Patent ID: 7760479
Filing Date: 2010-07-20
Classification: H02H,H03K

Abstract:
1. A circuit that limits current and protects against short circuits, the circuit comprising: a pass transistor defining a first input, a first output and a first control, wherein the input is connected to an input voltage, the first output delivers an output current to a load; a second transistor defining a second input, a second output and a second control, wherein the first and second inputs and outputs are connected together, and wherein the second transistor is smaller than the pass transistor; a programmable reference that sets the current limit; a comparator with one input connected to the first and second outputs, a second input connected to the programmable reference, and the comparator having a compare output that drives the second control; a logic gate comprising an input connected to the compare output, wherein the logic gate output drives the first control, and wherein when the first and second outputs are at a lower voltage than the programmable reference, the compare output turns on the second transistor and turns off the pass transistor, and wherein, when the first and second outputs rise above the programmable reference, the compare output turns off the second transistor and turns on the pass transistor.