Patent ID: 9455565
Filing Date: 2016-09-27
CPC Classification: H02H

Claim Text:
1. A protection circuit, comprising: a current supply line having a first end for coupling with a current supply, a second end for coupling with a device load, a current sense resistor, and a transistor pass element for controllably passing current to the device load, wherein the device load has a predetermined impedance and a predetermined capacitance; a controller having an enable input, current sense inputs coupled across the current sense resistor, and a gate drive output coupled to a gate terminal of the transistor pass element, wherein the controller turns on the transistor pass element in response to an enable signal at the enable input and turns off the transistor pass element in response to the current sense inputs indicating that the current supply line is passing current in excess of an overcurrent threshold; a reference load having a reference impedance and a reference capacitance; a current mirror having current sense inputs coupled across the current sense resistor and a transistor pass element for passing current to the reference load, wherein the amount of current passed to the reference load is a fixed proportion of the current to the device load, and wherein the reference impedance is the fixed proportion of the device impedance and the reference capacitance is the fixed proportion of the device capacitance; a comparator having a non-inverting input coupled to voltage on the proportional load, an inverting input coupled to voltage on the device load, and an output; a latch circuit having an input coupled to an output of the comparator and an output coupled to the enable input of the controller, wherein the latch circuit latches the controller off in response to a positive output from the comparator; and a switch circuit having a first input coupled to the supply voltage, a second input coupled to the voltage on the device load, and an output to the current mirror, wherein the switch circuit turns off the current mirror in response to the voltage on the device load exceeding a predetermined fraction of the supply voltage.