Power supply filtering

• US 20030197998A1
• Filed: 05/20/2003
• Published: 10/23/2003
• Est. Priority Date: 01/10/2002
• Status: Active Grant

• Current Assignee: CommScope Technologies, LLC (CommScope Holding Company, Inc.)
• Original Assignee: ADC Telecommunications Incorporated (TE Connectivity Limited)
• Inventors: Coffey, Joseph, Hernandez, Delfino
• Granted Patent: US 7,082,041 B2
• Time in Patent Office: Days
• US Class Current: 361/118
• CPC Class Codes: H02M 1/36 Means for starting or stopping converters
• CPC Class Codes: Y10S 323/901 Starting circuits
• CPC Class Codes: Y10S 323/908 Inrush current limiters

Abstract

A power supply is filtered while the amount of in-rush current required by the capacitive charging of the filter is limited. A resistor may be placed in parallel with a relay where the parallel combination is in series with the filtering capacitor. The relay is open upon applying power to the filter and remains open while the capacitor at least partially charges to cause charging current to pass through the resistor and thereby limit in-rush current. The relay is closed thereafter to provide a short circuit around the resistor and thereby unrestrict filtering by the capacitor. Alternatively, a common mode choke is disposed between a capacitor across input nodes and a capacitor across output nodes, whereby the size of the capacitors may be reduced to limit the in-rush current due to the common mode choke. The power supply filter may be included as part of a power distribution panel.

Claims

1. A power supply filter, comprising:

first and second power supply nodes, wherein a power supply voltage is applied across the first and second power supply nodes;

a resistor and a capacitor in series between the first and second node;

a relay with a first set of contacts in parallel with the resistor, the relay having a first position to create an open circuit in parallel with the resistor and a second position to create a short circuit in parallel with the resistor; and

a control circuit operably coupled to the relay, wherein the control circuit holds the relay in the first position until the capacitor is at least partially charged relative to the power supply voltage and then moves the relay to the second position.

2. The power supply filter of claim 1, wherein the control circuit includes a comparator, and wherein the control circuit detects when to move the relay from the first position to the second position by the comparator comparing a voltage across the capacitor to the power supply voltage.

3. The power supply filter of claim 2, wherein the control circuit includes a relay control circuit with an input that is coupled to an output of the comparator and an output that is coupled to the relay, and wherein the comparator output signals the relay control circuit to move the relay to the second position when the voltage across the capacitor is approximately equal to the power supply voltage.

4. The power supply filter of claim 1, wherein the control circuit includes a timer, and wherein the control circuit detects when to move the relay to the second position by the timer detecting the expiration of a specific amount of time.

5. The power supply filter of claim 4, wherein the control circuit includes a relay control circuit with an input that is coupled to an output of the timer and an output that is coupled to the relay, and wherein the timer output signals the relay control circuit to move the relay to the second position when the amount of time has expired.

6. The power supply filter of claim 1, further comprising an inductor disposed between the first node and a power supply providing the power supply voltage.

7. The power supply filter of claim 1, wherein the relay has a second set of contacts, the second set connected in series with a light emitting diode between the first node and a ground such that when the relay is in the first position the second set of contacts creates an open circuit to prevent the light emitting diode from illuminating and when the relay is in the second position the second set of contacts creates a short circuit to illuminate the light emitting diode.

8. The power supply filter of claim 1, wherein the first node has a negative potential relative to the second node.

15. The method of claim 1, wherein the relay has a second set of contacts, the second set connected in series with a light emitting diode between the first node and a ground, the method further comprising:

when maintaining the relay in a first position to create an open circuit in parallel with the resistor, maintaining the second set of contacts create an open circuit to prevent the light emitting diode from illuminating; and

when the relay is in the second position, causing the second set of contacts create a short circuit to illuminate the light emitting diode.

16. The method of claim 1, wherein applying the power supply voltage across the first and second power supply nodes comprises applying a negative potential to the first node relative to the second node.

9. A method of filtering a power supply, comprising:

applying a power supply voltage across first and second power supply nodes to pass current through a resistor and to a capacitor, wherein the resistor and capacitor are in series between the first and second nodes;

maintaining a relay with a first set of contacts in parallel with the resistor in a first position to create an open circuit in parallel with the resistor; and

when the capacitor is at least partially charged relative to the power supply voltage, moving the relay to a second position to create a short circuit in parallel with the resistor.

10. The method of claim 9, further comprising applying the power supply voltage and a voltage across the capacitor to a comparator to determine when the relay should be moved to the second position.

