Patent Description:
Light-emitting diodes (LEDs) are commonly used in various lighting operations. The color appearance of an object is determined, in part, by the spectral power density (SPD) of light illuminating the object. For humans viewing an object, the SPD is the relative intensity for various wavelengths within the visible light spectrum. However, other factors can also affect color appearance. Also, both a correlated color temperature (CCT) of the LED, and a distance of the temperature of the LED on the CCT from a black-body line (BBL, also known as a black-body locus or a Planckian locus), can affect a human's perception of an object. In particular there is a large market demand for LED lighting solutions, such as in retail and hospitality lighting applications, where it is desirable to control both a color temperature and a brightness level of the LEDs.

There are presently two major technologies for color tuning (e.g., white tuning) of LEDs. A first technology, for example as described in <CIT>, is based on white LEDs of two or more CCTs. The second technology is based on a combination of Red/Green/Blue/Amber colors. The first technology simply does not have a capability to tune LEDs in the Duv direction. In the second technology, the color tuning capability is seldom offered as an available function. In those cases, the user is instead usually offered a color wheel based on either Red-Green-Blue (RGB) or Hue-Saturation-Lightness (HSL) models.

However, the RGB and HSL models were not designed for general illumination. Both the RGB and HSL model are more appropriate for graphics or photographic applications.

<CIT> describes a control apparatus to color tune a multi-colored LED array according to the state of the art.

The information described in this section is provided to offer the skilled artisan a context for the following disclosed subject matter and should not be considered as admitted prior art.

The invention is set out in the appended claims, particularly the invention is defined by a control apparatus according to claim <NUM> and by a method according to claim <NUM>.

The disclosed subject matter will now be described in detail with reference to a few general and specific embodiments as illustrated in various ones of the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the disclosed subject matter. It will be apparent, however, to one skilled in the art, that the disclosed subject matter may be practiced without some or all of these specific details. In other instances, well-known process steps or structures have not been described in detail so as not to obscure the disclosed subject matter.

Examples of different light illumination systems and/or light-emitting diode implementations will be described more fully hereinafter with reference to the accompanying drawings. These examples are not mutually exclusive, and features found in one example may be combined with features found in one or more other examples to achieve additional implementations. Accordingly, it will be understood that the examples shown in the accompanying drawings are provided for illustrative purposes only and they are not intended to limit the disclosure in any way. Like numbers refer generally to like elements throughout.

Further, it will be understood that, although the terms first, second, third, etc. may be used herein to describe various elements. However, these elements should not be limited by these terms. These terms may be used to distinguish one element from another. For example, a first element may be termed a second element and a second element may be termed a first element without departing from the scope of the disclosed subject matter. As used herein, the term "and/or" may include any and all combinations of one or more of the associated listed items.

It will also be understood that when an element is referred to as being "connected" or "coupled" to another element, it may be directly connected or coupled to the other element and/or connected or coupled to the other element via one or more intervening elements. In contrast, when an element is referred to as being "directly connected" or "directly coupled" to another element, there are no intervening elements present between the element and the other element. It will be understood that these terms are intended to encompass different orientations of the element in addition to any orientation depicted in the figures.

Relative terms such as "below," "above," "upper," "lower," "horizontal," or "vertical" may be used herein to describe a relationship of one element, zone, or region relative to another element, zone, or region as illustrated in the figures. A person of ordinary skill in the art will understand that these terms are intended to encompass different orientations of the device in addition to an orientation depicted in the figures. Further, whether the LEDs, LED arrays, electrical components and/or electronic components are housed on one, two, or more electronics boards, or in one or multiple physical locations may also depend on design constraints and/or a specific application.

Semiconductor-based light-emitting devices or optical power-emitting-devices, such as devices that emit ultraviolet (UV) or infrared (IR) optical power, are among the most efficient light sources currently available. These devices may include light-emitting diodes, resonant-cavity light emitting diodes, vertical-cavity laser diodes, edge-emitting lasers, or the like (simply referred to herein as LEDs). Due to their compact size and low power requirements, LEDs may be attractive candidates for many different applications. For example, they may be used as light sources (e.g., flash lights and camera flashes) for hand-held battery-powered devices, such as cameras and cellular phones. LEDs may also be used, for example, for automotive lighting, heads-up display (HUD) lighting, horticultural lighting, street lighting, a torch for video, general illumination (e.g., home, shop, office and studio lighting, theater/stage lighting, and architectural lighting), augmented reality (AR) lighting, virtual reality (VR) lighting, as back lights for displays, and IR spectroscopy. A single LED may provide light that is less bright than an incandescent light source, and, therefore, multi-junction devices or arrays of LEDs (such as monolithic LED arrays, micro LED arrays, etc.) may be used for applications where enhanced brightness is desired or required.

In various environments where LED-based lamps (or related illumination devices) are used to illuminate objects as well as for general lighting, it may be desirable to control aspects of the color temperature of the LED-based lamps (or a single lamp) in addition to a relative brightness (e.g., luminous flux) of the lamps. Such environments may include, for example, retail locations as well as hospitality locations such as restaurants and the like. In addition to the CCT, another lamp metric is the color-rendering index (CRI) of the lamp. The CRI is defined by the International Commission on Illumination (CIE) and provides a quantitative measure of an ability of any light source (including LEDs) to accurately represent colors in various objects in comparison with an ideal, or natural-light source. The highest possible CRI value is <NUM>. Another quantitative lamp metric is Duv. The Duv is a metric defined in, for example, CIE <NUM>, to represent the distance of a color point to the BBL. It is a positive value if the color point is above the BBL and a negative value if the color point is below the BBL. Color points above the BBL appear greenish in color and those below the BBL appear pinkish in color. The disclosed subject matter provides an apparatus to control both a color temperature (CCT and Duv) as well as a brightness level of the lamp. As described herein, the color temperature is related to both CCT and Duv in color-tuning applications.

The disclosed subject matter is therefore directed to a wireless color-tuning (covering one or both of CCT and Duv) scheme for driving various colors of LEDs including, for example, primary color (Red-Green-Blue or RGB) LEDs, or desaturated (pastel) RGB color LEDs, to make light of various color temperatures with a high color-rendering index (CRI) and high efficiency, specifically addressing color mixing using phosphor-converted color LEDs.

