Patent ID: 9748761
Date: 2017-08-29
CPC Classifications: H02H

Claim:
1. An overcurrent detection circuit installed in a host for supplying power to a device, the circuit comprising: a detection resistor disposed on a power supply line; a current monitoring unit that compares a detected voltage that is a voltage drop across the detection resistor with a variable threshold voltage and asserts an overcurrent detection signal if the detected voltage exceeds the threshold voltage; and a control unit including a timer, wherein the control unit is switchable among (i) a first state where the threshold voltage is set to a first value is in accordance with a reference value for overcurrent protection, (ii) a second state where the threshold voltage is set to a second value that is greater than the first value, and (iii) a third state where the threshold voltage is set to a third value that is less than the first value, wherein the control unit is configured to: (a) in the first state, if the overcurrent detection signal is asserted, transition to the second state while initiating clocking by the timer; (b) in the second state, (i) if the overcurrent detection signal is asserted, transition to an overcurrent detection state, and (ii) if the overcurrent detection signal remains negated for a predetermined first time period, transition to the third state while initiating clocking by the timer; and (c) in the third state, (i) if the overcurrent detection signal is asserted, transition to the overcurrent detection state, and (ii) if the overcurrent detection signal remains negated for a predetermined second time period, transition to the first state.