LED lighting system

Abstract

An LED lighting system capable of realizing a dimming function that adjusts to reduce the brightness of output light, the LED lighting system including: an LED light source including three or more LED channels respectively configured to be capable of emitting light of different color temperatures; and a circuit configured to be capable of electrically driving the three or more LED channels. The circuit is configured to drive the three or more LED channels so as to mutually link together the reduction of the brightness and the color temperature of the output light obtained by the LED light source when dimming the brightness of the output light.

Description

Technical Field

[0001] This invention relates to an LED lighting system, and more specifically, to an LED lighting system configured to change the correlated color temperature (CCT) of light in conjunction with dimming. Background Technology

[0002] Light-emitting diodes (LEDs), with their long lifespan and excellent energy efficiency, are used as light sources in various types of lighting systems, and numerous attempts are underway to improve lighting quality by enhancing the light characteristics of LEDs. As one example of these attempts, a technique has been introduced in LED lighting systems with dimming capabilities that gradually reduce the correlated color temperature as the brightness decreases (the so-called dim-to-warm technology).

[0003] For example, US Patent 7,288,902 discloses a technique for controlling the drive current of LEDs with different color temperatures to mimic the color temperature changes corresponding to brightness variations in incandescent lamps. Another example is US Patent 9,769,895, which discloses a technique for independently controlling the drive current of white and red LEDs to mimic the dimming characteristics of incandescent lamps. Yet another example is Korean Patent KR10-2136773, which discloses a technique for independently controlling the drive current of cool and warm LEDs to mimic the correlated color temperature of an incandescent bulb during dimming. And yet another example is US Patent 8,330,394, which discloses a technique for controlling the drive voltage of LEDs so that the color of the light changes from white to red with dimming.

[0004] These existing technologies propose a method for dependently changing the correlated color temperature during dimming of an LED lighting system, but only suggest warming the correlated color temperature as brightness decreases to mimic the light characteristics of an incandescent lamp. Therefore, there is a need to optimize the LED lighting system while considering the required correlation between brightness and correlated color temperature during dimming to achieve the desired light characteristics.

[0005] <Prior art documents>

[0006] - US Patent No. 7,288,902 (October 30, 2007)

[0007] - US Patent No. 9,769,895 (September 19, 2017)

[0008] -Korean Patent KR10-2136773 (July 16, 2020)

[0009] - US Patent No. 8,330,394 (December 11, 2012) Summary of the Invention

[0010] Technical issues

[0011] The problem to be solved by the present invention is to provide an LED lighting system having a color temperature control function that optimizes the structure and manufacturing cost by using multiple LEDs with different correlated color temperatures according to the brightness and correlated color temperature required during dimming.

[0012] Technical solution

[0013] According to an embodiment of the present invention, an LED lighting system is capable of dimming to reduce the brightness of the output light. The LED lighting system includes: an LED light source comprising three or more LED channels respectively configured to emit light of different color temperatures; and a circuit configured to electrically drive the three or more LED channels. The circuit is configured to drive the three or more LED channels such that, during dimming to reduce the brightness of the output light, the brightness and color temperature of the output light obtained from the LED light source decrease together in a coordinated manner.

[0014] The circuit can operate to generate output light that depends on the dimming level by driving the remaining LED channels, except for at least one of the three or more LED channels, at all dimming levels corresponding to the dimming function.

[0015] The circuit can be configured to drive the three or more LED channels by dividing them into a number of dimming control intervals that are one less than the number of the three or more LED channels, and the circuit can be configured to achieve the brightness and color temperature of the output light depending on the dimming level by selectively using one of the combinations of two LED channels selected from the three or more LED channels in each dimming control interval.

[0016] The combination of the two LED channels can be composed of two LED channels with adjacent color temperatures from among the three or more LED channels.

[0017] The circuit can be configured to drive one or more LED channels of a selected LED combination at each dimming level to achieve the brightness and color temperature of the output light depending on the dimming level.

[0018] The light generated by the combination of the two LED channels can be configured to generate light within a 10th-order MacAdam ellipse located at coordinates on the blackbody trajectory on the chromaticity diagram.

[0019] Each LED channel can emit light within a 10th-order McAdam ellipse located at coordinates on the blackbody trajectory on the chromaticity diagram.

[0020] Among the three or more LED channels, the LED channel emitting light with the highest color temperature can have a spectrum with a maximum relative luminous intensity of 60% or more in the 380 to 500 nm wavelength band, and the LED channel emitting light with the lowest color temperature among the three or more LED channels can have a spectrum with a maximum relative luminous intensity of 30% or less in the 380 to 500 nm wavelength band.

[0021] The LED lighting system according to another embodiment may further include: a control interface configured to receive a desired dimming level from a user and output a dimming signal corresponding to the input dimming level to the circuit.

[0022] The circuit can be configured to implement a timer function, wherein when the timer function is activated, the circuit can be configured to control the LED channel with the lowest color temperature to automatically dim the emitted light for a predetermined time and then turn it off, or to control the LED channel with the lowest color temperature and the LED channel with the second lowest color temperature to automatically dim the mixed light as the color temperature decreases for a predetermined time and then turn it off.

[0023] The ratio of the maximum brightness of the LED channel emitting the highest color temperature among the three or more LED channels to the maximum brightness of the k-th LED channel in descending order of color temperature can be less than the value calculated by (N-k+1)2 / (4*(N-1)) (where 1<k<=N).

