BTW, I don't understand why having the driver converting AC to DC inside the LED spots is the default. For a new house, it seems to make sense to me to have at least one external driver for a ceiling of spots, if not one per floor (not one for the whole house because pf the drop in voltage). But 24V led spots seem much less common and I cannot find many reviews. Any idea why it's not more common ? It seems efficiency and thermals would be much easier to optimize without the size constraint, plus economy of scale with components. Any specific 24V led spots / bulbs to recommend ?

In the UK having separate drivers is, or used to be, the most common set up. I never had good luck with it. Big problems with compatibility, failing drivers, especially with dimmers, plus weird electrical problems like residual glow.

> I don't understand why having the driver converting AC to DC inside the LED spots is the default.

because LED bulbs are drop-in replacement for incandescent bulbs. AC is pre-installed

stand-alone LEDs don't have converters, be it singular or be it strips

It seems like a pretty normal local maximum situation, no? It's a solution which works "well enough" and means all light bulbs work in all light fixtures and all light fixtures work with all light bulbs. It would be better if we all moved away from LED, got all new standardized 24V light fixtures and stopped putting the power supply in the base of a standard E26 light bulb socket, but those kinds of transitions are costly.

It probably also doesn't help that this would require industry-wide cooperation between companies which would much rather sell their own light fixture + LED combo which people have to replace regularly than a light fixture which people buy once and keep for life.

GU5.3 is 12V standard socket. Then there is G4 but they probably have some issues as well in wrong place. Probably some others, it really is a mess.

This is also a good solution to the flicker problem. Centralizing the conversion means you can afford better power filtering capacitors and circuit designs.

I notice most BR30/40 bulbs start to flicker after about a year in my fixtures. It's not a happy environment for an electrolytic capacitor. In the summer I guarantee we are out of the operational range of what is in those bulbs.

I expected the -48VDC telco standard to become popular as people had more solar, batteries, etc. I guess we will get there the most complicated way possible with usb-c.

It would be nice to have the driver and LED decoupled from each other with a standard socket between driver and LED even if there is one per bulb.

You can buy recessed LED cans with remote drivers. It’s not super common, but they exist in commercial installations. The largest LED drivers that I am familiar with are 24VDC/96w which is enough for (12) 8w recessed cans.

Individual drivers per fixture allow flexibility with regards to commercial lighting control. The 0-10V dimming signal is sent to the driver, and if you have multiple fixtures per driver, they will all dim together. This behavior can be accomplished with individual LED drivers by wiring the dimming signal in parallel to each driver from the dimming module.

Line voltage circuits can handle a lot of fixtures, particularly at 230V or 277V. A 277V 20A circuit can continuously power 554 8w recessed cans or 138 32w 2x4s on a single pair of #12/2.5mm^2 wire. Two of those circuits can power all of the lights in a 20,000 square foot office.