Color temperature control of a lighting device

The lighting device may be configured to perform black body curve fading. For example, the control circuit may be configured to control the drive circuit such that the light emitted by the lighting load is adjusted (e.g., faded) along a black body curve. The control circuit may be configured to determine whether to fade from an initial color to a destination color in a Correlated Color Temperature (CCT) chromaticity space or an XY chromaticity space. The control circuit may be configured to determine whether the initial color and/or the destination color are on the black body curve. When the initial color and the destination color are determined to be on the black body curve, the control circuit may be configured to control the drive circuit such that the light emitted by the lighting device is adjusted from the initial color to the destination color along the black body curve.

BACKGROUND

Lamps and displays using efficient lighting devices, such as light-emitting diodes (LED) lighting devices, for illumination are becoming increasingly popular in many different markets. LED lighting devices provide a number of advantages over traditional lighting devices, such as incandescent and fluorescent lamps. For example, LED lighting devices may have a lower power consumption and a longer lifetime than traditional lighting devices. In addition, the LED lighting devices may have no hazardous materials, and may provide additional specific advantages for different applications. When used for general illumination, LED lighting devices provide the opportunity to adjust the color (e.g., from white, to blue, to green, etc.) or the color temperature (e.g., from warm white to cool white) of the light emitted from the LED lighting devices to produce different lighting effects.

A multi-colored LED illumination device may have two or more different colors of LED emission devices (e.g., LED emitters) that are combined within the same package to produce light (e.g., white or near-white light). There are many different types of white light LED lighting devices on the market, some of which combine red, green, and blue (RGB) LED emitters; red, green, blue, and yellow (RGBY) LED emitters; phosphor-converted white and red (WR) LED emitters; red, green, blue, and white (RGBW) LED emitters, etc. By combining different colors of LED emitters within the same package, and driving the differently-colored emitters with different drive currents, these multi-colored LED illumination devices may generate white or near-white light within a wide gamut of color points or correlated color temperatures (CCTs) ranging from warm white (e.g., approximately 2600 K-3700 K), to neutral white (e.g., approximately 3700 K-5000 K) to cool white (e.g., approximately 5000 K-8300 K). Some multi-colored LED illumination devices also may enable an intensity (e.g., lighting intensity and/or brightness) and/or color of the illumination to be changed to a particular set point. These tunable illumination devices may all produce the same color and color rendering index (CRI) when set to a particular dimming level and chromaticity setting (e.g., color set point) on a standardized chromaticity diagram.

SUMMARY

As described herein, a lighting device (e.g., a controllable light-emitting diode (LED) illumination device) may be responsive to wireless signals (e.g., radio-frequency signals). For example, the lighting device may include a wireless communication circuit that is configured to communicate wireless messages. The lighting device may include a lighting load (e.g., one or more emitter modules) configured to emit light. The lighting device may include a drive circuit for controlling the lighting load to emit light. The lighting device may include a control circuit configured to control the drive circuit.

The lighting device may be configured to perform black body curve fading. For example, the control circuit may be configured to control the drive circuit such that the light emitted by the lighting load is adjusted (e.g., faded) along a black body curve. The drive circuit may be configured to control the lighting load to emit light having a first color. The control circuit may be configured to receive, via the wireless communication circuit, a first message indicating a second color. The first color may be an initial color. The second color may be a destination color. The first message may include a fade request (e.g., in an XY chromaticity space). The fade request may include fade information associated with the second color. The second color may be indicated in an XY chromaticity space, a Correlated Color Temperature (CCT) chromaticity space, or another color space. The control circuit may be configured to determine whether to fade from the first color to the second color in the CCT chromaticity space or the XY chromaticity space.

The control circuit may be configured to determine whether the first color and/or the second color are on the black body curve. The first color and/or the second color may be determined to be on the black body curve when they are within a threshold value from the black body curve. The threshold value may be a delta uv measurement. When the first color and the second color are determined to be on the black body curve, the control circuit may be configured to control the drive circuit such that the light emitted by the lighting device is adjusted from the first color to the second color along the black body curve.

The control circuit may be configured to convert the first color and/or the second color to the CCT chromaticity space (e.g., from the XY chromaticity space). The first color and/or the second color may be converted to the CCT chromaticity space using one or more (e.g., a set of) equations and/or a look-up table stored in a memory of the lighting device. The control circuit may be configured to adjust the first color to the second color in the CCT chromaticity space. For example, the control circuit may perform a fade between the first color and the second color along the black body curve. For example, the control circuit may perform the fade according to a linear relationship between color (e.g., color temperature) and time. In addition, the control circuit may perform the fade according to a non-linear relationship between color and time, such that a perceived change in the color is approximately linear with respect to time. The control circuit may determine a plurality of CCT values along the black body curve between the first color and the second color. The plurality of CCT values may be associated with the linear or non-linear relationship between color and time. The control circuit may be configured to convert each of the plurality of CCT chromaticity values into the XY chromaticity space to determine a plurality of XY chromaticity coordinates. For example, the control circuit may be configured to convert each of the plurality of CCT chromaticity values into a plurality of uv chromaticity values. The control circuit may then be configured to convert the plurality of uv chromaticity values into the plurality of XY chromaticity coordinates.

The control circuit may be configured to control the drive circuit based on the plurality of XY chromaticity coordinates. For example, the control circuit may be configured to sequentially send each of the plurality of XY chromaticity coordinates to the drive circuit at respective time instances. The control circuit may be configured to determine a time schedule (e.g., such as a time delay between adjacent XY chromaticity coordinates) and may send the plurality of XY chromaticity coordinates to the drive circuit according to the time schedule. The lighting device may include one or more sensors configured to measure a color of the light emitted by the lighting device. The control circuit may be configured to compare the measured color to the second color. If the measured color is different than the second color by more than a predetermined value, the control circuit may be configured to adjust the control of the lighting load until the measure color is within the predetermined value of the second color.

The lighting device may be configured to adjust a color of light emitted by the lighting device based on a light level of ambient light proximate to the lighting device. The lighting device may be configured to measure the light level and/or a first color temperature of the ambient light proximate to the lighting device. The lighting device may determine whether the first color temperature is less than a red threshold temperature or greater than a blue threshold temperature at the determined light level. If the first color temperature is less than the red threshold temperature at the determined light level, the lighting device may control the lighting load such that the light emitted by the lighting device comprises a second color temperature that is equal to or greater than the red threshold temperature at the determined light level. If the first color temperature is greater than the blue threshold temperature at the determined light level, the lighting device may control the lighting load such that the light emitted by the lighting device comprises a third color temperature that is equal to or less than the blue threshold temperature at the determined light level. The lighting device may be configured to determine a CCT-illuminance curve (e.g., one or more values of the CCT-illuminance curve) to use. The lighting device may determine, using the determined CCT-illuminance curve, a present color temperature based on the illuminance level of ambient light. The lighting device may control respective intensities of the plurality of emitters to emit light at the determined present color temperature.

The lighting device may be configured to control a lighting load using one or more dimming curves. For example, the lighting device may switch dimming curves at a low ambient light level. The lighting device may be configured to determine an ambient light level proximate to the lighting device. The lighting device may be configured to compare the ambient light level to a predetermined threshold. If the ambient light level is greater than the predetermined threshold, the lighting device may be configured to control the lighting load according to a first dimming curve. If the ambient light level is less than a predetermined threshold, the lighting device may be configured to control the lighting load according to a second dimming curve.

DETAILED DESCRIPTION

FIG.1is a simplified perspective view of an example illumination device, such as a lighting device100(e.g., a light-emitting diode (LED) lighting device). The lighting device100may have a parabolic form factor and may be a parabolic aluminized reflector (PAR) lamp. The lighting device100may include a housing110and a lens112(e.g., an exit lens), through which light from an internal lighting load (not shown) may shine. The lighting device100may include a screw-in base114that may be configured to be screwed into a standard Edison socket for electrically coupling the lighting device100to an alternating-current (AC) power source.

FIG.2is an exploded view of another example lighting device200(e.g., an LED lighting device) having a parabolic form factor (e.g., which may have a similar assembly as the lighting device100shown inFIG.1). The lighting device200may include an emitter housing210that includes a heat sink212and a reflector214(e.g., a parabolic reflector), and a lens216(e.g., an exit lens). The lighting device200may include a lighting load, such as an emitter module220, that may include one or more emission LEDs. The emitter module220may be enclosed by the emitter housing210and may be configured to shine light through the lens216. The lens216may be made of any suitable material, for example glass. The lens216may be transparent or translucent and may be flat or domed, for example. The reflector214may shape the light produced by the emission LEDs within the emitter module220into an output beam. The reflector216may include planar facets218(e.g., lunes) that may provide some randomization of the reflections of the light rays emitted by the emitter module220prior to exiting lighting device220through the lens216. The lens216may include an array of lenslets (not shown) formed on both sides of the lens216. An example of a lighting device having a lens with lenslets is described in greater detail in U.S. Pat. No. 9,736,895, issued Aug. 15, 2017, entitled COLOR MIXING OPTICS FOR LED ILLUMINATION DEVICE, the entire disclosure of which is hereby incorporated by reference.

