IGBT Gate Driver PCB layout to minimize Ground Loops:

[adnan012]

Hi,

I want to discuss the layout issues for high power IGBT / Modfet gate drivers.

https://www.eetimes.com/document.asp?doc_id=1279083&page_number=1

There are two grounds -HV and VEE. What is purpose of these two different connections?

Top node of capacitor c2 is connected to the emitter of the IGBT. Is it necessary to use cpacitor?

At which point , 18 VDC ground should be connected?

 

[DaniU]

a) regarding the two grounds: the HV- isn't necessarily a ground, but is the negative voltage in the differential couple: HV+ and HV-.so these two points could be at any given potential in relation to GND/Vee or earth. the Vee voltage is simply the ground of the driving circuit, in the given topology the driver is floating in relation to the IGBT's emitter so the Vee can have a negative voltage for a stronger discharge of the gate (via C2).
b) top node of C2: it is not necessary to use capacitors. you can use the bjt driver without C1 and C2. it might degrade your common mode immunity.
c) 18V ground: the way i understand the circuit, the 18V ground is the Vee.

hope it helps

 

[FvM]

I think there are some unclear points in the circuit description.

"+18V/VEE" is a dual supply which should be specified as voltages relative to HV-, e.g. +12/-6V. More important the supply must not be allowed to float relative to HV-, it must be fixed by some means. Either the voltages are supplied by a dual DC/DC converter, or the offset to HV- is fixed by zener diodes or resistors.

The dual gate driver supply should surely have bypass capacitors. Limits for circuit inductance are commanded by the intended switching speed