2 ms·
Transistors are much more efficient full on or full off. So for the most part for transistor based voltage control they pulse the transistors with a duty cycle
by somat 5mo ago
Transistors are much more efficient full on or full off. So for the most part for transistor based voltage control they pulse the transistors with a duty cycle equivalent to the voltage needed and integrate it with capacitors, keep the pulse on 25% of the time you have 25% of the voltage sort of thing. Thus the acronym PWM (Pulse Width Modulation)
Note that transistors can be controlled to directly regulate the voltage. This will draw much more power than pulsing them.
It is also kind of neat how voltage is measured. Probably day one stuff in EE school but I thought it was interesting. Meters like the one in the article are sort of obvious. pull a spring with an electromagnet and see how far it gets. but how is voltage read electronically. The answer is capacitors. you time how fast a capacitor charges.
- magicalhippo 5mo agoEssentially how a Class D amplifier[1] works, and part of the reason you can get so much sound out of tiny portable speakers for so long. [1]: https://en.wikipedia.org/wiki/Class-D_amplifier https://en.wikipedia.org/wiki/Class-D_amplifier
- xxs 5mo agoPWM is used in pretty much everything. Any power supply, any voltage regulation (A cpu has multiple voltages, e.g. core, SoC, cache,), most LED brightness control, lots of motor speed controls and so on. Like mentioned transistor (esp FETs) like to be fully open or fully closed. Class-D amplifier requires to convert the naturally analog signal, unlike say a power supply that has a voltage ref. on/off, with sampling 1st. It makes it for a relatively poor example of PWM use.