ISOLATED CURRENT TO VOLTAGE, VOLTAGE TO VOLTAGE CONVERTER
First Claim
1. A current sensor comprising:
- a transformer having a primary winding, a secondary winding, and a substantially annular magnetic transformer core through which passes the primary winding and the secondary winding, wherein;
the primary winding is adapted to carry a current to be measured; and
the secondary winding is adapted to selectively carry a saturating current for inducing a saturating field in the magnetic transformer core, and to selectively carry a sampling current for inducing a field opposing the saturating field in the magnetic transformer core;
a power source for selectively supplying current to the secondary winding;
a sensing circuit adapted to measure a voltage that is substantially proportional to the magnitude of the current to be measured; and
a control circuit adapted to selectively apply the saturating current to the secondary winding and to selectively apply the sampling current to the secondary winding.
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Accused Products
Abstract
A current sensor is provided that employs a primary winding that carries the current to be measured, and a secondary winding that controls the flux inside the magnetic core, provides a sample of the primary current, and also helps to control the flux at small primary currents and to saturate the transformer. An auxiliary winding is optionally used to control the flux in order to simplify control of the sensor. By periodically applying a certain voltage at the secondary winding, the transformer core is forced out of saturation, and a sample of the primary current is taken by a sensing circuit that may include a sample-and-hold circuit and an analog-to-digital converter. A control circuit is employed to control the currents flowing in the secondary winding and optional auxiliary winding and to manage the sensing circuit.
120 Citations
36 Claims
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1. A current sensor comprising:
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a transformer having a primary winding, a secondary winding, and a substantially annular magnetic transformer core through which passes the primary winding and the secondary winding, wherein; the primary winding is adapted to carry a current to be measured; and the secondary winding is adapted to selectively carry a saturating current for inducing a saturating field in the magnetic transformer core, and to selectively carry a sampling current for inducing a field opposing the saturating field in the magnetic transformer core; a power source for selectively supplying current to the secondary winding; a sensing circuit adapted to measure a voltage that is substantially proportional to the magnitude of the current to be measured; and a control circuit adapted to selectively apply the saturating current to the secondary winding and to selectively apply the sampling current to the secondary winding. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. A current sensor comprising:
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a transformer having a primary winding, an auxiliary winding, a secondary winding, and a substantially annular magnetic transformer core through which passes the primary winding, the auxiliary winding, and the secondary winding, wherein; the primary winding is adapted to carry a current to be measured; the auxiliary winding is adapted to carry a saturating current for selectively inducing a saturating field in the magnetic transformer core; and the secondary winding is adapted to carry a sampling current for selectively inducing a field in the magnetic transformer core opposing the saturating field induced by the saturating current; a power source for selectively supplying current to the auxiliary winding and to the secondary winding; a saturating switch operatively coupled to the auxiliary winding for selectively connecting the auxiliary winding to the power source; a sampling switch operatively coupled to the secondary winding for selectively connecting the secondary winding to the power source; a sense resistor operatively connected in series with the secondary winding; a sensing circuit adapted to measure a voltage developed across the sense resistor wherein the sensing circuit comprises a sample-and-hold circuit and an analog-to-digital converter; and a digital control circuit adapted to selectively open and close the saturating switch and the sampling switch and to send control signals to the sample-and-hold circuit and to the analog-to-digital converter. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24, 25)
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26. A current sensor comprising:
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a first transformer having a first primary winding, a first secondary winding, and a first substantially annular magnetic transformer core through which passes the first primary winding and the first secondary winding, wherein; the first primary winding is adapted to carry a current to be measured; and the first secondary winding is adapted to selectively carry a first saturating current for inducing a first saturating field in the first magnetic transformer core, and to selectively carry a first sampling current for inducing a field opposing the first saturating field in the first magnetic transformer core; a second transformer having a second primary winding, a second secondary winding, and a second substantially annular magnetic transformer core through which passes the second primary winding and the second secondary winding, wherein; the second primary winding is adapted to carry the current to be measured; and the second secondary winding is adapted to selectively carry a second saturating current for inducing a second saturating field in the second magnetic transformer core, and to selectively carry a second sampling current for inducing a field opposing the second saturating field in the second magnetic transformer core; a first sensing circuit adapted to measure a voltage that is substantially proportional to the magnitude of the current flowing in the first primary winding; and a second sensing circuit adapted to measure a voltage that is substantially proportional to the magnitude of the current flowing in the second primary winding; and a control circuit adapted to switch an output-selection switch and to selectively apply the first sampling current to the first secondary winding and the second sampling current to the second secondary winding, such that; at least one of the first sampling current and the second sampling current is always flowing; and the output-selection switch selects the first sensing circuit when the first sampling current is flowing and selects the second sensing circuit when the second sampling current is flowing. - View Dependent Claims (27, 28, 29)
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30. In a system comprising a signal to be measured and a current sensor comprising a power source and substantially annular magnetic transformer core through which passes a primary winding and a secondary winding, a method of measuring the signal comprises:
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routing the signal to be measured through the primary winding; pulsing a saturating current through the secondary winding; pulsing a sampling current through the secondary winding; and measuring the sampling current through the secondary winding to determine the magnitude of the signal to be measured. - View Dependent Claims (31, 32, 33, 34, 35, 36)
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Specification