Upon reading and understanding the disclosed subject matter, a person of ordinary skill in the art will recognize that a similar scheme can be used for wireless control of luminous flux (e.g., "brightness level") of the LEDs as well.

As is known in the relevant art, the forward voltage of direct color LEDs decreases with increasing dominant wavelength. These LEDS can be driven with, for example, multichannel DC-to-DC converters. Advanced phosphor-converted color LEDs, targeting high efficacy and CRI, have been created providing for new possibilities for correlated color temperature (CCT) tuning applications. Some of the advanced color LEDs have desaturated color points and can be mixed to achieve white colors with <NUM>+ CRI over a wide CCT range. Other LEDs having <NUM>+ CRI implementations, or even <NUM>+ CRI implementations (or even lower CRI values), may also be used with the disclosed subject matter. These possibilities use LED circuits that realize, and increase or maximize, this potential. At the same time, the control circuits described herein are compatible with single-channel constant-current drivers to facilitate market adoption.

As is known to a person of ordinary skill in the art, since light output of an LED is proportional to an amount of current used to drive the LED, dimming an LED can be achieved by, for example, reducing the forward current transferred to the LED. In addition to or instead of changing an amount of current used to drive each of a number of individual LEDs, a control unit (described in detail with reference to <FIG>, below) or other type of multiplexer, switching apparatus, or similar apparatus known in the art, may rapidly switch selected ones of the LEDs between "on" and "off" states to achieve an appropriate level of dimming and color temperature for the selected lamp.

Generally, LED drive circuits are formed using either an analog-driver approach or a pulse-width modulation (PWM)-driver approach. In an analog driver approach, all colors are driven simultaneously. Each LED is driven independently by providing a different current for each LED. The analog driver results in a color shift and currently there is not a way to shift current three ways. Analog driving often results in certain colors of LEDs being driven into low current mode and other times, into very high current mode. Such a wide dynamic range imposes a challenge on sensing and control hardware.

In a PWM driver, each color is switched on, in sequence, at high speed. Each color is driven with substantially the same current. The mixed color is controlled by changing the duty cycle of each color. That is, one color can be driven for twice as long as another color to add into the mixed color. As human vision is unable to perceive very fast changing colors, the light appears to have one single color.

For example, a first LED (of a first color) is driven periodically with a current for a predetermined amount of time, then a second LED (of a second color) is driven periodically with the same current for a predetermined amount of time, and then a third LED (of a third color) is driven periodically with the current for a predetermined amount of time. Each of the three predetermined amounts of time may be the same amount of time or different amounts of time. The mixed color is therefore controlled by changing the duty cycle of each color. For example, if you have an RGB LED and desire a specific output, red may be driven for a portion of the cycle, green for a different portion of the cycle, and blue is driven for yet another portion of the cycle based on the perception of the human eye. Instead of driving the red LED at a lower current, it is driven at substantially the same current for a shorter time. This example demonstrates the downside of PWM with the LEDs being utilized poorly, therefore leading to an inefficient use of power. In some embodiments, the current is supplied from a voltage-controlled current source.

Another advantage of the disclosed subject matter over the prior art is that the desaturated RGB approach can create tunable light on and off the BBL, as well as on the BBL, for example, an isothermal CCT line (as described below) while maintaining a high CRI. Various other prior art systems, in comparison, utilize a CCT approach where tunable color-points fall on a straight line between two primary colors of LEDs (e.g., R-G, R-B, or G-B).

<FIG> shows a portion of an International Commission on Illumination (CIE) color chart <NUM>, including a black body line (BBL) <NUM> (also referred to as a Planckian locus) that forms a basis for understanding various embodiments of the subject matter disclosed herein. The BBL <NUM> shows the chromaticity coordinates for blackbody radiators of varying temperatures. It is generally agreed that, in most illumination situations, light sources should have chromaticity coordinates that lie on or near the BBL <NUM>. Various mathematical procedures known in the art are used to determine the "closest" blackbody radiator. As noted above, this common lamp specification parameter is called the correlated color temperature (CCT). A useful and complementary way to further describe the chromaticity is provided by the Duv value, which is an indication of the degree to which a lamp's chromaticity coordinate lies above the BBL <NUM> (a positive Duv value) or below the BBL <NUM> (a negative Duv value).

The portion of the color chart is shown to include a number of isothermal lines <NUM>. Even though each of these lines is not on the BBL <NUM>, any color point on the isothermal line <NUM> has a constant CCT. For example, a first isothermal line 117A has a CCT of <NUM>,<NUM>, a second isothermal line 117B has a CCT of <NUM>,<NUM>, a third isothermal line 117C has a CCT of <NUM>,<NUM>, and a fourth isothermal line 117D has a CCT of <NUM>,<NUM>.

With continuing reference to <FIG>, the CIE color chart <NUM> also shows a number of ellipses that represent a Macadam Ellipse (MAE) <NUM>, which is centered on the BBL <NUM> and extends one step <NUM>, three steps <NUM>, five steps <NUM>, or seven steps <NUM> in distance from the BBL <NUM>. The MAE is based on psychometric studies and defines a region on the CIE chromaticity diagram that contains all colors which are indistinguishable, to a typical observer, from a color at the center of the ellipse. Therefore, each of the MAE steps <NUM> to <NUM> (one step to seven steps) are seen to a typical observer as being substantially the same color as a color at the center of a respective one of the MAEs <NUM>. A series of curves, 115A, 115B, 115C, and 115D, represent substantially equal distances from the BBL <NUM> and are related to Duv values of, for example, +<NUM>, +<NUM>, <NUM>, - <NUM> and - <NUM>, respectively.

