I read on this website that it can be switched with 5v. Also really ignorant and rude to quote and exclude half of that message which I specifically refer to avoid asking questions about WHY im doing this as everyone I come to ask advice for about this topic has ended up wasting hours giving me unrelated advice and after I explain every specific detail of my life do they agree what im doing is right but they have no clue how to solve it. Stuff like this is why I dont like forums. Cant ask a simple question without having nosy people think they know my life better than me.
yes ive added a delay period so they can both be off while transitioning. Sorry for not understanding your question and I still dont understand what do you mean what do I think is the voltage on the drain pin. Im still learning electronics and just got into learning all this a week ago. I would assume zero?
Think as your transformer being a see-saw, with the pivot point at 50cm.
How high will the see-saw go.
Leo..
So the transformer is causing a inductive voltage spike? That would make sense but I dont know how high it would go as it depends how far the transformer/seesaw is from the pivot point.
OK, I am glad you added the last bit as up to that point I had no clue what your knowledge of electronics is, I will try to keep that in mind while answering.
I don't know how else to ask the question, one of the MOSFETs is on, one is off, with maybe a gap in between when they switch over. The MOSFETs both have their drain connected to the transformer primary at opposite ends, with the mid-point at about 55V (exact voltage not important). Both sources are connected to 0V. The one that's on is conducting electricity has its drain connected through the inside of the MOSFET to its source, so the drain is at 0V. The one that's off is open circuit internally, with its drain connected only to the other end of the transformer. The transformer mid point is 55V, one end is 0V through the on MOSFET, I'm asking what voltage the other end of the transformer is at, the end connected to the OFF MOSFET. I saw while I was typing that @Wawa posted a big clue, so I'm going to let you think about my question and his clue.
An in case you are wondering what this has to do with your overheated MOSFETs, it is one possible cause of the problem.
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oh ok that makes alot better sense. The seesaw and two transformer winding makes alot better sense. So the second seesaw/transformer winding would double the voltage.
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Well, when one transistor is on and saturated its drain voltage is basically zero, so the supply voltage appears across the half of the transformer primary connected to it. Because the two parts of the primary are tightly coupled the drain of the other "off" transistor is driven to twice the supply voltage. At 56v that would be 112v - so you need MOSFETs rated at at least 112v, preferably significantly higher.
And you absolutely do NOT want flywheel diodes across the windings because then either one of the other half of the primary would be always short-circuited.
You may find that higher voltage MOSFETs can't be driven from even a 5v logic level in which case a device such as an IGBT, insulated gate bipolar transistor, might be a better choice.
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Thread boss. Instant reason to ignore. Good luck.
Too bad for you. I built a MOSFET transformer circuit like yours and made it work.
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Correct. So your MOSFET maximum drain-source voltage has to be higher than twice the supply voltage, I'd go for at least 50% higher, so at least 180V.
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And no, an IRF540 is not suitable as it will hardly be on with a gate voltage of 5V, never mind its maximum drain-source voltage.
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thanks so much this helped a ton. Ill look into this. I have zero experience with IGBT but I assume they are driven similar to mosfets. Im currently looking at the FGPF4633 which has a 1.55v saturation voltage and goes up to 330v. And thanks for the warning about the diode. It sucks that IGBT's are not as easy to get as mosfets and are slightly more expensive. Amazon 2 day shipping has been a blessing the past few weeks. But so far looking at the specs IGBT's are amazing! Sorry being unable to reply yesterday as I just created this account and am limited by my daily posts
Understood, and again thanks so much for going through with having me understand better the seesaw mechanism. That helped a ton and opened my way of thinking. Sorry being unable to reply yesterday as I just created this account and am limited by my daily posts
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IGBTs are in effect a combination of a MOSFET and a bipolar, the mosfet turns on the transistor.
So you should be able to drive them like a MOSFET but you do need to make sure the Vgs-on is compatible with your driver.
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Finally got it to work, as Perry and the others stated it was because of the transformer causing the voltage to double. The IGBT I listed earlier didnt work, so I went with a IRF540 mosfet with a TC4420 driver and it worked flawlessly the first time! Sorry for the delay in response as shipping for all these components took a while. The whole circuit works perfectly.
But thanks so much to everyone who answered the question. I wish I could mark multiple solutions but again am very grateful for the help. And thanks to everyone else who respected my wishes to not go into details of my personal life even with the slight toxicity. This has been the first ever time I actually got a response on a forum post answered instead of wasting hours into my life and being told ridiculous stuff like move to the city or magically spend thousands of dollars that I dont have.
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