[0024] The three or more LED channels may include a first LED channel having at least one first LED that emits light with a first color temperature, a second LED channel having at least one second LED with a second color temperature lower than the first color temperature, and a third LED channel having at least one third LED with a third color temperature lower than the second color temperature, wherein the circuit can be controlled to selectively use one of a combination of two LED channels from the first to the third LED channels to achieve a desired brightness and a desired color temperature based on the brightness of the mixed light corresponding to the dimming level.

[0025] The first and second LED channels can emit white light, and the third LED channel can emit amber or red light.

[0026] The first color temperature can be from 10,000K to 4,000K, the second color temperature can be from 3,500K to 2,500K, and the third color temperature can be from 2,500K to 1,000K.

[0027] The first to third LED channels can emit light within a 10th-order McAdam ellipse located at coordinates on the blackbody trajectory on the chromaticity diagram.

[0028] The effects of the invention

[0029] According to the present invention, since three or more LED channels are provided that emit light with different color temperatures respectively, and two LED channels with adjacent color temperatures are used to generate mixed light in each interval during dimming, mixed light can be generated in a wide range of color temperatures, and colors that similarly follow the blackbody trajectory on the chromaticity diagram can be expressed.

[0030] Furthermore, as the brightness dims with increasing dimming level, the brightness and color temperature decrease together, thereby reducing the maximum brightness of the LED channel emitting warm light with a low color temperature, and thus reducing the number of LEDs in the LED channel emitting light with a low color temperature. Attached Figure Description

[0031] Figure 1 This is a block diagram of an LED lighting system according to an embodiment of the present invention.

[0032] Figure 2 A chromaticity diagram showing the schematic coordinates of the light from three LED channels with different color temperatures in an LED lighting system according to an embodiment of the present invention is provided.

[0033] Figure 3 The diagram shows that it can be represented by... Figure 2 The chromaticity diagram shows the chromaticity of the trajectory of the mixed light formed by the combination of two of the three types of light with relatively high color temperatures.

[0034] Figure 4 The illustration shows that it can be represented by... Figure 2 The chromaticity diagram shows the chromaticity of the trajectory of the mixed light formed by the combination of two of the three types of light with relatively low color temperatures.

[0035] Figure 5 The diagram shows the use of Figure 2 The chromaticity diagram shows an example of a chart representing the target brightness and target color temperature corresponding to the dimming level, with the three light types represented by the diagram.

[0036] Figure 6 The diagram shows the representation corresponding to the implementation. Figure 5 The chart shows an example of the brightness of three light levels for the target brightness and target color temperature dimming levels.

[0037] Figure 7 A chromaticity diagram illustrating schematic coordinates of light from three LED channels with different color temperatures in an LED lighting system, according to another embodiment of the present invention, is shown.

[0038] Figure 8The diagram shows that it can be represented by... Figure 7 The chromaticity diagram shows the chromaticity of the trajectory of the mixed light formed by the combination of two of the three types of light with relatively high color temperatures.

[0039] Figure 9 The diagram shows that it can be represented by... Figure 7 The chromaticity diagram shows the chromaticity of the trajectory of the mixed light formed by the combination of two of the three types of light with relatively low color temperatures.

[0040] Figure 10 The diagram shows the use of Figure 7 The chromaticity diagram shows an example of a chart representing the target brightness and target color temperature corresponding to the dimming level, with the three light types represented by the diagram.

[0041] Figure 11 The diagram shows the representation corresponding to the implementation. Figure 10 The chart shows an example of the brightness of three light levels for the target brightness and target color temperature dimming levels.

[0042] Figure 12 This is a chromaticity diagram representing the exemplary coordinates of the light from three LED channels with different color temperatures in an embodiment of the present invention.

[0043] Figure 13 The prior art shows a chromaticity diagram displaying the coordinates of two lights with different color temperatures. Detailed Implementation

[0044] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0045] Figure 1 A block diagram of an LED lighting system according to an embodiment of the present invention is shown. (Refer to...) Figure 1 The LED light source 10 includes three or more, for example, N (a natural number greater than or equal to 3) LED channels 11, 12, and 13. Each LED channel 11, 12, and 13 includes one or more LEDs and is configured to emit light with different color temperatures ranging from the highest to the lowest relative color temperature. Here, color temperature refers to correlated color temperature (CCT), hereinafter referred to as color temperature.

[0046] The LED lighting system of the present invention can be implemented as any type of lighting device, such as a table lamp, a lamp mounted on a ceiling or wall.

[0047] LED channel #1 11 emits light with the highest color temperature among N LED channels, while the remaining LED channels emit light with gradually decreasing color temperatures as the number of channels increases. Therefore, LED channel #N 13 emits light with the relatively lowest color temperature. Two embodiments including three LED channels are described below, but the number of LED channels is not limited to this; four or more LED channels can be provided. Each LED channel 11, 12, 13 may include one or more LEDs emitting light of the corresponding color temperature, such as white LEDs, red LEDs, and amber LEDs emitting light with various color temperatures as the light source.

[0048] Driver 20 is configured to electrically drive each LED channel 11, 12, 13. For example, driver 20 may be a circuit capable of selectively driving each LED channel 11, 12, 13 by applying a drive current to each LED channel. For example, driver 20 may be a current driver capable of supplying a desired amount of current, a constant voltage driver capable of applying a constant voltage, or a circuit capable of driving the LEDs of the LED channels in any manner. Figure 1 As shown, driver 20 includes three or more drivers 21, 22, 23 configured for each LED channel 11, 12, 13 to drive each LED channel 11, 12, 13 respectively.

