Conducted emission improvement of modern gate controlled devices

The paper deals with the problem of reducing conducted emissions of switched-mode power supplies using gate controlled devices such as IGBTs (insulated gate bipolar transistors) and power MOSFETs. The EMC problem is considered throughout the driving circuit design in order to meet the international conducted emission standards. In fact, addressing EMC in the design phase of the circuit is more cost effective than other alternatives. It is known that when compliance testing occurs at the end of the traditional product process there is a high probability that the final product fails to meet EMC objectives. The proposed strategy is to set the parameters of the driving circuit during the design starting from theoretical spectral analysis in order to comply with the EMC limits. The use of an original driving circuit, whose features were reported by C. Licitra et. al. (1992) and S. Musumeci et. al. (1993), is the way of reaching this goal. The circuit allows one to achieve the best EMC performances of the whole system without giving up on power losses reduction. This paper starts by reporting the design of the driving circuit. Firstly relationships between the derivatives of the current and the parameters of the circuit are shown, then such parameters are related to the Fourier series expansion coefficients. In the final part, experimental results of conducted emission tests are compared with theoretical spectra.