ADJUSTING COLOR TEMPERATURE IN A DIMMABLE LED LIGHTING SYSTEM
First Claim
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1. A light emitting diode (LED) controller for a switching power converter, comprising:
- a dimming detection module configured to receive a rectified input voltage, to detect a desired brightness level from the magnitude and/or shape of the rectified input voltage, and to thereby generate a target current level signal that varies responsive to a variation of the desired brightness level;
a regulator configured to regulate a cycling of a power switch to generate a regulated current at an output of the switching power converter responsive to the target current level signal; and
circuitry configured to allocate the regulated current between a first portion of the regulated current flowing through a first LED string and the second portion of the regulated current flowing through a second LED string responsive to changes in the desired brightness level such that a light output from the first LED string and the second LED string increases in redness responsive to a decrease in the desired brightness level, the circuitry comprising;
a first switch coupled in series with the first LED string, wherein a duty cycle of ON and OFF times of the first switch is responsive to a first switch control signal; and
a color control module configured to generate the first switch control signal responsive to the target current level.
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Abstract
A LED lighting system, such as a dimmable LED lamp, that may simulate the performance of an incandescent bulb. LED strings of different colors may be connected to the output of a single LED driver that regulates an overall intensity of light produced by the LED lighting system. The color of the LED lighting system may be controlled by circuitry, such as one or more switches, that allocates current between the LED strings to change the color temperature of light emitted by the LED lighting system as the light intensity changes.
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Citations
16 Claims
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1. A light emitting diode (LED) controller for a switching power converter, comprising:
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a dimming detection module configured to receive a rectified input voltage, to detect a desired brightness level from the magnitude and/or shape of the rectified input voltage, and to thereby generate a target current level signal that varies responsive to a variation of the desired brightness level; a regulator configured to regulate a cycling of a power switch to generate a regulated current at an output of the switching power converter responsive to the target current level signal; and circuitry configured to allocate the regulated current between a first portion of the regulated current flowing through a first LED string and the second portion of the regulated current flowing through a second LED string responsive to changes in the desired brightness level such that a light output from the first LED string and the second LED string increases in redness responsive to a decrease in the desired brightness level, the circuitry comprising; a first switch coupled in series with the first LED string, wherein a duty cycle of ON and OFF times of the first switch is responsive to a first switch control signal; and a color control module configured to generate the first switch control signal responsive to the target current level. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method of operation for a light emitting diode (LED) controller for a switching power converter, the method comprising:
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detecting a desired brightness level from the magnitude and/or shape of a rectified input voltage from a phase cut dimmer switch; generating a target current level signal that varies responsive to a variation in the desired brightness level; cycling a power switch to drive a regulated current through an output of the switching power converter; and controlling an allocation of the regulated current between a first LED string and a second LED string, the allocation of the regulated current being controlled such that an overall light emitted by the first LED string and the second LED string increases in redness responsive to a decrease in the desired brightness level. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15, 16)
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Specification