Patent ID: 7477502

Claim:
A power supply system comprising: a power supply; a load coupled to the power supply via a power supply line to receive a voltage therefrom; a circuit protection device comprising: at least one switch device coupled between the power supply and the load on the power supply line; a first controller coupled to the at least one switch for: A. monitoring current flow through the at least one switch; B. maintaining the at least one switch in an ON state while current flows through the at least one switch in a first direction; and C. causing the at least one switch toggle to an OFF state if current flowing through the at least one switch flows in a second direction; and a second controller coupled to the power supply line between the power supply and the at least one switch and coupled to the first controller for sensing an amount of current flowing between the power supply and the at least one switch and causing the first controller toggle the at least one switch to the OFF state when the current sensed by the second controller exceeds a reference value; wherein the first controller comprises a first input coupled to the power supply line between the at least one switch and the power supply, a second input coupled to the power supply line between the at least one switch and the load, and an output coupled to gate terminals of the at least one switch, wherein, when the output is in a first state, the at least one switch is in the ON state and when the output is in a second state, the at least one switch is in the OFF state; wherein the second controller comprises a current sensing device coupled to the power supply line between the power supply and the at least one switch for sensing the current in the power supply line and outputting a sensed voltage corresponding to the sensed current, a comparing device for comparing the sensed voltage to a reference voltage and outputting a first output when the sensed voltage exceeds the reference voltage and a switch coupled between the comparing device and the gate terminals of the at least one switch, wherein the switch, upon receiving the first output of the comparing device, operates toggle the at least one switch to the OFF state; and wherein the first controller comprises an undervoltage protection device and, upon receiving the first output from the comparing device, the second controller switch operates to enable the undervoltage protection device, thus driving the output of the first controller from the first state to the second state, causing the at least one switch to toggle to the OFF state.