CHAPTER 7 Thermal Managementu.dianyuan.com/bbs/u/22/1096741609.pdf · 2020. 5. 12. · Thermal Management Power Semiconductor Applications Philips Semiconductors Fig. 2 Maximum d.c

Thermal Management Power Semiconductor ApplicationsPhilips Semiconductors

CHAPTER 7

Thermal Management

7.1 Thermal Considerations

553


Thermal Considerations

555


7.1.1 Thermal Considerations for Power Semiconductors

The perfect power switch is not yet available. All powersemiconductors dissipate power internally both during theon-state and during the transition between the on and offstates. The amount of power dissipated internally generallyspeaking increases in line with the power being switchedby the semiconductor. The capability of a switch to operatein a particular circuit will therefore depend upon the amountof power dissipated internally and the rise in the operatingtemperature of the silicon junction that this powerdissipation causes. It is therefore important that circuitdesigners are familiar with the thermal characteristics ofpower semiconductors and are able to calculate powerdissipation limits and junction operating temperatures.

This chapter is divided into two parts. Part One describesthe essential thermal properties of semiconductors andexplains the concept of a limit in terms of continuous modeand pulse mode operation. Part Two gives workedexamples showing junction temperature calculations for avariety of applied power pulse waveforms.

PART ONE

The power dissipation limitThe maximum allowable power dissipation forms a limit tothe safe operating area of power transistors. Powerdissipation causes a rise in junction temperature which will,in turn, start chemical and metallurgical changes. The rateat which these changes proceed is exponentially related totemperature, and thus prolonged operation of a powertransistor above its junction temperature rating is liable toresult in reduced life. Operation of a device at, or below, itspower dissipation rating (together with carefulconsideration of thermal resistances associated with thedevice) ensures that the junction temperature rating is notexceeded.

All power semiconductors have a power dissipationlimitation. For rectifier products such as diodes, thyristorsand triacs, the power dissipation rating can be easilytranslated in terms of current ratings; in the on-state thevoltage drop is well defined. Transistors are, however,somewhat more complicated. A transistor, be it a powerMOSFET or a bipolar, can operate in its on-state at anyvoltage up to its maximum rating depending on the circuitconditions. It is therefore necessary to specify a SafeOperating Area (SOA) for transistors which specifies thepower dissipation limit in terms of a series of boundaries inthe current and voltage plane. These operating areas areusuallypresented for mounting base temperatures of 25 ˚C.At higher temperatures, operating conditions must bechecked to ensure that junction temperatures are notexceeding the desired operating level.

Continuous power dissipation

The total power dissipation in a semiconductor may becalculated from the product of the on-state voltage and theforward conduction current. The heat dissipated in thejunction of the device flows through the thermal resistancebetween the junction and the mounting base, Rthj-mb. Thethermal equivalent circuit of Fig. 1 illustrates this heat flow;Ptot can be regarded as a thermal current, and thetemperature difference between the junction and mountingbase ∆Tj-mb as a thermal voltage. By analogy with Ohm’slaw, it follows that:

Fig. 1 Heat transport in a transistor with powerdissipation constant with respect to time

Fig. 2 shows the dependence of the maximum powerdissipation on the temperature of the mounting base. Ptotmax

is limited either by a maximum temperature difference:

or by the maximum junction temperature Tjmax (Tmb K isusually 25˚C and is the value of Tmb above which themaximum power dissipation must be reduced to maintainthe operating point within the safe operating area).

In the first case, Tmb ≤ Tmb K :

that is, the power dissipation has a fixed limit value (Ptot max K

is the maximum d.c. power dissipation below Tmb K). If thetransistor is subjected to a mounting-base temperatureTmb 1, its junction temperature will be less than Tjmax by anamount (TmbK - Tmb 1), as shown by the broken line in Fig. 2.

Ptot =Tj − Tmb

Rthj − mb

1

∆Tj − mbmax = Tjmax − Tmb K 2

Ptot maxK =∆Tj − mbmax

Rthj − mb

; 3

557


Fig. 2 Maximum d.c. power dissipation in a transistoras a function of the mounting-base temperature

In the second case, Tmb > Tmb K :

that is, the power dissipation must be reduced as themounting base temperature increases along the slopingstraight line in Fig. 2. Equation 4 shows that the lower thethermal resistance Rthj-mb, the steeper is the slope of theline. In this case, Tmb is the maximum mounting-basetemperature that can occur in operation.

Example

The following data is provided for a particular transistor.

Ptot maxK = 75 W

Tjmax = 175 ˚C

Rthj-mb ≤ 2 K/W

Themaximumpermissible power dissipation for continuousoperation at a maximum mounting-base temperature ofTmb = 80 ˚C is required.

Note that the maximum value of Tmb is chosen to besignificantly higher than the maximumambient temperatureto prevent an excessively large heatsink being required.

From Eq. 4 we obtain:

Provided that the transistor is operated within SOA limits,this value is permissible since it is below Ptot max K. The sameresult can be obtained graphically from the Ptot max diagram(Fig. 3) for the relevant transistor.

Fig. 3 Example of the determination of maximum powerdissipation

Pulse power operationWhen a power transistor is subjected to a pulsed load,higher peak power dissipation is permitted. The materialsin a power transistor have a definite thermal capacity, andthus the critical junction temperature will not be reachedinstantaneously, even when excessive power is beingdissipated in the device. The power dissipation limit maybe extended for intermittent operation. The size of theextension will depend on the duration of the operationperiod (that is, pulse duration) and the frequency with whichoperation occurs (that is, duty factor).

Fig. 4 Heating of a transistor chip

If power isapplied to a transistor, the device will immediatelystart to warm up (Fig. 4). If the power dissipation continues,a balance will be struck between heat generation andremoval resulting in the stabilisation of Tj and ∆Tj-mb. Someheat energy will be stored by the thermal capacity of thedevice, and the stable conditions will be determined by thethermal resistances associated with the transistor and itsthermal environment. When the power dissipation ceases,the device will cool (the heating and cooling laws will beidentical, see Fig. 5). However, if the power dissipationceases before the temperature of the transistor stabilises,the peak values of Tj and ∆Tj-mb will be less than the values

0 20 40 60 80 100 120 140 160 180Tmb / C

Ptotmax / W100

90

80

70

60

50

40

30

20

10

0

47.5

Ptot max =Tjmax − Tmb

Rthj − mb

; 4

Ptot max =175−80

2W, =47.5W

558


reached for the same level of continuous power dissipation(Fig. 6). If the second pulse is identical to the first, the peaktemperature attained by the device at the end of the secondpulse will be greater than that at the end of the first pulse.Further pulses will build up the temperature until some newstable situation is attained (Fig. 7). The temperature of thedevice in this stable condition will fluctuate above andbelowthe mean. If the upward excursions extend into the regionof excessive Tj then the life expectancy of the device maybe reduced. This can happen with high-powerlow-duty-factor pulses, even though the average power isbelow the d.c. rating of the device.

Fig. 5 Heating and cooling follow the same law

Fig. 6 The peak temperature caused by a short powerpulse can be less than the steady-state temperature

resulting from the same power

Fig. 8 shows a typical safe operating area for d.c. operationof a power MOSFET. The corresponding rectangular-pulseoperating areas with a fixed duty factor, δ = 0, and the pulsetime tp as a parameter, are also shown. These boundariesrepresent the largest possible extension of the operatingarea for particular pulse times. When the pulse timebecomes very short, the power dissipation does not havea limiting action and the pulsecurrent and maximumvoltageform the only limits. This rectangle represents the largestpossible pulse operating area.

Fig. 7 A train of power pulses increases the averagetemperature if the device does not have time to cool

between pulses

Fig. 8 D.C. and rectangular pulse operating areas withfixed parameters δ=0, tp and Tmb=25˚C

In general, the shorter the pulse and the lower thefrequency, the lower the temperature that the junctionreaches. By analogy with Eq. 3, it follows that:

where Zthj-mb is the transient thermal impedance betweenthe junction and mounting base of the device. It dependson the pulse duration tp, and the duty factor δ, where:

1 100VDS / V

ID / A100

10

1

0.1

10 us

100 us

1 ms

10 ms

RDS(ON) =

VDS/ID

100 ms DC

tp =

BUK553-100

10

B

A

Ptot M =Tj −Tmb

Zthj − mb

, 5

559


and T is the pulse period. Fig. 9 shows a typical family ofcurves for thermal impedance against pulse duration, withduty factor as a parameter.

Fig. 9 Example of the presentation of the transientthermal impedance as a function of the pulse time with

duty factor as parameter

Again, the maximum pulse power dissipation is limitedeither by the maximum temperature difference ∆Tj-mb max

(Eq. 2), or by the maximum junction temperature Tjmax, andso by analogy with Eqs. 3 and 4:

when Tmb ≤ Tmb K, and:

when Tmb > Tmb K. That is, below a mounting-basetemperature of Tmb K, the maximum power dissipation hasa fixed limit value; and above Tmb K, the power dissipationmust be reduced linearly with increasing mounting-basetemperature.

Short pulse duration (Fig. 10a)As the pulse duration becomes very short, the fluctuationsof junction temperature become negligible, owing to theinternal thermal capacity of the transistor. Consequently,the only factor to be considered is the heating of the junctionby the average power dissipation; that is:

The transient thermal impedance becomes:

The Zthj-mb curves approach this value asymptotically as tpdecreases. Fig. 9 shows that, for duty factors in the range0.1 to 0.5, the limit values given by Eq. 10 have virtuallybeen reached at tp = 10-6 s.

