you can dim LED that are running on DC (it requires more than a potentiometer i guess - probably a buck circuit controlled by a pot, though) or AC; i have scant idea how the AC ones work, although variacs have existed for a real long time; but you have to buy special LED bulbs that can handle being on a dimming circuit.
this is different than a bulb like hue etc that have the ability to dim themselves through whatever mechanism.
Traditional dimmers used TRIACs. Those don't dim LEDs well, they make very visible flicker. TRIACs turn the AC off for part of the waveform, essentially a very slow version of PWM. With an incandescent filament that flicker isn't as noticeable since it takes some time to cool down & stop glowing, which visibly smooths the flicker. It just stabilizies around a lower temperature. With LEDs, the turn-off is nearly instant. You visibly see the flicker at the AC mains frequency.
There are two ways to dim an LED: supply less current at the same voltage, or PWM dim it with a fast enough switching speed that you don't notice the flicker (this being slower than it needs to be is what the article is about). A current source is pretty easy to build, and doesn't flicker, but it does dissipate all the excess energy as heat. That's not what you want inside the dimmer switch in your wall, it can be quite a lot of heat and would be a fire hazard in such a confined area. It does work for things like photography lamps which can have exterior heat sinking.
> but it does dissipate all the excess energy as heat.
No. That's only true for a linear regulator, which is just one, very terrible, implementation of a current source that's only used for very low power applications. Linear regulators are never used for things like room illumination.
The alternative, and what's used for all commercially available DC LED drivers (plentiful and cheap), is to just use a regular AC->DC switching supply in current mode (current for feedback rather than voltage feedback). The only flicker is the ripple left in the filtered output.
Why aren't these used? Because most dimmer switches use tech from incandescent age, and just chop off parts of the AC sine wave, so the bulbs are designed around the switches you can buy in the store. Why do dimmer switches chop? Because that's what the bulbs you can buy at the store expect, sometimes damaging them if not dimmed as they expect.
You can buy in wall DC dimmer switches from any LED supply store, but they require DC lighting, also only found at LED supply stores. It's entirely a very recent momentum problem, that's slowly going away.
You're correct. You can't use a linear regulator for dimming. A current-mode switching DC/DC converter works, but needs sufficient filtering (or high enough switching frequency) to avoid the flicker issue.
Linear regulators are in fact used for room lighting, and efficiency can be reasonably good. Typical design is AC input -> bridge rectifier -> passive low-pass filter -> long string of LEDs with a single linear regulator in series. Voltage drop across the regulator is much lower than across the string of LEDs so there's not a whole lot of heat generated.
You can dim LEDs running on AC by converting to DC and then adjusting the current limit of the switching power supply. No flicker, but more expensive components.
this is different than a bulb like hue etc that have the ability to dim themselves through whatever mechanism.