Electronics people – how do these LED bulbs work?

These R7 bulbs usually get used in floodlights. We’ve got an uplighter than uses them. When I looked a few years back the LED replacements were bulky plastic “corncob” things with a load of individual LEDs on – I assumed the space in the wide bit was for the electronics to take 240v down to something the LEDs would run on.

The Uplighter has very limited space and I concluded they wouldn’t fit, and bought another Halogen (the last one in the house, but for a light that was almost never used). Now the lamp is being used, thebulb failed and I looked again and found these Phillips bulbs. Only available up to 900lm/60w equivalent but how do they work – theres clearly no space for any electronics in there?

These R7 bulbs usually get used in floodlights. We’ve got an uplighter than uses them. When I looked a few years back the LED replacements were bulky plastic “corncob” things with a load of individual LEDs on – I assumed the space in the wide bit was for the electronics to take 240v down to something the LEDs would run on.

The Uplighter has very limited space and I concluded they wouldn’t fit, and bought another Halogen (the last one in the house, but for a light that was almost never used). Now the lamp is being used, thebulb failed and I looked again and found these Phillips bulbs. Only available up to 900lm/60w equivalent but how do they work – theres clearly no space for any electronics in there?

not come across them in that form-factor before but they’re pretty common as “filament” style bulbs that look like vintage/retro bulbs

They’re basically tiny LEDs covered in phosphor-impregnated silicone which makes them glow. They can be a lot smaller as they’re filled with thermally-conductive gas which essentially means the outer glass acts as a heatsink, so a separate metal heatsink as you’d normally find on an LED chip is not required.

They will use something like chip on board devices to get into that form factor. Think tiny bits of semiconductor mounted onto the white board in the middle that use the orange material as a protective packaging.

This page probably describes it better than that:

https://siliconlightworks.com/resoures/what-are-cob-leds

@zilog6128

@bigginge

Ok – that gives me a much better understanding of COB, but I thought LEDs ran on low voltages (and ideally constant current rather than constant voltage). The base of a GU10 LED contains some circuitry to do this (and I’d assumed those filament led bulbs had it in the base somewhere) but there no space in these to hide anything like that.

Yes you are correct an individual LED typically runs on 3-5v, which is why conventional LED bulbs have electronics to convert 240v AC mains to something LED friendly. In a COB bulb there are a load of individual LEDs connected in series.