A High Efficiency Full-bridge Converter

* Corresponding author: Joy Iong-Zong Chen, 168 University Rd. Dasung 51505 Chunghua, Department of Electrical Engineering Dayeh University, Taiwan ROC, E-mail: [email protected] Copyright JES 2012 on-line : journals/esrgroups.org/jes

Joy Iong-Zong Chen J. Electrical Systems 8-4 (2012): 442-458

Regular paper

A High Efficiency Full-bridge Converter

JES

Journal of Electrical Systems

A high efficiency full-bridge converter is implemented with a ZVS (zero voltage switching) full-bridge converter developed by Intersil IC (integrated circuit), 6754ISL , in this paper. For the comparaison purpose the data results from measuring the other one that implemented by IC

3895UCC converter is also presented. Normally, the implementation of a ZVS full-bridge converter is mainly for supplying the power to telecommunication system operating in BS (base station) resources, file server machines, or/and industrial applications. In addition, for a power supply system a Z0VS converter is mostly either applied in the rear stage controller to arrive at the null voltage switching or in the later stage to use as a control transistor to obtain the synchronization. In the contribution a fact was validated by this implementation that the efficiency of over 96% without unnecessary loss caused in the conversion procedure can be reached, as the IC 6754ISL is taken to serve as ZVS full-bridge converter and synchronization filter. Moreover, this investigated and implemented converter can obtain over 96% power efficiency in conversion procedure when compared with that of 90% which were ever published by the conventional techniques. Apart from, a L-C resonance circuit was developed and embedded into the popular PWM (pulse width modulation) power converter, which is referred as the soft-switching, so as to down sizing the volume of the IC which can totally reduce the power losses caused in the duration of a semi-conductor switching.

Keywords : Full-bridge converter, PWM (pulse width modulation), Synchronization filter, ZVS (Zero voltage switching).

1. Introduction

The related industrial of green energy is expected able to solve the problems of environmental pollution, to save power, and to play an alternative energy. For the reason of saving the energy to require much higher efficiency in power generating is becoming an important issue. It is known that the hardware switching technique has become as soft-switching technique in the design of power supply system. On the other hand, the power transfer techniques of the former one, which is by using of PWM (pulse width modulation) technique, transmits to the scheme with switching method for the latter one [1-4]. Thus, the efficiency in generating energy for a power supply system should be improved definitely. On the basis of aforementioned concept a high efficiency (96%) full-bridge converter is designed and implemented with soft-switching technique which is referred as ZVS (zero voltage switching) full-bridge converter. Furthermore, in this paper a high efficiency full-bridge converter is not only completed with IC (integrated circuit) 6754ISL , but its system performance also compared to one that completed with 3895UCC is.

Recently, the technique of IC is developed so fast as to the cost down quickly. By the way, the related products of the IC become much diversity. Therefore, in order to satisfy huge of the IC specifications and/or power assumption which could be ranged from the lowest value 1.5V up to the highest above 380V. Traditionally, a power supply with linear specification has the characters of lower power density, larger volume, and achieving the

J. Electrical Systems 8-4 (2012): 442-458

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increasing and decreasing voltage at the output terminal by using of PWM scheme to handle with the conducting time of power transistors. Especially, there will exists the parasitic capacitance and/or parasitic inductance inside the transistor when it is acting as a power switch, that is, the voltage and current happen at the terminal of an power transistor are not null at the switching instant. Thus, this fact will cause a huge of switching losses. Even that the more switching frequencies, the more power amount in switching losses will be. Certainly, it is gradually replaced with high frequency switching power supply in order to promote full efficiency in power generating and cost effective [5-11]. Moreover, the L-C resonance circuit is usually took into account the work for the reasons described as follows: to down size the full volume of the new style of power supply system, to reduce the power losses in switching interval with semiconductor components, and to increase the efficiency during power conversion. The resonance circuit illustrated previously is also referred as soft switching technique [22, 23] which includes phase-controlled and forearm modulation all can be obtained by ZVS and ZCS (zero current switching) results [16-18]. However, the power losses generated except in the switching interval, there is still another one so-called transmission power losses which is usually incurred from the losses of the resistor or/and the semiconductor components appear during the power conversion. The former one power loss can be solved by the means described previously, i.e., ZVS or ZCS. The advance techniques presented in this paper are used to mitigate the transmission power losses and the line winding loses which is caused at the secondary side of a high frequency transformer and a post-stage rectifier diode during the conversion interval. On the other hand, there are large amounts of transmission power losses will be generated due to both the semiconductors characteristics and the forward voltage happens at the power-on duration. Hence, these transmission power losses are equivalent to the production of forward voltage and forward current. One who can make sense that the transmission power losses occupy most of the part of all the power losses when the conversion is processing, since the increase of the loading current occurred at the output when some of the rectifier diodes are applied. Therefore, it is known that the transmission power losses are playing a key parameter which deteriorates the efficiency of a power supply circuit [19-21].

