Pulse width modulation (PWM) modulates the pulse width of a square-wave signal. The pulse width modulation method, which is used in controllers among other things, works with a constant pulse frequency and a constant pulse amplitude, only the pulse width is variable. Because the pulse frequency is constant, but the pulse width changes, the duty cycle changes.
Depending on the technical implementation, pulse width modulation works with a modulation signal or according to the comparator principle with edge control. In this principle, the linear amplitude rise of a sawtooth signal is compared with a variable comparison voltage and, if the voltage is equal, the output level of the comparator is switched over. If the reference voltage is changed, the switching time and thus the pulse width also changes.
Pulse width modulation is also known as pulse width or pulse duration modulation and is used in D/A converters, switching power supplies, telemetry, power electronics for controlling electric motors and dimmers, and also in optical transmitters, among other applications.