JD Module2 V1 - University of Florida · Module 2 Diode LTSPICE Model! • Add 1N4004 diode model to LTSPICE diode model library! – Navigate to C:\Program Files\LTC\LTspiceIV\lib\cmp!

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EEL 3923C JD/ Module 2 Power Supply Design & Construction

Prof. T. Nishida��Fall 2010

2 EEL 3923C, Fall 2010, T. Nishida

II. General Power Supply •  Converts ac powerline voltage into DC voltage of

required magnitude and stability for the electronic system

Diode Rectifier Filter Voltage

Regulator

120 V(rms) 60 Hz ac line input

Ref: Section 3.5, Sedra and Smith, Microelectronic Circuits, 5th Ed., Oxford, 2004.


General Power Supply Design •  Useful reference on power supply design

Ref: http://www.st.com/stonline/books/pdf/docs/1707.pdf


II.1 Transformer •  Ideal loss-less transformer

– No dissipation

– Voltage step-up/down determined ratio of coil turns on secondary/primary

– Current has inverse ratio

–  Impedance transformation Ref: http://www.mpdigest.com/issue/Articles/2009/oct/Mini/Default.asp


Real Transformer •  Real transformer

– Series resistance in windings, Rs, Rp – Stray leakage inductance, Xs, Xp – Core losses

•  Eddy current, Rc •  Magnetization, Xm


Module 2 Transformer Specs •  EI30 series laminated transformer

Ref: http://ww2.pulseeng.com/products/datasheets/LT2010.pdf


LT SPICE Transformer Model

Ref: h'p://ltspice.linear.com/so5ware/scad3.pdf


Module 2 Transformer LTSPICE Model •  8:1 transformer with series resistance •  Output voltage depends on load current

File: Module2_Transformer_+_RL.asc


Module 2 Transformer Implementation •  Sealed case, switch, LED power indicator, and

fuse for safety (supplied in JD lab)


II.2 Diode Rectifier •  Purpose: Convert ac transformer output

into waveform with non-zero DC component

•  What is DC component?


P/N Junction Rectifier Diode •  I-V characteristics

•  Equivalent circuit

i

v

Reverse bias Forward bias


General Purpose Rectifier Diodes •  Module 2 diode

Ref: http://www.fairchildsemi.com/ds/1N%2F1N4001.pdf


Module 2 Diode LTSPICE Model •  Add 1N4004 diode model to LTSPICE diode model library

–  Navigate to C:\Program Files\LTC\LTspiceIV\lib\cmp –  Open standard.dio using notepad or by double-clicking and using LTSPICE –  Insert the following into the file

.MODEL 1N4004 D(IS = 3.699E-09 RS = 1.756E-02 N = 1.774 XTI = 3.0 EG = 1.110 CJO = 1.732E-11 M = 0.3353 VJ = 0.3905 FC = 0.5 ISR = 6.665E-10 NR = 2.103 BV = 400 IBV = 1.0E-03 Iave=1000m Vpk=400 mfg=Fairchild type=silicon)

–  Close and restart LTSPICE •  Insert a generic diode into your schematic •  Right-click the diode; you should see a dialog box

–  Click ‘Pick New Diode’ –  Select 1N4004 from the list of possible diodes –  The diode should now look like:

Ref: http://www.fairchildsemi.com/models/PSPICE/Discrete/Diode.html


Half Wave Rectifier •  Circuit (LTSPICE)


Half Wave Rectifier •  Equivalent circuit using constant voltage model

•  Effect of forward voltage drop

•  Peak inverse voltage


Full Wave Rectifier •  Disadvantages of half-bridge rectifier: maximum conduction angle

of 180º •  Possible fixes:

•  Use two half-bridge rectifiers (basic concept of center-tapped transformer approach)

•  Bridge rectifier (similar to Wheatstone bridge circuit)


Full Wave Rectifier •  Center-tapped transformer approach

Ref. Sedra & Smith, Fig. 3.26

vS(t), vO(t)

t

Note: Effect of VD drop.

PIV=2VS-VD

Where are the half-bridge rectifiers?


Full Wave Rectifier •  Bridge rectifier approach

vS(t), vO(t)

t

Ref. Sedra & Smith, Fig. 3.27

PIV=VS-VD

What is the voltage drop?

