Patent ID: 7679876

Claim:
A system limiting a current through a load, comprising: a current sensor coupled to the load, producing a current indication indicating the value of the current through the load; a determination circuit coupled to the current sensor, generating a short-circuit signal when the current value exceeds a predetermined threshold; and a current supply circuit coupled to a voltage supply source, the current sensor, and the determination circuit, comprising a current limiting path and a current pass-through path, wherein the determination circuit determines whether the short-circuit signal is generated; if yes, the current supply circuit delivers a limited current through the current limiting path to the load upon receiving the short-circuit signal, and if not, the current supply circuit passes the current from the voltage supply source through the pass-through path to the load; wherein the current supply circuit comprises: a current source producing a bias current; a first transistor in a diode connection, coupled to the current source; a second transistor coupled to the voltage supply source and the current sensor, connected with the first transistor to form a current mirror and generate a mirrored current, and disconnected from the first transistor to provide the pass-through path; a first switch coupled to the determination circuit, the first and the second transistors, receiving the short circuit signal to connect the first and the second transistors; and a second switch coupled to the determination circuit, a ground and the second transistor, receiving the short-circuit signal to disconnect the second transistor from the ground; and wherein the limited load current is determined by width to length (W/L) ratio of the first and the second transistors, and the bias current.