Fig. 10 Three limit cases of rectangular pulse loads:(a) short pulse duration(b) long pulse duration(c) single-shot pulse

Long pulse duration (Fig. 10b)As the pulse duration increases, the junction temperatureapproaches a stationary value towards the end of a pulse.The transient thermal impedance tends to the thermalresistance for continuous power dissipation; that is:

Fig. 9 shows thatZthj-mb approaches this valueas tp becomeslarge. In general, transient thermal effects die out in mostpower transistors within 0.1 to 1.0 seconds. This timedepends on the material and construction of the case, thesize of the chip, the way it is mounted, and other factors.Power pulses with a duration in excess of this time haveapproximately the same effect as a continuous load.

δ =tp

T, 6

limtp →0

Zthj − mb= δRthj − mb 10

1E-07 1E-05 1E-03 1E-01 1E+01t / s

Zth j-mb / (K/W)1E+01

1E+00

1E-01

1E-02

1E-03

0

0.5

0.2

0.1

0.05

0.02

=tp tp

T

TP

t

D

=

BUK553-100A

Ptot maxK =∆Tj − mbmax

Zthj − mb

, 7

Ptot M max =Tjmax−Tmb

Zthj − mb

, 8

limtp → ∞

Zthj − mb=Rthj − mb 11

Ptot(av) = δPtot M 9

560


Single-shot pulses (Fig. 10c)As the duty factor becomes very small, the junction tendsto cool down completely between pulses so that each pulsecan be treated individually. When considering singlepulses, the Zthj-mb values for δ = 0 (Fig. 9) give sufficientlyaccurate results.

PART TWO

Calculating junction temperaturesMost applications which include power semiconductorsusually involve some form of pulse mode operation. Thissection gives several worked examples showing howjunction temperatures can be simply calculated. Examplesare given for a variety of waveforms:

(1) Periodic Waveforms

(2) Single Shot Waveforms

(3) Composite Waveforms

(4) A Pulse Burst

(5) Non Rectangular Pulses

From the point of view of reliability it is most important toknow what the peak junction temperature will be when thepower waveform is applied and also what the averagejunction temperature is going to be.

Peak junction temperature will usually occur at the end ofan applied pulse and its calculation will involve transientthermal impedance. The average junction temperature(where applicable) is calculated by working out the averagepower dissipation using the d.c. thermal resistance.

Fig. 11 Periodic Rectangular Pulse

When considering the junction temperature in a device, thefollowing formula is used:

where ∆Tj-mb is found from a rearrangement of equation 7.In all the following examples the mounting basetemperature (Tmb) is assumed to be 75˚C.

Periodic rectangular pulseFig. 11 shows an example of a periodic rectangular pulse.This type of pulse is commonly found in switchingapplications. 100W is dissipated every 400µs for a periodof 20µs, representing a duty cycle (δ) of 0.05. The peakjunction temperature is calculated as follows:

The value for Zth j-mb is taken from the δ=0.05 curve shownin Fig. 12 (This diagram repeats Fig. 9 but has beensimplified for clarity). The above calculation shows that thepeak junction temperature will be 85˚C.

Single shot rectangular pulseFig. 13 shows an example of a single shot rectangularpulse. The pulse used is the same as in the previousexample, which should highlight the differences betweenperiodic and single shot thermal calculations. For a singleshot pulse, the time period between pulses is infinity, ie theduty cycle δ=0. In this example 100W is dissipated for aperiod of 20µs. To work out the peak junction temperaturethe following steps are used:

The value for Zth j-mb is taken from the δ=0 curve shown inFig. 12. The above calculation shows that the peak junctiontemperature will be 4˚C above the mounting basetemperature.

Peak Tj: t = 2× 10−5s

P = 100W

δ =20400

= 0.05

Zthj − mb = 0.12K/W

∆Tj − mb = P × Zthj − mb = 100× 0.12= 12°C

Tj = Tmb + ∆Tj − mb = 75+ 12= 87°C

Average Tj: Pav = P × δ = 100× 0.05= 5W

∆Tj − mb(av) = Pav × Zthj − mb(δ = 1) = 5× 2 = 10°C

Tj (av) = Tmb + ∆Tj − mb(av) = 75+ 10= 85°C

0102030405060708090

100110

0 20 40 60 80 100 400 420 440 460 480

POWER(W)

TIME(uS)

0 20 40 60 80 100 400 420 440 460 480TIME(uS)

Tmb

Tjpeak

Tj t = 2× 10−5s

P = 100W

δ = 0

Zthj − mb = 0.04K/W

∆Tj − mb = P × Zthj − mb = 100× 0.04= 4°C

Tj = Tmb + ∆Tj − mb 14

561


Fig. 12 Thermal impedance curves for δ=0.05 and δ=0

Fig. 13 Single Shot Pulse

For a single shot pulse, the average power dissipated andaverage junction temperature are not relevant.

Composite rectangular pulseIn practice, a power device frequently has to handlecomposite waveforms, rather than the simple rectangularpulses shown so far. This type of signal can be simulatedby superimposing several rectangular pulses which have acommon period, but both positive and negative amplitudes,in addition to suitable values of tp and δ.

By way of an example, consider the composite waveformshown in Fig. 14. To show the way in which the methodused for periodic rectangular pulses is extended to covercomposite waveforms, the waveform shown has beenchosen to be an extension of the periodic rectangular pulseexample. The period is 400µs, and the waveform consistsof three rectangular pulses, namely 40W for 10µs, 20W for150µs and 100W for 20µs. The peak junction temperaturemay be calculated at any point in the cycle. To be able toadd the various effects of the pulses at this time, all thepulses, both positive and negative, must end at time tx inthe first calculation and ty in the second calculation. Positivepulses increase the junction temperature, while negativepulses decrease it.

Calculation for time t x

In equation 15, the values for P1, P2 and P3 are known:P1=40W, P2=20W and P3=100W. The Zth values are takenfrom Fig. 9. For each term in the equation, the equivalentduty cycle must be worked out. For instance the firstsuperimposed pulse in Fig. 14 lasts for a time t1 = 180µs,representing a duty cycle of 180/400 = 0.45 = δ. Thesevalues can then be used in conjunction with Fig. 9 to find avalue for Zth, which in this case is 0.9K/W. Table 1a givesthe values calculated for this example.

t1 t2 t3 t4

180µs 170µs 150µs 20µs

Repetitive δ 0.450 0.425 0.375 0.050T=400µs Zth 0.900 0.850 0.800 0.130

Single Shot δ 0.000 0.000 0.000 0.000T=∞ Zth 0.130 0.125 0.120 0.040

Table 1a. Composite pulse parameters for time tx

1E-07 1E-05 1E-03 1E-01 1E+01t / s

Zth j-mb / (K/W)1E+01

1E+00

1E-01

1E-02

1E-03

0

0.05

=tp tp

T

TP

t

D

=

0.04

0.12

0

10

20

30

40

50

60

70

80

90

100

110

0 20 40 60 80 100

POWER(W)

0 20 40 60 80 100Tmb

Tjpeak

Tj

∆Tj − mb@x = P1.Zthj − mb(t1) + P2.Zthj − mb(t3)

+ P3.Zthj − mb(t4) − P1.Zthj − mb(t2)

− P2.Zthj − mb(t4) 15

562


Fig. 14 Periodic Composite Waveform

0 20 40 60 80 100

0

20

40

60

80

100

200

180

160

140

120

100

80

60

40

20

0

20

40

60

120 140 160 180 200 220

P3

P2

P1

P1

P2

t1t2

t3t4

360 380 400 420 440 460 480 500

tx tyPOWER (W)

Time (uS)

160

140

120

100

80

60

40

20

0

20

40

60

80

100

t5t6

t7t8

120

P2

P3

P1

P2

P3

POWER (W)

POWER (W)Time (uS)

Time (uS)

Substituting these values into equation 15 for Tj-mb@x gives

Hence the peak values of Tj are 104.4˚C for the repetitivecase, and 80.9˚C for the single shot case.

Single Shot: ∆Tj − mb@x = 40× 0.13+ 20× 0.125

+ 100× 0.04− 40× 0.125

− 20× 0.04

= 5.9°C

Tj = Tmb + ∆Tj − mb = 75+ 5.9= 80.9°C

Repetitive: ∆Tj − mb@x = 40× 0.9+ 20× 0.85

+ 100× 0.13− 40× 0.85

− 20× 0.13

= 29.4°C

Tj = Tmb + ∆Tj − mb = 75+ 29.4= 104.4°C

563


Calculation for time t y

where Zthj-mb(t) is the transient thermal impedance for a pulsetime t.

t5 t6 t7 t8380µs 250µs 230µs 10µs

Repetitive δ 0.950 0.625 0.575 0.025T=400µs Zth 1.950 1.300 1.250 0.080

Single Shot δ 0.000 0.000 0.000 0.000T=∞ Zth 0.200 0.160 0.150 0.030

Table 1b. Composite pulse parameters for time ty

Substituting these values into equation 16 for Tj-mb@y gives

Hence the peak values of Tj are 96.2˚C for the repetitivecase, and 78˚C for the single shot case.

The average power dissipation and the average junctiontemperature can be calculated as follows:

Clearly, the junction temperature at time tx should be higherthan that at time ty, and this is proven in the abovecalculations.

Burst pulsesPower devices are frequently subjected to a burst of pulses.This type of signal can be treated as a composite waveformandas in the previous example simulated by superimposingseveral rectangular pulses which have a common period,but both positive and negative amplitudes, in addition tosuitable values of tp and δ.

