General > General Technical Chat
Powering an LED from international line voltage
kenyonshutt:
Yo! I can’t believe I’m struggling with this, but I’m finding it really difficult to design a cheap circuit that can drive a 10-15mA LED, powered by a wide range of AC voltages (roughly 80-250VAC). It’s frustratingly challenging, given the fact that all kinds of products have “power present” indicators. That’s all I’m trying to do.
Some attempts:
* AC feeds LED directly thru a resistor (resistor needs to be super high wattage, LED brightness changes with voltage)
* Voltage divider with zener regulator (zener ends up conducting way too much current at high voltage
* wide voltage range LDO like onsemi NCP785AH50T1G (lots of components, this family is only rated to 10ma which isn’t quite bright enough
Sure I could add a friggin transformer or switching power supply but I literally just want the LED to turn on, at a predictable brightness, when the device is plugged into the wall.
Thoughts anyone? Thanks!!
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HackedFridgeMagnet:
Capacitive Dropper may suit.
NiHaoMike:
How about use multiple smaller LEDs in series? Then you'll need less current for the same brightness, possibly to the point where a series resistor would become practical.
mariush:
Single diode for half wave rectification, optionally a small capacitor to reduce flicker, a zener diode to cut off the voltage if it goes above around 200v DC or less (up to you where you want heat to be produced) , a HV linear current driver like CL220 (5v - 220v DC, 20mA out) : https://www.digikey.com/en/products/detail/microchip-technology/CL220K4-G/4902728
jonpaul:
Use any VDE/TUV /CE approved led driver, cost ~ EU 5..15 depending on the LED power, V, I.
We use the Italian TCI
Avoid the Chinese drivers
j
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