Why do we use PWM control?

With linear control the pass element (usually some sort of transistor) has to dissipate the unused power. It dissipates the most at the one

1/2 power point. An ideal pass element dissipates no power when it is full on. So if instead of turning it on at half power all the time you turn it on at full power for 1/2 of the time, then you don=92t have to dissipate any power in your pass element. (ideally). This assumes that your load doesn=92t mind having the power turned on and off=85 which is the case for lots of things.

George H.

Two main reasons that I can think of:

1)The transistor that controls the current is either full-on or full-off. That means that the power/heat dissipated by the transistor itself is minimal. In a linear circuit, at 50% speed, the motor and transistor dissipate half the power each.

2)PWM provides better torque at low speed; the motor pushes hard for the brief periods it's on.

I hope that makes sense! :)

I don't understand the question. "DAC" means digital-to-analog converter, and "PWM" means pulse width modulation, which IS, often, exactly a digital-to-analog conversion scheme. So, PWM overlaps with DAC. It isn't an either-or comparison here, at all!