In pulse-width modulation (PWM), duty cycle is a fundamental concept that describes the proportion of time a PWM signal remains in the "ON" state compared to the total period of one cycle. PWM is a technique used to control the amount of power delivered to a load (such as a motor, LED, or heater) by varying the duty cycle of the signal.
The PWM signal consists of two main states: "ON" and "OFF." During the "ON" state, the signal is at a high voltage level, representing full power. During the "OFF" state, the signal is at a low voltage level, representing zero power. The cycle is the total time it takes for the signal to repeat, and it is usually measured in microseconds (Ξs) or milliseconds (ms).
The duty cycle is expressed as a percentage or a fraction and represents the percentage of time the signal remains in the "ON" state during one complete cycle. It can be calculated using the following formula:
Duty Cycle (%) = (ON Time / Total Cycle Time) * 100
Where:
ON Time: The duration of the "ON" state during one cycle.
Total Cycle Time: The time for one complete cycle.
For example, let's say we have a PWM signal with a cycle time of 10 milliseconds (ms) and an ON time of 2 milliseconds (ms). To calculate the duty cycle:
Duty Cycle (%) = (2 ms / 10 ms) * 100 = 20%
A duty cycle of 20% means that the signal is ON for 20% of the cycle time and OFF for the remaining 80% of the time.
The duty cycle determines the average power delivered to the load. When the duty cycle is 100%, the signal is always ON, providing full power continuously. Conversely, when the duty cycle is 0%, the signal is always OFF, and the load receives no power.
By adjusting the duty cycle of the PWM signal, you can effectively control the power output to the load. This technique is commonly used in various applications, including motor speed control, LED brightness control, audio modulation, and many other scenarios where precise control over power delivery is required.