Current sense shunt resistor circuit
First Claim
Patent Images
1. A current sense circuit, comprising:
- a shunt resistor in a current path for measuring current in the current path;
a sense resistor coupled to the shunt resistor for dividing current supplied to the shunt resistor; and
a resistance value for the sense resistor being selectable such that a ratio of the shunt resistor value to the sense resistor value produces a gain suitable for establishing a range of current measurements to cover a range of sensed current.
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Abstract
Current through a wire is sensed with a shunt resistor and a sense resistor in a current divider circuit. The values of the shunt resistor and sense resistor are related to provide a specified gain ratio to increase a dynamic range of current measurement. The sense resistor is a trimmable resistor, the configuration of which can be discerned from a look-up table based on a level of precision needed for current measurement. The two resistors can also be related by thermal coefficients to improve linearity of current measurements.
14 Citations
27 Claims
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1. A current sense circuit, comprising:
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a shunt resistor in a current path for measuring current in the current path;
a sense resistor coupled to the shunt resistor for dividing current supplied to the shunt resistor; and
a resistance value for the sense resistor being selectable such that a ratio of the shunt resistor value to the sense resistor value produces a gain suitable for establishing a range of current measurements to cover a range of sensed current. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A current sense circuit, comprising:
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a shunt resistor in a wire for measuring current through the wire;
a sense resistor coupled to the shunt resistor to provide a current divider path for the sensed current;
a switch disposed between the shunt resistor and the sense resistor for decoupling the sense resistor from the shunt resistor;
a voltage buffer coupled to the sense resistor and operable to maintain a single current direction through the sense resistor; and
the bias voltage being further operable to provide a reference current value in conjunction with the sense resistor when the switch is operated to decouple the sense resistor from the shunt resistor. - View Dependent Claims (9, 10, 11)
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12. A current sense circuit, comprising:
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a shunt resistor connected to a wire for measuring current through the wire;
a sense resistor coupled to the shunt resistor to provide a current divider circuit;
a relationship between the shunt resistor and the sense resistor values to provide a specified gain and dynamic range for measuring current through the shunt resistor; and
a trimming mechanism coupled to the sense resistor to modify the value of the sense resistor to obtain the specified gain in relationship with the shunt resistor value. - View Dependent Claims (13)
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14. A method for sensing current in a wire, comprising:
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providing a shunt resistor in the wire to generate a voltage related to current through the wire;
providing a sense resistor coupled to the shunt resistor to obtain a current divider circuit;
measuring current flow through the sense resistor; and
determining current flowing through the shunt resistor based on a specified relationship between the shunt resistor and the sense resistor. - View Dependent Claims (15, 16)
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17. A method for measuring current in a wire, comprising:
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providing a shunt resistor in the wire to develop a voltage for measuring current through the wire;
providing a sense resistor coupled to the shunt resistor to obtain a current divider circuit;
providing a switch between the shunt resistor and the sense resistor to couple or decouple the sense resistor and the shunt resistor; and
obtaining a reference current through the sense resistor when the sense resistor is decoupled from the shunt resistor. - View Dependent Claims (18, 19)
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20. A method for measuring current in a wire, comprising:
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providing a resistance in the wire to develop a voltage when current flows through the wire;
dividing current through the wire between the resistance and a current sensor having a gain relationship with the shunt resistor; and
modifying the current sensor to change the gain relationship to establish a desired gain relationship between the current sensor and the resistance, whereby the current sensor is capable of sensing current through the resistance over an entire dynamic range of operation. - View Dependent Claims (21)
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22. A method for setting a gain relationship between a shunt resistor in a wire for measuring current through the wire and a sense resistor coupled to the shunt resistor to form a current divider circuit, the method comprising:
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passing a predetermined current through the shunt resistor and the sense resistor;
obtaining a current measure for the current flowing through the sense resistor;
determining an error percentage based on an expected value for the current measured in the sense resistor and the actually measured current through the sense resistor; and
adjusting the value of the sense resistor to reduce a difference between the expected value of the current and the actually measured current through the sense resistor. - View Dependent Claims (23, 24, 25, 26)
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27. A method for forming a look-up table of values related to configuration of an adjustable sense resistor for use in conjunction with a current shunt resistor for measuring current in a wire, the method comprising:
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providing values for resistors in resistor path configurations for a resistor network forming the sense resistor;
simulating selected interruptions in the resistor network to produce a percent change in overall resistance for the sense resistor;
storing the selected interruption configuration and the associated percent change; and
providing a list of the interruption configurations and the associated percent changes.
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Specification