The lighting device200may include a driver housing230that may be configured to house a driver printed circuit board (PCB)232on which the electrical circuitry of the lighting device200may be mounted. The lighting device200may include a screw-in base234that may be configured to be screwed into a standard Edison socket for electrically coupling the lighting device200to an alternating-current (AC) power source. The screw-in base234may be attached to the driver housing230and may be electrically coupled to the electrical circuitry mounted to the driver PCB232. The driver PCB232may be electrically connected to the emitter module220, and may include one or more drive circuits and/or one or more control circuits for controlling the amount of power delivered to the emitter LEDs of the emitter module220. The driver PCB232and the emitter module220may be thermally connected to the heat sink212.

FIG.3is a top view of an example emitter module300(e.g., the emitter module220of the lighting device200) that is configured to be used within a lighting device (e.g., such as lighting device100shown inFIG.1or lighting device200shown inFIG.2). The emitter module300may include an array of emitters310(e.g., emission LEDs) and detectors312(e.g., detection LEDs) mounted on a substrate314and encapsulated by a primary optics structure, such as a dome316. For example, the emitter module300may include an array of sixteen emitters310and four detectors312. The emitters310, the detectors312, the substrate314, and the dome316may form an optical system. The emitters310may be arranged in a square array as close as possible together in the center of the dome316, so as to approximate a centrally located point source. The emitter module300may include multiple “chains” of emitters310(e.g., series-coupled emitters). The emitters310of each chain may be coupled in series and may conduct the same drive current. Each chain may include emitters310that produce illumination at a different peak emission wavelength (e.g., emit light of the same color). The emitters310of different chains may emit light of different colors. For example, the emitter module300may include four differently-colored chains of emitters310(e.g., red, green, blue, and white or yellow). The array of emitters310may include a chain of four red emitters, a chain of four green emitters, a chain of four blue emitters, and a chain of four white or yellow emitters. The individual emitters310in each chain may be scattered about the array, and arranged so that no color appears twice in any row, column, or diagonal, to improve color mixing within the emitter module300.

The detectors312may be placed close to each edge of the array of emitters310and/or and in the middle of the array of emitters310and may be connected in parallel to a receiver of the lighting device. Similar to the emitters310, the detectors312may be LEDs that can be used to emit or receive optical or electrical signals. When the detectors312are coupled to receive optical signals and emit electrical signals, the detectors312may produce current indicative of incident light from, for example, an emitter, a plurality of emitters, or a chain of emitters. The detectors312may be any device that produces current indicative of incident light, such as a silicon photodiode or an LED. For example, the detectors312may each be an LED having a peak emission wavelength in the range of approximately 550 nm to 700 nm, such that the detectors312may not produce photocurrent in response to infrared light (e.g., to reduce interference from ambient light).

The substrate314of the emitter module310may be a ceramic substrate formed from an aluminum nitride or an aluminum oxide material or some other reflective material, and may function to improve output efficiency of the emitter module300by reflecting light out of the emitter module300through the dome316. The dome316may include an optically transmissive material, such as silicon or the like, and may be formed through an over-molding process, for example. A surface of the dome316may be lightly textured to increase light scattering and promote color mixing, as well as to reflect a small amount of the emitted light back toward the detectors312mounted on the substrate314(e.g., about 5%). The size of the dome316(e.g., a diameter of the dome in a plane of the emitters310) may be generally dependent on the size of the array of emitters310. The diameter of the dome316may be substantially larger (e.g., about 1.5 to 4 times larger) than the diameter of the array of emitters310to prevent occurrences of total internal reflection.

Another form factor of a lighting device may be a linear form factor. A linear lighting device may include a number of the emitter modules (e.g., such as the emitter module220,300) spaced apart and arranged in a linear manner (e.g., in a line). Each emitter module in the linear lighting device may include a plurality of emitters and at least one dedicated detector, all of which may mounted onto a common substrate and encapsulated within a primary optics structure. The primary optics structure may be formed from a variety of different materials and may have substantially any shape and/or dimensions necessary to mix the light emitted by the emitters in any desirable manner.

FIG.4is a simplified block diagram of an example electrical device, such as a lighting device400(e.g., the lighting device100shown inFIG.1and/or the lighting device200shown inFIG.2). The lighting device400may include one or more emitter modules410(e.g., such as the emitter module220shown inFIG.2or the emitter module300shown inFIG.3). For example, if the lighting device400is a PAR lamp (e.g., as shown inFIGS.1and2), the lighting device400may include a single emitter module410. The emitter module410may include one or more emitters411,412,413,414. Each of the emitters411,412,413,414is shown inFIG.4as a single LED, but may each include a plurality of LEDs connected in series (e.g., a chain of LEDs), a plurality of LEDs connected in parallel, or a suitable combination thereof, depending on the particular lighting system. In addition, each of the emitters411,412,413,414may include one or more organic light-emitting diodes (OLEDs). For example, the first emitter411may represent a chain of red LEDs, the second emitter412may represent a chain of blue LEDs, the third emitter413may represent a chain of green LEDs, and the fourth emitter414may represent a chain of white or amber LEDs. The emitters411,412,413,414may be controlled to adjust an intensity (e.g., lighting intensity or brightness) and/or a color (e.g., a color temperature) of a cumulative light output of the lighting device400. The emitter module410may also include one or more detectors416,418(e.g., photodiodes, such as a red LED and a green LED) that may produce respective photodiode currents IPD1, IPD2(e.g., detector signals) in response to incident light.

The lighting device400may include a power converter circuit420, which may receive a source voltage, such as an AC mains line voltage VAC, via a hot connection H and a neutral connection N, and generate a DC bus voltage VBUS(e.g., approximately 15-20V) across a bus capacitor CBUS. The power converter circuit420may include, for example, a boost converter, a buck converter, a buck-boost converter, a flyback converter, a single-ended primary-inductance converter (SEPIC), a auk converter, or any other suitable power converter circuit for generating an appropriate bus voltage. The power converter circuit420may provide electrical isolation between the AC power source and the emitters411,412,413,414, and may operate as a power factor correction (PFC) circuit to adjust the power factor of the lighting device400towards a power factor of one.

The lighting device400may include one or more emitter module interface circuits430(e.g., one emitter module interface circuit per emitter module410in the lighting device400). The emitter module interface circuit430may include an LED drive circuit432for controlling (e.g., individually controlling) the power delivered to and an intensity (e.g., lighting intensity and/or luminous flux) of the light emitted of each of the emitters411,412,413,414of the respective emitter module410. The LED drive circuit432may receive the bus voltage VBUSand may adjust magnitudes of respective LED drive currents ILED1, ILED2, ILED3, ILED4conducted through the emitters411,412,413,414. The LED drive circuit432may include one or more regulation circuits (e.g., four regulation circuits), such as switching regulators (e.g., buck converters) for controlling the magnitudes of the respective LED drive currents ILED1-ILED4. An example of the LED drive circuit432is described in greater detail in U.S. Pat. No. 9,485,813, issued Nov. 1, 2016, entitled ILLUMINATION DEVICE AND METHOD FOR AVOIDING AN OVER-POWER OR OVER-CURRENT CONDITION IN A POWER CONVERTER, the entire disclosure of which is hereby incorporated by reference.

The emitter module interface circuit430may also include a receiver circuit434that may be electrically coupled to the detectors416,418of the emitter module410for generating respective optical feedback signals VFB1, VFB2in response to the photodiode currents IPD1, IPD2. The receiver circuit434may include one or more trans-impedance amplifiers (e.g., two trans-impedance amplifiers) for converting the respective photodiode currents IPD1, IPD2into the optical feedback signals VFB1, VFB2. For example, the optical feedback signals VFB1, VFB2may have DC magnitudes that indicate the magnitudes of the respective photodiode currents IPD1, IPD2.

The emitter module interface circuit430may also include an emitter module control circuit436for controlling the LED drive circuit432to control the intensities of the emitters411,412,413,414of the emitter module410. The emitter module control circuit436may include, for example, a microprocessor, a microcontroller, a programmable logic device (PLD), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or any other suitable processing device or controller. The emitter module control circuit436may generate one or more drive signals VDR1, VDR2, VDR3, VDR4for controlling the respective regulation circuits in the LED drive circuit432. The emitter module control circuit436may receive the optical feedback signals VFB1, VFB2from the receiver circuit434for determining a luminous flux LE of the light emitted by the emitters411,412,413,414.

The emitter module control circuit436may also receive a plurality of emitter forward-voltage feedback signals VFE1, VFE2, VFE3, VFE4from the LED drive circuit432and a plurality of detector forward-voltage feedback signals VFD1, VFD2from the receiver circuit434. The emitter forward-voltage feedback signals VFE1-VFE4may be representative of the magnitudes of the forward voltages of the respective emitters411,412,413,414, which may indicate temperatures TE1, TE2, TE3, TE4of the respective emitters. If each emitters411,412,413,414includes multiple LEDs electrically coupled in series, the emitter forward-voltage feedback signals VFE1-VFE4may be representative of the magnitude of the forward voltage across a single one of the LEDs or the cumulative forward voltage developed across multiple LEDs in the chain (e.g., all of the series-coupled LEDs in the chain). The detector forward-voltage feedback signals VFD1, VFD2may be representative of the magnitudes of the forward voltages of the respective detectors416,418, which may indicate temperatures TD1, TD2of the respective detectors. For example, the detector forward-voltage feedback signals VFD1, VFD2may be equal to the forward voltages VFDof the respective detectors416,418.

