High-frequency DC-DC Converter in Electric Vehicle Based on GaN Transistors

DC-DC converter in electric vehicle (EV) has higher demand for high efficiency and power density. Faster switching is beneficial to high power density. Gallium nitride (GaN) power transistors have the advantages of faster switching capability, smaller parasitic parameters and better electric parameters, which make them more suitable to achieve higher switching frequency and power density in DC-DC converter in EV. In this paper, the two-staged converter consisting of Buck and multi-phase interleaved half-bridge LLC series resonant converter (LLC-SRC) is chosen as the main topology. The current sharing problem caused by the mismatch between resonant components is analyzed and improved. Design consideration of driver of low-voltage GaN transistor and the efficiency improvement of high-voltage GaN transistor in LLC-SRC are analyzed. A 1MHz/2kW, 330V/12V DC-DC converter prototype is fabricated and efficiency comparison experiment with Si MOSFET is finished. Experimental results show that GaN power transistor has superior high frequency switching capability and efficiency advantage compared to Si MOSFET.