Active ripple and noise filter for telecommunication equipment powering
First Claim
1. A circuit for effectively reducing an unwanted AC component variation of a DC voltage to be applied to a load comprising:
- a detector coupled to sense the average voltage value of low frequency variation of said DC voltage; and
a controllable attenuator coupled in circuit between a source of said DC voltage and said load, and being operative to controllably attenuate the average voltage value sensed by said detector by an amount that is effective to provide a DC output voltage for application to said load in which said unwanted AC component variation has been effectively removed.
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Accused Products
Abstract
An active tracking filter reduces low frequency noise (such as a 20 Hz ringing signal) riding on a DC voltage (e.g., on the order of (−40 VDC) applied to a load such as a subscriber line interface circuit (SLIC). A controllable impedance device, such as a FET operating in its linear range, is coupled in circuit between a source of the DC voltage and the load. A low frequency voltage average detector circuit senses the average low frequency variation of the DC voltage. An output voltage sensor senses a DC output voltage at the output of the controllable impedance. A differential error amplifier circuit has a first input coupled to the low frequency voltage average detector circuit, a second input coupled to the output voltage sensor, and an output coupled to a control terminal of the controlled impedance device. The error amplifier controls the drive to the controllable impedance device such that the voltage drop thereacross reduces the low frequency variation of the DC voltage by an amount sufficient to accommodate the maximum amplitude of the noise, and thereby provide a DC output voltage to the load in which the unwanted low frequency noise has been effectively removed.
91 Citations
25 Claims
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1. A circuit for effectively reducing an unwanted AC component variation of a DC voltage to be applied to a load comprising:
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a detector coupled to sense the average voltage value of low frequency variation of said DC voltage; and
a controllable attenuator coupled in circuit between a source of said DC voltage and said load, and being operative to controllably attenuate the average voltage value sensed by said detector by an amount that is effective to provide a DC output voltage for application to said load in which said unwanted AC component variation has been effectively removed. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A tracking filter for effectively reducing unwanted low frequency noise riding on a DC voltage to be applied to a load comprising:
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a controllable impedance device adapted to be coupled in circuit between a source of said DC voltage and said load, and being operative to provide a controlled voltage drop thereacross;
a low frequency voltage average detector circuit which is adapted to sense the average low frequency variation of said DC voltage;
an output voltage sensor adapted to sense a DC output voltage at the output of said controllable impedance; and
an error amplifier circuit having a first input coupled to said low frequency voltage average detector circuit, a second input coupled to said output voltage sensor, and an output coupled to said control terminal of said controlled impedance device, and being operative to control the drive input to said controllable impedance device such that the voltage drop thereacross reduces the average low frequency variation of said DC voltage by an amount that is sufficient to accommodate the maximum amplitude of the unwanted low frequency noise, and thereby provide a DC output voltage for application to said load in which said unwanted low frequency noise has been effectively removed. - View Dependent Claims (11, 12, 13, 14, 15, 16)
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17. An apparatus comprising:
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input terminals to which a DC power supply voltage is applied from a DC power source for powering a signaling circuit;
output terminals that power said signaling circuit with a filtered version of said DC power supply voltage; and
a filter arrangement that is operative to effectively remove an unwanted AC component variation of said DC power supply voltage applied to said input terminals and produce said filtered version of said DC power supply voltage that powers said signaling circuit, said filter arrangement including a detector coupled to said input terminals and being operative to sense the average voltage value of low frequency variation of said DC power supply voltage, and a controllable attenuator coupled between said input and output terminals, and being operative to controllably attenuate the average voltage value sensed by said detector by an amount that produces said filtered DC power supply voltage for powering said signaling circuit, and in which said unwanted AC component variation has been effectively removed. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24, 25)
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Specification