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     

Analysis and Implementation of a ZVS-PWM Converter With Series-Connected Transformers

This brief presents the analysis, design, and implementation of zero-voltage switching (ZVS) active clamp converter with series-connected transformer. A family of isolated ZVS active clamp converters is introduced. The technique of the adopted ZVS commutation will not increase additional voltage stress of switching devices. In the adopted converter with series-connected transformer, each transformer can be operated as an inductor or a transformer. Therefore, no output inductor is needed. To reduce the voltage stress of the switching device in the conventional forward converter, the active clamp technique is used to recycle the energy stored in the transformer leakage back into the input dc source. Finally, experimental results are presented taken from a laboratory prototype with 100-W rated power, input voltage of 155 V, output voltage of 5 V, and operating at 150 kHz. [All rights reserved Elsevier].     

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.     

A new family of isolated converters that uses the magnetizinginductance of the transformer to achieve zero-voltage switching

A new family of isolated, zero voltage switched power converters which utilizes the magnetizing inductance of the transformer to achieve zero voltage turn-on of the primary switches is proposed. By employing saturable inductor(s) on the secondary side, soft turn-off of the output rectifier(s) is obtained with a minimum circulating energy flowing through the power converter. The proposed converters can operate either with a variable or a constant switching frequency. A complete DC analysis and design guidelines for the half-bridge topology are described, and the performance of a 100 W experimental power converter is presented     

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 high-performance, integrated magnetics scheme for buck-cascaded push-pull converter

This letter proposes a new integrated magnetics scheme for the buck cascaded current-fed push-pull converter. While integrating the transformer and inductor into a common structure, the proposed scheme also alters the operating characteristics of the basic converter. This leads to several advantages such as, continuous output current, zero voltage switching (ZVS), and zero current switching (ZCS) for the switches of the push-pull stage, and reduced conduction losses. The principle of operation of the proposed scheme is analyzed using the gyrator-capacitor model. Experimental results from a 12 V/5 A proof-of-concept prototype are presented demonstrating the advantages of the proposed scheme.     

Analysis and design of LCL-type series resonant converter

A series resonant converter modified by adding an inductor in parallel with the transformer primary (or secondary) is presented. This configuration is referred to as an “LCL-type series resonant converter”. A simplified steady-state analysis using complex AC circuit analysis is presented. Based on the analysis, a simple design procedure is given. Detailed experimental results obtained from a MOSFET-based 640 W converter are presented to verify the analysis. A narrow variation in switching frequency is required to regulate the output voltage for a very wide change in load, and the converter has load short-circuit capability. It is shown that by placing the parallel inductor on the secondary side, the parasitics of the high-frequency transformer can be used profitably     

An improved soft-switching PWM FB DC/DC converter for reducingconduction losses

An improved soft-switching topology of a full-bridge (FB) pulsewidth-modulated (PWM) DC/DC converter is described. The new topology employs an energy-recovery snubber to minimize a circulating current flowing through the transformer and switching devices. By using an energy-recovery snubber instead of adding a tapped inductor and a saturable reactor to reduce RMS current stress, the converter achieves zero-current switching (ZCS) for the right leg due to the minimized circulating current and achieves zero-voltage switching (ZVS) for the left leg due to the reflected output current during the interval of left leg transition. Both analysis and experiments are performed to verify the proposed topology by implementing a 7 kW (120 VDC, 58 A) 30 kHz insulated gate bipolar transistor (IGBT) based experimental circuit     

High-Efficiency Boost Half-Bridge Converter With Fast Boost Current Transferring ZVS Operation

A new boost half bridge (BHB) converter is presented. It is composed of additional switch, diode and coupled winding to boost inductor of BHB converter. Using the transferring of boost inductor current to coupled winding in a short period, the cancellation of zero voltage switching (ZVS) current, which always occurs in convention one, is prevented. Therefore, the ZVS operation is easily achieved by leakage inductor current of transformer. Furthermore, since negatively build-up leakage inductor current of boost winding helps the ZVS operation throughout full load range, the excellent ZVS operation and high efficiency is achieved.      

