Pulse Width Modulation correction Pulse Width Modulation (PWM) is a widely used technique to control the brightness of LEDs. It can be used to process the video signal and also to perform uniformity correction. PWM is used instead of varying the current because changing the current of the LEDs would also change the colors as explained above. PWM works by flashing the LEDs either full on or full off at a very high rate. The flashes are so fast that the human eye cannot notice them and the duration of the individual flashes (pulse width) determines the perceived brightness.