Multi-mode control based series-resonant dc-dc power converter

Abstract

A bi-directional series-resonant DC-DC power converter apparatus incorporating an improved multi-mode controller eliminates burst mode operation while supporting a wide voltage range handling capability. The converter includes a half bridge switching network and a full bridge switching network coupled together with a series resonant impedance including an inductor, a capacitor, and a transformer. Under normal and heavy load conditions, a controller regulates the converter output by varying the switching frequency of a half bridge and a full bridge switching network. The converter phase shift ensures ZVS operation based on a converter gain. Under light loading, the switching frequency will exceed a pre-determined maximum frequency and a second control mode is employed where the switching frequency is set to the maximum frequency and converter output is regulated by using a feedback control loop to vary the phase shift and duty cycle of the two switching networks.