Noise analysis of DC-AC random PWM schemes

Random pulsewidth modulation (RPWM) techniques for DC-AC power converters usually work well with high-sampling frequency. When RPWM schemes are implemented in digital signal processors (DSPs), the sampling frequency is limited by the speed of the processors. This paper analyzes the noise spectrum of various DSP-implemented RPWM techniques using a statistical approach. The relationship of the noise components and the sampling frequency for both the standard RPWM and the weighted RPWM methods is generalized. The dependency of the noise characteristics on various factors is calculated theoretically and verified experimentally. The generalized noise theory for randomized PWM switching provides useful practical guidelines to the choice of sampling frequency.