Zero-voltage Switching Converter Research Articles

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.

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 of a new ZVS converter with output voltage doubler

A novel zero voltage switching (ZVS) converter with output voltage doubler is presented. The output voltage doubler is used on the output side to achieve the boost type of voltage conversion ratio. Active-clamping technique is adopted to realise the ZVS turn-on of all switches, release the energy stored in the transformer leakage inductance and limit the voltage stresses on power switches. The ZVS function is achieved at the commutation stage of two complementary switches. The proposed circuit has no large output inductor such that the adopted circuit has a simpler structure, lower cost and no effective duty loss. The voltage stresses on output diodes are clamped at the output voltage. The circuit configuration, operation principles and design consideration are presented. Finally, experimental results based on a 300 W prototype are provided to verify the effectiveness of the proposed converter.

Implementation of a ZVS interleaved converter with two transformers

This paper presents an interleaved converter with the feature of zero voltage switching (ZVS). Two buck-type converters connected in parallel have the same switching devices and operate under the interleaved pulse-width modulation (PWM). Thus the output ripple current in the proposed circuit is less than that in the conventional forward converter. Thus the size of the output choke and capacitor is reduced. Only two switches are used in the proposed circuit instead of four switches in the conventional parallel ZVS converter. Therefore the circuit components in the proposed converter are reduced. ZVS turn-on is achieved during the commutation stage of two complementary switches such that the switching losses thermal stresses on the semiconductors are reduced. Experiments based on a 330 W prototype are provided to verify the theoretical analysis and the effectiveness of the proposed converter.

Active-clamp ZVS converter with step-up voltage conversion ratio

This article presents the circuit implementation and design considerations of a zero voltage switching (ZVS) converter with voltage step-up for battery-based applications. An active-clamp circuit including one auxiliary switch and one clamp capacitor is connected in parallel with the main switch to allow resonant behaviour by the output capacitances of switches and transformer leakage inductance during the transition interval. Thus, the ZVS turn-on of switches can be achieved. The switching losses and thermal stresses of the semiconductors are reduced. The circuit configuration, operation principle and design considerations of the converter are discussed in detail. Finally, experiments conducted on a laboratory prototype rated at 200 W are provided to verify the theoretical analysis and the effectiveness of the proposed converter.

Novel Half-Bridge Inductive DC–DC Isolated Converters for Fuel Cell Applications

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> This paper proposes a new class of converters based on the inductive input converters for the design of a power electronic interface for fuel cell (FC) applications. After studying the half-bridge structure, two soft-switching dc–dc converters are analyzed: one operating in zero-voltage-switching (ZVS) mode and the other in zero-current-switching (ZCS) mode. The ZVS converter can overcome the drawbacks of the original structure but is more complicated. The ZCS converter cannot operate at duty cycles below 0.5, but is simpler and more suitable for FC applications. Flexible choice of components, low losses, high efficiency, and modular converter possibility are all interesting characteristics of these converters. Their operation principle and characteristics are presented in this paper. Experimental results on 2 kW converters of each structure validate the theoretical analysis. </para>

Analysis and implementation of a zero voltage switching bi-forward converter

The system analysis and the circuit implementation of a zero voltage switching (ZVS) bi-forward converter is presented here. Two forward converters are adopted in the circuit with the active clamp technique to achieve interleaved PWM operation and load current sharing. Only two switches are used in the proposed converter instead of the four switches in the conventional parallel ZVS converter. Thus, the circuit components and conduction losses are reduced in the proposed converter. In the proposed circuit, the PWM signals of two switches are complementary to each other with a small delay time in order to realise the ZVS turn-on of the switches at the transition interval. Thus, the switching losses and thermal stresses of semiconductors are reduced since the interleaved PWM scheme is used to control two forward converters such that the output ripple currents are partially cancelled out. The sizes of the output chokes and capacitor are reduced. Experiments based on a 300 W prototype are provided to verify the theoretical analysis and the effectiveness of the proposed converter.

Novel interleaved ZVS converter with ripple current cancellation

AbstractThis paper presents a zero voltage switching (ZVS) converter with interleaved pulse‐width modulation scheme. An active clamp circuit is adopted in the proposed converter to recycle the energy stored in the leakage inductor of the transformer and reduce the voltage stress of the main power switch in the converter. The ZVS feature of switches can be achieved due to the resonance during the transition interval of two power switches. Two full‐wave rectifiers with ripple current cancellation are connected in parallel at the output side to reduce the current stress of the secondary winding of transformers. Instead of the conventional interleaved forward converter, power switches in the proposed converter can perform the functions of both forward converter and active clamp at the same time. Therefore, the circuit components in the power circuit are less than that of in the conventional interleaved forward converter. The operation principle and system analysis of the proposed converter are provided. Some experimental results for a 240 W (12 V/20 A) prototype are provided to demonstrate the effectiveness of the proposed converter. Copyright © 2008 John Wiley &amp; Sons, Ltd.

Interleaved ZVS Converter With Ripple-Current Cancellation

In this paper, an interleaved soft-switching converter with ripple-current cancellation is presented to achieve zero- voltage-switching (ZVS) turn-on and load current sharing. In order to achieve ZVS turn-on, an active snubber is connected in parallel with the primary winding of the transformer. The energy stored in the transformer leakage inductance and magnetizing inductance can be recovered so that the peak voltage stress of switching devices is limited. The resonance at the transition interval is used to realize ZVS turn-on of all switches. In order to achieve three-level pulsewidth-modulation (PWM) scheme, an addition fast-recovery diode is used in the converter. Three-level PWM scheme can reduce the ac ripple current on the output inductor such that the output inductor can be reduced. The current-doubler rectifier is adopted in the secondary side of the transformer to reduce the transformer secondary-winding current and output voltage ripple by canceling the current ripple of two output inductors. The output voltage is controlled at the desired value using the interleaved PWM scheme. These features make the proposed converter suitable for the dc-dc converter with high output current. The operation principles, steady state analysis, and design equations of the proposed converter are provided in detail. Finally, experiments based on a 600-W (12 V/50 A) prototype are provided to verify the effectiveness and feasibility of the proposed converter.

