Ringing in Gate Drive Transformer

[boylesg]

Schematic:

GDT: N30, 4 x AWG30 twisted tightly to form 3 wires, these were then twisted together to form a trifilar strand.


How would one apply an RC snubber to the above schematic. Increasing the value of R3 and R4 is suggested but if I increase the value too much then it will reduce the current into the FET gates significantly.

Ringing on GDT primary (scale 1uS)


Ringing on GDT secondaries (scale 1uS)

 

[barry]

You only need to worry about gate current during turn-on. If you were to increase the resistor to 100 ohms with an input capacitance of 5200pF you would still only have a turn on time of about 520 nS. If this is too much you could back off, but I think you need more than your 5 ohms.

 

[barry]

Bad calculation. should be 2.6uS.

 

[FvM]

What's your question actually?

The trifilar winding will give low leakage inductance, but on the other hand large inter-winding capacitance, likely to cause problems.

 

[boylesg]

What's your question actually?

The trifilar winding will give low leakage inductance, but on the other hand large inter-winding capacitance, likely to cause problems.

The question is what is the best way to get rid of the voltage spikes on the square wave edges without increasing the turn on time of the FETs.