Hi, i am using opto as an isloation between a three phase gate driver circuit and controller(signal generator), but i met a problem that is when i connect for example INH3 and INL3(also the ouputs from opto) the same time from opto board to the driver board, and when i give INL (low side mosfet switching) signal, the Vgs of low side mosfet shows nothing, but once i unplugged the INH3 connection bwteen driver and opto, the there will be vgs waveform, the INH3 has no signal input. I am confuesed. Anyone could help? Thank you

 

Disconnect the optocoupler and manually apply known high/low signals to the gate driver inputs to check the gate driver behaves as expected.

 

Disconnect the optocoupler and manually apply known high/low signals to the gate driver inputs to check the gate driver behaves as expected.

Thank you for replying, yeah i directly give INH or INL, the waveform is right, mosfets are switching, the peoblem should not be driver circuit, i tried to use a seprate Vcc power supply, and also tried seprate INH and INL on differen pcb board, but the issue still there, i think becuase they shared the same ground, however they have to share the same ground of driver, so i just get stuck