Digital subscriber line alternating current EMI/RFI broadband noise eliminator

• US 6,661,634 B2
• Filed: 01/08/2002
• Issued: 12/09/2003
• Est. Priority Date: 01/08/2002
• Status: Active Grant

• Current Assignee: Qwest Communications International Incorporated (Lumen Technologies, Inc.)
• Original Assignee: Qwest Communications International Incorporated (Lumen Technologies, Inc.)
• Inventors: Phillips, Bruce A., Roberts, John A. Jr., Schneider, Carlton Francis Scott
• Primary Examiner(s): Toatley, Jr., Gregory J.
• Assistant Examiner(s): Benenson, Boris
• Application Number:
  US10/042,672
• Publication Number:
  US 20030127913A1
• Time in Patent Office: 700 Days
• Field of Search: 361/118-119, 361/56, 361/91, 361/111
• US Class Current: 361/119
• CPC Class Codes: G06F 1/266 Arrangements to supply power to external peripherals either directly from the computer or under computer control, e.g. supply of power through the communication port, computer controlled power-strips
• CPC Class Codes: G06F 1/28 Supervision thereof, e.g. detecting power-supply failure by out of limits supervision
• CPC Class Codes: G06F 2200/261 PC controlled powerstrip
• CPC Class Codes: H02H 9/005 avoiding undesired transient conditions
• CPC Class Codes: H02M 1/44 Circuits or arrangements for compensating for electromagnetic interference in converters or inverters
• CPC Class Codes: H04B 3/28 Reducing interference caused by currents induced in cable sheathing or armouring
• CPC Class Codes: Y02D 10/00 Energy efficient computing, e.g. low power processors, power management or thermal management

Abstract

The present invention provides an apparatus and method for filtering electrical power to and from an electrical appliance to reduce or eliminate electromagnetic interference (EMI) and radio frequency interference (RFI). In one embodiment, an electrical outlet strip apparatus is provided for interconnection between an AC power source and an electrical appliance that provides transient voltage surge suppression for the appliance while substantially reducing or eliminating EMI from the AC power source from reaching the appliance. Additionally, the apparatus reduces or eliminates EMI produced by the appliance from propagating into the AC power system. The apparatus and method utilize a multistage EMI filter to filter the electrical power. In particular, the electrical power is filtered in a broadband range associated with digital subscriber line (DSL) systems to provide for improved DSL system performance.

Claims

1. An outlet strip apparatus for filtering electromagnetic interference (EMI) from an appliance prior to said EMI being conducted into an AC power source, said apparatus comprising:

a first input line, a second input line and a ground line for interconnection with said AC power source;

a plurality of outlets for interconnecting said apparatus to at least one said electrical appliance, each said outlet having at least a first, second and third conductor connected to said first input line, second input line and ground line, respectively;

at least one voltage surge absorption element disposed between said AC power source and said outlets, said element directly attached between at least two of said first input line said second input line and said ground line;

a first set of EMI filters interconnected in series with said first input line including first and second capacitors interconnecting said first input line to said second input line and at least one inductor disposed between said capacitors; and

a second set of EMI filters interconnected in series with said second input line and parallel with said first set of EMI filters, said second set of filters including at least one inductor disposed between said capacitors.

2. The apparatus of claim 1, wherein said multi-stage EMI filter is isolated in a metallic container and said metallic container is interconnected to said ground line.

3. The apparatus of claim 1, wherein said multi-stage EMI filter is operative to suppress common mode and differential mode electromagnetic interference.

4. The apparatus of claim 1, wherein said multi-stage EMI filter is operative to suppress electromagnetic interference in a frequency range between 25 kHz and 20,000 kHz.

5. The apparatus of claim 1, wherein said multi-stage EMI filter attenuates the amplitude of electromagnetic interference in a range between 3 dB and 65 dB.

6. The apparatus of claim 1, wherein said multi-stage EMI filter suppresses EMI in a frequency range of 500 kHz to 20,000 kHz and attenuates the amplitude of said EMI in a range between 55 and 65 dB.

7. The apparatus of claim 1, wherein said filter is operative to attenuate both impulse EMI and continuous EMI generated by said appliance.

8. The apparatus of claim 1, wherein said first input line is connectable to an AC power line and said second input line is connectable to an AC neutral line such that said apparatus is compatible with a 120 Volt AC power supply.

9. The apparatus of claim 1, wherein said first and second input lines are connectable to a first and second AC power lines such that said apparatus is compatible with a 220 Volt AC power supply.

10. The apparatus of claim 1, wherein said at least one voltage surge absorption element comprises a varistor, said varistor being normally non-conductive but becoming conducting when the voltage across said varistor exceeds a predetermined level.

11. The apparatus of claim 10, wherein said varistor is a metal oxide varistor.

12. A method for filtering electromagnetic interference (EMI) from an electrical appliance to prevent said EMI from being conducted into an AC power system while providing transient voltage surge suppression for said electrical appliance, said method comprising the steps of:

interconnecting between an AC power source and an electrical appliance a multi-stage EMI filter enclosed within a metallic casing and comprising first and second EMI filters interconnected in series, and a transient voltage surge suppression element;

diverting transient voltages from incoming electricity from said AC power source having a voltage amplitude greater than a predetermined level such that said transient voltages by-pass said electrical appliance;

passing incoming electricity from said AC power source through said first and second EMI filters on a first input line to attenuate EMI contained within said incoming electricity prior to said electricity reaching said electrical appliance, wherein said first and second filters include first and second capacitors interconnecting said first input line to a second input line and at least one inductor disposed between said capacitors; and

passing returning electricity from said electrical appliance through said first and second EMI filters on said second input line including at least one inductor disposed between said first and second capacitors such that EMI generated by said appliance is attenuated prior to re-introduction into said AC power source.

13. The method of claim 12, wherein said second passing step attenuates EMI in a frequency range between 25 kHz and 20,000 kHz.

14. The method of claim 12, wherein said second passing step attenuates the amplitude of said EMI in a range of between 3 dB and 65.

15. The method of claim 12, wherein said EMI filter and transient voltage surge suppression element are contained in an outlet strip apparatus, said outlet strip apparatus interconnecting said electrical appliance to said AC power source.

16. The apparatus of claim 12, wherein said second passing step attenuates EMI noise in a frequency range between 500 kHz and 20,000 kHz while attenuating the amplitude of said EMI noise in a range between 55 and 65 dB.