US Patent 7332358 MOSFET temperature sensing

A MOSFET has its gate voltage controlled to provide a constant drain current of the MOSFET, for example to limit inrush current for charging a capacitance of a power supply arrangement. A decrease in the gate voltage supplied to the MOSFET, corresponding to an increase in the junction temperature of the MOSFET, by more than a determined amount is detected and used to reduce the gate voltage, and hence the drain current, for example to zero, to prevent heating of the MOSFET beyond a maximum operating temperature.