Zero Voltage Switching Turn-on Research Articles

Implementation of a parallel zero-voltage switching DC–DC converter with fewer active switches

A parallel soft-switching DC–DC converter with fewer switch count is presented to achieve zero-voltage switching (ZVS), load current sharing and partially output ripple current cancellation. Two buck-type converters are connected in parallel to achieve load current sharing. Only two MOSFETs are used in the proposed converter instead of four switches in a conventional parallel ZVS forward converter. Therefore the proposed converter has fewer active switches. Current-doubler rectifiers are used in the output side in order to achieve partially ripple current cancellation. Therefore the current ripple on output capacitor is decreased and the size of the output choke and output capacitor are reduced. An active snubber is connected between two power transformers to absorb the energy stored in the leakage and magnetising inductances of transformers, to limit voltage stresses across switches, and to achieve ZVS turn-on for all switches. The ZVS turn-on is implemented in the transition interval of two complementary switches such that the switching losses and thermal stresses on semiconductors are reduced. Operation principle, circuit analysis and design example are discussed in detail. Finally, experimental results for a 360 W (12 V/30 A) prototype were presented to verify the effectiveness of the proposed converter.

Nonisolated ZVZCS Resonant PWM DC–DC Converter for High Step-Up and High-Power Applications

The demand for nonisolated high step-up dc-dc converters in applications such as dc backup energy systems for UPS, photovoltaic and fuel cell systems, and hybrid electric vehicles has been gradually increasing. This paper proposes nonisolated step-up dc-dc converters with an improved switching method. The proposed converter shows zero-voltage switching turn-on of the switches in continuous conduction mode as well as reduced turn- off switching losses owing to the switching method that utilizes Lr-Cr resonance in the auxiliary circuit. Also, as a result of the proposed switching method, the switching losses associated with diode reverse recovery become negligible even in the small duty cycle. The capacitance in the auxiliary circuit is significantly reduced compared to the pulsewidth modulation method. The duty cycle loss is further reduced resulting in increased step-up ratio. Experimental results from a 2-kW prototype of a two-phase interleaved version are also provided to validate the proposed concept.

Analysis, Design and Implementation of an Interleaved DC/DC Converter with Series-Connected Transformers

An interleaved DC/DC converter with series-connected transformers is presented to implement the features of zero voltage switching (ZVS), load current sharing and ripple current reduction. The proposed converter includes two half-bridge converter cells connected in series to reduce the voltage stress of the switches at one-half of the input voltage. The output sides of the two converter cells with interleaved pulse-width modulation are connected in parallel to reduce the ripple current at the output capacitor and to achieve load current sharing. Therefore, the size of the output chokes and the capacitor can be reduced. The output capacitances of the MOSFETs and the resonant inductances are resonant at the transition instant to achieve ZVS turn-on. In addition, the switching losses on the power switches are reduced. Finally, experiments on a laboratory prototype (24V/40A) are provided to demonstrate the performance of the proposed converter.

직접전력변환 방식을 이용한 능동 클램프 AC-DC 컨버터

This paper proposes an active-clamp ac-dc converter with direct power conversion that has a simple structure and achieves high efficiency. The proposed converter is derived by integrating the step-down ac chopper and the output-voltage doubler. The proposed converter provides direct ac-dc conversion and dc output voltage without using any full-bridge diode rectifier. The step-down ac chopper using an active-clamp mechanism serves to clamp the voltage spike across the main switches and provides zero-voltage turn-on switching. The resonant-current path formed by the leakage inductance of the transformer and the resonant capacitor of the output-voltage doubler achieves the zero-current turn-off switching of the output diodes. The operation principle of the converter is analyzed and verified. A 500W prototype is implemented to show the performance of the proposed converter. The prototype provides maximum efficiency of 95.1% at the full load.

Interleaved DC-DC Converters with Partial Ripple Current Cancellation

An interleaved PWM converter is proposed to implement the features of zero voltage switching (ZVS), load current sharing and ripple current reduction. The proposed converter includes two ZVS converters with a common clamp capacitor. With the shared capacitor, the charge balance of the two interleaved parts is automatically regulated under input voltage and load variations. The active-clamping circuit is used to realize the ZVS turn-on so that the switching losses on the power switches are reduced. The ZVS turn-on of all of the switching devices is achieved during the transition interval. The interleaved pulse-width modulation (PWM) operation will reduce the ripple current and the size of the input and output capacitors. The current double rectifier (CDR) is adopted in the secondary side to reduce output ripple current so that the sizes of the output chokes and capacitor are reduced. The circuit configuration, operation principles and design considerations are presented. Finally experimental results based on a 408W (24V/17A) prototype are provided to verify the effectiveness of the proposed converter.

