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what we can use instead of boost converter, if the boosters are the poorest option for charging the capacitors? if anybody knows, please help me to figure it out thanks
Registered Member #14
Joined: Thu Feb 02 2006, 01:04PM
Location: Prato/italy
Posts: 383
Full wave rectified royer push/pull converter: compact, powerful and simple to construct. Also can be switched on and off pulling down the mosfet gates (make sure your comparator has some hysteresys)
Registered Member #1262
Joined: Fri Jan 25 2008, 05:22AM
Location: Maryland, USA
Posts: 451
Boost converters are not the worst option for charging caps, I don't believe. However, a small power inverter with a rectified output would seem to be the ideal option.
has a schematic that gives you a rough idea of how an inverter works. Building something similar with rectified output should be perfect for charging caps.
Registered Member #1633
Joined: Tue Aug 12 2008, 04:21AM
Location:
Posts: 45
yes, i fiddled around with inverters for awhile, bt i had trouble getting them to invert. you could always use lots and lots of triple A's, which would mean riddiculusly fast charging times, but would make it very heavy. it would be simpler to construct though
Registered Member #1497
Joined: Thu May 22 2008, 05:24AM
Location: Toronto, Ontario, Canada
Posts: 801
My only thought would be a ballasted voltage multiplier running off of AC mains with a soft start system... but only for really *really* big cap banks imo since you loose some control over charge voltage (without a variac).
Registered Member #1694
Joined: Sat Sept 13 2008, 09:13AM
Location: Australia
Posts: 108
I'm ganna say a fly back circuit is a good option simply because they use them in the flashing lights on the wing tips of most aircraft. If those circuits can survive bouncing around on the end of a wing at -60C with very low air pressure, then they can survive in your coil gun im sure.
Registered Member #72
Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659
The flyback is the way to go, for several reasons
1) charging caps is basically a current-source job, a flyback is naturally high output impedeance
2) It runs at high efficiency (useful for battery operated equipment) at all stages of the charge cycle
3) The output voltage is very flexible, the same supply might be used to charge different caps to a wide range of voltages, with no change to the supply apart from terminal voltage detection
The more astute will have notice that all three reasons are just different aspects of the same physics
4) It's easy to choose the primary turns to run from very low voltage batteries, or higher voltage for lower primary current.
BUT, because it charges with current, and not to a well-defined voltage, you need to monitor the cap charge and switch it off, either manually with a DVM, or automatically with a voltage divider+comparator; the latter adds to complexity, and just don't get distracted during the former.
A Cockcroft Walton multiplier also has a high output impedance, and has the big advantage of charging to a well defined terminal voltage, so it would be a very good choice for a ghetto charger. However, it's inefficient at low voltages, and slow at high voltages.
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What else we can use instead of booster, if boosters are poorest option for charging the cap?
