Analysis of the ZVS two‐switch forward converter with synchronous current doubler rectifier

A soft switching two‐switch forward converter is presented to achieve zero voltage switching (ZVS) turn‐on of switching devices. In the adopted converter, a buck‐boost type of active clamp is connected in parallel with the primary winding of 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 between the transient interval of two main and auxiliary switches is used to achieve ZVS turn‐on of all switches. The current doubler synchronous rectifier is used in the secondary side of transformer for reducing the root mean square value of output inductor current, transformer secondary winding current and output voltage ripple by cancelling the current ripple of two output inductors. First, the circuit configuration and the principles of operation are analyzed in detail. The steady‐state analysis and design consideration are also presented. Finally, experimental results with a laboratory prototype based on a 380 V input and 12 V/30 A output were provided to verify the effectiveness of the proposed converter. Copyright © 2007 John Wiley & Sons, Ltd.     

Analysis and design of a two‐transformer active‐clamping ZVS isolated inverse‐SEPIC converter

This paper presents a two‐transformer active‐clamping zero‐voltage‐switching (ZVS) isolated inverse‐SEPIC converter, which is mainly composed of two active‐clamping ZVS isolated inverse‐SEPIC converters. The proposed converter allows a low‐profile design for liquid crystal display TVs and servers. The presented two‐transformer active‐clamping ZVS isolated inverse‐SEPIC converter can equally share the total load current between two secondaries. Therefore, the output inductor copper loss and the output diode conduction loss can be decreased. Detailed analysis and design of this new two‐transformer active‐clamping ZVS isolated inverse‐SEPIC converter are described. Experimental results are recorded for a prototype converter with an AC input voltage ranging from 85 to 135 V, an output voltage of 12 V and a rated output current of 13.5A, operating at a switching frequency of 65 kHz. Copyright © 2012 John Wiley & Sons, Ltd.     

A soft‐switching high step‐up DC‐DC converter with a single magnetic component

A soft‐switching high step‐up DC‐DC converter with a single magnetic component is presented in this paper. The proposed converter can provide high voltage gain with a relatively low turn ratio of a transformer. Voltage doubler structure is selected for the output stage. Due to this structure, the voltage gain can be increased, and the voltage stresses of output diodes are clamped as the output voltage. Moreover, the output diode currents are controlled by a leakage inductance of a transformer, and the reverse‐recovery loss of the output diodes is significantly reduced. Two power switches in the proposed converter can operate with soft‐switching due to the reflected secondary current. The voltages across the power switches are confined to the clamping capacitor voltage. Steady‐state analysis, simulation, and experimental results for the proposed converter are presented to validate the feasibility and the performance of the proposed converter. Copyright © 2012 John Wiley & Sons, Ltd.     

Analysis,design and implementation of a high‐voltage gain DC‐DC converter

An interleaved DC‐DC converter with soft switching technique is presented. There are two converter modules in the adopted circuit to share the load power. Since the interleaved pulse‐width modulation (PWM) is adopted to control two circuit modules, the ripple currents at input and output sides are naturally reduced. Therefore the input and output capacitances can be reduced. In each circuit module, a conventional boost converter and a voltage doubler configuration with a coupled inductor are connected in series at the output side to achieve high step‐up voltage conversion ratio. Active snubber connected in parallel with boost inductor is adopted to limit voltage stress on active switch and to release the energy stored in the leakage and magnetizing inductances. Since asymmetrical PWM is used to control active switches, the leakage inductance and output capacitance of active switches are resonant in the transition interval. Thus, both active switches can be turned on at zero voltage switching. The resonant inductance and output capacitances at the secondary side of transformer are resonant to achieve zero current switching turn‐off for rectifier diodes. Therefore, the reverse recovery losses of fast recovery diodes are reduced. Finally, experiments based on a laboratory prototype rated at 400 W are presented to verify the effectiveness of the proposed converter. Copyright © 2012 John Wiley & Sons, Ltd.     

An active‐clamping zero‐voltage‐switching flyback converter with integrated transformer

This paper proposes an active‐clamping flyback converter using an integrated transformer. The proposed converter is composed of two active‐clamp flyback converters. The presented converter can balance the total load current between secondary sides of two transformers so that the rectifier diode conduction loss is reduced. Also, the main switch of one converter is the auxiliary switch for the other converter, so that only two switches are required and both can achieve zero‐voltage‐switching operation. The two transformers are integrated into one magnetic core; therefore, the volume and copper loss of transformer can be reduced. Detailed analysis and design of this integrated magnetic active‐clamping flyback converter are described. Experimental results are recorded for a prototype converter with an AC input voltage ranging from 85 to 135 V, an output voltage of 24 V and an output current of 5 A, operating at a switching frequency of 100 kHz. Copyright © 2014 John Wiley & Sons, Ltd.     