Analysis, Design and Implementation of an Interleaved Single-Stage AC/DC ZVS Converters

An interleaved single-stage AC/DC converter with a boost converter and an asymmetrical half-bridge topology is presented to achieve power factor correction, zero voltage switching (ZVS) and load voltage regulation. Asymmetric pulse-width modulation (PWM) is adopted to achieve ZVS turn-on for all of the switches and to increase circuit efficiency. Two ZVS half-bridge converters with interleaved PWM are connected in parallel to reduce the ripple current at input and output sides, to control the output voltage at a desired value and to achieve load current sharing. A center-tapped rectifier is adopted at the secondary side of the transformers to achieve full-wave rectification. The boost converter is operated in discontinuous conduction mode (DCM) to automatically draw a sinusoidal line current from an AC source with a high power factor and a low current distortion. Finally, a 240W converter with the proposed topology has been implemented to verify the performance and feasibility of the proposed converter.

Novel topology of ac–dc converter using direct power conversion

This study proposes a novel topology of the ac–dc converter using direct power conversion that has a simple structure and achieves high efficiency. The proposed converter is derived by integrating the step-down ac chopper and the output-voltage doubler. The proposed converter provides direct ac–dc conversion and isolated dc output voltage without using any full-bridge diode rectifier. The step-down ac chopper using an active-clamp mechanism serves to clamp the voltage spike across the main switches and provides zero-voltage turn-on switching. The resonant-current path formed by the leakage inductance of the transformer and the resonant capacitor of the output-voltage doubler achieves the zero-current turn-off switching of the output diodes. The operation principle of the converter is analysed and verified. A 500 W prototype is implemented to show the performance of the proposed converter. The prototype provides maximum efficiency of 95.1% at the full load.

Implementation of parallel zero-voltage switching converter with series-connected transformers

SUMMARY This paper presents a parallel zero-voltage switching (ZVS) DC–DC converter with series-connected transformers. In order to increase output power, two transformers connected in series are used in the proposed converter. Two buck-type converters connected in parallel have the same switching devices. The primary windings of series-connected transformers can achieve the balanced secondary winding currents. The current doubler rectifiers with ripple current cancellation are connected in parallel at the output side to reduce the current stress of the secondary winding. Thus, the current ripple on the output capacitor is reduced, and the size of the output choke and output capacitor are reduced. Only two switches are used in the proposed circuit instead of four switches in the conventional parallel ZVS converter to achieve ZVS and output current sharing. Therefore, the proposed converter has less power switches. The ZVS turn-on is implemented during the commutation stage of two complementary switches such that the switching losses and thermal stresses on the semiconductors are reduced. Experimental results for a 528-W (48 V/11 A) prototype are presented to prove the theoretical analysis and circuit performance. Copyright © 2011 John Wiley & Sons, Ltd.

A Three-Phase Current-Fed Push–Pull DC–DC Converter With Active Clamp for Fuel Cell Applications

In this paper, a new active-clamped three-phase current-fed push-pull dc-dc converter is proposed for high-power applications where low-voltage high-current input sources such as fuel cells are used. The proposed converter has the following features: active clamping of the transient surge voltage caused by transformer leakage inductances, natural zero-voltage switching turn-on of main switches using energy stored in transformer leakage inductor, small current rating and zero-voltage and zero-current switching of clamp switches, no additional start-up circuitry for soft starting due to the operating duty cycle range between 0 and 1, and zero-current switching turn-off of rectifier diodes leading to negligible voltage surge associated with the diode reverse recovery. A comparative study along with loss analysis is performed. Experimental results from 5-kW laboratory prototypes of the proposed active-clamped converter and the passive-clamped converter are provided.

Multiphase DC–DC Converters Using a Boost-Half-Bridge Cell for High-Voltage and High-Power Applications

In this paper, multiphase dc-dc converters are proposed for high-voltage and high-power applications. A generalized converter is configured such that the boost-half-bridge (BHB) cells and voltage doublers are connected in parallel or in series to increase the output voltage and/or the output power. In addition to reduced device voltage and current ratings by the connection, the proposed converter has the following features: high-step-up voltage gain with significantly reduced transformer turn ratio, low-input current ripple due to interleaving effect, zero-voltage switching turn-ON of switches and zero-current switching turn-OFF of diodes, no additional clamping and start-up circuits required, high-component availability and easy thermal distribution due to the use of multiple small components, and flexibility in device selection resulting in optimized design. A design guideline of determining the optimum circuit configuration for given output voltage and power level is presented. Experimental results are also provided to validate the proposed concept.

