Output Voltage Doubler Research Articles

A Novel High-Voltage-Gain Quasi-Resonant DC–DC Converter With Active-Clamp and Switched-Capacitor Techniques

We propose an isolated high-voltage-gain quasi-resonant dc-dc converter with a bi-functional circuit for the renewable energy applications. The proposed converter adopts an interleaved connection in the primary side, reducing input current ripple, and includes the bi-functional circuit operating as the switched-capacitor cells and two active-clamped circuits simultaneously. The converter realizes high voltage conversion ratio without using extreme duty ratio, and the voltage spike due to the leakage inductance of the isolation transformer is clamped. In addition, an output voltage doubler in the secondary side comprises a series resonant circuit and then obtains zero current switching (ZCS) turn-off of rectifying diodes; the diode reverse recovery problems are also alleviated. A 320W laboratory prototype that operates at input of 26 V-34 V and output of 400 V is fabricated to verify the effectiveness of the proposed converter.

Highly Efficient Bridgeless Dual-Mode Resonant Single Power-Conversion AC–DC Converter

This paper presents a bridgeless dual-mode single power-conversion ac–dc converter that can achieve a high conversion efficiency. By adopting a bidirectional switch, we remove a full-bridge diode rectifier from the grid side of the proposed converter, and thereby, reduce the number of components and the primary-side conduction loss. To adapt the converter to 1-kW power applications with a bidirectional switch, we used a series-resonant circuit in the output voltage doubler on the secondary side. The series-resonant circuit also provides zero-current switching turn- off at the output diode, and thereby, reduces the reverse-recovery loss. To attain medium–high power capability with an appropriate transformer, the proposed converter operates in both discontinuous conduction mode and continuous conduction mode. The operation principle of the converter is presented and analyzed. By using the dual-mode control algorithm, the proposed converter achieves a high power factor of 0.994 and maximum efficiency of 97.3 $\%$ . Experimental results for a prototype 1-kW ac–dc converter verify these characteristics.

High Step-Up Resonant DC–DC Converter With Ripple-Free Input Current for Renewable Energy Systems

In this paper, we propose a high step-up resonant dc–dc converter with ripple-free input current for renewable energy systems. We use an input-current doubler and a switching mechanism employed at an output-voltage doubler to achieve high step-up voltage gain without having to use a transformer with high turns ratio. An active-clamp circuit installed on the primary side suppresses the surge voltage at the switch components and recycles the energy stored in the leakage inductance. A resonance that occurs at the secondary side of the converter is used to reduce the turn- off current and switching loss significantly, and to achieve high power conversion efficiency. The input-current ripple declines to zero theoretically because the duty cycle of the primary-side switches is always set to 0.5 regardless of the input voltages and load variations. The circuit operations, steady-state analysis, and design guideline of the proposed converter are also presented. A 600-W prototype converter has been fabricated to demonstrate the performance of the proposed converter.

New flatness‐based control of a high‐voltage generator for medical X‐ray applications

This study presents a new flatness-based control scheme for the quantum series–parallel LCC-type resonant converter with output voltage doubler for high-voltage pulse applications, like medical X-ray imaging. Based on a previously derived continuous time model of the system, a flat output of the system model is shown. Moreover, an optimised trajectory planning algorithm with limited resonant current and the controller design are addressed. Details on the experimental set-up and the real-time controller implementation on an FPGA are given. Measurement results show the accuracy of the presented control method.

A Novel Control Algorithm for Conversion ofAC-DC with Improved Power Factor andEfficiency

A Single power-conversion ac–dc converter with high power factor and high efficiency. The proposed converter is derived by integrating a full-bridge diode rectifier and a series-resonant active-clamp dc–dc converter. To obtain a high power factor without a power factor correction circuit, this paper proposes a novel control algorithm. The proposed converter provides single power-conversion by using the novel control algorithm for both power factor correction and output control. Also, the active-clamp circuit clamps the surge voltage of switches and recycles the energy stored in the leakage inductance of the transformer. Moreover, it provides zero-voltage turn-on switching of the switches. Also, a series-resonant circuit of the output-voltage doubler removes the reverse-recovery problem of the output diodes. The proposed converter provides maximum power factor 0.995 and maximum efficiency of 95.1% at the full load.