Fig. 15 Burst Mode Waveform

Consider the waveform shown in Fig. 15. The period is240µs, and the burst consists of three rectangular pulsesof 100W power and 20µs duration, separated by 30µs. Thepeak junction temperaturewill occurat the endof each burstat time t = tx = 140µs. To be able to add the various effectsof the pulses at this time, all the pulses, both positive andnegative, must end at time tx. Positive pulses increase thejunction temperature, while negative pulses decrease it.

where Zthj-mb(t) is the transient thermal impedance for a pulsetime t.

The Zth values are taken from Fig. 9. For each term in theequation, the equivalent duty cycle must be worked out.These values can then be used in conjunction with Fig. 9to find a value for Zth. Table 2 gives the values calculatedfor this example.

t1 t2 t3 t4 t5

120µs 100µs 70µs 50µs 20µs

Repetitive δ 0.500 0.420 0.290 0.210 0.083T=240µs Zth 1.100 0.800 0.600 0.430 0.210

Single Shot δ 0.000 0.000 0.000 0.000 0.000T=∞ Zth 0.100 0.090 0.075 0.060 0.040

Table 2. Burst Mode pulse parameters

Substituting these values into equation 17 gives

∆Tj − mb@y = P2.Zthj − mb(t5) + P3.Zthj − mb(t6)

+ P1.Zthj − mb(t8) − P2.Zthj − mb(t6)

− P3.Zthj − mb(t7) 16

050

100150

350300250200150100

500

50100150200250300350

0 20 40 60 80 100 120 140 160 240 260 280 300

T=240usPOWER (W)

Time (us)

Time (us)

t4

t2

t1

t3

t5

Repetitive: ∆Tj − mb@y = 20× 1.95+ 100× 1.3

+ 40× 0.08− 20× 1.3

− 100× 1.25

= 21.2°C

Tj = Tmb + ∆Tj − mb = 75+ 21.2= 96.2°C

Single Shot: ∆Tj − mb@y = 20× 0.2+ 100× 0.16

+ 40× 0.03− 20× 0.16

− 100× 0.15

= 3°C

Tj = Tmb + ∆Tj − mb = 75+ 3 = 78°C

∆Tj − mb@x = P.Zthj − mb(t1) + P.Zthj − mb(t3)

+ P.Zthj − mb(t5) − P.Zthj − mb(t2)

− P.Zthj − mb(t4) 17

Pav =25× 10+ 5× 130+ 20× 100

400

= 7.25W

∆Tj − mb(av) = Pav × Zthj − mb(δ = 1) = 7.25× 2 = 14.5°C

Tj (av) = Tmb + ∆Tj − mb(av) = 75+ 14.5= 89.5°C

564


Hence the peak value of Tj is 143˚C for the repetitive caseand 81.5˚C for the single shot case. To calculate theaverage junction temperature Tj(av):

The above example for the repetitive waveform highlightsa case where the average junction temperature (125˚C) iswell within limits but the composite pulse calculation showsthe peak junction temperature to be significantly higher. Forreasons of improved long term reliability it is usual tooperate devices with a peak junction temperature below125˚C.

Non-rectangular pulsesSo far, the worked examples have only covered rectangularwaveforms. However, triangular, trapeziodal andsinusoidal waveforms are also common. In order to applythe above thermal calculations to non rectangularwaveforms, the waveform is approximated by a series ofrectangles. Each rectangle represents part of thewaveform. The equivalent rectangle must be equal in areato the section of the waveform it represents (ie the sameenergy)andalso be of the samepeak power.With referenceto Fig. 16, a triangular waveform has been approximatedto one rectangle in the first example, and two rectangles inthe second. Obviously, increasing the number of sectionsthe waveform is split into will improve the accuracy of thethermal calculations.

In the first example, there is only one rectanglular pulse ,of duration 50µs, dissipating 50W. So again using equation14 and a rearrangement of equation 7:

Fig. 16 Non Rectangular Waveform

When the waveform is split into two rectangular pulses:

For this example P1 = 25W, P2 = 25W, P3 = 50W. Table 3below shows the rest of the parameters:

t1 t2 t3

75µs 50µs 37.5µs

Single Shot D 0.000 0.000 0.000T=∞ Zth 0.085 0.065 0.055

10% Duty Cycle D 0.075 0.050 0.037T=1000µs Zth 0.210 0.140 0.120

50% Duty Cycle D 0.375 0.250 0.188T=200µs Zth 0.700 0.500 0.420

Table 3. Non Rectangular Pulse Calculations

Repetitive: ∆Tj − mb@x = 100× 1.10+ 100× 0.60

+ 100× 0.21− 100× 0.80

− 100× 0.43

= 68°C

Tj = 75+ 68= 143°C0 20 40 60 80 100

0

10

20

30

40

50

100

90

80

70

60

50

40

30

20

10

0

10

20

30

0 20 40 60 80 100

0

10

20

30

40

50

100

90

80

70

60

50

40

30

20

10

0

10

20

30

P3

P2

P1

t3

t2

t1

Single Shot: ∆Tj − mb@x = 100× 0.10+ 100× 0.075

+ 100× 0.04− 100× 0.09

− 100× 0.06

= 6.5°C

Tj = 75+ 6.5= 81.5°C

Pav =3× 100× 20

240

= 25W

∆Tj − mb(av) = Pav × Zthj − mb(δ = 1) = 25× 2 = 50°C

Tj (av) = 75+ 50= 125°C

∆Tj − mb = Ptot M × Zthj − mb

Single Shot ∆Tj − mb = 50× 0.065= 3.25°C

Tjpeak = 75+ 3.25= 78.5°C

10% Duty cycle ∆Tj − mb = 50× 0.230= 11.5°C

Tjpeak = 75+ 11.5= 86.5°C

50% Duty cycle ∆Tj − mb = 50× 1.000= 50°C

Tjpeak = 75+ 50= 125°C

∆Tj − mb = P3.Zthj − mb(t3) + P1.Zthj − mb(t1) − P2.Zthj − mb(t2) 18

565


Sustituting these values into equation 18 gives:

To calculate the average junction temperature:

Conclusion

A method has been presented to allow the calculation ofaverage and peak junction temperatures for a variety ofpulse types. Several worked examples have showncalculations for various common waveforms. The methodfor non rectangular pulses can be applied to any waveshape, allowing temperature calculations for waveformssuch as exponential and sinusoidal power pulses. Forpulses such as these, care must be taken to ensure thatthe calculation gives the peak junction temperature, as itmay not occur at the end of the pulse. In this instanceseveral calculations must be performed with differentendpoints to find the maximum junction temperature.

Single shot ∆Tj − mb = 50× 0.055+ 25× 0.085− 25× 0.065

= 3.25°C

Tjpeak = 75+ 3.25= 78.5°C

10% Duty cycle ∆Tj − mb = 50× 0.12+ 25× 0.21− 25× 0.14

= 7.75°C

Tjpeak = 75+ 7.75= 82.5°C

50% Duty cycle ∆Tj − mb = 50× 0.42+ 25× 0.7− 25× 0.5

= 26°C

Tjpeak = 75+ 26= 101°C

50% Duty Cycle Pav =50× 50

200

= 12.5W

∆Tj − mb(av) = Pav × Zthj − mb(δ = 1) = 12.5× 2 = 25°C

Tj (av) = 75+ 25= 100°C

10% Duty Cycle Pav =50× 501000

= 2.5W

∆Tj − mb(av) = Pav × Zthj − mb(δ = 1) = 2.5× 2 = 5°C

Tj (av) = 75+ 5 = 80°C

566


7.1.2 Heat Dissipation

All semiconductor failure mechanisms are temperaturedependent and so the lower the junction temperature, thehigher the reliability of the circuit. Thus our data specifiesa maximum junction temperature which should not beexceeded under the worst probable conditions. However,derating the operating temperature from Tjmax is alwaysdesirable to improve the reliability still further. The junctiontemperature depends on both the power dissipated in thedevice and the thermal resistances (or impedances)associated with the device. Thus careful consideration ofthese thermal resistances (or impedances) allows the userto calculate the maximum power dissipation that will keepthe junction temperature below a chosen value.

The formulae and diagrams given in this section can onlybe considered as a guide for determining the nature of aheatsink. This is because the thermal resistance of aheatsink depends on numerous parameters which cannotbe predetermined. They include the position of thetransistor on the heatsink, the extent to which air can flowunhindered, the ratio of the lengths of the sides of theheatsink, the screening effect of nearby components, andheating from these components. It is always advisable tocheck important temperatures in the finished equipmentunder the worst probable operating conditions. The morecomplex the heat dissipation conditions, the more importantit becomes to carry out such checks.

Heat flow pathThe heat generated in a semiconductor chip flows byvarious paths to the surroundings. Small signal devices donot usually require heatsinking; the heat flows from thejunction to the mounting base which is in close contact withthe case. Heat is then lost by the case to the surroundingsby convection and radiation (Fig. 1a). Power transistors,however, are usually mounted on heatsinks because of thehigher power dissipation they experience. Heat flows fromthe transistor case to the heatsink by way of contactpressure, and the heatsink loses heat to the surroundingsby convection and radiation, or by conduction to coolingwater (Fig. 1b). Generally air cooling is used so that theambient referred to in Fig.1 is usually the surrounding air.Note that if this is the air inside an equipment case, theadditional thermal resistance between the inside andoutsideof the equipment caseshould be taken into account.

