Variable Resonant and Magnetizing Inductor Control for LLC Resonant Converter

In this article, a variable resonant and magnetizing inductor based control strategy is proposed for LLC resonant converter. To reduce system components, the control circuitries for variable inductor and variable transformer are integrated as one. For single variable resonant inductor control, the controllable voltage gain range is restricted due to the magnetic core material. Thus, with both resonant and magnetizing inductor control, the voltage gain range can be extended to some extent. Meanwhile, due to the fixed switching frequency operation, the electro-magnetic interference (EMI) performance of the proposed converter is improved. Nevertheless, the disadvantage of the proposed control strategy is the power loss associated with variable inductor and transformer. Comparison between the frequency control, variable resonant inductor control and the proposed variable resonant and magnetizing inductor control is presented.