Patent ID: 7642677

Claim:
Apparatus for controlling inrush current from a power supply to a load, the apparatus comprising: a first and a second power supply input and a first and a second load output; a semiconductor device coupled between the first power supply input and the first load output; a control circuit having a control circuit input coupled to the first load output and a control circuit output coupled to a conductance control node of the semiconductor device, wherein the apparatus is configured such that when a load is connected across the first load output and the second load output, the control circuit provides a control signal to the conductance control node to thereby progressively vary the conductance of the semiconductor device from a low conductance state to a high conductance state in response to a load signal being provided to the control circuit input indicating that a load current flowing through the semiconductor device has exceeded a pre-determined threshold, wherein the load signal is indicative of a voltage at the first load output and the control circuit is arranged to provide the control signal in response to determining whether the voltage at the first load output is less than a threshold voltage, and wherein the control circuit comprises an op amp having a voltage output coupled to a control resistor and a control capacitor which is also coupled to the conductance control node of the semiconductor device, the op amp having inputs coupled to the control circuit input and the threshold voltage.