Phase-shifted full-bridge PWM converter with clamping diodes and current transformer

Clamping diodes have been introduced into the zero-voltage-switched (ZVS) phase-shifted full-bridge (PSFB) pulse-width-modulated (PWM) converters to eliminate the voltage oscillation across the output rectifier diodes. However, the clamping diodes suffer from serious reverse recovery problem in output inductor discontinuous-current-mode (DCM) operation, impairing the reliability of the converter. A novel PSFB converter with clamping diodes and current transformer (CT) is proposed. The operation principles of the novel converter operating in output inductor CCM and DCM are analyzed in detail. The operation condition for the clamping diodes, the design considerations of the introduced CT and the output inductor are also given. Three 1200 W ZVS PSFB dc/dc modules, one being the conventional converter without CT, and the other two being the novel converters with different winding ratio of CT, are built for verification and comparison. Experimental results verify the effectiveness of the analysis and prove that the proposed converter has better reliability and higher efficiency compared with the conventional one.