Duty cycle

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The duty cycle D is defined as the ratio between the pulse duration (

τ

) and the period (

Τ

) of a rectangular waveform

In telecommunications and electronics, 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.^[1] 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 $D = \frac{\tau}{\Tau} \,$

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 asquare wave is 0.5, or 50%.

In a continuously variable slope delta (CVSD) modulation converter, the mean proportion of binary "1" digits at the converter output in which each "1" indicates a run of a specified number of consecutive bits of the same polarity in the digital output signal.

Some music synthesizers vary the duty cycle of their audio-frequency oscillators to obtain a subtle effect on the tone colors. This technique is known as Pulse-width modulation (PWM).

[edit]Use of term in equipment

In tools/equipment such as welders, the maximum duty cycle is defined as the percentage of time in a 10 minute period that it can be operated continuously before overheating. ^[2] Duty cycle is the time that a signal(DC) is ON compared to its period. For example, let's say a DC signal of 1V starts at time t=0sec and stays there for t=2sec at which point the DC signal goes to 0V and stays there until t =10 sec. At time t = 10 the signal goes back 1V and the process repeats over and over again. Based on this analysis the signal is 1V for 0<t<2 and 0V for 2<t<10, therefore the Period T = 10sec. The duty cycle is then ON/Period of the signal i.e., 2/10 = .2 which gives a duty cycle of 20% SEE FIG. ABOVE.