WO2010122013A1 - Method and lighting system for operating a multichannel led module - Google Patents

Abstract

The invention relates to a method and a lighting system designed therefor for controlling a multichannel LED module (3), wherein the light radiated by the multichannel LED module (3) is set to a predetermined color by independently activating the individual channels (5) and the actually radiated light color (11) is fed back for control purposes. A rough control, in which only the channels of a subgroup, in particular two channels, are adjusted independently of each other, occurs in a first step until the overall radiated light color lies within a specified tolerance range. A fine control, in which all channels are adjusted, occurs in a second step.

Description

 Method and lighting system for operating a wide-channel LED module

The invention relates to a method and exn designed for lighting system for operating a multi-channel LED module.

Such methods and dedicated lighting systems are used to control multi-channel LED modules. These are in particular modules with differently colored LEDs such as RGBW (red-green-blue-white) and RGBA (red-green-blue-amber) modules. Due to the different colors, especially red-green-blue, different shades can be achieved by mixing. For this purpose, the channels can be controlled individually.

US 6 552 495 B1 shows a control system and method for generating a desired light through a plurality of red, green and blue LEDs. This includes a color sensor that measures the generated light color in a first coordinate system, ie in RGB. The signal is transformed by a module into another color coordinate system, which is an xLy coordinate system. A second module converts a reference color specified in XYZ coordinates also into xLy coordinates. An adder now calculates the difference between the measurement and the reference and passes the result to a controller that uses a driver to control the LEDs so that the difference is compensated. The controller is preferably a PI (Proportional Integration) controller. US 2008/01 69770 A1 shows a method and system for translating a three-component color signal, preferably given in a CIE scale, to a color signal formed from n primary colors, where n is an integer with n greater than or equal to 4. In this case, a CIE standard color chart is used, which consists of 2 color dimensions, which represents 2 of the 3 components of the color signal. The n primary colors are formed by n LEDs with different wavelengths.

These are entered in the procedure on the CIE standard table as points Pl to Pn. Subsequently, at least one point P0 is formed by linear combination of the points P1 to Pn, which is preferably at or in the vicinity of the blackbody curve. Since the point PO is between the points Pl to Pn, triangles can now be formed, each triangle consisting of lines between PO and two adjacent points from Pl to Pn. Subsequently, the color signal is entered as point Px and determined by a control unit, in which triangle it is located. It follows, which two points from Pl to Pn next to PO are closest to Px. By means of these three points can now be determined by the control unit, a linear combination whose solution corresponds to the point Px. Thereafter, the optimal linear combination for PO is chosen by the control unit to achieve a maximum CRI value and a maximum luminous efficiency, whereby different linear combinations are available in a memory. Finally, before operating the LEDs with the determined parameters, the brightness of the linear combination of the 3 points must be adjusted so that it corresponds to the third component of the color signal. Although the prior art has shown methods and systems for adapting RGB LEDs to an x, y target color according to the ICC standard color chart, this adaptation requires rather complex calculations. Accordingly, expensive computing units, such as Cordic processors, DSPs (digital signal processors) or ASICs, etc., are required. In particular, the computing unit must be able to compute complex mathematical algorithms. In addition, this increases the computing time and thus the time of the adaptation of the lighting to the target.

It is the object of the invention to provide a method and a lighting system designed for this, which requires only a small amount of computation for the adaptation of the lighting properties to a target specification.

This object is achieved by the characterizing features of the independent claims. Particularly advantageous embodiments of the invention are described in the subclaims.

The present invention deals with a method of controlling a multi-channel LED module wherein the light emitted from the multi-channel LED module is adjusted to a predetermined color by independently driving the individual channels and the actual emitted light color is returned for control purposes. In a first step, a coarse regulation takes place in which only the channels of a subgroup, in particular two channels, are adjusted independently of each other until the total radiated light color lies within a predetermined tolerance range. In a second step, a fine-tuning takes place in which all channels are adapted. Another aspect of the present invention relates to a method of controlling a multi-channel LED module wherein the light emitted from the multi-channel LED module is adjusted to a predetermined color by independently driving the individual channels and the actual emitted light color is returned for regulatory purposes. The setting of the predetermined color at the beginning is done exclusively by the independent adaptation of individual channels of a subgroup. Each channel of the subgroup is adjusted independently of the others until the parameters set with it exceed a permitted maximum value or fall below a permitted minimum value. Instead of the channel with the unauthorized high or low parameter values, other non-subgroup channels are adapted for control.

