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Royer Converter

:: EPE Chat Zone ­:: ­Radio Bygones Message Board :: » EPE Forum Archives 2007-2009 » Archive through 02 March, 2007 » Royer Converter « Previous Next »

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poriet
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Username: poriet

Post Number: 135
Registered: 06-2005

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Posted on Thursday, 01 March, 2007 - 10:52 am:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Hi everyone,
I'm intending to do some stuff which involves getting 200-400V out of a 12V battery. No doubt there are lots of terribly clever ways of doing this, but I'm not an electrical engineer and I cant design SMPSs. So it's a Royer converter or nothing.
I've just finished making one from a design in an old R.M.Marston book on circuits for cars.The original circuit was a self-oscillating astable MV. What I want to do now, instead, is to use a square-wave oscillator and two N-Ch enhancement MOSFETs. I may even try to make the circuit with the Texas TL494 which has a dead-time feature.
As the transformer is a mains-type ( in reverse ). I suppose I should operate around 50Hz although I've seen circuits for these devices which used frquencies of 1KHz!
I guess the first question, then, is this:
Is there any advantage in using frequencies higher than 50Hz on an iron-cored transformer.
What sort of frequency would be an upper limit?
Regards
P.
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winston
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Username: winston

Post Number: 10
Registered: 02-2007

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Posted on Thursday, 01 March, 2007 - 11:06 am:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Assuming you're not wanting a huge current and are wanting DC, don't dismiss an SMPS so easily - there are some that are easy to construct! If you don't need much current, you can construct one with a 555 and a power MOSFET and suitable inductor. I managed to accidentally make well over 1000 volts that way before I looked up how to regulate it properly (I was shooting for 170 VDC, and was manually regulating it via a potentiometer to change the duty cycle of the 555. I turned it a bit too far. There was a lovely smell of ozone and melting capacitor). It worked on plug-in type breadboard, so it isn't even particularly layout fussy.

The regulation was the hardest bit (only a couple of components, but understanding how it regulates), and I ended up using the circuit on the Yahoo! group NEONIXIE-L (the third 555-based one, if you take a look there. The second schematic, using the 555's reset pin makes an ungodly amount of noise - electrical noise as well as the inductor making audible noise.). The regulation part of the circuit changes the duty cycle on the 555 via pin 5, which is what I had been doing with the pot when manually regulating it.
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gordon
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Username: gordon

Post Number: 195
Registered: 05-2005

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Posted on Thursday, 01 March, 2007 - 10:20 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

There are a lot of circuits available, for producing high voltages from 12 volts.

I came across this circuit which might be useful.

http://www.siliconchip.com.au/cms/A_102473/article.html

The switching frequency just needs to be reduced for a conventional iron cored transformer. Not sure what the highest frequency for an iron cored transfomer would be, maybe a few hundred hertz.

Probably depends to some extent on the power being drawn, but it shouldn't be too hard to measure efficiency against switching frequency.
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obiwan
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Username: obiwan

Post Number: 1536
Registered: 12-2005

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Posted on Friday, 02 March, 2007 - 12:11 am:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

The higher the frequency you can go, the better. Without knowing the specs on the transformer, I can't say how high you can go.

But yes, there are advantages. Just because the transformer is a "mains type", doesn't mean that you can only use it at 50/60 Hz.

If nothing else, do some testing. Start out at the lower frequency, and then keep going higher and higher until your voltage/current no longer supplies what you need. Then back it off a little bit.

You may want to keep an eye on spikes too.

But I agree, there are plenty of circuits out there, just search the web. But do what you feel best.
Do Not Hit The Fly That Lands On The Tigers Head.

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