The lighting device400may include a lighting device control circuit440that may be electrically coupled to the emitter module control circuit436of each of the one or more emitter module interface circuits430via a communication bus442(e.g., an I2C communication bus). The lighting device control circuit440may be configured to communicate with the emitter module control circuit436via the communication bus443to control the emitters411,412,413,414to control the intensity (e.g., lighting intensity and/or brightness) and/or the color (e.g., the color temperature) of the cumulative light emitted by the lighting device400. The lighting device control circuit440may include, for example, a microprocessor, a microcontroller, a programmable logic device (PLD), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or any other suitable processing device or controller. The lighting device control circuit440may be configured to adjust (e.g., dim) a present intensity LPRES(e.g., a present brightness) of the cumulative light emitted by the lighting device400towards a target intensity LTRGT(e.g., a target brightness), which may range across a dimming range of the lighting device, e.g., between a low-end intensity LLE(e.g., a minimum intensity, such as approximately 0.1%-1.0%) and a high-end intensity LHE(e.g., a maximum intensity, such as approximately 100%). The lighting device control circuit440may be configured to adjust a present color CPRESof the cumulative light emitted by the lighting device400towards a target color CTRGT(e.g., in an XY chromaticity space, where colors may be defined by an x-chromaticity coordinate and a y-chromaticity coordinate). The lighting device control circuit440may be configured to adjust a present color temperature TPRESof the cumulative light emitted by the lighting device400towards a target color temperature TTRGT(e.g., in a Correlated Color Temperature (CCT) chromaticity space, where colors may be defined by a color temperature value). The CCT chromaticity space may range between warm-white color temperature (e.g., approximately 1400 K) and a cool-white color temperature (e.g., approximately 10,000 K). For example, the lighting device control circuit440may be configured to adjust the present color CPRESof the cumulative light emitted by the lighting device400by transmitting an x-chromaticity coordinate and a y-chromaticity coordinate (e.g., in the XY chromaticity space) to the emitter module control circuit436. In addition, the lighting device control circuit440may be configured to adjust the present color CPRESof the cumulative light emitted by the lighting device400by transmitting the target color temperature TTRGT(e.g., in the CCT chromaticity space) to the emitter module control circuit436.

The lighting device400may include a communication circuit444coupled to the lighting device control circuit440. The communication circuit444may include one or more wireless communication circuits, such as, for example, a radio-frequency (RF) transceiver coupled to an antenna for transmitting and/or receiving RF signals. The one or more wireless communication circuits may comprise an RF transmitter for transmitting RF signals, an RF receiver for receiving RF signals, or an infrared (IR) transmitter and/or receiver for transmitting and/or receiving IR signals. For example, the communication circuit444may comprise a first wireless communication circuit capable of communicating on a first wireless communication link (e.g., a wireless network communication link) using a first wireless protocol (e.g., a wireless network communication protocol, such as the CLEAR CONNECT (e.g., CLEAR CONNECT A and/or CLEAR CONNECT X) and/or THREAD protocols), and a second wireless communication circuit capable of communicating on a second wireless communication link (e.g., a short-range wireless communication link) using a second wireless protocol (e.g., a short-range wireless communication protocol, such as the BLUETOOTH and/or BLUETOOTH LOW ENERGY (BLE) protocols). The communication circuit444may be configured to receive RF signals (e.g., wireless control signals) from one or more remote control devices via the wireless network communication link. The wireless control signals may include messages that indicate a destination color (e.g., in the XY chromaticity space, the CCT chromaticity space, a uv color space, and/or the like). The communication circuit444may be configured to receive RF signals (e.g., wireless configuration signals) from a computing device (e.g., a computer, a cloud server, a mobile device, such as a smart phone and/or a tablet, etc.) via the short-range wireless communication link (e.g., for configuring the operation of the lighting device400). In addition, the communication circuit444may be coupled to the hot connection H and the neutral connection N of the lighting device400for transmitting a control signal via the electrical wiring using, for example, a power-line carrier (PLC) communication technique.

The lighting device control circuit440may be configured to determine the target intensity LTRGT, the target color CTRGT, and/or the target color temperature TTRGTfor the lighting device400in response to messages (e.g., digital messages) received via the communication circuit434. When the lighting device control circuit440receives a target color temperature TTRGT, the lighting device control circuit440may be configured to convert the target color temperature TTRGTfrom the CCT chromaticity space to a target color CTRGTin the XY chromaticity space (e.g., as defined by an x-chromaticity coordinate and a y-chromaticity coordinate). The lighting device control circuit440may transmit the x-chromaticity coordinate and a y-chromaticity coordinate defining the target color CTRGTto the emitter module control circuit436.

The lighting device400may include a memory446configured to store operational characteristics of the lighting device400(e.g., the target intensity LTRGT, the target color temperature TTRGT, the low-end intensity LLE, the high-end intensity LHE, etc.). The memory may be implemented as an external integrated circuit (IC) or as an internal circuit of the lighting device control circuit440. The lighting device400may include a power supply448that may receive the bus voltage VBUSand generate a supply voltage Vcc for powering the lighting device control circuit440and other low-voltage circuitry of the lighting device400.

When the lighting device400is on, the lighting device control circuit440may be configured to control the emitter module(s)410to emit light substantially all of the time. The lighting device control circuit440may be configured to control the emitter module(s)410to disrupt the normal emission of light to measure one or more operational characteristics of the emitter modules during periodic measurement intervals. For example, during the measurement intervals, the emitter module control circuit436may be configured to individually turn on each of the different-colored emitters411,412,413,414of the emitter module(s)410(e.g., while turning of the other emitters) and measure the luminous flux LE of the light emitted by that emitter using one of the two detectors416,418. For example, the emitter module control circuit436may turn on the first emitter411of the emitter module410(e.g., at the same time as turning off the other emitters412,413,414) and determine the luminous flux LE of the light emitted by the first emitter411in response to the first optical feedback signal VFB1generated from the first detector416. In addition, the emitter module control circuit436may be configured to drive the emitters411,412,413,414and the detectors416,418to generate the emitter forward-voltage feedback signals VFE1-VFE4and the detector forward-voltage feedback signals VFD1, VFD2during the measurement intervals.

Methods of measuring the operational characteristics of emitter modules in a lighting device are described in greater detail in U.S. Pat. No. 9,332,598, issued May 3, 2016, entitled INTERFERENCE-RESISTANT COMPENSATION FOR ILLUMINATION DEVICES HAVING MULTIPLE EMITTER MODULES; U.S. Pat. No. 9,392,660, issued Jul. 12, 2016, entitled LED ILLUMINATION DEVICE AND CALIBRATION METHOD FOR ACCURATELY CHARACTERIZING THE EMISSION LEDS AND PHOTODETECTOR(S) INCLUDED WITHIN THE LED ILLUMINATION DEVICE; and U.S. Pat. No. 9,392,663, issued Jul. 12, 2016, entitled ILLUMINATION DEVICE AND METHOD FOR CONTROLLING AN ILLUMINATION DEVICE OVER CHANGES IN DRIVE CURRENT AND TEMPERATURE, the entire disclosures of which are hereby incorporated by reference.

Calibration values for the various operational characteristics of the lighting device400may be stored in the memory446as part of a calibration procedure performed during manufacturing of the lighting device400. Calibration values may be stored for each of the emitters411,412,413,414and/or the detectors416,418of each of the emitter modules410. For example, calibration values may be stored for measured values of luminous flux (e.g., in lumens), x-chromaticity coordinate, y-chromaticity coordinate, emitter forward voltage, photodiode current, and detector forward voltage. For example, the luminous flux, x-chromaticity coordinate, and y-chromaticity coordinate measurements may be obtained from the emitters411,412,413,414using an external calibration tool, such as a spectrophotometer. The values for the emitter forward voltages, photodiode currents, and detector forward voltages may be measured internally to the lighting device400. The calibration values for each of the emitters411,412,413,414and/or the detectors416,418may be measured at a plurality of different drive currents, e.g., at 100%, 30%, and 10% of a maximum drive current for each respective emitter.

In addition, the calibration values for each of the emitters411,412,413,414and/or the detectors416,418may be measured at a plurality of different operating temperatures. The lighting device400may be operated in an environment that is controlled to multiple calibration temperatures and values of the operational characteristics may be measured and stored. For example, the lighting device400may be operated at a cold calibration temperature, such as room temperature (e.g., approximately 25° C.), and a hot calibration temperature (e.g., approximately 85° C.). At each temperature, the calibration values for each of the emitters411,412,413,414and/or the detectors416,418may be measured at each of the plurality of drive currents and stored in the memory446.

After installation, the lighting device control circuit440of the lighting device400may use the calibration values stored in the memory446to maintain a constant light output from the emitter module(s)410. The lighting device control circuit440may determine target values for the luminous flux LE to be emitted from the emitters411,412,413,414to achieve the target intensity LTRGTand/or the target color temperature TTRGTfor the lighting device400. The lighting device control circuit440may determine the magnitudes for the respective drive currents ILED1-ILED4for the emitters411,412,413,414based on the determined target values for the luminous flux LE to be emitted from the emitters411,412,413,414. When the age of the lighting device400is zero, the magnitudes of the respective drive currents ILED1-ILED4for the emitters411,412,413,414may be controlled to initial magnitudes LED-INITIAL.