Contact thermal resistance R th mb-h

The thermal resistance between the transistor mountingbase and the heatsink depends on the quality and size ofthe contact areas, the type of any intermediate plates used,and the contact pressure. Care should be taken whendrilling holes in heatsinks to avoid burring and distorting the

metal, and both mating surfaces should be clean. Paintfinishes of normal thickness, up to 50 um (as a protectionagainst electrolytic voltage corrosion), barely affect thethermal resistance. Transistor case and heatsink surfacescan never be perfectly flat, and so contact will take placeon several points only, with a small air-gap over the rest ofthe area. The use of a soft substance to fill this gap lowersthe contact thermal resistance. Normally, the gap is filledwith a heatsinking compound which remains fairly viscousat normal transistor operating temperatures and has a highthermal conductivity. The use of such a compound alsoprevents moisture from penetrating between the contactsurfaces. Proprietary heatsinking compounds are availablewhich consist of a silicone grease loaded with someelectrically insulating good thermally conducting powdersuch as alumina. The contact thermal resistance Rth mb-h isusually small with respect to (Rth j-mb + Rth h-amb) when coolingis by natural convection. However, the heatsink thermalresistance Rth h-amb can be very small when either forcedventilation or water cooling are used, and thus a closethermal contact between the transistor case and heatsinkbecomes particularly important.

Fig. 1 Thermal resistances in the heat flow process:(a) Without a heatsink

(b) With a heatsink

Thermal resistance calculationsFig. 1a shows that, when a heatsink is not used, the totalthermal resistance between junction and ambient is givenby:

However, power transistors are generally mounted on aheatsink since Rth j-amb is not usually small enough tomaintain temperatures within the chip below desired levels.

Fig. 1b shows that, when a heatsink is used, the totalthermal resistance is given by:

Rthj − amb = Rthj − mb + Rthmb− amb 1

Rthj − amb = Rthj − mb + Rthmb− h + Rthh − amb 2

567


Note that the direct heat loss from the transistor case to thesurroundings through Rth mb-amb is negligibly small.

The first stage in determining the size and nature of therequired heatsink is to calculate the maximum heatsinkthermal resistance Rth h-amb that will maintain the junctiontemperature below the desired value

Continuous operationUnder dc conditions, the maximum heatsink thermalresistance can be calculated directly from the maximumdesired junction temperature.

Combining equations 2 and 3 gives:

and substituting Eq 4 into Eq 5 gives:

The values of Rth j-mb and Rth mb-h are given in the publisheddata. Thus, either Eq. 5 or Eq.6 can be used to find themaximum heatsink thermal resistance.

Intermittent operationThe thermal equivalent circuits of Fig. 1 are inappropriatefor intermittent operation, and the thermal impedance Zth j-mb

should be considered.

The mounting-base temperature has always beenassumed to remain constant under intermittent operation.This assumption is known to be valid in practice providedthat the pulse time is less than about one second. Themounting-base temperature does not change significantlyunder these conditions as indicated in Fig. 2. This isbecause heatsinks have a high thermal capacity and thusa high thermal time-constant.

Thus Eq.6 is valid for intermittent operation, provided thatthe pulse time is less than one second. The value of Tmbcan be calculated from Eq. 7, and the heatsink thermalresistance can be obtained from Eq.6.

Fig. 2 Variation of junction and mounting basetemperature when the pulse time is small compared

with the thermal time constant of the heatsink

The thermal time constant of a transistor is defined as thattime at which the junction temperature has reached 70%of its final value after being subjected to a constant powerdissipation at a constant mounting base temperature.

Now, if the pulse duration tp exceeds one second, thetransistor is temporarily in thermal equilibrium since sucha pulse duration is significantly greater than the thermaltime-constant of most transistors. Consequently, for pulsetimes of more than one second, the temperature differenceTj - Tmb reaches a stationary final value (Fig. 3) and Eq.7should be replaced by:

In addition, it is no longer valid to assume that the mountingbase temperature is constant since the pulse time is alsono longer small with respect to the thermal time constantof the heatsink.

Fig. 3 Variation of junction and mounting basetemperature when the pulse time is not small compared

with the thermal time constant of the heatsink

Rthj − amb =Tj − Tamb

Ptot(av)3

and Rthj − mb =Tj − Tmb

Ptot(av)4

Rthh − amb =Tj − Tamb

Ptot(av)− Rthj − mb − Rthmb− h 5

Rthh − amb =Tmb − Tamb

Ptot(av)− Rthmb− h 6

Tmb = Tj − PtotM.Rthj − mb 8

PtotM =Tj − Tmb

Zth j − mb

thus: Tmb = Tj − PtotM.Zth j − mb 7

568


Smaller heatsinks for intermittentoperationIn many instances, the thermal capacity of a heatsink canbe utilised to design a smaller heatsink for intermittentoperation than would be necessary for the same level ofcontinuous power dissipation. The average powerdissipation in Eq. 6 is replaced by the peak powerdissipation to obtain the value of the thermal impedancebetween the heatsink and the surroundings

The value of Zth h-amb will be less than the comparablethermal resistance and thus a smaller heatsink can bedesigned than that obtained using the too large valuecalculated from Eq.6.

HeatsinksThree varieties of heatsink are in common use: flat plates(including chassis), diecast finned heatsinks, and extrudedfinned heatsinks. The material normally used for heatsinkconstruction is aluminium although copper may be usedwith advantage for flat-sheet heatsinks. Small finned clipsaresometimes used to improve the dissipationof low-powertransistors.

Heatsink finishHeatsink thermal resistance is a function of surface finish.A painted surface will have a greater emissivity than a brightunpainted one. The effect is most marked with flat plateheatsinks, where about one third of the heat is dissipatedby radiation. The colour of the paint used is relativelyunimportant, and the thermal resistance of a flat plateheatsink painted gloss white will be only about 3% higherthan that of the same heatsink painted matt black. Withfinned heatsinks, painting is less effective since heatradiated from most fins will fall on adjacent fins but it is stillworthwhile. Both anodising and etching will decrease thethermal resistivity. Metallic type paints, such as aluminiumpaint, have the lowest emissivities, although they areapproximately ten times better than a bright aluminiummetal finish.

Flat-plate heatsinksThe simplest type of heatsink is a flat metal plate to whichthe transistor is attached. Such heatsinks are used both inthe form of separate plates and as the equipment chassisitself. The thermal resistance obtained depends on thethickness, area and orientation of the plate, as well as onthe finish and power dissipated. A plate mountedhorizontally will have about twice the thermal resistance ofa vertically mounted plate. This is particularly importantwhere the equipment chassis itself is used as the heatsink.

In Fig. 4, the thermal resistance of a blackened heatsink isplotted against surface area (one side) with powerdissipation as a parameter. The graph is accurate to within25% for nearly square plates, where the ratio of the lengthsof the sides is less than 1.25:1.

Finned heatsinks

Finned heatsinks may be made by stacking flat plates,although it is usually more economical to use ready madediecast or extruded heatsinks. Since most commerciallyavailable finned heatsinks are of reasonably optimumdesign, it is possible to compare them on the basis of theoverallvolume whichthey occupy. Thiscomparison is madein Fig. 5 for heatsinks with their fins mounted vertically;again, the graph is accurate to 25%.

Fig. 4 Generalised heatsink characteristics: flat verticalblack aluminium plates, 3mm thick, approximately

square

Fig. 5 Generalised heatsink characteristic: blackenedaluminium finned heatsinks

Zthh − amb =Tmb − Tamb

PtotM

− Rthmb− h 9

569


Fig. 6 Heatsink nomogram

1

10

100

10

10

10

3

4

5

10 100 1000

Bright HorizontalBright Vertical

Blackened HorizontalBlackened Vertical

1W2W5W10W20W50W100W

1mm

2mm3mm

30D

40DEXTRUDED

FLAT PLATE

SOT93TO220SOT82

Length of Extruded Heatsink (mm)

Areaofonesidemm2

Heatsink dimensionsThe maximum thermal resistance through which sufficientpower can be dissipated without damaging the transistorcan be calculated as discussed previously. This sectionexplains how to arrive at a type and size of heatsink thatgives a sufficiently low thermal resistance.

Natural air coolingThe required size of aluminium heatsinks - whether flat orextruded (finned) can be derived from the nomogram inFig. 6. Like all heatsink diagrams, the nomogram does notgive exact values for Rth h-amb as a function of the dimensionssince the practical conditions always deviate to some extentfrom those under which the nomogram was drawn up. Theactual values for the heatsink thermal resistance may differby up to 10% from the nomogram values. Consequently, itis advisable to take temperature measurements in thefinished equipment, particularly where the thermalconditions are critical.

The conditions to which the nomogram applies are asfollows:

• natural air cooling (unimpeded natural convection with nobuild up of heat);

• ambient temperature about 25˚C, measured about 50mmbelow the lower edge of the heatsink (see Fig. 7);

• atmospheric pressure about 10 N/m2;

• single mounting (that is, not affected by nearby heatsinks);

• distance between the bottom of the heatsink and the baseof a draught-free space about 100mm (see Fig. 7);

• transistor mounted roughly in the centre of the heatsink(this is not so important for finned heatsinks because ofthe good thermal conduction).

The appropriately-sized heatsink is found as follows.

1. Enter the nomogram from the right hand side of section1 at the appropriate Rth h-amb value (see Fig. 8). Movehorizontally to the left, until the appropriate curve fororientation and surface finish is reached.

2. Move vertically upwards to intersect the appropriatepower dissipation curve in section 2.

570


3. Move horizontally to the left into section 3 for the desiredthickness of a flat-plate heatsink, or the type of extrusion.

4. If an extruded heatsink is required, move verticallyupwards to obtain its length (Figs. 9a and 9b give theoutlines of the extrusions).

5. If a flat-plate heatsink is to be used, move verticallydownwards to intersect the appropriate curve forenvelope type in section 4.

