Pulse Width Modulation (PWM)

What is PWM?


The PWM signal generally is generated by comparing a triangular wave signal with a DC signal it-self. The DC signal can range between the minimum and maximum of the voltages of the triangle wave. Once the triangle waveform voltage is greater than the DC level, the output of the op-amp slings high, and when it is lower, the output slings low. It can be seen that if the DC level increased higher, the pulses would get even thinner.

The average voltage supply to the motor depends on the duty ratio. Thus by controlling duty ratio (control width of time on), average output voltage can be control and the motor can be controlled. One way to obtain the PWM signal is by comparing the triangular signal with the control signal. Theoretically, the energy efficiency of this method is 100% where when switch is open, there is no current flow and when the switch is closed, there is no voltage across it results to zero power loss.