OVERCURRENT DETECTION CIRCUIT, HOST USING THE SAME, AND METHOD OF DETECTING OVERCURRENT
First 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.
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Accused Products
Abstract
An overcurrent detection circuit installed in a host for supplying power to a device is disclosed. The overcurrent detection circuit includes: 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. The control unit is switchable among (i) a first state where the threshold voltage is set to a first value that is in accord 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.
23 Citations
5 Claims
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1. An overcurrent detection circuit installed in a host for supplying power to a device, the circuit comprising:
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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. - View Dependent Claims (2, 3)
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4. A host compliant with a USB-PD specification, the host comprising:
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a detection resistor and a switch disposed on a power supply line in series to each other; a USB-PD controller that controls the switch and negotiates a bus voltage and a supply current to be supplied via the power supply line, with a device compliant with the USB-PD specification via the power supply line; a converter that has an output terminal connected to the power supply line and generates the bus voltage; and a converter controller that controls the converter so that a voltage level determined by the negotiation is output, wherein the converter controller comprises 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 wherein the USB-PD controller comprises a timer and is switchable among (i) a first state where the threshold voltage is set to a first value that 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 by a predetermined percentage, and (iii) a third state where the threshold voltage is set to a third value that is less than the first value by a predetermined percentage, wherein the USB-PD controller 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, turn off the switch, 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, turn off the switch, and (ii) if the overcurrent detection signal remains negated for a predetermined second time period, transition to the first state.
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5. A method of detecting an overcurrent performed in a host compliant with a USB specification, the method comprising:
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setting an overcurrent threshold value to a first value that is a reference value; comparing a supply current flowing through a power supply line with the first value; setting the overcurrent threshold value to a second value that is larger than the reference value by a predetermined percentage while initiating clocking by a first timer if the supply current exceeds the threshold value; (i) determining an overcurrent state if the supply current exceeds the threshold value before a time counted by the first timer reaches a predetermined first time, and (ii) setting the overcurrent threshold value to a third value that is less than the reference value by a predetermined percentage while initiating clocking by a second timer if the supply current remains less than the threshold value for the first time; and (i) determining an overcurrent state if the supply current exceeds the threshold value before a time counted by the second timer reaches a predetermined second time, and (ii) setting the overcurrent threshold value to the first value, if the supply current remains less than the threshold value for the second time.
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Specification