What Does Pulse Width Modulation (PWM) Mean?
Pulse-width modulation (PWM) is a modulation process or technique used in most communication systems for encoding the amplitude of a signal right into a pulse width or duration of another signal, usually a carrier signal, for transmission. Although pwm controller is also used in communications, its main purpose is actually to control the power that is supplied to various types of electrical devices, most especially to inertial loads such as AC/DC motors.
Techopedia Explains Pulse Width Modulation (PWM)
Pulse-width modulation (PWM) is used for controlling the amplitude of digital signals in order to control devices and applications requiring power or electricity. It essentially controls the amount of power, in the perspective of the voltage component, that is given to a device by cycling the on-and-off phases of a digital signal quickly and varying the width of the "on" phase or duty cycle. To the device, this would appear as a steady power input with an average voltage value, which is the result of the percentage of the on time. The duty cycle is expressed as the percentage of being fully (100%) on.
A very powerful benefit of PWM is that power loss is very minimal. Compared to regulating power levels using an analog potentiometer to limit the power output by essentially choking the electrical pathway, thereby resulting in power loss as heat, PWM actually turns off the power output rather than limits it. Applications range from controlling DC motors and light dimming to heating elements.
Frequency of a PWM
The frequency of a PWM signal determines how fast a PWM completes one period. One Period is the complete ON and OFF time of a PWM signal as shown in the above figure. The formulae to calculate the Frequency is given below
Frequency = 1/Time Period
Time Period = On time + Off time
Normally the PWM signals generated by microcontroller will be around 500 Hz, such high frequencies will be used in high speed switching devices like inverters or converters. But not all applications require high frequency. For example, to control a servo motor we need to produce PWM signals with 50Hz frequency, so the frequency of a PWM signal is also controllable by program for all microcontrollers.
Some commonly arising questions on PWM
What is the difference between the Duty cycle and Frequency of a PWM signal?
The duty cycle and frequency of a PWM signals are often confused upon. As we know a PWM signal is a square wave with a particular on time and off time. The sum of this on time and off time is called as one time period. The inverse of one time period is called frequency. While the amount of time the PWM signal should remain on in one time period is decide by Duty cycle of the PWM.
To put it simple, how fast the PWM signal should turn on and turn off is decided by the frequency of the PWM signal and in that speed how long the PWM signal should remain turned on is decided by the duty cycle of the PWM signal.
