Active ripple and noise filter for telecommunication equipment powering
US6489755B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Sep 18, 2000 |
| Grant date | Dec 3, 2002 |
| Priority date | — |
| Expiry date | Nov 10, 2020 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH02M1/15
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
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.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.