Half-Bridge LLC Series-Resonant Converter With Hybrid Rectifier for LED Signage Backlighting Systems

Large-area LED signage backlighting systems require power supplies to provide constant voltage to multiple LED modules connected in parallel, each with a built-in LED current regulator to maintain a constant output brightness. LED signage backlighting systems can be divided into 12 V and 24 V, which require different power supply specifications. The development of a universal 2-in-1 LED driver will reduce the number of power supply models and avoid incorrect wiring in the field. A new topology of half-bridge LLC series-resonant converter with hybrid rectifier is proposed in this brief, which automatically switches between full-bridge rectifier and half-wave rectifier by LED current detection. The hybrid rectifier switching mode enables an optimized design with two times the output voltage range, thus reducing the switching frequency range and the circulating current of the LLC series-resonant converter. The performance of the 60 W half-bridge LLC series-resonant converter with hybrid rectifier and the conventional half-bridge LLC series-resonant converter is experimentally compared. The results prove that there is a significant improvement in efficiency based on the 24 V output condition.