Closed loop control analysis of half-bridge 1] resonant converter based battery charger

Series Resonant Converters (SRC) popularly known as Line Level Controlled (LLC) converters are the most suitable topology of DC-DC power supply. The closed loop voltage regulation of a Half-Bridge (HB) Line-Level-Controlled (LLC) converter using PI controller is presented in this paper. Major objective of PI controller is to modulate frequency and duty ratio of gate signals. A voltage controlled oscillator (VCO) is generating the gating signals which will drive the MOSFETs for getting a regulated output voltage. The optimum LLC switching frequency ranges are derived so that converter can operate at higher efficiency. In this converter the primary switches (MOSFET) are operated with Zero Voltage Switching (ZVS) and secondary switches (Diodes) with Zero Current Switching (ZCS) to have lower losses and hence to obtain higher efficiency. Finally the theoretical results are verified by simulating the converter in MATLAB1/SimulinkTM circuit Simulator. The results obtained from simulation clearly signify the controller performance for adjustment of output voltage in case of variation in input line voltage and output current through the load. If the above observations are looked closely then it clearly indicates that the controller is executing the functions of regulating the output voltage. Whenever there is any variations in input line and output load then the output voltage across the load is able to follow the reference signal.