Characteristics of a fixed-frequency series-parallel resonant converter operating on the utility line with and without active control

A single-phase high-frequency transformer-isolated ac-to-dc controlled rectifier using a fixed-frequency series-parallel (or LCC-type) resonant converter (SPRC) is presented. A simple analysis and design procedure is used for designing the converter for low line-current harmonic distortion and high power-factor (PF) operation. The converter performance characteristics have been verified with SPICE simulations and an experimental prototype SPRC, without using active control. These results show that, although no active control is used, the converter operates with a line-current total harmonic distortion (THD) of 13.5% at full load and 23.6% at half load, with line PF > 0.97. Active control has also been implemented in the experimental prototype to achieve a line PF > 0.99 with a THD of < 16%, for variation in supply voltage and load (full load to half load).