High frequency carrier digital PWM for Non-Sinusoidal modulating waveforms

The digital Pulse-Width Modulation (PWM) using High Frequency Carrier (HFCDPWM) gathers momentum with the utilization of high speed power switches such as power MOSFETs and IGBTs. An algorithm for generation of direct digital drive pulses for implementing various Non-Sinusoidal waveforms, specifically the raised sine wave, is presented. The implementation of various PWM schemes such as Sine-triangle PWM (SPWM), Space Vector PWM (SVPWM) by using microprocessor based pulse generator, employing a look-up table based algorithm, is discussed. An off-line look-up table generation proposed here for raised sine wave modulating signal, can be utilised to implement any type of modulating signals for carrier based modulation scheme. The proposed technique is compared with Regular Sampled PWM (RSPWM) and Sine Triangle PWM (SPWM) and the benefits of direct digital gating pulse generation over RSPWM and SPWM is emphasized. A pending patent application by the authors, describes the implementation of raised sine wave PWM modulation technique for induction motor drive applications.