Erfmdungsgemaß the predetermined color is preferably given m x, y coordinates in an ICC standard color chart.

The multi-channel LED module may be a four-channel LED module, in particular an RGBW (red-green-blue-white) or RGBA (red-green-blue-amber) LED module. At least one LED is connected to each channel.

The white channel can be realized by an RGB module. Alternatively, however, it can also be realized by at least one blue LED, wherein in the emission region of the blue LED is a wavelength conversion means which converts at least the wavelength of a part of the leaked radiation into another wavelength.

The Amber channel is preferably a white channel in which an amber color supplement is added at the exit angle of the light of the connected LED's / LEDs. The individual channels can be controlled via PWM (Pulse Width Modulation). This results in the advantage that no control by the drive current is necessary. Therefore, the driving current can be set to a constant value.

Another advantageous aspect of the invention is the fact that the adjustment of the emitted light of the multi-channel LED module to the predetermined color can be done exclusively by bit comparisons.

According to the invention, the light color attributed to control purposes can be given in RGB coordinates.

The RGB coordinates of the recirculated light color can be transformed into x, y coordinates of the ICC standard color chart and a parameter for the brightness for comparison with the predetermined color.

The coarse regulation preferably takes place via a subgroup of the channels, it being possible for the subgroup to be the red and the green channel.

The predetermined tolerance range, which represents the threshold between the coarse and the fine control, is preferably a multiple of an allowable error value.

In a preferred embodiment, the fine control takes place until the emitted light corresponds as far as the predetermined color that the error, so the deviation is not greater than the allowable error value.

Control of the blue and white / amber channels can then be done when the set PWM duty cycles of the red and green Channels are above an allowable maximum value or below an allowable minimum value.

The invention also relates to a lighting system comprising a multi-channel LED module, a control unit and a sensor device. The control unit sets the light emitted by the multi-channel LED module light to a predetermined color by independently controlling the individual channels. The sensor device returns the actually emitted light color to the control unit. In a first step, a coarse regulation takes place, in which only the channels of a subgroup, in particular two channels, are adapted independently of each other until the total radiated light color lies within a predetermined tolerance range. In a second step, a fine adjustment takes place, in which all channels are adapted.

Finally, the invention also relates to a lighting system comprising a multi-channel LED module, a control unit and a sensor device. The control unit sets the light emitted by the multi-channel LED module light to a predetermined color by independently controlling the individual channels. The sensor device returns the actually emitted light color to the control unit. The setting of the predetermined color is initially performed solely by independently adjusting individual channels of a subgroup. Each channel of the subgroup is adjusted independently of the others until the parameters set with it exceed a permitted maximum value or fall below a permitted minimum value. Instead of the channel with the unauthorized high or low parameter values, other non-subgroup channels are adapted for control. Preferably, the lighting system has a memory.

The rule may be designed to only perform bit comparisons.

The sensor device may be an RGB color sensor.

The invention will be explained in more detail with reference to the accompanying drawings. Show it:

Fig. 1 is a simplified representation of the erfmdungsgemaßen method using an ICC standard color chart

Fig. 2 is a vector diagram that the

Regulatory possibilities by varying the luminous intensity of the individual LEDs reflects

Fig. 3 shows a preferred embodiment of a flowchart of the inventive method

4 shows a schematic exemplary embodiment of the illumination system according to the invention

The invention will be explained with reference to an exemplary embodiment of a Betriebsgerates. In Fig. 1 is a simplified representation of the erfmdungsgemaßen method is shown. The procedure is explained using an ICC standard color chart.