The light output of the emitter modules410may decrease as the emitters411,412,413,414age. The lighting device control circuit440may be configured to increase the magnitudes of the drive current IDR for the emitters411,412,413,414to adjusted magnitudes LED-ADJUSTED to achieve the determined target values for the luminous flux LE of the target intensity LTRGTand/or the target color temperature TTRGT. Methods of adjusting the drive currents of emitters to achieve a constant light output as the emitters age are described in greater detail in U.S. Patent Application Publication No. 2015/0382422, published Dec. 31, 2015, entitled ILLUMINATION DEVICE AND AGE COMPENSATION METHOD, the entire disclosure of which is hereby incorporated by reference.

FIG.5Adepicts an International Commission on Illumination (CIE) 1931 color space chart500depicting a color space505and a black body curve510. The color space505may represent a two-dimensional space (e.g., an XY chromaticity space) where colors may be indicated by an x-chromaticity coordinate and a y-chromaticity coordinate. The black body curve510may represent a one-dimensional space (e.g., a CCT chromaticity space) where colors may be indicated by a color temperature value (e.g., from 1400 K to 10,000 K). The chart500depicts example color adjustments between colors on the black body curve510and between colors on and off the black body curve510. A color within a predetermined threshold value of the black body curve510may be considered to be on the black body curve510. A color farther from the black body curve510than the predetermined threshold value may be considered to be off the black body curve510. The predetermined threshold may be determined such that it is within one MacAdam ellipse of the black body curve510. The predetermined threshold value may be a delta UV (Duv) value (e.g., a delta UV value of 0.05). The predetermined threshold value may be a function of illuminance. For example, as an illuminance value (e.g., of a lighting device) decreases, the predetermined threshold value may increase.

A lighting device (e.g., such as the lighting device100shown inFIG.1, the lighting device200shown inFIG.2, or the lighting device400shown inFIG.4) may be controlled to emit light having a first color520, which may be referred to as an initial color CINIT. The lighting device may receive a message indicating a second color530, which may be referred to as a destination color CDEST. The lighting device may determine whether the first color520and/or the second color530are on the black body curve510. For example, as shown inFIG.5A, the first color520may not be on the black body curve510and the second color530may be on the black body curve510. The lighting device may need to convert the second color530from the CCT chromaticity space to the XY chromaticity space (e.g., as described herein). When the first color520and/or the second color530are not be on the black body curve510, the lighting device may determine to adjust (e.g., linearly adjust in the XY chromaticity space) the light emitted from the lighting device from the first color520to the second color530(e.g., from the first color520to the black body curve510). For example, the light emitted by the lighting device may be adjusted (e.g., faded) along a first path525from the first color520to the second color530. The first path525may be a straight line between the first color520and the second color530.

In addition, the lighting device may be controlled to emit light having a third color540. In this example, the third color540may be referred to as an initial color CINIT. The lighting device may receive the message indicating the second color530, which may be referred to as a destination color CDEST. The lighting device may determine that the third color540and the second color530are on the black body curve510. The lighting device may need to convert the second color530and/or the third color540from the CCT chromaticity space to the XY chromaticity space (e.g., as described herein). When the initial color CINIT(e.g., the third color540) and the destination color CDEST(e.g., the second color530) are determined to be on the black body curve510, the lighting device may determine to adjust the light emitted from the lighting device from the third color540to the second color530along the black body curve510(e.g., in the CCT chromaticity space). For example, the light emitted by the lighting device may be adjusted along a second path545that extends from the third color540to the second color530along the black body curve510. The second path545may be configured to remain within the predetermined threshold of the black body curve510.

When the initial color CINITand the destination color CDESTare both on the black body curve510, the lighting device may be configured to adjust (e.g., fade) the light emitted from the lighting device along the black body curve510(e.g., in the CCT chromaticity space) according to a relationship between color (e.g., color temperature) and time. For example, the lighting device may be configured to adjust the color temperature to which the lighting device is controlling the light emitted from the lighting device along the black body curve510according to a linear relationship between color temperature and time.FIG.5Bdepicts an example linear relationship550between color temperature and time for adjusting a color temperature of light emitted by a lighting device based on the black body curve510. As shown inFIG.5B, the color temperature may be adjusted from a warm-white color temperature CCTWW(e.g., approximately 1400 K) at one end of the linear relationship550to a cool-white color temperature CCTCW(e.g., approximately 10,000 K) at the other end. For example, the lighting device may be configured to update the color temperature of the light emitted by the lighting device on a periodic basis at an update period (e.g., every half-cycle of the AC power source to which the lighting device is coupled). According to the linear relationship550between color temperature and time, the lighting device may be configured to adjust the color temperature by a constant amount (e.g., steps) per update period. The constant amount of color temperature adjustment per update period may be associated with a particular command to fade the light emitted by the lighting device from the initial color CINITto the destination color CDEST. For example, the lighting device may determine the amount of color adjustment per update period based on the difference between the initial color CINITand the destination color CDESTand/or the update period. For example, if the lighting device is initially emitting light at a color temperature of 3000K and receives a command to fade the light emitted to a color temperature of 6000K over a fade period of one minute, the lighting device may linearly adjust the color temperature with respect to time from 3000K at time t1(e.g., zero seconds) to 6000K at time t2(e.g., sixty seconds) as shown inFIG.5B.

When adjusting the color temperature as defined by the linear relationship550between color temperature and time, the lighting device may convert the color temperature from the CCT chromaticity space to the XY chromaticity space during each update period before controlling the light emitted from the lighting device. As shown inFIG.5A, the color temperatures on the black body curve510near the cool-white color temperature CCTCW(e.g., 10,000 K) are closer together in the XY chromaticity space than color temperatures near the warm-white color temperature CCTWW(e.g., 1400K). In other words, the constant amounts of adjustment of the color temperature in the CCT chromaticity space per update period when using the linear relationship550may result in varying amounts of adjustment of the color in the XY chromaticity space (e.g., larger steps in the color in the XY chromaticity space near the warm-white color temperatures and smaller steps in the color in the XY chromaticity space near the cool-white color temperatures). As the lighting device is fading the color temperature by the constant amounts in the CCT chromaticity space, the color of the light emitted by the lighting device (e.g., as perceived by the human eye) may transition more quickly through the warm-white color temperatures than the cool-white color temperatures (e.g., a perceived change in the color temperature may be non-linear with respect to time).

The lighting device may be configured to adjust (e.g., fade) the light emitted from the lighting device along the black body curve510according to a non-linear relationship between color (e.g., color temperature) and time, for example, to cause the perceived change in the color temperature to be approximately linear with respect to time.FIG.5Cdepicts an example non-linear relationship560between color temperature and time for adjusting a color temperature of light emitted by a lighting device based on the black body curve510. For example, the lighting device may be configured to adjust the light emitted from the lighting device along the black body curve510according to the non-linear relationship560between color temperature and time that may provide for higher resolution near the warm-white color temperatures than near the cool-white color temperatures. Stated differently, the non-linear relationship560may be configured to avoid abrupt changes in perceived color that may be perceived using the linear relationship550during the fade from an initial color temperature at an initial time to a target color temperature at a target time. The non-linear relationship560may include an exponential relationship defined by an exponential curve, a square law relationship defined by a square law curve, and/or another non-linear relationship. As shown inFIG.5C, the color temperature may be adjusted from the warm-white color temperature CCTWW(e.g., approximately 1500 K) at one end of the non-linear relationship560to the cool-white color temperature CCTCW(e.g., approximately 10,000 K) at the other end. According to the non-linear relationship560between color temperature and time, the lighting device may be configured to adjust the color temperature by a variable amount per update period. For example, the lighting device may determine the amount of color adjustment for each update period based on the non-linear relationship560and/or the update period. When using the non-linear relationship550between color temperature and time to fade the light emitted by the lighting device from an initial color CINITto a destination color CHEST, the lighting device may be configured to provide smaller changes in color temperature per update period near the warm-white color temperatures than near the cool-white color temperatures. For example, if the lighting device is initially at a color temperature of 3000K and receives a command to fade to a color temperature of 6000K over a fade period of one minute, the lighting device may adjust the color temperature according to the non-linear relationship560with respect to time from 3000K at time t3(e.g., zero seconds) to 6000K at time t4(e.g., sixty seconds) as shown inFIG.5C. The varying amounts of adjustment of the color temperature in the CCT chromaticity space per update period when using the non-linear relationship560may be sized such that the resulting amounts of adjustment of the color in the XY chromaticity space are approximately constant (e.g., the perceived change in the color temperature may be approximately linear with respect to time).

FIG.6is a flowchart depicting an example control procedure600for adjusting a color of light emitted by a lighting device based on a black body curve (e.g., the black body curve510shown inFIG.5A). The control procedure600may be executed as part of a control procedure (e.g., a color control procedure). The control procedure600may be implemented by one or more devices. For example, the control procedure600may be executed by a control circuit (e.g., the lighting device control circuit440shown inFIG.4) of a lighting device (e.g., such as the lighting device100shown inFIG.1, the lighting device200shown inFIG.2, or the lighting device400shown inFIG.4) to adjust a color of light emitted by the lighting device. For example, the control procedure600may be executed at602by the lighting device that is emitting light having a first color (e.g., an initial color CINIT).