6. Move horizontally to the left to obtain heatsink area.

7. The heatsink dimensions should not exceed the ratio of1.25:1.

Fig. 7 Conditions applicable to nomogram in Fig. 6

Fig. 8 Use of the heatsink nomogram

Fig. 9a Outline of Extrusion 30D

Fig. 9b Outline of Extrusion 40D

Thecurves in section 2 take account of the non linear natureof the relationship between the temperature drop acrossthe heatsink and the power dissipation loss. Thus, at aconstant value of the heatsink thermal resistance, thegreater the power dissipation, the smaller is the requiredsize of heatsink. This is illustrated by the following example.

ExampleAn extruded heatsink mounted vertically and with a paintedsurface is required to have a maximum thermal resistanceof Rth h-amb = 2.6 ˚C/W at the following powers:

Enter the nomogram at the appropriate value of the thermalresistance in section 1, and via either the 50W or 5W linein section 2, the appropriate lengths of the extrudedheatsink 30D are found to be:

Case (b) requires a shorter length since the temperaturedifference is ten times greater than in case (a).

As the ambient temperature increases beyond 25˚C, sodoes the temperature of the heatsink and thus the thermalresistance (at constant power) decreases owing to theincreasing role of radiation in the heat removal process.Consequently, a heatsink with dimensions derived fromFig. 6 at Tamb > 25˚C will be more than adequate. If themaximum ambient temperature is less than 25˚C, then thethermal resistance will increase slightly. However, any

Approx

100mm

Approx

50mm

Tamb Tamb

Th

(a)Ptot(av) = 5W (b)Ptot(av) = 50W

(a) length = 110mm and (b) length = 44mm.

571


increase will lie within the limits of accuracy of thenomogram and within the limits set by other uncertaintiesassociated with heatsink calculations.

For heatsinks with relatively small areas, a considerablepart of the heat is dissipated from the transistor case. Thisis why the curves in section 4 tend to flatten out withdecreasing heatsink area. The area of extruded heatsinksis always large with respect to the surface of the transistorcase, even when the length is small.

Fig. 10 Arrangement of two equally loaded transistorsmounted on a common heatsink

If several transistors are mounted on a common heatsink,each transistor should be associated with a particularsection of the heatsink (either an area or length accordingto type) whose maximum thermal resistance is calculatedfrom equations 5 or 6; that is, without taking the heatproduced by nearby transistors into account. From the sum

of these areas or lengths, the size of the common heatsinkcan then be obtained. If a flat heatsink is used, thetransistors are best arranged as shown in Fig. 10. Themaximum mounting base temperatures of transistors insuch a grouping should always be checked once theequipment has been constructed.

Forced air coolingIf the thermal resistance needs to be much less than 1˚C/W,or the heatsink not too large, forced air cooling by meansof fans can be provided. Apart from the size of the heatsink,the thermal resistance now only depends on the speed ofthe cooling air. Provided that the cooling air flows parallelto the fins and with sufficient speed (>0.5m/s), the thermalresistance hardly depends on the power dissipation and theorientation of the heatsink. Note that turbulence in the aircurrent can result in practical values deviating fromtheoretical values.

Fig. 11 shows the form in which the thermal resistances forforced air cooling are given in the case of extrudedheatsinks. It also shows the reduction in thermal resistanceor length of heatsink which may be obtained with forced aircooling.

The effect of forced air cooling in the case of flat heatsinksis seen from Fig. 12. Here, too, the dissipated power andthe orientation of the heatsink have only a slight effect onthe thermal resistance, provided that the air flow issufficiently fast.

Fig. 11 Thermal Resistance of a finned heatsink (type 40D) as a function of the length with natural and forced aircooling

0 50 100 150 200 250 300 3500

0.5

1

1.5

2

2.5

Length (mm)

Rth h-amb (K/W)

P=3W

P=10W

P=30W

P=100W

1m/s2m/s5m/s

Natural

Convection

ForcedCooling

(Vertical)

Blackened

572


Fig. 12 Thermal Resistances of heatsinks (2mm thick copper or 3mm thick aluminium) under natural convection andforced cooling conditions, with a SOT93 envelope.

(a) blackened(b) bright

SummaryThe majority of power transistors require heatsinking, andonce the maximum thermal resistance that will maintain thedevice’s junction temperature below its rating has beencalculated, a heatsink of appropriate type and size can bechosen. The practical conditions under which a transistorwill be operated are likely to differ from the theoretical

considerations used to determine the required heatsink,and thus temperatures should always be checked in thefinished equipment. Finally, some applications require asmall heatsink, or one with a very low thermal resistance,in which case forced air cooling by means of fans shouldbe provided.

573

Preface Power Semiconductor ApplicationsPhilips Semiconductors

Acknowledgments

We are grateful for all the contributions from our colleagues within Philips and to the Application Laboratories in Eindhovenand Hamburg.

We would also like to thank Dr.P.H.Mellor of the University of Sheffield for contributing the application note of section 3.1.5.

The authors thank Mrs.R.Hayes for her considerable help in the preparation of this book.

The authors also thank Mr.D.F.Haslam for his assistance in the formatting and printing of the manuscripts.

Contributing Authors

N.Bennett

M.Bennion

D.Brown

C.Buethker

L.Burley

G.M.Fry

R.P.Gant

J.Gilliam

D.Grant

N.J.Ham

C.J.Hammerton

D.J.Harper

W.Hettersheid

J.v.d.Hooff

J.Houldsworth

M.J.Humphreys

P.H.Mellor

R.Miller

H.Misdom

P.Moody

S.A.Mulder

E.B.G. Nijhof

J.Oosterling

N.Pichowicz

W.B.Rosink

D.C. de Ruiter

D.Sharples

H.Simons

T.Stork

D.Tebb

H.Verhees

F.A.Woodworth

T.van de Wouw

This book was originally prepared by the Power Semiconductor Applications Laboratory, of the Philips Semiconductorsproduct division, Hazel Grove:

M.J.Humphreys

C.J.Hammerton

D.Brown

R.Miller

L.Burley

It was revised and updated, in 1994, by:

N.J.Ham C.J.Hammerton D.Sharples

Preface Power Semiconductor ApplicationsPhilips Semiconductors

Preface

This book was prepared by the Power Semiconductor Applications Laboratory of the Philips Semiconductors productdivision, Hazel Grove. The book is intended as a guide to using power semiconductors both efficiently and reliably in powerconversion applications. It is made up of eight main chapters each of which contains a number of application notes aimedat making it easier to select and use power semiconductors.

CHAPTER 1 forms an introduction to power semiconductors concentrating particularly on the two major power transistortechnologies, Power MOSFETs and High Voltage Bipolar Transistors.

CHAPTER 2 is devoted to Switched Mode Power Supplies. It begins with a basic description of the most commonly usedtopologies and discusses the major issues surrounding the use of power semiconductors including rectifiers. Specificdesign examples are given as well as a look at designing the magnetic components. The end of this chapter describesresonant power supply technology.

CHAPTER 3 describes motion control in terms of ac, dc and stepper motor operation and control. This chapter looks onlyat transistor controls, phase control using thyristors and triacs is discussed separately in chapter 6.

CHAPTER 4 looks at television and monitor applications. A description of the operation of horizontal deflection circuits isgiven followed by transistor selection guides for both deflection and power supply applications. Deflection and power supplycircuitexamples arealso given basedon circuitsdesigned by the Product Concept andApplication Laboratories (Eindhoven).

CHAPTER 5 concentrates on automotive electronics looking in detail at the requirements for the electronic switches takinginto consideration the harsh environment in which they must operate.

CHAPTER 6 reviews thyristor and triac applications from the basics of device technology and operation to the simple designrules which should be followed to achieve maximum reliability. Specific examples are given in this chapter for a numberof the common applications.

CHAPTER 7 looks at the thermal considerations for power semiconductors in terms of power dissipation and junctiontemperature limits. Part of this chapter is devoted to worked examples showing how junction temperatures can be calculatedto ensure the limits are not exceeded. Heatsink requirements and designs are also discussed in the second half of thischapter.

CHAPTER 8 is an introduction to the use of high voltage bipolar transistors in electronic lighting ballasts. Many of thepossible topologies are described.

Contents Power Semiconductor ApplicationsPhilips Semiconductors

Table of Contents

CHAPTER 1 Introduction to Power Semiconductors 1

General 3

1.1.1 An Introduction To Power Devices ............................................................ 5

Power MOSFET 17

1.2.1 PowerMOS Introduction ............................................................................. 19

1.2.2 Understanding Power MOSFET Switching Behaviour ............................... 29

1.2.3 Power MOSFET Drive Circuits .................................................................. 39

1.2.4 Parallel Operation of Power MOSFETs ..................................................... 49

1.2.5 Series Operation of Power MOSFETs ....................................................... 53

1.2.6 Logic Level FETS ...................................................................................... 57

1.2.7 Avalanche Ruggedness ............................................................................. 61

1.2.8 Electrostatic Discharge (ESD) Considerations .......................................... 67

1.2.9 Understanding the Data Sheet: PowerMOS .............................................. 69

High Voltage Bipolar Transistor 77

1.3.1 Introduction To High Voltage Bipolar Transistors ...................................... 79

1.3.2 Effects of Base Drive on Switching Times ................................................. 83

1.3.3 Using High Voltage Bipolar Transistors ..................................................... 91

1.3.4 Understanding The Data Sheet: High Voltage Transistors ....................... 97

CHAPTER 2 Switched Mode Power Supplies 103

Using Power Semiconductors in Switched Mode Topologies 105

2.1.1 An Introduction to Switched Mode Power Supply Topologies ................... 107

2.1.2 The Power Supply Designer’s Guide to High Voltage Transistors ............ 129

2.1.3 Base Circuit Design for High Voltage Bipolar Transistors in PowerConverters ........................................................................................................... 141

2.1.4 Isolated Power Semiconductors for High Frequency Power SupplyApplications ......................................................................................................... 153

