Inrush limiting circuit

Quite a neat little circuit, using the return path makes the gate drive circuitry simpler. Because the SMPS output is isolated from the input it makes no difference to the supply which rail of the DC supply the inrush current limiter is installed.

The mosfet is not being used as a switch it is being used in linear mode to maintain constant dv/dt across the mosfet which results in constant current charging of the input capacitors.