A High-Voltage Low-Power Switched-Capacitor DC-DC Converter Based on GaN and SiC Devices for LED Drivers

Abstract

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/cm 3 are achieved without heatsink or airflow. The characteristic impedance level of the converter is an order of magnitude higher than previously published ones.

A 240V to 47.5 V Fully Integrated Switched-Capacitor Converter in GaN Achieving 62.6% Efficiency at 220 mW/mm2

“…The used GaN-on-SOI process provides high-quality n-type power transistors with a drain-source breakdown voltage of 200 V. Compared to traditional silicon transistors, they have lower parasitic capacitances for the same on-resistance R on . Hence, for the same R F SL (4), they have significantly lower switching losses (6). Besides these high-voltage power transistors, GaN-on-SOI also offers low-voltage n-type transistors, which can be used to implement control circuits [8].…”

“…As shown in Fig. 1, most reported GaN-based voltage converter designs use discrete GaN HEMTs with CMOS silicon drivers [6], [7]. However, recent technology progress allows higher levels of integration.…”

“…Table I compares the simulation results of the proposed converter to the state-of-the-art. This design is the first work to fully integrate a converter at input voltages higher than 200 V. Conventional designs at these specifications all make extensive use of external components [1], [6], [7]. Although higher-quality external components would result in a higher efficiency, a fully integrated converter significantly enhances the cost, compactness and reliability.…”

Design of a High-to-Low Voltage, Low-Power, Isolated DC/DC Converter for EV Applications

“…To overcome these limitations some interesting alternatives may be considered: Input Series Converters (ISC) [8], Switched-Capacitor (SC) stages [11] and Multi-Level Flying-Capacitor converters [12]. Previously, a qualitative comparison was built between these structures to determine which of them is suitable for a HVLP converter [13].…”