Every LED has a rated current, which is the amount of current that needs to flow to get the
maximum light output. In a PWM driver, the current is switched at a high frequency between
0 and the rated output current. This means the LED load is either off or running at its rated
current. The ratio of on time to off time determines the LED brightness. See the following
diagram for an example of an LED that is dimmed to approximately 25% using PWM. The
25% level is a result of the current flowing for 25% of the time, then being turned off for the
remaining 75% of the time.