A wide input voltage and load output variations fixed-frequency ZVS DC/DC LLC resonant converter for high-power applications

This paper presents a fixed-frequency zero-voltage-switching three-level DC/DC resonant converter. By applying phase-shift control between the primary and secondary sides of the transformer, the converter can operate at a fixed switching frequency. The converter can achieve ZVS operation in the entire load range by using the magnetizing inductance of the transformer. In addition, the converter can operate with wide input-voltage variations without penalizing the efficiency. Therefore, the converter is suitable for applications in which high efficiency and high power density are required. The principle of operation for the converter is analyzed and verified on a 2.75 kW, 775 kHz experimental prototype.