Power factor improvement and closed loop control of an AC-to-DC resonant converter

This paper presents the characteristics and dynamic performance of a modified series-parallel resonant converter (MSPRC) with a capacitive output filter and operating oil the utility line. The power factor of this converter is very high, even with no active control of the input line current. Fixed frequency control is used to regulate the magnitude of the output voltage and power. The sampled-data modelling technique of the MSPRC is used along with a small signal model to achieve excellent voltage regulation. The HF transformer nonidealities (i.e. leakage inductance and winding capacitance) are used as part of a resonant tank circuit. Thus, this converter is most suitable for high-voltage DC applications. Based on complex AC circuit analysis, the AC-to-DC MSPRC is designed for a 500 W, 1 kV output rating. Finally, simulation results are compared with experimental results.