Backlighting circuits including brownout detection circuits responsive to a current through at least one light emitting diode and related methods
First Claim
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1. A backlighting circuit for a user interface of an electronic device, said backlighting circuit comprising:
- at least one light emitting diode optically coupled to the user interface wherein said at least one light emitting diode provides backlighting for the user interface;
a current source electrically coupled in series with said at least one light emitting diode wherein said current source controls a current through said at least one light emitting diode; and
a brownout detection circuit wherein said brownout detection circuit determines a brownout condition for the user interface responsive to said current through said at least one light emitting diode falls below a predetermined threshold wherein said brownout detection circuit determines a brownout condition using a comparison between a reference signal and a feedback signal from said current source; and
a control circuit wherein said control circuit is electrically coupled to said brownout detection circuit and wherein said control circuit turns said current source off in response to a determination that a brownout condition has occurred.
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Abstract
A backlighting circuit for user interface in an electronic device includes at least one light emitting diode optically coupled to the user interface wherein the at least one light emitting diode provides backlighting for the user interface. A current source is electrically coupled in series with the at least one light emitting diode wherein the current source controls a current through the at least one diode. In addition, a brownout detection circuit determines a brownout condition for the user interface responsive to the current through the diode. Related communications devices and methods are also discussed.
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Citations
20 Claims
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1. A backlighting circuit for a user interface of an electronic device, said backlighting circuit comprising:
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at least one light emitting diode optically coupled to the user interface wherein said at least one light emitting diode provides backlighting for the user interface; a current source electrically coupled in series with said at least one light emitting diode wherein said current source controls a current through said at least one light emitting diode; and a brownout detection circuit wherein said brownout detection circuit determines a brownout condition for the user interface responsive to said current through said at least one light emitting diode falls below a predetermined threshold wherein said brownout detection circuit determines a brownout condition using a comparison between a reference signal and a feedback signal from said current source; and a control circuit wherein said control circuit is electrically coupled to said brownout detection circuit and wherein said control circuit turns said current source off in response to a determination that a brownout condition has occurred. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method for providing backlighting for a user interface of an electronic device including a user interface and at least one light emitting diode optically coupled to the user interface wherein the at least one light emitting diode provides backlighting for the user interface, said method comprising the step of:
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determining a brownout condition for said at least one diode responsive to a current through said at least one light emitting diode falling below a predetermined threshold wherein determining the brownout condition comprises comparing a feedback signal representative of a current through the at least one diode with a reference signal; and turning said at least one light emitting diode off in response to a determination that a brownout condition has occurred. - View Dependent Claims (11)
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12. A backlighting circuit for a user interface of an electronic device, said backlighting circuit comprising:
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at least one light emitting diode optically coupled to the user interface wherein said at least one light emitting diode provides backlighting for the user interface; a constant current source electrically coupled in series with said at least one light emitting diode wherein said constant current source controls a current through said at least one light emitting diode in response to a comparison between a reference signal and a feedback signal from said constant current source; a brownout detection circuit wherein said brownout detection circuit determines a brownout condition for the user interface responsive to said feedback signal wherein said brownout detection circuit determines that said brownout condition has occurred when said current through said at least one diode falls below a predetermined threshold; and a control circuit wherein said control circuit is electrically coupled to said brownout detection circuit and wherein said control circuit turns said constant current source off in response to a determination that a brownout condition has occurred. - View Dependent Claims (13, 14, 15, 16, 17, 18)
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19. A method for providing backlighting for a user interface of an electronic device including a user interface and at least one light emitting diode optically coupled to the user interface wherein the at least one light emitting diode provides backlighting for the user interface, said method comprising the step of:
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comparing a feedback signal representative of a current through the at least one light emitting diode with a reference signal; controlling a current through the at least one light emitting diode in response to said comparison between said reference signal and said feedback signal; and determining a brownout condition for the user interface responsive to comparing the feedback signal representative of the current through the at least one diode with the reference signal to determine that said current through said at least one light emitting diode has fallen below a predetermined threshold; and turning the electronic device off in response to a determination that a brownout condition has occurred. - View Dependent Claims (20)
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Specification