Referring now to <FIG>, and with continuing reference to <FIG>, <FIG> shows a chromaticity diagram <NUM> with approximate chromaticity coordinates of colors for typical coordinate values (as noted on the x-y scale of the chromaticity diagram <NUM>) for a red (R) LED at coordinate <NUM>, a green (G) LED at coordinate <NUM>, and a blue (B) LED at coordinate <NUM>. <FIG> shows an example of the chromaticity diagram <NUM> for defining the wavelength spectrum of a visible light source, in accordance with some embodiments. The chromaticity diagram <NUM> of <FIG> is only one way of defining a wavelength spectrum of a visible light source; other suitable definitions are known in the art and can also be used with the various embodiments of the disclosed subject matter described herein.

A convenient way to specify a portion of the chromaticity diagram <NUM> is through a collection of equations in the x-y plane, where each equation has a locus of solutions that defines a line on the chromaticity diagram <NUM>. The lines may intersect to specify a particular area, as described below in more detail with reference to <FIG>. As an alternative definition, the white light source can emit light that corresponds to light from a blackbody source operating at a given color temperature.

The chromaticity diagram <NUM> also shows the BBL <NUM> as described above with reference to <FIG>. Each of the three LED coordinate locations <NUM>, <NUM>, <NUM> are the CCT coordinates for "fully-saturated" LEDs of the respective colors green, blue, and red. However, if a "white light" is created by combining certain proportions of the R, G, and B LEDs, the CRI of such a combination would be extremely low. Typically, in the environments described above, such as retail or hospitality settings, a CRI of about <NUM> or higher is desirable.

<FIG> shows a revised version of the chromaticity diagram <NUM> of <FIG>, with approximate chromaticity coordinates for desaturated R, G, and B LEDs in proximity to the BBL, the desaturated R, G, and B LEDs having a color-rendering index (CRI) of approximately <NUM>+ and within a defined color temperature range, in accordance with various embodiments of the disclosed subject matter.

However, the chromaticity diagram <NUM> of <FIG> shows approximate chromaticity coordinates for desaturated (pastel) R, G, and B LEDs in proximity to the BBL <NUM>. Coordinate values (as noted on the x-y scale of the chromaticity diagram <NUM>) are shown for a desaturated red (R) LED at coordinate <NUM>, a desaturated green (G) LED at coordinate <NUM>, and a desaturated blue (B) LED at coordinate <NUM>. In various embodiments, a color temperature range of the desaturated R, G, and B LEDs may be in a range from about <NUM> to about <NUM>. In other embodiments, the desaturated R, G, and B LEDs may be in a color temperature range of, for example, about <NUM> to about <NUM>. In still other embodiments, the desaturated R, G, and B LEDs may be in a color temperature range of about <NUM> to about <NUM>. In still other embodiments, the desaturated R, G, and B LEDs may be selected to be in a wide range of color temperatures. As noted above, the color rendering index (CRI) of a light source does not indicate the apparent color of the light source; that information is given by the correlated color temperature (CCT). The CRI is therefore a quantitative measure of the ability of a light source to reveal the colors of various objects faithfully in comparison with an ideal or natural-light source.

In a specific exemplary embodiment, a triangle <NUM> formed between each of the coordinate values for the desaturated R, G, and B LEDs is also shown. The desaturated R, G, and B LEDs are formed (e.g., by a mixture of phosphors and/or a mixture of materials to form the LEDs as is known in the art) to have coordinate values in proximity to the BBL <NUM>. Consequently, the coordinate locations of the respective desaturated R, G, and B LEDs, and as outlined by the triangle <NUM>, has a CRI have approximately <NUM> or greater and an approximate tunable color-temperature-range of, for example, about <NUM> to about <NUM>. Therefore, the selection of a correlated color temperature (CCT) may be selected in the color-tuning application described herein such that all combinations of CCT selected all result in the lamp having a CRI of <NUM> or greater. Each of the desaturated R, G, and B LEDs may comprise a single LED or an array (or group) of LEDs, with each LED within the array or group having a desaturated color the same as or similar to the other LEDs within the array or group. A combination of the one or more desaturated R, G, and B LEDs comprises a lamp.

<FIG> shows a revised version of the chromaticity diagram <NUM> of <FIG>, with approximate chromaticity coordinates for desaturated R, G, and B LEDs in proximity to the BBL, the desaturated R, G, and B LEDs having a color-rendering index (CRI) of approximately <NUM>+ and within a defined color temperature range that is broader than the desaturated R, G, and B LEDs of <FIG>, in accordance with various embodiments of the disclosed subject matter.

However, the chromaticity diagram <NUM> of <FIG> shows approximate chromaticity coordinates for desaturated R, G, and B LEDs that are arranged farther from the BBL <NUM> than the desaturated R, G, and B LEDs of <FIG>. Coordinate values (as noted on the x-y scale of the chromaticity diagram <NUM>) are shown for a desaturated red (R) LED at coordinate <NUM>, a desaturated green (G) LED at coordinate <NUM>, and a desaturated blue (B) LED at coordinate <NUM>. In various embodiments, a color temperature range of the desaturated R, G, and B LEDs may be in a range from about <NUM> to about <NUM>. In other embodiments, the desaturated R, G, and B LEDs may be in a color temperature range of about <NUM> to about <NUM>. In still other embodiments, the desaturated R, G, and B LEDs may be in a color temperature range of about <NUM> to about <NUM>.

In a specific exemplary embodiment, a triangle <NUM> formed between each of the coordinate values for the desaturated R, G, and B LEDs is also shown. The desaturated R, G, and B LEDs are formed (e.g., by a mixture of phosphors and/or a mixture of materials to form the LEDs as is known in the art) to have coordinate values in proximity to the BBL <NUM>. Consequently, the coordinate locations of the respective desaturated R, G, and B LEDs, and as outlined by the triangle <NUM>, has a CRI have approximately <NUM> or greater and an approximate tunable color-temperature-range of, for example, about <NUM> to about <NUM>. Since the color temperature range is greater than the range shown in <FIG>, the CRI is commensurately decreased to about <NUM> or greater. However, a person of ordinary skill in the art will recognize that the desaturated R, G, and B LEDs may be produced to have individual color temperatures anywhere within the chromaticity diagram. Therefore, the selection of a correlated color temperature (CCT) may be selected in the color-tuning application described herein such that all combinations of CCT selected all result in the lamp having a CRI of <NUM> or greater. Each of the desaturated R, G, and B LEDs may comprise a single LED or an array (or group) of LEDs, with each LED within the array or group having a desaturated color the same as or similar to the other LEDs within the array or group. A combination of the one or more desaturated R, G, and B LEDs comprises a lamp.

