Thanks for answering!
But since I use optocoupler, I already have one isolated ground "GND_DRV", and my isolated DC/DC use this ground too. How can I provide power to the drvier IC 1EDN7126GXTMA1, if the Vss is not connected to this ground, or I don't need an optocoupler anymore? This question troubles me a whole day. I'm a rookie, really appreaciate any reply, thank you