Method and apparatus for sensing a current in a circuit
First Claim
1. A current sense circuit, comprising:
- a current sense resistor coupled to an input of the current sense circuit, the current sense resistor to receive a current to be sensed from the input of the current sense circuit to convert the current to be sensed to the current sense voltage;
a first PN junction diode of a first transistor coupled to the current sense resistor;
a second resistor coupled between a collector of the first transistor and a base of the first transistor; and
a light emitting diode (LED) coupled to the first PN junction diode to provide a current sense threshold substantially a function of a difference between a forward voltage drop of the LED and a forward voltage drop of the first PN junction diode, the current sense threshold substantially equal to a voltage drop across the second resistor, the first PN junction diode coupled to be biased from the forward voltage drop of the LED, the LED coupled to the current sense resistor to generate an output when the current sense voltage from the current sense resistor reaches the current sense threshold.
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Abstract
Techniques are disclosed to sense a current in a circuit. For instance, current sense circuit according to the teachings of the present invention includes a current sense resistor coupled to an input of the current sense circuit. The current sense resistor is coupled to receive a current to be sensed from the input of the current sense circuit. The current to be sensed is converted to a current sense voltage. A first PN junction diode is coupled to the current sense resistor. A light emitting diode (LED) is coupled to the first PN junction diode to provide a current sense threshold substantially proportional to a difference between a forward voltage drop of the LED and a forward voltage drop of the first PN junction diode. The first PN junction diode is coupled to be biased from the forward voltage drop of the LED. The LED is coupled to the current sense resistor to generate an output when the current sense voltage from the current sense resistor reaches the current sense threshold.
9 Citations
14 Claims
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1. A current sense circuit, comprising:
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a current sense resistor coupled to an input of the current sense circuit, the current sense resistor to receive a current to be sensed from the input of the current sense circuit to convert the current to be sensed to the current sense voltage; a first PN junction diode of a first transistor coupled to the current sense resistor; a second resistor coupled between a collector of the first transistor and a base of the first transistor; and a light emitting diode (LED) coupled to the first PN junction diode to provide a current sense threshold substantially a function of a difference between a forward voltage drop of the LED and a forward voltage drop of the first PN junction diode, the current sense threshold substantially equal to a voltage drop across the second resistor, the first PN junction diode coupled to be biased from the forward voltage drop of the LED, the LED coupled to the current sense resistor to generate an output when the current sense voltage from the current sense resistor reaches the current sense threshold. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A current sense circuit, comprising:
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a current sense resistor coupled to a direct current (DC) output of a power supply, wherein the current sense circuit is to be powered entirely from the DC output, wherein the current sense resistor is to convert a current at the DC output into a current sense voltage; a first PN junction diode of a first transistor coupled to the current sense resistor; and a second resistor coupled between a collector of the first transistor and a base of the first transistor, wherein a current sense threshold is substantially equal to a voltage across the second resistor, wherein the current sense circuit is to generate an output when the current sense voltage reaches the current sense threshold to sense the current at the DC output. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14)
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Specification