PWM to Voltage Calculator

Convert PWM duty cycle to average output voltage

Result

Output Voltage (Vout): 6.000 V

Calculation: 12.00 × (50.0 / 100) = 6.000 V

Quick Reference

Supply Voltage

The maximum voltage (Vsupply) when PWM is at 100% duty cycle

Duty Cycle

Percentage of time the PWM signal is "on" during one cycle (0-100%)

Output Voltage

The average voltage (Vout) produced by the PWM signal

Formula

Where:

  • Vout is the average output voltage
  • Vsupply is the supply voltage
  • Duty Cycle is the percentage of time the PWM signal is high (0-100%)

What is PWM?

Pulse Width Modulation (PWM) is a technique for controlling the amount of power delivered to an electrical device. Instead of varying the voltage continuously, PWM rapidly switches the signal between its maximum and minimum values. The ratio of time spent in the "on" state versus the total period is called the duty cycle.

For example, if you have a 12V supply with a PWM signal at 50% duty cycle, the output will oscillate rapidly between 12V and 0V. The average voltage over a complete cycle will be 6V. This allows precise control of power delivery with minimal heat loss compared to linear voltage regulation.

Example Calculation

Scenario:

You have a 12V power supply and need to control an LED to 75% brightness using PWM.

Calculation:

Vout = 12V × (75 / 100) = 12V × 0.75 = 9V

The PWM signal needs a 75% duty cycle to produce an average voltage of 9V, which will drive the LED at 75% brightness.

Frequently Asked Questions

What is PWM (Pulse Width Modulation)?

PWM is a technique that encodes information in a pulsed signal. It works by rapidly switching a digital signal on and off. The ratio of on-time to off-time (duty cycle) determines the average voltage. PWM is commonly used in motor control, LED brightness adjustment, power supplies, and digital-to-analog conversion.

How does PWM work?

PWM switches between high (supply voltage) and low (0V) states at a high frequency. The percentage of time the signal is high is called the duty cycle. For example, a 50% duty cycle means the signal is high 50% of the time and low 50% of the time. The average voltage equals the supply voltage multiplied by the duty cycle percentage.

What is duty cycle?

Duty cycle is the percentage of time a PWM signal remains in the "on" state during one complete cycle. It's expressed as a percentage from 0% to 100%. A 0% duty cycle means the signal is always off, 50% means it's on half the time, and 100% means it's always on. The duty cycle directly proportional to the average output voltage.

What are common applications of PWM?

PWM has many applications including: DC motor speed control, LED brightness adjustment, power supply regulation, audio amplification (Class D amplifiers), switched-mode power supplies (SMPS), servo motor control, and fan speed regulation. It's used because it's efficient and allows precise analog control with digital signals.

What frequency is typically used for PWM?

PWM frequencies vary depending on the application. Audio PWM amplifiers typically use 100 kHz to 1 MHz. Motor control often uses 1-20 kHz. LED dimming might use 200-10,000 Hz. Higher frequencies are less audible and more efficient but require faster switching components.

How do I filter PWM to get true analog output?

To convert PWM to a smooth analog voltage, use a low-pass filter consisting of a resistor and capacitor (RC filter). The cutoff frequency should be much lower than the PWM frequency. The formula is: fc = 1 / (2π × R × C). A larger resistance or capacitance increases filtering but slows response time.

What is the difference between PWM frequency and duty cycle?

Frequency is how fast the PWM signal switches (number of on-off cycles per second), measured in Hz. Duty cycle is the percentage of time the signal is on during each cycle. Both affect the output, but duty cycle determines average voltage while frequency affects the smoothness and efficiency.

Pro Tips

  • • Always use a low-pass filter to smooth PWM output when you need a clean analog signal for sensitive applications like audio or precision control.
  • • Higher PWM frequencies are better for applications where you want to minimize audible noise (like motor speed control or LED dimming).
  • • When controlling inductive loads (motors, solenoids), use a freewheeling diode to protect the driving circuit from back EMF.
  • • PWM efficiency improves at higher duty cycles because transistors spend less time in transition, reducing switching losses.
  • • For accurate PWM to voltage conversion, ensure the filter has a cutoff frequency at least 10 times lower than the PWM frequency.
  • • In microcontroller applications, use built-in PWM hardware when possible instead of bit-banging PWM in software for better accuracy and reliability.

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