Soft-Switch Full-Bridge Secondary Dual Resonance DC-DC Converter

Nowadays, the full-bridge converter is widely used in high-voltage and high-power applications. Traditional full-bridge PWM DC-DC converter has such advantages as simple circuit structure, easy to implement, but it can not achieve soft-switching, so that the efficiency is lower.The phase-shifted full-bridge converter can achieve soft-switching of the power switches, but it has several shortages such as the lag-leg’s soft-switching conditions were difficult to achieve, secondary side rectifier diode’s reverse recovery losses, and circulation losses etc.In order to achieve the soft-switching of the power switches and rectifier diodes with full range of loads, eliminate the circulation losses, the full-bridge secondary side dual resonance DC-DC converer based on the secondary side resonance technique is proposed and studied in detail in this paper.The operational principles and steady state characteristics of the full-bridge secondary side dual resonance DC-DC converter with symmetric and asymmetric control strategy were discussed respectively. The operating parameters of each component were calculated, and the soft-switching conditions of power switches and rectifier diodes were gave. The research shows that the voltage gain of the converter with symmeric control strategy is independent of its output load, switching frequency and duty cycle,other wise the converter with asymmeric control strategy shows the PWM converter’s operating characteristics whose voltage gain can be adjusted by the duty cycle.The full-bridge secondary side dual resonance DC-DC converter can achieve soft-switching of power switches and rectifier diodes, eliminate the circulation losses, with symmetric and asymmetric control strategy. Moreover, the proposed converter eliminates the voltage spike and oscillation of the rectifier diodes, clamps the diode voltage at the output voltage to decrease the voltage stress of the rectifier diodes.Based on the theoretical analysis, the main circuit parameters of the proposed converter with asymmetric control strategy were designed. And the simulation was carried out with the Saber software. Finally, experimental results from a1kW400V/48V prototype are presented to verify the analysis of the proposed converter. Experimental results show that the proposed converter has more advantages in the soft-switching range of power and primary circulation losses compared to the conventional phase-shifted full-bridge converters.