Supra resonant fixed frequency full bridge DC-DC resonant converter with reduced switching losses

This paper presents the theoretical analysis and simulation results of a new topology of a full bridge DC-DC resonant converter that works with fixed frequency above resonance, providing nearly zero switching losses. The converter is basically a full bridge series parallel resonant converter that is connected to the input voltage source via two capacitors and an additional switch. The new idea presented in this paper consists in the proper control of the additional switch that connects and disconnects the two input capacitors, forcing zero voltage supply during the commutations of the bridge switches. This way, zero switching turn-on and, turn-off losses are obtained for the bridge switches, and ZVS for the auxiliary switch. This process allows the efficiency of the converter to be strongly improved, while maintaining fixed frequency operation. The converter is intended to be used in telecommunications equipment and is designed for 600 W output power with an internal frequency of 250 kHz, with PWM control.