Tool/software:
Hi TI team
Need your expert team support on following:
Our gate drive requirement is 20A
We selected TI UCC21750QDWRQ1 ( 10A) and using Current buffer/amplifier IXD_630 (30A) to achieve gate drive requirement.
Question is : How to achieve soft turn-off with this combination ( TI GD + IXD_630 ---> SiC Power Module)?
Thanks
Hi Chandra,
What is the FET or IGBT part number for which you say you need 20A-30A of gate drive current? The largest IGBT module with which I am familiar is FF800R12KE7 .
I tested this module with several gate drivers and measured the gate current with a 1 ohm external Rg and a differential probe (Igate). These "10A" gate drivers never even reached 4A of output current into this real load, since they had a finite dI/dt rise time, and before the output reached the saturation limit, the gate voltage increased enough to where the (Vdd-Vgs)/Rgate set a lower current limit than the saturation value. While I do agree that the buffer will provide a lower 0.3 ohm resistance vs. the 2.5 ohms of the UCC21750, the peak current will not necessarily be 3x higher.
This IXD_630 is a CMOS buffer, and it will buffer the soft-turn off into a strong turn-off. There are some circuits you can use if you use a BJT totem pole buffer instead, since that is a linear totem pole buffer.
My recommendation is therefore to try and check the performance with the UCC21750 alone first. If you do build a circuit with this buffer, you should add a bypass path with a DNP 0 ohm resistor, so that you can easily compare the performance of buffer vs. no buffer. Hopefully you will find that the integrated output stage is sufficient, and then you can retain the soft-turn off function of this device.
Best regards,
Sean
Thank you very much dear Sean, for quick support and useful insights on our approach
Following are more details:
Power module part number : CAB6R0A23GM4T, SiC MOSFET Power Module from Wolf speed, 2300V, 200A, 6mohm
Drive current requirement (I source/sink @Rg =0) is 14.6A
So, we are searching for 15A gate drivers with built-in safety features and without SPI Communication as per project requirement
This led to go with TI UCC21750QDWRQ1 (10A) + Current buffer/amplifier IXD_630 (30A) to achieve gate drive requirement.
Assumption is that though TI gate driver hav soft turn-off feature, going with above 2-stage approve results in loss of soft turn-off.
How the loss of soft turn off will impact?
What are the possible mitigation techniques from your expertise?
Appreciate your support
Chandra