<FIG> shows a color-tuning device <NUM> of the prior art requiring a hard-wired flux-control device <NUM> and a separate, hard-wired CCT-control device <NUM>. The flux-control device <NUM> is coupled to a single-channel driver circuit <NUM> and the CCT-control device is coupled to a combination LED-driving circuit/LED array <NUM>. The combination LED-driving circuit/LED array <NUM> may be a current-driver circuit, a PWM driver circuit, or a hybrid current-driver/PWM-driver circuit. Each of the flux-control device <NUM>, the CCT-control device <NUM>, and the single-channel driver circuit <NUM> is located in a customer facility <NUM> and all devices generally must be installed with applicable national and local rules governing high-voltage circuits. The combination LED-driving circuit/LED array <NUM> is generally located remotely (e.g., a few meters to dozens of meters or more) from the customer facility <NUM>. Consequently, both the initial purchase price and the installation price may be significant.

Consequently, in a conventional color-tunable system which operates off a single-channel constant-current driver, two control inputs are usually required, one for flux control (e.g., luminous flux or dimming) and the other for color tuning. The control inputs can be realized by, for example, electrical-mechanical devices, such as linear or rotary sliders, DIP switches, or a standard <NUM> V to 10V dimmer. While the dimmer for flux control may already be present in existing installations, it may be difficult and costly to accommodate a second dimmer for CCT control in a retrofit scenario due to electrical wiring requirements including various types of code compliance issues. The disclosed subject matter overcomes these limitations and expenses by eliminating all dimmers from an installation. As will be instantly recognizable to a person of ordinary skill in the art upon reading and understanding the disclosed subject matter described below, all physical control devices (e.g., dimmers) are eliminated.

<FIG> illustrates an embodiment of the invention and shows an example of a high-level schematic diagram of a wireless color-tuning device <NUM>, including a control unit <NUM>, a dimmer emulator <NUM>, a wireless control-device <NUM>, a wireless module <NUM>, and an LED array <NUM>. The LED array <NUM> may comprise, for example, the desaturated LEDs of <FIG> and <FIG>, in accordance with various embodiments of the disclosed subject matter.

The dimmer emulator <NUM> is described in detail with reference to <FIG>, below. However, in various embodiments, the dimmer emulator <NUM> can perform many operations consecutively. Such operations can include, for example, receiving and processing signals of at least one of CCT, Duv, and luminous flux. In some embodiments in which the dimmer emulator <NUM> performs multiple operations substantially concurrently, the dimmer emulator <NUM> may be instantiated multiple times to control various operations of the LED array <NUM>. If the wireless color-tuning device <NUM> is configured only to control luminous flux, a person of ordinary skill in the art may consider the wireless color-tuning device <NUM> to be a wireless LED-control device.

In some embodiments, each of the control unit <NUM>, the dimmer emulator <NUM>, the wireless module <NUM>, and the LED array <NUM> may be contained within a light-engine enclosure <NUM>. In some embodiments, one or more of the control unit <NUM>, the dimmer emulator <NUM>, the wireless module <NUM>, and/or the LED array <NUM> may be physically located within the light-engine enclosure <NUM> and others of the control unit <NUM>, the dimmer emulator <NUM>, the wireless module <NUM>, and/or the LED array <NUM> may be located outside of the light-engine enclosure <NUM> either nearby (e.g., within a few meters) or more remotely (e.g., dozens of meters) from each other. As is instantly recognizable to a person of ordinary skill in the art, all physical control-devices that are hard-wired (e.g., dimmers) are eliminated.

The wireless color-tuning device <NUM> includes a single-channel driver circuit (e.g., LED driver <NUM>). In some embodiments, the LED driver <NUM> may be located within a customer installation-area. In some embodiments, the LED driver <NUM> may be located remotely from a customer installation-area (but generally still within a customer facility). In some embodiments, the LED driver <NUM> may be located within the light-engine enclosure <NUM> (e.g., a junction box or other type of electronics enclosure used for housing various types of electrical or electronic components).

As is known to a person of ordinary skill in the art, since light output of an LED is proportional to an amount of current used to drive the LED, dimming an LED can be achieved by, for example, reducing the forward current transferred to the LED. The LED driver <NUM> sends a pre-determined amount of current to one, two, or all three colors of the LED array <NUM> to change an overall CCT and/or Duv level of the LED array <NUM>.

However, in addition to or instead of changing an amount of current used to drive each of individual ones of the LEDs in the LED array <NUM>, a control unit (described below with reference to <FIG>) rapidly switches selected ones of the LEDs or selected groups of colors in the LED array <NUM> between "on" and "off" states to achieve an appropriate level of dimming for the selected lamp in accordance with intensities desired as indicated by an end-user in setting a level of desired brightness on, for example, a flux-control device.

The LED driver <NUM> is coupled through an LED + signal line <NUM> and an LEDsignal line <NUM> provide power to the LED array <NUM>, through the control unit <NUM>. The control unit <NUM> may be, for example, a microcontroller, a microprocessor, or other processing unit known in the art. In some embodiments, the control unit <NUM> may be, for example, a special-purpose processor, such as a field-programmable gate array (FPGA) or an application specific integrated circuit (ASIC). The control unit <NUM> is configured to control the LED array <NUM>, which is coupled to the control unit <NUM>. For example, the control unit <NUM> receives wireless-based signals from the wireless module <NUM> to control various operations and lighting modes of the LED array <NUM>. As discussed above, the control operations may include, for example, a received signal to adjust luminous flux, CCT, and/or Duv distance from the BBL (for example, along an isothermal line of the received CCT - see <FIG>). The LED array <NUM> can be any type of multi-colored LED array including the desaturated-types of LEDs described above with reference to <FIG> and <FIG>.

