An Interleaved PFM LLC Resonant Converter With Phase-Shift Compensation

The interleaved structure of LLC resonant converter with the phase-shift modulation (PSM) is presented and then its optimum operating region is discussed. The LLC resonant converters can achieve zero-voltage switching (ZVS) of the primary switches and zero-current switching (ZCS) of the secondary switches. However, the secondary peak current is large due to the discontinuous conduction mode (DCM). The interleaved PFM LLC resonant converter has difficulty in synchronizing switching instants among phases owing to the parameter mismatch of resonant circuits. In the proposed method, the current unbalance caused by the parameter mismatch is compensated by PSM. It is confirmed that the proposed method achieves lower peak current even when there is parameter mismatch and that the operation of below resonant frequency is suitable, both of which are simulated and experimentally verified.