WO2009156244A2 - Circuit for dimming a lamp and associated method - Google Patents

Abstract

The invention relates to a circuit for dimming a lamp comprising at least two illumination units. The circuit comprises a control unit for coupling a brightness with a color temperature depending on an input signal, the at least two illumination units being controllable by the control unit depending on the input signal. The invention also relates to a method for dimming a lamp.

Description

description

Circuit for dimming a lamp and associated method

The invention relates to a circuit for dimming a lamp and an associated method.

LED lamps for home lighting will increasingly replace existing incandescent lamps. Although the color temperature of the incandescent bulbs, which is about 2750K, can be perceived as pleasant, LEDs offer special advantages at colder color temperatures of up to 8000K (so-called "sky-white" coloring).

A dimming of LEDs is easily possible electronically, but a change in the color temperature is associated with a high electrical control effort. This effort reduces customer acceptance and increases the price of the lamp.

Existing solutions set a color location of the lamp by means of several single-color LEDs. For example, LED combinations in the form of RGB or RGBW (R: red LED, G: green LED, B: blue LED, W: white LED) are common. Due to the different characteristics of the individual differently colored LEDs, a complicated, expensive and difficult to set the customer (three individual controller) control is needed to choose the color temperature depending on the brightness of the lamp. In addition, a different aging behavior of the different LEDs causes a shift of the color location of the lamp.

The object of the invention is to avoid the above-mentioned disadvantages and in particular to provide a lamp whose color temperature is consistent with a

Reduction of performance (eg in the context of dimming) too warmer color temperatures, similar to a light bulb.

This object is achieved according to the features of the independent claims. Further developments of the invention will become apparent from the dependent claims.

To achieve the object, a circuit for dimming a lamp comprising at least two light units is specified

- With a control unit for coupling a brightness and a color temperature depending on an input signal;

- Wherein, depending on the input signal based on the control unit, the at least two lighting units are controlled.

Here, the dimming of the lamp denotes an adjustment of a lamp parameter, in particular a brightness (brighter or darker) of the lamp. In addition, the dimming can be used to adapt the color locus or the color temperature of the lamp. Thus, with changing the brightness, the color temperature can be adjusted. For example, it is advantageous that as the brightness increases, a higher color temperature (e.g., 8000K) and thus increasingly "cold white" light is set.

The approach presented here allows the brightness and color temperature to be coupled in a channel, i. the adjustment of both parameters can be advantageous by means of the

Input signal done. The implementation

Abstrahlcharakteristika the at least two light units by means of the control unit preferably depends on

(eg in the form of characteristic curves) stored parameter curves for brightness and color temperature. The parameter curves can be at least partially - eg in Reference to the color temperature - individually deposited for each of the lighting units.

In particular, the at least two light units have different color temperatures, so that the color temperature of the lamp is suitably adjustable depending on the brightness, in particular with increasing brightness, a higher color temperature and with decreasing brightness, a lower color temperature is adjustable.

Thus, at a lower brightness, a pleasant color temperature of the lamp ("feel-good light") can be set for the user. Operation is intuitive for the user based on the input signal. In particular, the user of the lamp does not have to worry about additionally setting different color temperatures depending on the brightness of the lamp.

A development consists in that the lighting unit comprises an LED or an LED module.

It can be provided per LED module, a plurality of LEDs in particular also different colored LEDs.

In particular, identical or similar LEDs and / or identical or (very) similar phosphors are used in the luminous units. This makes effective a perceptible aging, i. different changes in color temperatures, counteracted.

A further development is that the at least two light units can be controlled on the basis of the control unit by means of the input signal on the basis of a dimming characteristic curve and on the basis of one characteristic curve for color matching per light unit. In particular, the control unit comprises a microcontroller which can access stored values, for example characteristic curves, and outputs a corresponding brightness value that can be determined by one or more characteristic curves or stored values, depending on the input signal per lighting unit. As a result of the different actuations of the at least two lighting units relative to one another, it is thus achieved that a desired color temperature can be set as a function of the brightness of the lamp (desired by the user).

