Hello,

I have designed a board with an isolated H-Bridge with IGBT for a maximum load of 10A at 330V.

The gate driver that I used is 1ED3431MU12M from Infineon and the IGBT IKW20N65ET7. The pwm signal used in this board works at 20KHz

The problem that I am facing is that when there is a load (inductive) all the power supply lines have a huge noise, and some digital circuits don’t work properly.

I looked at the gate signals waveform, but they are not bad and the voltage on the load has not huge ringing (around 24V).

I tried also to add some snubber or just a capacitor across the IGBT without any improvements.

If I look the current on the load I can see a lot of spikes (in the region of the miller plateau), I can reduce them adding a series inductance to the load but on the load side voltage ringing is created.

I suppose that these spikes propagate to all the power supplies from the flyback converter that creates all the power supplies needed from the board. The board uses the power line and the SMPS creates all the power supplies needed, also the isolated voltages for the HIGH side IGBTs.

Is there anyone that have any suggestions or had a similar problem in the past?

Thank you,

Riccardo

P.s I put some pictures that I took with the oscilloscope and the schematic of the H-Bridge.

 

3,300W is a lot of power to be switching on and off at 20KHZ!
You will need to take very exceptional steps to prevent radiated and supply born interference from affecting the control circuits. These steps should include:
Isolation of switching signals from high voltage supplies.
Shielded, twisted pairs for signal and power lines.
Elimination of any possible ground loops.
Good decoupling of all supplies.
Complete EMI shielding of all control circuits.
This is no trivial task.

 

I don’t see amongst all those fuzzy lines any decoupling for the supply for the high side drive.