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TIDA-010015: TIDA-010015

Pravin Khisti

Prodigy 100 points

Part Number: TIDA-010015
Other Parts Discussed in Thread: UCC256301

Hi,

We are using TIDA-010015 design for 500W power supply design.

We are in board bring up stage. We have bypass the PFC stage and working on LLC stage.

But MOSFETs Q3,Q2 gets damaged (Short between all pins) and also UCC256301 gets damaged.

We have verified voltage levels at all pins of llc controller like VCR, BLK which are within limits as per datasheet.

Also all waveforms Isens, Ho,Lo,VCR are as expected.

But we are unable to find out why this is happening. We tried on two different PCB boards but MOSFET and LLC controller

always gets damaged.

We also tried with UCC256402A (with respective changes) but same result we observed.

Can you please help us to resolve the issue.

Regards

Pravin Khisti

Pravin Khisti

over 2 years ago

0 Desheng, Guo over 2 years ago

TI__Expert 6090 points

Hi Pravin,

Thanks for choosing TI!

I can't position what's wrong in your circuits with your description. But, I guess the damage issue is possible introduced by the SR controller's false action.

Suggest you do the following debug:

First, you need check your transformer's inductance are correct on both primary and secondary side; And, you need double check the transformer's 'dot' terminal of those windings, if it is reversed on one, the output maybe shortage.

Then, confirm there is no shortage happen on your power stage;

At last, you can cutoff the SR controller output, or disable it before the LLC started normally.

0 Pravin Khisti over 2 years ago in reply to Desheng, Guo

Prodigy 100 points

Hi Desheng,

Thanks. I will try and revert.

Regards

Pravin

0 Pravin Khisti over 2 years ago in reply to Pravin Khisti

Prodigy 100 points

Hi Desheng,

Your doubt was correct. Winding polarity were reversed.

Now MOSFET is not getting damaged.

But small overlap between LO (green) and HO (Yellow) is observed.

Due to this there is glitch in Bulk voltage and due to this RVCC is getting ON and OFF.

How can I correct this.

Also switching frequency is 485 kHz. Is it in acceptable range?

0 Desheng, Guo over 2 years ago in reply to Pravin Khisti

TI__Expert 6090 points

Good to see you solved this problem.

And thanks again for choosing TI!

0 Pravin Khisti over 2 years ago in reply to Desheng, Guo

Prodigy 100 points

Hi Desheng,

My problem is not resolved. Now HO and LO are overlapping. Please suggest

-Pravin

0 Pravin Khisti over 2 years ago in reply to Pravin Khisti

Prodigy 100 points

Hi Desheng,

Un fortunately MOSFET got damaged after some time again.

Regards

Pravin Khisti

0 Desheng, Guo over 2 years ago in reply to Pravin Khisti

TI__Expert 6090 points

Hi Pravin,

Then, please check the control of SR.

0 Pravin Khisti over 2 years ago in reply to Desheng, Guo

Prodigy 100 points

Hi Desheng,,

Now MOSFET is not getting damaged. We by mistake used different MOSFET than recommended.

But HO and LO waver forms are not as expected.

Green in HO and Yellow is LO

HO is almost 390V and its not getting discharge.

You mentioned earlier SR output. Do you mean Synchronous rectifier ? Its wave form is as below

We tuned Cr, VCR, Isense resistor/capacitor. But waveforms are not as expected.

Please suggest what we should try.

Regards

Pravin Khisti

0 Desheng, Guo over 2 years ago in reply to Pravin Khisti

TI__Expert 6090 points

Hi Pravin,

It looks you solve the problem already.

0 Desheng, Guo over 2 years ago in reply to Desheng, Guo

TI__Expert 6090 points

Oh, I see you have some problem with 'HO', 'LO'.

But, I haven't quite understand your meaning of 'HO'. I guess you want to mention the high side pwm signal, but it should be 15V square waveform.

I suggest you post your problem to UCC25640x product, our product expert will help you on that chip.

0 Pravin Khisti over 2 years ago in reply to Desheng, Guo

Prodigy 100 points

If I have solved the problem Why I would post

0 Desheng, Guo over 2 years ago in reply to Pravin Khisti

TI__Expert 6090 points

Oh, I see you have some problem with 'HO', 'LO'.

But, I haven't quite understand your meaning of 'HO'. I guess you want to mention the high side pwm signal, but it should be 15V square waveform.

I suggest you post your problem to UCC25640x product, our product expert will help you on that chip.