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Re: Flyback Driver PCBs

Original poster: Matthew Smith <matt-at-kbc-dot-net.au> 

Kreso wrote:
 > I invite anybody to try my setup up. It will bring HUGE sparks.
 > 1. Get yourself a PC SMPS i used AT 200 W
 > 2. Toke the board out.
 > 3. Remove ferite cored transformer
 > 4. Connect flyback  primary to the points where primary of transformer
 > 5. Apply power

Jim Mitchell replied:
>Kreso I've tried that and the PSU just goes into protection and makes a 5mm
>spark at 2hz.

Matthew speculates (as an SMPS novice):

I'd guess that Jim's attempt may have been with a supply, the controller of 
which has switch current limiting.  To reproduce Kreso's results, you would 
need need a supply which relies on monitoring secondary voltage (normally 
feedback through opto-coupler) and no limiting of the switch current.  If 
no feedback were received (increase in secondary voltage regulates through 
decrease in switch pulse width), the unit could run "flat out", giving 
results as reported by Kreso.

I think that it's already been pointed out that most TV line-out 
transformers normally only see 115V or so.  A Computer supply is generally 
fed by a bridge rectifier, making the voltage available to the switch Vline 
/ (SQRT(2)/2).  I'm guessing that Kreso is in "220 Land", so his switch 
would be pumping:
(220/(sqrt(2)/2)-Vswitch_loss =roughly= 310V into transformer.  In "240 
Land", you're closer to 340V.

If considering this experiment, therefore, I would suggest using 
transformers that you don't mind getting "fried".



Matthew Smith
Kadina Business Consultancy
South Australia