Pulse-width modulation: Meaning (information, definition, explanation, facts)

Pulse-width modulation is a way to represent data over a communications channel. With pulse-width modulation, the value of a sample of data is represented by the length of a pulse.

Pulses of various lengths (the information itself) will be sent at regular intervals (the carrier frequency of the modulation).

_ _ _ _ _ _ _ _ | | | | | | | | | | | | | | | | Clock | | | | | | | | | | | | | | | | __| |____| |____| |____| |____| |____| |____| |____| |____

_ __ ____ ____ _ Data | | | | | | | | | | | | | | | | | | | | _________| |____| |___| |________| |_| |___________

Data 0 1 2 4 0 4 1 0

The clock signal is not necessary as the leading edge of the data signal can be used as the clock if a small offset is added to the data value in order to avoid the lack of a pulse for zero values.

PWM is also used to vary the total amount of power delivered to a load without resistive waste. An RC filter can be used to smooth the pulse train into a steady analog voltage. This method is commonly used in DC motor speed control.

See also:

• Modulation
• Pulse-code modulation
• Pulse-amplitude modulation
• Pulse-density modulation
• Pulse-position modulation