The control procedure600may be executed at602in response to receipt of a message (e.g., a digital message) indicating a second color (e.g., a destination color CHEST) that is different than the first color. The second color may be indicated in (e.g., reference a value in) an XY chromaticity space, a Correlated Color Temperature (CCT) chromaticity space, a UVW color space, a RGB color space, or another color space. When the second color is indicated in the XY chromaticity space, the message may include an x-chromaticity coordinate and a y-chromaticity coordinate that indicates the second color. When the second color is indicated in the CCT chromaticity space, the message may include a CCT value of the second color. When the second color is indicated in the UVW color space, the message may include u-chromaticity, a v-chromaticity, and a lightness index (e.g., w). When the second color is indicated in the CCT chromaticity space, the message may include a CCT value of the second color. When the second color is indicated in the RGB color space, the message may include a red x-chromaticity coordinate, a red y-chromaticity coordinate, a green x-chromaticity coordinate, a green y-chromaticity coordinate, a blue x-chromaticity coordinate, and a blue y-chromaticity coordinate that indicate the second color. The message may include a fade request. The fade request may indicate fade information. The fade information may include a fade rate, a fade duration, an adjustment interval, and/or an adjustment magnitude (e.g., a step, increment/decrement change in color per adjustment interval).

At604, the lighting device may determine whether the first color and/or the second color are on the black body curve. The lighting device may determine that a color is on the black body curve when that color is within a threshold value from the black body curve (e.g., within one MacAdam ellipse of the colors on the black body curve). The threshold value may be a delta UV (Duv) value (e.g., a delta UV value of 0.05). At606, the lighting device may determine to fade in the CCT chromaticity space, when the first color and the second color are on the black body curve. Further, at606, the lighting device may set a present CCT chromaticity value CCTPRESbased on the CCT chromaticity value associated with the initial color CINIT, and may determine a destination CCT chromaticity value CCTDESTbased on the CCT chromaticity value associated with the destination color CHEST.

At610, the lighting device may determine whether to fade in the CCT chromaticity space. If the lighting device determines at610to fade in the CCT chromaticity space, the lighting device may adjust at612the color temperature (e.g., the present CCT chromaticity value CCTPRES) of the light emitted by the lighting device in the CCT chromaticity space. For example, a control circuit of the lighting device may be configured to perform at612a fade (e.g., a linear fade or a non-linear fade) in the CCT chromaticity space. The control circuit may be configured to control the lighting load such that the light emitted by the lighting device is adjusted from the first color to the second color by performing the fade in the CCT chromaticity space (e.g., according to the linear relationship550or the non-linear relationship560between color temperature and time). The color temperature may be adjusted (e.g., iteratively) based on the fade information received in the message. Alternatively, the lighting device may determine the fade information (e.g., to use for the fade) based on one or more factors. The one or more factors may include a time of day, a time associated with the second color, a user configured fade rate, the linear relationship550, the non-linear relationship560, an update period, and/or the like. The lighting device may be pre-configured to use the non-linear relationship560to fade, at612. The lighting device may determine to switch from the non-linear relationships560to the linear relationship550to fade, at612.

In examples, the lighting device may determine whether to use the linear relationship550or the non-linear relationship560to fade in the CCT chromaticity space, for example, based on an estimated perceived change in color. For example, the lighting device may determine whether to use the linear relationship550or the non-linear relationship560such that the color temperature change during the fade is approximately linear with respect to time. In examples, the lighting device may determine an estimated perceived change in color between a current color and a target color using the linear relationship550and non-linear relationship560. The lighting device may choose the linear relationship550or the non-linear relationship560based on which respective estimated perceived change in color between the current color and the target color is closer to a linear perceived change in color. The lighting device may be configured to select the linear relationship550when the perceived changes in color temperature are substantially continuous. For example, the lighting device may be configured to select the non-linear relationship560when using the linear relationship550would result in discontinuous perceived changes in color temperature. In examples, the lighting device may determine whether to use the linear relationship550or the non-linear relationship560to fade in the CCT chromaticity space, for example, based on a delta CCT value (e.g., the difference between a current color temperature and a target color temperature). When the delta CCT is below a threshold delta (e.g., 1000K), the lighting device may determine to use the linear relationship550to fade. For example, when the delta CCT is below the threshold delta, fading using the linear relationship550may appear the same to a user (e.g., have the same perceived change in color) as fading using the non-linear relationship560. When the delta CCT is greater than or equal to the threshold delta, the lighting device may determine to use the non-linear relationship560to fade.

When fading in the CCT chromaticity space along the black body curve, the lighting device may determine a plurality of CCT chromaticity values along the black body curve between the first color temperature and the second color temperature. The plurality of CCT chromaticity values may be associated with the fade (e.g., the fade information). An number of CCT chromaticity values (e.g., steps or ticks) during the fade may be determined based on one or more factors, for example, such as a fade duration, a difference between the first color temperature and the second color temperature, a relationship between color temperature and time (e.g., linear or non-linear) and/or the like. For example, the lighting device may adjust (e.g., iteratively) the present CCT chromaticity value CCTPRESof the plurality of CCT chromaticity values to a next CCT chromaticity value of the plurality of CCT chromaticity values along the black body curve. The lighting device may repeat the loop610,612,614,618, and620for the remaining CCT chromaticity values until the second color (e.g., last CCT chromaticity value of the plurality of CCT chromaticity values) is reached. The last CCT chromaticity value of the plurality of CCT chromaticity values may be the CCT chromaticity value associated with the second color (e.g., the destination color CHEST).

At612, the lighting device may adjust the present CCT chromaticity value CCTPRESbased on the fade information. The first time the lighting device enters612, the present CCT chromaticity value CCTPRESis equal to the CCT chromaticity value associated with the initial color CINIT. When determining how to adjust the present CCT chromaticity value CCTPRESbased on the fade information, the lighting device may determine the fade duration (e.g., 3 seconds), the adjustment magnitude, a fade rate, and/or an adjustment interval. The fade duration may define an allotted time to fade from the initial color CINITto the destination color CDEST. The adjustment interval may be how often (e.g., an amount of time or period) the lighting device periodically adjusts the lighting load across the fade duration. In some examples, adjustment interval may be set to equal the length of one line cycle of the AC mains line voltage, so 16.67 ms when operating in a 60 Hz system or every 20 ms when operating in a 50 Hz system. The adjustment magnitude may define a size of a step change (e.g., ACCT) for each adjustment interval. The adjustment magnitude may be determined based on CINIT, CDEST, the fade duration, and/or the adjustment interval. The fade rate may be a measure of how quickly each color adjustment is performed (e.g., adjustment magnitude divided by adjustment interval). At612, the lighting device may adjust the present CCT chromaticity value CCTPRESby the adjustment magnitude along the black body curve that is based on the fade duration and/or the adjustment interval. Taking an example where the fade duration is 3 seconds and the adjustment interval is 16.67 ms, at612the lighting device may adjust the present CCT chromaticity value CCTPRESby a step change that is equal to approximately 1/180thof the path between the present CCT chromaticity value CCTPRESand the destination CCT chromaticity value CCTDEST. Further, in this example, the lighting device may perform the loop610,612,614,618, and620and adjust CCTPRESapproximately 180 times over 3 seconds for the present CCT chromaticity value CCTPRESto be equal to the destination CCT chromaticity value CCTDEST.

At614, the lighting device may convert the adjusted present CCT chromaticity value CCTPRESdetermined at612from the CCT chromaticity space to the XY chromaticity space to determine a present X chromaticity value XPRESand a present Y chromaticity value YPRES. The adjusted present CCT chromaticity value CCTPRESmay be converted to the XY chromaticity space based on one or more (e.g., a set of) equations stored in a memory of the lighting device. The adjusted present CCT chromaticity value CCTPRESmay be converted to the XY chromaticity space based on a look up table stored in the memory of the lighting device. The lighting device may be configured to convert the adjusted present CCT chromaticity value CCTPRESinto the uv chromaticity space to determine a present uv chromaticity value (e.g., a present u chromaticity value UPRESand a present v chromaticity value VPRES), and then be configured to convert the present uv chromaticity value into the present XY chromaticity values.

At618, the lighting device may control the drive circuit such that the light emitted by the lighting device is adjusted from the first color to the second color. For example, the drive circuit may control an LED drive circuit based on the present X chromaticity value XPRESand the present Y chromaticity value YPRESat618. The control circuit may send XPRESand YPRESto an emitter module control circuit (e.g., such as the emitter module control circuit436shown inFIG.4) to appropriately drive each of the LEDs (e.g., different color LEDs) of the lighting device. When the lighting device at620determines that the light emitted by the lighting devices is not at the second color (e.g., the present CCT chromaticity value CCTPRESdoes not equal the destination CCT chromaticity value CCTDEST), the control procedure600may return to610, and the control circuit may perform another iteration of adjusting the present X chromaticity value XPRESand the present Y chromaticity value YPRES. The lighting device may continue iteratively adjusting the present chromaticity values XPRESand the present Y chromaticity value YPRESuntil they are equal to a destination X chromaticity value XDESTand a destination Y chromaticity value YDESTdetermined at608. For example, the lighting device may perform the loop610,612,614,618, and620and adjust the present CCT chromaticity value CCTPRESbased on the adjustment interval and the adjustment magnitude until the present CCT chromaticity value CCTPRESis equal to the destination CCT chromaticity value CCTDEST. Once the present CCT chromaticity value CCTPRESis equal to the destination CCT chromaticity value CCTDEST, the control procedure600may exit.