(a)   Positive half-cycle

Which diodes are forward-biased?

(b) Negative half-cycle


Module 2 Full Wave Rectifier •  Note the importance of the ground reference


II.3 Filter •  Purpose: Reduce voltage ripple

•  Need shunt capacitor to pass DC and filter ac frequencies


Half Wave Rectifier With Filter Cap •  Goal: First order

smoothing of output •  Approach: Filter

capacitor •  Assume capacitor

initially uncharged, vC(t=0)=0V

•  Assume ideal diode for simplicity (i.e. neglect VD drop)

vS(t), vO(t)

t

T Vr


Half Wave Rectifier With Filter Cap •  Approximate Analysis C charges up from t=0 to t=T/4 iD=iC+iL

where iL=vO/R and iC=Cdvs/dt

Diode turns off at peak. Why? vO(t=T/4) =VSpeak C discharges through R delivering load

current.

vO=VSpeake-t/RC Stops discharging when vO(t) less than vs

(t).

vO(t)

t vS (t)


Half Wave Rectifier With Filter Cap •  Approximate Analysis

Define ripple voltage, Vr: VSpeak-Vr ≅VSpeake-T/R

LC

Assuming CR>>T,

Vr ≅ VSpeak(T/RLC) Vr ≅VO (T/C)(IL/VO) 0.05VO ≅ IL T/C

•  Similar analysis for full wave rectifier with filter capacitor •  What changes?

vS(t), vO(t)

t

T Vr


Capacitors Types Capacitor types Capacitance range Accuracy

Temperature stability

Leakage Comments

ElectrolyHc 0.1 µF -‐ ~1 F V poor V poor Poor Polarised capacitor -‐ widely used in power supplies for smoothing, and bypass where accuracy, etc is not required.

Ceramic 10 pF -‐ 1 µF Variable Variable Average Exact performance of capacitor depends to a large extent on the ceramic used.

Tantalum 0.1 µF -‐ 500 µF Poor Poor Poor Polarised capacitor -‐ very high capacitance density.

Silver mica 1 pF -‐ 3000 pF Good Good Good Rather expensive and large -‐ not widely used these days except when small value accurate capacitors are needed.

Polyester (Mylar)

0.001 µF -‐ 50 µF Good Poor Good Inexpensive, and popular for non-‐demanding applica@ons.

Polystyrene 10 pF -‐ 1 µF V good Good V good High quality, oBen used in filters and the like where accuracy is needed.

Polycarbonate 100 pF -‐ 20 µF V good V good Good Used in many high tolerance and hash environmental condi@ons. Supply now restricted.

Polypropylene 100pF -‐ 50 µF V good Good V good High performance and low dielectric absorp@on.

Teflon 100 pF -‐ 1 µF V good V v good V v good High performance -‐ lowest dielectric absorp@on.

Glass 10 pF -‐ 1000 pF Good Good V good Excellent for very harsh environments while offering good stability. Very expensive.

Porcelain 100 pF -‐ 0.1 µF Good Good Good Good long term stability

Vacuum and air 1 pF -‐ 10 000 pF OBen used as variable capacitors in transmiKers as a result of their very high voltage capability.

Ref: h'p://www.radio-‐electronics.com/info/data/capacitor/capacitor_types.php


Capacitor Applications ApplicaHon Suitable types Reasons

Power supply smoothing Aluminium electrolyHc High capacity, high ripple current

Audio frequency coupling

Aluminium electrolyHc

Tantalum

Polyester / polycarbonate

High capacitance

High capacitance, small size

Cheap, but values not as high as electrolyHcs

RF coupling

Ceramic COG

Ceramic X7R

Polystyrene

Small, cheap, low loss

Small cheap, but higher loss than COG

Very low loss, but larger than ceramic

RF decoupling

Ceramic COG

Ceramic X7R

Small, low loss. Values limited to around 1000 pF

Small, low loss, higher values available than for COG types

Tuned circuits Silver mica

Ceramic COG

Close tolerance, low loss

Close tolerance, low loss, although not as good as silver mica

Ref: h'p://www.radio-‐electronics.com/info/data/capacitor/capacitor_types.php


Module 2 LTSPICE Simulation Half Wave with Filter Cap

•  Caution: Make sure + terminal of electrolytic capacitor is connected to positive secondary voltage lead

