CONTROL CIRCUIT FOR REDUCING POWER LOSS OF LLC RESONANT CONVERTER DURING LIGHT-LOAD OR NO-LOAD OPERATION

摘要

The present invention particularly discloses a control circuit comprising a signal detection unit and a controller unit for reducing power loss of a LLC resonant converter during light-load or no-load operation. In the present invention, the signal detection unit is adopted for sensing a primary-side current from a transformer unit of the LLC resonant converter, and then converting the primary-side current to a reference voltage signal. Thus, according to a level variation of the reference voltage signal, the controller unit is able to properly regulate duty cycle of a switch controlling signal based on a duty cycle reduction percentage. Eventually, by using the switch controlling signal to control the periodic ON-OFF switching of power switches, power loss of the LLC resonant converter operated under light load or no load can be obviously reduced; moreover, working temperature of the power switches is simultaneously lowered.