These are commonly used for direct current (DC) motor control in robotics and other applications. In electronics, many modern microcontrollers (MCUs) integrate PWM controllers exposed to external pins as peripheral devices under firmware control by means of internal programming interfaces. PWM has also been used in certain communication systems where its duty cycle has been used to convey information over a communications channel. PWM also works well with digital controls, which, because of their on/off nature, can easily set the needed duty cycle. Power loss, being the product of voltage and current, is thus in both cases close to zero. When a switch is off there is practically no current, and when it is on and power is being transferred to the load, there is almost no voltage drop across the switch. The main advantage of PWM is that power loss in the switching devices is very low. For example, switching has to be done several times a minute in an electric stove 100 or 120 Hz (double of the utility frequency) in a lamp dimmer between a few kilohertz (kHz) and tens of kHz for a motor drive and well into the tens or hundreds of kHz in audio amplifiers and computer power supplies. The rate (or frequency) at which the power supply must switch can vary greatly depending on load and application. The PWM switching frequency has to be high enough not to affect the load, which is to say that the resultant waveform perceived by the load must be as smooth as possible. PWM is particularly suited for running inertial loads such as motors, which are not as easily affected by this discrete switching, because their inertia causes them to react slowly. Along with maximum power point tracking (MPPT), it is one of the primary methods of reducing the output of solar panels to that which can be utilized by a battery. The longer the switch is on compared to the off periods, the higher the total power supplied to the load.
The average value of voltage (and current) fed to the load is controlled by turning the switch between supply and load on and off at a fast rate. Pulse-width modulation ( PWM), or pulse-duration modulation ( PDM), is a method of reducing the average power delivered by an electrical signal, by effectively chopping it up into discrete parts.
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