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.     

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     

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.     

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.     

Novel current‐source multilevel inverter driven by single gate drive power supply

This paper proposes a novel current‐source multilevel inverter, which is based on a current‐source half‐bridge topology. Multilevel inverters are effective for reducing harmonic distortion in the output voltage and the output current. However, the multilevel inverters require many gate drive power supplies to drive switching devices. The gate drive circuits using a bootstrap circuit and a pulse transformer can reduce the number of the gate drive power supplies, but the pulse width of the output PWM waveform is limited. Furthermore, high‐speed power switching devices are indispensable to create a high‐frequency power converter, but various problems, such as high‐frequency noise, arise due to the high dv/dt rate, especially in high‐side switching devices. The proposed current‐source multilevel inverter is composed of a common emitter topology for all switching devices. Therefore, it is possible to operate it with a single power supply for the gate drive circuit, which allows stabilizing the potential level of all the drive circuits. In this paper, the effectiveness of the proposed circuit is verified through experimental results. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 166(2): 88–95, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20475     

Pulse current regenerative resonant snubber‐assisted two‐switch flyback‐type ZVS PWM DC‐DC converter

In this paper, a two‐switch high‐frequency flyback transformer‐type zero voltage soft‐switching PWM DC‐DC converter using IGBTs is proposed. Effective applications for this power converter can be found in auxiliary power supplies of rolling stock transportation and electric vehicles. This power converter is basically composed of two active power switches and a flyback high‐frequency transformer. In addition to these, two passive lossless snubbers with power regeneration loops for energy recovery, consisting of a three‐winding auxiliary high‐frequency transformer, auxiliary capacitors and diodes are introduced to achieve zero voltage soft switching from light to full load conditions. Furthermore, this power converter has some advantages such as low cost circuit configuration, simple control scheme, and high efficiency. Its operating principle is described and to determine circuit parameters, some practical design considerations are discussed. The effectiveness of the proposed power converter is evaluated and compared with the hard switching PWM DC‐DC converter from an experimental point of view, and the comparative electromagnetic conduction and radiation noise characteristics of both DC‐DC power converter circuits are also depicted. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 152(3): 74–81, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20081     

A novel prototype of auxiliary edge resonant bridge leg link snubber‐assisted soft‐switching sine‐wave PWM inverter

This paper proposes a new circuit topology of the three‐phase soft‐switching PWM inverter and PFC converter using IGBT power modules, which has the improved active auxiliary switch and edge resonant bridge leg‐commutation‐link soft‐switching snubber circuit with pulse current regenerative feedback loop as compared with the typical auxiliary resonant pole snubber discussed previously. This three‐phase soft‐switching PWM double converter is more suitable and acceptable for a large‐capacity uninterruptible power supply, PFC converter, utility‐interactive bidirectional converter, and so forth. In this paper, the soft‐switching operation and optimum circuit design of the novel type active auxiliary edge resonant bridge leg commutation link snubber treated here are described for high‐power applications. Both the main active power switches and the auxiliary active power switches achieve soft switching under the principles of ZVS or ZCS in this three‐phase inverter switching. This three‐phase soft‐switching commutation scheme can effectively minimize the switching surge‐related electromagnetic noise and the switching power losses of the power semiconductor devices; IGBTs and modules used here. This three‐phase inverter and rectifier coupled double converter system does not need any sensing circuit and its peripheral logic control circuits to detect the voltage or the current and does not require any unwanted chemical electrolytic capacitor to make the neutral point of the DC power supply voltage source. The performances of this power conditioner are proved on the basis of the experimental and simulation results. Because the power semiconductor switches (IGBT module packages) have a trade‐off relation in the switching fall time and tail current interval characteristics as well as the conductive saturation voltage characteristics, this three‐phase soft‐switching PWM double converter can improve actual efficiency in the output power ranges with a trench gate controlled MOS power semiconductor device which is much improved regarding low saturation voltage. The effectiveness of this is verified from a practical point of view. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 155(4): 64–76, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20207     

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.     