If the lighting device determines that the first color or the second color are not on the black body curve at604, then at608, the lighting device may determine to fade in a XY chromaticity space. For example, the lighting device may determine to fade in the XY chromaticity space when the first color and/or the second color are not on the black body curve. In some examples at608, the lighting device may set a present X chromaticity coordinate XPRESand a present Y chromaticity coordinate YPRESbased on the X and Y chromaticity coordinates associated with initial color CINIT, respectively. Further, at608, the lighting device may determine the destination X chromaticity coordinate XDESTand the destination Y chromaticity coordinate YDESTbased on the X and Y chromaticity coordinates associated with the destination color CDEST. When the lighting device determines to fade in the XY chromaticity space at610, the lighting device may adjust (e.g., iteratively) at616a present X chromaticity coordinate XPRESand a present Y chromaticity coordinate YPRES, for example, based on the fade duration, the adjustment magnitude, and an adjustment interval. The lighting device may continue iteratively adjusting the present X chromaticity coordinate XPRESand the present Y chromaticity coordinate YPRESuntil they are equal to the destination X chromaticity coordinate XDESTand the destination Y chromaticity coordinate YDESTdetermined at608. For example, the control procedure600may end when the present X chromaticity coordinate XPRESand the present Y chromaticity coordinate YPRESare equal to the destination X chromaticity coordinate XDESTand the destination Y chromaticity coordinate YDEST.

If the lighting device determines at610to not fade in the CCT chromaticity space, the lighting device may adjust the present X chromaticity coordinate XPRESand the present Y chromaticity coordinate YPRESbased on the fade duration and/or the adjustment interval at616. After adjusting the present X chromaticity coordinate XPRESand the present Y chromaticity coordinate YPRESat616, the lighting device may control an LED drive circuit based on the present X chromaticity coordinate XPRESand the present Y chromaticity coordinate YPRES.

The lighting device may include one or more sensors (e.g., such as the detectors312shown inFIG.3). At least one of the one or more sensors may be configured to measure a color of the light emitted by the lighting device. Alternatively, an external sensor may measure the color of the light emitted by the lighting device. The lighting device may receive, from the external sensor and/or a system controller, an indication of the color of the light emitted by the lighting device. At620, the lighting device may be configured to determine whether the light emitted by the lighting device is at the second color (e.g., CDEST). If the light emitted by the lighting device is measured at the second color, the control procedure600may end.

The lighting device may determine that the first color is off the black body curve (e.g., greater than the threshold value from the black body curve) and that the second color is on the black body curve. The lighting device may control, based on the first color being greater than the threshold value from the black body curve and the second color being on the black body curve, the drive circuit such that the light emitted by the lighting device is adjusted (e.g., adjusted linearly) toward the black body curve to a third color that is on the black body curve. The lighting device may then control the drive circuit such that the light emitted by the lighting device is adjusted along the black body curve between the third color and the second color using the control procedure600wherein the third color is the initial color and the second color is the destination color.

In examples, the lighting device may determine that the first color is on the black body curve and the second color is off the black body curve. The lighting device may control the drive circuit such that the light emitted by the lighting device is adjusted along the black body curve between the first color and an intermediate color using the control procedure600wherein the first color is the initial color and the intermediate color is the destination color. The lighting device may then control the drive circuit such that the light emitted by the lighting device is adjusted (e.g., adjusted linearly) away the black body curve to the second color that is off the black body curve.

FIG.7is a chart700of illuminance vs. color temperature depicting example color appearances. The chart700may be preferred color temperature plot, such as a Kruithof curve, that depicts regions color temperatures that are often viewed as comfortable or pleasing to an observer (e.g., the human eye) at particular illuminance levels (e.g., light levels). The chart700may define a first region710where light appears reddish and is unpleasing to the human eye (e.g., the observer). The first region710may be defined by a first curve712. The first curve712may be a CCT red boundary that defines respective threshold color temperatures, for various illuminance values, below which the emitted light appears reddish in color. The chart700may define a second region720where light appears bluish and is unpleasing to the human eye. The second region720may be defined by a second curve722. The second curve722may be a CCT blue boundary that defines respective threshold color temperatures, for various illuminance values, above which the emitted light appears bluish in color. The chart700may define a third region730that is between the first region710and the second region720. The third region730may be defined by the first curve712and the second curve722. The third region730may define color temperatures between the first curve712and the second curve722, for various illuminance values, that the emitted light is pleasing to the human eye.

A lighting device (e.g., such as the lighting device100shown inFIG.1, the lighting device200shown inFIG.2, and/or the lighting device400shown inFIG.4) may be configured to control the color temperature of the light emitted from the lighting device to maintain the color temperature in the pleasing region of a preferred color temperature plot (e.g., the third region730of the Kruithof curve shown inFIG.7). For example, the lighting device may be configured to determine an illuminance level of the space illuminated by the lighting device and compare the determined illuminance level to a CCT red boundary (e.g., the first curve712) and the CCT blue boundary (e.g., the second curve714) to maintain the color temperature of the light emitted from the lighting device within the pleasing region.

The values of the CCT red boundary (e.g., the first curve712) and the CCT blue boundary (e.g., the second curve714) may be configurable. For example, the values of the CCT red boundary and the CCT blue boundary may be configured based on user preferences. A user may be able to use an application running on a computing device (e.g., a mobile device) to configure the values of the CCT red boundary and the CCT blue boundary, and the computing device may transmit the adjusted values of the CCT red boundary and the CCT blue boundary to the lighting device. For example, the user may select from a plurality of options (e.g., different options of color temperature preference plots and/or shapes and values of the CCT red boundary and the CCT blue boundary) displayed by the application running on the computer device. In addition, the user may utilize a wizard executed by the application running on the computer device to configure the values of the CCT red boundary and the CCT blue boundary. The user may configure the values of the CCT red boundary and the CCT blue boundary based on the preference of the user and/or based on the color of the environment (e.g., wall, furniture, etc.) that the lighting device is illuminating. Further, the values of the CCT red boundary and the CCT blue boundary may automatically be updated. For example, the lighting device may automatically configure (e.g., learn) the desired values of the values of the CCT red boundary and the CCT blue boundary in response to detecting changes in the color temperature of the lighting device as manually adjusted by a user (e.g., in response to actuations of buttons of a remote control device that is controlling the lighting device).

In addition, the lighting device may be configured to determine an illuminance level of the space that is illuminated by the lighting device, and control the color temperature of the light emitted from the lighting device based on (e.g., as a function of) the determined illuminance level. For example, the lighting device may be configured to control the color temperature of the light emitted from the lighting device along a CCT-illuminance curve740as shown inFIG.7. The values of the CCT-illuminance curve740may be set equal to the median value between the CCT red boundary and the CCT blue boundary for values of the illuminance that are less than a threshold illuminance (e.g., approximately 500 lumens as shown inFIG.7). The values of the CCT-illuminance curve740may be stored in memory in the lighting device. In addition, the values of the CCT-illuminance curve740may be configured by a user and/or automatically configured by the lighting devices in a similar manner as the values of the CCT red boundary and the CCT blue boundary may be configured as described above.

FIG.8Ais a flowchart depicting an example control procedure800for adjusting a color (e.g., a color temperature) of light emitted by a lighting device based on an illuminance level (e.g., a light level) of ambient light within a space in which the lighting device is installed. The control procedure800may be executed as part of a color control procedure. The control procedure800may be implemented by one or more devices. For example, the control procedure800may be executed by a control circuit of a lighting device (e.g., such as a control circuit of the lighting device100shown inFIG.1, a control circuit of the lighting device200shown inFIG.2, and/or the lighting device control circuit440of the lighting device400shown inFIG.4), a control circuit of a remote control device, and/or a control circuit of a system controller to adjust a color (e.g., a present color temperature CCTPRES) of light emitted by the lighting device. For example, the control circuit may execute the control procedure800periodically at801. In addition, the control circuit may execute the control procedure800at801in response to a change in the illuminance level of the ambient light and/or a change in a target intensity of the lighting device. The control circuit may execute the control procedure800to ensure that the light in a space is pleasing (e.g., within region730of the chart700shown inFIG.7), for example, to a user. The light in the space may be considered pleasing if it does not appear too reddish or bluish.

At802, the control circuit may determine the values of a CCT red boundary (e.g., the first curve712shown inFIG.7) and a CCT blue boundary (e.g., the second curve714shown inFIG.7) on an illuminance vs. CCT chart (e.g., the chart700shown inFIG.7). For example, the values of the CCT red boundary and the CCT blue boundary may be stored in memory on the lighting device and the control circuit may retrieve the values of the CCT red boundary and the CCT blue boundary from memory at802. The values of the CCT red boundary and the CCT blue boundary may be fixed values and/or may be configurable values. For example, a user may configure the values of the CCT red boundary and the CCT blue boundary using a computing device, and the configured values may be transmitted to the lighting device and stored in memory. In addition, the control circuit may automatically configure (e.g., learn) the values of the CCT red boundary and the CCT blue boundary, for example, in response to detecting changes in the color temperature of the lighting device as manually adjusted by a user.

