Research on Soft-Start Method and Light Load Intermittent Control of LLC Resonant Converter

With its resonant characteristics, LLC resonant converters can achieve soft-switching characteristics within the full input voltage and load range, and have superior soft-switching performance, which can effectively reduce high-frequency switching losses and improve system efficiency. Considering the phenomenon of large inrush current during high-voltage startup of LLC resonant converters, this paper studies the optimal soft-start scheme to determine the optimal soft-start scheme for frequency reduction and phase-shift hybrid startup to achieve the optimal goal of minimum inrush current. Furthermore, in order to alleviate the problems of wide voltage gain range and low control efficiency under light load, the control strategy of intermittent mode is adopted to effectively reduce the light load loss. Finally, an experimental prototype with a rated power of 2 kW and a resonant frequency of 500 kHz was built to verify the above theoretical methods.