High Frequency Analysis of a Switching Mode Power Supply

In this paper, the electromagnetic fields radiated by a buck converter are calculated with a method based upon the Method of Moments (MoM). From the field line plots of the Poynting vector field, it is seen that DC power flows from voltage source to switch. There, the DC power is transformed into high frequency (HF) power. This HF power travels partially towards the diode where it is converted back into DC power which flows to the resistive load. This means that there exists a HF channel between switch and diode. In the second part of the paper, the conditions are derived to obtain a matching between the transmitter of high frequency power (switch) and the receiver (diode) at the different ends of the HF channel. The matching eliminates the radiation of energy at the switching frequency and its harmonics and therefore contributes to a better Electromagnetic Compatibility (EMC) performance.

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