Comment by DoctorOetker
1 day ago
I don't believe LED-pixel displays use PWM. I would expect them to use bit planes: for each pixel transform the gamma-compressed intensity to the linear photon-proportional domain. Represent the linear intensity as a binary number. Start with the most significant bit, and all pixels with that bit get a current pulse, then for the next bitplane all the pixels having the 2nd bit set are turned on with half that current for the same duration, each progressive bitplane sending half as much current per pixel. After the least significant bitplane has been lit each pixel location has emitted a total number of photons proportional to what was requested in the linear domain.
So for an 8bit color display you have 24 lines of various currents going across each row (or column) of pixels?
There are more efficient ways of achieving this, but you certainly don't need a separate conductor for each bitplane, but obviously you need separate strings for each color channel.
So to ignore the colorwise overhead lets pretend we just have a single color channel.
You could even arrange all LED's in series and short out (bypass with mosfet) those LED's that should NOT be lit.
Then you can just energize an inductor until the appropriate current is reached and then flash a certain amount of charge through the LED string.
One can choose between reusing the same inductor for the different currents or having separate inductors each for their own current levels.
It would require bypass transistors for each LED, but there are support electronics for each LCD pixel too, as a comparison.
The 24-bit color display (3x8) would actually result in many more bit planes after gamma deflating to the linear photon proportional domain.