Invited Seminar at Ulsan National Institute of Science and Technology (UNIST), Ulsan, Korea

Title: More Bang for Your Buck: An Isolated Bidirectional DC-DC Converter for High Power Density

Abstract: For the 2018 IEEE International Future Energy Challenge student competition, our team developed a 1-kW wide-output-range (400 V to 35 V-50 V) bidirectional DC/DC converter used in residential energy storage systems using on gallium-nitride (GaN) devices. This talk will describe the design procedure for the two-stage configuration that was proposed. The first unregulated stage was a CLLC (690kHz) DC transformer, and the second regulated stage was a two-phase interleaved buck/boost converter (350 kHz-1 MHz). To achieve high frequency and high efficiency, the triangular-current mode operation is applied for the interleaved buck converter. For the unregulated CLLC converter, it can always work at its most efficient point, and an analytical model is used to optimize the planar transformer. The proposed 1-kW converter demonstrated 94% peak efficiency and 2.21 W/cm3 power density.

Also, Prof. Yu-Chen Liu met with Prof. Jeehoon Jung and Prof. Katherine A. Kim at UNIST to discuss research on high power density converters.