Apparatus and method for limiting leakage to ground current while optimizing output of a power supply adaptable for use with a motion sensor switch
First 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.
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Accused Products
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.
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Citations
10 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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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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:
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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. - View Dependent Claims (10)
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Specification