Non-Backflow-Power and Reduced-Switching-Loss Modulation for Bidirectional Series Resonant Converter With Wide Gain Range

In the achievement of high power efficiency over a wide gain range for a bidirectional series resonant converter (BSRC), conduction losses caused by backflow power and switching losses are two challenges. In this article, a novel modulation of the BSRC is proposed for a wide voltage gain range and high efficiency as well. With the proposed modulation, the BSRC can operate in both buck- and boost-like modes for a wide gain range. The resonant current is in phase with the terminal voltage on both primary and secondary sides, to eliminate the backflow power for the reduction of conduction losses. Hard turn-off problem is alleviated with a resonant current fully released before the completion of the switching cycle. Thus, the number of hard switching actions is significantly reduced compared with existing modulation schemes in the literature. A control scheme based on state-flowchart is also proposed to realize seamless transition among different working modes. To validate the proposed modulation, a 1 kVA prototype of BSRC is developed and interfaces a high-voltage bus ranging from 240 to 480 V and a low-voltage bus ranging from 24 to 56 V. Compared with conventional modulation schemes, efficiency enhancement can be observed over the whole operating range.