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

Abstract

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 0tpsHtpsL ≤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.