Oznog said:
Certainly not. No transformer can ever create DC without a rectifier, no matter what you do with the primary.
Alright I'll be a bit more acurate doesn't create steady DC, it makes very small positive pulses and very large negitive pulses.
Try connecting the primary of a small mains transformer to an AA battey in series with a switch, connect a neon lamp to the secondary. When you hold the button the neon might flash very dimly as the field builds but it will flash even brighter when you release the button as the field collapses and notice the corrona is only generated around one electrode.
Oznog said:
Current in induced in the secondary winding when the mag flux changes. The mag flux increases when the primary transistor is on and creates current in the secondary.
True but not much current is generated as the field builds slowly.
Oznog said:
When the transistor is off, it decreases and makes current in the other direction.
When the transistor suddenly shuts off, the current in the primary decay more rapidly and generates a huge back EMF, it explains why you can generate 1kV from a 1:20 transformer with only 12V at the primary.
Oznog said:
when the transistor is on, flux increases rapidly making a high current spike on the output. Then it decreases at a more moderate rate when the transistor is off.
You've got that the wrong way round, the current increases slowly when the transistor turns on, remember inductors don't like sudden change in current and it's for this reason that a huge spike is generated when the transistor turns of; it's like turning a relay off.
Oznog said:
However, the core flux is always in the same direction. It increases and decreases but does not reverse
That's true in this case and it's why large negitive spikes are generated.
Oznog said:
, so the core is essentially biased at all times like an electromagnet.
It does turn off (minus the small current in the feedback).
Oznog said:
This reduces the capacity of the core.
No, it's because the core is only ever being magnetised with one polarity.
Oznog said:
Furthermore, if you do not allow enough time for the flux to be drained by the load during the "off" period, current will increase even higher the next "on" period and so on until the core flux reaches a saturation point. At that time the current during the "on" period is limited only by the total resistance in the primary circuit and will typically draw enough current to smoke.
That will only happen if the tube is disconnected.
Oznog said:
It is not a very appropriate design. He needs a split primary pretty badly.
Either way I agree.
But it does use pulsed DC, read the link I posted before. I've bought cheep DC fluorescent tube fittings before and one end of the tube always goes black and it doesn't illuminate uniformly