The ICC standard color chart is rendered in x-y coordinates. In essence, a color space is shown that has the shape of a triangle. In this triangle are all human-visible colors defined by an X, Y, Z space. Due to better visualization, this 3-dimensional X, Y, Z space was limited to a 2-dimensional x, y space. This is made possible by omitting the parameter for brightness. This means that the ICC standard color chart from Fig.l does not indicate brightness differences. This parameter should therefore be considered separately. Only a color intensity is given, with the border representing the "pure" colors with the highest saturation. Within the triangle are mixed colors.

On the Planckian curve, also known as Black Body line, the white points are at different color temperatures. The defined white point E is thereby x = y = z = 0, 3333. Starting from this, the color saturation increases in each direction and reaches its respective maximum at the edge of the triangle.

The edge of the triangle is defined, as already explained, by primary colors that consist exclusively of one wavelength. Some of these are shown in Fig.l. Roughly speaking, at the upper end of the triangle, the color green is at a wavelength of about 520 nm. The right corner is at about 650nm as red defined, bottom left at about 470nm is blue.

If an RGB LED module is now used, the red, green and blue LEDs in this color space create a triangle. By mixing the three colors, any color within that triangle can be created. This is preferably realized by differently strong driving of the LEDs. In this case, a control of the LEDs via the drive current is conceivable. However, a preferred

Control with constant current and a variable PWM

(Pulse Width Modulation) pulse width. By using the three LEDs not only can every color within the

Triangles are generated. It can also be realized as an additional parameter each different brightness level.

By adding a fourth color, such as white or amber, a further refinement of the Emstellungsmoglichkeiten can be achieved. When adding the amber LED even the producible color space can be increased, since now the color space that can be generated is no longer spanned by a triangle, but by a quadrilateral.

Em channel controls a certain color, whereby more than one LED can be connected to one channel. This means that, for example, several blue LEDs can be connected to the blue channel. In addition, it is also conceivable that additional channels can be realized. This can be achieved by connecting different colored LEDs to one channel. For example, let yourself be Achieve magenta channel by connecting at least one blue and at least one red LED.

A mixture of the individual luminous colors is achieved by suitable means, preferably by a mixing disk.

In the example shown in FIG. 1, a light color corresponding to a color at point A is initially generated by a four-channel RGBA LED module.

The predetermined target color corresponds to that at point C.

According to the invention, a coarse regulation is therefore first carried out until the emitted light color lies within a certain tolerance range. This is represented here by the circle around point C. In this coarse regulation, only red and green are varied. Blue and Amber (amber) remain constant. Here, the advantage is exploited that a variation of green roughly corresponds to a change of the total emitted light in the y-direction. By contrast, a variation of red roughly corresponds to a change in the total emitted light in the x direction. This means that by independent rules of red and green independent dimensions in the color space are varied.

A further clarification for this shows the

Vector diagram of Fig.2. It is by a

Reinforcement of the green LED or the green channel, one

Shift achieved in the y-direction. A reinforcement of By contrast, red LED means a shift in the x direction. By amplifying the blue LED, a shift roughly towards the origin is achieved. A gain of the amber LED is a shift against that of a gain of the blue LED, with the blue portion of the y being less.

Thus, a coarse regulation is now carried out in Fig.l only by changing the red and the blue channel. In this case, a rapid change in the total emitted light color is achieved in that the change in the luminous intensity of an LED has a greater step size.

According to the invention, it is also taken into account whether a channel has exceeded or fallen below a maximum or minimum permissible limit value. If this is the case, a further control by means of the blue and / or the white channel instead of the channel with unauthorized high or low control parameters is performed. Further explanations on this can be found in the description of FIG.

The coarse control is then replaced by a fine control when the total generated light color has arrived at point B, following the white arrow, which is on the circle around the target point C. In the fine control, a smaller step size is used to change. In addition, now to approximate the target point C all channels are varied independently. An approximation can now be achieved by shifting in four different directions, the four directions are shown in Figure 2. The regulation is then terminated when the shortcut is not greater than a legal error value.

In addition, it is also possible to adjust the brightness to a predetermined value.

Fig. 3 shows a preferred embodiment of a flowchart of the inventive method.

In step A, an initialization takes place. Here the essential parameters of the erfmdungsgemaßen method are set. The step by step adjustment is set to coarse (fastStep). This means that a coarse regulation takes place at least in the first pass of the flowchart.