基于GaN器件大功率双向DC/DC变换器的设计与仿真

介绍了一种新的高功率双向隔离式DC/DC变换器作为高功率转换系统的主要电路.DC/DC变换器使用基于氮化镓(GaN)的功率开关器件.对10 kW GaN大功率DC/DC变换器的拓扑结构进行了优化、参数化和分析,并通过仿真和实验验证了其有效性.它由使用新型的GaN晶体管组成的两个单相全桥电路、两个输入/输出电感和一个高频...     

ZVS DC/DC converter with series half‐bridge legs for high voltage application

This paper presents a new DC/DC converter with series half‐bridge legs for high voltage application. Two half‐bridge legs connected in series and two split capacitors are used in the proposed circuit to limit the voltage stress of each active switch at one‐half of input voltage. Thus, active switches with low voltage stress can be used at high DC bus application. In the proposed converter, two circuit modules are operated with an interleaved pulse‐width modulation scheme to reduce the input and output ripple currents and to achieve load current sharing. In each circuit module, two resonant tanks are operated with phase‐shift one‐half of switching cycle such that the frequency of the input current is twice the frequency of the resonant inductor current. Based on the resonant behavior, all MOSFETs are turned on at zero voltage switching with the wide ranges of input voltage and load conditions. The rectifier diodes can be turned off at zero current switching if the switching frequency is less than the series resonant frequency. Thus, the switching losses on power semiconductors 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 © 2011 John Wiley & Sons, Ltd.     

A half‐bridge resonant DC/DC converter with satisfactory soft‐switching characteristics

In this paper, a half‐bridge resonant DC/DC converter with constant output voltage is proposed, which possesses good soft‐switching characteristics. At rated operating point, the switches can operate almost without switching‐on and off losses. Further, at whole working range, both zero‐voltage‐switching mode of switches and zero‐current‐switching mode of diodes are maintained. Thus, the converter can achieve a high efficiency. Experimental results verify the low switching losses and high efficiency characteristics based on a 200 W prototype. System efficiency is as high as 96% and always above 90% when output power changes from 100% to 20%. Copyright © 2016 John Wiley & Sons, Ltd.     

Analysis and design of a two‐transformer active‐clamping forward converter with parallel‐connected current doubler rectifiers

A new two‐transformer active‐clamping forward converter with parallel‐connected current doubler rectifiers (CDRs) is proposed in this paper. The presented DC–DC converter is mainly composed of two active‐clamping forward converters with secondary CDRs. Only two switches are required and each one is the auxiliary switch for the other. The circuit complexity and cost are thus reduced. The leakage inductance of the transformer or an additional resonant inductance is employed to achieve zero‐voltage‐switching (ZVS) during the dead times. Two CDRs at the secondary side are connected in parallel to reduce the current stresses of the secondary windings and the ripple current at the output side. Accordingly, the smaller output chokes and capacitors decrease the converter volume and increase the power density. Detailed analysis and design of the presented two‐transformer active‐clamping forward converter are described. Experimental results are recorded for a prototype converter with a DC input voltage of 130??180V, an output voltage of 5 V and an output current of 40 A, operating at a switching frequency of 100 kHz. Copyright © 2010 John Wiley & Sons, Ltd.     

A 6.6‐kV transformerless cascade PWM STATCOM. Experimental verification by a three‐phase 200‐V, 10‐kVa laboratory system

This paper deals with a 6.6‐kV transformerless STATCOM cascading multiple single‐phase H‐bridge PWM converters in each phase. The AC voltage of the STATCOM is almost sinusoidal, so that it requires no harmonic filter. Each converter is equipped with a capacitor and a voltage sensor on the DC side, which are electrically isolated from each other. The STATCOM has the capability of self‐starting and voltage‐balancing without any external power supply or equipment. Experiments using a three‐phase 200‐V, 10‐kVA laboratory system, along with computer simulations, are carried out to confirm the viability and effectiveness of the STATCOM. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 170(1): 55–64, 2010; Published online in Wiley InterScience ( www.interscience.wiley. com ). DOI 10.1002/eej.20822     