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

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.     

Analysis and Implementation of an Interleaved ZVS Converter with High Input Voltage

An interleaved half‐bridge converter is presented for high input voltage application. The features of the proposed converter are zero voltage switching (ZVS) turn‐on for all active switches, ripple current reduction at output side, load current sharing and load voltage regulation. Two half‐bridge converters connected in series and two split capacitors are used to limit the voltage stress of each power switch at one‐half of input DC bus voltage. Thus, active switches with low voltage stress can be used at high input voltage application. On the other hand, the output sides of two half‐bridge converters are connected in parallel to share the load current and reduce the current stresses of the secondary windings and the rectifier diodes. Since two half‐bridge converters are operated with interleaved pulse‐width modulation (PWM), the output ripple current can partially cancel each other such that the resultant ripple current at output side is reduced and the size of output inductors can be reduced. In each half‐bridge converter, asymmetrical PWM scheme is used to regulate the output voltage. Based on the resonant behavior by the output capacitance of MOSFETs and the leakage inductance (or external inductance) of transformers, active switches can be turned on at ZVS during the transition interval. Thus, the switching losses of power MOSFETs are reduced. The proposed converter can be applied for high input voltage applications such as three‐phase 380‐V utility system. Finally, experiments based on a laboratory prototype with 960‐W rated power are provided to demonstrate the performance of proposed converter. Copyright © 2012 John Wiley & Sons, Ltd.     

A ZVS‐ZCS phase shift full bridge DC‐DC converter with secondary‐side control for battery charging applications

The output power requirement of battery charging circuits can vary in a wide range, hence making the use of conventional phase shift full bridge DC‐DC converters infeasible because of poor light load efficiency. In this paper, a new ZVS‐ZCS phase shift full bridge topology with secondary‐side active control has been presented for battery charging applications. The proposed circuit uses 2 extra switches in series with the secondary‐side rectifier diodes, operating with phase shift PWM. With the assistance of transformer's magnetizing inductance, the proposed converter maintains zero voltage switching (ZVS) of the primary‐side switches over the entire load range. The secondary‐side switches regulate the output voltage/current and perform zero current switching (ZCS) independent of the amount of load current. The proposed converter exhibits a significantly better light load efficiency as compared with the conventional phase shift full bridge DC‐DC converter. The performance of the proposed converter has been analyzed on a 1‐kW hardware prototype, and experimental results have been included.     

Hybrid DC–DC converter with high efficiency,wide ZVS range,and less output inductance

In this paper, a new soft switching direct current (DC)–DC converter with low circulating current, wide zero voltage switching range, and reduced output inductor is presented for electric vehicle or plug‐in hybrid electric vehicle battery charger application. The proposed high‐frequency link DC–DC converter includes two resonant circuits and one full‐bridge phase‐shift pulse‐width modulation circuit with shared power switches in leading and lagging legs. Series resonant converters are operated at fixed switching frequency to extend the zero voltage switching range of power switches. Passive snubber circuit using one clamp capacitor and two rectifier diodes at the secondary side is adopted to reduce the primary current of full‐bridge converter to zero during the freewheeling interval. Hence, the circulating current on the primary side is eliminated in the proposed converter. In the same time, the voltage across the output inductor is also decreased so that the output inductance can be reduced compared with the output inductance in conventional full‐bridge converter. Finally, experiments are presented for a 1.33‐kW prototype circuit converting 380 V input to an output voltage of 300–420 V/3.5 A for battery charger applications. Copyright © 2015 John Wiley & Sons, Ltd.     

Series resonant ZCS‐PFM DC‐DC power converter with high‐frequency high‐voltage transformer link for high‐power magnetron drive

This paper presents a single lossless inductive snubber‐assisted ZCS‐PFM series resonant DC‐DC power converter with a high‐frequency high‐voltage transformer link for industrial‐use high‐power magnetron drive. The current flowing through the active power switches rises gradually at a turned‐on transient state with the aid of a single lossless snubber inductor, and ZCS turn‐on commutation based on overlapping current can be achieved via the wide range pulse frequency modulation control scheme. The high‐frequency high‐voltage transformer primary side resonant current always becomes continuous operation mode, by electromagnetic loose coupling design of the high‐frequency high‐voltage transformer and the magnetizing inductance of the high‐frequency high‐voltage transformer. As a result, this high‐voltage power converter circuit for the magnetron can achieve a complete zero current soft switching under the condition of broad width gate voltage signals. Furthermore, this high‐voltage DC‐DC power converter circuit can regulate the output power from zero to full over audible frequency range via the two resonant frequency circuit design. Its operating performances are evaluated and discussed on the basis of the power loss analysis simulation and the experimental results from a practical point of view. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 153(3): 79–87, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20126     

