EP2992734A1

EP2992734A1 - Method for altering the colour location of the visible light emitted by an led module

Info

Publication number: EP2992734A1
Application number: EP14724020.4A
Authority: EP
Inventors: Peter Pachler
Original assignee: Tridonic Jennersdorf GmbH
Current assignee: Tridonic GmbH and Co KG
Priority date: 2013-04-30
Filing date: 2014-04-29
Publication date: 2016-03-09
Also published as: WO2014177535A1; DE102013207961A1

Abstract

The invention relates to a method for altering the colour location of the visible light emitted by an LED module, said LED module having at least two parallel LED sections, each section having at least one LED and the emission spectra of the LED sections being different. The LED sections are operated alternately with a constant current and in order to alter the colour location, the relationship between the activation periods of the LED sections is altered, preferably whilst maintaining the sum of the activation periods of all the LED sections.

Description

Method of changing the color locus of a LED

Module emitted visible light

The invention relates to a method for changing the color locus of the visible light emitted by an LED module and to a control module which is designed to carry out the method according to the invention, and in particular to an LED module for operating at least two LED paths. The control module can be supplied starting from a supply voltage (AC voltage / DC voltage) and, based on this, the at least two LED paths can each be operated with at least one LED. Preferably, the at least two LED sections and the LED module together with the control module form a unit, so that this unit is buildable in a lamp or light. The aim of the invention is to provide a solution which makes it possible to dynamically and gradually change a color location or a color temperature of the light emitted by the LED paths. In particular, the invention proposes to operate two basically identical white-light LEDs, which however have a different color temperature or a different emission spectrum, in parallel or alternately.

Both LED paths are preferably operated by means of a PWM modulation, wherein the control module is adapted to change a duty cycle of the PWM modulations. In particular, the control module may separately change the _on- time (T _on- time) of the PWM signal for each of the LED links. This makes it possible to influence the switch-on duration of the LED circuits, the aim being to avoid a flickering of the LED circuits and thus the switch-on frequency, with which a PWM module controls the LED circuits, above the threshold of approx 80 Hz, preferably 100 Hz, as of which switching is no longer perceptible to the human eye.

Since the LED strips used preferably have different color temperatures, by changing the T _on times of the LED strips, it is now possible to set any color temperature or any color location which lies between the color locations of the LED strips used.

This setting of the color locus can be further combined with a dimming function. Thus, e.g. In a known manner, a relatively slow dimming PWM modulation are used whose duty cycle dictates a dimming value, i. a value to which the LED strips are to be dimmed. A corresponding evaluation is carried out by the control module.

Following on from this dimming PWM modulation, the color PWM modulation for the color temperature change can take place according to the invention. It can be provided that within the switch-on period of the dimming PWM pulse of the dimming PWM modulation of the dimming PWM pulse is divided into the at least two parallel LED links. This means that the switch-on duration of the dimming PWM pulse defines the maximum sum of the switch-on durations of the LED lines, the switch-on duration of the dimming PWM pulse is thus divided as the available total switch-on time duration for the LED paths. Alternatively or additionally, it can be provided that an entire dimming PWM pulse is used to control one of the two LED paths and then the duty cycle for changing the temperature value is changed by a variable number of dimming PWM pulses being applied to the other LED Route is switched.

Thus, the LED circuits can be supplied from different power sources, which can preferably provide as constant current sources supply currents of different heights for the LED circuits. Preferably, however, only one current source can be switched to the parallel LED paths. For the purposes of the invention, the parallel operation includes alternating operation. The LED routes are therefore provided in parallel, but can be operated alternately.

In addition to white light LEDs, of course, colored LEDs can be connected in parallel, and by appropriate control of the LEDs, the color temperature / color location can be further changed, in particular, the area in which the color temperature can be changed can be increased.

However, by activating the different parallel LED paths, white light is preferably always generated, wherein, if further colored (eg red, green, blue) LED paths are provided in parallel, the color rendering index is color-coded by the color PWM modulation of the duty cycle of the resulting white mixed light can be improved.

Along with changing the duty cycles of a first LED track, e.g. a 'cold' light (e.g., 3300K to 5300K, especially 4000K, preferably over 5300K, e.g., 6500K) and a second LED path, e.g. 'Warm' light emits (for example, under 3000K to 3300K), and which represent the white light path, so also a duty cycle between the colored LED tracks or a red and a green LED track is changed accordingly.

