T17.2 - A Regulated 36V-60V-Input VIN-Insensitive Resonant Switched-Capacitor Converter with Large Voltage Conversion Ratio

This paper presents a regulated input-voltage-insensitive resonant switched-capacitor converter for 36V-60V to 3.3V/5V. In this design, the resonant capacitor voltages depend only on the fixed output voltage, avoiding resonant frequency variation with input voltage. This feature allows for the use of Class II capacitors (X7R, X7S, etc.) for saving cost and providing high power density. Meanwhile, the voltage difference between two resonant capacitors is greatly reduced and there is only 4% capacitance derating difference, which ensures a better match between two resonant tanks. Moreover, compared with the conventional two-stage architecture (a switched tank converter and a regulated buck converter), this converter realizes a larger voltage conversion ratio without adding more passive components. A prototype using only Class II capacitors has been designed with a constant resonant frequency of 340kHz, immune to input voltage and capacitance derating. Measurement results show that the converter achieves a peak efficiency of 92.6% for 36V-to-5V conversion and a power density of 567W/in3.