零电压开关不对称半桥DC／DC变换器

近年来，软开关技术得到广泛的发展与应用，出现不少高效率的电路拓扑，其中不对称半桥就是典型的适用于中低功率的直流变换电路。它充分利用电路本身的分布特性，利用变压器漏感和开关寄生电容的谐振来实现零电压开关，减少了开关的导通损耗。介绍了一种在变压器原边带箝位电路的不对称半桥零电压开关电路。该箝位电路能明显减少输出二板管的反向恢复效应，提高变换器的效率。并对该软开关电路的工作原理和实现方法做了详细的分析，通过一台300W，100kHz的实验样机，证实了该方法的有效性。     

Non‐isolated single‐switch DC–DC converters with extended duty cycle for high step‐down voltage applications

Several new topologies of single‐switch non‐isolated DC–DC converters with wide conversion gain and reduced semiconductor voltage stress are proposed in this paper. Most of the proposed topologies are derived from the conventional inverse of SEPIC (Zeta) converter. The proposed topologies can operate with larger switch duty cycles compared with the existing single switch topologies, hence, making them well suitable for high step‐down voltage conversion applications. With extended duty cycle, the current stress in the active power switch is reduced, leading to a significant improvement of the system losses. Moreover, the active power switch in some of the proposed topologies is utilized much better compared to the conventional Zeta and quadratic‐buck converters. The principle of operation, theoretical analysis, and comparison of circuit performances with other step‐down converters are discussed regarding voltage and current stress and switch silicon utilization. Finally, simulation and experimental results for a design example of a 50 W/5 V at 42‐V input voltage operating at 50 kHz will be provided to evaluate the performance of the proposed converters. Copyright © 2014 John Wiley & Sons, Ltd.     

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.     

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.     

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.     

An Approach to a Higher‐Power‐Density Power Supply for a 380‐V DC Distribution System

A methodology for realizing a higher‐power‐density DC‐DC converter has been proposed for a power unit installed in a 380‐V DC distribution system. The possibility of the converter design will be strengthened by using the series–parallel connection topology for isolated DC‐DC converters. A converter prototype with a power density of 10 W/cm³ has been fabricated, and the feasibility of the converter design has been confirmed experimentally. This result contributes to the realization of a highly efficient and highly space‐saving 380‐V DC distribution system. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 186(3): 51–62, 2014; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.22494     

Development of gate drive circuit for next‐generation ultrahigh‐speed switching devices

This paper describes a gate drive circuit which is capable of driving an ultrahigh‐speed switching device and of suppressing high‐frequency noise caused by its high dV/dt ratio of 104 V/μs order. SiC (silicon carbide)‐based power semiconductor devices are very promising as next‐generation ultrahigh‐speed switching devices. However, one of their application problems is how to drive them with less high‐frequency noise without sacrificing their ultrahigh‐speed operation capability. The paper proposes a new gate drive circuit specialized for such devices, which charges and discharges the input capacitance of the device by using an impulse voltage generated by inductors. This ultrahigh‐speed switching operation causes a high‐frequency common‐mode noise current in the gate drive circuit, which penetrates an isolated power‐supply transformer due to the parasitic capacitance between the primary and the secondary windings. In order to overcome this secondary problem, a toroidal multicore transformer is also proposed in the paper in order to reduce the parasitic capacitance drastically. By applying the former technique, the turn‐on time and turn‐off time of the power device were shortened by 50% and by 20%, compared with a conventional push‐pull gate drive circuit, respectively. In addition, the latter technique allows reduction of the peak common‐mode noise current to 25%, compared with the use of a conventional standard utility power‐supply transformer. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 176(4): 52–60, 2011; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21124