•  Select standard value capacitance by right-clicking capacitor



•  Note: Need to simulate long enough to reach steady-state – Start to save data after steady-state is reached



•  Note: Positive current defined down in RL •  Calculate percent ripple in output voltage

– Percent ripple = 100(Vr /VOmax )


Module 2 LTSPICE Simulation Full Wave with Filter Cap

•  Caution: Make sure + terminal of electrolytic capacitor is connected to positive secondary voltage lead


II.4 Regulator •  Purpose: Active circuit to achieve nearly

constant output voltage up to a max load current

•  Approaches – Open-circuit

•  Zener diode – Closed-circuit

•  Op-amp, transistor •  Specialized regulator ICs


Operation at Reverse Breakdown—��Zener Diodes

•  Operation at reverse bias •  Define VZ and IZ with opposite polarity

•  Circuit symbol

•  I-V characteristic

i

v -VZ -VZK

-IZK

-IZT

Figure 3.21, Sedra & Smith


Zener Diodes •  Parameters: Identify on I-V characteristic

•  Q point (i=IZT and v=VZ) •  Zz= incremental resistance (slope = 1/Zz) •  ΔV=Zz Δ I •  IZK = minimum reverse current for operation in breakdown

region •  Equivalent circuit (piece-wise linear)

•  VZ = VZ0 + ZzIZ for IZ > IZK

+ VZ _


Zener Shunt Regulator •  Zener diode placed in parallel with load (shunt)



Zener Shunt Regulator •  Line regulation: Defined as change in output voltage, VO

for change in line voltage, V+, for no load •  ΔVO=(rz/(rz+R)) ΔV+

•  What is the effect of connecting a load? •  Load regulation: Defined as ΔVo per 1mA when RL

chosen to draw IL=1mA •  If ΔIL=+1mA, what is ΔIZ? •  Effect of ΔIZ on ΔVO? Check zener I-V curve. •  ΔVO = Zz ΔIZ

•  What limits the lowest RL for the shunt regulator?


1N4728A – 1N4758A Zener Diodes

Ref: http://www.fairchildsemi.com/ds/1N%2F1N4745A.pdf


Module 2 Zener Diode LTSPICE Model •  Add 1N4733A zener diode model to LTSPICE diode model library

–  Navigate to C:\Program Files\LTC\LTspiceIV\lib\cmp –  Open standard.dio using notepad or by double-clicking and using LTSPICE –  Insert the following into the file

* 1N4733 * Motorola 5.1V 1W Si Zener pkg:DO-41 1,2 .MODEL 1N4733 D(IS=7.03E-16 RS=0.871 TT=5.01E-8 CJO=1.89E-10 VJ=0.75 M=0.33

BV=5.059 IBV=0.049 Vpk=5.1 mfg=Fairchild type=zener)

–  Close and restart LTSPICE •  Insert a generic diode into your schematic •  Right-click the diode; you should see a dialog box

–  Click ‘Pick New Diode’ –  Select 1N4733 zener diode from the list of possible diodes –  The zener diode should now look like:

Ref: http://www.duncanamps.com/spice/diodes/zener.mod


Module 2 Zener LTSPICE Model •  Zener diode placed in parallel with load (shunt)



LM2940 Low Dropout Pos Regulator

Ref: http://www.national.com/ds/LM/LM2940.pdf


LM2940 Low Dropout Pos Regulator



LT1086 Low Dropout Pos Regulator

Ref: h'p://cds.linear.com/docs/Datasheet/1086ffs.pdf


LT1086 Low Dropout Pos Regulator

Ref: h'p://cds.linear.com/docs/Datasheet/1086ffs.pdf


LM2940 Standard Pos Regulator

Ref: http://www.fairchildsemi.com/ds/LM/LM7805.pdf


LM3940 Regulator 5V to 3.3V Converter


Documents

JD Module2 V1 - University of Florida · Module 2 Diode LTSPICE Model! • Add 1N4004 diode model to LTSPICE diode model library! – Navigate to C:\Program Files\LTC\LTspiceIV\lib\cmp!