However, such post stage transmission power losses aforementioned may be removed by replacing with a synchronization rectifier embedded in a circuit [5-11]. This mean is not only able to improve the secondary power losses, but also have the advantages of lower conduction voltage losses and faster reaction speed compared to the general rectifier with diode [8]. By the way, transistors are the main components utilized to act as rectifying role for the synchronization rectifier of the post stage. Hereafter, the meaning of synchronization stands for that the inversion of the switch timing of a transistor equal to the switch frequency of a switching power supply, and the primitive purpose is to reduce the high power losses caused by the larger current at the rectifying diode [10].

In this letter we aim in studying and implementing a power converter with high efficiency (above 96% in measuring with 120W loading), and the ZVS full-bridge converter IC ( 6754ISL ) [14], which was developed by Intersil Company, is applied. The reasons for selecting this conversion device are that it can be adopted in several fields of the power supply developing, such as power for telecommunication and information, power of base station, power of file server, and even power of industry. Besides, it can either obtain null voltage between switching state when applied in the pre-stage control or

Joy I.-Z. Chen et al: A High Efficiency Full-bridge Converter

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it can also applied in the post-stage for controlling a transistor to act as a rectifier. Thus, by utilizing 6754ISL for both investigating the synchronization rectifier to improve the efficiency in transmission and implementing a full-bridge power converter with less 120W to reach at the total efficiency above 96%. The implementing results shown that the total efficiency can be reach approximate above 90% when the loading is within the interval of 120W~720W without large power losses. It is worthy to note that for comparison purpose there is another resonance power sub-system implemented with 3895UCC taken into account the designed implementation [15]. These completed systems are compared with all the same conditions, that is, with 120W~720W power output loading, and both of them can gain high efficiency in above 90%~97% under the loading of 120W~720W. Such a high efficiency power converter implemented with synchronization rectifier technique definitely obtains the affect of saving power. The rest of the paper is organized as follows. In section 2 the preliminary includes the introduction of power converter and its control techniques are presented. In section 3 the procedures of implementation and measurement for the designed converter circuits are illustrated. Some measured waveforms and numerical data in the experiment are shown and explained in section 4. A brief conclusion is drawn in section 5.

2. Preliminary 2.1. The Construction of a ZVF Circuit

It is known that the ZVF converter generally has much complicate structure, since it is built up by at least 4 power transistors for switching. A basic construction of such configuration is shown in Fig. 1. Comparing to the configuration of a half-bridge voltage converter which has to bear larger current since it is just constructed by the transistors with lower voltage. Inversely, the specified current can be selected in lower value but higher voltage for the transistor utilized in a push-pull converter. In words, if the advantages described previous can be combined together, then a high power converter could be implemented by the transistor with both lower voltage and smaller current, and such a circuit structure is referred as full-bridge converter. A basic full-bridge converter is shown in Fig. 1 in which 4 MOSFET-type transistors marked in QA, QB, QC, QD are designed in the primary side of a transformer. When a paired switching transistor, for instance, QA and QD or QB and QC, are triggered on, the relative generating energy will be passed over the secondary side of the transformer. In other words, the converter will stay in the state of so-called flying-wheel model in which the paired switching transistor at the same side will be turned on simultaneously, e.g. the two QA and QC at the upper arm or QB and QD at the lower arm. The null voltage happens at the state of flying-wheel model because the primary of the transformer becomes as short circuit. In addition, a short period of delay time should be added into the signal duration as the switching state, i.e. the 4 transistor are both staying in cut-in or cut-off state for the reason to generate resonance function in the circuit.


