Estimation of Optimum Value of Y-Capacitor for Reducing Emi in Switch Mode Power Supplies

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Milind M. Jha, Kunj Behari Naik, Shyama P. Das

Putting a Y-capacitor between the primary ground and secondary ground is a common practice in industry to reduce EMI; but, this capacitor increases touch current. A method is discussed to measure the touch current at circuit design level. An optimum value of Y-capacitor is predicted without exceeding touch current limit. Experimental results of touch current measurements and EMI measurements are analyzed.

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