At804, the control circuit may determine an illuminance level EAMBof ambient light proximate to the lighting device. The ambient light may be proximate to the lighting device if it is in the same space (e.g., room) as the lighting device. The lighting device may include one or more sensors (e.g., such as the detectors312shown inFIG.3) configured to measure the illuminance level EAMBof the ambient light. The control circuit may receive an indication of the illuminance level EAMBof the ambient light proximate to the lighting device. The indication of the illuminance level EAMBof the ambient light may be received from the one or more sensors. The control circuit may be configured to determine the illuminance level EAMBof the ambient light in response to the sensors. Alternatively and/or additionally, the indication of the illuminance level EAMBof the ambient light may be received via a wireless communication circuit of the lighting device (e.g., from an external sensor).

At806, the control device may determine whether the present color temperature CCTPRES(e.g., to which the control circuit is controlling the light emitted by the lighting device) is less than a red threshold temperature CCTTH-REDat the determined illuminance level EAMB. The red threshold temperature CCTTH-REDmay represent a value on the CCT red boundary. The CCT red boundary may define respective threshold color temperatures for various illuminance values below which the emitted light appears reddish in color. In addition, the red threshold temperature CCTTH-REDmay be offset from the CCT red boundary (e.g., to provide a buffer between the threshold temperature and the unpleasant area). The unpleasant area may be larger or smaller than the area shown inFIG.7for different users. The buffer may ensure that the red threshold temperature CCTTH-REDremains outside of the unpleasant area for other users (e.g., with larger unpleasant areas). For example, the red threshold temperature CCTTH-REDmay be offset from the CCT red boundary at a specific illuminance value by an offset value. The offset value may be configured such that the red threshold temperature CCTTH-REDremains outside of the unpleasant area for various users and/or remains pleasing for minor changes in the illuminance level EAMBof the ambient light. For example, the red threshold temperature CCTTH-REDmay be determined using a value on the CCT red boundary plus the offset value (e.g., a value greater than the first curve712shown inFIG.7).

If the present color temperature CCTPRESis less than the red threshold temperature CCTTH-REDat the determined illuminance level EAMB, the control circuit may control the lighting load at808to increase the present color temperature CCTPRESof the light emitted by the lighting device to be equal to or greater than the red threshold temperature CCTTH-REDat the determined illuminance level EAMB. For example, the control circuit may at808set the present color temperature CCTPRESto be greater than the red threshold temperature CCTTH-REDat the determined illuminance level EAMBby a first offset amount CCTOFFSET1(e.g., CCTPRES=CCTTH-RED+CCTOFFSET1). The first offset amount CCTOFFSET1may be determined such that there is a buffer between the red threshold temperature CCTTH-RED(e.g., a potentially reddish color) and the present color temperature CCTPRES(e.g., a potentially a pleasing color). For example, the first offset amount CCTOFFSET1may be determined such that the light emitted by the lighting device remains pleasing for minor changes in the illuminance level EAMBof the ambient light. After the control circuit sets the present color temperature CCTPRESto be greater than or equal to the red threshold temperature CCTTH-REDat the determined illuminance level EAMBat808, the control circuit may control a drive circuit (e.g., the LED drive circuit432) at814to control emitters (e.g., the emitters411,412,413,414) to respective intensities to cause the lighting device to emit light at present color temperature CCTPRES(e.g., as determined at808). The control procedure800may then end to816.

If the present color temperature CCTPRESis not less than the red threshold temperature CCTTH-REDat the determined illuminance level EAMB, the control circuit may determine at810whether the present color temperature CCTPRESis greater than a blue threshold temperature CCTTH-BLUEat the determined illuminance level EAMB. The blue threshold temperature CCTTH-BLUEmay represent a value on a CCT blue boundary (e.g., the second curve722shown inFIG.7) on an illuminance vs. CCT chart (e.g., the chart700shown inFIG.7). The CCT blue boundary may define respective threshold temperatures for various illuminance values above which the emitted light appears bluish in color. In addition, the blue threshold temperature CCTTH-BLUEmay be offset from the CCT blue boundary (e.g., to provide a buffer between the threshold temperature and the unpleasant area). The unpleasant area may be larger or smaller than the area shown inFIG.7for different users. The buffer may ensure that the blue threshold temperature CCTTH-BLUEremains outside of the unpleasant area for other users (e.g., with larger unpleasant areas). For example, the blue threshold temperature CCTTH-BLUEmay be offset from the CCT blue boundary at a specific illuminance value by an offset value. The offset value may be configured such that the blue threshold temperature CCTTH-BLUEremains outside of the unpleasant area for various users and/or remains pleasing for minor changes in the illuminance level EAMBof the ambient light. The offset value for the blue threshold temperature CCTTH-BLUEmay be the same as the offset value for the red threshold temperature CCTTH-RED. The blue threshold temperature CCTTH-BLUEmay represent a value on the CCT blue boundary minus an offset value (e.g., a value less than the second curve722shown inFIG.7).

If the present color temperature CCTPRESis greater than the blue threshold temperature CCTTH-BLUEat the determined illuminance level EAMB, the lighting device may control the lighting load at812to decrease the present color temperature CCTPRESof the light emitted by the lighting device to be equal to or less than the blue threshold temperature CCTTH-BLUEat the determined illuminance level EAMB. For example, the control circuit may at812set the present color temperature CCTPRESto be less than the blue threshold temperature CCTTH-BLUEat the determined illuminance level EAMBby a second offset amount CCTOFFSET2(e.g., CCTPRES=CCTTH-BLUE−CCTOFFSET2). The second offset amount CCTOFFSET2may be determined such that there is a buffer between the blue threshold temperature CCTTH-BLUE(e.g., a potentially bluish color) and the present color temperature CCTPRES(e.g., a potentially a pleasing color). For example, the second offset amount CCTOFFSET2may be determined such that the light emitted by the lighting device remains pleasing for minor changes in the illuminance level EAMBof the ambient light. After the control circuit sets the present color temperature CCTPRESto be less than or equal to the blue threshold temperature CCTTH-BLUEat the determined illuminance level EAMBat808, the control circuit may control a drive circuit (e.g., the LED drive circuit432) at814to control emitters (e.g., the emitters411,412,413,414) to respective intensities to cause the lighting device to emit light at present color temperature CCTPRES(e.g., as determined at808). The control procedure800may then end to816.

If the present color temperature CCTPRESis determined at810to be less than the blue threshold temperature CCTTH-BLUEat the determined illuminance level EAMB, the control procedure800may end at816. The control circuit may be configured to perform, using the one or more sensors, periodic measurements of the illuminance level of the ambient light proximate to the lighting device. The control circuit may determine that the illuminance level of the ambient light proximate to the lighting device has changed from a first illuminance level to a second illuminance level. The control circuit may repeat the control procedure800for the second illuminance level. For example, the control circuit may determine whether the change from the first illuminance level to the second illuminance level is greater than a predetermined threshold. When the difference between the second illuminance level and the first illuminance level is greater than the predetermined threshold, the lighting device may repeat the control procedure800for the second illuminance level to control the lighting load such that the present color temperature CCTPRESthe light emitted by the lighting device is between the CCT red boundary and the CCT blue boundary at the second illuminance level. Alternatively and/or additionally, the control circuit may receive, via the wireless communication circuit, a message that indicates the change in the illuminance level that is greater than the predetermined threshold.

FIG.8Bis a flowchart depicting an example control procedure850for adjusting a color of light emitted by a lighting device based on an illuminance level (e.g., a light level) of ambient light in which the lighting device is installed. The control procedure850may be executed as part of a color control procedure. The control procedure850may be implemented by one or more devices. For example, the control procedure850may be executed by a control circuit of a lighting device (e.g., such as a control circuit of the lighting device100shown inFIG.1, a control circuit of the lighting device200shown inFIG.2, and/or the lighting device control circuit440of the lighting device400shown inFIG.4), a control circuit of a remote control device, and/or a control circuit of a system controller to adjust a color (e.g., a present color temperature CCTPRES) of light emitted by the lighting device. For example, the control circuit may execute the control procedure850periodically at851. In addition, the control circuit may execute the control procedure800at851in response to a change in the illuminance level of the ambient light and/or a change in a target intensity of the lighting device. The control circuit may execute the control procedure800to ensure that the light in a space is pleasing (e.g., within region730of the chart700shown inFIG.7). The light in the space may be considered pleasing if it does not appear too reddish or bluish.

At852, the control circuit may determine the values of a CCT-illuminance curve (e.g., the CCT-illuminance curve740shown inFIG.7). For example, the values of the CCT-illuminance curve may be stored in memory on the lighting device and the control circuit may retrieve the values of the CCT-illuminance curve from memory at852. The values of the CCT-illuminance curve may be fixed values and/or may be configurable values. For example, a user may configure the values of the CCT-illuminance curve using a computing device, and the configured values may be transmitted to the lighting device and stored in memory. In examples, the control circuit may determine (e.g., select) the CCT-illuminance curve from a plurality of CCT-illuminance curves stored in a memory. In addition, the control circuit may automatically configure (e.g., learn) the values of the CCT-illuminance curve, for example, in response to detecting changes in the color temperature of the lighting device as manually adjusted by a user. For example, the lighting device may identify a manual adjustment of the color temperature by a user. The lighting device may be configured to store a plurality of previous user adjustments in memory. The CCT-illuminance curve may be adjusted (e.g., learned) based on the plurality of previous user adjustments.

