A Novel PWM Technique in Digital Control

One problem with microprocessor-based high-frequency pulsewidth-modulation (PWM) converters is the modulating resolution limitation caused by limited-time resolution of hardware timers. In this paper, a novel PWM technique, the double PWM (DPWM), is proposed. DPWM combines the advantages of low-frequency modulation and high-frequency switching in power conversion and resolves the contradiction between high frequency and accuracy in a digital control scheme. DPWM effectively increases the resolution in digital control, while the harmonics introduced by this method is found to be negligible. Theoretical analysis, characteristics, and design considerations are given, and they are verified by experiments on a 5.5-kW 20-kHz insulated-gate-bipolar-transistor boost-buck converter