Hi, i think you have to cheak your mosfet again may be their is a short among one of them,and the Vgs of High side is always greater than the low side Vgs, therefore their is something wrong with your circute cheak it carefully.
i am designing the single phase half bridge inverter circuit.I used the optocoupler HCPL 3120 to drive the mosfet. My question is, can only just one HCPL 3120 is used to drive two mosfet that are high side mosfet and low side mosfet?
It is possible to design bootstrap-based MOSFET drivers using opto-couplers. So, it is possible to use a driver circuit comprising of opto-couplers but no dedicated driver such as the IR2110. However, I recommend the use of such dedicated drivers instead of opto-coupler based designs.