For example, depending on the input signal, the dimming characteristic curve can provide a first value, by means of which a second value is determined for each lighting unit on the basis of a color temperature characteristic curve specific to the lighting unit. Thus, the first value is processed by means of several color temperature characteristics to a plurality of second values (a separate value for each lighting unit) and these second values are used to control the respective lighting units.

In this case, it should be noted that the control unit can access stored values, which are here designated by way of example as characteristic curves, and can perform an assignment (mapping) to further values on the basis of the stored values. In this respect, the characteristic curves should be understood as preferably stored values which can be used for (further) processing or for controlling the lighting units. Also, the characteristics may be linked to functionally stored values, i. A rule or function can be stored on the basis of which an initial value can be determined for an input value. In this case, the pre-storage of a plurality of values or value pairs can be omitted.

Another development is that the control unit comprises a color controller, the color controller depending on a measured value determined by means of a sensor activates the at least two lighting units.

In particular, processing of the brightness and the color temperature takes place in the color controller. For example, at least one desired value is predetermined by the input signal, and at least one actual value is provided by means of the sensor. The color controller performs a nominal-actual comparison and sets the lighting units so that the actual value largely corresponds to the setpoint. In this respect, the regulation to the desired value can be carried out continuously or time-discretely (i.e., iteratively at certain predeterminable times).

Preferably, the color controller is impressed on the basis of the input signal, a desired brightness or a desired color temperature. This can be done by the control unit in that the input signal is assigned by means of a characteristic curve for color matching a target color temperature and that the input signal is assigned by means of a dimming characteristic of a desired brightness. The sensor can accordingly provide actual values for the color temperature and / or the brightness.

In particular, it is a continuing education that the

Control unit based on the input signal determines the brightness and the color temperature.

It is also a development that the control unit based on the input signal, the brightness and the

Color temperature determined on the basis of characteristics or stored values.

It should be noted that the characteristics are stored as stored values in the control unit, which is preferably designed as a microcontroller with memory. Furthermore, it is a development that drivers are provided for controlling the at least two light units.

In the context of an additional development, a higher color temperature can be set with increasing brightness of the lamp.

A next development is that with decreasing brightness of the lamp, a lower color temperature is adjustable.

One embodiment is that a warm-white lighting unit and a cold-white lighting unit are provided.

For example, one or more light units, in particular LEDs or LED modules, may be provided which have a color temperature between warm white and cold white. One advantage is that the emitted light can be better adapted to a so-called Planck curve. By passing through the color temperature and / or brightness, the emitted light remains closer to the Planck curve and thus looks more natural. Planck's deviating light is usually perceived as colorful.

The above object is also achieved by a method for controlling a lamp comprising at least two light units,

- In which dependent on an input signal, a brightness and a color temperature of the lamp are determined; - Wherein depending on the determined brightness and color temperature, the at least two light units are controlled. An alternative embodiment consists in that the brightness and the color temperature are determined on the basis of at least one characteristic curve, wherein in particular one characteristic is provided per lighting unit for an adaptation of the color temperature.

It should be noted here that the characteristic can refer to any type of stored or cached values and / or functionally determinable values.

A next embodiment is that the input signal is a dimming signal.

The dimming signal is preferably a signal with which a user of the lamp can set the brightness of the lamp.

It is also an embodiment that a color temperature and / or a brightness of the lamp is detected by means of a sensor and that, depending on the detected color temperature and / or the detected brightness, a control of the at least two light units is performed.

Accordingly, a target-actual comparison between color temperature and brightness values predetermined or ascertainable based on the input signal and color temperature and brightness actual values provided by the sensor can be performed. Thus, on the basis of the method described here, a continuous or discrete-time control for setting the at least two lighting units can be carried out in accordance with a desired specification.

Embodiments of the invention are illustrated and explained below with reference to the drawings. Show it :

Fig.l characteristics of a lamp comprising two LEDs in particular color temperatures and

Brightnesses depending on a controller position;

2 characteristic curves in a partial logarithmic scaling for a lamp comprising two LEDs, in particular color temperatures and

Brightnesses depending on a controller position;

3 a dimming without a color management system;

A dimming with a color management system;

FIG. 5 a dimming taking into account a setting of the color temperature without a color management system; FIG.

6 shows a dimming taking into account the setting of the color temperature with a color management system.

