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Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
Sulaiman wrote ...
The posts above assume a constant VOLTAGE output, charging capacitors requires constant CURRENT.
Look through the forums for 'CCPS'
I don't think the output V-A characteristics of a SLR inverter is much different than that of a "bare" half-bridge, but of course the ZCS decreases switching losses a lot.
jonny5 wrote ...
For LOPT transformers with integrated voltage multipliers, the capacitive ballasting of the CW voltage multiplier may also serve to protect against shorts.
Sorry for OT but I have never seen a TV transformer with integrated multiplier, and I have seen tens of them...
Registered Member #1451
Joined: Wed Apr 23 2008, 03:48AM
Location: Boulder, Co
Posts: 661
Sulaiman wrote ...
The posts above assume a constant VOLTAGE output, charging capacitors requires constant CURRENT.
Look through the forums for 'CCPS'
Thanks! I really hadn't thought that the supply would be different so I didn't specify at first. I've looked through the forum and a CCPS is EXACTLY what I need. I even thought about building one a while ago but it was a little over my head at the time.
One question: in a bridge design that uses a GDT to drive it, when one device is switched on, the opposite one in the bridge is off.... But looking at the schematic it seems that the one that is off has a negative voltage across it's gate from the GDT, not just 0. Is that bad? It's not really that large of a voltage, only up to 24v, but that can't be good for a MOSFET. Should I put in a reverse bias diode to short the negative potential? And if I did, wouldn't that load the GDT unevenly and effect the other windings?
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
No, it's not bad, in fact the negative voltage helps it turn off quicker and stay off. It works fine and has been used in industry for years, just wire it up and be happy.
However, be aware that 24V is a dangerously high voltage for reliable gate drive, 12 or 15 would be better. It's symmetrical, so if you drive the "on" devices to +12v, the off ones see -12. If you use the usual setup of a 1:1 GDT, two gate drive ICs, one inverting and one non-inverting, and run them off 12v, this is what you'll get.
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Most efficient transformer drive design
