Isolated DC-DC Converter utilizing GaN power device for Automotive Application

This paper presents an isolated step-sown DC-DC converter using GaN power device for automotive applications. The works for a power supply from a high voltage main battery with 200V to low voltage auxiliary battery with 13.6V in hybrid electric vehicle. A LLC converter is known as isolated DC-DC converter with high-efficiency. However, when input and/or output voltage considerably fluctuates, efficiency of a LLC resonant converter becomes worse. In order to solve this problem, a DC-DC boost-up converter to mitigate efficiency deterioration for the input and/or output voltage fluctuation is added to a LLC resonant converter. Generally speaking, an additional circuit, the boost-up chopper in this case, also deteriorates the total system efficiency. To avoid the efficiency degradation, discontinuous current mode control and GaN power devices are applied to the boost-up chopper. The DC-DC boost-up converter experimentally achieves 99.03% of conversion efficiency at nominal output so that it has no effect on the total system efficiency. Even though adding a DC-DC boost-up chopper to the LLC resonant converter, a power density expected to 10 W/cc.