Integrated magnetic full wave converter with flexible output inductor

A new integrated magnetic full wave DC/DC power converter that provides flexible transformer design by incorporating an independent output inductor winding is introduced. The transformer is implemented on a traditional three-leg magnetic core. The inductor winding can be separately designed to control the output current ripple. The cross-sectional area of the inductor core leg can be reduced dramatically. The operation and performance of the proposed circuit are verified on a 100 W prototype converter.     

Low cost high efficiency DC-DC converter for fuel cell powered auxiliary power unit of a heavy vehicle

In this paper, a new dc-dc converter for solid oxide fuel cell (SOFC) powered auxiliary power unit (APU) is proposed. The proposed converter does not consider the leakage inductance of the transformer as a parasite and uses it for energy transfer, thus avoiding problems of low efficiency and difficulty in control, caused by leakage inductance. The need for a separate filter inductor is also eliminated. Soft switching is done for some of the switches of the proposed converter, thereby further increasing the efficiency of the converter. Thus, the achieved low cost and high efficiency of the proposed converter make it suitable for SOFC powered APU applications. Simulation and experimental results are presented to verify the proposed dc-dc converter. The achieved cost and efficiency of the prototype are 50.8$/kW and 90%, respectively.     

Three-phase synchronous PWM for flyback converter with power-factor correction using FPGA ASIC design

The design and development of a synchronous pulsewidth modulation (PWM) generator suitable for the three-phase flyback converter with transformer isolated and power-factor correction using a field-programmable gate array is proposed. The proposed three-phase synchronous PWM makes it possible for the converter to obtain the sinusoidal supply currents with a near-unity power factor. A high-frequency transformer is considered in the design to provide galvanic isolation and serves the dual role of inductor and transformer. Results are provided to demonstrate the effectiveness of the design.     

一种应用于48 V-1 V系统的隔离型混合模式降压变换器

提出了一种应用于48 V-1 V系统的隔离型混合模式降压变换器,利用飞电容和变压器实现高转换比应用下的高转换效率。混合变换器结合了开关电容变换器和开关电感变换器,其中飞电容承担了部分电压降,实现了功率开关管电压应力的降低。由于开关节点处的电压摆幅较小,开关损耗随之减小;通过使用更低压的功率开关管,实现功率开关管导通损耗减小。在此基础上,隔离型混合模式降压变换器通过时序控制可以实现软开关,进而实现功率开关管开关损耗减小,使得整体效率提升。在隔离型混合模式降压变换器中,飞电容还具有隔直电容的作用,可以防止变压器偏磁。在典型应用下,即在48 V输入电压、1 V输出电压、500 kHz开关频率下,峰值效率为94.84%。     

一种零电压开关Zeta变换器的设计

给出了一种零电压开关Zeta变换器,这种变换器可以提高效率和减小功率开关管的电压应力.当变换器工作在连续模式时,应用谐振电容和变压器的漏感实现功率开关管的零电压导通.详细分析了变换器的工作原理,并设计了相应的电路进行验证.仿真结果表明所设计的Zeta变换器效率达92.21%,输出电压纹波为125 mV.它可被用于等离子显示屏(PDP)电源系统.     

Integrated ZVS DC–DC converter with continuous input current and high voltage gain

An integrated zero-voltage-switching (ZVS) DC–DC converter with continuous input current and high voltage gain is proposed. The proposed converter can operate with soft switching, a continuous inductor current and fixed switching frequency. The voltage stress of the power switches is relatively low compared to the output voltage. Moreover, soft-switching characteristic of the proposed converter reduces switching loss of active power switches and raise the conversion efficiency. The reverse-recovery problem of output rectifiers is also alleviated by controlling the current changing rates of diodes with the use of the leakage inductance of a coupled inductor. The operation and performance of the proposed DC–DC converter were verified on an 115?W experimental prototype operating at 100?kHz.     

