Inverter theory

This forum is for specialized infomation important to the construction and safe operation of the high voltage electrical supplies and related circuitry needed for fusor operation.
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Martin Shahi
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Joined: Thu Aug 29, 2013 1:06 pm
Real name: Martin Shahi

Inverter theory

Post by Martin Shahi » Sun Oct 27, 2013 11:02 am

Hi everybody.
So at the moment I am trying to make sense of power inverter theory, and would be very grateful for some clarification, or a link to somewhere where I can study the theory, since my google searches have been fruitless.

I want to build my own power supply, and my thought process behind this is to take (UK) mains, rectify it, invert it back to AC at a minimum of 10kHz, and then use ferrite transformers to get a higher voltage, and then if needed to use a CW multiplier. However the problem I am having is working out how to increase the frequency. I have found a circuit (http://en.wikipedia.org/wiki/File:Fluor ... verter.png) which increases the frequency, but I do not know by how much, or how to work it out. I tried building this circuit in Yenka, but that didn't quite work out, though I did observe a large increase in frequency.

Thanks for any replies

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Chris Bradley
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Re: Inverter theory

Post by Chris Bradley » Sun Oct 27, 2013 1:10 pm

There are a number of topologies of circuits to switch a DC source and feed it into a transformer. Some, but not all, have been tried and reported here. Each have advantages and disadvantages. Just do an internet search of various combinations of 'switching / circuit / topologies / switch-mode / SMPS / SCR'.

The rectification of AC to provide a DC supply is, actually, non-trivial because you can easily end up with a high-frequency switched supply but with the lower AC frequency overlaid on it. More difficult is the use of rectification and high frequency high value capacitors (or, rather, avoiding using too many of them) to provide a clean DC input to a switching circuit fit for a stable high frequency output. However, for fusor work this is less significant because you don't really need a pure DC supply. Some overlaid AC voltage variation is not a big deal for a fusor supply.

Current availability of FET drivers with built in PWM spoil the circuit builder by making the whole task pretty simple (relatively speaking). Read more and you'll form a picture of how you want to proceed. I'll happily help you, as I am sure others will, once you have reached some level of demonstrated self-research and you ask well-informed, specific and technical questions which are always welcome here.

Martin Shahi
Posts: 20
Joined: Thu Aug 29, 2013 1:06 pm
Real name: Martin Shahi

Re: Inverter theory

Post by Martin Shahi » Sun Oct 27, 2013 2:30 pm

Chris Bradley wrote: I'll happily help you, as I am sure others will, once you have reached some level of demonstrated self-research and you ask well-informed, specific and technical questions which are always welcome here.
Thanks, I'll search using the terms you mentioned and read up a bit more on it.

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