Apparatus and method for limiting leakage to ground current while optimizing output of a power supply adaptable for use with a motion sensor switch
DCFirst Claim
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, and wherein;
said regulator is further adapted to maintain said predetermined magnitude of said leakage current substantially constant in response to a variation in temperature of at least a portion of said regulator.
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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.
36 Citations
22 Claims
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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:
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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, and wherein;
said regulator is further adapted to maintain said predetermined magnitude of said leakage current substantially constant in response to a variation in temperature of at least a portion of said regulator.
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2. 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:
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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, and wherein;
said regulator limits and maintains said leakage current to said predetermined magnitude which is less than or equal to 500 μ
A.
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3. 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:
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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, and wherein said regulator comprises;
first and second transistors; and
first and second resistance elements;
the base and collector of said first transistor and the base and collector of said second transistor being adapted to receive respective voltages based on said AC voltage, and the emitter of said first transistor being adapted to output said DC voltage; and
said first resistance element having a first terminal coupled to said input terminal and a second terminal coupled to the base of said first transistor, and said 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. - View Dependent Claims (4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
a zener diode, coupled between the emitters of said first and second transistors, and being adapted to cause said regulator to maintain said leakage current substantially constant in response to a change in temperature of said regulator.
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5. An apparatus as claimed in claim 3, wherein:
said first resistance element has a resistance value in relation to a resistance value of said second resistance element which causes said regulator to limit and maintain said leakage current to said predetermined magnitude which is less than or equal to 500 μ
A.
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6. An apparatus as claimed in claim 3, wherein:
said first resistance element is a 10 MΩ
resistor and said second resistance element is a 6.81 kΩ
resistor.
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7. An apparatus as claimed in claim 3, wherein:
a ratio of a magnitude of resistance of said first resistance element and a magnitude of resistance of said second resistance element is about 1468.
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8. An apparatus as claimed in claim 3, wherein:
said second terminal of said first resistance element is directly connected to said base of said first transistor.
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9. An apparatus as claimed in claim 3, wherein:
said first and second terminals of said second resistance element are directly connected to the base of said first transistor and the emitter of said second transistor, respectively.
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10. An apparatus as claimed in claim 3, wherein:
said first and second transistors are NPN transistors.
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11. An apparatus as claimed in claim 3, wherein said regulator further comprises:
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a third resistance element having a first terminal coupled to said input terminal of said regulator and a second terminal coupled to the collector of said first transistor and the base of said second transistor; and
a fourth resistance element having a first terminal coupled to the emitter of said second transistor and a second terminal coupled to the emitter of said first transistor.
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12. An apparatus as claimed in claim 3, wherein said regulator further comprises:
a rectifier, adapted to generate said first voltage based on said AC voltage.
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13. An apparatus as claimed in claim 12, wherein:
said first and second terminals of said first resistance element are directly connected to an output terminal of said rectifier and said base of said first transistor, respectively.
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14. 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 the steps of:
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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;
maintaining a magnitude of said DC voltage substantially constant in response to a variation in said source AC voltage within said AC voltage range; and
maintaining said magnitude of said DC voltage substantially constant in response to a variation in temperature of at least a portion of said regulator.
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15. 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 the steps of:
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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, and wherein;
said leakage current limiting and maintaining step limits and maintains said leakage current to said predetermined magnitude which is less than or equal to 500 μ
A.
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16. 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 the steps of:
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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;
maintaining a magnitude of said DC voltage substantially constant in response to a variation in said source AC voltage within said AC voltage range;
generating a plurality of said DC output voltages based on said DC voltage generated in said generating step; and
maintaining a respective magnitude of each of said DC output voltages substantially constant in response to variations in said source AC voltage within said AC voltage range.
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17. A motion sensor switch, comprising:
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a motion sensor, adapted to sense a condition of a monitored area and output a signal indicative thereof; and
a power supply, adapted to power said motion sensor, said power supply comprising;
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 to said motion sensor;
a ground terminal adapted to receive a leakage current generated by said DC power supply in response to said source AC voltage; and
a regulator, 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 source AC voltage within an AC voltage range, and to output a DC voltage having a magnitude which remains substantially constant in response to a variation in said input AC voltage;
said power supply outputting said at least one DC output voltage based on said DC voltage. - View Dependent Claims (18, 19, 20, 21, 22)
said regulator is further adapted to maintain said predetermined magnitude of said leakage current substantially constant in response to a variation in temperature of at least a portion of said regulator.
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19. A motion sensor switch as claimed in claim 17, wherein:
said regulator limits and maintains said leakage current to said predetermined magnitude which is less than or equal to 500 μ
A.
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20. A motion sensor switch as claimed in claim 17, wherein:
said power supply outputs three said DC output voltages of different magnitudes to said motion sensor.
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21. A motion sensor switch as claimed in claim 17, wherein said regulator comprises:
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first and second transistors; and
first and second resistance elements;
the base and collector of said first transistor and the base and collector of said second transistor being adapted to receive respective voltages based on said source AC voltage, and the emitter of both said first and second transistors being adapted to output said DC voltage; and
said first resistance element having a first terminal coupled to said input terminal and a second terminal coupled to the base of said first transistor, and said 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.
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22. A motion sensor switch as claimed in claim 21, wherein:
said first resistance element has a resistance value in relation to a resistance value of said second resistance element which causes said regulator to limit and maintain said leakage current to said predetermined magnitude which is less than or equal to 500 μ
A.
Specification