Active EMI filter having no inductive current sensing device
First Claim
Patent Images
1. A filter for an electrical power system, comprising:
- an error amplifier coupled to system lines in said system, to obtain voltages related to currents in the respective lines, and operable to output a signal based on a difference in current between a pair of said lines;
the output signal being coupled to one of said lines;
wherein the output signal influences said difference in said voltages between said pair of system lines to decrease the voltage difference.
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Abstract
An active EMI filter senses current in a ground line as a voltage across a capacitor coupled to the ground line. The EMI filter senses common mode voltage and determines a difference between the common mode voltage and noise to provide an output to the ground line to reduce the difference.
6 Citations
34 Claims
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1. A filter for an electrical power system, comprising:
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an error amplifier coupled to system lines in said system, to obtain voltages related to currents in the respective lines, and operable to output a signal based on a difference in current between a pair of said lines;
the output signal being coupled to one of said lines;
wherein the output signal influences said difference in said voltages between said pair of system lines to decrease the voltage difference. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A method for reducing EMI in an electrical power circuit with an active EMI filter, comprising:
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sensing a voltage on at least one of an input and ground line related to current through the line;
sensing voltage in at least another of the input and ground line;
comparing the sensed voltages and providing a voltage signal based on differences between the voltages; and
applying the voltage signal to at least one of the input and ground lines to thereby reduce the voltage difference. - View Dependent Claims (16, 18, 19, 20, 21, 22, 23, 24, 25)
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17. An active EMI filter, comprising:
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an error amplifier for amplifying an error signal;
a capacitor coupled to an input of the error amplifier for developing a voltage related to a sensed current;
a second capacitor coupled to a second input of the error amplifier for developing a voltage related to a sensed current; and
an output capacitor coupled to an output of the error amplifier and at least one of the first and second capacitors;
wherein the error amplifier is operable to detect a difference in voltages developed across the first and second capacitors and supply a voltage to the output capacitor to compensate the difference in voltages between the first and second capacitors. - View Dependent Claims (26, 27, 28, 29, 30, 31, 32, 33, 34)
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Specification