Over current protection methods for LLC resonant converter

LLC resonant converter was getting more and more attention in recent years because of its high efficiency, high frequency operation capability and simple structure. In this paper, the over current protection issue of LLC resonant converter is discussed. Three methods to provide over current protection function for LLC converter are proposed and investigated. They are: increase switching frequency control, variable frequency+PWM control, and diode clamping method. The pros and cons for each method were discussed. Tests were performed to verify the discussion.