DE102013022685B4 - Driver circuit and method for operating a dimmable LED track in a dimming range with two ranges - Google Patents

Abstract

Driver circuit (TS) for the dimmable operation of an LED line (LM) supplied by the driver circuit (TS) over a dimming range, wherein the driver circuit (TS) is designed such that
- the dimming range has at least a first range in which the dimming is carried out by means of amplitude variation of the LED current, and a second range not overlapping with the first range in which the dimming is carried out by means of PWM modulation of the LED current, wherein the second range is located below and adjacent to the first range, wherein
- a dimming value at which the transition from the first range to the second range occurs is adjustable, and wherein the driver circuit (TS) detects the type of LED section (LM) depending on a coded plug or a coded socket of the LED section (LM) for connection to the driver circuit (TS) in order to set the adjustable dimming value accordingly.

Description

The invention relates to a driver circuit and a method for controlling a dimmable lighting system. The driver circuit supplies the lighting system, in particular an LED system with at least one LED, directly or indirectly with electricity and allows the dimming of a lighting system connected or connectable to the driver circuit over a dimming range. In the present case, lighting system is also to be understood as at least one LED module which, in addition to the lighting system, has further components such as a memory and/or a communication interface. In particular, the lighting system can also have one or more OLEDs.

From the state of the art, it is known to choose a dimming method for dimming LEDs/OLEDs that uses either pulse width modulation (PWM) of the LED current or amplitude modulation (AM), ie a change in the amplitude value of the lamp current. The state of the art is exemplified here by WO 2011/024101 A1 , the EP 1 689 212 B1 and the DE 198 48 925 B4 be called.

US 2012/0 086 701 A1 describes a method for providing an input signal indicating a desired brightness for one or more LEDs to a first and a second parallel control path. The method further includes performing compensation in at least one of the control paths to increase the efficiency of the one or more LEDs.

US 2013 / 0 293 134 A1 describes an LED lighting device which can tone and dim, and an LED luminaire which contains the LED lighting device.

The DE 10 2011 002 830 A1 describes a method for dimming lamps operated by means of an operating device. The operating device is in particular a converter for at least one LED.

The DE 10 2008 029 816 A1 describes a circuit for dimming a lamp with lighting units. The circuit comprises a control unit for coupling a brightness and a color temperature depending on an input signal, whereby the lighting units can be controlled using the control unit depending on the input signal.

US 2011 / 0 234 104 A1 describes a load determining device and a lighting device using the same for determining and illuminating a lighting load.

WO 2010/ 034 509 A2 describes a method and a measuring device for determining the electrical properties of an OLED.

In particular, it is known that at higher dimming levels, i.e. when lamps are to be operated with a slightly reduced brightness, dimming is carried out by means of amplitude modulation until a certain dimming level is reached at which the amplitude is kept constant. Then it switches to dimming by means of PWM modulation in order to dim to dimming values below the certain dimming level, i.e. when, for example, a low dimming level is required.

The problem is that analogue dimming, i.e. dimming by changing the amplitude value, has an impact on the color consistency of the light source. In particular, a color shift can be caused by the change in amplitude. On the other hand, PWM dimming has its limits at low dimming values in the lowest adjustable duty cycle. Depending on the light source to be operated, the intended use or the environment, various negative properties can become noticeable in state-of-the-art systems when dimming, which have a particular impact on the quality of the light output.

It has now been recognized that the transition point between analog and PWM dimming, i.e. the transition dimming value or dimming level at which the change is made from dimming by means of amplitude change to PWM dimming, should advantageously be set depending on the design of the light source or the specific application. The invention therefore proposes a driver circuit with an adjustable transition dimming value. In addition, a method for operating an LED line is disclosed. The driver circuit and the 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 according to claim 1 is provided.

The driver circuit can set the adjustable dimming value depending on the LED range operated by the driver circuit.

The driver circuit may have a user interface via which the adjustable dimming value can be set. The adjustable dimming value can be adjustable by a user and/or by the manufacturer.

The LED section may alternatively or additionally comprise at least one OLED.

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

The driver circuit can set the adjustable dimming value on the basis of direct information, in particular determined by retrieving the information from the LED path, e.g. by accessing a memory, and/or indirect information, in particular determined by detecting parameters.

