Adaptive Voltage-Controlled Oscillator for Improved Dynamic Performance in LLC Resonant Converter

This paper proposes an adaptive voltage-controlled oscillator (VCO) to improve the dynamic performance in LLC resonant converters. The proposed adaptive VCO is designed to have frequency-dependent small-signal gains, so that the variation of low-frequency magnitude in frequency response of LLC resonant converter is effectively adjusted. As a result, an enhanced dynamic performance is obtained over wide-operating ranges. Through approximated derivation, the proposed adaptive VCO has a simple formula and does not require any additional sensing circuits. Furthermore, it is robust to variation of circuit parameters. Dynamic performance enhancement was verified by experimental results with a 144-W laboratory prototype half-bridge LLC resonant converter.