Table of Contents
Pulse Width Modulation (PWM) is a technique used in embedded systems to control power delivery to devices such as motors, LEDs, and heaters. Calculating the duty cycle is essential for precise control of these devices. This guide provides a step-by-step process to determine the duty cycle in PWM-controlled applications.
Understanding PWM and Duty Cycle
The duty cycle represents the percentage of time the PWM signal stays high within one cycle. It directly influences the amount of power delivered to the load. A duty cycle of 50% means the signal is high half the time, while 100% means it is always high.
Calculating the Duty Cycle
To calculate the duty cycle, you need to know the desired output level and the PWM period. The basic formula is:
Duty Cycle (%) = (On Time / Total Period) × 100
Step-by-Step Calculation
- Determine the total period of the PWM signal, which is the inverse of the frequency.
- Decide the desired output level, expressed as a percentage.
- Calculate the on-time by multiplying the total period by the desired duty cycle percentage divided by 100.
- Use the formula to find the duty cycle if the on-time and period are known.
Example Calculation
Suppose you have a PWM frequency of 1 kHz, and you want a duty cycle of 75%. The total period is 1 ms (1000 μs). The on-time is:
On Time = 75% of 1 ms = 0.75 ms (750 μs)
This means the PWM signal should stay high for 750 μs and low for 250 μs in each cycle to achieve the desired duty cycle.