[0049] The control unit 30 is configured to control the driver 20 in a manner that adjusts the brightness of the light emitted from each LED channel 11, 12, 13 according to an input dimming signal. The dimming signal can be input to the control unit 30 via the control interface 40. The control unit 30 may include a microprocessor, memory, and related hardware and software, and can be programmed to control the driver 20 according to the control logic described below.

[0050] Control interface 40 is configured to receive input of a desired dimming level from the user. When the user inputs a desired dimming level using control interface 40, control interface 40 generates a dimming signal corresponding to the input dimming level and outputs the dimming signal to control unit 30. Control unit 30 can then output a control signal to drive driver 20 based on the transmitted dimming signal. At this time, control unit 30 can obtain the drive current for driving each LED channel 11, 12, 13 from dimming table 50 to achieve the input dimming level. Dimming table 50 may be a lookup table including data on the drive current for each LED channel 11, 12, 13 to achieve the dimming level (i.e., the brightness level of the light) corresponding to each dimming signal. As another example, control unit 30 can calculate the drive current corresponding to the input dimming level using a predetermined function.

[0051] The control interface 40 can be integrated with elements that constitute the main body of the lighting system, such as the control unit 30, driver 20, and LED light source 30, or it can be configured remotely and connected to them via wired or wireless means. Furthermore, the control interface 40 can be configured with any interface, such as a rotary or sliding knob or a touchscreen input mechanism, to allow the user to input the desired dimming level.

[0052] The control unit 30 controls the brightness and color temperature of the mixed light emitted from the LED light source 10 to decrease in conjunction with the increase of the dimming level indicated by the dimming signal. Here, an increase in the dimming level means that the brightness of the light gradually dims. For example, the dimming level can include 21 levels from level 1 to level 21, where level 1 can represent the state of maximum brightness and level 21 can represent the state of zero brightness. In this process, the brightness can be set to gradually decrease as the dimming level increases from level 1 to level 21. In an exemplary embodiment of the present invention, the brightness decreases as the dimming level increases, and the color temperature also decreases in conjunction with the brightness. Thus, as the brightness decreases due to dimming, the color temperature also decreases in conjunction with the brightness, and a warm light with a low color temperature can be generated according to the dimming process, thereby realizing the color temperature control function. At a low dimming level, a bright mixed light with a high color temperature is generated for work and study; at a high dimming level, a dark mixed light with a low color temperature is generated for rest and sleep.

[0053] Further, according to an embodiment of the invention, the control unit 30 is configured to control the driver 20 according to N-1 consecutive control intervals set based on increasing dimming levels. At least one of two LED channels with adjacent color temperatures is used to obtain the mixed light in each control interval. For example, when using N LED channels numbered 1 to N arranged in ascending order of color temperature, in the control interval with the lowest dimming level, at least one of LED channels 1 and 2 is used to generate the mixed light, and in the control interval of the next dimming level, at least one of the second and third LED channels is used to generate the mixed light. In this way, dimming is performed sequentially using two LED channels with adjacent color temperatures in each control interval, and in the last control interval, at least one of LED channel N and the previous LED channel is used to generate the mixed light. Since two LED channels with adjacent color temperatures are used to generate the mixed light in each control interval in this way, light characteristics that approximate the desired trajectory on the chromaticity diagram can be achieved during dimming. This will be described again later.

[0054] Each LED channel 11, 12, and 13 can emit light within a 10th-order McAdam ellipse located at the coordinates of the blackbody trajectory on the chromaticity diagram.

[0055] LED channel 11, emitting light with the highest color temperature among the N LED channels, can emit light with a spectrum having a maximum relative emission intensity of over 60% in the 380-500nm wavelength range. LED channel 13, emitting light with the lowest color temperature among the N LED channels, can emit light with a spectrum having a maximum relative emission intensity of less than 30% in the 380-500nm wavelength range. In the high-brightness, low-light level, the high-color-temperature light, which constitutes the majority of the mixed light, includes more of the spectrum near 460nm, which inhibits melatonin secretion; and in the low-brightness, high-light level, the low-color-temperature light, which constitutes the majority of the mixed light, includes less of the spectrum near 460nm. Therefore, in the high-brightness state, melatonin secretion can be suppressed to improve concentration; and in the low-brightness state, it can aid in melatonin secretion and sleep.

[0056] On the other hand, according to an embodiment of the present invention, the control unit 30 can be configured to implement a timer function. When the timer function is activated, dimming can be performed by driving the LED channel with the lowest color temperature among the N LED channels. Specifically, the lamp with the lowest color temperature is automatically dimmed and then turned off after a predetermined time. On the other hand, in another example, when the timer function is activated, the LED channel emitting light with the lowest color temperature (i.e., the Nth LED channel) and the LED channel emitting light with the second lowest color temperature (i.e., the (N-1)th LED channel) among the N LED channels can be driven together to gradually dim and then turn off as the color temperature decreases.

[0057] On the other hand, another embodiment of the LED lighting system of the present invention can have a wireless charging function for wireless charging of mobile phones, etc. When the LED lighting system of the present invention is implemented in the form of a table lamp, a mobile phone stand pad for wireless charging can be provided, and the mobile phone can be placed on the pad for wireless charging. A detailed description of the circuitry for implementing the wireless charging function is omitted.

