I need help to identify this old SMD device
After googling the code 5393 I stumbled across this datasheet. The component appears to be the Toshiba TA75393F, and for me it matches your schematic perfectly.



It seems like you're using the 7.15V reference to detect the presence of the 380VDC, in fact this reference is hooked to the "-" pin of the comparator, and in the case of the comparator B, once the reference disappears, the output goes to low making the PNP transistor conducting.

On the other side, the comparator A with the positive feedback branch makes me think of a comparator with hysteresis. According to this question it could be an overvoltage detection circuit (and in this case the higher external reference would make sense since you want to trigger your comparator only in the case when the 380VDC source has an overvoltage).