EP2882263A1 - Driver circuit and method for operating a dimmable LED section in a dimming area with two areas - Google Patents

Abstract

A driver circuit is provided for operating over a dimming range dimmable operation of a driver provided by the driver circuit LED circuit, wherein the driver circuit is designed such that the dimming region has at least a first region in which the dimming is performed by means of amplitude variation of the LED current, and a second region, not overlapping with the first region, in which the dimming is additionally and / or alternatively carried out by means of PWM modulation of the LED current, wherein the second region lies below adjacent to the first region, and wherein a dimming value in which the Transition from the first area to the second area is adjustable. The adjustable dimming value is also referred to below as the transition dimming value.

Description

The invention relates to a driver circuit and a method for controlling a dimmable light source. The driver circuit supplies the illuminant path, in particular an LED path with at least one LED, directly or indirectly electrically and allows the dimming of a light path connected or connectable to the driver circuit via a dimming range. In the present case, the term illuminant path also means at least one LED module which, in addition to the luminous means, has further components such as a memory and / or a communication interface. In particular, the light path can also have one or more OLEDs.

From the prior art, it is known to select a dimming method for dimming LEDs / OLEDs, which uses either a pulse width modulation (PWM) of the LED current or an amplitude modulation (AM), ie a change in the amplitude value of the luminous flux. As the state of the art should be exemplified here WO 2011/024101 A1 , the EP 1 689 212 B1 and the DE 198 48 925 B4 to be named.

In particular, it is known that at higher dimming levels, ie when lamps are to be operated with a slightly reduced brightness, a dimming by means of amplitude modulation takes place until a certain dimming level is reached, at which the amplitude is constant is held. Then, dimming by means of PWM modulation is performed to dim to dimming values below the determined dimming level, ie when, for example, a low dimming level is required.

The problem now is that an analog dimming, i. Dimming by means of a change in the amplitude value, on the one hand, has an effect on the color constancy of the lighting means. In particular, a color shift, a color shift, can be caused by the amplitude change. On the other hand, limits of PWM dimming at low dimming values result in the lowest settable duty cycle. Thus, due to the light source to be operated, the purpose or the environment in systems of the prior art in dimming various negative characteristics can be noticeable, which in particular affect the quality of the light output.

It has now been recognized that the transition point between the analog and the PWM dimming, ie the transition dimming value or dimming level at which the dimming is changed by means of amplitude variation to the PWM dimming, advantageously depends on the design of the luminous means or the concrete Purpose should be set. The invention therefore proposes a driver circuit with an adjustable transition dimming value. In addition, a method for the operation of an LED track is disclosed. The driver circuit and method are the subject of the independent claims. Further developments of the invention are the subject of the dependent claims.

In a first aspect, a driver circuit is provided for dimming via a dimming range operable by the driver circuit LED track, wherein the driver circuit is designed such that the dimming region has at least a first region in which the dimming carried out by means of amplitude variation of the LED current and a second region not overlapping with the first region, in which the dimming is additionally and / or alternatively carried out by means of pulsed modulation, preferably PWM modulation of the LED current, the second region lying below adjacent to the first region, and wherein a dimming value at which the transition from the first region to the second region occurs is adjustable. The adjustable dimming value is also referred to below as the transition dimming value. In particular, in the case of a dynamic change of a predetermined dimming value to be dimmed to the LED track, the driver circuit can control the LED track in a limited range around the adjustable dimming value and / or for a limited period of time with a combination of dimming by means of amplitude variation and from dimming by means of PWM modulation dimming.

The driver circuit may adjust the adjustable dimming value depending on the LED path operated by the driver circuit.

The driver circuit may have a user interface over which the adjustable dimming value is adjustable. The adjustable dimming value may be adjustable by a user and / or production side.

The LED route may alternatively or additionally have at least one OLED.

The driver circuit may have a sensor interface, in particular for a connection to a photosensor and / or a temperature sensor.

The driver circuit can be detected by direct, in particular by retrieving the information from the LED link, e.g. set the adjustable dimming value by accessing a memory, determined information and / or an indirect, in particular by detecting parameters determined information.

The driver circuit may detect as parameters electrical parameters of the LED route and / or environmental parameters, in particular by means of connectable sensors.

The driver circuit may conclude from determined information on the type of LED route to be operated and adjust the adjustable dimming value depending thereon.

The driver circuit may detect at least one test dimming curve by means of a connectable sensor, e.g. by detecting emission characteristics of the LED path over a certain period of time, and based on this, determining and setting the adjustable dimming value. The driver circuit may further comprise a functionally connected evaluation circuit, which serves for the evaluation of acquired data / parameters.

