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Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
To drive a TV xfmr to insane levels, you don't need to use fancy topologies, a half-bridge of IRFPx60 (or newer equivalent) FETs is more than enought to pull a 20cm arc. Just be sure to set the running frequency right and avoid series resonances (tune the circuit with a small light-bulb in series and change the frequency until the bulb becomes the dimmest, but stay under ~50kHz.)
Registered Member #1749
Joined: Fri Oct 10 2008, 02:04AM
Location: Claremont New Hampshire
Posts: 497
Mike wrote ...
SLR means series load resonant topology. Steve describes it briefly here a quarter page down and also another site .
All I have to say is wow impresive.
Dr. Kilovolt wrote ...
To drive a TV xfmr to insane levels, you don't need to use fancy topologies, a half-bridge of IRFPx60 (or newer equivalent) FETs is more than enought to pull a 20cm arc. Just be sure to set the running frequency right and avoid series resonances (tune the circuit with a small light-bulb in series and change the frequency until the bulb becomes the dimmest, but stay under ~50kHz.)
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
Chris Cramer wrote ...
Light bulb what wattage?
I use 60W for testing and it glows just very dimly when tuned properly. An important thing I forgot to clarify, this is with open circuit output of course.
Registered Member #95
Joined: Thu Feb 09 2006, 04:57PM
Location: Norway
Posts: 1308
Chris Cramer wrote ...
Well can't you make your own on a bigger core and put it all in transformer oil and maybe the driver to?
Dude, have you looked at the previous work we've done here before? I did exactly what you describe not long ago. Or what about Jan, who has magnitudes of awesome videos of flyback abuse, doing things I never even thought possible with stock flybacks. Browse 'round a bit and see fer yerself, we'll provide you with details on the drivers if you want to know more.
Registered Member #1749
Joined: Fri Oct 10 2008, 02:04AM
Location: Claremont New Hampshire
Posts: 497
Uzzors wrote ...
Chris Cramer wrote ...
Well can't you make your own on a bigger core and put it all in transformer oil and maybe the driver to?
Dude, have you looked at the previous work we've done here before? I did exactly what you describe not long ago. Or what about Jan, who has magnitudes of awesome videos of flyback abuse, doing things I never even thought possible with stock flybacks. Browse 'round a bit and see fer yerself, we'll provide you with details on the drivers if you want to know more.
Thank you Uzzors. What components do you use to drive that beast or is it SLR topology? Would this 20A Variac be a good idea?
Registered Member #1749
Joined: Fri Oct 10 2008, 02:04AM
Location: Claremont New Hampshire
Posts: 497
Firefox wrote ...
I think once you pass the point (50-80Vin) when it is tough to keep paracitic oscillations out of the ZVS driver, the SLR topology becomes superior. While the ZVS flyback driver can pull massive currents at low voltages (tough with the SLR topo), limiting current draw becomes the problem at higher voltages, which the SLR topokogy does by nature.
Before I go making a full bridge resonant driver or SLR can I try to keep it ZVS because the other topologies are new to me. Can I use A MOT to get up to 50-80V at a good amount of current.
Registered Member #540
Joined: Mon Feb 19 2007, 07:49PM
Location: MIT
Posts: 969
You would have to change the tank values to increase the Q of the tank. Increase the inductance and decrease the tank capacitance. That should work fine.
I have had parasitic oscillations kill one of my MOSFETs once. It decided to go short and it drew about 50A at 24V. Luckily, the current was limited by the resistances of the wires and the internal resistance of the batteries. I don't know why my driver runs into parasitic oscillations at such low voltages though.
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
Myke wrote ...
I don't know why my driver runs into parasitic oscillations at such low voltages though.
This is because the conditions when the oscillations happen depend on many factors such as type and speed of transistors used, gate pullup resistors, etc.
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