电动汽车直流变换器中高压MOSFET的振荡分析与改善

电动汽车需要高功率密度、高效率、高可靠性的高压到低压DC-DC变换器来给车内的低压电子负载提供电源。ZVS移相全桥拓扑利用电路寄生元件实现器件零电压开关,具有开关损耗低、工作频率高、功率器件开关应力小、变换器可靠性高等优点。当出现导通延迟现象时,普通功率MOSFET在移相全桥变换器中由于体二极管反向恢复特性差不能及时清除内部载流子,会导致器件在开关过程中出错,进而影响系统的可靠性。英飞凌新型过AEC-Q101认证高压功率COOLMOS CFDA带有极快速的体二极管,并具有极低的导通电阻。实验表明在移相全桥变换中使用CFDA能够减小潜在体二极管反向恢复问题,提高系统效率以及可靠性,尤其适用于车用HV-LV的DC-DC变换器。

Analysis and improvement on the oscillation behavior of high voltage MOSFET in automotive DCDC converter

For providing the power to the low voltage electronic load, electric vehicles require the DC-DC converter with high power density, high efficiency and high reliability. ZVS phase-shifted full-bridge topology utilizes circuit parasitic elements to achieve zero-voltage switching, it has the advantage of low switching losses, high frequency, low switching stress etc, it is suitable for the DC-DC converter of vehicles. But if use the ordinary power MOSFET in the converter, the device maybe oscillate or even get failure during switching for the poor recovery characteristics of the body diode. The CoolMOSTM CFDA of Infineon, which has passed the AEC-Q101 authentication, it can improve this oscillatory behavior with fast recovery body diode. Experimental results show that use the high voltage MOSFET in the phase-shifted full-bridge converter, the oscillation problems which bring from the recover behavior of body diode can be reduced, the system efficiency and reliability is improved, it is especially useful to the DC converters with HV to LV.