离散移相控制全桥DC-DC变换器的能量迭代建模及多周期态研究

The study of energy model and multi-period of discrete phase shift control technique for full-bridge DC-DC converter

针对移相全桥DC-DC变换器,提出一种离散移相控制方法.通过建立移相全桥DC-DC变换器输出滤波电容能量模型,分析了离散移相控制全桥DC-DC变换器的能量迭代过程和控制原理.通过对离散移相控制全桥DC-DC变换器能量迭代过程的研究,揭示了其多周期态工作特性.与传统PWM移相全桥DC-DC变换器的仿真对比分析结果表明,离散移相控制全桥DC-DC变换器具有控制环路简单可靠、瞬态响应速度快等优点.

Phase-shift full-bridge （PSFB） DC-DC converter benefits from high efficiency by zero-voltage switching turn-on of all switches without any additional auxiliary circuit, and PSFB DC-DC converter has been widely used in high power applications. In this paper, the operating mode of PSFB DC-DC converter is studied, and the energy iteration model of PSFB DC-DC converter is established. The discrete phase shift （DPS） control technique for PSFB DC-DC converter is proposed and discussed. Unlike the conventional PWM PSFB control technique, the DPS control technique uses two preset phase shift times tpsH and tpsL as control variables where 0 〈 tpsH 〈 tpsL ≤ Tw with Tw being the switching period. When output voltage is lower than the reference voltage, phase shift time tpsH is selected, and a large duty cycle DH is obtained on the secondary side, which makes output voltage increase. Similarly, when output voltage is higher than the reference voltage, phase shift time tpsL is selected, and a small duty cycle DL is obtained on the secondary side, which makes output voltage decrease. With the energy iteration model, the energy iteration process is clearly revealed, steady-state and transient performances are studied. From the analysis results it can be known that the DPS controlled PSFB DC-DC converter always operates in a multi-periodic state. The simulation reasults show that the proposed control technique has an advantage over the conventional PWM PSFB control technique in simple design, great robust and excellent transient performance.