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

The driver circuit can use the information obtained to determine the type of LED track to be operated and set the adjustable dimming value depending on this.

The driver circuit can record at least one test dimming curve by means of a connectable sensor, e.g. by recording emission properties of the LED section over a certain period of time, and determine and set the adjustable dimming value based on this. The driver circuit can also have an evaluation circuit functionally connected to it, which serves to evaluate recorded 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 depending on a signal supplied via the bus interface, in particular a bus command.

When dimming, an amplitude value can decrease towards the adjustable dimming value by means of amplitude variation, and dimming below the adjustable dimming value can be carried out 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 track via a communication interface.

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

In a further aspect, a method according to claim 15 is provided.

• 1 schematisch zwei Einstellungen für den einstellbaren Dimmwert einer Treiberschaltung nach der Erfindung;
• 2 schematisch die Treiberschaltung; und
• 3 schematisch eine zweite Ansicht der Treiberschaltung.

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

• 1 schematically two settings for the adjustable dimming value of a driver circuit according to the invention;
• 2 schematically the driver circuit; and
• 3 schematically a second view of the driver circuit.

In the following, dimming the lamp path by changing the amplitude of the lamp current is also referred to as analog dimming or amplitude dimming, while dimming by means of pulse width modulation of the lamp current is also referred to as PWM dimming.

The adjustable dimming value or the transition dimming value can be set depending on various criteria.

For example, it can be provided that purely analogue dimming takes place at dimming values that are above the transition dimming value, while pure PWM dimming takes place in the lower range, i.e. below the transition dimming value. Preferably, therefore, the two dimming methods do not mix in the static state. However, with dynamic dimming, it can happen that the dimming methods overlap, particularly at the transition dimming value, or in a limited area around the transition dimming value, or for a limited time.

For PWM dimming, in particular, the lowest constantly clocked amplitude value can be selected, i.e. the amplitude value that is assumed at the transition dimming value during amplitude dimming (i.e. the amplitude value that results when a dimming value approaches the transition dimming value during dimming with amplitude change).

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

One possibility is to provide a user interface on the driver circuit, for example a user-accessible controller that can be used to set the transition dimming value. This also allows the dimming value to be set during production, for example depending on a customer-specific application.

It can also be provided that the driver circuit records information and, depending on this, sets the transition value accordingly during operation or when a lighting system is connected. For this purpose, the driver circuit can be designed in such a way that it can retrieve information from the lighting system, e.g. by accessing a memory of the lighting system, which in particular identifies the type and/or configuration of the lighting system. This information is referred to below as direct information, since the driver circuit accesses the lighting system directly. However, the driver circuit can alternatively or additionally also be designed to indirectly determine information and thus draw conclusions about the type of lighting system connected or about environmental conditions.

The driver circuit can be set up to record and/or evaluate electrical parameters of the lighting system. For example, the driver circuit can use an integrated circuit (IC, ASIC) that is functionally connected to the driver circuit for evaluations. On the one hand, the type/configuration of the lighting system to be operated can be determined based on the electrical parameters recorded or their evaluation. On the other hand, environmental parameters can be recorded and included, for example, via additional or alternative sensors, such as temperature or photo sensors. The electrical and/or environmental parameters recorded and/or evaluated are referred to below as indirect information.

Depending on the direct or indirect information recorded, the driver circuit can 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 is stored. For example, an associated transition dimming value can be selected using a lookup table and the information. Furthermore, at least one function can also be stored in the memory assigned to the driver circuit, so that a transition dimming value is set functionally depending on the information recorded.

The driver circuit can therefore also have a sensor interface via which it can be connected to a temperature and/or photo sensor, in particular to record or measure test dimming curves. This can be done, for example, in a configuration phase of the driver circuit or at the factory under conditions that simulate those that will prevail during later use. This can also be used to adapt to certain lamps. It can also be provided that the configuration phase is initiated again manually or automatically, for example to adapt to changed environmental conditions and/or lamps. The latter can also occur without replacement, e.g. due to signs of aging of the lamps.

