A closed-loop control of high power LLC Resonant Converter for DC-DC applications

This paper presents a new closed-loop control strategy applied to half-bridge high power LLC Resonant Converter applicable in DC-DC applications and can be applied for other applications also. A new control circuit is designed and implemented for the high power LLC converter. A closed-loop variable frequency control through VCO is analyzed through PI Controller. Due to Zero Voltage Switching (ZVS) technique the turn-on losses of both the switches (IGBTs) in half-bridge are reduced and ZVS can be achieved for the entire control range in close-loop. Validity of PI controller and control circuit in closed-loop are verified with software simulation results for wide input and load range. A hardware prototype rated at 2.1 kW has been built with DSP TMS320F2811 and hardware results are presented to verify the control strategy. Practical results with DC-DC converter match with the simulated results and performance of control circuit is verified and tested practically with input voltage variations and load changes at different references.