For example, it is assumed that two LEDs (LEDl and LED2) are installed together in one lamp. The LEDl is a warm white LED with a color temperature (CCT) of 2000K and LED2 is a cold white LED with a color temperature of 8000K.

The relative efficiency of the warm-white LED compared to the cold-white LED is assumed to be 50% in the following (for example due to efficiency disadvantages of the phosphors used).

A dimmer for home use provides a rule dimension, which is also called controller position in the following. With the regulator position, a proportional control of the emitted light quantity of the lamp are generated. At the same time, the color temperature should be reduced with a reduction in the amount of light. For example, the color temperature drops from 6500K at full light output to 2500K at less than 20% of the light output.

FIG. 1 shows by way of example the following characteristics:

A characteristic curve 101 which determines the emitted light quantity of the warm white LED as a function of the

Regulator position shows;

a characteristic curve 104 which shows the emitted light quantity of the cold-white LED 2 in dependence on the regulator position; a characteristic curve 103 which shows the emitted light quantity of the lamp comprising the LED1 and the LED2 as a function of the regulator position;

a characteristic curve 102 shows the color temperature (CCT) of the lamp as a function of the position of the regulator.

The emitted light quantity 103 is approximately linearly correlated with the regulator position.

An alternative characteristic for a brightness control according to DIN EN 60929 (logarithmic dependence of the brightness of the regulator position) is shown in FIG. 2 hereby comprises the following characteristics:

A characteristic curve 201 which determines the emitted light quantity of the warm-white LED1 as a function of the

Regulator position shows;

a characteristic curve 204 which shows the emitted light quantity of the cold white LED 2 as a function of the regulator position; a characteristic curve 202 which shows the emitted light quantity of the lamp comprising the LED1 and the LED2 as a function of the regulator position; a characteristic curve 203 shows the color temperature (CCT) of the lamp as a function of the position of the regulator.

In Figure 2, the power of the LED or the amount of light was scaled logarithmic. For the color temperature, a linear scale is provided.

The characteristic of the cold white LED2 and the characteristic of the warm white LEDl can be implemented electronically. A compensation of different aging of the individual LEDs can be omitted if identical LED chips are used. The different phosphors used are resistant to aging to a good approximation.

An active monitoring of the color temperature can thus be omitted. The color temperature in the example presented can be set in a range from about 6500K to about 2500K.

In addition to the two characteristics presented other characteristics are possible. In particular, a relationship between amount of light and color temperature can be set in a wide range.

Incandescent lamps can only be operated up to 3200K (halogen). Whether by means of the approach presented here a stronger or a weaker decrease of the color temperature with the amount of light is desired can be specified individually. An appropriate setting or regulation is possible.

It is advantageous here that at full power both LEDs can actually be operated at full power and thus an efficient utilization of the lamp is made possible. It should be noted that a plurality of LEDs can be used. For example, two LEDs are mentioned here. In this case, LED modules can be provided with more than one LED and correspondingly more such modules can be combined. In particular, a plurality of individual LEDs can form a cold white LED module or a warm white LED module. Furthermore, the lamp may comprise at least two LEDs or one or more LED modules.

Depending on the desired control range, different characteristics for the individual LEDs (LED1 or LED2) can be specified in the above example. For low color temperature ranges, it is possible to efficiently use LEDs whose color temperature is not far removed from the actual useful color temperature of the lamp.

switching examples

3 shows a dimming without color management system (CMS:

Color Management System). A dimming signal DIM is received by a microcontroller 301 and converted by means of a stored dimming characteristic 302 (cf., for example, EN 60929: 2004 E.4.3.7). The dimming characteristic 302 is preferably stored logarithmically or in a parabolic form (y = x ² ).

The microcontroller 301 generates signals for driving an LED driver 303 and an LED driver 304. The LED driver 303 controls a warm white LED 305 and the LED driver 304 controls a cold white LED 306.

The LED driver 303 and / or 304 may be designed as a switching regulator, for example as a step-down converter, as a step-up converter, as an inverse converter, as a cuttlefish, as a Cuk, as a flyback converter or as a linear regulator. The average output current of the LED drivers 303, 304 is preferably directly proportional to the input signal provided by the microcontroller 301. An average of the current can be adjusted by a variable current control. Alternatively, it is also possible to switch between different current levels (back and forth). Here, a current level is preferably OA and another current level is I _max .

