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Heating in LLC HB mosfets ?
Heating in LLC HB mosfets ?
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Old 24th April 2019, 05:37 AM   #51
voltwide is offline voltwide  Ireland
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Your test indicates that magnetizing current was way too high, so the MOSFETs heated up according to conduction loss Rdson*Irmsē.
You should learn to measure primary current and simulate the primary tank with LTspice.
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Old 24th April 2019, 06:17 AM   #52
TroelsM is offline TroelsM  Denmark
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I see the point about the lead-inductance. I'm pretty sure it s a 400V part. Still bordeline, but it was only for a test.
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Old 24th April 2019, 07:58 AM   #53
TroelsM is offline TroelsM  Denmark
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Quote:
Originally Posted by voltwide View Post
Your test indicates that magnetizing current was way too high, so the MOSFETs heated up according to conduction loss Rdson*Irmsē.
You should learn to measure primary current and simulate the primary tank with LTspice.
Hi. I think I have a decent knowledge of simulating this stuff, but I'm probably overlooking something, or maybe I have a "hidden" parasitic in the prototype that does not show up in the sims i have done.

The supprising part is that the sims dont show drastic changes from 75uH to 110uH. I donīt think I'll have the time to full analyze the difference right now, but hopefully I can get back to the issue later.

Kind regards TroelsM
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Old 24th April 2019, 10:24 AM   #54
kees52 is offline kees52  Netherlands
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I have use this core a E71\33\32.

But is for a welder inverter.

Have someone a good simulation schematic for LLC with models? I have the ncp1395 mod and osc only it is in zip with schematic.
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Old Yesterday, 09:20 PM   #55
voltwide is offline voltwide  Ireland
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Quote:
Originally Posted by kees52 View Post
I have use this core a E71\33\32.

But is for a welder inverter.

Have someone a good simulation schematic for LLC with models? I have the ncp1395 mod and osc only it is in zip with schematic.

pls complete your zip archive, I got "could not find symbol VC02"
you may find this link useful: https://archive.eetasia.com/www.eeta...N_6f1e90c8.HTM
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Old Today, 09:38 AM   #56
kees52 is offline kees52  Netherlands
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Quote:
Originally Posted by voltwide View Post
pls complete your zip archive, I got "could not find symbol VC02"
you may find this link useful: https://archive.eetasia.com/www.eeta...N_6f1e90c8.HTM
zip is complete, it does work here.

unpack it in your ltspice folder under LLC design or such, find application.lib and change path for models if needed.

Thanks for the link, these I had already.

Have you idea of a usable feedback for a constant voltage source inverter for mig welding? Using a comparator into this feedback can speedup the regulation, maybe a good idea for use with a amplifier, however I think a unregulated smps for audio do work as good or maybe better as a feedbacked one, but the impedance is higher, for low impedance what is good for impuls behavior feedback is better.

regards

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Old Today, 12:46 PM   #57
voltwide is offline voltwide  Ireland
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Quote:
Originally Posted by kees52 View Post
zip is complete, it does work here.

unpack it in your ltspice folder under LLC design or such, find application.lib and change path for models if needed.

Thanks for the link, these I had already.

Have you idea of a usable feedback for a constant voltage source inverter for mig welding? Using a comparator into this feedback can speedup the regulation, maybe a good idea for use with a amplifier, however I think a unregulated smps for audio do work as good or maybe better as a feedbacked one, but the impedance is higher, for low impedance what is good for impuls behavior feedback is better.

regards
My LLCs operate unregulated, i.e. at fixed frequency adjusted to primary series resonant frequency. With this operating point the output impedance is at absolute minimum, I would call it better than toroidal xformer of same power rating.
On the other hand this implies the urgent need of some fast current limiting. Otherwise the hole thing blows at the first output short.
I prefer clamp Diodes that limit voltage excursion at the primary tank - a bullet-proof cycle-by-cycle current limiter.
For welding applications I would recommend secondary synchronous rectification. That saves power loss and delivers stiffer voltage than diode rectifiers.



The constant voltage regulation of LLC is a special beast due to the nonlinear transfer function - so I avoided this approach.
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Old Today, 12:49 PM   #58
TroelsM is offline TroelsM  Denmark
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I think it would be very interesting to discuss LLC-simulation, but maybe it should not be in this thread?

I have an older thread with a simple, general LLC simulation:
LLC simulation
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Old Today, 03:38 PM   #59
kees52 is offline kees52  Netherlands
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Quote:
Originally Posted by voltwide View Post
My LLCs operate unregulated, i.e. at fixed frequency adjusted to primary series resonant frequency. With this operating point the output impedance is at absolute minimum, I would call it better than toroidal xformer of same power rating.
On the other hand this implies the urgent need of some fast current limiting. Otherwise the hole thing blows at the first output short.
I prefer clamp Diodes that limit voltage excursion at the primary tank - a bullet-proof cycle-by-cycle current limiter.
For welding applications I would recommend secondary synchronous rectification. That saves power loss and delivers stiffer voltage than diode rectifiers.



The constant voltage regulation of LLC is a special beast due to the nonlinear transfer function - so I avoided this approach.
Thanks

For the mig welding I need a constant voltage and need then feedback, I can do that with a PID feedback or such, caluclating that is not so difficult.

Synchronous rectification is a nice approach but the mosfets need to be uge, and I do not now it is suitable for welding, I do not see it somewhere used in a welder inverter.

I have some resonace designs who are used as a mma welder, also open loop and these have a current limiter who works fine, a antistick, maybe usable for a high current amplifier supply. wil send if you like, it is from russia..


rgards
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