UCC28950: Gate oscillating in 380Vdc

Rock Shao

Part Number: UCC28950
Other Parts Discussed in Thread: UCC28951

My customer used UCC28950 for a 1100W project, in the no-load condition, the gate waveforms were normal in 200Vdc~300Vdc input, but there will be oscillating in 380Vdc input.

The schmatic and layout as below. Where can we modify to reduce this problem? thanks.

over 4 years ago

0 Mike O' over 4 years ago

TI__Guru* 85616 points

Hello,

It sounds like the design is stable at every point except at 380 V.

You might want to have him check his voltage loop compensation.

1. You can use Webench or the excel design tool that can be found at the following link. https://www.ti.com/product/UCC28950?keyMatch=UCC28950&tisearch=search-everything&usecase=GPN#design-development##design-tools-simulation

2. There is also an application note that reviews how to calculate the voltage loop for the UCC28950 and UCC28951 devices that can be find at the following link tha your customer may find useful. https://www.ti.com/lit/pdf/slua560

3. You may want to send him the UCC28950EVM https://www.ti.com/lit/pdf/sluub02 so he can study it an compare it to there design waveforms.

a. Also there is a proven layout in the user's guide that can be used as a reference to compare his waveforms too.

Regards,

0 Rock Shao over 4 years ago in reply to Mike O'

Expert 2995 points

Hi,

It is OK for Vin in 380V, but there has another problem is 12V with load, the full load needs 90A, it is normal in the 30A, but over 35A the CS waveform is unstable.

How can I reduce this problem? thanks.

0 Yunsheng Qu over 4 years ago in reply to Rock Shao

TI__Genius 9790 points

Hi, Rock

It looks the voltage loop is not stable if the load is higher than 35A, the CS signal is jumping from 50% duty to narrow duty. could you let customer capture gain/phase curve of voltage loop?

At the same time, I need more waveforms to clarify the issue,

OUTA/OUTC of pin-out of UCC28950 and CS signal together.

Yunsheng

Power management

Power management forum

UCC28950: Gate oscillating in 380Vdc