Formula & Calculator
PWM Duty Cycle to Average Voltage
Calculates the effective average voltage delivered by a PWM signal from its duty cycle and supply voltage.
Interpretation
V_avg = D × V_supply. Average voltage output from PWM signal is duty cycle times supply voltage. Used for motor speed and LED brightness control.
Variables
| Symbol | Quantity | Unit |
|---|---|---|
| V_avg | Average (effective) voltage | V |
| D | PWM duty cycle (fraction of time signal is on, 0 to 1) | |
| V_supply | Supply voltage | V |
What it means
Pulse Width Modulation (PWM) produces a signal that is on for a fraction D of the period (duty cycle). The average voltage seen by the load is the duty cycle times the supply voltage (assuming ideal switching). This is used to control DC motor speed and LED brightness. Understanding this is essential for power control applications.
Worked example
PWM Duty Cycle to Voltage – Two Detailed Examples
Real‑World| Parameter | Value |
|---|---|
| D (duty cycle) | 0.5 |
| V_supply (V) | 12 |
| Parameter | Value |
|---|---|
| D | 0.25 |
| V_supply | 5 |
Common mistakes
- PWM duty cycle to average voltage: V_avg = D × V_supply – where D is duty cycle (0‑1).
- D: The fraction of time the signal is high – 0.5 means 50% duty cycle.
- Units: V_avg in volts – same as V_supply.
- Assumes: Ideal switch and no losses – real circuits have voltage drops.
- Frequency: The PWM frequency must be high enough for filtering.
Applications
PWM duty cycle to average voltage, V_avg = D × V_supply, relates the average voltage applied to a load to the duty cycle (D) of a pulse‑width modulated signal. This is fundamental for controlling DC motors, LEDs, and heating elements. Engineers use it to set speed, brightness, or temperature by varying the duty cycle. By understanding this relation, they can implement open‑loop control or generate analog signals from digital outputs. This formula is used in motor drivers, lighting systems, and power converters. It is a basic but essential concept in embedded systems and power electronics.
- Motor speed control using PWM in robotics and automation
- LED dimming for display and lighting applications
- Power regulation in switching converters
- Heater control in temperature regulation systems
- Audio amplification (class D amplifiers)
Frequently Asked Questions
The average voltage is V_avg = D · V_supply, where D is the duty cycle (0 to 1) and V_supply is the supply voltage. This assumes the PWM signal is on for a fraction D of the period.
Using duty cycle as a percentage instead of converting it to a decimal fraction first, producing a result 100 times too large.
Duty cycle D = (on‑time) / (period). It is a value between 0 and 1. In percentage, it is D×100%.
V_avg = 0.5 × 5 = 2.5V.
The frequency does not affect the average voltage, but it affects the ripple and the ability to smooth the signal with a low‑pass filter. Higher frequency reduces ripple.
The peak voltage is V_supply (when the signal is on). The average voltage is lower.
Motor speed control, dimming LEDs, audio amplification, and power conversion.
D = V_avg / V_supply.
The load may affect the voltage due to resistance; the formula assumes an ideal voltage source and no load effects.
PWM is a digital signal with varying duty cycle; analog output is a continuous voltage. PWM is often filtered to produce an analog voltage.