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Fig. 1 Basic structure of ZVF converter

2.2 .The Requirements for Switching Power Transistors

In the paper two types of power converter are implemented for comparing purpose and established with the likely structure, that is, the first one implemented in the condition of higher power output. Thus, the converter IC, 6754ISL developed by Intersil, provides with synchronization rectifier is implied in such a converter. The converter IC, 3895UCC developed by Texas Instruments, supports for resonance circuit is applied in the other type of power converter. Consider the switching speed happens on the high frequency switching circuit, the power MOSFET transistors are the most frequently for usage because it has the shorter switching duration. By the way, the main concerning focus on the conducting resistance of a switching transistor, hence, the type number IRFP460 is adopted in this implementation and some parameters of this MOSFET are listed in Table 1.

Table 1. Some important parameters of IRFP460

Type number DSSV DI ( )DS onR issC ossC gQ

IRFP460 500V 20A 0.270 4100pf 480pf 120nC

2.3 The Designing in High Frequency Transformer

The main function of a transformer is to pull up the output voltage, to transmit the energy, and to reach at the isolation between the input and the output in the ZVF. Accordingly, the core of a transformer should not only be selected with high conduct magnetic coefficient, but the saturation flux density also should be the necessary condition. Thereafter, the larger operation space of flux can be obtained. A high frequency transformer with EE-type core is applied in the study so as to gain high capacity above 720 W, the operating frequency and the efficiency are about 100KHZ and 90%, respectively. The output capacitor is another factor needs to remind, normally, it is applied to store the energy for the purpose of keeping the output voltage on the continuity and stability state. Since the ESR (equivalent serial resistance) caused by the output capacitor will directly affect the ripple voltage value at the output, the output capacitor with less capacity should be adopted,


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e.g. the parallel of combining tantalum capacitor or ceramic electric capacitor with polypropylene membrane is the best method. 3. Procedures of Implementation and Measurement

Not only the larger power converter adopted in the implementation is necessary, but also to note the promotion in the efficiency is important. In such situation a converter embedded with synchronization rectifier converter and the other one equipped with resonance converter are built to compare the functions each other. In the implementation the former and the latter construction are completed with a synchronization rectifier converter IC, Intersil 6754ISL , and a resonance converter IC, Texas Instruments

3895UCC , respectively. Moreover, all the specifications of the two converter IC are describer as follows, input voltage ( inV ) DC0V ~ DC300V, output voltage ( outV )DC120V, maximum output current 6outI A= , switching frequency 100sf KHZ= , and the output power range is 120W~720W.

3.1 Designing 6754ISL Circuit

In this subsection including pre-stage input, post-stage output circuits and the frequency of 6754ISL , and 2110IR driver are planned. The planning circuit of 6754ISL is shown in Fig. 2 in which the output voltage can handled by adjusting the ERRV voltage values, i.e. the output voltage of OUTULOUTUROUTLLOUTLROUTULOUTURs could be controlled as periodical rectangular waveforms. The 4 output points of 6754ISL , OUTLL, OUTLR, OUTUL, and OUTUR are applied to control 4 MOSFETs.

1

56789

10

234

11121314151617181920VREF

VERRCTBUFRTDRESDELCTFBRAMPCSIOUT GND

OUTLRNOUTLLNOUTUROUTULOUTLROUTLLVDDVADJSS

ISL6754

104

C1

46KR1

331C3

104C2

10KR4 10KR3

10KR2

104C4

104C5

+12

Ai

Bi

Ci

Di

FiEi

10KVR1

Fig. 2 6754ISL control circuit

As shown in Fig. 3 the waveforms of OUTULOUTUROUTLLOUTLR are

different each other and those waveform depend on the voltage value of ERRV which is arranged in the interval 1~5V. The least energy state stays at 1ERRV V= in which OUTLR and OUTLL modulate OUTUR and OUTUL, respectively as shown in Fig. 5. The other


447

state stays at 5ERRV V= presented in Fig. 4 in which the output energy has the biggest value OUTLR and OUTLL are corresponding to modulate OUTUL and OUTUR, respectively.

