Creation of Spread Spectrum in Power Converters by Combining the Possible Random Variations of PWM Parameters

Randomization PWM parameters in power converters originates a spreading of the emission spectrum, achieving a reduction in the amplitudes of the strong electromagnetic emission peaks generated in the switching, thus mitigating electromagnetic interference (EMI). In this study, all forms of PWM parameter variation by means of randomization are developed with the aim of broadening the spectrum. A total of 31 diversification possibilities are developed giving rise to different methods of spread spectrum creation. In the process of studying all combinations, new randomization methods not previously included in the literature have emerged. The emission decrease in each method is measured and quantified with respect to the highest emission peak produced, which corresponds to constant PWM. The reductions achieved in some of the randomization methods are very significant. For emission measurements and quantifications, a DC-DC Buck converter has been used to feed a high illumination LED lamp. The confection of each randomization mode is implemented with a low performance FPGA development board and VHDL hardware description language. The results obtained from the measurement of each method are compared with the others, highlighting those methods more suitable to be included in power converters to reduce electromagnetic interference.