General > General Technical Chat
Mains voltage LEDs?
coppercone2:
I think the problem is overloads. When I had a overload that broke a bunch of things I measured a bunch of caps in like air conditioner and stuff, they were all severely reduced in capacitance. There is just not enough protection in houses and the grid. It's such a flimsy structure that I don't think its durable enough for the rough power grid. Still LED light seems to be doing better then CFL for now.
BadeBhaiya:
Maybe slightly related, I have seen a new kind of one of these mains LED boards.
These LED boards control the current though the LED string by using an in-series inductor and varying the switching frequency of the rectified mains though it. The switching part was an SO-8 and the reference current was set using a resistor
I don't remember the exact part number, but it was a Chinese one. Also I might be wrong and I just may have been unaware of their existence, and they are not new at all
Marco:
--- Quote from: BadeBhaiya on February 19, 2023, 05:57:16 pm ---These LED boards control the current though the LED string by using an in-series inductor and varying the switching frequency of the rectified mains though it. The switching part was an SO-8 and the reference current was set using a resistor
--- End quote ---
Probably some offline buck converter, without an electrolytic capacitor that's still going to flicker though.
I wonder why almost no one uses offline boost converters with LED strings. Just operate at poor efficiency and power factor low on the mains voltage. Minimal flicker, no electrolytic if you don't mind terrible PF.
tom66:
--- Quote from: Marco on February 19, 2023, 07:08:15 pm ---Probably some offline buck converter, without an electrolytic capacitor that's still going to flicker though.
I wonder why almost no one uses offline boost converters with LED strings. Just operate at poor efficiency and power factor low on the mains voltage. Minimal flicker, no electrolytic if you don't mind terrible PF.
--- End quote ---
It's probably cheaper to use a proper filter cap and a buck converter. The LED bulbs we have don't flicker.
Marco:
Thanks to the electrolytic it doesn't flicker, without the electrolytic you could increase reliability though. I doubt boost would increase cost over buck.
TI has been making the TPS92561 for a while, but the topology seems relatively rare.
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