A new pulsewidth-modulated zero-voltage-switching multi-resonant converter using resonant inductor freewheeling

A new pulsewidth-modulated zero-voltage-switching multi-resonant converter (PWM-ZVS-MRC) operating at constant switching frequency is presented. Instead of controlling the switching frequency, the output voltage is regulated by controlling the freewheeling period of the resonant inductor. This converter possesses the advantages of the PWM converter and the frequency-modulated (FM) ZVS-MRC. In contrast to its quasi-resonant counterpart, namely the PWM-ZVS-QRC, it provides significant reduction in voltage stress and dramatic improvement in load range. Moreover, by absorbing all major parasitic components in the resonant circuit, the possible parasitic ringing occurring in the PWM-ZVS-QRC is eliminated. The principle of operation of both buck and boost versions are described. The mathematical derivation is concentrated on the steady-state analysis of the buck PWM-ZVS-MRC. Finally, the experimental results agree with the theoretical prediction