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Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
Mestre Racerxdl wrote ...
Thanks for the help :), in all, i have tested the mosfets here, all is working, i have 12 here :P
And the performance is incredible better, i have tested one with a 100kHz Oscilator and a Coil from a Plasma Globe (the smaller than Flyback ones), and I get incredible 4cm Sparks with only 24V. (Versus 2cm sparks with a MJE13007 Bipolar)
I suppose you have a transformer with ferrite core, that's not a Tesla coil. Tesla coil is an air cored resonant transformer.
Registered Member #89
Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145
Hi guys
I wondered about some things here, it's all about bridge design, CW SSTC with BJT's;
1. I can use a current transformer or feedback loops to sense the secondary current, but I fear it won't be reliable enough. Coupling would need to be precisely configured in order to acheive best of current-proportional drive. Am I right?
2. I wonder if there is anything that would prevent me from simply sensing the primary current, usng a single CT in 'true' proportional-current drive mode?
With enough coupling the primary current will track secondary current allowing oscillation, and transistors will always have assured class C operation with minimal losses.
3. If 2 fails for any reason I could use a current transformer with 'steer' windings just like hard switched designs in PC power supplies.
Then I would take feedback from secondary base and drive the PCD transformer via two diodes. (I don't know how much sense does that make). That would basically be like replacing the TL494 with base-feedback current transformer and I don't see why wouldn't it work.
4. I believe bipolars can match mosfets in performance with proper driving tecchnique. With PCD, the charge actually starts draining off the base just as the current passes peak, and tracks it slowly to zero. This should further eliminate storage time and result in good efficiency.
I can also get some small, fast bjt's here for cheap, and might try something one day if I get enough xp.
Registered Member #89
Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145
Hi guys
I just got around to try the proposed scheme 2. Half bridge of but11A's driven directly by a Hfe proportional current transformer in series with primary - would that work?
Purely experimental, as I never tried something like that and want to get more into bjt's.
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SSTC: Why it cant use a Bipolar Transistor?
