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How does an inverter look like? Answered

I happen to have a broken CFL lamp. I took it apart because i wanted to harvest the components that the electronic ballast contains.So how does a DC to AC CFL inverter look like?
And how can i use the transformer and the inverter in order to make an electric shocker(battery powered)?
Note that i also possess 2 other transformers from Kodak disposable cameras(one of them has 4 pins as the CFL's transformer and the other 5 pins)

Thanks in advance.



Best Answer 8 years ago

Just use the circuit you've got out of it, the HV outputs (to tube) should be fairly obvious to you.
And be careful...


You mean that i can connect a 9 volt battery directly to the circuit and the result will be an electric shocker?

Sorry if i misunderstood something but english is not my native language.

Maybe if you connected it in the right place. A camera-flash is probably better for you though.


Why would a CFL have an inverter?  It's getting AC directly from the wall.

They go to DC then power-up with a pulsed-DC electronic circuit. I could post a picture of one, but I'm not sure where I put it... Not strictly inversion, but you get the idea if you think "DC-fed CFL-driver".


Ah, thanks, Lemonie.  That seems oddly baroque, but I'm not an electrical engineer.

If you think "Why not just step-up mains to KV with a transformer?" you start thinking about "well that's going to be a fairly big lump in there". Perverse as it may seem, a diode or two and a dinky-inductor/transistor is more compact. Beyond "compact" - I don't understand the system well enough to give any other advantages...


Higher frequencies are easier to filter, with physically smaller parts.

Yes, that makes a lot of sense to me. I guess that's where the whining noise comes from when you hear it?


The basic story with switching power supplies is that you've got this little energy storage element, usually an inductor, that can store a quantity of energy Umax.  The maximum power you can feed through the supply is Umax times the switching frequency, or Pmax = f*Umax.  Also the volume and weight of the energy storage element tend to scale with Umax.

What this effectively means is that you want to run your switcher as fast as you can, so as to make the energy stored per cycle as small as possible, so you can use smaller, lighter components.  I mean there are also limits to how fast your switches can open and close, and of course at really high frequencies (MHz, GHz) everything looks like an antenna, and the power just wants to fly out into space.  Typical switcher frequencies are in the KHz, and compared to this the mains frequency of 50 or 60 Hz is glacially slow.  To do the same switcher-magic at that low of a frequency would require a bigger, heavier inductor for the energy storage, also bigger, heavier filter capacitors too.

Thanks (again), Jack!  That's a very clear theoretical explanation, which is good for me.  If I need concrete examples, I can borrow my lab engineer's textbooks.

Art of Electronics, by Horowitz and Hill - new edition due this year, but THE classic text. Win Hill is a very nice guy.

That's the one!  My mind was drawing a complete blank.  The only two-author text I could think of was Abramowitz and Stegun, which I knew was completely wrong.

"Hecht and Zajac" that'll get jammed in the old synapses now too !



Look here

Right.  Jack Lopez (below), helped clarify things a lot.  Your URL (linked here) has the right wording -- "two transistors connected as a high-frequency DC to AC inverter."  The key is that they are not actually an inverter, but are merely an oscillator, which serves the same purpose at sufficiently high frequencies.  That's the detail that I was missing, and which Jack, Steve, and Lemonie cleared up.

Its only getting 110V. The CFL needs very high voltages, so they use the electronics to step up the voltage, rectify 110V to ~150V DC, and then chop it all back up into a small transformer, it can be small because they chop at ultrasonic frequencies. Transformer size scales with frequency.