Apparatus and method for limiting leakage to ground current while optimizing output of a power supply adaptable for use with a motion sensor switch

• US 6,472,853 B2
• Filed: 08/07/2001
• Issued: 10/29/2002
• Est. Priority Date: 06/28/1999
• Status: Expired due to Term

• Current Assignee: Hubbell, Inc.
• Original Assignee: Hubbell, Inc.
• Inventors: Blau, David A., Baldwin, John R., Nishihira, Thomas S.
• Primary Examiner(s): Riley, Shawn
• Application Number:
  US09/922,771
• Publication Number:
  US 20020000794A1
• Time in Patent Office: 448 Days
• Field of Search: 323/269, 323/350, 323/278, 323/909, 340/540, 327/439, 327/463, 700/12, 369/170, 307/116
• US Class Current: 323/269
• CPC Class Codes: G05F 1/46 wherein the variable actually regulated by the final control device is dc G05F1/625 takes precedence

Abstract

A method and apparatus for regulating a DC power supply, adaptable for use with a motion sensor switch, by limiting the leakage to ground current of the power supply to comply with U.L. Standards while also enabling the DC power supply to provide a stable DC output voltage which is essentially unaffected by changes in magnitude of the AC supply voltage or changes in ambient temperature. The method and apparatus employs first and second transistors, in which the base and collector of the first transistor and the base and collector of the second transistor are coupled to receive a voltage based on the AC supply voltage, and the emitter of both the first and second transistors are coupled to drive an output circuit of the DC power supply. The emitter of the second transistor is also coupled via a first resistor to the base of the first transistor, and the collector of the second transistor is also coupled via a second resistor to the base of the first transistor. The magnitudes of the first and second resistors are determined such that the leakage to ground current remains substantially constant over a range of magnitudes of the AC supply voltage, and the emitters of the first and second transistors drive the output circuit to provide at a plurality of output terminals a plurality of stable DC output voltages having respective magnitudes which are essentially unaffected by changes in the magnitude of the AC supply voltage. A zener diode can be coupled between the emitters of the first and second transistors to cause the magnitudes of the stable DC output voltages to be essentially unaffected by changes in temperature.

Claims

1. An apparatus for regulating a DC power supply, said DC power supply being adaptable for use with a motion sensor switch and having a power supply input terminal adapted to receive a source AC voltage, at least one power supply output terminal adapted to output at least one DC output voltage, and a ground terminal, said DC power supply generating in response to said source AC voltage a leakage current flowing to said ground terminal, said apparatus comprising:

an input terminal, adapted to receive an AC voltage based on said source AC voltage; and

a regulator, coupled to said input terminal to receive said AC voltage, and being adapted to limit said leakage current to a predetermined magnitude, to maintain said predetermined magnitude of said leakage current substantially constant in response to a variation in said input AC voltage within an AC voltage range, and to output a DC voltage having a magnitude which remains substantially constant in response to variations in said input AC voltage, said power supply outputting said at least one DC output voltage based on said DC voltage.

2. An apparatus as claimed in claim 1, wherein said regulator comprises:

first and second transistors;

a diode having an anode coupled to said input terminal and a cathode;

a first resistance element having a first terminal coupled to said cathode of said diode and a second terminal coupled to the base of said first transistor;

a second resistance element having a first terminal coupled to the base of said first transistor and a second terminal coupled to the emitter of said second transistor;

a third resistance element having a first terminal coupled to the emitter of said second transistor and a second terminal; and

a zener diode having an anode coupled to the second terminal of said third resistance element and a cathode coupled to the emitter of said first transistor.

3. An apparatus as claimed in claim 2, wherein said regulator further comprises:

a fourth resistance element having a first terminal coupled to the cathode of said diode and a second terminal coupled to the base of the first transistor; and

a fifth resistance element having a first terminal coupled to the cathode of said diode and a second terminal coupled to the collector of said first transistor.

4. An apparatus as claimed in claim 2, wherein:

each of said first and second transistors is an npn transistor.

5. An apparatus as claimed in claim 1, wherein said regulator comprises:

a first transistor having an emitter coupled to said input terminal;

a second transistor component having at least one second transistor, such that the base of one said second transistor is coupled to the collector of said first transistor and the emitter of another said second transistor is coupled to the base of said first transistor; and

a zener diode having an anode coupled to the collector of said first transistor and a cathode coupled to the collectors of said second transistors.

6. An apparatus as claimed in claim 5, wherein said regulator further comprises:

a resistance element, coupled between said anode of said zener diode and said collector of said first transistor; and

a second zener diode having an anode coupled to the emitter of said first transistor and a cathode coupled to said input terminal.

7. An apparatus as claimed in claim 5, wherein:

said second transistor component includes two second transistors, the base of one of said second transistors being coupled to the emitter of the other said second transistor.

8. An apparatus as claimed in claim 7, wherein:

said first transistor and each said second transistor is a pnp transistor.

