Overcurrent protection for the LLC resonant converter with improved hold-up time

The LLC resonant converter topology enables high DC-DC conversion efficiency and has been recently adopted for power supplies in several application areas. In this paper a method for overcurrent protection of the LLC resonant converter is proposed, which avoids a reduction of the hold-up time resulting from the application of the protection scheme. The discussion covers the operation principle, design aspects and a detailed analysis of the circuit operation. Finally measurements on a prototype are presented showing an improvement in the hold-up time of up to 83%.