This creates a system of, for example, four LED paths (eg at least two white light LEDs with different color temperature, a green LED and a red LED), which makes it possible to set different color temperatures. The invention thus provides an apparatus and a method as claimed in the independent claims. Further developments of the invention are the subject of the dependent claims. In a first aspect, the invention provides a method of changing the color location of the visible light emitted by an LED module, the LED module having at least two parallel LED paths, each having at least one LED, the emission spectrum of the LED Different routes, and wherein the LED routes are operated alternately with constant current, and color change for changing the ratio of the turn-on periods of the LED routes, preferably while keeping constant the sum of the turn-on time durations of all LED routes.

The sum of the switch-on durations of all LED sections can be predetermined by a dimming signal.

The dimming signal may be evaluated by the control module such that the dimming signal sets an upper limit of a total turn-on duration of all the LED paths.

The turn-on durations of the LED paths may be adjusted depending on a color temperature change signal.

The LED routes can be white light LED routes.

The LED routes can have different color temperatures.

At least one of the LED circuits can, preferably exclusively, have red, green and / or blue LEDs. The LED sections can be supplied with constant currents of different heights, in particular starting from different current sources.

The LED links can be powered from a single power source.

The LED sections can be switched on and off alternately by means of a switching element. It is not necessary at all times to activate or activate one of the LED circuits. So it may happen that all or individual LED routes are at least temporarily disabled.

When the color temperature change signal is supplied, the switch-on time duration of the LED paths can be changed relative to one another, in particular the switch-on time duration of one LED route can be shortened / lengthened and (indirectly) proportional to this the switch-on time duration of another LED route can be lengthened / shortened.

The LED strips can be mounted on an LED module.

In another aspect, the invention provides a control module configured to perform a method as described above. In a still further aspect, the invention provides a control module having at least one input to which a dimming and / or color temperature change signal can be supplied and having at least one output from which at least two LED paths are operable, the control module being adapted thereto to evaluate a dimming and / or Farbtemperaturänderungssignal supplied to him and depends at least on the

Color temperature change signal to change a color location of the emitted light from an LED module visible light, the LED module has at least two parallel LED stretches, each having at least one LED, wherein the emission spectrum of the LED routes differs, and wherein the control module to is designed to operate the LED sections alternately with constant current, and for color change the ratio of the Einschaltzeitdauern to change the LED routes, preferably while keeping constant the sum of the switch-on of all LED routes. The control module can be designed as a ballast module for an LED module and in particular be designed to control a switch of the LED module in response to the dimming signal and / or the color temperature change signal or supply the converter module with a signal to be selected by the LED module setting displays.

The control module may be attached to the LED module.

In yet another aspect, the invention provides an LED module or luminaire having a control module as described above.

The invention will now be described with reference to the figures. Showing:

Fig. 1 is a tolerance diagram for mixing with respect to a MacAdam 1 ellipse.

Fig. 2 is a control of two LED lines without

Dimming.

Fig. 3 is a control of two LED routes with dimming.

Fig. 4 schematically shows a circuit construction.

Fig. 5 is a control of two LED routes with dimming.

Fig. 6 shows schematically a control module according to the invention. FIG. 1 is a diagram illustrating the requirements for accurately driving the LED traces to allow tolerance requirements for a MacAdam 1 ellipse over the entire dimming range (MAI Tolerance Influence Elipse, 6500K to 2700K blend).

The requirements for achieving a slight color deviation are very high. In particular, only a deviation of about ± 1.25% per channel up to a dimming value of 1% is allowed per channel to remain in the MacAdam 1 ellipse. From a dimming value of 1% higher tolerances are possible. In this case, a dimming value of 1% means, in particular, a dimming to 1% of the light output that is emitted without dimming.

The invention now provides, in particular, two different supply currents for two LED paths with different color temperatures.

In Fig. 2 is shown the current at a dimming value of 100% (behavior at a dimming value of 100% at c.a 4000K, see 100% steps of the pulses [%]), i. at full power without dimming, switching back and forth between the LED circuits.

The LED sections are supplied with supply currents of different heights. Thus, one LED track is operated with a supply current of 100% (black curve), while another LED track is operated with a current of approx. 130% (gray curve).

