Spread spectrum in DC-DC full bridge voltage converter by a dual randomized PWM scheme

Randomized pulse width modulation (RPWM) deals better than deterministic PWM (DPWM) with electro-magnetic compatibility (EMC) standards for conducted electromagnetic interferences (EMI). In this paper, we propose a dual RPWM scheme for full bridge DC-DC voltage converter. This scheme is based on a triangular carrier with two randomized parameters. By using directly the randomized parameters of the carrier, a mathematical model of the power spectral density (PSD) of output voltage is developed. Then, the PSD analysis shows the EMC advantage of the proposed dual randomization scheme comparatively to the classical simple randomization schemes. Finally, FFT analysis confirms this advantage.