OUTUL

OUTLL

OUTUR

OUTLR

Fig. 3 Four different output waveforms of 6754ISL , when 1ERRV V=

OUTUL

OUTLL

OUTUR

OUTLR

Fig. 4 Four different output waveforms of 6754ISL , when 5ERRV V=

3.1.2 The Synchronization Rectifier Circuit The sequences of synchronization rectifier for 6754ISL are achieved by OUTLLN and

OUTLRN. Hence, the rectifying diodes in the post-stage have to be replaced by MOSFET in order to active as a rectifier. The waveforms of OUTLLN and OUTLRN are measured and illustrated in Fig. 5 with the value of 1ERRV V= . In Fig. 5 the waveform of OUTUL is marked 1, waveform of OUTLR is marked with 2, and waveform of OUTLLN and OUTLRN are marked 3 and 4, respectively. Alternately, in Fig. 6 shows the waveforms with the condition of 5ERRV V= , and the shown order is same as that of Fig. 5.


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OUTUL

OUTLL

OUTUR

OUTLR

Fig. 5 Four measured waveforms with 1ERRV V=

OUTUL

OUTLL

OUTUR

OUTLR

Fig. 6 Four measured waveforms with 5ERRV V=

3.2 Designing 3895UCC Circuit

Four divisions are planned for the implemented circuit with 3895UCC including pre-stage input, post-stage output, 3895UCC switching, and driver with 2110IR .

3.2.1 Planning the 3895UCC Driver for Full-bridge Converter

The IC 3895UCC is one controller used to modulate the phase shifter with the scheme of PWM (Pulse width modulation). The turn on and/or off a half-bridge converter circuit corresponding to the other one is the technique to realize full-bridge power conversion. The scheme of permanent pulse width modulation combined with resonance null voltage switching is adopted as a current or a voltage control model for providing with high efficiency operation. The oscillator output with a 3895UCC is shown in Fig. 7 in which the components TC and TR are constructed to adjust the operation frequency. The full implemented circuit is shown in Fig. 8. The operation frequency can be determined by

5120

48T T

oscR CT = + (ns) (5)

For example, the operation frequency 90OSCT KHZ= can be figured out by the substitution of 70TC pf= and 120TR K= into the previous equation.


449

Fig. 7 The oscillator circuit with 3895UCC

104

C1

103C2

120K

R4

10K

R1 EA-1 EAO2

RAMP3

VREF4

GND 5

SYNC 6

CT7

RT8

DELAB9

DELCD10ADS 11ISNS 12

OUTD 13OUTC 14

VDD 15

PGND 16

OUTB 17OUTA 18

SOFT19EA+20

UCC3895

U1

471C10

7.5K

R5

7.5K

R6

/+12

AiBiCiDi

PWM

G1

331C47

VOF390RR35

9K1R41

Comment: 5V

Z2

/+12

104C71

OV1

104C22

4.7UF/50V

C3

Fig. 8 The complete implemented circuit

Several different frequencies generate in 3895UCC are obtained and listed in Table 2

by measuring and calculating in the experimental procedure. Once the fixed frequency is decided, the values of TC and TR can to be calculated. Some referenced values of TC is listed in Table 3. Hence, the TR is also can be determined by the formula written as

40 47 0 07 47 17 5 10+

T oscT

T osc

C fR

C f. . .

(6)


450

Table 2 Measured and calculated frequencies values in 3895UCC

TC TR Frequencies by measuring Frequencies by calculating 450PF 100K 107K 104K

120K 90K 87K 200K 55K 52.6K

Table 3 The decision range of TC

Range of frequencies Values of TC

oscf < 30KHZ 2 2nF.

