A High Efficiency High Power-Density LLC DC-DC Converter for Electric Vehicles (EVs) On-Board Low Voltage DC-DC Converter (LDC) Application

This paper presents a high efficiency high power-density LLC DC-DC converter for Electric Vehicles (EVs) on-board low voltage DC-DC converter (LDC) application. In the proposed LDC, primary switches achieve ZVS turn-on and secondary synchronous rectifier switches achieve ZVS turn-on and ZCS turn-off. To reduce current stress and improve efficiency, three phase interleaved LLC DC-DC converters are paralleled to provide more than 200A load current. Switch-Controlled Capacitor (SCC) technology is used to achieve the load current sharing of the three phase LLC DC-DC converter. In addition, GaN HEMTs are used in the transformer primary to improve the switching frequency and power-density. To verify the analysis, a 3.8kW(14V/270A) LLC DC-DC converter prototype is designed. The experimental results show that full load efficiency is 95.8% at 270A load current and 3kW/L power-density is achieved.