1MHz LLC resonant DC-DC converter with PWM output regulation capability

This paper proposes a 1MHz resonant DC transformer (DCX) with output regulation capability based on the traditional LLC resonant converter. The proposed regulated DCX (RDCX) has a configuration with an auxiliary transformer in series with the main transformer at primary side but independent at the secondary side. And, the auxiliary transformer creates an output to feed the cascaded PWM dc-dc converter. Since the output of the PWM dc-dc converter is parallel with the main output, the tight regulation of output voltage can be realized by adjusting the duty cycle of the auxiliary dc-dc stage. The majority of power is delivered to load through the main transformer, and only small portion of power is converted by two-stage. Therefore, the total conversion efficiency is almost as high as conventional LLC-DCX. The steady state operating principle of the proposed converter is analyzed and a 1MHz prototype is built-up to verify the theoretical analysis in this paper.