Conducted noise compliance through good filter design

The personal computer is becoming an important item for the domestic and industrial sector. Computing devices need good regulated power supplies. Power supply could be linear or switching. But due to certain advantages of SMPS, it is preferred for usage in all computing devices. Yet compared to a linear power supply, SMPS generates higher EMI noise because of switching devices. This noise may affect the performance of products in the vicinity. To suppress these noises a low pass filter is used. The design of an EMI filter for SMPS depends upon a lot of factors such as impedance of filter, frequency of emitted noise/fundamental frequency and suppression requirements. This paper describes the techniques for design of filter for compliance purposes and throws light over comparison of the theoretical values with reference to practical suppression.