Signals received from the wireless module <NUM> are interpreted or translated by an algorithm within the control unit <NUM>. The interpretation or translation provides a determination how the received wireless-signals affect operations of the LED array <NUM>. For example, the control unit <NUM> may relate a specific signal amplitude and signal type (e.g., a series and periodicity of the received signals) to a particular operation of the LED arrays <NUM>. The particular types of operations include CCT and Duv, and optionally also luminous flux.

In some embodiments, the determination of how the received wireless-signals affect operations of the LED array <NUM> is made by comparing the received signal to a lookup table (LUT) stored, for example, within the control unit <NUM> to a particular CCT, Duv, and luminous flux setting of one or more groups of individual colors of LEDs within the LED array <NUM>. In various embodiments, a translation mechanism of the control unit <NUM> includes both the algorithm embodiment and the LUT embodiment that may be used concurrently to translate various components of the received signal.

Further, although not shown explicitly, the control unit <NUM> may control switching operations of individual LEDs or groups of a single LED color within the LED array <NUM>. For example, the control unit can provide a PWM signal, based on the signal received from the wireless module <NUM>, to provide user-selected CCT, Duv, and/or luminous flux to the LED array <NUM> by switching selected colors or color groups of LEDs within the LED array <NUM>.

In various embodiments, at least one of the LED driver <NUM> (see <FIG>) and the control unit <NUM> may comprise or include a hybrid LED driving-circuit for CCT and Duv tuning, as well as for luminous-flus control. The hybrid driving-circuit can include an LED driver to produce a stabilized LED-driver current. In a specific exemplary embodiment, the control unit <NUM> delivers the current to the appropriate ones of LEDs or color groups of LEDs within the LED array <NUM> based on the desired CCT and Duv tuning. The hybrid driving-circuit within the control unit <NUM> may then be overlaid with PWM time-slicing directing current to at least two colors of the LED array <NUM>.

In various embodiments, the control unit <NUM> can be configured to have a special calibration mode. The calibration mode can function with either the algorithm (although the user may need access to the underlying software or firmware to change values) or values in the LUT. For example, the control unit <NUM> can enter the calibration mode if it is power cycled in a special sequence (e.g., a combination of long and short power-up/down cycles). While in this calibration mode, the user (e.g., a calibrating technician at the factory or an advanced end-user) is asked to change the correlation values of the output signals of the three control devices to their respective controlled-values (CCT, Duv, and/or flux). The control unit <NUM> then stores these two algorithms or values in, for example, software in an internal memory or firmware (e.g., an EEPROM), or hardware (e.g., a Field Programmable Gate Array (FPGA)). The internal memory can take a number of forms including, for example, electrically erasable programmable read-only memory (EEPROM), phase-change memory (PCM), flash memory, or various other types of non-volatile memory devices known in the art.

With continuing reference to <FIG>, the wireless module <NUM> provides signals, received wirelessly, to the control unit <NUM>. The wireless module <NUM> can be of any type of open-source standard or proprietary standard. In various embodiments, the wireless module <NUM> is configured to provide signals to the control unit <NUM> via pre-defined protocols (some of which are described below). In some embodiments, it may be desirable for the wireless module <NUM> to have a low-power consumption if it is powered from the LED current. In case the wireless module <NUM> operates in bursts of high-peak current, a large decoupling capacitor (described below with reference to <FIG>) may be used to reduce voltage/current (power) dips in power supplied to the LED (e.g., voltage and/or current), thereby eliminating or reducing light flicker from the LED array <NUM>.

The wireless module <NUM> may be configured to receive signals and to communicate in pre-defined protocols, known in the art, with the control unit <NUM> over, for example, a serial interface. In a specific exemplary embodiment, the wireless module <NUM> uses a universal asynchronous receiver-transmitter (UART) communications protocol. In other embodiments, the wireless module <NUM> may use an inter-integrated circuit (I-squared-C or I<NUM>C) protocol, a Serial Peripheral Interface (SPI), or other type of communications protocol known in the art. The wireless signals may be transferred from the wireless control-device <NUM> at a remote location to the wireless color-tuning device <NUM> via Wi-Fi®, Bluetooth®, Zigbee®, Z-Wave®, fifth-generation cellular-network technology (<NUM>), or other communication technology-signals known in the art.

In this exemplary embodiment, the wireless control-device <NUM> is shown to include buttons to either increase or decrease each of CCT, Duv, and luminous flux In other embodiments, the wireless control-device <NUM> may only include two sets of buttons to increase or decrease both CCT and luminous flux. In still other embodiments, the wireless control-device <NUM> may include only a single "increase and decrease" set of buttons with a selector switch to determine which one of, for example, CCT, Duv, and luminous flux relates to the increase and decrease set of buttons. The programming of such signals emanating from the wireless control-device <NUM> for a given communications protocol is known in the art.

The wireless control-device <NUM> may comprise an electrical control-device, a mechanical control-device, or a software control-device, each of which is configured to transmit a signal (e.g., indicative of end-user preferences for CCT, Duv, and luminous flux (an intensity level of the LED array <NUM>)) to the wireless module <NUM> of <FIG>. The wireless control-device <NUM> may be based on analog or digital signals. If the wireless control-device is based on an analog output, one of the components within the light-engine enclosure <NUM>, such as, for example, the wireless module <NUM> or the control unit <NUM>, can include an analog-to-digital converter (ADC).

The dimmer emulator <NUM> receives instructions from the control unit <NUM> to provide signals on a <NUM> V to <NUM> V+ signal line <NUM> and a <NUM> V to <NUM> V- signal line <NUM> to an input of the LED driver <NUM>. The dimmer emulator is described in more detail with reference to <FIG>, below.

In various embodiments, the dimmer emulator <NUM> is not powered by current supplied by the LED driver <NUM> to the LED array <NUM>. In these embodiments, the power for the dimmer emulator <NUM> may be supplied by the <NUM> V to <NUM> V interface of the LED driver <NUM>. Most commercially-available LED <NUM> V to <NUM> V interfaces provides a unit current from between about <NUM>µA and about <NUM>µA. In other embodiments, a separate power supply may be installed near the dimmer emulator <NUM> (e.g., within the light-engine enclosure <NUM>).

