Current Sensorless Synchronous Rectification Method of SiC-Based LLC Resonant Converter in Power Supply Units

This paper proposes a novel current sensorless synchronous rectification (CSSR) method for silicon carbide (SiC)-based LLC resonant converter to improve the efficiency, power density, and stability of power supply units (PSUs). The proposed CSSR method is implemented by using voltage gain and switching frequency with the input and output voltage sensors. However, it does not require any output current sensors, differently from the existing sensorless methods. This results in improving its power density. Also, it ensures the high efficiency and stability by using the accurate synchronous rectification (SR) strategies based on time-domain analysis. In particular, it enables the use of digital signal processor (DSP) cost-effective by simply adopting their look-up tables. As the result, the proposed CSSR method is suitable for high switching frequency operations based on SiC devices. The featured characteristics and operational principles of proposed CSSR method are firstly described. Then, they are mathematically investigated by time-domain analysis. Finally, its practical effectiveness is verified by experimental tests on a hardware prototype of 1.5 KW LLC resonant converter with SR.