Implementation of a Soft Switching Converter with High Input Voltage

This paper presents an interleaved zero voltage switching (ZVS) DC/DC converter with high input voltage applications. In order to reduce the voltage stress of MOSFETs, two half‐bridge zeta converters are connected in series at high voltage side. Thus, the voltage stress of MOSFETs can be clamped at one‐half of input voltage. Asymmetric pulse‐width modulation (APWM) is adopted to control power switches. With the resonant behavior by the leakage inductance of transformer and the output capacitance of MOSFET at the transition interval, MOSFETs can be turned on at ZVS. For each half‐bridge zeta converter, two series transformers are connected in series at the primary side and in parallel at the secondary side in order to reduce the current stress of secondary windings for high load current applications. Interleaved PWM scheme is used to control two half‐bridge converters in order to reduce the size of output filter inductor and capacitor due to the partial ripple current cancellation. Experimental results, taken from a laboratory prototype rated at 1 kW, are presented to demonstrate the converter performance. Copyright © 2012 John Wiley & Sons, Ltd.     

Two‐switch flyback PWM DC‐DC converter in continuous‐conduction mode

The two‐switch flyback DC‐DC converter is an extended version of the conventional single‐switch flyback converter. An additional switch and two clamping diodes serve as a simple, but an effective way to limit the switch overvoltages, which occur in the conventional single‐switch flyback converter due to the ringing of the resonant circuit formed by the transformer leakage inductance and the transistor output capacitance. The clamping diodes in the two‐switch flyback topology clamp the maximum voltage across each switch equal to the DC input voltage. This paper presents a detailed steady‐state analysis and design procedure of the diode‐clamped two‐switch flyback converter operated in continuous‐conduction mode (CCM). The power loss in each component of the two‐switch flyback converter is compared with those of the single‐switch flyback converters with and without RCD clamp, and is presented in a tabular form. The two‐switch flyback converter was bread‐boarded to validate the theoretical analysis. Experimental results from a 10 V/30 W, 100 kHz laboratory prototype verified that the maximum switch voltage is limited to the DC input voltage. Copyright © 2010 John Wiley & Sons, Ltd.     

LLC resonant DC–DC converter with series‐connected primary windings of transformer

This paper proposes a zero‐voltage switching (ZVS) LLC resonant step up DC–DC converter with series‐connected primary windings of the transformer. The series resonant inverter in the proposed topology has two power switches (MOSFETs), two resonant capacitors, two resonant inductors, and only one transformer with center‐tapped primary windings. The power switches are connected in the form of a half‐bridge network. Resonant capacitors and inductors along with the primary windings of the transformer form two series resonant circuits. The series resonant circuits are fed alternately by operating the power switches with an interleaved half switching cycle. The secondary winding of transformer is connected to a bridge rectifier circuit to rectify the output voltage. The converter operates within a narrow frequency range below the resonance frequency to achieve ZVS, and its output power is regulated by pulse frequency modulation. The converter has lower conduction and switching losses and therefore higher efficiency. The experimental results of a 500‐W prototype of proposed converter are presented. The results confirm the good operation and performance of the converter. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Isolated high voltage‐boosting converter derived from forward converter

A novel isolated high voltage‐boosting converter, derived from the traditional forward converter, is presented in this paper. As compared with the traditional forward converter, the demagnetizing winding of the transformer in the proposed converter is used not only to demagnetize but also to improve the voltage conversion ratio. Therefore, the duty cycle is not limited, and the utilization of the transformer, also called coupled inductor, can be increased also. Furthermore, the proposed converter maintains the advantage of possessing a non‐pulsating output current, leading to a small output voltage ripple. Moreover, by applying one additional voltage‐boosting winding to the transformer, the voltage conversion ratio can be significantly improved. In addition, an active clamp circuit is employed in the proposed converter to reduce the voltage stress of the main switch, caused by the leakage inductance in the transformer, and the switches can achieve zero‐voltage switching. Finally, the analysis of operating principles, choice of the turns, turns ratio, core size, and each wire size of the coupled inductor are described in detail, and the experimental results with a prototype with 12‐V input voltage, 100‐V output voltage, and 100‐W output power are provided to verify the feasibility and effectiveness of the proposed converter. Copyright © 2015 John Wiley & Sons, Ltd.     

