Analysis of two-section phase-controlled resonant voltage converter

Abstract

Analysis of two-section resonant DC-to-DC converter with phase power control is carried out in this paper. Two-section converter is considered as a boundary case of the multi-section converter with only one controlled section and other uncontrolled sections. The converter sections are parallel resonant half-bridge voltage inverters with a common resonant capacitor connected to the load through a matching transformer, center-tapped rectifier and smoothing filter. One of the sections is the reference, relative to which the phase shift of the output pulses of the other section is adjusted. The switching frequency of the converter is constant, which improves its electromagnetic compatibility. Analysis is carried out by the fundamental harmonic approximation method. Analytical expressions for voltage and current phasors in both sections of the converters have been established. The dependence of the converter power on the phase shift between the pulses of the half-bridge inverter sections was obtained. The dependence of the efficiency of the converter on the power was analyzed. It is shown that the efficiency slightly decreases when the power is reduced in a wide range of powers and only at powers less than 10% of full load power it drops sharply. The problems of operation of section transistor switches in their zero-voltage switching mode is considered. Verification of the conducted analysis was carried out by simulation of the converter circuit using the PSIM program for modeling power electronics devices. The simulation results are in a good agreement with the analysis results.