Reduction of radiated electromagnetic interference in 4-phases pulse width modulation converter system

Radiated electromagnetic interference (EMI) in pulse width modulation (PWM) converter system is analyzed using discrete time Fourier series (DTFS) and a snubber circuit. The causes of radiated EMI are found through DTFS analysis of output waveform of switched voltage. By designing a snubber circuit with resistor (R) and capacitor (C) filter, overshoot and ringing of switched voltage are suppressed and the EMI is also reduced. The important factors are to minimize peak voltage and to reduce power dissipation in selecting of RC value. The design of snubber circuit is considered these points and measured EMI shows the improvement of 6 dBuV/m.