At854, the control circuit may determine an illuminance level EAMBof ambient light proximate to the lighting device. The ambient light may be proximate to the lighting device if it is in the same space (e.g., room) as the lighting device. The lighting device may include one or more sensors (e.g., such as the detectors312shown inFIG.3) configured to measure the illuminance level EAMBof the ambient light. The control circuit may receive an indication of the illuminance level EAMBof the ambient light proximate to the lighting device. The indication of the illuminance level EAMBof the ambient light may be received from the one or more sensors. The control circuit may be configured to determine the illuminance level EAMBof the ambient light in response to the sensors. Alternatively and/or additionally, the indication of the illuminance level EAMBof the ambient light may be received via a wireless communication circuit of the lighting device (e.g., from an external sensor).

At856, the control circuit may set the present color temperature CCTPRESbased on the CCT-illuminance curve (e.g., as determined at852) and the illuminance level EAMB(e.g., as determined at854) For example, the control circuit may set the present color temperature CCTPRESequal to the value of the CCT-illuminance curve at the illuminance level EAMB. After the control circuit sets the present color temperature CCTPRESat856, the control circuit may control a drive circuit (e.g., the LED drive circuit432) at858to control emitters (e.g., the emitters411,412,413,414) to respective intensities to cause the lighting device to emit light at present color temperature CCTPRES(e.g., as determined at856). The control procedure850may then end to860.

FIG.9is a chart900depicting a plurality of dimming curves. The chart900comprises a linear dimming curve910, a square law dimming curve920, and an exponential dimming curve930. A lighting device (e.g., such as the lighting device100shown inFIG.1, the lighting device200shown inFIG.2, and/or the lighting device400shown inFIG.4) may determine to use one or more of the dimming curves. The dimming curves of the lighting device may each define values of actual intensity (e.g., the present intensity LPRESand/or the target intensity LTRGT) with respect to controlled intensity (e.g., as determined from messages received via the communication circuit434). In examples, the lighting device may use the linear dimming curve910, the square law dimming curve920, and/or the exponential dimming curve930over the full range of intensities. For example, the lighting device may use one of the dimming curves based on an illuminance level (e.g., a light level) of ambient light in which the lighting device is installed. In examples, the lighting device may use a first dimming curve over a first range of illuminance levels of the ambient light and a second dimming curve over a second range of illuminance levels of the ambient light. For example, the lighting device may use the square law curve920over the first range of illuminance levels and the linear dimming curve910or the exponential dimming curve930over the second range of illuminance levels.

FIG.10is a flowchart depicting an example control procedure1000for selecting a dimming curve based on an illuminance level (e.g., a light level) of ambient light in which the lighting device is installed. The method1000may be executed as part of a control procedure (e.g., an intensity control procedure). The control procedure1000may be implemented by one or more devices. For example, the control procedure1000may be executed by a control circuit of a lighting device (e.g., such as a control circuit of the lighting device100shown inFIG.1, a control circuit of the lighting device200shown inFIG.2, or the lighting device control circuit440of the lighting device400shown inFIG.4), a control circuit of a remote control device, and/or a control circuit of a system controller to determine a dimming curve for controlling an intensity of light emitted by the lighting device. The control procedure1000may be used to control an intensity of light emitted by the lighting device by controlling a drive circuit (e.g., the LED drive circuit432) of the lighting device to control emitters (e.g., the emitters411,412,413,414). For example, the control circuit may execute the control procedure1000periodically at1002. In addition, the control circuit may execute the control procedure1000at1002by the lighting device in response to a change in the illuminance level of the ambient light.

The control procedure1000may be executed to use a dimming curve with finer granularity at a low ambient light level. For example, when the ambient light level is high (e.g., when the ambient light level is greater than an illuminance threshold ETH), the control circuit may be configured to use a normal dimming curve (e.g., the linear dimming curve910and/or the square law dimming curve920shown inFIG.9), which may provide a substantially constant amount of change of the actual intensity of the lighting device per step change in the controlled intensity. When the ambient light level is low, the control circuit may be configured to use a low-level dimming curve (e.g., the exponential dimming curve930), for example, to provide a higher granularity in the adjustment of the actual intensity of the lighting device per step change in the controlled intensity near the low-end intensity LLE. The control circuit may use hysteresis when determining which of the dimming curves to use. For example, when the lighting device is using the normal dimming curve, the control circuit may start to use (e.g., switch to) the low-level dimming curve when the ambient light level is less than a first illuminance threshold ETH1. In addition, when the lighting device is using the low-level dimming curve, the control circuit may start to use (e.g., switch to) the normal dimming curve when the ambient light level is greater than a second illuminance threshold ETH2(e.g., which may be greater than the first illuminance threshold ETH1).

At1004, the control may determine an illuminance level EAMBof ambient light proximate to the lighting device. The ambient light may be proximate to the lighting device if it is in the same space (e.g., room) as the lighting device. The lighting device may include one or more sensors (e.g., such as the detectors312shown inFIG.3) configured to measure the illuminance level EAMBof the ambient light. The control circuit may receive an indication of the illuminance level EAMBof the ambient light proximate to the lighting device. The indication of the illuminance level EAMBof the ambient light may be received from the one or more sensors. The control circuit may be configured to determine the illuminance level EAMBof the ambient light in response to the sensors. Alternatively and/or additionally, the indication of the illuminance level EAMBof the ambient light may be received via a wireless communication circuit of the lighting device (e.g., from an external sensor).

When the lighting device is using a normal dimming curve (e.g., the square law dimming curve) at1006, the lighting device may compare the determined illuminance level EAMBof the ambient light to the first illuminance threshold ETH1at1008. The first predetermined illuminance threshold ETH1may correspond to a low illuminance level of the ambient light. For example, the lighting device may determine whether the illuminance level EAMBof the ambient light is less than or equal to the first illuminance threshold ETH1. If the illuminance level of the ambient light is less than the first illuminance threshold ETH1, the control circuit at1008may determine to control a lighting load of the lighting device according to a low-level dimming curve, such as the exponential dimming curve (e.g., the exponential dimming curve930shown inFIG.9) at1010. The exponential law dimming curve may enable a finer granularity of dimming below the low illuminance level of ambient light than a normal dimming curve, such as the square law dimming curve. For example, the control circuit may at1010control the lighting device to adjust (e.g., fade) the intensity from a first intensity at the determined illuminance level EAMBof the ambient light (e.g., according to the normal dimming curve) to a second intensity at the determined illuminance level EAMBof the ambient light (e.g., according to the low-light dimming curve across a period of time (e.g., 1-60 minutes), such that the change in the intensity is not noticed by a user.

When the lighting device is not using a normal dimming curve at1006(e.g., the lighting device is using the exponential dimming curve), the lighting device may compare the determined illuminance level EAMBof the ambient light to the second illuminance threshold ETH2at1012. The second predetermined illuminance threshold ETH2may correspond to a high illuminance level of the ambient light. If the illuminance level EAMBof the ambient light is greater than or equal to the second illuminance threshold ETH2, the control circuit at1014may determine to control the lighting load according to a normal law dimming curve, such as the square law dimming curve (e.g., such as the square law dimming curve920shown inFIG.9) at1014. For example, the control circuit may at1013control the lighting device to adjust (e.g., fade) the intensity from a first intensity at the determined illuminance level EAMBof the ambient light (e.g., according to the low-light dimming curve) to a second intensity at the determined illuminance level EAMBof the ambient light (e.g., according to the normal dimming curve) across a period of time (e.g., 1-60 minutes), such that the change in the intensity is not noticed by a user.

The control circuit may be configured to control the lighting load based on a step size of the intensity and the illuminance level EAMBof the ambient light proximate to the lighting device. For example, the intensity of the lighting load may be adjusted when a user presses a button. Each button press may correspond to a step change in intensity. The control circuit may be configured to control the lighting load according to the normal law dimming curve, at1014, when the illuminance level of the ambient light proximate to the lighting device is below a third illuminance threshold ETH3. The third illuminance threshold ETH3may be a step change threshold. The control circuit may be configured to control the lighting load according to the exponential law dimming curve, at1010, when the illuminance level of the ambient light proximate to the lighting device is greater than or equal to the third illuminance threshold Eau. As described herein, the exponential law dimming curve may enable a finer granularity of dimming below the third illuminance threshold ETH3of ambient light than a normal dimming curve, such as the square law dimming curve. For example, controlling the lighting load using the normal dimming curve at low ambient light levels may enable the control circuit to adjust from a current intensity to a target intensity with fewer button presses when compared to the exponential law dimming curve. Stated differently, the normal dimming curve may enable larger intensity step sizes for each button press when compared to the exponential law dimming curve.

It should be appreciated that althoughFIGS.1and2depict example lighting devices100,200; the disclosure herein is not limited to these example lighting devices100,200. Instead, the lighting device(s) referred to herein, may be any lighting device such as a linear lighting device, a strip light, a bulb, a downlight, a tube, and/or the like.