[0058] In a system consisting of N LED channels, if the color temperature decreases linearly with increasing dimming level, and the brightness change decreases with an m-th order polynomial, then the k-th LED channel and the (k-1)-th LED channel are mixed. The mixing ratio y between the k-th and (k-1)-th LED channels within the mixing interval is... k It is represented by the following numerical expression 1.

[0059] [Formula 1]

[0060] y k =-(N-1)x+(N-k+1)

[0061] Here, x is the normalized value of the dimming level, which is a value between 0 and 1, where "1" corresponds to the lowest dimming level in the brightest state and "0" corresponds to the highest dimming level in the off state.

[0062] The luminance ratio Lk of the maximum luminance of the first channel with the highest color temperature to the luminance of the kth channel is represented by the following formula 2.

[0063] [Formula 2]

[0064] L k =y k *L total

[0065] Among them, L total It is a value between 0 and 1, which is a value that normalizes the total system brightness relative to the maximum system brightness depending on the dimming level. "1" indicates that the total system brightness is equal to the maximum system brightness, and "0" indicates that the total brightness is 0 and the system is off.

[0066] At this time, due to the total system brightness L total For x m Therefore, the brightness ratio L of the k-th channel to the maximum brightness of the first channel is... k It is represented by the following numerical expression 3.

[0067] [Formula 3]

[0068] L k = [-(N-1)x+(N-k+1)]*x m =-(N-1)*x (m+1) +(N-k+1)*x m

[0069] The point with the highest brightness in the k-th LED channel within the above interval is L. k The point where the differential value becomes 0. Differentiating equation 3, we obtain equation 4 below.

[0070] [Formula 4]

[0071] L k = -(m+1)(N-1)x m +m(N-k+1)x (m-1)

[0072] Through L in logarithmic expression 4 k Substituting 0, find the point x that maximizes the brightness of the k-th LED channel. max It is represented by the following numerical expression 5.

[0073] [Formula 5]

[0074] x max= m*(N-k+1) / [(m+1)(N-1)]

[0075] Therefore, if the value of x in logarithmic expression 3 is substituted into the value of x in numerical expression 5... max Then the maximum brightness L of the k-th LED channel k_max It is represented by the following expression, 6.

[0076] [Formula 6]

[0077] L k_ma x=[-m(N-k+1) / (m+1)+m(N-k+1)]*[m(N-k+1) / [(m+1)(N-1)]] m

[0078] For example, in a system consisting of three LED channels (N=3), the maximum brightness L depends on the dimming level of the second channel (k=2). 2_max It decreases as the polynomial order m increases; for example, when m is 1, L 2_max It becomes 0.500; when m is 2, L 2_max It becomes 0.296; when m is 3, L 2_max It becomes 0.211; when m is 4, L 2_max It becomes 0.164; when m is 5, L 2_max The value becomes 0.134. That is, as the brightness change of the system, which depends on the dimming level, becomes non-linear, the maximum brightness required for the second and subsequent channels decreases. Since the human eye responds logarithmically to brightness changes, the brightness change of the lighting system must increase exponentially inversely to the brightness change so that the human eye perceives a linear increase in brightness. Therefore, it is preferable that the brightness change of the lighting system increases non-linearly.

[0079] Therefore, it is preferable that the maximum brightness of the k-th LED channel is less than the maximum brightness of the first-order polynomial with m=1. Substituting m=1 into equation 6, the maximum brightness L of the k-th LED channel... k_max It is obtained from the following formula 7.

[0080] [Formula 7]

[0081] L k_max = (N-k+1) 2 / (4*(N-1))

[0082] Where 1 < k <= N.

[0083] Therefore, according to an embodiment of the present invention, the ratio of the maximum brightness of the k-th LED channel to the maximum brightness of the LED channel with the highest color temperature among the N LED channels can be set to be less than the value calculated by the following formula:

[0084] (N-k+1) 2 / (4*(N-1))(where 1<k<=N).

[0085] The LED lighting system of an embodiment of the present invention includes three LED channels that emit light of three different color temperatures. In this case, the highest color temperature can be a value between 10,000K and 4,000K, the intermediate color temperature can be a value between 3,500K and 2,500K, and the lowest color temperature can be a value between 2,500K and 1,000K. Furthermore, the three lights with different color temperatures can be light within a 10th-order McAdam ellipse located at coordinates on the blackbody locus on a chromaticity diagram. Using three LED channels, each with one of these three color temperatures, light is created by mixing light with the highest color temperature (between 10,000K and 4,000K) and light with the second highest color temperature (between 3,500K and 2,500K) in the low-brightness range corresponding to relatively high brightness levels. Similarly, light with a color temperature between 3,500K and 2,500K and light with the lowest color temperature (between 2,500K and 1,000K) is mixed in the high-brightness range corresponding to relatively low brightness levels. Because dimming is performed sequentially using LED channels with consecutive color temperatures from three different LED channels, colors that similarly follow a blackbody trajectory on a chromaticity diagram can be represented.

