Design and measurement of μA leakage current EMI filter

In this paper, a re-design of low power single-phase EMI filter where less than 100 μA of leakage current as per UL 1206-1 standards will be presented. The recent current limit is more stringent for medical applications than the others. Hence there is need to revisit the EMI filter design. The two Y capacitors are the major contributors to the leakage current due to the equivalent series resistor (ESR). The three-Y capacitors are suggested for the strategy. The experimental data indicates that low leakage current is achieved and the filter provides an average of 67 dB insertion loss in the 150 kHz to 30 MHz band. Mutual coupling is investigated but it does not contribute to the leakage current at low power.