PWM Voltage Calculator Formula
Understand the math behind the pwm voltage calculator. Each variable explained with a worked example.
Formulas Used
Average Voltage
v_avg = v_peak * duty_cycle_pct / 100RMS Voltage
v_rms = v_peak * sqrt(duty_cycle_pct / 100)Power Ratio vs DC
power_ratio = duty_cycle_pctVariables
| Variable | Description | Default |
|---|---|---|
v_peak | Peak Voltage (Logic High)(V) | 3.3 |
duty_cycle_pct | Duty Cycle(%) | 75 |
How It Works
PWM Average Voltage
A PWM signal with fixed amplitude and variable duty cycle produces an average voltage proportional to the duty cycle.
Formulas
V_avg = V_peak x Duty Cycle
V_rms = V_peak x sqrt(Duty Cycle)
When filtered through a low-pass filter, the PWM signal approximates a DC voltage equal to V_avg. This principle drives motor controllers, dimmers, and digital-to-analog conversion.
Worked Example
3.3 V logic level at 75% duty cycle.
- 01Average voltage: 3.3 x 0.75 = 2.475 V
- 02RMS voltage: 3.3 x sqrt(0.75) = 3.3 x 0.866 = 2.858 V
- 03Power is 75% of continuous DC
Frequently Asked Questions
Is PWM average the same as a true DC voltage?
After filtering, yes. The ripple depends on filter design and PWM frequency. Higher frequency allows smaller filters.
Why use PWM instead of a voltage regulator?
PWM switching is very efficient (95%+) because the transistor is either fully on or off. Linear regulators waste power as heat.
What PWM frequency should I use?
For LEDs: 200+ Hz to avoid flicker. For motors: 1-20 kHz. For audio: 40+ kHz (above hearing range).
Ready to run the numbers?
Open PWM Voltage Calculator