UCC256403: LLC resonant converter 1200W / 48V / 30A

Hello,

I am reviewing your inquiry and will get back to you shortly.

Regards,

Hello,

I thought about this a little more.  If you do a constant current constant voltage design you actually could achieve a better power limit.  Please note though when you try to exceed more current than peak current is controlled to the output voltage will drop out of regulation.

Regards,

1) Okay, that works. So this power limit is self-imposed?

The general point of my question is that I want to run this LLC topology for a power rating greater than 1kW. In general, you recommend a Phase Shifted Full Bridge converter for these power levels.

Nevertheless, I find that the LLC converter would be simple to realize, at lower cost, with a smaller converter surface. This remains my humble opinion.  


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2) I have a second question: What is the order of magnitude of the air gap in an LLC-type transformer? I'll explain why: I'm using the dimensioning file you provide for the UCC256403. Following my results, I find myself with these values for my resonant cell:


Cr = 270 nF
Lr = 10 uH
Lm = 80 uH
f0 = 96.9 kHz
Ln = 8
Qe = 0.31

If I use the formula for calculating a transformer in the case of an LLC seen on the internet :

If I choose an ETD49 pot, I end up with an air gap of 4.675mm using this calculation method:

Is it normal to have such a large air gap for this type of topology?

I'm asking you this question because I'm relying heavily on the TIDM325A-2 / TIDA-010081 diagram and I'm wondering what type of pot + air gap is used for this power level.

Thank you for your answers :)

Sincerely,

Let me add this so that you understand my calculation :

Hello,

Your inquiry is under review and I will get back to you shortly.

Regards,

Hello,

In regards to power supply design.  I generally calculate my transformer turns ration, RMS, peak currents.  I give this information along with the voltages and isolation requirements to a magnetic design house to design my magnetics for me.  When designing evaluation modules this is the process we typically use.

When it comes to magnetic design if you want do it your self.  We typically recommend Mag-Inc.  They have a lot of great information and application notes that can help you with your design process.

Regards,

Hello Mike,


Thanks for the information about the transformers. I have just contacted them.


For the UCC256403, is the power limitation imposed by the designer? The maximum power of 1 kW is just an advice because afterwards, you consider that the performance degrades?

Wishing you a good day,


Best regards,

Hello,

Your inquiry is under review and I will get back to you shorty.

Regards,