Two‐switch flyback PWM DC–DC converter in discontinuous‐conduction mode

The two‐switch flyback DC–DC converter is an extended version of the conventional single‐switch flyback converter. An additional switch and two clamping diodes serve as a simple, but an effective way to limit the switch overvoltages, which occur in the conventional single‐switch flyback converter due to the ringing of the resonant circuit formed by the transformer leakage inductance and the transistor output capacitance. The clamping diodes in the two‐switch flyback topology clamp the maximum voltage across each switch equal to the DC input voltage. This paper presents a detailed analysis and design procedure of the diode‐clamped two‐switch flyback converter operated in discontinuous‐conduction mode (DCM). A comparison of power losses of the two‐switch and the single‐switch flyback converters is given. The two‐switch flyback converter was bread‐boarded to validate the theoretical analysis. Experimental results from a 20‐V/30‐W, 100‐kHz laboratory prototype verified that the maximum switch voltage is limited to the DC input voltage. Copyright © 2010 John Wiley & Sons, Ltd.     

Soft switching DC/DC converter with high voltage gain and less current ripple

A new soft switching three‐level converter with two DC/DC circuits in the primary side and current double rectifiers in the secondary side is presented to realize the zero‐voltage switching operation, reduce the transformer secondary winding turns and the output current ripple, and lessen the voltage rating of rectifier diodes. Two DC/DC pulse‐width modulation circuits sharing same power switches with interleaved half switching cycle are adopted in the proposed converter to reduce the current rating of transformer primary windings. Two inductors and four diodes are adopted in the secondary side to achieve current double rectifier, reduce output ripple current, and decrease the transformer secondary winding turns. Based on the pulse‐width modulation scheme, the power switchers can be turned on at zero‐voltage switching operation. Laboratory experiments with a 1.44 kW prototype are provided to verify the theoretical analysis. Copyright © 2016 John Wiley & Sons, Ltd.     

Series resonant high‐voltage DC–DC converter with reduced component count

This paper proposes a novel zero‐current‐switching series resonant high‐voltage DC–DC converter with reduced component count. The series resonant inverter in the proposed topology has two power switches (insulated‐gate bipolar transistors, IGBTs), two resonant capacitors, and only one high‐voltage transformer (HVT) with center‐tapped primary windings. The power switches are connected in the form of a half‐bridge network. The leakage inductances of the transformer's primary windings together with the resonant capacitors form two series resonant circuits. The series resonant circuits are fed alternately by operating the power switches with interleaved half switching cycle. The secondary winding of the HVT is connected to a bridge rectifier circuit to rectify the secondary voltage. The converter operates in the discontinuous conduction mode (DCM) and its output voltage is regulated by pulse frequency modulation. Therefore, all the power switches turn on and off at the zero‐current switching condition. The main features of the proposed converter are its lower core loss, lower cost, and smaller size compared to previously proposed double series resonant high voltage DC–DC converters. The experimental results of a 130‐W prototype of the proposed converter are presented. The results confirm the excellent operation and performance of the converter. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Analysis and design of an active‐clamping zero‐voltage‐switching isolated inverse‐SEPIC converter

This paper presents an active‐clamping zero‐voltage‐switching (ZVS) isolated inverse‐SEPIC converter. The high voltage spikes when turning off the switches are eliminated. The energies stored in the parasitic elements can be recycled to achieve the ZVS of switches. Therefore, the conversion efficiency increases substantially, yet with a reduced circuit cost. Detailed analysis and design of the proposed topology are described. Experimental results are recorded for a prototype converter with a DC input voltage ranging from 130 to 180 V, an output voltage of 12 V and a rated output power of 120 W, operating at a switching frequency of 65 kHz. The average active‐mode efficiency is above 88%. Copyright © 2010 John Wiley & Sons, Ltd.     

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

An 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.     

Implementation of an interleaved pulse‐width modulation converter for renewable energy conversion

This paper presents an interleaved soft switching converter to achieve the features of zero voltage switching (ZVS) turn‐on for power switches, zero current switching turn‐off for rectifier diodes at full load, less transformer secondary winding with full‐wave diode rectifier topology, and balance primary currents with series connection of the transformer secondary windings. Two circuit modules are adopted in the proposed circuit, and they are operated with an interleaved pulse‐width modulation. Thus, ripple currents at the input and output sides are reduced. In each module, two ZVS converters using the same switches are operated with interleaved half switching cycle. The secondary windings of transformers are connected in series in order to ensure that the primary side currents are balanced. The full‐wave diode rectifier topology is used on the output side such that the voltage stress of rectifier diodes equals output voltage, rather than being two times the output voltage as in a conventional center‐tapped rectifier topology. Laboratory experiments with a 1000‐W prototype are provided to describe the effectiveness of the proposed converter. Copyright © 2011 John Wiley & Sons, Ltd.