30KHZ < oscf < 100KHZ 680 pF

100KHZ < oscf 200 pF

The simulation waveform results from the experimental procedure of implementing the

circuit for UCC3895 are measured and shown in Fig. 9. Four different output waveform are illustrated as OUTAiOUTBi OUTCi OUTDi. It is clear to understand that the phase shift happens in OUTAi OUTBi is caused by OUTCiOUTDi, respectively, and this is completed (or modulated) at the pin 20 of 3895UCC . However, the values of phase shift change insignificantly, see Fig. 10, when try to increase the loading and the loading feedback voltage is adjusted to 1ERRV V= . On the other hand, the output waveforms are going become as presented in Fig. 11 after the loading feedback voltage is modified as

5ERRV V= . This explains that the energy stored in the ZVS may release under the conditions that OUTCi to OUTAi, OUTDi to OUTBi are corresponding each other.

OUTAi OUTBi OUTCi OUTDi

Fig. 9 Four output waveforms in 3895UCC


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Fig. 10 Four output waveforms in 3895UCC when 1ERRV V=

Fig. 11 Four output waveforms in 3895UCC when 5ERRV V=

3.2.2 Description of Pre-stage Input and Post-stage Output

The pre-stage input and post-stage output are isolated by a frequency transformer. The former stage mainly consisted of driver, which is constructed by two IC marked as

2110IR , and full-bridge converter illustrated in Fig. 12. The rectifier and filter circuits shown in Fig. 13 are involved in the post-stage, and in which are composed by a U30D60D diode and a -type filter, respectively.

D4U30D60D

15UH

XL6

15UH

XL5

15UH

XL4

10KR9

10K R1210K R11

10K R9_110K R10

Q1

25NM50N

Q2

25NM50N

Q3

25NM50N

Q4

25NM50N

Q1_1

25NM50N

C20

205

VadVad

Vad

Co2_1

Do2_1

Co2 Do2

Co2

Do2

Ao1 Bo1

Bo2

Ao2

Ao1 Bo1

10K R11_125NM50N

Q4_1

R10_110K25NM50N

Q3_1

10K R12_1

25NM50NQ2_1

Fig. 12 The structure of full-bridge converter


452

Vab

2UFC21

104/630VC23

Co2_Do2

Ao1_Bo1150UHXL1

470UF/400VC13

2UF

C14

23

1 U30D60DD3

U30D60D

D5

1

4

2

3

5

T1

GAP_IN+

GAP_IN-

10UHXL2

10UHXL3104K/PP630V

C68104K/PP630V

C69

1234

4PIN

TB1

Vin+Vin-Vout+Vout-

104K/PP630V

C69

Fig. 13 Rectifier and filter circuit

It is worthy to note that the post-stage is always burn down before the 49C is installed.

By measuring with the OSC scope, the phenomena looked for the reason that caused by the burst waveforms as shown in Fig. 14 (a). However, it disappears after 49C is installed and this normal waveform shown in Fig. 14 (b)

Fig. 14 The waveforms before 14 (a) and after 14 (b) 49C installed

3.3 The Implementation Circuit with IR2110 Driver

It is well known that a MOSFET is driven by the voltage when it is play as a switch, i.e., there exists a cross threshold voltage between the gate and source of the MOSFET and which needs keep the threshold voltage then the MOSFET can keep in working state. Thus, in this implementation the cross threshold voltage of the MOSFET in the full-bridge converter is applied to promote the input voltage from 5V to 15V. The main specifications of 2110IR are claimed as follows, (1) a dual input and dual output IC, (2) null dead time embedded, (3) the difference voltage can approach to 500V, (4) output voltage is measured about 10V~20V, (5) the switch time is / 120 / 94on offt t ns ns= . It needs to plan one half-bridge circuit as illustrated in Fig. 15. Then the full-bridge converter is

Burst waveform


453

comprised by these two aforementioned. The measured waveforms from the converter are presented in Fig. 16.

3W 10RR7

3W 10RR8

104C12

31DF4

D2

/+12

/+12

104

C8

104C11

NC 8

VD

D9

HIN10

SD11LIN12

VSS

13

NC 14

L0 1

CO

M2

VC

C3

NC 4

Vs5Vb6

H0 7

IR2110U3

OUTUROUTLR

Co2Do2

104

C6

205

C20

IRF460Q3

10KR10

IRF460Q4

10KR11

Co2

Do2

Co2_D

Vab

U30D60D

D4

Fig. 15 One half-bridge converter

Hi Lo Hi

Lo

Fig. 16 Waveforms from the measurement of converter 4. Experimental Results

The implementation of the converter developed in this paper can be applied in high power converter. The circuit configuration is so-called pull-up synchronizing rectifier full-bridge converter which is implemented by using of post-stage synchronizing rectifier to promote the full efficiency. The adjustable output voltage, outV , is obtained by the pull-up converter to pull up the input voltage. A synchronizing rectifier with the unchangeable duty-cycle 50% for the main switch is built up at post-stage.

