Slope modulation in inverter circuits

Slope modulation is discussed as a means of voltage control in inverter circuits. The mark and space intervals of the pulse-width modulation (PWM) waveform are generated by controlling the slopes of a triangular carrier waveform. This slope modulation scheme, when implemented with a square-wave reference waveform and a constant volts/hertz ratio, produces a linear relationship between the fundamental frequency and the frequency ratio. The constant volts/hertz ratio is useful in such applications as variable-speed motor drives. The adopted three-phase PWM technique results in a constant current harmonic distortion at all frequencies.<>