The time relationship between the two switched current levels (eg OA and I _max ) determines the mean current through the respective LED. This is a pulse width modulation method for adjusting the brightness of the LEDs 305, 306.

The power supply of the microcontroller 301 and the LED driver 303, 304 via a power supply 307th

4 shows a dimming with a color management system. In addition to the description of Fig.3 is here

Microcontroller 401 provided with a color controller 409.

4 shows a driver 403, which drives a red LED 406, a driver 404, which drives a green LED 407, and a driver 405, which drives a blue LED 408. The drivers 403 to 405 and the microcontroller 401 are powered by a power supply unit 411.

The microcontroller 401 comprises a dimming characteristic 402, which is controlled by means of a dimming signal DIM.

Furthermore, a color temperature CCT can be set externally. The dim signal DIM is generated by means of the

Microcontroller converted into a brightness signal BRI and thus the color controller 409 fed. Furthermore, the

Color controller 409 with externally adjustable color temperature

CCT charged. The color controller 409 compensates for LED tolerances, especially when using different LED chip colors. The color controller 409 is combined with a sensor 410, wherein the measured values supplied by the sensor 410 are evaluated by the color controller 409. The sensor 410 is arranged such that the light emitted by the LEDs 406 to 408 can be measured.

The color controller 409 determines an actual light color based on the sensor 410 and determines and compensates for a deviation from the default value CCT. A deviation from the brightness signal BRI is also determined and compensated.

Such a color control system comprising the color controller 409 and the sensor 410 is associated with significant costs. For example, the microcontroller must be more powerful, and the demands on the LED drivers are higher. In addition, it is preferably to be ensured by design measures that as little ambient light as possible falls from the outside onto the sensor and thus incorrect measurements are avoided.

5 shows a possibility for efficient dimming of the color temperature without a color management system.

FIG. 5 comprises a microcontroller 501 with a dimming characteristic 501, wherein a dimming signal DIM is applied to the microcontroller 501 and, based on a CCT characteristic 503, into a signal for a warm white LED 507 and based on a CCT characteristic 504 in FIG a signal for a cold white LED 508 is decomposed. The microcontroller 501 derives its output signals via a driver 505 to the LED 507 and a driver 506 to the LED 508. The driver 505, 506 and the microcontroller 501 are powered by a power supply 509 with power. Thus, the dimming signal DIM is processed by means of the dimming characteristic 502 and by means of the two further characteristics 503 and 504. These two characteristics 503 and 504 determine the proportion of light of the warm white LED 507 and the cold white LED 508 in the total light. As a result, all intermediate colors, which lie in the CIE xy diagram between the color locations of the two LED colors, can be set as a function of the desired brightness of the dimming signal DIM.

By the shape of the characteristics, the characteristic, e.g. the color temperature of the dimming signal DIM depending determined and adjusted. It is also possible by suitable choice of the characteristic curves 503, 504 to determine whether the total light of the two LEDs 507, 508 should be generated as energy-efficiently as possible or cost-effectively.

Fig. 6 shows a dimming with a color management system. In addition to the description of Figure 5, a microcontroller 601 is provided with a color controller 604 which is supplied with a sensed signal (e.g., brightness and / or color temperature) via a sensor 605.

In FIG. 6, the microcontroller 601 also comprises a characteristic 602 for adjusting the color temperature and a dimming characteristic 603. Using a dimming signal DIM, the microcontroller uses the characteristic curves 602 and 603 to determine a color temperature CCT and a brightness BRI which are processed further in the color controller into output signals for a red LED 609, a green LED 610 and a blue LED 611. The LEDs 609 to 611 are driven by drivers 606 to 608. Both the drivers 606 to 608 and the microcontroller 601 are powered by a power supply 612. The color management system comprising the color controller 604 and the sensor 605 can directly detect and evaluate a color temperature. On the other hand, based on the characteristic curve 602, the desired color temperature can be derived from the dimming signal. Accordingly, the color controller 604 may set the actual color temperature so that the target preset is (almost) the actual value. Such an adjustment can be done iteratively automatically. The same applies to the brightness, the target value of which can likewise be determined from the dimming signal DIM on the basis of the dimming characteristic 603 and can be adjusted automatically by means of the color controller 604 taking into account the brightness value (actual value) supplied by the sensor 605.

