A practical method for achieving inductance cancellation in filter capacitors

Parasitic elements hidden into passive components and added by PCB tracks make the design of EMI filters a difficult task. Gaining control of such parasitic components can enhance the overall filter performance as well as improve the accuracy of the final attenuation prediction. In this paper, a practical method for achieving inductance cancellation in filter capacitors featuring high flexibility and, at the same time, high repeatability is proposed. Thanks to the complete shielding of the coreless coupled windings the cancellation effect is not affected by ground plane proximity, providing constant equivalent parameter values. Moreover, the shield can be helpful to reduce the mutual coupling between different components of the same filter, thus enhancing the overall filter attenuation. The effectiveness of the proposed approach is verified by extensive experimental tests.