UCC27611: Problem with Gan driver

Simon Ravyts

Part Number: UCC27611

Hello
I am using your GaN driver with EPC2034 and EPC 2047 GaNFETs.
There is an evaluation board (EPC9047) where they use both components and where the switching times are about 2 ns. I measured in my circuit and the switching times are about 20 ns, leading to a lot of switching losses.
I noticed that for the turn-on, no resistor but only a diode was used. Can't this lead to problems with overshoots etc? I am using 2 times a 1 ohm resistor (1 ohm for the turn-on and 1 ohm for the turn-off). The datasheet does not really specify good values for the gate resistors. Besides this, can there be other problems that lead to this slow switching time?
Kind regards
Simon Ravyts

over 7 years ago

0 Simon Ravyts over 7 years ago

Intellectual 510 points

Really nobody?

0 Bing -PSC Lu over 7 years ago in reply to Simon Ravyts

TI__Intellectual 1615 points

Hi, Simon,
The resistor slows the switching down, instead of speed it up. The purpose of the resistor is to provide damping. The diode was put there to drop some voltage and keep the FET gate voltage safe.
For the gate resistor value, you have to play with it and see your best results. Normally, the resistor is adjusted to get the trade off between the loss, EMI, overshoot, etc. There is not a fixed resistor value for different designs.
Bing

0 Simon Ravyts over 7 years ago in reply to Bing -PSC Lu

Intellectual 510 points

Hello Bing

Thanks for your reply. I have a question, as you don't put a resistor at all in your design, can I also just directly connect the gate to the driver? Or would it really be better to place a diode?

Simo

0 Bing -PSC Lu over 7 years ago in reply to Simon Ravyts

TI__Intellectual 1615 points

Hi, Simon,
You should be able to do that. Just do some test and observe your gate. If you see the gate voltage becomes too high and you need that diode to help. Otherwise, you can directly connect the gate to the MOSFET. Once you do this, you lose the capability of adjust the switching speed.
Bing

0 Simon Ravyts over 7 years ago in reply to Bing -PSC Lu

Intellectual 510 points

Hello Bing

I disconnected the resistor between the gate of the EPC GaNFET (http://epc-co.com/epc/Products/eGaNFETsandICs/EPC2047.aspx )

and the driver but the switching times remain very low (10 and 40 ns) versus the 2 and 8 ns which are shown in this application note : http://epc-co.com/epc/Products/DemoBoards/EPC9047.aspx

Do you have any other comments on things that I can try? Or possible causes?

Kind regards
Simon

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UCC27611: Problem with Gan driver