Output rectifier analysis in parallel and series-parallel resonant converters with pure capacitive output filter

This paper analyzes the behavior of a pure capacitive output filter in parallel and series-parallel resonant converters. Unlike traditional resonant voltage-and current-driven rectifiers, pure capacitive output filters present interruptions in power transfer from the transformer primary to the secondary, owing to the existence of a parallel resonant capacitor. Therefore, existing formulas for different specifications of the output rectifier (e.g., output voltage ripple, efficiency, etc.) cannot be employed. This work provides detailed analysis of, and design equations for, pure capacitive output filters to cover the characteristic behavior of this rectifier. These valuable equations can be employed in the design of both low and high voltage power supplies for a variety of applications such as telecom power supplies and medical therapy instruments. Experimental results of a 10kVDC, 1.1kW power supply are presented to validate the analysis, along with other comparative experimental examples. With the rapid growth of low and high voltage applications, the equations will benefit researchers and R&D engineers in the area of resonant power conversion.