The driver circuit may store the at least one detected test dimming curve in a memory operatively connected to the driver circuit.

The driver circuit can in particular have a bus interface, preferably a DALI bus interface, and can set the adjustable dimming value as a function of a signal supplied via the bus interface, in particular a bus command.

An amplitude value may decrease by dimming by means of an amplitude change towards the adjustable dimming value, and dimming below the adjustable dimming value may be effected by means of PWM modulation, preferably with the smallest amplitude value with respect to the adjustable dimming value and preferably with constant timing.

The driver circuit can communicate with the LED link via a communication interface.

The driver circuit may comprise a memory, in particular a look-up table, in which preferably at least one adjustable dimming value, e.g. in association with information about the LED route and / or parameters, is stored, and wherein the driver circuit based on the direct and / or indirect information set the adjustable dimming value, and in particular from the memory can retrieve.

In a further aspect, a method is provided for dimming a dimmable operation of an LED array powered by a driver circuit, wherein the driver circuit performs dimming by amplitude variation of the LED current in a first region of the dimming region and not into one with the first region overlapping second area, the dimming additionally and / or alternatively by means of PWM modulation of the LED current wherein the second region is located below adjacent to the first region, and wherein a dimming value at which the transition from the first region to the second region occurs is adjustable. In particular, the first and second regions do not overlap.

Fig. 1

schematisch zwei Einstellungen für den einstellbaren Dimmwert einer Treiberschaltung nach der Erfindung;

Fig. 2

schematisch die Treiberschaltung; und

Fig. 3

schematisch eine zweite Ansicht der Treiberschaltung.

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

Fig. 1

schematically two settings for the adjustable dimming value of a driver circuit according to the invention;

Fig. 2

schematically the driver circuit; and

Fig. 3

schematically a second view of the driver circuit.

In the following, the dimming of the luminous means path by means of an amplitude change of the luminous flux is also referred to as analog dimming or amplitude dimming, while the dimming by means of pulse width modulation of the luminous flux is also referred to as PWM dimming.

The setting of the adjustable dimming value or of the transition dimming value can be carried out depending on different criteria.

For example, it can be provided that for dimming values which are above the transition dimming value, purely analog dimming takes place, while in the lower range, ie below the transition dimming value, pure PWM dimming takes place. Preferably, therefore, there is no mixing of the two dimming processes in the static state. At a However, dynamic dimming may cause the dimming processes to overlap, in particular at the transition dimming value or within a limited range around the transition dimming value or for a limited time.

In particular, for the PWM dimming, the lowest constant clocked amplitude value can be chosen, that is, the amplitude value assumed at amplitude transition at the transition dimming value (i.e., the amplitude value resulting from approaching a dimming value to the transition dimming value at dimming with amplitude variation).

According to the invention, it is now possible to adjust the transition dimming value due to various factors.

One possibility is to provide the driver circuit with a user interface, for example a controller accessible to a user, via which the transition dimming value can be set. As a result, the dimming value can also be set on the production side, for example, depending on a customer-specific application.

It can further be provided that the driver circuit detects information, and adjusts the transition value accordingly during operation or when connecting a light path. For this purpose, the driver circuit may be designed so that it can retrieve information from the light path, for example by accessing a memory of the light path, which in particular identifies the type and / or configuration light source. This information is in the Hereinafter referred to as direct information, since the driver circuit directly accesses the illuminant path. However, the driver circuit may alternatively or additionally also be designed to indirectly determine information and thus to infer the type of connected lamps or ambient conditions.

Thus, the driver circuit can be set up to detect and / or evaluate electrical parameters of the light path. For example, the evaluator driver circuit may use an integrated circuit (IC, ASIC) that is operatively connected to the driver circuit. On the basis of the detected electrical parameters or based on their evaluation, on the one hand can be closed to the type / configuration of the light path to be operated. On the other hand, environmental parameters can be detected and included, for example, via additionally or alternatively provided sensors, for example temperature or photosensors. The detected and / or evaluated electrical and / or environmental parameters are referred to below as indirect information.

Depending on the detected direct or indirect information, the driver circuit may then set the transition dimming value. For this purpose, the driver circuit can also access a memory assigned to it, in which data for setting the transition dimming value are stored. Thus, for example, based on the look-up table and on the basis of the information, an associated transition dimming value can be selected. Furthermore, in the memory assigned to the driver circuit, there can also be at least one function be deposited so that depending on the information collected, the determination of a transition dimming value is functional.

