DC-DC Converter (122V,20A)

Hi Bhushan:

UCC28950 can cover this application. can you capture the waveform during start up when the failure happen?

before you start up, try using diode instead of using SR mosfet.

The waveform should include input mosfet, VGS/VDS/ID and current through primary transformer.

I would also suggest you try UCC28951-Q1, this is pin to pin with UCC28950-Q1 but improve duty and current limit function.

You can find the difference between UCC28950 and UCC28951 in below link.

http://www.ti.com/lit/an/slua853/slua853.pdf

 thanks.

Hi david Huang,

Thanks for your reply. When i Switch the circuit, in fraction of seconds only MOSFET failed.

Using SLUC222D (PSFB) (UCC28950 Excel design Tool), I am not able to get MOSFET, with very low RDS, <5mohm.

I used IRF300P226, but it has 19mOhms RDS.

Here, I am attaching SLUC222D file.

power budget also not in proper with this MOSEFT.120VDC_DC-100Khz-2700w.xls

Hello David

Attached is a debug procedure that you can use to get your design up and  running. It starts by looking at the UCC28950 (or UCC28951) in isolation then applies a low voltage to the power stage so that you can confirm that all the waveforms are correct. The main advantage is that any faults in the system are unlikely to cause damage because you do the initial work at a low power.

Regards
Colin

/cfs-file/__key/communityserver-discussions-components-files/196/UCC28950_2C00_-UCC28951-Debug.docx

Hi Colin and David,

Thanks for your replies. I will come back to you.

Hi Bhushan,

Sorry to be late response . Do you have any progress by following Colin's document?

My meaning is when you step by step power on the UCC28950, does the mosfet still fail?

Hi  David,

Thanks for your reply. This project is going under R& D basis.

My engineers and test bench busy with some other urgent project.

And I would like to change the PCB design also.

Next week i will come back to you with my reply.

Once again thanks for your interest  and earlier also Mr.Colin helped me a lot, regarding some other project.