Study Of The Half-bridge Zero-Voltage-Switching Bidirectional Converter For Vehicle Application

Bi-directional DC-DC converters can easily control the transfer of power between two DC sources, and will be widely used in applications as fuel cell vehicles, aerospace systems, and new power generation system which utilize clean energy. However, there exit key problems in their applications, which are power density, EMC and cost. Soft switching is one of key technology to solve these problems. Some circuits use resonant, quasi-resonant, and multi-resonant techniques. However, voltage and current stress in these converters are higher. Some circuits use passive snubbers or active clamp techniques. However, these converters become more complicate. Phase-shift bi-directional DC-DC converter is attractive since it operates with fixed frequency, has small voltage and current stress and can realize ZVS without auxiliary switches.A novel bi-directional DC-DC converter is introduced, which based on referring to much converter data. The converter is composed of two symmetrical half-bridge circuits. The flow of power is controlled by phase-shift modulation. The proposed topology has the advantages of soft-switching implementation without additional devices, high efficiency and simple control. The converter mainly is used for auxiliary power supply in fuel cell vehicles where a bi-directional DC-DC converter is needed for cold start and battery recharge. The soft switching, phase-shifted PWM and bi-directional DC-DC converter hang together, depress circuit switching loss and noise effectively, which provide condition to increase switch frequency, efficiency and reduce size and weight for the converter; at the same time, it is proved the converter can achieve ZVS in larger load variation, and the converter has the virtue of structure compact, voltage and current stress small such as ordinary hard switch converter.In this paper, the operation principle and the equivalent circuit structures in different periods of time of the dual-bridge zero-voltage-switching(ZVS) bi-directional DC-DC converter are analyzed. The condition of achieving soft-switched is derived. And the design of control circuit is achieved. The emulation result proves that the circuit structure and control method are valid. The averaged model is derived, and can be used to offer theoretic foundation of the close-loop design on detail circuit. At last,the simulation verifications and experimental results are also presented.