In step B it is checked whether a further adaptation is necessary. In this case, it is determined whether the inaccuracy of the actual value (x, y) to the target value (Targetx, Targety) is within an allowable error value (error). If this is the case, then the process is completed.

If, in step C, all four channels (RGBW) are less than half of the maximum allowable PWM value, then it is determined for each channel if the channel is off.

If the respective channel is not off, the PWM pulse width of this channel is increased by 50% of the maximum permissible PWM pulse width. However, if the channel is off, the next channel is checked. In step D1, the channels are set with the respective PWM pulse widths.

Then the RGB actual values are measured in D2 by means of the color sensor.

In D3, the RGB actual values are transformed into (X, Y, Z) coordinates. These are then converted into x, y, z coordinates. This results in the x-actual (x) and y-actual (y) values.

In step E, an adjustment of the actual x value is performed by changing the red channel and the y actual value by changing the green channel.

In this case, first x-actual (x) is compared with x-target (targetx) in El. If X-Is is too small, red in E2 is increased by a fastStep.

Now it is checked in E3 whether an x, y actual value has already been reached within a specified tolerance range. The specified tolerance range is a multiple K of the permitted error value "error".

If this is the case, then a fine control is switched for red. This is achieved in D4 by switching from fastStep to fineStep.

It is also conceivable that the method has more than two control levels. This means that there is not only a coarse and a fine control. For this purpose, K can represent a variable which becomes smaller as the actual value approaches the setpoint as the actual value increases. This reduction of K is done each time a new approach has been reached. When reaching a new approximation level, of course, the change increment of a color is reduced to a smaller one.

In steps Ell to E15, an analogous procedure is carried out in the event that the actual x value is too large.

In steps E21 to E35, a procedure analogous to E1 to E15 is carried out for a comparison between the actual y value and the y setpoint with corresponding adaptation of green.

In steps F to I is now checked whether the PWM pulse width of the red and / or the green channel xn is an illicit high or low range. If this is the case, then the blue instead of the red one, or the white and the blue channel instead of the green channel, is regulated.

In step F, it is thus checked whether the pulse width set with red lies above a maximally permitted value. If this is the case, the X actual value and the Y actual value are adjusted by adjusting the blue channel.

If m Fl is the PWM pulse width of red above a maximum permissible value, this is set to the maximum permissible value. Now, a comparison of the actual value of the x and the actual value of the y, which proceeds analogously to E1 to E35, follows whether these values are below or above the desired values. However, not the red or the green channel is adjusted, but the blue channel. Again, there is a decision as to whether the pace should be set from blue to faststep or finestep. This decision is made again depending on whether the x actual value and y actual value are within a K fold of the tolerance range "error".

In step G it is checked whether red is below a minimum allowed value UL. If this is the case, an adjustment of the x actual value and the y

Actual value made by adjusting the blue channel.

If, in step Gl, the PWM pulse width of red is below the UL

Value, then in step G2 the step speed of red is set to 1.

If the PWM pulse width of Red is less than 1, then it is set to the value 0 in G4. Again, a comparison of x-actual and y-actual analogous to FIl to F45 follows, whether these values are below or above the nominal values. In each case, the blue channel is adjusted again.

Again, there is a decision as to whether the pace should be set from blue to faststep or finestep. This decision is made again depending on whether the x-actual and y-actual value is within a K-fold of the tolerance range "error".

In step H it is checked whether the pulse width of green is above a maximum permissible pulse width. If this is the case, then the actual x value and the y actual value are changed by changing the pulse width of blue and white customized. It is determined in H1 whether the PWM pulse width of green is above the maximum permissible PWM value. If this is the case, the value in H2 is set to the maximum permissible PWM value. Again, an adaptation to the type described in steps FIl to F45 is made, now not only blue is adjusted, but blue and white together. It should be noted that if the actual x-value is too small, blue and white in H11-H15 are reduced by one increment and increased by one increment if the actual x-value in H21-H25 is too large.

When comparing the y actual value with the y setpoint, however, if the actual y value is too small, the step size of the blue channel in H31-H35 is reduced by one increment and white is increased by one increment. If the y-actual value is too large, on the other hand, blue is increased by one step in H41-H45 and white is reduced by one step.