Implementation of a parallel zero-voltage switching forward converter with less power switches

A parallel zero-voltage switching (ZVS) forward converter is proposed to achieve load current sharing, output ripple current cancellation and conversion efficiency improvement. Two forward converters are connected in parallel to achieve interleaved pulse width modulation operation. Thus, the ripple currents on the output side are partially cancelled on each other so that the size of output chokes and capacitor is reduced. Only two switches are used in the proposed converter instead of four switches in the conventional parallel ZVS forward converter. Therefore the proposed converter has less power switching devices. An active snubber is connected between two power transformers to absorb the energy stored in the leakage and magnetising inductances of transformers, to limit voltage stresses across switches and to realise the ZVS turn-on of all switches. Thus, the conversion efficiency is improved by the soft-switching operation of switching devices. Finally, the performance of the proposed converter is evaluated on a 480 W (24 V/20 A) laboratory prototype.

Interleaved DC–DC zero-voltage switching converter with series-connected in the primary side and parallel-connected in the secondary side

An interleaved zero-voltage switching (ZVS) forward converter is presented in this study. Two forward converter circuits with active snubber are used in the proposed circuit to share the load current. The interleaved pulse-width modulation (PWM) scheme is adopted to achieve current ripple reduction in the output capacitor. Thus, the size, weight and conduction losses of the output chokes are reduced. Only two switches instead of four switches in the conventional parallel ZVS forward converter are used in the proposed converter. Thus, the switch counts are reduced in the proposed circuit. The PWM signals of two switches are complementary each other with a small delay time in order to realise the ZVS turn-on at the transition interval. Thus, the switching losses and thermal stresses of the power switches are reduced. Experiments based on a 650 W prototype were provided to verify the theoretical analysis and the effectiveness of the proposed converter.

Analysis and implementation of an interleaved soft switching converter

An interleaved soft switching converter with active snubber circuit is presented here. The active snubber circuit not only absorbs the energy stored in the leakage inductor but also achieves zero-voltage switching turn-on feature for power switches. Moreover, the resonant tank which is composed of the leakage inductor and resonant capacitor is used to achieve zero current switching turn-off feature for rectifier diodes at the secondary side of transformer. Hence, the reverse recovery problem can be eliminated. The operational principle and design consideration are discussed in detail. Finally, experimental results taken from a 600W prototype are presented to confirm the effectiveness of the proposed converter.

ZVS Double-Ended Ćuk Converter

This brief presents a zero-voltage switching (ZVS) Ćuk converter with double-ended rectifier to reduce switching losses on power semiconductors, decrease voltage stresses on rectifier diodes, and achieve power delivery to the output load in both the positive and negative half cycles of the secondary winding voltage. An auxiliary switch and a clamp capacitor are connected in parallel with the primary side of the transformer to absorb all the energy stored in the transformer leakage inductance. The resonant inductance and the clamp capacitance are resonant to achieve ZVS of the auxiliary switch. On the other hand, the resonant inductance and output capacitance of the main switch are resonant to achieve ZVS turn-on of the main switch. Experimental results for a 300-W prototype circuit operating are given to demonstrate the effectiveness of the proposed converter.

Analysis, design and experimentation of an interleaved active-clamping buck-type converter

An interleaved pulse-width modulation (PWM) zero voltage switching (ZVS) converter is presented in this article. Two converter modules with an interleaved PWM scheme are used in the proposed circuit to achieve load current sharing and to reduce the ripple currents on the input and output capacitors such that the size of the output choke and capacitor is reduced. For each module, two buck-type dc–dc converters with only two switches are used to reduce the current rating of transformer winding and share the load current. Two buck-type converters in each module use the same switching devices to regulate the output voltage. The ZVS turn-on of the switches is achieved by utilising the transformer leakage inductance and output capacitance of switches. Thus, the switching losses of the proposed converter are reduced. Experiments based on a 660 W prototype are provided to verify the theoretical analysis and the effectiveness of the proposed converter.