Typically, under the prior art, when a physical <NUM> V to <NUM> V dimmer is used, the physical dimmer is configured to control one or many LED drivers at the same time. When multiple LED drivers are connected to the same dimmer, the dimmer must be able to sink the sum of all the currents and still maintain a relatively stable, output voltage. On the other hand, the dimmer must also be able to operate reliably from just one LED driver. In electrical terms, the dimmer should behave as a variable constant-voltage regulator regardless of its input current. The output voltage is generally determined by its control input only (e.g., usually the position of a slider).

<FIG> shows an exemplary embodiment of the dimmer emulator <NUM> of <FIG>, in accordance with various exemplary embodiments of the disclosed subject matter. In this exemplary embodiment, the dimmer emulator <NUM> is shown to include a current source <NUM>, a first capacitor <NUM>, C<NUM>, an optional overcurrent-protection device <NUM>, F<NUM>, a diode <NUM>, D<NUM>, an adjustable-voltage reference <NUM>, U<NUM>, and other components described in detail below. The other components form a transient response and frequency-stability circuit, as well as a resistive voltage-divider with a variable voltage-divider ratio.

A combination of the current source <NUM> and the first capacitor <NUM>, C<NUM>, represents the <NUM> V to <NUM> V interface output of the LED driver <NUM> of <FIG>. In a specific exemplary embodiment, the first capacitor <NUM> comprises a <NUM>µF capacitor. The combination of the current source <NUM> and the first capacitor <NUM>, C<NUM>, provides a current, I<NUM>, of about <NUM>µA to the remainder of the circuit comprising the dimmer emulator <NUM>.

The diode <NUM>, D<NUM>, protects the dimmer emulator <NUM> circuit from moderate levels of over-current and/or over-voltage. The optional overcurrent-protection device <NUM>, F<NUM>, may comprise a resettable fuse for protection of the dimmer emulator <NUM> circuit against high levels of over-current, such as erroneously connecting an output of the LED driver <NUM> output to the dimmer emulator <NUM> circuit. Therefore, the optional overcurrent-protection device <NUM> is inserted in series upstream of the diode <NUM> (e.g., between the combination of the current source <NUM> and the first capacitor <NUM>, C<NUM>, and the diode <NUM>). In a specific exemplary embodiment, the diode <NUM> comprises an <NUM> V Zener diode. The optional overcurrent-protection device <NUM> may comprise a positive temperature-coefficient (PTC) device. In various embodiments, the optional overcurrent-protection device <NUM> is also known generically as any type of passive-component resettable fuse device such as a multi-fuse, poly-fuse, or poly-switch device.

In various embodiments, the adjustable-voltage reference <NUM>, U<NUM> (described in more detail below), comprises a precision, variable shunt-voltage regulator. In this embodiment, the adjustable-voltage reference <NUM>, U<NUM>, comprises a low-voltage, three-terminal adjustable-voltage reference, having a specified thermal stability over a selected temperature range. In a specific exemplary embodiment, the adjustable-voltage reference <NUM>, U<NUM>, is a TLV431AFTA device (manufactured by Diodes Incorporated, <NUM> Hedgcoxe Road, Suite <NUM>; Plano, Texas, <NUM>, USA). In this specific exemplary embodiment, the output voltage of the adjustable-voltage reference <NUM> can be set to any value between VREF of <NUM> V and <NUM> V with two external resistors - a fourth resistor <NUM>, R<NUM>, and a fifth resistor <NUM>, R<NUM>. In a specific exemplary embodiment, values of resistance for R<NUM> and R<NUM> are each about <NUM> kΩ. As discussed in more detail below, an output voltage, Vout, can be set to be as low as the reference voltage VREF (e.g., <NUM> V ± <NUM>%).

With continuing reference to <FIG>, a first resistor <NUM>, R<NUM>, a second resistor <NUM>, R<NUM>, and a third resistor, R<NUM>, combined with a transistor <NUM>, M<NUM>, collectively determine a voltage appearing at the <NUM> V to <NUM> V+ node (see <FIG>). An operation of the transistor <NUM>, M<NUM>, is controlled by a signal on a signal line <NUM> that is coupled to a gate of the transistor <NUM>. The signal may be, for example, a PWM signal. This collective combination of components, R<NUM>, R<NUM>, R<NUM>, and M<NUM>, determines the voltage regardless of the input current. In this embodiment, the only control signal is the duty cycle of the PWM signal. In a specific exemplary embodiment, the signal line <NUM> is coupled to the gate of a field-effect transistor (e.g., a MOSFET device). Each of the second resistor <NUM> and the third resistor <NUM> are coupled to opposite sides of the transistor <NUM> (e.g., to the drain and source of the transistor). Therefore, the PWM signal on the signal line <NUM> controls the conductance on current by the drain and the source.

Between <NUM>% and <NUM>%, the circuit is able to cover a wide voltage range. Analyses of two extremes of the PWM duty cycle is presented immediately below to better illustrate the function of this collective combination of components.

At a <NUM>% PWM duty-cycle (e.g., no voltage signal on the signal line <NUM> is present), the transistor <NUM>, M<NUM>, is constantly off. Therefore, the third resistor <NUM>, R<NUM>, is open-circuit. Consequently, the first resistor <NUM>, R<NUM>, and the second resistor <NUM>, R<NUM>, form a resistive voltage-divider. When the adjustable-voltage reference <NUM>, U<NUM>, is in operation, the reference input-voltage is approximately, for example, <NUM> V. In this case, a value within the <NUM> V to <NUM> V+ range is determined by: <MAT>.

Using the exemplary values of R<NUM> = <NUM> kΩ and R<NUM> = <NUM> kΩ given above, the value for Vout determined by equation (<NUM>) is approximately <NUM> V. As the resistive voltage-divider comprised of R<NUM> and R<NUM> is an attenuator, the value of <NUM> V to <NUM> V+ cannot be lower than the reference voltage (e.g., <NUM> V). If a lower voltage is desired, a similar circuit with a reference voltage lower than <NUM> V can be used.

