> Trying to cram all the infrastructure for an LED lamp into the shape of a light bulb is a bad idea, even if the input power is DC.
Absolutely, the incandescent light bulbs have that shape for a reason: the screw is small because there is nothing to put in it and it doesn't heat, the bulb is large to dissipate all the light and heat it generates. And the LED light bulbs have exactly opposite problems: almost all of the heat is generated near the screw while the bulb itself generates almost none and the light-emitter doesn't even need the bulb that large around of it. Oh, and the casing around the screw is plastic so the thermal conductivity is horrible. Honestly, it's a profoundly terrible form-factor which we're now stuck with.
Absolutely, the incandescent light bulbs have that shape for a reason: the screw is small because there is nothing to put in it and it doesn't heat, the bulb is large to dissipate all the light and heat it generates. And the LED light bulbs have exactly opposite problems: almost all of the heat is generated near the screw while the bulb itself generates almost none and the light-emitter doesn't even need the bulb that large around of it. Oh, and the casing around the screw is plastic so the thermal conductivity is horrible. Honestly, it's a profoundly terrible form-factor which we're now stuck with.