Cost-effective resonant circuit with fast energy transfer speed for plasma display panels

A simple and cost-effective sustain circuit with energy recovery and injection function is proposed based on reduced number of circuit components and fast energy transfer speed for plasma display panels (PDPs). The proposed driver configures the sustain circuit and the resonant circuit in such a way that the resonant network is energized by the sustain voltage level and the ground level in charging and discharging the panel capacitor, respectively. Due to this structure, the energy transfer through the panel is twice as fast as the conventional drivers biased by half sustain voltage level. This faster energy transfer speed can lead to the increased number of sustain pulses or the increased address lines, which can improve image brightness or display resolution, respectively. Moreover, the over-excited resonant network enables the panel voltage to fully rise up to the sustain voltage and fall down to the ground, despite of unavoidable parasitic resistance on the circuits. This operation insures zero-voltage turn-on switching for all the sustain switches, which yields reduced switching losses in the driver. Furthermore, the resonant circuit of the proposed driver is installed to function for the energy recovery/injection operation at both the Y and the X electrodes. Due to the semiconductor devices shared in common as well as simplified arrangement, the developed structure can be designed with fewer devices than the conventional approaches. As a result, the PDP driver presented in this paper can feature reduced number of switching devices, faster sustain voltage transition, higher brightness, and smaller size.

Analysis and implementation of an active-clamping zero-voltage turn-on switching/zero-current turn-off switching converter

A new isolated dc/dc converter with zero-voltage turn-on switching (ZVS) of power switches and zero-current turn-off switching (ZCS) of diodes is presented. In conventional flyback converters, the main drawbacks are high voltage stresses on power devices, large transformer size and serious reverse recovery current, which resulted in high voltage spikes across output diode. To solve these problems, a buck-boost type of active-clamp circuit is connected in parallel with the primary winding to clamp the voltage spike across the power switch, to recycle the energy stored in the leakage and magnetising inductances of the transformer and to realise the turn-on ZVS by utilising the leakage inductance and output capacitance of the switch. The leakage inductance and the resonant capacitance on the secondary side are resonant to allow the output diodes to turn off at ZCS. Thus, the switching losses and thermal stresses of switches and diodes are reduced, the output diode has no reverse recovery problem and voltage stresses of the output diodes are clamped to the output voltage. Experiments conducted on a laboratory prototype rated at 270 W are provided to verify the effectiveness of the proposed converter.

Zero voltage switching double-ended converter

A new zero voltage switching (ZVS) converter with a double-ended rectifier is presented to reduce switching losses on power semiconductors, decrease voltage stresses on rectifier diodes and achieve bidirectional power delivery to output load. A buck-boost type of active snubber is connected in parallel with the primary side of a transformer to recycle the energy stored in transformer leakage and magnetising inductors and to limit voltage stress on the main switch. During the transition interval, the transformer leakage inductor and the output capacitor of power MOSFET are resonant to realise the ZVS turn-on of the switch. Finally, the experimental results were given to demonstrate the circuit performance and to verify the feasibility of the proposed converter.

Analysis and implementation of a soft-switching converter with reduced switch count

This study presents a reduced switch dual-converter to implement the features of zero-voltage switching (ZVS), load current sharing, high output current and low output ripple current. There are two converter modules in the proposed converter. These two modules share the same power switches and provide the balance load current. The active-clamping circuit is used to realise the ZVS turn-on such that the switching losses on power switches are reduced. The current output rectifier is adopted in the output side to realise the higher output current with reduced ripple current such that the sizes of the output chokes and capacitor are reduced. Compared with the conventional ZVS parallel-connected converter with four power switches, only two switches are used in the proposed converter to accomplish parallel operation. Thus, the proposed converter has less circuit components. Finally, the experimental results based on a laboratory prototype (12 V/50 A) are provided to demonstrate the effectiveness of the proposed converter.

Soft switching active-clamped dual-series resonant converter

A soft switching active-clamp dual-series resonant converter is proposed here. Two small transformers are used in the proposed topology to provide more load power. An active-clamp circuit is used to absorb the energy stored in the leakage inductor of transformer, to clamp voltage stresses across switches and to realise the zero-voltage switching turn-on of switches in order to alleviate the switching losses. In order to remove the reverse-recovery problem on output diodes, the zero-current switching turn-off is realised by choosing the proper angle frequency on the secondary side. Analysis of mode operation, design considerations and experimental results of the proposed zero-voltage zero-current switching (ZVZCS) converter are described in detail. Finally, a 200 W ZVZCS prototype treated under Vin=48 V, Vo=200 V is implemented to verify the practicability of the proposed converter.