The driver circuit can thus carry out measurements in which the driver circuit detects the light properties of the lamp section depending on different dimming values and, based on the detected properties or the behavior of the lamp section, determines an optimal transition dimming value from analog dimming to PWM dimming.

This makes it possible for the driver circuit to distinguish between different lighting systems based on their electrical properties. For example, a lighting system with LED lighting systems can be distinguished from a lighting system with OLED lighting systems because the electrical characteristics of OLEDs and LEDs are different. Among other things, a color change is more pronounced when OLEDs are dimmed analogously than when LEDs are dimmed analogously. For a lighting system with OLEDs, or when a lighting system is operated with only OLEDs, the transition dimming value is therefore selected differently than when a lighting system is operated with only LEDs. The transition dimming value is then higher for OLEDs in particular than when a lighting system is operated with only LEDs.

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

The driver circuit can also use the bus interface to inform other bus participants about the set or to be set adjustable transition dimming value. For example, it is possible for the driver circuit to use measurements and/or sensor detection to determine information and data that are relevant for setting the transition dimming value. If the transition dimming value is determined by the driver circuit, the driver circuit can transmit this transition dimming value to be set to other driver circuits that, for example, do not have the option of recording/determining the corresponding information or data, i.e., for example, do not have a sensor interface.

In static dimming, it is particularly desirable that the range in which PWM dimming occurs and the range in which amplitude dimming occurs do not overlap, so that there is a separation between the two dimming methods.

However, with dynamic dimming, a mixture of dimming methods may occur at the adjustable switching dimming value for a limited period of time or within a limited range.

The 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 is set to x% ( 1 left) or on the other hand to a higher dimming value y% ( 1 right) to adjust the dimming ranges using PWM modulation (PWM) or amplitude modulation (AM).

Depending on the setting of the adjustable transition dimming value, dimming can, for example, be carried out 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 (e.g. 5%) or to one hundred percent (100%) or a maximum dimming value (e.g. 80% - 95%). In the first case, dimming can only be carried out by changing the amplitude, in the second case only with pulse width modulation, or vice versa. As already mentioned, the transition dimming value can be set by a user or based on the connected light source.

2 shows by way of example how the driver circuit TS supplies the luminous source path LM on the one hand, but can also exchange data D with the luminous source path on the other. In particular, the luminous source path has a memory S that contains information about the luminous source path. The driver circuit TS thus directly records information about the luminous source path LM in order to set the adjustable transition dimming value accordingly. A bus interface Bus and a sensor interface Sens are also shown schematically 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 source path LM can also have a coded plug or a coded socket for connection to the driver circuit or an operating device having the driver circuit, whereby the driver circuit can then recognize the type of luminous source path depending on the plug/socket.

In particular, bidirectional communication can take place between the driver circuit TS and the lighting section LM, so that the driver circuit TS can, for example, change or adapt parameters of the lighting section LM. The communication between the driver circuit TS and the lighting section LM can of course be either analogue or digital. However, communication via a separate communication interface on the driver circuit TS and/or the lighting section LM is not absolutely necessary, since communication can also take place via the supply V, for example by modulating the supply parameters.

Another exemplary design is shown in 3 where the driver circuit TS only communicates with the light source via the supply V. The driver circuit TS has 3 a recognition circuit/detection circuit, which can be provided in addition to or as an alternative to the components of the driver circuit TS already described. This detection circuit is preferably designed to detect electrical parameters, such as current or voltage parameters or capacitance values, which directly or indirectly serve to supply V to the lighting path LM.

The parameters can also be recorded continuously, so that if the lamp section changes, for example due to aging, and a resulting change in the electrical parameters of the lamp section LM and/or a change in the ambient parameters the transition dimming value can be changed.

The leakage current can also be measured as an electrical parameter, for example, if OLEDs are used as the light source in the light source section. For example, in LED sections in which white light LEDs are operated together with LEDs of a different color, such as red LEDs, the adjustable transition dimming value can be set by the driver circuit TS detecting or monitoring the saturation of the LEDs and using its measurement to identify the dimming value at which the colored LEDs no longer conduct/are no longer active. The driver circuit TS can also use the optional photo sensor for this purpose. 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 only takes place with PWM modulation.

