Interesting twisted LED light (Patreon)

Published:

2023-11-01 09:18:27

Imported:

2023-11

Content

The best thing about reverse engineering this light was making sense of how a little extra dynamic current regulator allows lights like this to be dimmed, while using simple circuitry and standard existing components.

I reckon it is effectively rationing the charge to the main smoothing capacitor via the usual linear regulator, but then automatically adjusting the LED current down if it detects the current through them dipping too low. That allows it to regulate the LED current - and therefore intensity by the amount of charge put into the smoothing capacitor during the active area of the dimmer controlled sine wave.

https://www.youtube.com/watch?v=vThoHttAQd0

Files

Inside a twisted LED bulb

I chose this lamp to take apart because it has an interesting style. It's very similar to a fashionable (and expensive) designer compact fluorescent lamp called Plumen that was very popular with architects and designers because it "made a statement". This one is based on two shaped plastic tubes with two parallel flexible LED filaments running through them. Each filament is based on a flexible PCB strip with a series parallel array of LEDs to give a high operating voltage from one end of the strip to the other. That means they can use a fairly standard linear driver inside. There's another of those mysterious inline regulating chips to add an extra layer of current regulation to the LEDs. These seem common in dimmable lamps, and I think it's a way of regulating the LED current based on ripple from the current limited supply to the capacitor, that will be affected by the duty cycle of the dimmer output. It could be that the chip detects when the voltage across its internal sense resistor has dropped too low and then regulates the current down to the point it can maintain an acceptable level continuously, with its external capacitor acting as a simple analogue memory. If you enjoy these videos you can help support the channel with a dollar for coffee, cookies and random gadgets for disassembly at:- https://www.bigclive.com/coffee.htm This also keeps the channel independent of YouTube's algorithm quirks, allowing it to be a bit more dangerous and naughty. #ElectronicsCreators