A Family of Spread-Spectrum Modulation Schemes Based on Distribution Characteristics to Reduce Conducted EMI for Power Electronics Converters

Spread-spectrum modulation strategy is recognized as an effective solution to reduce conducted electromagnetic interference (EMI). This article proposes a family of spread-spectrum modulation strategies that can effectively reduce the conducted EMI for power electronics converters. The introduced modulation strategies eliminate the noise spikes in conducted EMI spectrum, reducing the harsh requirements for designing EMI filters. The proposed spread-spectrum methods are based on the distribution characteristic of switching frequency, which determine the waveform function of switching frequency. In addition, the design principles take reduced switching losses and fixed variation range of switching frequency into consideration. The differential equation that makes the switching frequency subject to arbitrary statistical distribution is derived in detail together with the corresponding solutions. Three typical statistical distributions represented by uniform distribution, exponential distribution and normal distribution are performed. Relevant experiments have verified that the proposed spread-spectrum modulation schemes can reduce the conducted EMI about 20 dB. Finally, several other typical spread-spectrum modulation schemes such as random pulsewidth modulation (PWM), periodic PWM, and programmed PWM are implemented in converters for comprehensive comparison to evaluate the proposed spread-spectrum modulation schemes.