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

Claims (15)

Driver circuit (TS) for the dimmable operation of an LED section (LM) that can be supplied by the driver circuit (TS) over a dimming range, wherein the driver circuit (TS) is designed such that - the dimming range has at least a first range in which dimming is carried out by changing the amplitude of the LED current, and a second range that does not overlap with the first range, in which dimming is carried out by means of PWM modulation of the LED current, wherein the second range is located below and adjacent to the first range, wherein - a dimming value at which the transition from the first range to the second range takes place can be set, and wherein the driver circuit (TS) recognizes the type of LED section (LM) depending on a coded plug or a coded socket of the LED section (LM) for connection to the driver circuit (TS) in order to set the adjustable dimming value accordingly. Driver circuit (TS) according to claim 1 , wherein the driver circuit (TS) is adapted to set the adjustable dimming value depending on the LED section (LM) operated by the driver circuit (TS). Driver circuit (TS) according to claim 1 or 2 , wherein the driver circuit (TS) has a user interface via which the adjustable dimming value can be set. Driver circuit (TS) according to one of the preceding claims, wherein the LED path (LM) alternatively or additionally comprises at least one OLED. Driver circuit (TS) according to one of the preceding claims, wherein the driver circuit (TS) has a sensor interface (Sens), in particular for a connection to a photo sensor and/or a temperature sensor. Driver circuit (TS) according to one of the preceding claims, wherein the driver circuit (TS) is designed to set the adjustable dimming value on the basis of direct information, in particular determined by retrieving the information from the LED path (LM), e.g. by accessing a memory (S), and/or indirect information, in particular determined by detecting parameters. Driver circuit (TS) according to one of the preceding claims, wherein the driver circuit (TS) is designed to detect electrical parameters of the LED path (LM) and/or environmental parameters as parameters, in particular by means of connectable sensors. Driver circuit (TS) according to one of the preceding claims, wherein the driver circuit (TS) is designed to deduce from determined information the type of LED section (LM) to be operated and to set the adjustable dimming value depending thereon. Driver circuit (TS) according to one of the preceding claims, wherein the driver circuit (TS) is configured to detect at least one test dimming curve by means of a connectable sensor, e.g. by detecting emission properties of the LED section (LM) over a certain period of time, and to determine and set the adjustable dimming value based thereon. Driver circuit (TS) according to one of the preceding claims, wherein the driver circuit (TS) is configured to store the at least one detected test dimming curve in a memory (TSS) functionally connected to the driver circuit (TS). Driver circuit (TS) according to one of the preceding claims, in particular comprising a bus interface (bus), preferably a DALI bus interface, wherein the driver circuit (TS) is designed to adjust the adjustable dimming value depending on a (Bus) supplied signal, in particular a bus command. Driver circuit (TS) according to one of the preceding claims, wherein an amplitude value during dimming decreases by means of amplitude variation towards the adjustable dimming value, and wherein the dimming below the adjustable dimming value takes place by means of PWM modulation, preferably with the smallest amplitude value with respect to the adjustable dimming value and preferably with constant clocking. Driver circuit (TS) according to one of the preceding claims, wherein the driver circuit (TS) is configured to communicate with the LED path (LM), e.g. via a communication interface. Driver circuit (TS) according to one of the preceding claims, wherein the driver circuit (TS) has a memory (TSS), in particular a look-up table, in which at least one adjustable dimming value is stored, e.g. in association with information about the LED path (LM) and/or parameters, and wherein the driver circuit (TS) is set up to set the adjustable dimming value based on the direct and/or indirect information, and in particular to retrieve it from the memory (TSS). Method for dimmable operation of an LED section (LM) that can be supplied by a driver circuit (TS) over a dimming range, wherein the driver circuit (TS) carries out the dimming in a first area of the dimming range by changing the amplitude of the LED current, and carries out the dimming in a second area that does not overlap with the first area by means of PWM modulation of the LED current, where the second area is located below and adjacent to the first area, where - a dimming value at which the transition from the first area to the second area takes place can be set, and wherein the driver circuit (TS) recognizes the type of LED section (LM) depending on a coded plug or a coded socket of the LED section (LM) for connection to the driver circuit (TS) in order to set the adjustable dimming value accordingly.

Images