[0086] More specifically, general lighting products using conventional tunable white LEDs are configured to independently change brightness and color temperature within a range of 6,500K to 2,700K, in which case, along the connection... Figure 2 The chroma diagram shown uses straight lines on the blackbody locus corresponding to coordinates at 6,500K and 2,700K to represent colors. Since the lines do not deviate significantly from the blackbody locus, a similar color representation following the blackbody locus is possible. However, if the range is expanded to below 2,500K to further broaden the color temperature representation range, such as... Figure 2 As shown, because the blackbody trajectory curves significantly near 2,500K, it is impossible to perform a similar color representation that follows the blackbody trajectory. For example, as... Figure 13As shown, if light at coordinate 601 (approximately 6,500 K) and coordinate 602 (approximately 2,050 K) on a chromaticity diagram corresponding to a blackbody locus 301 are mixed in a conventionally known manner, a mixed light with coordinates on a straight line 603 connecting the two coordinates 601 and 602 is obtained. In this case, a significant portion of the coordinates on the straight line 603 deviates considerably from the blackbody locus, and some 10th-order McAdam ellipses at coordinate 604 deviate from the blackbody locus, making it impossible to perform a similar color representation following the blackbody locus. As another example of the prior art, there is a dimming technique that expresses color by mixing three different colors of light, such as green, blue, and red, along a desired trajectory on a chromaticity diagram. In this technique, color can be expressed over the entire area of ​​the triangle connecting the coordinates of the three lights on the chromaticity diagram, thus allowing for precise color representation along the blackbody locus if necessary. However, this technique suffers from complexity in control and significantly increases the manufacturing cost of the lighting system, as the brightness and color temperature of the dimming are not controlled in a linked manner. This invention solves these problems and provides a method for achieving color expression that similarly follows a blackbody trajectory while realizing a wide range of color temperature representation. Furthermore, the LED lighting system of embodiments of this invention uses three or more LED channels with different color temperatures, and uses two LED channels with adjacent color temperatures for each interval, thereby enabling color expression over a wide color temperature range while similarly following a blackbody trajectory. For example, in embodiments of this invention, such as... Figure 12 As shown, light is used at coordinate 501 (approximately 6,500 K), corresponding to the blackbody locus 301 on the chromaticity diagram; light at coordinate 502 (approximately 3,000 K); and light at coordinate 503 (approximately 1,750 K). In the relatively bright dimming range, the two types of light corresponding to coordinates 501 and 502, which have relatively high color temperatures, are mixed. In the relatively dark dimming range, the two types of light corresponding to coordinates 502 and 503, which have relatively low color temperatures, are mixed. Thus, color expression can be achieved by similarly following the two straight lines 504 and 505 of the blackbody locus 301 over a wide color temperature range. Figure 2 In the chromaticity diagram shown, the background representing color temperature is displayed in black and white, but it can be understood that it has the same color temperature distribution as commonly used chromaticity diagrams.

[0087] The following describes an embodiment comprising three LED channels that emit light of three different color temperatures. As specific examples, two embodiments using three LED channels that generate light of different color temperatures will be described: an embodiment using three white LED channels that generate white light of different color temperatures, and an embodiment using two white LED channels that generate white light of different color temperatures and one amber LED channel that generates amber light. Table 1 and... Figures 2 to 6 Table 2 and [other documents] are used to explain the embodiment using three white LED channels. Figures 7 to 11 These are examples used to explain embodiments using two white LED channels and one amber LED channel. These two examples are exemplary examples used to explain embodiments of the invention; the number of LED channels, the color temperature of the generated light, etc., can be varied.

[0088] Example 1: White 6,500K – White 3,000K – White 2,000K

[0089] Use LED channels that generate white light with a color temperature of 6,500K (Kelvin), LED channels that generate white light with a color temperature of 3,000K, and LED channels that generate white light with a color temperature of 2,000K. Each LED channel may include more than one LED that generates white light of the corresponding color temperature.

[0090] exist Figure 2 The diagram shows the coordinates (xy scale) 101 of the 6,500K white light, the coordinates 102 of the 3,000K white light, and the coordinates 103 of the 2,000K white light generated by each of the three LED channels, displayed on a CIE (International Commission on Illumination) colorimetric chart, and further shows the blackbody trajectory 301. As shown, the three white lights used are white lights with coordinates on the blackbody trajectory 301.

[0091] When there are three LED channels emitting light with different color temperatures, that is, when N=3, the dimming is divided into N-1, or two control zones. In the relatively bright control zone with a low dimming level, two LED channels that generate two adjacent high color temperature lights, namely 6,500K white light and 3,000K white light, are used to generate mixed light. In the relatively dark control zone that becomes darker as the dimming level increases, two adjacent low color temperature lights, namely 3,000K white light and 2,000K white light, are used to generate mixed light.

[0092] Figure 3 The diagram shows the coordinate trajectory 111 of light obtained by mixing 6,500K white light and 3,000K white light in a first control zone with relatively high brightness, and shows a coordinate 112 of trajectory 111 as an example. At this point, the coordinate trajectory 111 of the light obtained by mixing 6,500K white light and 3,000K white light coincides with the straight line connecting coordinate 101 of the 6,500K white light and coordinate 102 of the 3,000K white light. Figure 3The ellipse indicated by reference numeral 113 in the figure represents a 10th-order McAdam ellipse at coordinate 112 of the mixed light. In an embodiment of the invention, the mixed light obtained by mixing light generated by LED channels of adjacent color temperatures is configured to lie within a 10th-order McAdam ellipse at coordinates on the blackbody trajectory on the chromaticity diagram. This can be interpreted as equivalent to a 10th-order McAdam ellipse at any coordinate on the trajectory 111 of the mixed light including at least a portion of the blackbody trajectory 301.