Continuing with the other extreme of the analyses, at a <NUM>% PWM duty-cycle (e.g., a maximum voltage signal on the signal line <NUM> is present), the transistor <NUM>, M<NUM>, is constantly on. Consequently, the third resistor <NUM>, R<NUM>, is in parallel with the second resistor <NUM>, R<NUM>, and the parallel combination of R<NUM> and R<NUM> is in series with the first resistor <NUM>, R<NUM>. In this case, the value of the <NUM> V to <NUM> V signal is determined by: <MAT>.

As recognizable to a skilled artisan, there are now two equations and three variables. However, a third equation is given by the <NUM> V to <NUM> V+ voltage at the <NUM>% PWM duty-cycle and the minimum input current of <NUM>µA as given by the exemplary description above. The target therefore is to have <NUM> V at this condition (as noted above, a broad voltage range is desired). The adjustable-voltage reference <NUM>, U<NUM>, consumes some current and thus not all of the <NUM>µA flows through the first resistor <NUM>, R<NUM>. The actual current consumption of the adjustable-voltage reference <NUM>, U<NUM>, in regulation, can experimentally be obtained. Therefore, the third equation becomes: <MAT>.

For the exemplary resistor values provided above, the value of IR1 is approximately equal to <NUM>µA (therefore, the current loss through the adjustable-voltage reference <NUM>, U<NUM>, is approximately <NUM>µA (in this example, <NUM>µA - <NUM>µA = <NUM>µA).

In between these two states (<NUM> V at the <NUM>% PWM duty-cycle and <NUM> V at the <NUM>% PWM duty-cycle), the switching of the transistor <NUM>, M<NUM>, causes the effective resistance in the path of the third resistor <NUM>, R<NUM>, to vary between the value of R<NUM> and a very high impedance. The effective change in the resistance value of R<NUM> creates a resistive voltage-divider with a variable ratio. In a specific exemplary embodiment, values of resistance for R<NUM>, R<NUM>, and R<NUM> are about <NUM> kΩ, about <NUM> kΩ, and about <NUM> kΩ, respectively.

With continuing reference to <FIG>, a second capacitor <NUM>, C<NUM>, functions as a decoupling capacitor. The second capacitor <NUM>, C<NUM>, removes high-frequency ripple caused by the switching of the transistor <NUM>, M<NUM> due to application of the PWM signal on the signal line <NUM>. All other components shown in <FIG>, for example, a third capacitor <NUM>, C<NUM>, a fourth capacitor <NUM>, C<NUM>, and a fifth capacitor <NUM>, C<NUM>, are for transient response and frequency stability.

In a specific exemplary embodiment, a value of capacitance of C<NUM> is about <NUM>µF. Values for C<NUM>, C<NUM>, and C<NUM> are each about <NUM> nF.

In some embodiments, various ones of the various components and modules described above may comprise software-based modules (e.g., code stored or otherwise embodied in a machine-readable medium or in a transmission medium), hardware modules, or any suitable combination thereof. A hardware module is a tangible (e.g., non-transitory) physical component (e.g., a set of one or more microcontrollers or microprocessors or other hardware-based devices) capable of performing certain operations and interpreting the output signals received from, for example, the wireless module <NUM> of <FIG>. The one or more modules may be configured or arranged in a certain physical manner. In various embodiments, one or more microcontrollers or microprocessors, or one or more hardware modules thereof, may be configured by software (e.g., through an application or portion thereof) as a hardware module that operates to perform operations described herein for that module.

In some example embodiments, a hardware module may be implemented, for example, mechanically or electronically, or by any suitable combination thereof.

For example, a hardware module may include dedicated circuitry or logic that is permanently configured to perform certain operations. A hardware module may be or include a special-purpose processor, such as a field-programmable gate array (FPGA) or an application specific integrated circuit (ASIC). A hardware module may also include programmable logic or circuitry that is temporarily configured by software to perform certain operations. As an example, a hardware module may include software encompassed within a central processing unit (CPU) or other programmable processor. It will be appreciated that a decision to implement a hardware module mechanically, electrically, in dedicated and permanently configured circuitry, or in temporarily configured circuitry (e.g., configured by software) may be driven by cost and time considerations.

In various embodiments, many of the components described may comprise one or more modules configured to implement the functions disclosed herein. In some embodiments, the modules may constitute software modules (e.g., code stored on or otherwise embodied in a machine-readable medium or in a transmission medium), hardware modules, or any suitable combination thereof. A "hardware module" is a tangible (e.g., non-transitory) physical component (e.g., a set of one or more microprocessors or other hardware-based devices) capable of performing certain operations and interpreting certain signals. The one or more modules may be configured or arranged in a certain physical manner. In various embodiments, one or more microprocessors or one or more hardware modules thereof may be configured by software (e.g., an application or portion thereof) as a hardware module that operates to perform operations described herein for that module.

In some example embodiments, a hardware module may be implemented, for example, mechanically or electronically, or by any suitable combination thereof. For example, a hardware module may include dedicated circuitry or logic that is permanently configured to perform certain operations. As noted above, a hardware module may comprise or include a special-purpose processor, such as an FPGA or an ASIC. A hardware module may also include programmable logic or circuitry that is temporarily configured by software to perform certain operations, such as interpretation of the various signals received by the control unit <NUM> from the wireless module <NUM> (see <FIG>).

Thus, in one embodiment, a method of color tuning a light-emitting diode (LED) array includes receiving at a wireless module a wireless signal that includes at least one signal of signals including a CCT value and a Duv of a temperature of the LED array from a BBL. The method also includes receiving one or more signals from the wireless module at a control unit and translating, by the control unit, the one or more signals based on the wireless signal from the wireless control-device. The control unit is further coupled to the LED array and to an LED driver, and the method further comprises the control unit receiving power for the LED array from the LED driver and providing the power to the LED array in a manner based on the translated signals. A dimmer emulator is coupled to the control unit. The method further comprises the dimmer emulator providing one or more control signals to the LED driver as controlled by the control unit and that are dependent on the translated signals.

