UCC28951-Q1: Sic MOSFETs for PSFB topology VDC: 950V

Hello,

Please see my comments to your questions below.

1. Share me data for doing PSFB using SIC mosfets. Presently For next revision schematic I'm referring TOshiba 5KW reference design (5 kW Isolated Bidirectional DC-DC Converter Reference Design | Toshiba Electronic Devices & Storage Corporation | Asia-English )

I searched the TI reference design data base for the UCC28951 and there are no SiC reference designs.  https://www.ti.com/reference-designs/index.html

However, you should be able to use SiC FETs with this controller; as long as, you use SiC drivers.  The following link will bring you to the driver page where can find half bridge and full bridge drivers for your application.

https://www.ti.com/power-management/gate-drivers/overview.html

2. Additionally, for faster turn oFF of Primary FEts (SIC Mosfets ) , can i shunt SiC diode for faster turn OFF? Will it disturb ZVS or something related? Image shown below

> You should be able to use the same principle as turning off a Si FET.  You set the turn-on delay of the half bridge to turn the FET on at 1/2 the resonant period.  The speed of the turning off the FET should not affect this.

>The SiC FETs do have lower capacitance that allows them to turn off faster than a SiC FET.  This will affect the size of the shim inductor.

3. IF shim inductor is required as per excel and we are not using shim inductor? What are the consequences? is it only hard switching or it will disturb any other waveform?

>If the excel calculated requires a shim inductor and you don't use one.  You will not have the ability to achieve ZVS down to 50 % load.  However, you could still valley switch if you set the turn-on delays to 1/4 the tank frequency.

4. adding Ceramic capacitor across drain to source FETs on primary side as shown below. This is after CT. can we do something like this?

>I do not recommend doing this because these capacitor may act as a high frequency bulk capacitor if the capacitance is too large.

>However, for noise I have seen some designers use small high frequency capacitors here.  If you decide to do this I would evaluated the current the CT is measuring vs the current in the primary of the transformer to make sure it is measuring the current correctly.  

Regards,