Lighting assembly, circuits and methods
First Claim
Patent Images
1. A circuit, comprising:
- at least a first light emitting device coupled between a first power supply node and a first internal node;
a current sense circuit;
a disable circuit having a first disable path that couples the first internal node to a first power supply node in a passive mode; and
a sense isolation circuit that, in the passive mode, electrically isolates the current sense circuit from current flowing through at least the first light emitting device, and in an operational mode couples the current sense circuit to the first internal node, wherein the at least one lighting device comprises light emitting diodes (LEDs), and wherein the LEDs are configured to be connected in series between the first power supply node and the first internal node so that the LEDs are reverse biased when a voltage difference between the power supply node and the first internal mode falls below a predetermined minimum difference, whereinwhen switching from an operational mode to the passive mode, the disable circuit couples the first internal node to the first power supply node after the sense isolation circuit isolates the current sense circuit from current flowing through at least the lighting device connection point; and
when switching from the passive mode to the operational mode, the disable circuit isolates the first internal node from the first power supply node before the sense isolation circuit couples the current sense circuit to current flowing through at least the lighting device connection point.
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Abstract
A circuit in accordance with one embodiment of the invention can include an LED drive circuit that may isolate a sense circuit from a supply voltage in a passive mode, and maintain a predetermined voltage difference between the sense circuit and the supply voltage in an operational mode.
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Citations
16 Claims
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1. A circuit, comprising:
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at least a first light emitting device coupled between a first power supply node and a first internal node; a current sense circuit; a disable circuit having a first disable path that couples the first internal node to a first power supply node in a passive mode; and a sense isolation circuit that, in the passive mode, electrically isolates the current sense circuit from current flowing through at least the first light emitting device, and in an operational mode couples the current sense circuit to the first internal node, wherein the at least one lighting device comprises light emitting diodes (LEDs), and wherein the LEDs are configured to be connected in series between the first power supply node and the first internal node so that the LEDs are reverse biased when a voltage difference between the power supply node and the first internal mode falls below a predetermined minimum difference, wherein when switching from an operational mode to the passive mode, the disable circuit couples the first internal node to the first power supply node after the sense isolation circuit isolates the current sense circuit from current flowing through at least the lighting device connection point; and when switching from the passive mode to the operational mode, the disable circuit isolates the first internal node from the first power supply node before the sense isolation circuit couples the current sense circuit to current flowing through at least the lighting device connection point. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A circuit comprising:
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at least one lighting device connection point; a current control circuit coupled between a first internal node and a second power supply node that controls a current flowing through the at least one lighting device connection point; a disable circuit having a first disable path that couples the first internal node to a first power supply node in a passive mode; and a sense isolation circuit that, in the passive mode, electrically isolates a current sense circuit from current flowing through at least one lighting device connection point, and wherein; when switching from an operational mode to the passive mode, the disable circuit couples the first internal node to the first power supply node after the sense isolation circuit isolates the current sense circuit from current flowing through at least the lighting device connection point; and when switching from the passive mode to the operational mode, the disable circuit isolates the first internal node from the first power supply node before the sense isolation circuit couples the current sense circuit to current flowing through at least the lighting device connection point. - View Dependent Claims (9, 10, 11, 12, 13, 14)
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15. A method, comprising:
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in an operational mode, controlling an illumination current through at least one lighting device in response to sensing at least a portion of the illumination current with a sense circuit; in a passive mode, electrically isolating the sense circuit from sensing the illumination current, wherein the at least one lighting device comprises two ends; in the passive mode, coupling both ends of the at least one lighting device to a same disable potential to prevent current from flowing through the at least one lighting device; when switching from the operational mode to the passive mode, coupling both ends of the at least one lighting device to the same disable potential after isolating the sense circuit from sensing the illumination current; and when switching from the passive mode to the operational mode, disabling a first end of the two ends from the a power supply node before coupling the sense circuit to a current flowing through at least a lighting device connection point.
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16. A method comprising:
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in an operational mode, controlling an illumination current through at least one lighting device in response to sensing at least a portion of the illumination current with a sense circuit; in a passive mode, electrically isolating the sense circuit from sensing the illumination current, wherein the at least one lighting device comprises two ends; in the passive mode, coupling both ends of the at least one lighting device to a same disable potential to prevent current from flowing through the at least one lighting device; when switching from the operational mode to the passive mode, coupling both ends of the at least one lighting device to the same disable potential after isolating the sense circuit from sensing the illumination current; and when switching from the passive mode to the operational mode, disconnecting one end of the at least one lighting device from the disable potential before connecting the sense circuit to sense the illumination current.
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Specification