New design and implementation of an external passive circuit for cancelling the parasitic capacitance in filter inductors

This paper presents a new technique consisting of an additional passive component and a small capacitor to cancel out the effect of parasitic capacitance, thereby improving high frequency filtering performance. The proposed method is related to strategy that has been exploited for cancelling parasitic capacitance in filter inductors. In this technique an extra winding is wound together with the main inductor on the same core to form coupled magnetic windings in a center-tapped connection. This structure of coupled windings and compensating capacitor can eject capacitive current of the main inductor. Simple circuit relationships between the windings turn ratio, its parasitic capacitance and the compensating capacitor are written. By these relationships and proposed design in this paper, we could obtain the optimized values for windings turn ratio and the value of compensating capacitor. Effects of the main parameters such as coupling coefficient, turn ratio and type of the core material are considered and simulated by PSIM software. Also experimental results confirm the proposed technique.