4.1 Analysis of the Measured Data

In this subsection the measured data of two power converters, which has the same power conversion range 120W~720W, are compared and analyzed. In the first one, the conversion switch 3895UCC is employed to set up a power switch which applies the traditional power control, and the U30D60D is adopted as a power diode set up at the post-stage. Then, the


454

other one built up with Intersil 6754ISL named as ZVS power converter in which the PWM scheme is used as the power controlled switch, and the usage of MOSFET is to complete the function of synchronizing rectifier. The specifications of these two power converters are figured out as follows, input DC voltage 0 ~ 300inV V= , output DC voltage 120outV V= , switching frequency =100sf KHz , and the transformer core is EE55. The resistance loading applied to the implementation and the rearrangement are shown in Fig. 17 in which each branch resistance is assigned to 120/200W so as to use just one resistance loading for the case of loading is equivalent to 120W.

Fig. 17 Designated resistance loading

The two power converters are implemented and completed in a broad plane shown in Fig. 18 in which all the circuit are same in the pre-stage, but the post-stage circuit are with different PWM switch scheme. The different PWM control, 6754ISL or 3895UCC switching power MOSFET, and driver circuit are included in the pre-stage. Furthermore, the rectifier circuit and output filter circuit are included in the post-stage as shown in Fig. 19. Certainly, the post-stage is configured with MOSFET (IRF460) components when the

6754ISL is employed to PWM, in contrast, the diode (U30D60D) is set up at the post-stage when 3895UCC is used to control PWM.

Fig. 18 pre-stage circuit

POWER MOSFET CKT IRF460

Driver CKT IR2110

PWM IC CKT UCC389

PWM IC CKT ISL6754


455

Fig. 19 post-stage circuit

4.1.1. Results from the Applied of 3895UCC

The data listed in Table 4 is the measured data comes from input voltage and output current of 3895UCC and the input/output power can be consequently calculated as from 120W to 720W. With the lower and higher loading, the output power may be evaluated as 123.83W and 685.58W, respectively. Accordingly, it is clear to make sense that the output efficiency becomes inferior when the output is beyond 400W.

4.1.2 Results from the Applied of 6754ISL

The measured data results from input voltage and output current of 6754ISL converter

are listed in Table 5, and the output power is arranging in same as that of 3895UCC . In words, the power generated at output are 128.06W and 696.33W corresponding to the lower value and higher loading value. This trend of the fact is same as that of 3895UCC , however, the conversion efficiency can be still always kept in about 90% when the power is over 600W.

Table 4 The measured results of the implementation of 3895UCC

Assigned power

Measured Power

120W 240W 360W 480W 600W 720W

inV (V) 52.58 60.64 66.93 74.25 80.9 87.31

inI (I) 2.473 4.177 5.775 7.13 8.209 8.966

inP (W) 128.13 253.29 386.52 529.4 664.1 782.82

outV (V) 120.7 119.4 121.2 120.6 121.5 121.5

outI (I) 1.026 1.952 2.909 3.96 4.898 5.666

outP (W) 123.83 233.06 352.57 477.57 595.1 685.58 100 =

out inP P( ) % 96.64 92.01 91.21 90.20 89.6 87.57

High frequency Transformer

Rectifier U30D60 or IRFP460

Filter


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4.2 The Comparison of Power Efficiency

As the fact claimed in Fig. 21 that the conversion efficiency will decrease to below 90% when the power converted is implemented by 3895UCC . Thus, the efficiency will approach to much less while the loading increase. In contrast, the conversion efficiency can be still always kept in about 90% when the power is over 600W for 6754ISL . Therefore, the results from the comparison between 6754ISL and 3895UCC are shown in Fig. 20, i.e. the almost same values of power can be achieved with different IC such as

3895UCC and 6754ISL as long as the values at Pin1 and Pin2 are almost equivalent. In addition, such as the cases of Pout1 and Pout2 shown in Fig. 20 where the output power approximately equals with the condition of the output voltage is assigned at DC 120V. Apart from the analysis of the power efficiency for the two different scenario are presented in Fig. 21 in which Pin1 and Pout1 are assigned as input power and output power of the converter 3895UCC , respectively. With the same assignment Pin2 and Pout2 indicates the input and output power of the converter 6754ISL , respectively.