Single Power-Conversion AC--DC Converter With High Power Factor and High Efficiency

This paper proposes a single power-conversion ac-dc converter with high power factor and high efficiency. The proposed converter is derived by integrating a full-bridge diode rectifier and a series-resonant active-clamp dc-dc converter. To obtain a high power factor without a power factor correction circuit, this paper proposes a novel control algorithm. The proposed converter provides single power-conversion by using the novel control algorithm for both power factor correction and output control. Also, the active-clamp circuit clamps the surge voltage of switches and recycles the energy stored in the leakage inductance of the transformer. Moreover, it provides zero-voltage turn-on switching of the switches. Also, a series-resonant circuit of the output-voltage doubler removes the reverse-recovery problem of the output diodes. The proposed converter provides maximum power factor 0.995 and maximum efficiency of 95.1% at the full load. The operation principle of the converter is analyzed and verified. Experimental results for a 400 W ac-dc converter at a constant switching frequency of 50 kHz are obtained to show the performance of the proposed converter.

고역률을 갖는 단일 전력변환 AC-DC 컨버터

This paper proposes a single power-conversion ac-dc converter with a dc-link capacitor-less and high power factor. The proposed converter is derived by integrating a full-bridge diode rectifier and a series-resonant active-clamp dc-dc converter. To obtain a high power factor without a power factor correction circuit, this paper proposes a suitable control algorithm for the proposed converter. The proposed converter provides single power-conversion by using the proposed control algorithm for both power factor correction and output control. Also, the active-clamp circuit clamps the surge voltage of switches and recycles the energy stored in the leakage inductance of the transformer. Moreover, it provides zero-voltage turn-on switching of the switches. Also, a series-resonant circuit of the output-voltage doubler removes the reverse-recovery problem of the output diodes. The proposed converter provides maximum power factor of 0.995 and maximum efficiency of 95.1% at the full-load. The operation principle of the converter is analyzed and verified. Experimental results for a 400W ac-dc converter at a constant switching frequency of 50kHz are obtained to show the performance 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.

Experimental Investigation of High Step-Up DC-DC Converter for Fuel Cell System

This work aims to present experimental investigation of a high step-up DC-DC converter for fuel cell system. The proposed converter comprises of an input-current doubler, an output-voltage doubler, and an active-clamp circuit. The input-current doubler and the output-voltage doubler both provide much higher voltage conversion ratio by using a low turn ratio transformer. The low turn ratio increases the overall efficiency. A series resonant circuit of the output voltage doubler removes the reverse recovery problem of the rectifying diodes. The active-clamp circuit clamps the surge voltage of switches and recycles the energy stored in the leakage inductance of the transformer. Simulation has been carried out for the proposed converter with the help of OrCAD software. Experimental results show that the better performance of the converter is achieved at an input voltage of 30V.

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.

Analysis of two resonant converters with the same converter leg

A new series resonant converter composed of two resonant circuits with the same converter leg is presented to achieve the zero-voltage switching (ZVS) turn-on of power switches at a wide range of input voltage and load conditions and zero-current switching (ZCS) turn-off of rectifier diodes in a low input voltage case. Thus, the switching losses of power switches and reverse recovery current on rectifier diodes are improved. If the minimum dc voltage gain of the proposed converter is properly selected, the output voltage can be regulated at no-load condition. Two resonant converters using the same power switches are operated by the phase shift half-switching cycle. Thus, the current ripple at the input terminal capacitor can be reduced. In order to reduce the current stresses of output diodes, the output sides of two resonant converters are connected in parallel. The root mean square currents on transformer secondary windings, transformer copper losses and thermal losses can be further reduced. The output voltage doubler topology is adopted in the output side such that the voltage stress of rectifier diodes is equal to the output voltage instead of two times the output voltage in the conventional centre-tapped rectifier topology. Based on the resonant behaviour, all switches are turned on at ZVS and rectifier diodes are turned off at ZCS if the switching frequency is less than the series resonant frequency. The laboratory experiments with a 1000 W prototype are provided to verify the effectiveness of the proposed converter.

