PWM Calculator
Calculate PWM period, on/off times, and average voltage from frequency and duty cycle — or find the duty cycle needed to achieve a target average voltage.
PWM Parameters
%
V
Results
Period (T)1.000 ms
tON500.0 µs
tOFF500.0 µs
Average voltage (Vavg)2.500 V
Vavg = Vpeak × D/100
Common PWM Frequencies by Application
| Application | Typical Frequency |
|---|---|
| DC motor speed control | 1–20 kHz |
| Servo motor control | 50 Hz |
| LED dimming | 100 Hz – 20 kHz |
| Switching power supply | 20 kHz – 2 MHz |
| Class D audio amplifier | 40 – 400 kHz |
| Piezo buzzer tone | 1 – 20 kHz |
How PWM Works
Pulse-Width Modulation (PWM) is a technique for encoding analog information in a digital signal by varying the fraction of time the signal is high (the duty cycle). The average voltage seen by the load equals the peak voltage multiplied by the duty cycle.
A low-pass filter on the output converts the PWM waveform to a true DC analog voltage equal to Vavg. Without a filter, the load itself may integrate the switching (e.g., a motor's inductance or an LED's phosphor persistence).
Average Voltage
Vavg = Vpeak × D / 100Period and Timing
T = 1 / f | tON = T × D/100Key Points
- Higher frequency: smoother output but higher switching losses
- D = 0% = always off; D = 100% = always on
- Motor control: higher frequency reduces audible noise (>20 kHz)
- Servos use 50 Hz with 1–2 ms pulse width to encode angle
- LED dimming: >100 Hz prevents visible flicker
- PWM resolution: an N-bit timer gives 2ᴺ steps of duty cycle
Applications
- Motor speed and direction control
- LED brightness dimming
- Servo position control
- Switching power supply duty cycle
- DAC via RC low-pass filter