UCC25600: Load regulation.

Sreeni N K

Part Number: UCC25600

Hi,

We are using UCC25600 for our project which is based of LLC. The system is designed to deliver an output power of 600W.

We are facing some issue in the load regulation of the system; the voltage is not stable; the output voltage keeps dipping during the load range.

The System rating is as below:

Vin: 320 -690 VAC

Vout1: 15V

Iout1: 20A

Vout2: 15V

Iout2 :15A

So, could you please help on this.

The schematic of the same is attached below.

LLC.pdf

Looking forward to your reply.

Regards,

Sreeni N K

4 months ago

0 Sreeni N K 4 months ago

Prodigy 60 points

The input of the LLC is 800V DC.

The O/P is dropping to 13.5V @output current 7A.

The TBD values are as follows:

R49 :5.1k Ohms

R55: 2.7K Ohms

R52: 160 Ohms

D25 & D27: B1100-13-F

0 Sean Xu 4 months ago in reply to Sreeni N K

TI__Genius 13590 points

Hello,

Do you have waveforms of bridge? Maybe over current is kicked in. Maybe the loop is not stable.

Please check the bridge current signals and loop stability.

Regards,
Sean

0 Sreeni N K 4 months ago in reply to Sean Xu

Prodigy 60 points

Hi,

Thank you for your quick response.

We will share the waveforms, by that time could you please check on the compensation circuit, over current and RT pin circuit values.

Also, the resonant tank values.

Regards

Sreeni N K

0 Manikanta Pallantla 4 months ago in reply to Sreeni N K

TI__Genius 12945 points

Hi Sreeni,

Could you share the design calculator. It would be easier to verify the tank parameters through it. Also, have you tried to simulate the converter with your compensation values?

Regards

Manikanta P

0 Sreeni N K 4 months ago in reply to Manikanta Pallantla

Prodigy 60 points

Hi Manikanta,

We tried to use design calculator, but there was some issue with design calculator the values were not changing w.r.t our inputs given into the calculator.

So, we have manually calculated the values, I am attaching the same here. We have calculated the values keeping the Magnetizing Inductance fixed.

And we couldn't simulate the converter with the compensation value, due to the software limitations.

UCC25600_Battery Charger_600uH.pdf

Regards

Sreeni N K

0 Manikanta Pallantla 4 months ago in reply to Sreeni N K

TI__Genius 12945 points

Hi Sreeni,

Could you please clarify why the output voltage is considered as 30V whereas actual output voltage is 15V in your resonant tank design? Also, you are currently using type 2 compensator. For Direct frequency control, you will have to use type 3.

Regards

Manikanta P

0 Sreeni N K 4 months ago in reply to Manikanta Pallantla

Prodigy 60 points

Hi Manikanta,

There are 2 possible options for the output, either 2outs in parallel 15V@15A, 15V@20A each, or in series which is 30V@20A.
I will try to tune it with type 3 and will get back to you.

Regards

Sreeni N K

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UCC25600: Load regulation.