[0093] Figure 4 The coordinate trajectory 121 of the light obtained by mixing 3,000K white light and 2,000K white light in the second control range with relatively low brightness is shown, and a coordinate 122 of the trajectory 121 is shown as an example. At this time, the coordinate trajectory 121 of the light obtained by mixing 3,000K white light and 2,000K white light coincides with the straight line connecting the coordinates 102 of the 3,000K white light and the coordinates 103 of the 2,000K white light. Figure 4 The ellipse shown as reference numeral 123 in the attached figure represents the 10th-order McAdam ellipse at coordinate 122 of the mixed light. Similar to the first control region, in the second control region, the mixed light obtained by mixing light generated from LED channels of adjacent color temperatures lies within the 10th-order McAdam ellipse located at coordinates on the blackbody locus on the chromaticity diagram. This can be interpreted as equivalent to... Figure 4 The 10th-order McAdam ellipse at any coordinate on the coordinate trajectory 121 of the mixed light includes at least a portion of the blackbody trajectory 301.

[0094] The mixed light obtained by mixing light of adjacent color temperatures is located within the 10th order McAdam ellipse at the coordinates on the blackbody trajectory, so that the mixed light approximately resembling the blackbody trajectory can be maintained during dimming.

[0095] Table 1 exemplarily illustrates the luminance of each light source used to achieve a target brightness and target color temperature depending on the dimming level, using 6,500K, 3,000K, and 2,000K white light. In Table 1, the luminance of each white light source is calculated as a value that achieves the target brightness and target color temperature, and is described as a value rounded to two decimal places. The No. of the dimming level is a sequential number for each dimming level, and the % value is obtained by decreasing the dimming level from 100% to 0% by the same increment. For example, the target brightness is the sum of the luminances of all lights, the target color temperature can be roughly calculated as a weighted average of the luminances depending on the color temperature of each light, and the luminance of each light source can be determined by values ​​that satisfy these conditions.

[0096] Table 1

[0097]

[0098]

[0099]

[0100] on the other hand, Figure 5 This is a graph showing the percentage of target luminance and target color temperature for each light level in Table 1. Figure 6 This is a graph showing the brightness of each light for each dimming level in Table 1. In Table 1, the target brightness is set to the lowest dimming level, i.e., the maximum brightness in dimming level No. 1, and is set to be off at the highest dimming level, i.e., dimming level No. 21. Figure 5 In this table, the target brightness is expressed as a percentage of the brightness of the corresponding dimming level relative to the maximum brightness. In Table 1, the target color temperature is set as 6,500K, the highest of the three colors used in dimming level No. 1, and as 2,000K, the lowest color temperature used in dimming level No. 21. Figure 6 In this table, target brightness is shown as a percentage of the target color temperature for each dimming level when the color temperature of 6,500K is 100% and the color temperature of 2,000K is 0%. See Table 1. Figure 5 and Figure 6 When using three (N=3) different LED channels to achieve color temperature control, dimming control is performed in two separate (N-1) control intervals, C11 and C12. Figure 5 and Figure 6 In the diagram, the horizontal axis represents the percentage of dimming level. 100% on the far right corresponds to the lowest dimming level at maximum brightness, and 0% corresponds to the highest dimming level when the screen is off. That is, as the dimming level increases, it follows... Figure 5 and Figure 6 The path that moves from the right side to the left side of the horizontal axis.

[0101] First, in the first control range C11, mixed light is generated by mixing 6,500K light with the highest color temperature and 3,000K light with the second highest color temperature. The first control range C11 is the range from 100% to 25% of the dimming level. Within the first control range C11, as the dimming level increases, the brightness of the 6,500K white light with the relatively high color temperature is gradually decreased, while the brightness of the 3,000K white light with the relatively low color temperature is gradually increased, and then decreased again.

[0102] Next, in the second control zone C12, mixed light is generated by mixing 3,000K light with an intermediate color temperature and 2,000K light with the lowest color temperature. The second control zone C12 is the range from 20% to 0% of the dimming level. In this control zone C12, as the dimming level increases, the brightness of the relatively high color temperature 3,000K white light gradually decreases, while the brightness of the relatively low color temperature 2,000K light increases and then decreases. Thus, as the dimming level increases in each control zone C11 and C12, the brightness of the LED channel with the higher color temperature in two adjacent LED channels gradually decreases, while the brightness of the LED channel with the lower color temperature gradually increases and then decreases, thereby... Figure 5 As shown, the percentage of brightness tends to decrease non-linearly as the dimming level increases. If the percentage of brightness is as... Figure 5 As shown, the brightness changes linearly rather than nonlinearly with the dimming level. Therefore, the user perceives the brightness as changing linearly with the dimming level. This is because the human eye is less sensitive to brightness changes in relatively bright conditions but more sensitive in relatively dim conditions. At relatively high dimming levels, the brightness change increases with the dimming level, leading the user to perceive the brightness as changing linearly with the dimming level. Thus, a high-quality lighting system can be provided that provides a linear change in brightness that can be perceived as corresponding to a linear change in dimming level.