If the currents for the first and second LED links are the same, that would be the same output from the LED links Performance equal. This can be achieved if the one current control takes place so that the luminous flux emitted by the LED sections remains the same at the selected target color temperature.

In general, a (relative) current change between the LED links can be used to keep the luminous flux at a level, while using formulas (1) it is determined when an LED track is turned on (see parameter k). Thus, the same supply current could be used for both LED routes.

Since the total luminous flux Φ should remain the same, the following formula (2) must be solved together with the formulas (1).

By solving formulas (1) and (2), the current required to produce a constant luminous flux can be calculated. These calculations may be performed in the control module, e.g. through an IC, ASIC, or a microcontroller.

By solving the formulas (1), a ratio is defined in which the LED sections are to be switched on / off. However, when dimming down to 5% of the power (keeping the color location / color temperature of the emitted light), a situation as shown in Fig. 3 is exhibited (behavior at a dimming value of 5% at about 4000K; Pulse width of about 5% on the pulse [%] axis).

As shown in Fig. 3, the turn-on time of the currents for the LED paths is very short. For this reason, driving the LED lines must be very precise in order to obtain a specific color value / color location or a specific color temperature, especially if the LED lines are supplied from different current sources.

Alternatively, therefore, unlike the in Figs. 2 and 3, in which one current source is provided per LED path (in FIG. 1, the current characteristics of two current sources are shown), the LED paths are operated starting from only one current source.

In the case of several current sources, therefore, a change in the brightness takes place in that the switch-on time duration of the supply currents of the LED paths is reduced to the same extent during dimming while maintaining the fab location / the color temperature. Thus, an overall reduction of the output power is achieved. As can be seen in Fig. 1, 100% dimming therefore gives full brightness. Since the LED sections are operated alternately, one of the LED sections is operated at the same time with the current supplied by the respective current source. In FIG. 3, by contrast, the switch-on time duration for each of the LED line currents is reduced, so that in each case only a very short switch-on period is given, for example 5%, so that the brightness changes.

If a change in the color locus / the color temperature is now to take place, then the switch-on durations with which the LED lines are driven are to be changed relative to one another. If, for example, the switch-on time duration of the supply current for an LED route is extended, the turn-on time duration of the supply current of another LED route is simultaneously shortened. This results in a change in the color temperature.

If both the color temperature and the brightness value of the emitted light are to be changed, then both possibilities are to be combined. In particular, therefore, the turn-on of the supply current for one LED track (indirectly) is proportional to the

Switching ON period of the supply current for the other LED track to change, while at the same time the turn-on time of the LED lines is given as a whole by the ON time of the dimming signal, i. the maximum sum of the turn-on durations of the LED paths is determined by the pulse width of the Diram PWM modulation.

Alternatively, as stated, it is intended to supply both LED paths via only one current source. The basic circuit construction is shown in FIG. 4. The supply current of the LED links is here switched by means of at least one switching element ((bipolar) transistor, FET, MOSFET) between the LED links. Since the LED circuits are each operated alternately, there is in principle no requirement to provide two power sources. In particular, not at a dimming value of 100%.

As shown in Fig. 4, therefore, the switching element may be provided to switch the current path over the parallel LED paths from one LED track to another LED track. In the case of several LED paths, a change in the circuit, that is to say a plurality of switches, must accordingly be provided.

At a dimming value of 100%, the switching frequency of the switching element then sets the color temperature, while the luminous flux is adjusted by means of the supply current. At the same luminous flux of the LED sections no change is necessary. If you want to dimming down to lower luminous fluxes, you must first determine the switch-on duration of the dimming PWM signal by the controller module. If only brightness dimming is to take place, in order to keep the color temperature / color location constant, the switch-on durations for the channels must be adjusted relative to the switch-on duration of the dimming signal, as shown in FIG.

In particular, here one LED path within the dimming PWM signal is supplied with the supply current for two switch-on durations (pulses), while the other LED route is supplied with the supply flow for only one switch-on period (pulse). Thus, without complicated switching or tuning of two current sources by using the switching element, the color temperature of the emitted light can be kept constant, while only the brightness is changed.

If, on the other hand, a change in the color temperature point also takes place, the turn-on durations of the LED paths relative to one another must be changed and, in particular, the turn-on time duration of the supply current of one LED path longer or shorter in relation to the turn-on time duration of the supply current of the other LED path.

