Hybrid spread spectrum modulation-based electromagnetic interference suppression of vehicle DC/DC converters

The phase-shifted full-bridge converter is often used as an on-board DC/DC converter because of its advantages of easy control and low loss. The use of a spread spectrum modulation technique can reduce the conducted common mode electromagnetic interference. However, the spectrum expansion of periodic pulse width modulation is not strong enough and is accompanied by spectral overlapping phenomenon in the high-frequency band. In addition, the chaotic pulse width modulation generates a large number of low-frequency components and the spectrum expansion is not controllable. In this paper, discrete chaotic sequences are used to modulate the modulation frequency of the periodic function for the second time to enhance the harmonic side-band extension capability of the periodic pulse width modulation, and to solve the problem of the accumulation of the low-frequency harmonic components caused by the chaotic pulse width modulation, and the introduction of the wide-band characteristics of the chaotic sequences can alleviate the overlapping phenomenon of the spectrum in the high-frequency band. Through the whale optimization algorithm, the relevant modulation parameters affecting the periodic-chaotic pulse width modulation–modulation frequency f_m and frequency extension range Δf are optimized. Finally, a 500W phase-shifted full-bridge converter experimental prototype verifies that period-chaos pulse-width modulation has better common mode EMI attenuation characteristics when compared with period pulse-width modulation and chaotic pulse-width modulation. In addition, it verifies the accuracy of the optimized parameters. The modulation means and optimization methods proposed in this paper can be used to reduce the conducted electromagnetic interference in switching power supplies.