Silly Miniature "OLTC"
flannelhead, Tue Mar 04 2008, 03:59PMA pair days ago I got this silly idea of an OLTC. Here's the block diagram:
Actually it isn't OLTC because it's not run "Off-Line", but the topology is otherwise the same. You may think the idea is silly, so do I
I have built the 555 circuit already. I don't currently have time to throw the whole thing together. I don't except very good results from this circuit, but c'mon, it won't cost anything to try, and I have all the parts already. MOSFETs have never before been tested with OLTCs, there's a change it could even work with low powers. Next weekend I should have enough time to put it together. It could become DWOLTC, heh Let's see how it gets going!
Re: Silly Miniature "OLTC"
Experimentonomen, Tue Mar 04 2008, 04:24PM
It should work with a small coil, IRF460 can take quite some surge current.
Experimentonomen, Tue Mar 04 2008, 04:24PM
It should work with a small coil, IRF460 can take quite some surge current.
Re: Silly Miniature "OLTC"
flannelhead, Tue Mar 04 2008, 04:39PM
Yeh, my coil is gonna be quite small (1.75in x 5in, 380 turns).
flannelhead, Tue Mar 04 2008, 04:39PM
Yeh, my coil is gonna be quite small (1.75in x 5in, 380 turns).
Re: Silly Miniature "OLTC"
Sulaiman, Tue Mar 04 2008, 10:03PM
Most of the disposable camera flash circuits that I've seen have +HV as 'ground' with -ve high voltage
so that circuit wouldn't work as drawn.
Sulaiman, Tue Mar 04 2008, 10:03PM
Most of the disposable camera flash circuits that I've seen have +HV as 'ground' with -ve high voltage
so that circuit wouldn't work as drawn.
Re: Silly Miniature "OLTC"
flannelhead, Wed Mar 05 2008, 01:26PM
My circuit seems to have positive HV output. And it can be changed by reversing the diode on HV out (it's halfwave rectified)
flannelhead, Wed Mar 05 2008, 01:26PM
My circuit seems to have positive HV output. And it can be changed by reversing the diode on HV out (it's halfwave rectified)
Re: Silly Miniature "OLTC"
Marko, Wed Mar 05 2008, 01:34PM
Guys, OLTC is pretty obsolete technology now, I don't think it's worth wasting your time.
25nF cap at that voltage is going to yield only 1.3milijoules at that voltage, absolutely no chance for any arcs.
To make any success out of OLTC, you will need to wind extremely low resonant frequency secondary, and use capacitors i uF range with a single turn primary. You'll need resonant frequency no higher than 100..200kHz.
What's the resonant frequency of your secondary spark?
In other words, don't build OLTC.
If you just want sparks from camera inverter, you are much better to simply discharge a few uF cap into a flyback.
If you want a TC, you'll be far, far better to simply build a small DRSSTC, and actually easier even if it doesn't look so.
I'd really recommend you a small DRSSTC since it will be very good learning project, and very rewarding once you get it right!
Despite someone might tell you to increase size of your coil to lower the resonant frequency, don't do that - keeping the coil small really cuts the price of parts down, and small IGBT's can run up to a Mhz.
Marko, Wed Mar 05 2008, 01:34PM
Guys, OLTC is pretty obsolete technology now, I don't think it's worth wasting your time.
25nF cap at that voltage is going to yield only 1.3milijoules at that voltage, absolutely no chance for any arcs.
To make any success out of OLTC, you will need to wind extremely low resonant frequency secondary, and use capacitors i uF range with a single turn primary. You'll need resonant frequency no higher than 100..200kHz.
What's the resonant frequency of your secondary spark?
In other words, don't build OLTC.
If you just want sparks from camera inverter, you are much better to simply discharge a few uF cap into a flyback.
If you want a TC, you'll be far, far better to simply build a small DRSSTC, and actually easier even if it doesn't look so.
I'd really recommend you a small DRSSTC since it will be very good learning project, and very rewarding once you get it right!
Despite someone might tell you to increase size of your coil to lower the resonant frequency, don't do that - keeping the coil small really cuts the price of parts down, and small IGBT's can run up to a Mhz.
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