对称控制全桥谐振PWM软开关变换器

摘要

The traditional symmetrical controlled full bridge DC-DC converter fails to achieve soft switching. Thus, this paper proposes a full bridge resonant PWM (FB-RPWM) converter. Its operation modes and steady state characteristics are analyzed. The analysis results show that FB-RPWM converter exhibits the characteristics of DC-DC transformer (DCX), and its DC voltage conversion ratio is independent of load, switching frequency and duty ratios. The proposed FB-RPWM converter can realize zero-voltage turn-on switching (ZVS) of switches in the full load range and zero-current turn-off switching (ZCS) of the diode. Compared with the traditional phase-shift full bridge (PSFB) converter, FB-RPWM converter has reduced switch current stress and turn-off current of the main switch. It has also completely eliminated current offset of magnetizing inductor, and thus improved the efficiency of the converter. Finally, a 400V input, 50V/10A output experimental prototype is established to verify the theoretical analysis.%针对传统对称控制全桥变换器不能实现软开关而导致变换器效率较低的现状，提出了对称控制全桥谐振 PWM(FB-RPWM)变换器，详细分析了 FB-RPWM变换器的工作模式及其稳态特性。分析结果表明：FB-RPWM 变换器虽然采用对称控制，却仍在全负载范围内实现了所有桥臂开关管的零电压开通（ZVS）和输出二极管的零电流关断（ZCS），且其输入输出电压传输比与负载、开关频率和占空比无关，呈现出直-直变压器（DCX）的工作特性。与移相全桥（PSFB）变换器相比，FB-RPWM 变换器减小了两个开关管的关断电流，且变压器一次侧采用隔直电容，实现了励磁电感电流的零直流偏量，降低了变压器损耗，进一步提高了变换器的效率。最后，搭建了一台400V输入、50V/10A输出的实验装置，验证了理论分析的正确性。