Current sensor and method using differentially generated feedback
First Claim
1. A current sensor having at least one signal interface channel comprising:
- a transformer having a primary winding, a secondary winding and a feedback winding;
a magnetic core to magnetically couple said primary winding, said secondary winding and said feedback winding; and
a feedback generating circuit responsive to an AC signal in said secondary winding for supplying a feedback signal to said feedback winding, said feedback signal being free of any polarity reversal and effective for maintaining a flux in said magnetic core substantially near zero;
said feedback generating circuit comprising;
an operational amplifier having a first differential input port, a second differential input port at which a DC offset voltage may develop, and first and second differential output pores; and
a switching assembly coupling said feedback winding to said first and second differential output ports and adapted to generate a compensating AC signal from said DC offset voltage, said compensating AC signal being coupled to the first and second differential input ports of said operational amplifier through said primary and secondary windings.
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Accused Products
Abstract
A current sensor has one signal interface channel including a transformer having a primary winding, a secondary winding and a feedback winding. A magnetic core magnetically couples the primary winding, the secondary winding and the feedback winding. The current sensor further includes a feedback generating circuit responsive to an AC signal in the secondary winding for generating a feedback signal having a continuous polarity supplied to the feedback winding. The feedback signal being effective for maintaining a flux in the magnetic core substantially near zero. The feedback generating circuit is made up of an operational amplifier, such as an amplifier having first and second differential input ports and first and second differential output ports, and a switching assembly designed to generate a compensating AC signal from a DC offset voltage. The compensating AC signal is conveniently coupled to the operational amplifier through the magnetic core.
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Citations
18 Claims
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1. A current sensor having at least one signal interface channel comprising:
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a transformer having a primary winding, a secondary winding and a feedback winding; a magnetic core to magnetically couple said primary winding, said secondary winding and said feedback winding; and a feedback generating circuit responsive to an AC signal in said secondary winding for supplying a feedback signal to said feedback winding, said feedback signal being free of any polarity reversal and effective for maintaining a flux in said magnetic core substantially near zero; said feedback generating circuit comprising; an operational amplifier having a first differential input port, a second differential input port at which a DC offset voltage may develop, and first and second differential output pores; and a switching assembly coupling said feedback winding to said first and second differential output ports and adapted to generate a compensating AC signal from said DC offset voltage, said compensating AC signal being coupled to the first and second differential input ports of said operational amplifier through said primary and secondary windings. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. In a current sensor having one signal interface channel including a respective transformer having a primary winding, a secondary winding and a feedback winding each being magnetically coupled to each other through a common magnetic core, a feedback generating circuit responsive to an AC signal in said secondary winding for supplying a feedback signal to said feedback winding, said feedback signal being free of any polarity reversal and effective for maintaining a flux in said magnetic core substantially near zero, said feedback generating circuit comprising:
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an operational amplifier having a first differential input port, a second differential input port at which a DC offset voltage may develop, and first and second differential output ports; and a switching assembly adapted to generate a compensating AC signal from said DC offset voltage, said compensating AC signal being coupled to said operational amplifier through said primary and secondary windings; said switching assembly comprising; first and second input switches for respectively coupling during a first switching period the first input port to said secondary winding and the second input port to a predetermined electrical ground, and for respectively coupling during a second switching period the second input port to said secondary winding and the first input port to the predetermined electrical ground; and an output switch for coupling during the first switching period the first output port to said feedback winding, said output switch coupling during the second switching period the second output port to said feedback winding. - View Dependent Claims (10, 11, 12, 13, 14)
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15. A method for signal compensation in a current sensor comprising:
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magnetically coupling a primary winding, a secondary winding and a feedback winding; generating a feedback signal free of any polarity reversal, said feedback signal being supplied to said feedback winding and being effective for maintaining a magnetic flux substantially near zero by operating an operational amplifier having a first differential input port, a second differential input port at which a DC offset voltage may develop, and first and second differential output ports from which said feedback signal is produced; and generating a compensating AC signal from said DC offset voltage, said compensating signal being predeterminedly coupled to the first and second differential input ports of said operational amplifier through said primary and secondary windings. - View Dependent Claims (16, 17)
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18. In a current sensor having one signal interface channel including a respective transformer having a primary winding, a secondary winding and a feedback winding each being magnetically coupled to each other through a common magnetic core, a feedback generating circuit responsive to an AC signal in said secondary winding for supplying a feedback signal to said feedback winding, said feedback signal being free of any polarity reversal and effective for maintaining a flux in said magnetic core substantially near zero, said feedback generating circuit comprising:
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an operational amplifier having a first differential input port, a second differential input port at which a DC offset voltage may develop, and first and second differential output ports; and a switching assembly adapted to generate a compensating AC signal from said DC offset voltage, said compensating AC signal being coupled to said operational amplifier through said primary and secondary windings; said switching assembly comprising; first and second input switches for respectively coupling during a first switching period the first input port to said secondary winding and the second input port to a predetermined electrical ground, and for respectively coupling during a second switching period the second input port to said secondary winding and the first input port to the predetermined electrical ground; and an output switch for coupling during the first switching period the first output to said feedback winding, said output switch coupling during the second switching period the second output port to said feedback winding.
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Specification