by Doug Coulter » Thu Nov 10, 2011 9:49 am
Most CCFL power supplies are quite inefficient - makes them cheaper, and when you're putting out real power yet still saving plenty over an incandescent, no sweat - the usual Generous Electric deal. Most of that power is wasted in ballasting the difference between strike and maintain voltage, and many off the shelf models just use a small series cap, the peak currents from which create I2R loss in other stuff in there.
Here the guy used a crazy big inductor for that - much more efficient, and to my eye, ran the lamp at bare minimum power. In a sense you could say that was resonant but it would be a very loose use of that word. Further I'd bet that he used a circuit that would produce constant current into the lamp over a wide range of input voltage. Then he puts in an enourmous bank (for this) of electrolytics (which he carefully doesn't mention the values of). There's your battery when there's no battery. And he claimed that those 18v worth of batteries weren't...yeah, right.
Going over to digikey, we can find 47,000 uF caps @ 6v the size he had, and how many did he have, 10 or so? Half a farad or thereabouts? (you can overvolt common new electrolytics for quite awhile before the failure rate goes up - what happens is eventually the capacity goes down as they re-form). Obviously he was not measuring the huge current during charging these - not a scope in sight. So, going to the old .5CV2 equation... we have .5*.5F * (being generous) 102 = 25 watt/seconds, or enough to run half a watt for 50 seconds - does it all add up now? If his 9v batteries were good, it'd have been 18 squared...a lot more joules.
Like Rossi's fusion, it's easy to fool people who *think* they are smart, till some boring guy comes along with a calculator...and knowledge of how to use it.
Remember in a thing with an LED, the caps are as small as they can be and the thing still work - capacity isn't cheap or small, and that turning off input power doesn't remove the device load other than the led from the caps, which is why they only stay up a second or so...
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.