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Post by lamazoid on May 27, 2007 10:48:16 GMT -8
Update: i've increased the number of turns just as you said. Its now 5 turns primary + 2 feedback, wire is single 0.5mm. The efficency rised up to 70% !!!
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Post by Gary Lecomte on May 28, 2007 6:02:14 GMT -8
Update: i've increased the number of turns just as you said. Its now 5 turns primary + 2 feedback, wire is single 0.5mm. The efficency rised up to 70% !!! Glad My Advice Helped.
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rmeyn
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Post by rmeyn on May 28, 2007 19:14:01 GMT -8
Gary & Imazoid, I have been able to simulate transformers quite well, but I have not tried to leave out the seconday. I'll give it a try just the way the diagram indicates. When I googled the IRF7456 it indicated the chip was primarily used as a synchronous rectifer. Richard UPDATE: I simulated the circuit using a general purpose MOSFET and center tapped primaries with inductances you measured. It oscillates nicely, but at very small voltages. The real trick will be to model the IRF7456. I suspect this device is relatively new. I'm having fun and hoping I'm contributing something. Am I right? The real goal here is to take a low DC voltage and induce a high voltage without using much power? Also, you can purchase similar devices (IRF 7240 or IRF 7413 N type MOSFET from www.futurlec.com/TransMos.shtml for 80c or so plus $4.00 US to just about anywhere. Richard
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Post by Gary Lecomte on May 29, 2007 5:17:52 GMT -8
Gary & Imazoid, I have been able to simulate transformers quite well, but I have not tried to leave out the seconday. I'll give it a try just the way the diagram indicates. When I googled the IRF7456 it indicated the chip was primarily used as a synchronous rectifer. Also, you can purchase similar devices (IRF 7240 or IRF 7413 N type MOSFET from www.futurlec.com/TransMos.shtml for 80c or so plus $4.00 US to just about anywhere. Richard 1) If you want, Just add a Secondary. Any Secondary. It will not affect How the circuit does or doesn't Oscillate and it will give you an Output Test point. 2) Not "As a synchronous rectifer". But "In synchronous rectifer Applications". There is a Big Difference here in the meaning. 3) If I were to get the Part, I would prefer the Exact part (IRF7456) that Imazoid used. Not just a Simular one.
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rmeyn
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Post by rmeyn on May 29, 2007 7:14:56 GMT -8
Gary, For testing purposes I thought close might be OK. When I get time I will check my sources more thoroughly. Right now, I am having health problems and probably will be spending more time in bed. Richard
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Post by lamazoid on May 30, 2007 6:39:13 GMT -8
Actually i have tested IRL2905 and IRL2505 they both give nearly the same result.
Richard can you give your model? I dont have PSpice for now but i believe SuperSpice will work so i can test it.
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rmeyn
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Post by rmeyn on May 30, 2007 11:39:39 GMT -8
Iamazoid, Yes I would be happy I'm at work now , but when I get home I will post it. It's a spice model, but should easily be adapted to Pspice or SuperSpice. UPDATE: Your link is www.irf.com/product-info/models/model_links.html You will have to pick the appropriate model off the list and download the .doc file. Let me know how your conversion to SuperSpice works! Richard
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rmeyn
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Post by rmeyn on May 30, 2007 17:19:02 GMT -8
Iamazoid, Yes I would be happy I'm at work now , but when I get home I will post it. It's a spice model, but should easily be adapted to Pspice or SuperSpice. UPDATE: Your link is www.irf.com/product-info/models/model_links.html You will have to pick the appropriate model off the list and download the .doc file. Let me know how your conversion to SuperSpice works! Richard
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rmeyn
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Post by rmeyn on May 30, 2007 17:34:32 GMT -8
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rmeyn
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My primary interests are electronics, sailing, bowling, and camping
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Post by rmeyn on May 31, 2007 19:23:25 GMT -8
Iamazoid, When you use the Spice Model ,only use the code listed at and below .MODEL MM NMOS LEVEL=1 IS=1e-32. and other code relevant to the drain, gate, and source. Your circuit does not show it using the internal diode that exists in the IRF7456. Some of the code I sent you concerns diode modelling. My approach has been to line up model parameters from a PSpice listing and match them to the Spice Printout. I used a general MOSFET model and added the new parameters. So far ,I can get the circuit to begin oscillating, but not continuing to oscillate. Regards, Richard M.
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Post by lamazoid on May 31, 2007 23:24:46 GMT -8
I was unable to load this into SuperSpice I tried CiruitMaker but it returns an error. Anyway, i can use other type mosfets listed in library, if you tell me how to deal with transformer model.
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Post by Gary Lecomte on Jun 1, 2007 4:38:53 GMT -8
Thats Pretty Expensive to just buy One Part and I also have the additional 10% to 15% exchange rate on our Canadian dollar.
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rmeyn
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Post by rmeyn on Jun 1, 2007 5:15:13 GMT -8
Iamazoid, Unforturnately, you cannot directly load the model from Spice into SuperSpice. I would recommend that that you take a SuperSpice MOSFET model, any MOSFET model, and adjust it to the IRF7456 parameters. Pspice has a component called "breakout" when contains genealized models of different components. You can modify the "breakout" MOSFET to match the IRF7456. I worked on mine last night and found that parameters were relatively easy to match. As for the transformer, in Pspice the simplist way is to take two inductors, connect them in series, provide a ground loop path, and add a K LINEAR element , which links inductors together. A very good tutorial to follow can be had at www.seas.upenn.edu/~jan/spice/spice.overview.html Regards, Richard
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Post by lamazoid on Jun 1, 2007 11:58:07 GMT -8
Got it. Its better i'll find normal PSpice or whole Cadence Orcad.
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rmeyn
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Post by rmeyn on Jun 1, 2007 14:19:16 GMT -8
Remember though. If you switch to another software such as Pspice, you will still have to customize a model for the IRF7456 or some other MOSFET. Such software was designed primarily to simulate integrated circuits. I still recommend heartily that you use the tutorial I provided. It was written for SPICE, but works for PSpice , and certainly will work for SuperSpice. Once you get the knack of simple circuits you will be ready to tackle customized component models. Best of Luck! Richard M.
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