The loading range at the output is controlled in the interval 120~20 for the two converters, and the current is held over 1A~6A. It is reasonable to describe some facts from Fig. 21 as follows: (1) the converter equipped with 6754ISL , which has the ability of synchronizing rectifier, can gain high electrical conversion, since above 90% conversion efficiency can be obtained in such an implementation, (2) both the switch can arrive at the rules of ZVS for whichever of 3895UCC or 6754ISL converter during the switching time, and the highest power efficiency of 96.64% and 97.13% can be achieved respectively. This fact describes that the soft switching technique can be definitely employed to improve the problem of switching power losses, (3) in terms of solving the critical issue of conduction losses caused by the rectifying diode with heavy loading, the

6754ISL converter illustrates more significant in improving the power efficiency than that of 3895UCC , since the former one has the ability of synchronizing rectifier.

Table 5 The measured results of the implementation of 6754ISL

Assigned power

Measured data

120W 240W 360W 480W 600W 720W

inV (V) 52.32 60.52 66.82 74.52 80.82 87.42

inI (A) 2.52 4.18 5.73 7.04 8.07 8.81

inP (W) 131.84 252.97 382.87 524.62 652.21 770.17

outV (V) 120.7 120.2 120.6 120.3 120.4 120.1

outI (A) 1.061 1.994 2.933 3.994 4.973 5.798

outP (W) 128.06 239.6 353.71 480.47 598.74 696.33 100 =

out inP P( ) %

97.13 94.72 92.38 91.58 91.8 90.41


457

128.13253.29

386.52

529.4

664.1

782.82

123.83233.06

352.57477.57

595.1685.58

131.84252.97

382.87

524.62652.21770.17

128.06239.6353.71

480.47598.74

696.33

0100200300400500600700800900

120W 240W 360W 480W 600W 720W

Measured power

AssignedPower

Pin1 Pout1

Fig. 20 The comparison of input-output voltages for two different circuits

96.6492.01 91.21 90.2 89.6 87.57

97.1394.72 92.38 91.58 91.8 90.41

80859095

100

120W 240W 360W 480W 600W 720W

Efficiency

Power

1 2

Fig. 21 The comparison of efficiency between 1: 3895UCC , 2 : 6754ISL

5. Conclusion and Suggestion

A high power efficiency full-bridge converter is investigated and implemented with an experiment in which a ZVS full-bridge converter IC, 6754ISL developed by Intersil, is adopted as a main component controller in this paper. On the other hand, the measured data result from the other one implemented by IC 3895UCC converter is to compare with that of the converter aforementioned.

It is well known that the converter with a synchronizing rectifier can create high conversion efficiency just when the loading is light. Nevertheless, it should be possible to developed an alternative way which the synchronizing switch can be powered off during the loading is lower than a threshold value, and in order to break off the synchronizing switch just by using parasitic diode to establish a complete rectifier for saving the switching losses. The volume size is also a problem for considering in cost effective direction. Finally, to joint PFC (power factor correction) technique for developing high quality power converter providing to all the consumers is one of the important targets for all the countries in the world. Certainly, one part is to promote the capacity in power supporting and the


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other part to increase both the power factor and the power efficiency are necessary for the best total solution. References [1] S. H. Chung, S. Y. Hui, and W. H. Wang, A zero-current-switching PWM fly-back converter with a simple

auxiliary switch, IEEE Transactions on Power Electronics, vol. 14, no. 2, pp. 329-342, Mar. 1999. [2] Adib, E.; Farzanehfard, H., Zero-Voltage Transition Current-Fed Full-Bridge PWM Converter, IEEE

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