A 700kHz High-Efficiency High-Power-Density Three-Level Parallel Resonant DC-DC Converter for High-Voltage Charging Applications

This paper proposes a variable-frequency zero-voltage-switching (ZVS) three-level parallel resonant converter, which is able to utilize the parasitic components of the high-turns-ratio transformer. Voltage stress of primary switches is half of input voltage. Low voltage MOSFETs with better performance can be applied. Zero-current-switching (ZCS) is achieved for rectifier diodes. Magnetic integration technique is applied. Only one magnetic component is required in this converter. The power factor concept of resonant converters is proposed and analyzed. A novel constant power factor control scheme is proposed. Based on this control strategy, the circulating energy of resonant converters is considerably reduced. High efficiency can be obtained for high-voltage high-power charging applications. The operation principle of the converter is analyzed and verified on a 700kHz, 3.7kW prototype. The power density of 72W/inch3 is achieved with over 88% efficiency.