The method may further comprise, in the dimmer emulator, adjusting an adjustable-voltage reference coupled to a current source and to a transistor to alter a variable voltage-divider ratio of a resistive voltage-divider, the resistive voltage-divider including a first resistor coupled in series to a first end of a second resistor and a first end of a third resistor, each of the second resistor and the third resistor being coupled on their respective second ends to opposite sides of the transistor.

The method may further comprise controlling operation of the transistor by applying a PWM signal to a signal line coupled to a gate of the transistor.

The method may further comprise the control unit correlating a value of the signal received from the wireless module with a corresponding value of at least one value of values including the CCT value and the Duv value and/or using a LUT to correlate a value of the signal received from the wireless module with a corresponding value of at least one value of values including the CCT value and the Duv value.

The method may further comprise the control unit supplying a PWM time-slicing signal to at least two of three-color groups of LEDs within the LED array, the at least two of three-color groups of LEDs being based at least partially on a value of a desired value of CCT and/or a desired Duv.

The method further comprises the control unit using an algorithm and a LUT to correlate a value of the signal received from the wireless module with a corresponding value of the luminous-flux level of the LED array.

In another embodiment, a computer-readable storage medium that stores instructions for execution by one or more processors of a control apparatus to color tune a light-emitting diode (LED) array. The instructions when executed configure the one or more processors to: receive at a wireless module a wireless signal that includes at least one signal of signals including a CCT value and a Duv of a temperature of the LED array from a BBL, receive one or more signals from the wireless module at a control unit and translate, by the control unit, the one or more signals based on the wireless signal from the wireless control-device. The control unit is further coupled to the LED array and to an LED driver, and the instructions when executed further configure the control unit to receive power for the LED array from the LED driver and providing the power to the LED array in a manner based on the translated signals. A dimmer emulator is coupled to the control unit. The instructions when executed further configure the dimmer emulator to provide one or more control signals to the LED driver as controlled by the control unit and that are dependent on the translated signals.

The instructions when executed further configure, in the dimmer emulator, adjusting an adjustable-voltage reference coupled to a current source and to a transistor to alter a variable voltage-divider ratio of a resistive voltage-divider, the resistive voltage-divider including a first resistor coupled in series to a first end of a second resistor and a first end of a third resistor, each of the second resistor and the third resistor being coupled on their respective second ends to opposite sides of the transistor.

The instructions when executed further configure the one or more processors to control operation of the transistor by applying a PWM signal to a signal line coupled to a gate of the transistor.

The instructions when executed further configure the control unit to correlate a value of the signal received from the wireless module with a corresponding value of at least one value of values including the CCT value and the Duv value and/or use a LUT to correlate a value of the signal received from the wireless module with a corresponding value of at least one value of values including the CCT value and the Duv value.

The instructions when executed further configure the control unit to supply a PWM time-slicing signal to at least two of three-color groups of LEDs within the LED array, the at least two of three-color groups of LEDs being based at least partially on a value of a desired value of CCT and/or a desired Duv.

The instructions when executed further configure the control unit to use an algorithm and a LUT to correlate a value of the signal received from the wireless module with a corresponding value of the luminous-flux level of the LED array.

The description above includes illustrative examples, devices, systems, and methods that embody the disclosed subject matter. In the description, for purposes of explanation, numerous specific details were set forth in order to provide an understanding of various embodiments of the disclosed subject matter. It will be evident, however, to those of ordinary skill in the art that various embodiments of the subject matter may be practiced without these specific details. Further, well-known structures, materials, and techniques have not been shown in detail, so as not to obscure the various illustrated embodiments.

As used herein, the term "or" may be construed in an inclusive or exclusive sense. Further, other embodiments will be understood by a person of ordinary skill in the art upon reading and understanding the disclosure provided. Further, upon reading and understanding the disclosure provided herein, the person of ordinary skill in the art will readily understand that various combinations of the techniques and examples provided herein may all be applied in various combinations.

Although various embodiments are discussed separately, these separate embodiments are not intended to be considered as independent techniques or designs. As indicated above, each of the various portions may be inter-related and each may be used separately or in combination with other types of electrical control-devices, such as dimmers and related devices. Consequently, although various embodiments of methods, operations, and processes have been described, these methods, operations, and processes may be used either separately or in various combinations.

Claim 1:
A control apparatus (<NUM>) to color tune a multi-colored LED array (<NUM>), the apparatus comprising:
- a wireless module (<NUM>) configured to receive a wireless signal from a wireless control-device (<NUM>), the received wireless signal comprising at least a correlated color temperature value and a distance value of a temperature of the multi-colored LED array (<NUM>) from a black-body line;
- a control unit (<NUM>) coupled to the wireless module (<NUM>) and configured to translate signals received from the wireless module (<NUM>), the control unit (<NUM>) further coupled to the multi-colored LED array (<NUM>) and to an LED driver (<NUM>), the control unit (<NUM>) configured to receive power for the multi-colored LED array (<NUM>) from the LED driver (<NUM>), the control unit (<NUM>) further configured to provide the power to the multi-colored LED array (<NUM>) in a manner based on the translated signals; and
- a dimmer emulator (<NUM>) coupled to the control unit (<NUM>) and configured to provide one or more control signals to the LED driver (<NUM>) as controlled by the control unit (<NUM>) and dependent on the translated signals;
characterized in that the dimmer emulator comprises:
a current source (<NUM>);
an adjustable-voltage reference (<NUM>) coupled to the current source (<NUM>);
a transistor (<NUM>) coupled to the adjustable-voltage reference (<NUM>); and
a resistive voltage-divider (R1, R2, R3) configured to have a variable voltage-divider ratio; wherein the resistive voltage-divider includes a first resistor (R1) coupled in series to a first end of a second resistor (R2) and a first end of a third resistor (R3), each of the second resistor (R2) and the third resistor (R3) being coupled on their respective second ends to opposite sides of the transistor (<NUM>), further comprising a signal line (<NUM>) coupled to a gate of the transistor (<NUM>), wherein an operation of the transistor (<NUM>) is controlled by applying a pulse-width modulation signal to the signal line (<NUM>) and wherein the variable voltage-divider ratio is determined by a duty cycle of the applied pulse-width modulation signal.