A High-Voltage Low-Power Switched-Capacitor DC-DC Converter Based on GaN and SiC Devices for LED Drivers
Keywords:DC-DC power converters, Gallium nitride, Silicon carbide, Switched capacitor circuits, Wide band gap semiconductors.
Previous research on switched-capacitor DC-DC converters has focused on low-voltage and/or high-power ranges, where the efficiencies are dominated by conduction losses. Switched-capacitor DC-DC converters at high-voltage (> 100 V) and low-power (< 10 W) levels with high efficiency and high power density are anticipated to emerge. This paper presents a switched-capacitor converter with an input voltage up to 380 V (compatible with rectified European mains) and a maximum output power of 10 W. The converter is intended for LED drivers. GaN switches and SiC diodes are analytically compared and actively combined to properly address the challenges at high-voltage low-current levels, where switching losses become significant. Further trade-off between conduction losses and switching losses is experimentally optimized with switching frequencies. Three variant designs of the proposed converter are implemented, and the trade-off between efficiencies and power densities is validated with measurement results. A peak efficiency of 98.6 % and a power density of 7.5 W/cm3 are achieved without heatsink or airflow. The characteristic impedance level of the converter is an order of magnitude higher than previously published ones.
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