A digital controlled short-circuit current limiting method for LLC converters with fast response and resonant current limiting

The increasing-frequency method is one of the most easy and practical ways of current limiting for LLC since it requires no additional components and ZVS can be realized all the time. However, when applying this method, previous study makes no attempt to limit the peak resonant current in dynamic state or to accurate the output current in steady state, and the large output current spike lasting time is not the minimized. This paper proposed a digital controlled short-circuit current limiting method for LLC converters. The method including 4 steps, has faster output current spike dropping time, and can limit the dynamic resonant current and precisely regulate the steady-state output current, which provides a safer guarantee for LLC's post-stage circuit. And the method is also suitable for parallel LLC, which can realize current sharing. The method was verified on two 1.5kW LLC.