Output Rectification 159

2.2.1 Fast Recovery Epitaxial Diodes for use in High Frequency Rectification 161

2.2.2 Schottky Diodes from Philips Semiconductors .......................................... 173

2.2.3 An Introduction to Synchronous Rectifier Circuits using PowerMOSTransistors ........................................................................................................... 179

i


Design Examples 185

2.3.1 Mains Input 100 W Forward Converter SMPS: MOSFET and BipolarTransistor Solutions featuring ETD Cores ........................................................... 187

2.3.2 Flexible, Low Cost, Self-Oscillating Power Supply using an ETD34Two-Part Coil Former and 3C85 Ferrite .............................................................. 199

Magnetics Design 205

2.4.1 Improved Ferrite Materials and Core Outlines for High Frequency PowerSupplies ............................................................................................................... 207

Resonant Power Supplies 217

2.5.1. An Introduction To Resonant Power Supplies .......................................... 219

2.5.2. Resonant Power Supply Converters - The Solution For Mains PollutionProblems .............................................................................................................. 225

CHAPTER 3 Motor Control 241

AC Motor Control 243

3.1.1 Noiseless A.C. Motor Control: Introduction to a 20 kHz System ............... 245

3.1.2 The Effect of a MOSFET’s Peak to Average Current Rating on InvertorEfficiency ............................................................................................................. 251

3.1.3 MOSFETs and FREDFETs for Motor Drive Equipment ............................. 253

3.1.4 A Designers Guide to PowerMOS Devices for Motor Control ................... 259

3.1.5 A 300V, 40A High Frequency Inverter Pole Using Paralleled FREDFETModules ............................................................................................................... 273

DC Motor Control 283

3.2.1 Chopper circuits for DC motor control ....................................................... 285

3.2.2 A switched-mode controller for DC motors ................................................ 293

3.2.3 Brushless DC Motor Systems .................................................................... 301

Stepper Motor Control 307

3.3.1 Stepper Motor Control ............................................................................... 309

CHAPTER 4 Televisions and Monitors 317

Power Devices in TV & Monitor Applications (including selectionguides) 319

4.1.1 An Introduction to Horizontal Deflection .................................................... 321

4.1.2 The BU25XXA/D Range of Deflection Transistors .................................... 331ii


4.1.3 Philips HVT’s for TV & Monitor Applications .............................................. 339

4.1.4 TV and Monitor Damper Diodes ................................................................ 345

TV Deflection Circuit Examples 349

4.2.1 Application Information for the 16 kHz Black Line Picture Tubes .............. 351

4.2.2 32 kHz / 100 Hz Deflection Circuits for the 66FS Black Line Picture Tube 361

SMPS Circuit Examples 377

4.3.1 A 70W Full Performance TV SMPS Using The TDA8380 ......................... 379

4.3.2 A Synchronous 200W SMPS for 16 and 32 kHz TV .................................. 389

Monitor Deflection Circuit Example 397

4.4.1 A Versatile 30 - 64 kHz Autosync Monitor ................................................. 399

CHAPTER 5 Automotive Power Electronics 421

Automotive Motor Control (including selection guides) 423

5.1.1 Automotive Motor Control With Philips MOSFETS .................................... 425

Automotive Lamp Control (including selection guides) 433

5.2.1 Automotive Lamp Control With Philips MOSFETS .................................... 435

The TOPFET 443

5.3.1 An Introduction to the 3 pin TOPFET ......................................................... 445

5.3.2 An Introduction to the 5 pin TOPFET ......................................................... 447

5.3.3 BUK101-50DL - a Microcontroller compatible TOPFET ............................ 449

5.3.4 Protection with 5 pin TOPFETs ................................................................. 451

5.3.5 Driving TOPFETs ....................................................................................... 453

5.3.6 High Side PWM Lamp Dimmer using TOPFET ......................................... 455

5.3.7 Linear Control with TOPFET ...................................................................... 457

5.3.8 PWM Control with TOPFET ....................................................................... 459

5.3.9 Isolated Drive for TOPFET ........................................................................ 461

5.3.10 3 pin and 5 pin TOPFET Leadforms ........................................................ 463

5.3.11 TOPFET Input Voltage ............................................................................ 465

5.3.12 Negative Input and TOPFET ................................................................... 467

5.3.13 Switching Inductive Loads with TOPFET ................................................. 469

5.3.14 Driving DC Motors with TOPFET ............................................................. 471

5.3.15 An Introduction to the High Side TOPFET ............................................... 473

5.3.16 High Side Linear Drive with TOPFET ...................................................... 475iii


Automotive Ignition 477

5.4.1 An Introduction to Electronic Automotive Ignition ...................................... 479

5.4.2 IGBTs for Automotive Ignition .................................................................... 481

5.4.3 Electronic Switches for Automotive Ignition ............................................... 483

CHAPTER 6 Power Control with Thyristors and Triacs 485

Using Thyristors and Triacs 487

6.1.1 Introduction to Thyristors and Triacs ......................................................... 489

6.1.2 Using Thyristors and Triacs ....................................................................... 497

6.1.3 The Peak Current Handling Capability of Thyristors .................................. 505

6.1.4 Understanding Thyristor and Triac Data .................................................... 509

Thyristor and Triac Applications 521

6.2.1 Triac Control of DC Inductive Loads .......................................................... 523

6.2.2 Domestic Power Control with Triacs and Thyristors .................................. 527

6.2.3 Design of a Time Proportional Temperature Controller ............................. 537

Hi-Com Triacs 547

6.3.1 Understanding Hi-Com Triacs ................................................................... 549

6.3.2 Using Hi-Com Triacs .................................................................................. 551

CHAPTER 7 Thermal Management 553

Thermal Considerations 555

7.1.1 Thermal Considerations for Power Semiconductors ................................. 557

7.1.2 Heat Dissipation ......................................................................................... 567

CHAPTER 8 Lighting 575

Fluorescent Lamp Control 577

8.1.1 Efficient Fluorescent Lighting using Electronic Ballasts ............................. 579

8.1.2 Electronic Ballasts - Philips Transistor Selection Guide ............................ 587

8.1.3 An Electronic Ballast - Base Drive Optimisation ........................................ 589

iv

Index Power Semiconductor ApplicationsPhilips Semiconductors

Index

Airgap, transformer core, 111, 113Anti saturation diode, 590Asynchronous, 497Automotive

fanssee motor control

IGBT, 481, 483ignition, 479, 481, 483lamps, 435, 455motor control, 425, 457, 459, 471, 475resistive loads, 442reverse battery, 452, 473, 479screen heater, 442seat heater, 442solenoids, 469TOPFET, 473

Avalanche, 61Avalanche breakdown

thyristor, 490Avalanche multiplication, 134

Baker clamp, 138, 187, 190Ballast

electronic, 580fluorescent lamp, 579switchstart, 579

Base drive, 136base inductor, 147base inductor, diode assisted, 148base resistor, 146drive transformer, 145drive transformer leakage inductance, 149electronic ballast, 589forward converter, 187power converters, 141speed-up capacitor, 143

Base inductor, 144, 147Base inductor, diode assisted, 148Boost converter, 109

continuous mode, 109discontinuous mode, 109output ripple, 109

Bootstrap, 303Breakback voltage

diac, 492Breakdown voltage, 70Breakover current

diac, 492Breakover voltage

diac, 492, 592thyristor, 490

Bridge circuitssee Motor Control - AC

Brushless motor, 301, 303Buck-boost converter, 110Buck converter, 108 - 109Burst firing, 537Burst pulses, 564

Capacitancejunction, 29

Capacitormains dropper, 544

CENELEC, 537Charge carriers, 133

triac commutation, 549Choke

fluorescent lamp, 580Choppers, 285Clamp diode, 117Clamp winding, 113Commutation

diode, 164Hi-Com triac, 551thyristor, 492triac, 494, 523, 529

Compact fluorescent lamp, 585Continuous mode

see Switched Mode Power SuppliesContinuous operation, 557Converter (dc-dc)

switched mode power supply, 107Cookers, 537Cooling

forced, 572natural, 570

Crest factor, 529Critical electric field, 134Cross regulation, 114, 117Current fed resonant inverter, 589Current Mode Control, 120Current tail, 138, 143

Damper Diodes, 345, 367forward recovery, 328, 348losses, 347outlines, 345picture distortion, 328, 348selection guide, 345

Darlington, 13Data Sheets

High Voltage Bipolar Transistor, 92,97,331MOSFET, 69

i


dc-dc converter, 119Depletion region, 133Desaturation networks, 86

Baker clamp, 91, 138dI/dt

triac, 531Diac, 492, 500, 527, 530, 591Diode, 6

double diffused, 162epitaxial, 161schottky, 173structure, 161

Diode Modulator, 327, 367Disc drives, 302Discontinuous mode

see Switched Mode Power SuppliesDomestic Appliances, 527Dropper

capacitive, 544resistive, 544, 545

Duty cycle, 561

EFD coresee magnetics

Efficiency Diodessee Damper Diodes

Electric drill, 531Electronic ballast, 580

base drive optimisation, 589current fed half bridge, 584, 587, 589current fed push pull, 583, 587flyback, 582transistor selection guide, 587voltage fed half bridge, 584, 588voltage fed push pull, 583, 587

EMC, 260, 455see RFI, ESDTOPFET, 473

Emitter shortingtriac, 549

Epitaxial diode, 161characteristics, 163dI/dt, 164forward recovery, 168lifetime control, 162operating frequency, 165passivation, 162reverse leakage, 169reverse recovery, 162, 164reverse recovery softness, 167selection guide, 171snap-off, 167softness factor, 167stored charge, 162technology, 162