The control module according to the invention can also be provided as a ballast module for an LED module. In particular, in this case, the control module can receive a dimming signal, for example via a DALI bus, and calculate which switch-on time duration of the supply current for the LED paths must be selected in order to set a corresponding brightness value.

Alternatively or additionally, the control module may calculate how to activate the LED paths, with dimming within the on-time of the dimming PWM signal, to set a color temperature. In addition to the dimming signal or alternatively, the control module can thus receive a signal indicating a desired color temperature change relative or absolute.

Fig. 6 shows schematically the operation of the control module, the control module SM1 shown in Fig. 6 above a PWM signal PWM-ON, in particular a Dimming PWM signal is supplied. The control module SM1 is now configured to evaluate the supplied PWM signal PWM-ON. The control module SM1 then outputs PWM signals PWM-OFF LED1 and PWM-OFF LED2, which can either be used directly for controlling the LED paths or can be evaluated by a converter or LED module.

The control module SM2 shown in FIG. 6, in turn, is supplied with a PWM signal PWM-IN, in particular a dimming PWM signal. At an output, the control module SM2 outputs a combined signal PWM-OFF, which has, for example, pulses of different current level. This output signal PWM-OFF can be either directly to drive the LED links, e.g. via at least one switching element, used, or be evaluated by a converter or LED module.

The dashed lines on the output sides of the control modules SM1 and SM2 indicate that the ON periods of the output signals move within the ON period of the PWM signal PWM-ON.

Claims

Claims 1. A method of changing the color location of the visible light emitted by an LED module,

wherein the LED module has at least two parallel LED paths, each having at least one LED, wherein the emission spectrum of the LED routes differs, and

wherein the LED sections are operated alternately with constant current, and

for color change the ratio of

Einschaltzeitdauern the LED links is changed, preferably while keeping constant the sum of the switch-on durations of all LED routes.

2. The method according to claim 1, wherein the sum of the

On duration of all LED lines is given by a dimming signal.

3. The method according to claim 1 or 2, wherein the

Dimming signal is evaluated to the effect that the dimming signal is an upper limit of

Total turn-on time of all LED lines sets.

4. The method according to any one of the preceding claims,

wherein turn-on durations of the LED paths are adjusted depending on a color temperature change signal.

5. The method according to any one of the preceding claims, wherein the LED routes are white light LED routes.

6. The method according to any one of the preceding claims, wherein the LED paths have different color temperatures.

7. The method according to any one of the preceding claims,

wherein at least one of the LED sections, preferably exclusively, has red, green and / or blue LEDs.

8. The method according to any one of the preceding claims,

where the LED circuits with constant currents

different height, in particular from different power sources, are supplied.

9. The method according to any one of the preceding claims,

where the LED links are powered by a single power source.

10. The method according to any one of the preceding claims, wherein the LED sections are switched on and off alternately by means of a switching element.

11. The method according to any one of the preceding claims, wherein not at any time one of the LED links is activated.

12. The method according to any one of the preceding claims, wherein when feeding the

Color temperature change signal the

Turn-on durations of the LED routes relative

be changed to each other, in particular the

Switch-on time of an LED track

shortened / lengthened and proportional to the On-time of another LED line

lengthened / shortened.

13. The method according to any one of the preceding claims, wherein the LED strips are mounted on an LED module.

14. Control module designed to

Process according to the preceding claims

perform.

15. Control module having at least one input to which a dimming and / or color temperature change signal can be supplied and having at least one output from which at least two LED paths are operable, wherein the control module is adapted to a dimming and / or or

Evaluate color temperature change signal and

depending at least from that

Color temperature change signal to change a color location of the emitted light from an LED module visible light, the LED module has at least two parallel LED stretches, each having at least one LED, wherein the emission spectrum of the LED routes differs, and wherein the control module to is designed to operate the LED sections alternately with constant current, and to change the color change the ratio of the switch-on periods of the LED lines, preferably below

Constant maintenance of the sum of the switch-on durations of all LED routes.

16. Control module according to claim 14 or 15, wherein da control module is designed as a ballast module for an LED module and the control module in particular is designed, a switch of the LED module in response to the dimming signal and / or the

Controlling color temperature change signal or supply the converter module with a signal indicating an e-division to be selected by the LED module.

17. Control module according to one of claims 14 to 16, wherein the control module is mounted on the LED module.

18. LED module or luminaire with a control module according to one of claims 14 to 17.