Pulse-width Modulation (PWM) is a term used to describe a digital output signal being sent to constant HIGH depending on the duty cycle and can be programmed to control different applications in a control circuitry. This same technology is being used to run the fan for your PC device you are using while reading this blog.
PWM is used in Siemens Variable Frequency Drives by converting the DC output of the drive to an AC signal using PWM.
In recent years, PWM technology has been used to cool your PC by sending pulses to the fan, (think about someone manually spinning the fan as needed), based on what the Duty Cycle is set at. For example at 10 percent duty cycle the fan would turn slowly and quietly, and at 80 percent duty cycle the fan would turn faster, until it has lowered the temperature of the device. Can you think of any other applications we could use PWM?