Smooth brightness adjustment for color-tunable light source module
First Claim
1. A method comprising:
- generating a first pulse sequence using a first pulse-width modulator, the first pulse sequence having a first pulse period corresponding to a high frequency;
generating a modulating pulse sequence using a second pulse-width modulator, the modulating pulse sequence having a second pulse period corresponding to a low frequency,wherein generating each modulating pulse in the modulating pulse sequence includes perturbing a width of the modulating pulse by a perturbation amount, the perturbation amount being in a range corresponding to the first pulse period, and wherein different modulating pulses in the sequence are perturbed by different amounts; and
modulating the pulse train using the sequence of modulating pulses to produce an output electrical signal.
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Abstract
A first sequence of pulses having a high frequency can be modulated using a second sequence of pulses having a lower frequency. The pulse width of the second sequence of pulses can be perturbed from a nominal pulse width on a per-pulse basis, within a perturbation range corresponding to the pulse period of the first sequence of pulses. In one application, the resulting output can be used to drive LEDs. In some instances, two or more channels of LEDs of different colors can be supported, with the pulse width of the first pulse sequence being selected per-channel based on a desired light color and the nominal pulse width of the second pulse sequence being selected for all channels based on a desired brightness.
19 Citations
24 Claims
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1. A method comprising:
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generating a first pulse sequence using a first pulse-width modulator, the first pulse sequence having a first pulse period corresponding to a high frequency; generating a modulating pulse sequence using a second pulse-width modulator, the modulating pulse sequence having a second pulse period corresponding to a low frequency, wherein generating each modulating pulse in the modulating pulse sequence includes perturbing a width of the modulating pulse by a perturbation amount, the perturbation amount being in a range corresponding to the first pulse period, and wherein different modulating pulses in the sequence are perturbed by different amounts; and modulating the pulse train using the sequence of modulating pulses to produce an output electrical signal. - View Dependent Claims (2, 3, 4, 5)
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6. A method of controlling brightness and color temperature in a light source device having a plurality of independently addressable groups of LEDs, wherein the LEDs in each group emit light of a different color, the method comprising:
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determining a target color temperature and a brightness set-point based at least in part on a received control signal; computing, for each of a plurality of output channels, a nominal pulse width and a number of pulses to include in a pulse train, the pulse train having a duration defined as a fixed number of pulse periods, the computation being based at least in part on the target color temperature and the brightness set-point; computing a perturbation amount; computing, for each of the output channels, a perturbed pulse width from the nominal pulse width and the perturbation amount; generating, on each of the plurality of output channels, a pulse train, the pulse train including the number of pulses computed for that output channel, wherein at least one of the pulses in the pulse train has a width equal to the perturbed pulse width; converting each of the pulse trains to an operating current; and delivering each of the operating currents to a different one of the independently addressable groups of LEDs. - View Dependent Claims (7, 8, 9)
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10. A light source module comprising:
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an emitter having a plurality of LEDs, the plurality of LEDs being electrically connected into two or more independently addressable groups of LEDs, wherein the LEDs in each group emit light of a different color; and a current source module for each group, wherein each current source module provides a current based on a color pulse sequence modulated by a brightness pulse sequence, the color pulse sequence having a first pulse period corresponding to a high frequency and a first pulse width selected based on a target light color, the brightness pulse sequence having a second pulse period corresponding to a low frequency and a nominal pulse width selected based on a target light brightness, wherein a pulse width of each pulse in the brightness pulse sequence is perturbed from the nominal pulse width by a perturbation amount, the perturbation amount being in a range corresponding to the first pulse period, and wherein different brightness pulses in the brightness pulse sequence are perturbed by different amounts. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
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Specification