LIST OF REFERENCE NUMBERS

101 Characteristic: Delivered amount of warm white LED in

Dependence of the controller position 102 Characteristic curve: Color temperature of the lamp as a function of the controller position

103 Characteristic: Delivered light quantity of the lamp as a function of the controller position

104 Characteristic: Delivered amount of light cold white LED as a function of the controller position

201 Characteristic: Delivered amount of warm white LED as a function of the controller position

202 Characteristic: Delivered light quantity of the lamp as a function of the controller position

203 Characteristic: Color temperature of the lamp depending on the controller position

204 Characteristic: Delivered amount of light cold white LED depending on the controller position

301 microcontroller

302 dimming characteristic

303 LED driver

304 LED driver

305 LED (warm white)

306 LED (cold white)

307 power supply

401 microcontroller

402 dimming characteristic

403 LED driver

404 LED driver

405 LED driver

406 LED (red)

407 LED (green)

408 LED (blue)

409 color controls 410 sensor

411 power supply

501 microcontroller

502 dimming characteristic

503 CCT characteristic for LED 507

504 CCT characteristic for LED 508

505 LED driver

506 LED driver

507 LED (warm white)

508 LED (cold white)

509 power supply

601 microcontroller

602 Characteristic curve for color temperature adjustment

603 dimming characteristic

604 color controls

605 sensor

606 LED driver

607 LED driver

608 LED driver

609 LED (red)

610 LED (green)

611 LED (blue)

612 power supply

Claims

claims 1. A circuit for dimming a lamp comprising at least two light units (507, 508), - with a control unit (501) for coupling a brightness and a color temperature depending on an input signal (DIM); - Wherein dependent on the input signal (DIM) based on the control unit, the at least two lighting units (507, 508) are controllable. 2. A circuit according to claim 1, wherein the lighting unit (507, 508) comprises an LED or an LED module. 3. A circuit according to any one of the preceding claims, wherein the basis of the control unit (501) by means of the input signal based on a dimming characteristic (502) and based on a characteristic for color matching (503, 504) per lighting unit, the at least two lighting units (507, 508 ) are controllable. 4. A circuit according to one of the preceding claims, wherein the control unit (601) comprises a color controller (604), the color controller (604) depending on a measured value determined by a sensor (605) the at least two light units (609, 610, 611 ). 5. A circuit according to any one of the preceding claims, wherein the control unit based on the input signal (DIM) determines the brightness and the color temperature. 6. A circuit according to any one of the preceding claims, wherein the control unit based on the input signal, the brightness and the color temperature based on Characteristics or stored values. 7. A circuit according to any one of the preceding claims, wherein the driver (505, 506) for controlling the at least two lighting units (507, 508) are provided. 8. A circuit according to any one of the preceding claims, wherein with increasing brightness of the lamp, a higher color temperature is adjustable. 9. A circuit according to any one of the preceding claims, wherein with decreasing brightness of the lamp, a lower color temperature is adjustable. 10. A circuit according to any one of the preceding claims, wherein a warm white light unit (507) and a cold white light unit (508) are provided. 11. A method for driving a lamp comprising at least two light units (507, 508), - In which dependent on an input signal (DIM) a brightness and a color temperature of the lamp are determined; - In which dependent on the determined brightness and color temperature, the at least two lighting units (507, 508) are controlled. 12. The method of claim 11, wherein the brightness and the color temperature are determined based on at least one characteristic, in particular one per characteristic curve per lighting unit is provided for an adjustment of the color temperature. 13. The method according to any one of claims 11 or 12, wherein the input signal is a dimming signal. 14. The method according to any one of claims 11 to 13, - In which by means of a sensor (605) a color temperature and / or brightness of the lamp is detected / and - In which, depending on the detected color temperature and / or the detected brightness, a control (604) of the at least two lighting units is performed.