Changing switching circuit from BJT to IGBT

Thread Starter

THICKO

Joined Jun 10, 2016
17
Hi Gentlemen
I have a working coil driver circuit using a BU940 darlington.
As the circuit is rather current heavy i have changed it to an IGBT as this is
the way things have gone over the years. I am using a driver TG4420 and
an IRGB14C40L device. I wonder if anyone could help as to the gate resistor
value, i'm a bit concerned that the value of 1k shown in the data sheet is
rather large for a 5v gate drive. My dim and distant past recalls small values
for gate circuits around 10-20 ohms in switching circuits, am i just out of
date or maybe just stupid?
I can post a circuit if ness but in essence it's just a micro going to the TG4420
The gate supply is 5v and the IGBT device is a 5v gate type.
The gate charge is around 30nc i believe.

Mick
 

crutschow

Joined Mar 14, 2008
27,212
A small series gate resistor is often used to prevent oscillations in MOSFET circuits.
IGBTs are much slower and likely won't oscillate with no resistor, but you can us 20-100Ω if that makes you feel better.
 

Thread Starter

THICKO

Joined Jun 10, 2016
17
Many thanks Crutschow i just wondered about the 1k gate resistor used and listed in
the data sheet. I thought the switching speed would be very slow with that fitted.
I had put a 22 ohm in the circuit which is obviously much smaller than the 1k and
was concerned about the gate ringing/oscillating.
 
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