Novel Zero-Voltage and Zero-Current-Switching Full-Bridge PW

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IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS,VOL.35,NO.1,JANUARY/FEBRUARY199915 Novel Zero-V oltage and Zero-Current-Switching Full-Bridge PWM Converter Using

a Simple Auxiliary Circuit

Jung-Goo Cho,Member,IEEE,Ju-Won Baek,Chang-Yong Jeong,and Geun-Hie Rim,Member,IEEE

Abstract—A novel zero-voltage and zero-current-switching (ZVZCS)full-bridge pulsewidth modulation converter is presented to simplify the circuits of the previously presented ZVSCS converters.A simple auxiliary circuit,which consists of one small capacitor and two small diodes,is added in the secondary to provides ZVZCS conditions to primary switches,as well as to clamp secondary recti?er voltage.The additional clamp circuit for the secondary recti?er is not necessary.The auxiliary circuit includes neither lossy components nor additional active switches,which makes the proposed converter ef?cient and cost effective.The principle of operation,features,and design considerations are illustrated and veri?ed on a2.5-kW100–kHz insulated-gate-bipolar-transistor-based experimental circuit. Index Terms—DC/DC converter,insulated gate bipolar tran-sistor,soft switching.

I.I NTRODUCTION

W ITH THE increasing demand for higher power den-sity power conversion with lower cost,insulated gate bipolar transistors(IGBT’s)are considered as power devices instead of MOSFET’s in the high-frequency high-power ap-plications,since IGBT’s have higher power density and lower cost compared to MOSFET’s.The operating frequency of IGBT’s,however,is much lower than MOSFET’s,(usually limited to20–30kHz)[1]because of higher switching loss which comes from the tail current during the turn-off period. Therefore,to operate IGBT’s at higher switching frequencies, it is required to reduce the turn-off switching loss.Zero-voltage switching(ZVS)with a substantial external snubber capacitor or Zero-current switching(ZCS)can be a solution,but the ZCS is more effective than ZVS,since the tail current can be eliminated by removing the minority before turning off[4]. To apply IGBT’s for high-frequency(around100kHz) high-power full-bridge dc/dc converters,a ZVZCS technique has been introduced and a couple of ZVZCS full bridge (FB)pulsewidth modulation(PWM)converters have been presented[5]–[9].The ZVZCS means mixed operation of ZVS for leading-leg switches and ZCS for lagging-leg switches. The ZVS of leading-leg switches is achieved by the same Paper IPCSD98–62,presented at the1998IEEE Applied Power Electronics Conference and Exposition,Anaheim,CA,February15–19,and approved for publication in the IEEE T RANSACTIONS ON I NDUSTRY A PPLICATIONS by the Industrial Power Converter Committee of the IEEE Industry Applications Society.Manuscript released for publication August3,1998.

The authors are with the Power Electronics Research Division,Korea Electrotechnology Research Institute,Changwon,641-120Korea. Publisher Item Identi?er S0093-9994(99)00447-8.manner as that of the ZVS FB PWM converters[2],[3], while the ZCS of lagging-leg switches is achieved by resetting the primary current during the freewheeling period.So far,a couple of ZVZCS-FB-PWM converters have been presented [5]–[9].Their primary currents during freewheeling period, however,are reset by different manners.In the converter[5], the primary current is reset by using the reverse avalanche breakdown voltage of the leading-leg IGBT’s,where the stored energy in the leakage inductance is completely dissipated in the leading-leg IGBT’s.This approach is not ef?cient,unless the leakage inductance is very small.In the converter[6],the primary current is reset by using the dc blocking capacitor voltage and adding a saturable reactor.The saturable reactor loss limits the maximum power level by5kW.In the converter [7],the primary current is reset by adding an active clamp in the secondary side,which provides ZVZCS condition to the primary switches,as well as the active clamp of the secondary recti?er.The additional switch,however,makes switching loss due to hard switching and increases cost and control complexity.In the converter[8],the primary current is reset by adding a snubber circuit in the secondary side. There are no lossy components in the snubber circuit,however, the large circulating energy by the resonance between the leakage inductance and snubber capacitors reduces the overall ef?ciency and increases the voltage rating of the secondary recti?er diodes by two times.In the converter[9],the primary current is reset by using the transformer auxiliary winding. Neither lossy components involved nor an additional active switch are added.Besides,no large circulating energy is generated.All active and passive devices are operated under minimum voltage and current stresses.This approach can handle more than10kW,but the auxiliary circuit is a little bit complex.

This paper proposes a novel ZVZCS-FB-PWM converter with a simple auxiliary circuit to improve the previously presented ZVZCS-FB-PWM converters(see Fig.1).The ZVS mechanism of leading-leg switches is also the same as that of the converters in[2],[3],and[5]–[9].A simple auxiliary circuit provides not only ZVZCS condition to the primary switches,but clamping of the secondary recti?er.Therefore, most of the problems of the previous ZVZCS converters are solved and,furthermore,an additional passive or active clamp circuit is not necessary.

The operation,analysis,features,and design considerations of the proposed converter are illustrated.A2.5-kW100-kHz

0093–9994/99$10.00©1999IEEE

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16IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS,VOL.35,NO.1,JANUARY/FEBRUARY

1999Fig.1.Circuit topology of the proposed ZVZCS-FB-PWM

converter.

Fig.2.Operation waveforms of the proposed converter.

prototype has been built using IGBT’s and tested to verify the

principle of operation.

II.O PERATION P RINCIPLE

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