Pure sine wave inverter driver latch up

[e.roble]

Hi everyone. I have attached a picture file to consult something. Do you have an idea why the driver intermittently lose output even if there are no shutdown scenario?

I noticed it at first at 300W load. It was gone when I tried adding turn off resistance on IGBT gates. But it showed again at 400W load. It does not show on load below 400W and above 400W. only at 400W. Before it only shows at 300W.

It only happens also on the falling edge side of the sine wave output.

From my research, outputs may latch when high side reference "VS" goes way below "COM" but i did not detect any of this during the shutdown scenari

 

[alec_t]

The image is too small for clarity, but seems to show a problem with the driver input. So it's not surprising there is a loss of output.