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eem2am 14th January 2012 08:51 PM

Stabilising SMPS simulation for Amp supply
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Hello, please could you help to stabilise my LLC SMPS simulation.

Its got a split output so it can be for a half-bridge class d amplifier. (330W)

Its in LTspice.

I have made it have a minimum frequency by adding a current source I1 to the LTC6908.

I then implemented variable frequency by adding a PNP transistor to the frequency changing parts of the LTC6908.

It doesn’t seem possible to stabilise it, so I am hoping that you may assist me.

Here is the LTspice simulation in .txt form, and if you make it to .asc form, then it will be runnable in LTspice

2shared - download LLC.txt

Here also is simulation

Attachment 260366

gmarsh 15th January 2012 06:16 PM

Any particular reason you're using a pure oscillator IC instead of a purpose-built LLC controller?

eem2am 15th January 2012 06:18 PM

yes, dont have a model for an LLC controller

dtproff 16th January 2012 04:59 AM

I will be honest ant tell you I have never been able to stabilize the LLC in either symetrix or ocad. From what I understand from talking to the resident PHD here, this issue is in the small signal model for the LLC's is not well described for a spice simulation because of the way Lp/Lr add in over the power range. Not sure I am in total agreement with him but he does have the PHD in his tittle and he heads up the advance R&D group.

If you just want help stabilizing the loop for the LLC using a standard TL431/Opto I can certainly provide you some values that will get you pretty close the first time up.


dtproff 16th January 2012 05:15 AM

Alternatively, if you just need the open loop waveforms yuo could set it to resonance and see what you get.


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