Analysis, Design, and Implementation of a Parallel ZVS Converter

A soft-switching converter is presented in this paper to achieve a zero-voltage-switching (ZVS) turn on for all switches. Two half-bridge converters with asymmetric pulsewidth-modulation scheme are connected in parallel to control the output voltage at the desired value and achieve load-current sharing. Based on the output capacitance of power switches and the resonant inductance, including the external inductance and the transformer leakage inductance, the resonance can be achieved at the transition interval of power switches. Therefore, the ZVS turn on of power switches can be realized. The peak voltage of the power switches is limited to input dc voltage. The center-tapped rectifier is adopted at the transformer secondary side to achieve a full-wave rectification. Operation principles, steady-state analysis, and design equations of the proposed converter are discussed in detail. Finally, experimental results based on a 240-W prototype are provided to verify the performance and the feasibility of the proposed converter.

Interleaved zero voltage switching forward converter with less switches

An interleaved zero voltage switching (ZVS) forward converter with less switches is presented. Two forward converters with active clamp technique are adopted in the circuit to achieve interleaved pulse-width-modulation (PWM) operation and load current sharing. Only two switches are used in the converter instead of four as in the conventional parallel ZVS converter. Experiments verified the theoretical analysis and the effectiveness of the converter.

Analysis and Derivations for a Family ZVS Converter Based on a New Active Clamp ZVS Cell

A new zero voltage switching (ZVS) cell is proposed based on the active clamping technique. With a small clamping diode in the cell, the voltage ringing caused by the auxiliary inductor and the parasitic capacitance of the diode is eliminated, and therefore, the circulating loss is minimized. A new ZVS boost converter is presented and analyzed in detail to demonstrate the operating principle of the new ZVS cell. A new family of ZVS dc-dc converters can be derived based on the proposed ZVS cell and typical nonisolated dc-dc converters. A 500 W/190 kHz ZVS boost prototype is made to verify the analysis.

Analysis of a Zero-Voltage Switching Converter With Two Transformers

This brief presents an active-clamp zero-voltage switching converter. Two transformers connected in series are used, and each transformer can be operated as an inductor or a transformer. No output inductor is needed. An active-clamp circuit is used to recycle the energy stored in the transformer leakage. The system analysis, operation principles, and design equations of the proposed converter are provided. Experiments based on a laboratory prototype are also provided to confirm the converter performance

Implementation of the ZVS converter with synchronous rectifier

The paper presents the system analysis and circuit design of a half-bridge zero-voltage-switching (ZVS) flyback converter with synchronous rectifier. The leakage inductance and output capacitance of active switches are used to realise ZVS operation during the transition state between two switches. The switching power loss of active switches can be reduced to a minimum due to the ZVS operation such that the high-efficiency circuit can be achieved. The circuit-operation principle, mathematical analysis and design example of a half-bridge ZVS flyback converter with synchronous rectifier are explained and analysed. The synchronous rectifier is used at the transformer-secondary side to reduce further the conduction loss and to increase the circuit efficiency. Finally the experimental results from a 24 V/7 A output load with 100 kHz switching-frequency prototype circuit are provided to verify the theoretical analysis.

A Leakage-Inductance-Based ZVS Two-Inductor Boost Converter With Integrated Magnetics

A two-inductor boost converter topology has conduction loss and transformer utilization advantages in converting low-voltage higher current inputs to high output voltages. In this letter, a new zero-voltage switching (ZVS) two-inductor boost converter with integrated magnetics is proposed. In the new topology, the two current source inductors, a resonant inductor and a two-winding transformer, are integrated into one single magnetic core with three windings. Two windings simultaneously perform the functions of the current source inductors and the transformer primary. The transformer leakage inductance forms the resonant inductance. This leads to a much more compact converter design with a significant reduction in the number of core and winding components. A theoretical analysis establishes the operating point of the ZVS converter. Both of the theoretical and experimental waveforms, including flux waveforms for the legs of the integrated core structure, are presented at the end of the letter.

A New Family of Full-Bridge ZVS Converters

A family of soft-switched, full-bridge (FB) pulse-width-modulated (PWM) converters that feature zero-voltage-switching (ZVS) of all bridge switches over a wide range of input voltage and output load with minimal duty cycle loss and circulating current is described. The ZVS of primary switches is achieved by employing two magnetic components whose volt-second products change in the opposite directions with a change of phase shift between the two bridge legs. One magnetic component is a transformer while the other magnetic component is either a coupled inductor or a single-winding inductor. The transformer is used to provide isolated output(s), whereas the inductor is used to store energy for ZVS.

Nonresonant and resonant coupled zero voltage switching converters

Two zero-voltage switching power converters with nonresonant and resonant coupling are presented. These are high-order multiple resonant converters in which the circuit modes associated with the converter operation may have different resonant frequencies. The steady-state responses of these converters are derived in terms of state-plane diagrams by using proper state variable transformations. It is shown that the converters have all the desirable features for high-frequency applications and overcome the drawback of load-range limitation of zero-voltage switching associated with the conventional class-E converter.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>