T09.1 - Automatic Resonant Frequency Tracking for Primary-Side Regulation LLC Based on Magnetizing Current Cancellation

A novel primary-side regulation (PSR) scheme for LLC based on magnetizing current cancellation is presented. The transformer magnetizing current component on the sampling resistor can be offset by the compensating current, which generated by the auxiliary winding and the added compensating inductor. The effect of magnetizing current in the sampled primary resonant current can be effectively eliminated, so the accurate output current can be estimated on the primary side of the LLC resonant converter. Finally, a 24–48 V LLC prototype has been built up to verify the theoretical analysis.