Editing Pulse-width modulation (section)

==== Time proportioning ====
Many digital circuits can generate PWM signals (e.g., many [[microcontrollers]] have PWM outputs). They normally use a [[counter (digital)|counter]] that increments periodically (it is connected directly or indirectly to the [[clock signal|clock]] of the circuit) and is reset at the end of every period of the PWM. When the counter value is more than the reference value, the PWM output changes state from high to low (or low to high).<ref>{{cite web |last=Barr |first=Michael |date=1 September 2001 |title=Introduction to Pulse Width Modulation (PWM) |url=https://barrgroup.com/Embedded-Systems/How-To/PWM-Pulse-Width-Modulation |website=Barr Group}}</ref> This technique is referred to as '''time proportioning,''' particularly as '''time-proportioning control'''<ref>''Fundamentals of HVAC Control Systems,'' by Robert McDowall, [https://books.google.com/books?id=UMk1EUp-W-UC&pg=PA21&dq=%22time+proportioning%22 p. 21]</ref> – which ''proportion'' of a fixed cycle time is spent in the high state.

The incremented and periodically reset counter is the discrete version of the intersecting method's sawtooth. The analog comparator of the intersecting method becomes a simple integer comparison between the current counter value and the digital (possibly digitized) reference value. The duty cycle can only be varied in discrete steps, as a function of the counter resolution. However, a high-resolution counter can provide quite satisfactory performance.