9. A method for regulating a DC power supply, said DC power supply being adaptable for use with a motion sensor switch and having a power supply input terminal adapted to receive a source AC voltage, at least one power supply output terminal adapted to output at least one DC output voltage, and a ground terminal, said DC power supply generating in response to said source AC voltage a leakage current flowing to said ground terminal, said method comprising:

limiting said leakage current to a predetermined magnitude, and maintaining said predetermined magnitude of said leakage current substantially constant in response to variations in said source AC voltage within an AC voltage range;

generating a DC voltage based on said source AC voltage; and

maintaining a magnitude of said DC voltage substantially constant in response to a variation in said source AC voltage within said AC voltage range.

10. A method as claimed in claim 9, wherein:

said limiting step includes inputting said source AC voltage into a regulator comprising a transistor and resistor configuration;

said generating step includes outputting said DC voltage at an output terminal of said regulator; and

said maintaining step includes continuing to input said source AC voltage into said regulator when said variation in said source AC voltage occurs, so that said generating step outputs said substantially constant DC voltage at said output terminal of said regulator.

11. An apparatus for regulating a DC power supply, said DC power supply being adaptable for use with a motion sensor switch and having a power supply input terminal adapted to receive a source AC voltage, at least one power supply output terminal adapted to output at least one DC output voltages, and a ground terminal, said DC power supply generating in response to said source AC voltage a leakage current flowing to said ground terminal, said apparatus comprising:

an input terminal, adapted to receive an AC voltage based on said source AC voltage; and

a regulator, coupled to said input terminal to receive said AC voltage and including first and second elements, and being adapted to limit said leakage current to a predetermined magnitude as governed by a value of said first element in relation to a value of said second element, to maintain said predetermined magnitude of said leakage current substantially constant in response to a variation in said input AC voltage within an AC voltage range, and to output a DC voltage having a magnitude which remains substantially constant in response to variations in said input AC voltage, said power supply outputting said at least one DC output voltage based on said DC voltage.

12. An apparatus as claimed in claim 11, wherein:

said first element comprises a first resistor and said second element comprises a second resistor.

13. An apparatus as claimed in claim 11, wherein said regulator comprises:

first and second transistors;

a diode having an anode coupled to said input terminal and a cathode;

said first element configured to include a first resistance element having a first terminal coupled to said cathode of said diode and a second terminal coupled to the base of said first transistor;

said second element configured to include a second resistance element having a first terminal coupled to the base of said first transistor and a second terminal coupled to the emitter of said second transistor;

a third resistance element having a first terminal coupled to the emitter of said second transistor and a second terminal; and

a zener diode having an anode coupled to the second terminal of said third resistance element and a cathode coupled to the emitter of said first transistor.

14. An apparatus as claimed to claim 13, wherein said regulator further comprises:

a fourth resistance element having a first terminal coupled to the cathode of said diode and a second terminal coupled to the base of the first transistor; and

a fifth resistance element having a first terminal coupled to the cathode of said diode and a second terminal coupled to the collector of said first transistor.

15. An apparatus as claimed in claim 13, wherein:

each of said first and second transistors is an npn transistor.

16. An apparatus an claimed in claim 11, wherein said regulator comprises:

a first transistor having an emitter coupled to said input terminal;

a second transistor component having at least one second transistor, such that the base of one said second transistor is coupled to the collector of said first transistor and the emitter of another said second transistor is coupled to the base of said first transistor; and

a zener diode having an anode coupled to the collector of said first transistor and a cathode coupled to the collectors of said second transistors.

17. An apparatus as claimed in claim 16, wherein said regulator further comprises:

a resistance element, coupled between said anode of said zener diode and said collector of said first transistor; and

a second zener diode having an anode coupled to the emitter of said first transistor and a cathode coupled to said input terminal.

18. An apparatus as claimed in claim 16, wherein:

said second transistor component includes two second transistors, the base of one of said second transistors being coupled to the emitter of the other said second transistor.

19. An apparatus as claimed in claim 18, wherein:

said first transistor and each said second transistor is a pnp transistor.

20. A method for regulating a DC power supply, said DC power supply being adaptable for use with a motion sensor switch and having a power supply input terminal adapted to receive a source AC voltage, at least one power supply output terminal adapted to output at least one DC output voltage, first and second elements coupled between said input and output terminals, and a ground terminal, said DC power supply generating in response to said source AC voltage a leakage current flowing to said ground terminal, said method comprising;

limiting said leakage current to a predetermined magnitude, as governed by a value of said first element in relation to a value of said second element, and maintaining said predetermined magnitude of said leakage current substantially constant in response to variations in said source AC voltage within an AC voltage range;

generating a DC voltage based on said source AC voltage; and

maintaining a magnitude of said DC voltage substantially constant in response to a variation in said source AC voltage within said AC voltage range.

21. A method as claimed in claim 20, wherein:

said limiting step includes inputting said source AC voltage into a regulator comprising a transistor and resistor configuration comprising said first and second elements;

said generating step includes outputting said DC voltage at an output terminal of said regulator; and

said maintaining step includes continuing to input said source AC voltage into said regulator when said variation in said source AC voltage occurs, so that said generating step outputs said substantially constant DC voltage at said output terminal of said regulator.

22. A method as claimed in claim 20, wherein:

said first element includes a first resistor and said second element includes a second resistor.