Temperature-compensated apparatus for monitoring current having controlled sensitivity to supply voltage
First Claim
1. In a circuit for connection to a resistance shunt, an apparatus for monitoring current through the shunt, comprising:
- a comparator having two output states in relation to a threshold switching voltage, and having inputs for connection to the resistance shunt wherein the comparator is responsive to a voltage developed across the shunt, so that a voltage across the shunt larger than the threshold switching voltage causes the comparator output to assume a first one of the two output states and a voltage across the shunt smaller than the threshold switching voltage causes the comparator output to assume the second one of the two output states; and
a temperature compensation means, connected to the comparator, for temperature compensating the threshold switching voltage such that the threshold switching voltage changes proportionally to absolute temperature.
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Abstract
An apparatus for monitoring current through a lamp circuit that uses a series resistance shunt in the circuit with one end connected to a current source and the second end connected to the lamp. The apparatus includes a comparator that is connected across the shunt and has a threshold switching voltage wherein a voltage across the shunt that is larger than the threshold switching voltage will switch the comparator on and a voltage across the shunt that is smaller than the threshold switching voltage will switch the comparator off. A biasing circuit, connected to and controlling the comparator, temperature compensates the threshold switching voltage such that the threshold switching voltage changes proportionally to absolute temperature and controls a sensitivity of the threshold switching voltage to changes in a supply voltage of the circuit. In a preferred embodiment, the shunt is a portion of the printed board trace. Also in a preferred embodiment, the apparatus has a 50% sensitivity to changes in supply voltage.
31 Citations
20 Claims
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1. In a circuit for connection to a resistance shunt, an apparatus for monitoring current through the shunt, comprising:
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a comparator having two output states in relation to a threshold switching voltage, and having inputs for connection to the resistance shunt wherein the comparator is responsive to a voltage developed across the shunt, so that a voltage across the shunt larger than the threshold switching voltage causes the comparator output to assume a first one of the two output states and a voltage across the shunt smaller than the threshold switching voltage causes the comparator output to assume the second one of the two output states; and a temperature compensation means, connected to the comparator, for temperature compensating the threshold switching voltage such that the threshold switching voltage changes proportionally to absolute temperature. - View Dependent Claims (2, 3, 4, 5)
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6. In a circuit for connection to a resistance shunt, an apparatus for monitoring current through the shunt, the improvement comprising:
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a comparator having two output states in relation to a threshold switching voltage, and having inputs for connection to the resistance shunt wherein the comparator is responsive to a voltage developed across the shunt, so that a voltage across the shunt larger than the threshold switching voltage causes the comparator output to assume a first one of the two output states and a voltage across the shunt smaller than the threshold switching voltage causes the comparator output to assume the second one of the two output states; and a sensitivity control means, connected to the comparator, for controlling a sensitivity of the threshold switching voltage to changes in a supply voltage of the circuit. - View Dependent Claims (7, 8, 9, 10)
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11. In a circuit for connection to a resistance shunt, an apparatus for monitoring current through the shunt, comprising:
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a comparator having two output states in relation to a threshold switching voltage, and having inputs for connection to the resistance shunt wherein the comparator is responsive to a voltage developed across the shunt, so that a voltage across the shunt larger than the threshold switching voltage causes the comparator output to assume a first one of the two output states and a voltage across the shunt smaller than the threshold switching voltage causes the comparator output to assume the second one of the two output states; and a biasing circuit, connected to and controlling the comparator, for temperature compensating the threshold switching voltage such that the threshold switching voltage changes proportionally to absolute temperature, and for controlling a sensitivity of the threshold switching voltage to changes in a supply voltage of the circuit. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
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Specification