Adjusting color temperature in a dimmable LED lighting system
First Claim
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1. A light emitting diode (LED) lighting system, comprising:
- a phase-angle dimmer switch;
a rectifier configured to rectify an AC voltage into a rectified input voltage having a shape and/or magnitude responsive to a dimming level set by the phase-angle dimmer switch;
a dimming detection module configured to receive the 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 single switching power regulator configured to generate a regulated current at an output of the single switching power regulator responsive to the target current level signal;
an initial LED string coupled to the output of the single switching power regulator;
a first LED string coupled to the output of the single switching power regulator through the initial LED string and configured to emit light of a first color temperature based on a first portion of the regulated current flowing through the first LED string;
a second LED string coupled to the output of the single switching power regulator through the initial LED string and configured to emit light of a second color temperature based on a second portion of the regulated current flowing through the second LED string, the second color temperature being different than the first color temperature; and
circuitry configured to allocate the regulated current between the first portion of the regulated current flowing through the first LED string and the second portion of the regulated current flowing through the second LED string responsive to changes in the desired brightness level such that a light output from the LED lighting system 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
20 Claims
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1. A light emitting diode (LED) lighting system, comprising:
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a phase-angle dimmer switch; a rectifier configured to rectify an AC voltage into a rectified input voltage having a shape and/or magnitude responsive to a dimming level set by the phase-angle dimmer switch; a dimming detection module configured to receive the 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 single switching power regulator configured to generate a regulated current at an output of the single switching power regulator responsive to the target current level signal; an initial LED string coupled to the output of the single switching power regulator; a first LED string coupled to the output of the single switching power regulator through the initial LED string and configured to emit light of a first color temperature based on a first portion of the regulated current flowing through the first LED string; a second LED string coupled to the output of the single switching power regulator through the initial LED string and configured to emit light of a second color temperature based on a second portion of the regulated current flowing through the second LED string, the second color temperature being different than the first color temperature; and circuitry configured to allocate the regulated current between the first portion of the regulated current flowing through the first LED string and the second portion of the regulated current flowing through the second LED string responsive to changes in the desired brightness level such that a light output from the LED lighting system 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, 8, 9, 10, 11)
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12. A method of operation in a light emitting diode (LED) lighting system, the method comprising:
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rectifying an AC voltage into a rectified input voltage having a shape and/or magnitude responsive to a dimming level set by a phase-angle dimmer switch; detecting a desired brightness level from the magnitude and/or shape of the rectified input voltage, and thereby generating a target current level signal that varies responsive to a variation in the desired brightness level; generating a regulated current at an output of a single switching power regulator responsive to the target current level signal; driving the regulated current through an initial LED string coupled to the output of the single switching power regulator; and controlling an allocation of the regulated current from the initial LED string between a first LED string and a second LED string, wherein the first LED string is configured to emit light of a first color temperature and the second LED string is configured to emit a light of a second color temperature, the second temperature being different than the first color temperature, the allocation of the regulated current being controlled such that an overall light emitted by the LED lighting system increases in redness responsive to a decrease in the desired brightness level. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20)
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Specification