An improved phase shifted bridge converter for high voltage applications

In high voltage (HV) applications, it is attractive to dispense with the expensive output inductor and operate with a purely capacitive filter. This paper shows that the HV Phase Shifted Bridge with capacitive filter (PSBCF) converter can lose soft switching in two MOSFETs. This can result in a lower efficiency and a limitation of operation to the lower switching frequencies. The LDD auxiliary circuit developed for the standard PS-PWM-ZVS-FB converter is adapted to assist the HV PSBCF with ZVS. The operation of the auxiliary circuit is explained and its performance examined.