Electronic – MOSFET won’t turn-off at low drain current

Using Andy's and some other people's suggestion here is the solution that I've come up with

The pro of this approach is the simplicity, but the cons are that the driving speed is limited and the power consumed when the PMOS is ON.

Edit: More clarification: OutConn- can be any source voltage (Vcc). PGate2 is the connection to the PMOS gate to switch it. After actually testing this circuit, i can say that for a power MOSFET with gate capacitance of about 3000pF the switching frequency that can be achieved can be maximum of about 1kHz. If anyone knows how to achieve higher frequency, please let me know.

There is a small change in total gate charge with the FET's supply voltage. It is not particularly large, because the difference in Gate-Drain capacitance when going from 24 V to 40 V is relatively small. However, the gate drive current is generated in your IC from a linear regulator from the 40 V input. Therefore with a constant gate drive, the IC will still dissipate more power at higher VIN.

There is an NXP Three Phase Driver IC -- MC34937 which allows the gate drive power to be distinct from the FET bridge supply -- you can use that to either 'move' some of the dissipation outside the IC, or supply it from a DC/DC converter which reduces the power dissipated considerably.