11. The method of claim 10, further comprising:

outputting from the comparator a signal to a relay control circuit coupled to the relay; and

controlling the relay from the relay control circuit such that the relay remains in the first position until the output of the comparator indicates that the voltage across the capacitor is approximately equal to the power supply voltage.

12. The method of claim 9, further comprising starting a timer when power supply voltage is first applied across the first and second power supply nodes to determine when a specific amount of time has expired that indicates when the relay should be moved to the second position.

13. The method of claim 12, further comprising:

outputting from the timer a signal to a relay control circuit coupled to the relay; and

controlling the relay from the relay control circuit such that the relay remains in the first position until the output of the timer indicates that the specific amount of time has elapsed.

14. The method of claim 9, further comprising passing current through an inductor between a power supply providing the power supply voltage and the first node.

17. A power supply filter, comprising:

first and second power supply input nodes, wherein a power supply voltage is applied across the first and second power supply input nodes;

first and second power supply output nodes;

a first capacitor connected between the first and second power supply input nodes;

a second capacitor connected between the first and second power supply output nodes; and

a common mode choke electrically disposed between the first and second power supply input nodes and the first and second power supply output nodes such that current flows through the common mode choke in a first direction when passing between the first power supply input node and the first power supply output node and such that current flows through the common mode choke in an opposite direction from the first direction when passing between the second power supply output node and the second power supply input node.

18. The power supply filter of claim 17, wherein the first power supply input node and first power supply output node have a negative potential relative to the second power supply input node and the second power supply output node.

19. The power supply filter of claim 17, wherein the common mode choke is toroidal.

20. A method of filtering a power supply, comprising:

applying a power supply voltage across first and second power supply input nodes to pass current to a first capacitor connected across the first and second power supply input nodes, to pass current in a first direction between the first supply input node and a first power supply output node through a common mode choke and to a second capacitor connected across the first power supply output node and a second power supply output node, and to pass current in a second direction opposite the first direction between the second power supply output node and the second power supply input node through the common mode choke.

21. The method of claim 20, wherein the first power supply input node and the first power supply output node have a potential that is negative relative to the second power supply input node and the second power supply output node.

22. The method of claim 20, wherein the common mode choke is toroidal.

23. A power distribution panel, comprising:

an input voltage connector;

a filtering circuit having current in-rush control and a filtering capacitor, the filtering circuit being operable to receive voltage through the input voltage connector and the current in-rush control being operable to limit current drawn through the input voltage connector until the filtering capacitor is at least partially charged;

an output voltage connector; and

over-current protection device electrically connected between an output of the filtering circuit and the output voltage connector.

24. The power distribution panel of claim 23, wherein the in-rush control comprises a charging resistor in series with the filtering capacitor, a relay in parallel with the resistor, and a relay control operable to position the relay to create an open circuit upon the filtering circuit receiving voltage and position the relay to create a short circuit once the filtering capacitor is at least partially charged.

25. The power distribution panel of claim 24, wherein the relay control positions the relay based upon a comparison of the voltage received through the input connector with the voltage across the filtering capacitor.

26. The power distribution panel of claim 24, wherein the relay control positions the relay based upon expiration of a set amount of time from when the filter circuit receives the voltage.

27. The power distribution panel of claim 23, further comprising a faceplate, and wherein the filtering circuit includes a light emitting diode operable to illuminate when the filtering capacitor is at least partially charged, the light emitting diode being disposed on the faceplate.

28. The power distribution panel of claim 23, wherein the over-current protection device includes one or more fuses.

29. A power distribution panel, comprising:

an input voltage connector;

a filtering circuit having a first filtering capacitor connected across first and second input nodes, a second filtering capacitor connected across first and second output nodes, and a common mode choke electrically connected between the input and output nodes such that current flows through the common mode choke in a first direction between the first input node and the first output node and flows through the common mode choke in a second direction opposite the first between the second output node and first output node, the filtering circuit being operable to receive voltage across the input nodes through the input voltage connector;

an output voltage connector; and

an over-current protection device electrically connected between an output node of the filtering circuit and the output voltage connector.

30. The power distribution panel of claim 29, wherein the common mode choke is toroidal.

31. The power distribution panel of claim 29, wherein the over-current protection device includes at least one fuse.

32. The power distribution panel of claim 29, further comprising a faceplate, and wherein the filtering circuit includes a light emitting diode operable to illuminate when the filtering capacitor is at least partially charged, the light emitting diode being disposed on the faceplate.