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How to make LED driver out of CFL components? Answered

I got some CFL parts like transformers, transistors, capacitors, etc. How do I make a (simple) LED driver to make an LED light bulb using the CFL components? I was thinking of a capacitive dropper power supply but the CFLs also had transformers so I could use those. Too bad the internet doesn't have much info of using CFL parts to make an LED bulb. Because when people get a CFL base to make an LED light bulb, they could just as well use the CFL PCB parts too.

If it helps, the two CFLs I took apart are a Commercial electric 14w reflector bulb and an (old) Lights of America 13w "The Bulb" bug light bulb.


I think you might have the parts there for a Joule thief.


since that, in its most simple form, used one NPN transistor, one resistor, one hand-wound 1:1 transformer, one LED, and one AA battery.

Or maybe you wanted to wanted to run this thing from mains power, rather than from a AA battery. I don't know what a "capacitive dropper power supply" is, but I am guessing maybe that means putting a capacitor in series with the mains for to limit the current.

I think I have seen that trick, the capacitor in series with the mains, inside of a plug-in LED nightlight, that I got from a local dollar store. On request, I can upload a picture and circuit diagram of this.

In summary, you might be able to build something that lights up an LED, but it won't be as nice as a real engineered LED driver.


3 years ago

For some reason the reply buttons on the comments don't work so I have to write a new comment.

@iceng & mplichfamily

I'm talking about the PARTS of the PCB, not the entire PCB itself. I already took all the components off and threw away the boards. I dont want to make an adapter to connect to an unmodified ballast, I want to use the ballast parts to make a whole power supply.

The parts include some metal film capacitors (or I think they are) so I wonder if I could use several of those wired in parallel to make a capacitor of a higher capacitance to power some LEDs.

Here's an article about capacitive dropper power supplies (aka transformerless power supply): http://www.electroschematics.com/5678/capacitor-po...

Thanks for the link. Now I see what you mean by capacitive dropper. It turns out that is pretty much the same the same circuit used in the dollar-store-LED-nightlight.

For anyone interested, pictures and circuit diagram of this nightlight are attached. This nightlight was sold in the Former United States, so it is intended for 120 VAC mains power, not 240 VAC as is used in other locations.


Hey! I have that exact night light as well as many other ones of different designs. They're from Dollar Tree. I opened one up once to see how it worked and I saw that big red blob thing and had no idea how it worked.

Here's a video of an LED corn bulb from eBay that uses a capacitive dropper.

Many cheap bulbs use capacitive dropper power supplies like this. The thing about capacitive dropper power supplies is that there is a direct connection to the mains, so any exposed connections on the LEDs, or whatever components are being powered, are live and should be handled with care as if it was a live mains wire.

This is no problem if the LEDs are sealed and cannot be touched, but it is dangerous in uses like those corn bulbs where there are SMD LEDs right on the surface. If you look on ebay and search for "led corn", most of the results would be for the newer versions with a plastic cover.

Oh the Reply buttons work again, so nevermind that.


3 years ago

When you look at CFL components you discover frequencies around 400 hertz at over 100 VAC while a 14 watt LED might use 4A at 3.3 VDC which would use a different step down transformer at 50 or 60 cycles and be much larger.

Yes you could use the high fq CFL xfmrs to reverse another cfl xfmr to lower voltage and rectify the output to DC BUT leds are current regulated devices and cfl does not have those.

In the result you will spend more money and lots of time when an eBay driver will do all you need for $3.


Nope. Doesn't work. CFL is taking mains power and converting it to the high voltage (thousands of volts) power needed to produce the plasma arch in the tube. An LED bulb needs to take mains power and convert it to a low voltage constant current DC power source. Basically an LED power source needs a rectifier, voltage regulator of some sort and a means to maintain a constant current. Exact needs of the supply will be determined by the LEDs you plan to use and how you would like to configure them.