IGBT/MOSFET Hybrid Bridge with Phase Shift and Frequency Modulation Control for a Bi-directional Series Resonant Converter

A circuit topology and its control for a bi-directional isolated series resonant converter (SRC) are proposed. In general SRCs, when the output voltage is decreased, the turn-off current and the switching frequency are increased and efficiency is decreased due to the increase of switching loss. MOSFETs are therefore mainly used, as MOSFETs have a lower turn-off loss than IGBTs. In the present study, to achieve both low cost and high efficiency, the proposed converter utilizes an IGBT/MOSFET hybrid bridge that consists of an IGBT leg and a MOSFET leg to form a full bridge. In the proposed control using phase shift with pulse-frequency modulation, MOSFET is turned off first and the IGBT current is decreased. After that, the IGBT is turned off at reduced current. The results of testing demonstrated that the proposed control reduces the turn-off current of the IGBT and also the switching frequency under conditions of low output voltage. A prototyped converter showed 96.6 % efficiency at the IGBT switching frequency of 117.7 kHz.