[0103] like Figure 5 As shown, by varying the brightness of each light corresponding to changes in the dimming level within two control intervals C11 and C12, the percentage of target brightness can be made to change non-linearly with respect to the dimming level, and the percentage of target color temperature can be made to change linearly with respect to the dimming level. For example, the percentage of target brightness can change non-linearly as a polynomial or exponential function of quadratic or higher relative to the dimming level, and the percentage of target color temperature can change as a linear function. In particular, by making the percentage of target brightness change non-linearly with respect to the dimming level, the brightness change during the dimming process can be visually recognized as a linear change corresponding to a linear change in the dimming level.

[0104] Example 2: White 6,500K – White 2,700K – Amber 1,700K

[0105] The invention employs LED channels that generate white light with a color temperature of 6,500 K (Kelvin), LED channels that generate white light with a color temperature of 2,700 K, and LED channels that generate amber light with a color temperature of 1,700 K. Each LED channel may include one or more LEDs that generate white light or amber light of the corresponding color temperature. Descriptions that are repeated in Example 1 above are omitted. In another embodiment of the invention, red light may be used instead of amber light.

[0106] Figure 7 The coordinates 201 of the 6,500K white light, 102 of the 2,700K white light, and 203 of the 1,700K white light generated by the three LED channels are shown on a chromaticity diagram on a CIE colorimetric chart, and the blackbody locus 301 is further shown. As shown, the two white lights used are those with coordinates on the blackbody locus 301, while the coordinates of the amber light are located within a 10th-order McAdam ellipse at the coordinates on the blackbody locus 301.

[0107] As in Example 1, dimming control is performed in two separate control zones. In the relatively bright control zone with a low dimming level, two LED channels that generate two adjacent high color temperature lights, namely 6,500K white light and 2,700K white light, are used to generate mixed light. In the relatively dark control zone that becomes darker as the dimming level increases, two LED channels that generate two adjacent low color temperature lights, namely 2,700K white light and 1,700K amber light, are used to generate mixed light.

[0108] Figure 8 The coordinate trajectory 211 of the light obtained by mixing 6,500K white light and 2,700K white light in a relatively bright first control area is shown, and a coordinate 212 of the trajectory 211 is shown as an example. At this time, the trajectory 211 of the light obtained by mixing 6,500K white light and 2,700K white light coincides with the straight line connecting the coordinates 201 of the 6,500K white light and the coordinates 202 of the 2,700K white light. Figure 8 The ellipse indicated by reference numeral 213 in the attached figure represents the 10th-order McAdam ellipse of the mixed light at coordinate 212. In embodiments of the invention, the mixed light obtained by mixing light generated from LED channels of adjacent color temperatures is configured to lie within the 10th-order McAdam ellipse at coordinates on the blackbody locus on the chromaticity diagram, which can be interpreted as equivalent to... Figure 8 The 10th-order McAdam ellipse at any coordinate on the coordinate trajectory 211 of the mixed light includes at least a portion of the blackbody trajectory 301.

[0109] on the other hand, Figure 9 The coordinate trajectory 221 of light obtained by mixing 2,700K white light and 1,700K amber light in a relatively dark second control zone is shown, and a coordinate 222 of trajectory 221 is shown as an example. At this time, the coordinate trajectory 221 of light obtained by mixing 2,700K white light and 1,700K amber light coincides with the straight line connecting the coordinates 202 of 2,700K white light and the coordinates 203 of 1,700K amber light. Figure 9The ellipse shown as reference numeral 223 in the attached figure represents the 10th-order McAdam ellipse of the mixed light at coordinate 222. Similar to the first control region, in the second control region, the mixed light obtained by mixing light generated from LED channels of adjacent color temperatures lies within the 10th-order McAdam ellipse at coordinate 222 on the blackbody locus on the chromaticity diagram. This can be understood as equivalent to... Figure 9 The 10th-order McAdam ellipse at any coordinate on the coordinate trajectory 221 of the mixed light includes at least a portion of the blackbody trajectory 301.

[0110] The mixed light obtained by mixing light of adjacent color temperatures is located within the 10th order McAdam ellipse at the coordinates on the blackbody trajectory, so that the mixed light approximately resembling the blackbody trajectory can be maintained during dimming.

[0111] Table 2 exemplarily illustrates the luminance of each light source used to achieve the target brightness and target color temperature corresponding to the dimming level using 6,500K white light, 2,700K white light, and 1,700K amber light. In Table 2, the luminance of each light source is calculated as a value that achieves the target brightness and target color temperature, and is described as a value rounded to two decimal places.

[0112] Table 2

[0113]

[0114]

[0115]

[0116] on the other hand, Figure 10 This is a graph showing the percentage of target brightness and target color temperature for each dimming level in Table 2. Figure 11 This is a graph showing the brightness of each light for each dimming level in Table 2.

[0117] Refer to Table 2. Figure 10 and Figure 11As in the first example, dimming control is performed in two separate control zones, C21 and C22. First, in the first control zone C21, mixed light is generated by mixing 6,500K light with the highest color temperature and 2,700K light with the second highest color temperature. The first control zone C21 covers the dimming level from 100% to 40%. Within the first control zone C21, as the dimming level increases, the brightness of the relatively high color temperature 6,500K white light gradually decreases, while the brightness of the relatively low color temperature 2,700K white light gradually increases and then decreases. Next, in the second control zone C22, mixed light is generated by mixing 2,700K light with the intermediate color temperature and 1,700K light with the lowest color temperature. The second control zone C22 covers the dimming level from 35% to 0%. Within this control range C22, as the dimming level increases, the brightness of the 2,700K white light, which has a relatively high color temperature, gradually decreases, while the brightness of the 1,700K amber light, which has a relatively low color temperature, increases and then decreases. By controlling the brightness of each light as described above, the brightness percentage can tend to change linearly rather than non-linearly with respect to the dimming level, allowing the user to perceive that the brightness changes linearly with respect to the dimming level.

