PWM Duty Cycle Calculator

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Calculate PWM duty cycle behavior including period, on-time, off-time, average voltage, RMS voltage, and approximate load power.

Input Parameters

PWM Frequency

Duty Cycle

High-Level Voltage

Load Resistance

Used only for approximate average and RMS power.

Results

PWM Period

On Time

Off Time

Average Voltage

RMS Voltage

Load Power Estimate

Design Note

Equations Used

Period = 1 / Frequency

Duty = Ton / Period × 100%

Average Voltage = Vhigh × Duty

RMS Voltage = Vhigh × √Duty

Resistive Load Power = Vrms² / Rload

Frequently Asked Questions (FAQ)

Q1: What is PWM duty cycle?
Duty cycle is the percentage of each switching period for which the PWM signal stays high.

Q2: Does PWM average voltage equal duty times voltage?
For an ideal 0-to-V signal, yes. Real loads may respond differently depending on filtering and dynamics.

Q3: Should motor power use average or RMS voltage?
For simple resistive heating, RMS is useful. Motors and inductive loads need more detailed models.

Q4: How do I calculate Ton and Toff?
Ton equals period times duty ratio. Toff equals period minus Ton.

Q5: Why does PWM frequency matter?
Frequency affects ripple, audible noise, switching losses, and how the load or filter responds.

Q6: Can this be used for LED dimming?
Yes, for timing and average-drive estimation, but LED current limiting and driver design must also be checked.

Disclaimer: This calculator assumes an ideal rectangular PWM waveform and a simple resistive load for power estimates. Real switching circuits may require driver losses, rise/fall time, inductance, filtering, and thermal analysis.

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