In step I, it is checked whether the pulse width of the green channel is below a minimum allowed value UL. If this is the case, the x-value and the y-value are adjusted again by adjusting the white and the blue channel.

If the PWM pulse width of green is below the LT value, in step 12 the step speed is set from green to 1. If the PWM pulse width of green is less than 1, this is set to the value 0 in FIG.

Subsequently, matching of blue and white is performed in the manner described in steps H11-H45. In step K, it is determined whether the PWM pulse width of blue is above the maximum allowable PWM value. If this is the case, the value is set to the maximum permissible PWM value. It is then checked in K3 whether the PWM pulse width of green is below the UL value. If this is the case, the step speed of blue is set to 1. If the PWM value of blue is less than 1, then it is set to the value 0.

In step L, the same process described in step K for blue is now performed for white.

In step M is jumped back to the start in step B. This forms a loop and the method can be performed until a given error value is not exceeded.

4, a schematic embodiment of the illumination system according to the invention is shown.

The lighting system 1 has a control unit 2. This in turn can consist of a low-cost processor, since thanks to the method according to the invention only simple bit comparisons must be made. Of course, however, higher-quality processors such as Cordic processors or other types such as digital signal processors, or ASICs can be used.

The control unit 2 is connected via a bus 6 with an LED module 3. The bus here consists of 4 of independent channels 5, each channel regulating a luminous color.

The LED module is embodied here as an element which comprises four differently colored LEDs 4. These can be red, green, blue and white. Alternatively or in addition to the white LED, however, an amber LED can be used. In addition, it is conceivable to use several instead of one LED of one color, which are connected to the same channel 5. The white channel can be realized by a separate RGB module. Alternatively, however, it can also be realized by at least one blue LED, wherein in the emission region of the blue LED is a wavelength conversion means which converts at least the wavelength of a part of the leaked radiation into another wavelength.

If an amber channel is to be used, this is preferably a white channel m of the embodiment described above, in which an amber additive is added at the exit angle of the light of the one or more LEDs.

The emitted light from the LED module 11 is mixed by suitable means, for example by a lens so that a uniform luminous color is formed.

It can be connected to the bus 6 and several LED modules.

The invention is also not limited to LEDs. It can be used in place of any other type of colored lights. A sensor device 7 is connected to the control unit 2. This is an RGB color sensor. It measures the light 11 emitted by at least one LED module. Thanks to the three independent measuring sizes, all the colors that can be generated by combining the three colors can be measured, as well as the brightness. Nevertheless, it is conceivable to connect a further brightness sensor to the Regelemheit, for example, a daylight sensor.

In addition to the adaptation of the luminous color described above, it is therefore also possible to adjust the brightness to a predetermined value.

The three independent measured variables are transmitted via the interface 8 to the control unit for the adaptive control of the LEDs described above.

The rule unit 10 also has an interface 10. This can be as

User interface be formed. For example, it may be an input device by means of which a user of the rule transmits a color setpoint and possibly a brightness value. With the aid of the color sensor measurement, the luminous color of the LEDs 4 could be adapted to the set value.

However, the interface 10 may also be an interface to a central control unit. The latter may be a programmable timer that cycles through different light patterns at different times of the day. Optionally, the lighting system may include a memory 9. In this example, set color specifications can be stored. Thus, the lighting system can also be programmed for different temporally changing luminous properties.

List of reference numbers:

