Comparison of three different modulators for Power Converters with respect to EMI optimization

Switch-mode power converters are well known for emissions in the band of electromagnetic interference (EMI) interest. The spectrum shape depends on the type of modulator and its purpose. This paper gives design guidelines to choose the optimum topology depending on requirements of different applications. Spectral measurements on prototypes of a pulse width modulator (PWM), a DeltaSigma-modulator and a hysteretic self-oscillating modulator are shown, which are verifying their simulations, with respect to different EMI challenges.