The driver circuit can therefore also have a sensor interface, via which it can be connected to a temperature sensor and / or a photosensor, in order in particular to detect or measure test dimming curves. This can be done, for example, in a configuration phase of the driver circuit or in the factory under conditions that simulate those prevailing during later use. This can also be done to adapt to certain bulbs. It can also be provided that the configuration phase is triggered manually or automatically again, for example, in order to achieve an adaptation to changing environmental conditions and / or lighting means. The latter can also be used without replacement, e.g. due to signs of aging of the bulbs result.

By the driver circuit so measurements can be made, in which the driver circuit light characteristics of the light path depending on different dimming detected and determined on the basis of the detected properties, or the behavior of the light path an optimal transition dimming value of the analog dimming to PWM dimming.

In particular, it is also possible for the driver circuit to differentiate between different illuminant paths on the basis of their electrical properties. Thus, a light path with LED bulbs can be distinguished from a light path with OLED bulbs, as the electrical characteristics of OLEDs and LEDs are different. Among other things, a change in color is more pronounced with an analog dimming of OLEDs than with an analog dimming of LEDs. In the case of a light path with OLEDs, or in the case of operation of a light path with only OLEDs, therefore, the transition dimming value is chosen differently than when operating a light path with exclusively LEDs. The transition dimming value is then higher in OLEDs, in particular, than when a light-emitting diode array is operated with only LEDs.

Further, adjustment of the adjustable transition dimming value may be based on a signal / command supplied to the driver circuit. One possibility is to specify to the driver circuit via the electrical supply a dimming value to be set, for example by supplying a supply voltage of alternating and / or different polarity, or by an on / off sequence. On the other hand, the supply of the signal can also take place via a bus interface. For this purpose, a bus interface of the driver circuit may preferably be connected to a DALI or DSI bus.

Via the bus interface, the driver circuit can also inform other bus users, for example, about the adjustable transition dimming value to be set or set. It is thus possible, for example, for the driver circuit, by means of measurements and / or sensory detection, to ascertain information and data which are relevant for setting the transition dimming value. If the transition dimming value is determined by the driver circuit, the driver circuit can apply this transition dimming value to another Transmit driver circuits, for example, do not have the ability to capture / determine the appropriate information or data, so for example, have no sensor interface.

In particular, in the case of static dimming, it is desirable that the area in which PWM dimming is performed and the area where amplitude dimming is performed not overlap, so that there is a separation between the two dimming methods.

However, dynamic dimming may result in a mixture of dimming procedures at the adjustable switching dimming value for a limited period of time or within a limited range.

The Fig. 1 shows two examples in which the transition dimming value is changed by the driver circuit. Here it is shown that the transition dimming value on the one hand to x% ( Fig. 1 left) or on the other hand to a higher dimming value y% ( Fig. 1 right) to adjust the ranges of dimming using PWM modulation (PWM) or amplitude modulation (AM).

Depending on the setting of the adjustable transition dimming value, it is also possible, for example, to dim only by changing the amplitude or exclusively by means of PWM dimming. This is the case when the transition dimming value is set to zero percent (0%) or a minimum dimming value (eg 5%) or to one hundred percent (100%) or a maximum dimming value (eg 80% - 95%). In the first case, then a dimming can be done only by means of amplitude change, in the second case only with pulse width modulation, or vice versa. As mentioned, the adjustment of the transition dimming value can be done by a user or based on the connected light source.

Fig. 2 shows by way of example how the driver circuit TS on the one hand supplies the light source LM, on the other hand, however, additionally can exchange data D with the light source. In particular, the light-emitting means path has a memory S which contains information about the light-emitting means path. Thus, the driver circuit TS directly detects information about the light path LM to adjust according to the adjustable transition dimming value. Schematically, a bus interface bus and a sensor interface Sens are shown on the driver circuit, as well as an optional memory TSS associated with the driver circuit.

As an alternative to the memory TSS, the luminous means LM may also have a coded plug or a coded socket for connection to the driver circuit or an operating device having the driver circuit, the driver circuit then being able to detect the type of luminous means depending on the plug / socket.

In particular, bidirectional communication can take place between the driver circuit TS and the luminous means LM, so that the driver circuit TS can, for example, change or adapt parameters of the luminous means LM. The communication between driver circuit TS and light source LM can of course either analog or digital. However, a communication via a separate communication interface to driver circuit TS and / or light source LM is not absolutely necessary, since a communication via the supply V, for example by modulation of the supply parameters can be done.

