Pulse Width Modulation (PWM)  Use of PWM as a switching
technique  Pulse Width Modulation (PWM) is a commonly used
technique for generally controlling DC power to an electrical
device, made practical by modern electronic power switches.
However it also finds its place in AC choppers. The average
value of current supplied to the load is controlled by the
switch position and duration of its state. If the On period of
the switch is longer compared to its off period, the load
receives comparatively higher power. Thus the PWM switching
frequency has to be faster.  Typically switching has to be done
several times a minute in an electric stove, 120 Hz in a lamp
dimmer, from few kilohertz (kHz) to tens of kHz for a motor
drive. Switching frequency for audio amplifiers and computer
power supplies is about ten to hundreds of kHz. The ratio of the
ON time to the time period of the pulse is known as duty cycle.
If the duty cycle is low, it implies low power.  The power loss
in the switching device is very low, due to alm