ESD, 67see Protection, ESDprecautions, 67

ETD coresee magnetics

F-packsee isolated package

Fall time, 143, 144Fast Recovery Epitaxial Diode (FRED)

see epitaxial diodeFBSOA, 134Ferrites

see magneticsFlicker

fluorescent lamp, 580Fluorescent lamp, 579

colour rendering, 579colour temperature, 579efficacy, 579, 580triphosphor, 579

Flyback converter, 110, 111, 113advantages, 114clamp winding, 113continuous mode, 114coupled inductor, 113cross regulation, 114diodes, 115disadvantages, 114discontinuous mode, 114electronic ballast, 582leakage inductance, 113magnetics, 213operation, 113rectifier circuit, 180self oscillating power supply, 199synchronous rectifier, 156, 181transformer core airgap, 111, 113transistors, 115

Flyback converter (two transistor), 111, 114Food mixer, 531Forward converter, 111, 116

advantages, 116clamp diode, 117conduction loss, 197continuous mode, 116core loss, 116core saturation, 117cross regulation, 117diodes, 118disadvantages, 117duty ratio, 117ferrite cores, 116magnetics, 213magnetisation energy, 116, 117

ii


operation, 116output diodes, 117output ripple, 116rectifier circuit, 180reset winding, 117switched mode power supply, 187switching frequency, 195switching losses, 196synchronous rectifier, 157, 181transistors, 118

Forward converter (two transistor), 111, 117Forward recovery, 168FREDFET, 250, 253, 305

bridge circuit, 255charge, 254diode, 254drive, 262loss, 256reverse recovery, 254

FREDFETsmotor control, 259

Full bridge converter, 111, 125advantages, 125diodes, 126disadvantages, 125operation, 125transistors, 126

Gatetriac, 538

Gate driveforward converter, 195

Gold doping, 162, 169GTO, 11Guard ring

schottky diode, 174

Half bridge, 253Half bridge circuits

see also Motor Control - ACHalf bridge converter, 111, 122

advantages, 122clamp diodes, 122cross conduction, 122diodes, 124disadvantages, 122electronic ballast, 584, 587, 589flux symmetry, 122magnetics, 214operation, 122synchronous rectifier, 157transistor voltage, 122transistors, 124voltage doubling, 122

Heat dissipation, 567

Heat sink compound, 567Heater controller, 544Heaters, 537Heatsink, 569Heatsink compound, 514Hi-Com triac, 519, 549, 551

commutation, 551dIcom/dt, 552gate trigger current, 552inductive load control, 551

High side switchMOSFET, 44, 436TOPFET, 430, 473

High Voltage Bipolar Transistor, 8, 79, 91,141, 341

‘bathtub’ curves, 333avalanche breakdown, 131avalanche multiplication, 134Baker clamp, 91, 138base-emitter breakdown, 144base drive, 83, 92, 96, 136, 336, 385base drive circuit, 145base inductor, 138, 144, 147base inductor, diode assisted, 148base resistor, 146breakdown voltage, 79, 86, 92carrier concentration, 151carrier injection, 150conductivity modulation, 135, 150critical electric field, 134current crowding, 135, 136current limiting values, 132current tail, 138, 143current tails, 86, 91d-type, 346data sheet, 92, 97, 331depletion region, 133desaturation, 86, 88, 91device construction, 79dI/dt, 139drive transformer, 145drive transformer leakage inductance, 149dV/dt, 139electric field, 133electronic ballast, 581, 585, 587, 589Fact Sheets, 334fall time, 86, 99, 143, 144FBSOA, 92, 99, 134hard turn-off, 86horizontal deflection, 321, 331, 341leakage current, 98limiting values, 97losses, 92, 333, 342Miller capacitance, 139operation, 150

iii


optimum drive, 88outlines, 332, 346over current, 92, 98over voltage, 92, 97overdrive, 85, 88, 137, 138passivation, 131power limiting value, 132process technology, 80ratings, 97RBSOA, 93, 99, 135, 138, 139RC network, 148reverse recovery, 143, 151safe operating area, 99, 134saturation, 150saturation current, 79, 98, 341secondary breakdown, 92, 133smooth turn-off, 86SMPS, 94, 339, 383snubber, 139space charge, 133speed-up capacitor, 143storage time, 86, 91, 92, 99, 138, 144, 342sub emitter resistance, 135switching, 80, 83, 86, 91, 98, 342technology, 129, 149thermal breakdown, 134thermal runaway, 152turn-off, 91, 92, 138, 142, 146, 151turn-on, 91, 136, 141, 149, 150underdrive, 85, 88voltage limiting values, 130

Horizontal Deflection, 321, 367base drive, 336control ic, 401d-type transistors, 346damper diodes, 345, 367diode modulator, 327, 347, 352, 367drive circuit, 352, 365, 406east-west correction, 325, 352, 367line output transformer, 354linearity correction, 323operating cycle, 321, 332, 347s-correction, 323, 352, 404TDA2595, 364, 368TDA4851, 400TDA8433, 363, 369test circuit, 321transistors, 331, 341, 408waveforms, 322

IGBT, 11, 305automotive, 481, 483clamped, 482, 484ignition, 481, 483

Ignitionautomotive, 479, 481, 483darlington, 483

Induction heating, 53Induction motor

see Motor Control - ACInductive load

see SolenoidInrush current, 528, 530Intrinsic silicon, 133Inverter, 260, 273

see motor control accurrent fed, 52, 53switched mode power supply, 107

Irons, electric, 537Isolated package, 154

stray capacitance, 154, 155thermal resistance, 154

Isolation, 153

J-FET, 9Junction temperature, 470, 557, 561

burst pulses, 564non-rectangular pulse, 565rectangular pulse, composite, 562rectangular pulse, periodic, 561rectangular pulse, single shot, 561

Lamp dimmer, 530Lamps, 435

dI/dt, 438inrush current, 438MOSFET, 435PWM control, 455switch rate, 438TOPFET, 455

Latching currentthyristor, 490

Leakage inductance, 113, 200, 523Lifetime control, 162Lighting

fluorescent, 579phase control, 530

Logic Level FETmotor control, 432

Logic level MOSFET, 436

Magnetics, 207100W 100kHz forward converter, 197100W 50kHz forward converter, 19150W flyback converter, 199core losses, 208core materials, 207EFD core, 210ETD core, 199, 207

iv


flyback converter, 213forward converter, 213half bridge converter, 214power density, 211push-pull converter, 213switched mode power supply, 187switching frequency, 215transformer construction, 215

Mains Flicker, 537Mains pollution, 225

pre-converter, 225Mains transient, 544Mesa glass, 162Metal Oxide Varistor (MOV), 503Miller capacitance, 139Modelling, 236, 265MOS Controlled Thyristor, 13MOSFET, 9, 19, 153, 253

bootstrap, 303breakdown voltage, 22, 70capacitance, 30, 57, 72, 155, 156capacitances, 24characteristics, 23, 70 - 72charge, 32, 57data sheet, 69dI/dt, 36diode, 253drive, 262, 264drive circuit loss, 156driving, 39, 250dV/dt, 36, 39, 264ESD, 67gate-source protection, 264gate charge, 195gate drive, 195gate resistor, 156high side, 436high side drive, 44inductive load, 62lamps, 435leakage current, 71linear mode, parallelling, 52logic level, 37, 57, 305loss, 26, 34maximum current, 69motor control, 259, 429modelling, 265on-resistance, 21, 71package inductance, 49, 73parallel operation, 26, 47, 49, 265parasitic oscillations, 51peak current rating, 251Resonant supply, 53reverse diode, 73ruggedness, 61, 73

safe operating area, 25, 74series operation, 53SMPS, 339, 384solenoid, 62structure, 19switching, 24, 29, 58, 73, 194, 262switching loss, 196synchronous rectifier, 179thermal impedance, 74thermal resistance, 70threshold voltage, 21, 70transconductance, 57, 72turn-off, 34, 36turn-on, 32, 34, 35, 155, 256

Motor, universalback EMF, 531starting, 528

Motor Control - AC, 245, 273anti-parallel diode, 253antiparallel diode, 250carrier frequency, 245control, 248current rating, 262dc link, 249diode, 261diode recovery, 250duty ratio, 246efficiency, 262EMC, 260filter, 250FREDFET, 250, 259, 276gate drives, 249half bridge, 245inverter, 250, 260, 273line voltage, 262loss, 267MOSFET, 259Parallel MOSFETs, 276peak current, 251phase voltage, 262power factor, 262pulse width modulation, 245, 260ripple, 246short circuit, 251signal isolation, 250snubber, 276speed control, 248switching frequency, 246three phase bridge, 246underlap, 248

Motor Control - DC, 285, 293, 425braking, 285, 299brushless, 301control, 290, 295, 303current rating, 288

v


drive, 303duty cycle, 286efficiency, 293FREDFET, 287freewheel diode, 286full bridge, 287half bridge, 287high side switch, 429IGBT, 305inrush, 430inverter, 302linear, 457, 475logic level FET, 432loss, 288MOSFET, 287, 429motor current, 295overload, 430permanent magnet, 293, 301permanent magnet motor, 285PWM, 286, 293, 459, 471servo, 298short circuit, 431stall, 431TOPFET, 430, 457, 459, 475topologies, 286torque, 285, 294triac, 525voltage rating, 288

Motor Control - Stepper, 309bipolar, 310chopper, 314drive, 313hybrid, 312permanent magnet, 309reluctance, 311step angle, 309unipolar, 310

