Electromagnetic Interference Spectrum Steering Technique using Switching Angles Modulation in GaN DC-DC Converters

The fast switching speed of the GaN devices in DC-DC converters significantly increase the EMI noise in high frequencies. Passive and active EMI reduction techniques are usually applied in power converters to reduce the EMI noise. With no extra components, spectrum spread techniques becomes more and more popular in EMI noise reduction. Conventional spectrum spread techniques such as switching frequency modulation, averagely relocates the EMI energy near its switching frequency which is not always helping to reduce the EMI filter's size. By controlling the switching angles, the magnitude of the harmonics can be determined, and the EMI spectrum can be steered regarding to the EMI filter's attenuation performance. In this paper, it is proved that the rectangular waveform's harmonics energy is only related with average duty cycle and voltage level. By rearranging the harmonics magnitude with the optimized switching angles, the EMI filter size can be significantly reduced compared with the fixed switching frequency control. And compared with conventional spectrum spread techniques, the proposed technique can further reduce the EMI filter size and fully use the EMI filter's attenuation abilities.