Another exemplary embodiment is exemplary in FIG Fig. 3 shown, in which the driver circuit TS only communicates via the supply V with the illuminant path. The driver circuit TS has in Fig. 3 a detection circuit / detection circuit, which may be provided in addition to or as an alternative to already described components of the driver circuit TS. This detection circuit is preferably configured to detect electrical parameters, such as current or voltage parameters or capacitance values, which serve directly or indirectly to the supply V of the light-emitting means path LM.

The detection of the parameters can also take place continuously, so that the transition dimming value can be changed in the case of a change in the light path, for example due to aging phenomena, and a resulting change in the electrical parameters of the light source LM and / or in a change of the environmental parameters.

As an electrical parameter, the leakage current can also be measured, for example, if OLEDs are used as the light source of the illuminant path. For example, even in LED circuits where white light LEDs together with LEDs of other color, For example, red LEDs are operated, the adjustable transition dimming value are set by the driver circuit TS detects or monitors saturation of the LEDs, and detects by their measurement, at which Dimmwert the colored LEDs are no longer conductive / no longer active. For this purpose, the driver circuit TS can also use the optional photo sensor. The driver circuit can then set the adjustable transition dimming value so that it is above the dimming value at which the colored LEDs no longer conduct, so that below this dimming value dimming takes place only with PWM modulation.

As an alternative to the PWM modulation, other pulsed modulation modes can also be used according to the invention, for example a pulse width modulation or pulse code modulation.

Claims (15)

Driver circuit for dimming via a dimming operation of a supply of the driver circuit LED track,
wherein the driver circuit is designed such that - the dimming region has at least a first region in which the dimming means
Amplitude change of the LED current is performed, and a non-overlapping with the first area second area in which the dimming is additionally and / or alternatively carried out by means of PWM modulation of the LED current, the second area below is adjacent to the first area , and where - A dimming value, in which the transition from the first region to the second region takes place, is adjustable. Driver circuit according to claim 1, wherein the driver circuit is adapted to adjust the adjustable dimming value depending on the operated by the driver circuit LED route. Driver circuit according to claim 1 or 2, wherein the driver circuit has a user interface, via which the adjustable dimming value is adjustable. Driver circuit according to one of the preceding claims, wherein the LED path alternatively or additionally comprises at least one OLED. Driver circuit according to one of the preceding claims, wherein the driver circuit has a sensor interface, in particular for connection to a photosensor and / or a temperature sensor. Driver circuit according to one of the preceding claims, wherein the driver circuit is adapted, on the basis of a direct, in particular by retrieving the information from the LED track, e.g. by accessing a memory, determined information and / or an indirect, in particular by detecting parameters determined information to set the adjustable dimming value. Driver circuit according to one of the preceding claims, wherein the driver circuit is adapted to detect as parameters electrical parameters of the LED route and / or environmental parameters, in particular by means of connectable sensors. Driver circuit according to one of the preceding claims, wherein the driver circuit is adapted to close from the determined information on the type of LED track to be operated and to set depending on the adjustable dimming value. Driver circuit according to one of the preceding claims, wherein the driver circuit is adapted to detect by means of a connectable sensor at least one test dimming curve, for example by Detecting emission characteristics of the LED route over a certain period of time, and based on this, determining and setting the adjustable dimming value. Driver circuit according to one of the preceding claims, wherein the driver circuit is adapted to store the at least one detected test dimming curve in a memory operatively connected to the driver circuit. Driver circuit according to one of the preceding claims, in particular comprising a bus interface, preferably a DALI bus interface, wherein the driver circuit is adapted to adjust the adjustable dimming value depending on a signal supplied via the bus interface, in particular a bus command. Driver circuit according to one of the preceding claims, wherein an amplitude value decreases during dimming by means of amplitude change to the adjustable dimming value, and wherein the dimming below the adjustable dimming value by means of PWM modulation, preferably with respect to the adjustable dimming value smallest amplitude value and preferably with constant timing, takes place. Driver circuit according to one of the preceding claims, wherein the driver circuit is adapted to communicate with the LED link, for example via a communication interface. Driver circuit according to one of the preceding claims, wherein the driver circuit comprises a memory, in particular a look-up table, in which at least one adjustable dimming value, e.g. in association with information about the LED route and / or parameters, is stored, and wherein the driver circuit is adapted to set on the basis of the direct and / or indirect information, the adjustable dimming value, and in particular to retrieve from the memory. Method for dimming a dimming range of an LED circuit that can be supplied by a driver circuit,
wherein the driver circuit in a first range of the dimming range performs the dimming by amplitude variation of the LED current, and in a second range not overlapping with the first range dimming additionally and / or alternatively by means of PWM modulation of the LED current, the second Area below is adjacent to the first area, and wherein - a dimming value at which the transition from the first area to the second area is adjustable.

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