AC power source filter for audio video electrical load

• US 6,473,510 B1
• Filed: 04/03/1998
• Issued: 10/29/2002
• Est. Priority Date: 04/03/1998
• Status: Expired due to Term

• Current Assignee: Monster LLC (Atlantic Acquisition, Inc.)
• Original Assignee: Monster, Inc. (Atlantic Acquisition, Inc.)
• Inventors: Marsh, Richard N.
• Primary Examiner(s): Isen, Forester W.
• Assistant Examiner(s): Grier, Laura A.
• Application Number:
  US09/054,738
• Time in Patent Office: 1,670 Days
• Field of Search: 381/94.5, 381/94.6, 381/77, 333/168-169, 333/181
• US Class Current: 381/94.6
• CPC Class Codes: H03H 1/0007 of radio frequency interference filters
• CPC Class Codes: H04B 15/005 Reducing noise, e.g. humm, from the supply
• CPC Class Codes: H04B 2203/5425 improving S/N by matching impedance, noise reduction, gain control
• CPC Class Codes: H04B 2203/545 Audio/video application, e.g. interphone
• CPC Class Codes: H04B 2203/5491 using filtering and bypassing
• CPC Class Codes: H04B 3/56 Circuits for coupling, blocking, or by-passing of signals

Abstract

A filter for suppressing noise surges and noise frequencies in ac power lines to an audio video load includes at least one noise suppression circuit. The noise suppression circuit in turn includes first and second inductors coupled to respective power lines in series with the load. A capacitor is coupled between the power lines at the input of the first inductor and the output of the second inductor. With this arrangement, the capacitor suppresses noise surges in the power line, while being protected by the second inductor from being damaged by the surges. Also, the filter suppresses two noise frequencies using only the single capacitor. If desired, additional noise suppression circuits can be provided, with each noise suppression circuit suppressing two noise frequencies using only a single capacitor.

Claims

1. A filter for suppressing noise in at least first and second power lines used for electrically connecting an audio video load to an ac power source, comprising:

a first inductor coupled to the first power line in series between the power source and the load for presenting an impedance to noise;

a second inductor coupled to the second power line in series between the power source and the load for presenting an impedance to noise and preventing damage to components connected to its output; and

a capacitor coupled between an input side of the first inductor and protected and output side of the second inductor and protected from power surges by said second inductor for short circuiting high frequency noise.

2. A filter for suppressing noise in at least first and second power lines used for electrically connecting an audio video load to an ac power source, comprising:

a first inductor coupled to the first power line in series between the power source and the load;

a second inductor coupled to the second power line in series between the power source and the load; and

a capacitor coupled between an input side of the first inductor and an output side of the second inductor, wherein the inductors are characterized by respective inductances and the capacitor is characterized by a capacitance, and the inductances and capacitance are established for suppressing at least two predetermined frequencies in the power lines.

3. A filter for suppressing noise in at least first and second power lines used for electrically connecting an audio video load to an ac power source, comprising:

a first inductor coupled to the first power line in series between the power source and the load;

a second inductor coupled to the second power line in series between the power source and the load; and

a capacitor coupled between an input side of the first inductor and an output side of the second inductor, further comprising a metal oxide varistor coupled to the power lines in parallel with the load at an input side of the filter.

4. A filter for suppressing noise in at least first and second power lines used for electrically connecting an audio video load to an ac power source, comprising:

a first inductor coupled to the first power line in series between the power source and the load;

a second inductor coupled to the second power line in series between the power source and the load; and

a capacitor coupled between an input side of the first inductor and an output side of the second inductor, wherein the capacitor is a first capacitor, and the filter further comprises;

a third inductor in series with the first inductor;

a fourth inductor in series with the second inductor; and

a second capacitor coupled between an input side of the third inductor and an output side of the fourth inductor, whereby the filter suppresses at least four predetermined frequencies.

5. A filter for suppressing noise in at least first and second power lines used for electrically connecting an audio video load to an ac power source, comprising:

a first inductor coupled to the first power line in series between the power source and the load;

a second inductor coupled to the second power line in series between the power source and the load; and

a capacitor coupled between an input side of the first inductor and an output side of the second inductor, in combination with the audio video load.

6. A device for suppressing ac power line noise to an audio video load, comprising:

at least first and second power lines configured for electrically connecting an ac power source to the audio video load;

at least first and second inductors respectively coupled to the first and second power lines, each defining a respective input side and a respective output side for presenting an impedance to noise; and

at least one capacitor coupled to a capacitor line, the capacitor line being attached to the input side of the first inductor and to the output side of the second inductor and protected from power surges by said second inductor for short circuiting high frequency noise.

7. The device of claim 6, wherein the inductors are coupled to the power lines in series between the power source and the load.

8. The device of claim 7, wherein the inductors are characterized by respective inductances and the capacitor is characterized by a capacitance, and the inductances and capacitance are established for suppressing at least two predetermined frequencies in the power lines.

9. The device of claim 7, further comprising a metal oxide varistor coupled to the power lines in parallel with the load at an input side of the device.

10. The device of claim 7, wherein the capacitor is a first capacitor, and the device further comprises:

a third inductor in series with the first inductor;

a fourth inductor in series with the second inductor; and

a second capacitor coupled between an input side of the third inductor and an output side of the fourth inductor, whereby the device suppresses four or more predetermined frequencies.

11. The device of claim 7, in combination with the audio video load.

12. A method for suppressing noise at the power supply input of audio video equipment coupled to a source of 60 Hz ac power, the source having a first power line and a second power line, comprising the step of:

coupling a filter to the power lines, the filter having at least one circuit, the at least one circuit including;

at least a first inductor coupled to the first power line in series between the power source and the load,

at least a second inductor coupled to the second power line in series between the power source and the load, and

at least a first capacitor, the capacitor being coupled to the first power line upstream of the first inductor, the capacitor being coupled to the second power line downstream of the second inductor, whereby noise surges and at least two noise frequencies in one or more of the power lines are suppressed by the filter.

13. The method of claim 12, further comprising the step of:

establishing the capacitance of the capacitor and the inductances of the inductor as appropriate for suppressing at least two predetermined ac frequencies.

14. The method of claim 12, further comprising the step of coupling a metal oxide varistor to the power lines in parallel with the load at the input sides of the inductors.

15. The method of claim 12, wherein the capacitor is a first capacitor, and the method further comprises:

coupling a third inductor in series with the first inductor;

coupling a fourth inductor in series with the second inductor; and

coupling a second capacitor between an input side of the third inductor and an output side of the fourth inductor, whereby the filter suppresses four predetermined frequencies.