Implementation of digitally controlled phase shift full bridge converter for server power supply

Abstract

The digital controller of the phase-shift full bridge converter for a server power supply is designed and implemented in this paper. Analog controllers are replaced by single MCU (micro controller unit) that not only manages the protection or the operational flow of a power supply but also controls the converter. Voltage mode controller is designed based on the z-domain small signal model considering effect of variation on output filter inductance. Moreover, gain scheduling is applied to adjust the controller gain according to load current. The current offset flowing through a magnetizing inductor is eliminated by adding PI compensator instead of inserting a blocking capacitor that may increase loss, cost, and volume. The saturation of a transformer and the conduction loss due to the current offset can be prevented. The performance of designed controller is verified by the experiments on 1.2kW phase-shift full bridge converter.