[0118] The preferred embodiments of the present invention have been described in detail above, but the scope of the present invention is not limited thereto. Various modifications and improvements made by those skilled in the art using the basic concepts of the present invention as defined in the following claims also fall within the scope of the present invention.

[0119] Industrial availability

[0120] This invention relates to an LED lighting system that is industrially applicable because it can be used in lighting devices.

Claims

1. An LED lighting system capable of dimming to reduce the brightness of the output light, the LED lighting system comprising: LED light source, comprising three or more LED channels respectively configured to emit light of different color temperatures; as well as The circuit is configured to electrically drive the three or more LED channels. The circuit is configured to drive the three or more LED channels such that, during dimming when the output light brightness decreases, the brightness and color temperature of the output light obtained from the LED light source decrease together in a coordinated manner. The three or more LED channels include a first LED channel, a second LED channel, and a third LED channel, each configured to emit light of different color temperatures. The first LED channel is configured to emit white light with a first color temperature in the range of 10,000K to 4,000K; the second LED channel is configured to emit white light with a second color temperature lower than the first color temperature; and the third LED channel is configured to emit amber or red light with a third color temperature lower than the second color temperature. The output light is positioned within a 10th-order McAdam ellipse located at coordinates on the blackbody trajectory on the chromaticity diagram.

2. The LED lighting system according to claim 1, wherein, The circuit operates to generate output light that depends on the dimming level by driving the remaining LED channels, excluding at least one of the three or more LED channels, at all dimming levels corresponding to the dimming function.

3. The LED lighting system according to claim 1, wherein, The circuit is configured to drive the three or more LED channels by dividing them into a number of dimming control intervals that are one less than the number of the three or more LED channels. The circuit is configured to achieve the brightness and color temperature of the output light, which depend on the dimming level, by selectively using one LED channel from a combination of two LED channels selected from the three or more LED channels in each dimming control interval.

4. The LED lighting system according to claim 3, wherein, The combination of the two LED channels is composed of two LED channels with adjacent color temperatures from the three or more LED channels.

5. The LED lighting system according to claim 3 or 4, wherein, The circuit is configured to drive one or more LED channels of a selected LED combination at each dimming level to achieve the brightness and color temperature of the output light depending on the dimming level.

6. The LED lighting system according to claim 1, wherein, Each LED channel emits light within a 10th-order McAdam ellipse located at coordinates on the blackbody trajectory on the chromaticity diagram.

7. The LED lighting system according to claim 1, wherein, The first LED channel has a spectrum with a maximum relative luminous intensity of 60% or more in the 380 to 500 nm wavelength band, and the third LED channel has a spectrum with a maximum relative luminous intensity of 30% or less in the 380 to 500 nm wavelength band.

8. The LED lighting system according to claim 1, further comprising: A control interface is configured to receive the desired dimming level from the user and output a dimming signal corresponding to the input dimming level to the circuit.

9. The LED lighting system according to claim 1, wherein, The circuit is configured to implement a timer function, wherein when the timer function is activated, the circuit is configured to control the LED channel with the lowest color temperature to automatically dim the emitted light for a predetermined time and then turn it off, or to control the LED channel with the lowest color temperature and the LED channel with the second lowest color temperature to automatically dim the output light as the color temperature decreases for a predetermined time and then turn it off.

10. The LED lighting system according to claim 1, wherein, The ratio of the maximum brightness of the kth LED channel in descending order of color temperature among the three or more LED channels to the maximum brightness of the LED channel emitting the highest color temperature light among the three or more LED channels is less than (N-k+1). 2 The value calculated by / (4*(N-1)) where N is the number of LED channels included in the LED light source, 1 <k<=N。 11. The LED lighting system according to claim 1, wherein, The circuit control selectively uses one of the LED channels from the first to the third LED channels to achieve the desired brightness and color temperature based on the brightness of the output light corresponding to the dimming level.

12. The LED lighting system according to claim 1, wherein, The first color temperature is 10,000K to 4,000K, the second color temperature is 3,500K to 2,500K, and the third color temperature is 2,500K to 1,000K.

13. The LED lighting system according to claim 1, wherein, During dimming with reduced brightness, dimming control is performed for multiple separate control intervals based on the brightness of the output light, wherein in the control interval where the brightness of the output light is relatively maximum, the percentage of color temperature decreases approximately linearly relative to the percentage of dimming level with a slope of 1 or greater than 1.

14. The LED lighting system according to claim 1, wherein, During dimming with reduced brightness, dimming control is performed for multiple separate control intervals based on the brightness of the output light, and the percentage of color temperature decreases approximately linearly relative to the percentage of dimming level, wherein in a first control interval where the brightness of the output light is relatively maximum, the slope of the linear change of the percentage of color temperature relative to the percentage of dimming level is equal to or greater than the slope of the linear change of the percentage of color temperature relative to the percentage of dimming level in a second control interval, in which the brightness of the output light is lower than that in the first control interval.

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