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I made this ZVS circuit on LTspice and want to make high voltages with it. The ZVS circuit does work fine and output high power but the transformer I made doesn't work fine. I want x400 step up which means the inductance ratio of the inductors has to be 1^2:400^2 which is 1:160000. I made the inductors to have inductances of 1uH (primary L4) and 160 mH (secondary L5) and set a SPICE directive for mutual inductance with full efficiency (K1 L4 L5 1) but on the output I get 58.5 mV @ 58.5 mA, why am I not getting high voltages? I have gone through the circuit multiple times but couldn't find out what's the problem.

This is my circuit enter image description here

And this is the output enter image description here

winny
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  • Welcome! Since output is floating, you need to be measuring differentially (hold and drag) across the output. Otherwise you are measuring against ground. Alternatively, ground the output for simplicity in your simulation. – winny Aug 15 '23 at 08:43
  • I don't understand how my output is floating because both ends of the resistor are connected to the output of my transformer. –  Aug 15 '23 at 08:55
  • They have no connection to ground, hence floating. – winny Aug 15 '23 at 09:00
  • can you be more specific, where should i connect ground to? –  Aug 15 '23 at 09:25
  • Move transout to top of R5. Connect ground to bottom of R5. – winny Aug 15 '23 at 09:33
  • That didn't work –  Aug 15 '23 at 09:35
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    Please be more descriptive. As Andy said, you won't see any high voltage with 1 ohm load on the secondary. Try 1 or 10 Mohm. In SPICE, M is denoted Meg. – winny Aug 15 '23 at 09:42
  • That works, how does more resistance on the load show more voltage? –  Aug 15 '23 at 09:45
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    Limited current capability from the primary, mainly due to the inductors. Please calculate the power needed if you intended to develop 12*400=4800 V into a 1 ohm resistor. P=U^2/R. – winny Aug 15 '23 at 09:57

1 Answers1

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enter image description here

on the output i get 58.5mV @ 58.5mA, why?

You have a 1 Ω load on the output and, that means you get 58.5 mA when the transformer output is 58.5 mV.

Apart from anything else, a 1 Ω output load is ridiculously low for this type of circuit. How much voltage did you expect to achieve with a 1 Ω load?

Andy aka
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  • That was not my question, I was asking why am I not getting a high voltage on the output of the transformer. I'll update my question to make it more clear. –  Aug 15 '23 at 08:48
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    @LOKi that was your question and I've posted a picture of what you originally wrote. – Andy aka Aug 15 '23 at 08:55
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    @LOKi Along with not having a ground reference at the output of the transformer, the reflected load resistance at the primary is 1/400 = 0.0025 ohms. That coupled with the 36uH series inductor and switching at around 8kHz means your system has a gain of 0.55. You also have the driver impedance which will reduce the gain. A little ohm's law goes a long way in understanding many circuits. – qrk Aug 15 '23 at 16:04
  • Hmmm...interesting. The dude dropped off the face of the planet. Does that mean this answer can never get accepted for all eternity? – Ste Kulov Aug 17 '23 at 17:47
  • @SteKulov looks that way LOL – Andy aka Aug 17 '23 at 17:50