Reduction of Conducted Perturbations in DC-DC Voltage Converters 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 Electro-Magnetic Interferences (EMI). In this paper, we propose a dual RPWM scheme for DC-DC voltage converters: the buck converter and the full bridge converter. This scheme is based on the comparison of deterministic reference signals (one signal for the buck converter and two signals for the full bridge converter) to a single triangular carrier having 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 for each converter. The EMC advantage of the proposed dual randomization scheme compared to the classical simple randomization schemes is clearly highlighted by the PSD analysis and confirmed by FFT (Fast Fourier Transform) analysis of the output voltage.