Mounting, transistor, 154Mounting base temperature, 557Mounting torque, 514

Parasitic oscillation, 149Passivation, 131, 162PCB Design, 368, 419Phase angle, 500Phase control, 546

thyristors and triacs, 498triac, 523

Phase voltagesee motor control - ac

Power dissipation, 557see High Voltage Bipolar Transistor loss,MOSFET loss

Power factor correction, 580active, boost converted, 581

Power MOSFETsee MOSFET

Proportional control, 537Protection

ESD, 446, 448, 482overvoltage, 446, 448, 469reverse battery, 452, 473, 479short circuit, 251, 446, 448temperature, 446, 447, 471TOPFET, 445, 447, 451

Pulse operation, 558Pulse Width Modulation (PWM), 108Push-pull converter, 111, 119

advantages, 119clamp diodes, 119cross conduction, 119current mode control, 120diodes, 121disadvantages, 119duty ratio, 119electronic ballast, 582, 587flux symmetry, 119, 120magnetics, 213multiple outputs, 119operation, 119output filter, 119output ripple, 119rectifier circuit, 180switching frequency, 119transformer, 119transistor voltage, 119transistors, 121

Qs (stored charge), 162

RBSOA, 93, 99, 135, 138, 139Rectification, synchronous, 179Reset winding, 117Resistor

mains dropper, 544, 545Resonant power supply, 219, 225

modelling, 236MOSFET, 52, 53pre-converter, 225

Reverse leakage, 169Reverse recovery, 143, 162RFI, 154, 158, 167, 393, 396, 497, 529, 530,537Ruggedness

MOSFET, 62, 73schottky diode, 173

Safe Operating Area (SOA), 25, 74, 134, 557forward biased, 92, 99, 134reverse biased, 93, 99, 135, 138, 139

vi


Saturable choketriac, 523

Schottky diode, 173bulk leakage, 174edge leakage, 174guard ring, 174reverse leakage, 174ruggedness, 173selection guide, 176technology, 173

SCRsee Thyristor

Secondary breakdown, 133Selection Guides

BU25XXA, 331BU25XXD, 331damper diodes, 345EPI diodes, 171horizontal deflection, 343MOSFETs driving heaters, 442MOSFETs driving lamps, 441MOSFETs driving motors, 426Schottky diodes, 176SMPS, 339

Self Oscillating Power Supply (SOPS)50W microcomputer flyback converter, 199ETD transformer, 199

Servo, 298Single ended push-pull

see half bridge converterSnap-off, 167Snubber, 93, 139, 495, 502, 523, 529, 549

active, 279Softness factor, 167Solenoid

TOPFET, 469, 473turn off, 469, 473

Solid state relay, 501SOT186, 154SOT186A, 154SOT199, 154Space charge, 133Speed-up capacitor, 143Speed control

thyristor, 531triac, 527

Starterfluorescent lamp, 580

Startup circuitelectronic ballast, 591self oscillating power supply, 201

Static Induction Thyristor, 11Stepdown converter, 109Stepper motor, 309Stepup converter, 109

Storage time, 144Stored charge, 162Suppression

mains transient, 544Switched Mode Power Supply (SMPS)

see also self oscillating power supply100W 100kHz MOSFET forward converter,192100W 500kHz half bridge converter, 153100W 50kHz bipolar forward converter, 18716 & 32 kHz TV, 389asymmetrical, 111, 113base circuit design, 149boost converter, 109buck-boost converter, 110buck converter, 108ceramic output filter, 153continuous mode, 109, 379control ic, 391control loop, 108core excitation, 113core loss, 167current mode control, 120dc-dc converter, 119diode loss, 166diode reverse recovery effects, 166diode reverse recovery softness, 167diodes, 115, 118, 121, 124, 126discontinuous mode, 109, 379epitaxial diodes, 112, 161flux swing, 111flyback converter, 92, 111, 113, 123forward converter, 111, 116, 379full bridge converter, 111, 125half bridge converter, 111, 122high voltage bipolar transistor, 94, 112, 115,118, 121, 124, 126, 129, 339, 383, 392isolated, 113isolated packages, 153isolation, 108, 111magnetics design, 191, 197magnetisation energy, 113mains filter, 380mains input, 390MOSFET, 112, 153, 33, 384multiple output, 111, 156non-isolated, 108opto-coupler, 392output rectifiers, 163parasitic oscillation, 149power-down, 136power-up, 136, 137, 139power MOSFET, 153, 339, 384pulse width modulation, 108push-pull converter, 111, 119

vii


RBSOA failure, 139rectification, 381, 392rectification efficiency, 163rectifier selection, 112regulation, 108reliability, 139resonant

see resonant power supplyRFI, 154, 158, 167schottky diode, 112, 154, 173snubber, 93, 139, 383soft start, 138standby, 382standby supply, 392start-up, 391stepdown, 109stepup, 109symmetrical, 111, 119, 122synchronisation, 382synchronous rectification, 156, 179TDA8380, 381, 391topologies, 107topology output powers, 111transformer, 111transformer saturation, 138transformers, 391transistor current limiting value, 112transistor mounting, 154transistor selection, 112transistor turn-off, 138transistor turn-on, 136transistor voltage limiting value, 112transistors, 115, 118, 121, 124, 126turns ratio, 111TV & Monitors, 339, 379, 399two transistor flyback, 111, 114two transistor forward, 111, 117

Switching loss, 230Synchronous, 497Synchronous rectification, 156, 179

self driven, 181transformer driven, 180

Temperature control, 537Thermal

continuous operation, 557, 568intermittent operation, 568non-rectangular pulse, 565pulse operation, 558rectangular pulse, composite, 562rectangular pulse, periodic, 561rectangular pulse, single shot, 561single shot operation, 561

Thermal capacity, 558, 568

Thermal characteristicspower semiconductors, 557

Thermal impedance, 74, 568Thermal resistance, 70, 154, 557Thermal time constant, 568Thyristor, 10, 497, 509

’two transistor’ model, 490applications, 527asynchronous control, 497avalanche breakdown, 490breakover voltage, 490, 509cascading, 501commutation, 492control, 497current rating, 511dI/dt, 490dIf/dt, 491dV/dt, 490energy handling, 505external commutation, 493full wave control, 499fusing I2t, 503, 512gate cathode resistor, 500gate circuits, 500gate current, 490gate power, 492gate requirements, 492gate specifications, 512gate triggering, 490half wave control, 499holding current, 490, 509inductive loads, 500inrush current, 503latching current, 490, 509leakage current, 490load line, 492mounting, 514operation, 490overcurrent, 503peak current, 505phase angle, 500phase control, 498, 527pulsed gate, 500resistive loads, 498resonant circuit, 493reverse characteristic, 489reverse recovery, 493RFI, 497self commutation, 493series choke, 502snubber, 502speed controller, 531static switching, 497structure, 489switching, 489

viii


switching characteristics, 517synchronous control, 497temperature rating, 512thermal specifications, 512time proportional control, 497transient protection, 502trigger angle, 500turn-off time, 494turn-on, 490, 509turn-on dI/dt, 502varistor, 503voltage rating, 510

Thyristor data, 509Time proportional control, 537TOPFET

3 pin, 445, 449, 4615 pin, 447, 451, 457, 459, 463driving, 449, 453, 461, 465, 467, 475high side, 473, 475lamps, 455leadforms, 463linear control, 451, 457motor control, 430, 457, 459negative input, 456, 465, 467protection, 445, 447, 451, 469, 473PWM control, 451, 455, 459solenoids, 469

Transformertriac controlled, 523

Transformer core airgap, 111, 113Transformers

see magneticsTransient thermal impedance, 559Transient thermal response, 154Triac, 497, 510, 518

400Hz operation, 489, 518applications, 527, 537asynchronous control, 497breakover voltage, 510charge carriers, 549commutating dI/dt, 494commutating dV/dt, 494commutation, 494, 518, 523, 529, 549control, 497dc inductive load, 523dc motor control, 525dI/dt, 531, 549dIcom/dt, 523dV/dt, 523, 549emitter shorting, 549full wave control, 499fusing I2t, 503, 512gate cathode resistor, 500gate circuits, 500gate current, 491

gate requirements, 492gate resistor, 540, 545gate sensitivity, 491gate triggering, 538holding current, 491, 510Hi-Com, 549, 551inductive loads, 500inrush current, 503isolated trigger, 501latching current, 491, 510operation, 491overcurrent, 503phase angle, 500phase control, 498, 527, 546protection, 544pulse triggering, 492pulsed gate, 500quadrants, 491, 510resistive loads, 498RFI, 497saturable choke, 523series choke, 502snubber, 495, 502, 523, 529, 549speed controller, 527static switching, 497structure, 489switching, 489synchronous control, 497transformer load, 523transient protection, 502trigger angle, 492, 500triggering, 550turn-on dI/dt, 502varistor, 503zero crossing, 537

Trigger angle, 500TV & Monitors

16 kHz black line, 35130-64 kHz autosync, 39932 kHz black line, 361damper diodes, 345, 367diode modulator, 327, 367EHT, 352 - 354, 368, 409, 410high voltage bipolar transistor, 339, 341horizontal deflection, 341picture distortion, 348power MOSFET, 339SMPS, 339, 354, 379, 389, 399vertical deflection, 358, 364, 402

Two transistor flyback converter, 111, 114Two transistor forward converter, 111, 117

Universal motorback EMF, 531

ix


starting, 528

Vacuum cleaner, 527Varistor, 503Vertical Deflection, 358, 364, 402Voltage doubling, 122

Water heaters, 537

Zero crossing, 537Zero voltage switching, 537

x

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CHAPTER 7 Thermal Managementu.dianyuan.com/bbs/u/22/1096741609.pdf · 2020. 5. 12. · Thermal Management Power Semiconductor Applications Philips Semiconductors Fig. 2 Maximum d.c