EMI filter design for switching voltage regulator with improved thermal stability

Abstract

An EMI filter for the switching voltage regulator is presented not only to mitigate EMI noise, but also to improve thermal stability. This filter is composed of a resistor, ferrite bead, and also Zener diodes in parallel. Simulations, circuit probing, and far-field measurements are carefully carried out to demonstrate that voltage ringing is suppressed by 13 dB and EMI noise is reduced up to 10 dB. Infrared-red (IR) images are captured to show that this solution lowers the component temperature from 94 to 82 oC, bringing the circuit from critical temperature back to safe operation temperature.