Effective filtering solution with low cost small size for common-mode reduction in dc–dc converters

An effective solution is introduced aimed to reduce the size and cost of electromagnetic interference (EMI) filters in dc–dc converters. This method is based on the insertion of small ground inductor (grounded through RF inductor). This technique is suitable for unshielded cables. The RF inductor prevent the return current of the common-mode (CM) noise at high frequencies, it is inserted between the earth ground (ground reference plane) and the chassis ground of the converter, therefore it isolate the converter chassis from power line ground at high frequencies. As well, maintaining the electrical safety grounding at the power frequency with very low impedance to ground. The efficiency of the proposed method is demonstrated by combining measurements and simulations for the fast testing. The level of CM current is compared versus a specific standard. This allows showing that the EMI emission levels can be reduced by as much as 30 dB.