Simulation analysis on high step-up DC-DC converter for fuel cell system

This paper presents a high step-up DC-DC converter for fuel cell system. The proposed converter comprises of an input-current doubler, an output-voltage doubler, and an active-clamp circuit. The input-current doubler and the output-voltage doubler both provide much higher voltage conversion ratio by using a low turn ratio transformer. The low turns ratio increases the overall efficiency. A series resonant circuit of the output voltage doubler removes the reverse recovery problem of the rectifying diodes. The active-clamp circuit clamps the surge voltage of switches and recycles the energy stored in the leakage inductance of the transformer. The proposed converter has been simulated in OrCAD software. Simulation results proved that based on the transformer design, better performance of the converter can be achieved for any value of input voltage. Key words: Series resonant circuit, active clamp circuit, input-current doubler, output-voltage doubler.

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.

High Step-Up Active-Clamp Converter With Input-Current Doubler and Output-Voltage Doubler for Fuel Cell Power Systems

A high-efficiency high step-up DC-DC converter is proposed for fuel cell power systems. The proposed system consists of an input-current doubler, an output-voltage doubler, and an active-clamp circuit. The input-current doubler and the output-voltage doubler provide a much higher voltage conversion ratio without using a high turns ratio in the transformer and increase the overall efficiency. A series-resonant circuit of the output-voltage doubler removes the reverse-recovery problem of the rectifying diodes. The active-clamp circuit clamps the surge voltage of switches and recycles the energy stored in the leakage inductance of the transformer. The operation principle of the converter is analyzed and verified. A 1 kW prototype is implemented to show the performance of the proposed converter. The prototype achieved a European efficiency of 96% at an input voltage of 30 V.

Design and implementation of an interleaved soft‐switching converter with output voltage doubler

AbstractAn interleaved pulse‐width modulation (PWM) converter with less power switches is presented in this paper. The buck type of active clamp circuit is used to recycle the energy stored in the leakage inductor of a transformer. The zero voltage switching (ZVS) turn‐on of power switches is realized by the resonance during the transition interval of power switches. At the secondary side of transformers, two full‐wave rectifiers with dual‐output configuration are connected in parallel to reduce the current stresses of the secondary windings of transformers. In the proposed converter, power switches can accomplish two functions of the interleaved PWM modulation and active clamp feature at the same time. Therefore, the circuit components in the proposed converter are less than that of the conventional interleaved ZVS forward converter. The operation principle and system analysis of the proposed converter are provided in detail. Experimental results for a 280 W prototype operated at 100 kHz are provided to demonstrate the effectiveness of the proposed converter. Copyright © 2008 John Wiley & Sons, Ltd.

Analysis of voltage doubler ZVS converter

A novel zero voltage switching (ZVS) isolated converter 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. The proposed circuit has no large output inductor such that the adopted circuit has a simpler structure, lower cost and no effective duty loss. Finally experimental results based on a 300 W prototype are provided to verify the effectiveness of the proposed converter.

Active clamp ZVS converter with output voltage doubler

An isolated converter with boost voltage conversion ratio is presented. The active clamp circuit is used to achieve zero voltage switching, release the energy stored in the transformer leakage inductance and limit the voltage stresses on power switches. Compared with the conventional active clamp forward converter, the adopted circuit has no large output filter inductor. Thus, it has features of simpler structure, lower cost and no effective duty loss. Experimental results for a converter with an input voltage of 24 V, an output voltage of 200 V and operating at switching frequency of 73 kHz are provided to verify the effectiveness of the proposed converter.