High Efficiency LLC-Based AC-DC Converter for Wide Load Voltage Range Applications

Inhalt:
In order to prevent power efficiency reduction in DC-DC stage of front end AC-DC converters for high efficiency high power density applications with wide load voltage range, an LLC-based converter arrangement is proposed in this paper. To achieve higher efficiency in this arrangement, the LLC circuit is designed to operate and remain under resonance frequency for all output voltages and a boost-based PFC stage regulates LLC output voltage magnitude through DC-bus voltage adjustment. A three loop control strategy is used to control the proposed AC-DC converter. To achieve fast response of load voltage, an inner hysteresis current mode control system has been employed which also provides low ripple input AC current for wide input voltage range.