The zero Voltage switching (ZVS) critical conduction mode (CRM) buck Converter With tapped-inductor

The critical conduction mode (CRM) control has some disadvantages such as the increase of switching loss and conduction loss of the main switch at extreme high/low voltage conversion applications. In this paper, a CRM buck converter with tapped inductor is proposed to overcome these problems. In this converter, both the active switch and the diode have soft switching operation by the resonance between the switch parasitic capacitors and the filter inductor. Furthermore, the peak current of the main switch is reduced by tapped inductor operation, thus the conduction loss and switching loss levels of the main switch are lowered. Consequently, this tapped inductor scheme with CRM control alleviates the severe power stress and enhances device utilization. For the proposed converter evaluation, this paper provides the operation analysis and design procedures of the converter, and also presents the hardware verification for a 50-W prototype operating at maximum 70 kHz. Finally, a new topology family derived by combination of CRM operation with the basic tapped-inductor converter is included.     

A ZVZCS PWM FB DC/DC converter using a modified energy-recovery snubber

The conventional high-frequency phase-shifted zero-voltage-switching (ZVS) full-bridge DC/DC converter has a disadvantage, in that a circulating current flows through transformer and switching devices during the freewheeling interval. Due to this circulating current, RMS current stress, conduction losses of the transformer and switching devices are increased. To alleviate this problem, this paper proposes an improved zero-voltage zero-current switching (ZVZCS) phase-shifted full-bridge (FB) DC/DC converter with a modified energy-recovery snubber (ERS) attached at the secondary side of transformer. Also, the small signal model of the proposed ZVZCS FB DC/DC converter is derived by incorporating the effects introduced by a transformer leakage inductance and an ERS to achieve ZVZCS. Both analysis and experiment are performed to verify the proposed topology by implementing a 7-kW (120 VDC, 58 A) 30-kHz insulated-gate-bipolar-transistor-based experimental circuit.     

零电流开关大功率DC/DC双全桥变换器设计

提出了一种基于双全桥结构的单向零电流开关大功率（兆瓦级）DC/DC变换器,该变换器通过采用两个全桥变换器来实现零电流开关,实现了较低的功率损耗和输出滤波电感。为了验证提出的变换器在大功率应用中的有效性,构建了小型样机并在大功率直流电网进行了实际测试。实验证明,相比传统的两种单向大功率全桥变换器,提出变换器所需的滤波电感和半导体器件的功率损耗均较少,分别仅为1.72mH和924.5kW。     

Transformer secondary leakage inductance based ZVS dual bridge DC/DC converter

A novel zero voltage switching (ZVS) dual bridge dc/dc converter is presented. The proposed converter is composed of two dual-transistor-forward converter, coupled with a single high frequency transformer. ZVS is realized by introducing a proper leakage inductance to the secondary of the high frequency isolation transformer with a corporation of a designed pulse-width modulation control. Operation principle and ZVS condition of the proposed converter are analyzed. Experimental results obtained from a 3.2-kW prototype are given. Extensions of the proposed converter topologies and experimental results of one extension converter are presented.     

Analysis and design of a modified series resonant converter

A modified series resonant converter (SRC) (also referred to as the LCL-type SRC) which overcomes the problems of the standard series resonant converter is presented. A state-space approach is used for the analysis. Analysis shows that the converter enters into three different modes. Converter gain and other component stresses are plotted with variation in the load current. Detailed experimental results obtained from a 500 W MOSFET converter are presented to verify the theory. With a proper selection of inductor ratio, only a narrow variation in switching frequency is required to regulate the output voltage for wide variation in the load current. It is shown that, by placing the parallel inductor on the secondary side, the parasitics of the high-frequency transformer can be used profitably