1 lighting system

2 control unit

3 LED module

4 LED 5 color channel

6 bus

7 color sensor

8 Interface between color sensor and control unit 9 Memory

10 interface

11 emitted light

Claims

Claims : A method of operating a multi-channel LED module (3), wherein the light emitted from the multi-channel LED module (3) is adjusted to a target color coordinate by independently driving the individual channels (5) and the actual emitted light color (11) for regulatory purposes is characterized in that in a first step as long as a coarse regulation takes place, in which only the channels of a subgroup, in particular two channels, are adapted independently of each other until the total radiated light color is within a predetermined tolerance range around a target color coordinate, and in a second step, a fine control, in which all channels are adapted. 2. The method according to claim 1, characterized in that the fine control takes place as long as the emitted light as far as the predetermined color coordinate corresponds, that the error is not greater than a permitted error value. 3. The method according to any one of the preceding claims, characterized in that the predetermined tolerance range, the threshold between the coarse and the fine control is a multiple of the allowed error value. 4. A method for operating a multi-channel LED module (3), wherein the radiated from the multi-channel LED module (3) Light is set to a predetermined color coordinate by independently driving the individual channels (5) and the actually emitted light color (11) is returned for control purposes, characterized in that the setting of the predetermined color coordinate at the beginning takes place exclusively by the independent adaptation of individual channels of a subgroup, - each channel of the subgroup is adapted independently of the others until the parameters set with it exceed a permitted maximum value or fall below a permitted minimum value, and - instead of the channel with the illicit high or low parameter values, other non-subgroup channels are adapted for regulation. 5. Method according to one of the preceding claims, characterized in that the predetermined color coordinate is given in x, y coordinates in an ICC standard color chart. 6. The method according to any one of the preceding claims, characterized in that it is in the multi-channel LED module (3) to a Four-channel LED module, in particular an RGBW (red-green-blue-white) or RGBA (red-green-blue-amber) LED module, with at least one LED connected to each channel. 7. The method according to any one of the preceding claims, characterized in that the white channel is realized by an RGB module or at least one blue LED, wherein in the emission region of the blue LED wavelength conversion means is at least the wavelength of a portion of the leaked radiation in converts another wavelength. 8. The method according to any one of the preceding claims, characterized in that the control of the individual channels (5) via PWM, wherein the drive current is preferably set to a constant value. 9. The method according to any one of the preceding claims, characterized in that for adjusting the emitted light (11) of the multi-channel LED module (3) to the predetermined color coordinate only bit comparisons are performed. 10. The method according to any one of the preceding claims, characterized in that the recirculated for regulatory purposes light color (8) is given in RGB coordinates. 11. The method according to any one of the preceding claims, characterized in that the RGB coordinates of the recirculated light color for comparison with the predetermined color in x, y coordinates of the ICC standard color chart and a parameter for the brightness is transformed. 12. The method according to any one of the preceding claims, characterized in that a control of the blue and the white / amber channel takes place when the set PWM duty cycle of the red and green channel are above a maximum allowed value or below an allowable minimum value. 13. The method according to claims 1 and 6, characterized in that the coarse regulation takes place via a subset of the channels, wherein it is the subgroup to the red and the green channel. 14. Lighting system (1) comprising a multi-channel LED module (3), a control unit (2) and a sensor device (7), wherein the control unit (2) emitted by the multi-channel LED module (2) light (11) set to a predetermined color coordinate by independently driving the individual channels (5) and the sensor device (7) the actually emitted light color (11) of the control unit (2) zurückfuhrt characterized in that - In a first step as long as a coarse regulation takes place, in which only the channels a subgroup, in particular two channels, are adapted independently of each other until the total radiated light color is within a predetermined tolerance range, and - in a second step, a fine control takes place, in which all channels are adjusted. 15. lighting system (1) comprising a multi-channel LED module (3), a control unit (2) and a sensor device (7), wherein the control unit (2) emitted by the multi-channel LED module (3) light (11) set to a predetermined color coordinate by independently driving the individual channels (5) and the sensor device (7) the actually emitted light color (11) of the control unit (2) zurückfuhrt characterized in that - The setting of the predetermined color in the beginning exclusively by the independent Customizing individual channels of a subgroup, - Each channel of the subgroup is adapted independently of the others until the parameters set with it allow one Exceed maximum value or below a permitted minimum value and - instead of the channel with the illicit high or low parameter values, other non-subgroup channels are adapted for regulation. 16. Lighting system (1) according to claims 14 and 15, characterized in that the illumination system (1) has a memory (9). 17. Lighting system (1) according to claims 14 and 15, characterized in that the control unit (2) is designed so that it performs only bit comparisons. 18. Illumination system (1) according to claims 14 and 15, characterized in that the sensor device (7) is an RGB color sensor.