Analysis of Split-Capacitor Push–Pull Parallel-Resonant Converter in Boost Mode

This paper presents a new model that facilitates a comprehensive analysis of split-capacitor push-pull parallel resonant converter (PPRC) topology in three different modes. The three modes, named as normal, buck, and boost, are realized by operating the converter with a variable switching frequency, which is generated by modulating the damped resonant frequency with a variable phase-shift. The proposed modes allow the converter to operate with a variable voltage gain over a wide load range with zero-voltage switching (ZVS). In this paper, the operation and behavior of the converter in boost mode is analyzed in detail through derivation of explicit analytical expressions for voltage gain, ZVS frequency and other circuit variables. Experimental results of a 150 W prototype PPRC converter, controlled by the proposed technique, are presented and compared with simulations and theoretical results to prove the validity of both the proposed model and control technique. The results indicate that the gain of the prototype converter can be increased up to about 145% of the nominal voltage and the parasitic elements have only minor impact on the performance.