Design technique of coupled inductor filter for suppressing switching ripples in PWM converters

This paper proposes a design method of a coupled inductor filter for suppressing switching ripples in PWM converters. High attenuation performance in the ripples is achieved by adjusting positions of poles and zeros. The previous researches only focused on a double zero and a double pole, which determine notching and bandwidth frequencies of the filter. However, the proposed filter gives the increased attenuation in high frequency region by placing another double pole between bandwidth and notching frequencies. For this property, this paper proposes the design procedure of a coupled inductor filter. In addition, control strategies to find the resonance frequency and minimize the ripples are presented in the full paper. Furthermore, an uncoupled general form circuit, named LLC-LC filter is proposed as a filter topology.