Study on EMI suppression of a high-low voltage DC/DC converter in electric vehicle by periodic frequency modulation

The high-low voltage DC/DC converter of electric vehicle produces high du/dt and di/dt due to the high operating frequency of the power devices, which introduce nonnegligible electromagnetic interference. In this paper, the power devices control signals of the high-low voltage DC/DC converter were modulated by periodic signals, the influence of the modulation frequency, the maximum frequency deviation and the modulation waveform on the conducted electromagnetic interference were analyzed. Combined with the published data of the phase-shifted full-bridge circuit of the high-low voltage DC/DC converter, the spread-spectrum modulation control signal model and power circuit model were established in MATLAB/Simulink and PSIM, and co-simulations were carried out with different modulation parameters. The interference suppression effects of three test frequency bands required by CISPR 25 were tested; the optimal parameters for the periodic frequency modulation of the high-low voltage DC/DC converter in electric vehicle were proposed.