Duty Cycle

The duty cycle is the fraction of time that a system is in an "active" state. In particular, it is used in the following contexts:

Duty cycle is the proportion of time during which a component, device, or system is operated.Suppose a disk drive operates for 1 second, and is shut off for 99 seconds, then is run for 1 second again, and so on. The drive runs for one out of 100 seconds, or 1/100 of the time, and its duty cycle is therefore 1/100, or 1 percent.

In a periodic phenomenon, the ratio of the duration of the phenomenon in a given period to the period.

Duty cycle D = (τ/T)

where

τ is the duration that the function is active high (normally when the signal is greater than zero);
Τ is the period of the function.

For example, in an ideal pulse train (one having rectangular pulses), the duty cycle is the pulse duration divided by the pulse period. For a pulse train in which the pulse duration is 1 μs and the pulse period is 4 μs, the duty cycle is 0.25. The duty cycle of a square wave is 0.5, or 50%.

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