Lighting means with several leds as light sources for two light functions with an overlap of the area for their implementation and vehicle lamp equipped therewith

Abstract

A light source (01) with several LEDs (02) as light sources for two different lighting functions, with the lighting areas intended for their realization overlapping in a common lighting area (bi-functional lighting area), and a vehicle light equipped with such a light source are described. The light source (01) comprises at least one LED driver arrangement (03) with separate inputs (04) for control signals for requesting the two lighting functions and several switchable outputs (05), each representing a preset constant current source, to which the LEDs (02) or LED strings of several LEDs (02) arranged in series are connected, wherein at least the LEDs (21) of the common lighting area are connected in parallel to several outputs (51, 52, 53).

Description

[0001] The invention relates to a light source according to the preamble of claim 1, and a vehicle light equipped with such a light source according to the preamble of claim 13.

[0002] A vehicle light, for example, comprises a light interior essentially enclosed by a light housing with at least one light opening and a light lens closing this opening, and at least one light source contained therein, comprising at least one light source for at least one lighting function of the vehicle light.

[0003] Examples of vehicle lights include repeater flashing lights located at the front of the vehicle, on the sides of the vehicle and / or on the side mirrors as well as at the rear of the vehicle, exit lights, for example for ambient lighting, marker lights, brake lights, fog lights, reversing lights, as well as typically high-mounted third brake lights, so-called central, high-mounted braking lights, daytime running lights, headlights and also fog lights used as turning or cornering lights, as well as combinations thereof.

[0004] Such a combination is regularly implemented in familiar rear lights. These lights combine, for example, repeater turn signals, marker lights, brake lights, fog lights, and reversing lights, to name just one of the many combinations found in rear lights. This list is neither exhaustive nor does it mean that all of the mentioned lights must be combined in a single rear light. For instance, only two or three of the mentioned lights, or even other lights, may be combined in a single rear light housing.

[0005] Every vehicle light, especially automotive lights, fulfills one or more tasks or functions depending on its design. Each task or function is achieved through a specific lighting function. Examples of lighting functions include illuminating the road in a headlight design, signaling (such as a flashing light to indicate direction or a brake light to indicate braking), and parking lights (such as a taillight) to ensure the vehicle's visibility day and / or night, as seen in taillights or daytime running lights.

[0006] Every lighting function must fulfill a legally prescribed light distribution. This light distribution defines minimum luminous flux values, commonly referred to as brightness, within specific solid angle ranges.

[0007] Different brightness levels or viewing distances, as well as different light colors, are assigned to the individual lighting functions.

[0008] When viewed from outside the luminaire's interior, either looking at or through the light diffuser, each lighting function is realized by at least one luminous surface, such that a luminous surface is available for each lighting function at least while it is being performed. Examples of luminous surfaces are: a transparent surface area backlit by one or more light sources, for example a light disc or - in the case of a clear light disc - an optical disc arranged between the light disc and the light source, a surface area illuminated by one or more light sources, for example a reflector, a viewing surface of one or more light sources, as well as combinations thereof.

[0009] Due to their high efficiency in converting electric current into light visible to the human eye, semiconductor light sources, such as inorganic light-emitting diodes or organic light-emitting diodes, are increasingly used as light sources for vehicle lights.

[0010] Inorganic light-emitting diodes consist of at least one light-emitting diode semiconductor chip, or LED chip for short, and at least one primary optic, which is molded on, for example, by injection molding, and completely or partially encloses the at least one LED chip. Vehicle lights are also known in which pure LED chips without molded-on primary optics are used.

[0011] Known types include inorganic light-emitting diodes for through-hole mounting (THT; Through Hole Technology), surface-mountable (SMD; Surface Mounted Device) LEDs, and LEDs in which the LED chip is bonded directly to the light source carrier using bare-metal mounting technology (COB; Chip On Board).

[0012] For the sake of completeness, it should also be mentioned that other contact configurations are possible, such as the so-called flip-chip design, in which the LED chip's contact elements are directly connected to a substrate. In these cases, no bond wire is used.

[0013] For the sake of simplicity, the following text will no longer distinguish between inorganic light-emitting diodes and LED chips, and will instead use the term LED to refer to both, unless explicitly stated otherwise. The outstanding properties of LEDs compared to other, conventional light sources are a significantly longer lifespan and a considerably higher luminous efficacy for the same power consumption. In other words, LEDs consume less power than other light sources for the same luminous intensity. Therefore, when one or more LEDs are used as the light source in a vehicle light, for example, the load on the vehicle's electrical system can be reduced, resulting in energy savings for the vehicle.Furthermore, LEDs have a significantly longer lifespan than other light sources suitable for use in vehicle lights. This longer lifespan, among other things, increases operational reliability and consequently the quality of the vehicle light due to a lower failure rate.

[0014] In addition to their higher luminous efficacy, another reason for the increased use of semiconductor light sources, such as LEDs (inorganic light-emitting diodes) and / or OLEDs (organic light-emitting diodes), in vehicle lighting applications lies primarily in their short, virtually immeasurable activation time from the moment current is applied until light is emitted. Unlike an incandescent bulb, the light emission occurs almost instantly at full intensity, proportional to the current. This results in enhanced perceptibility of lighting functions implemented using semiconductor light sources, thereby increasing the road safety of vehicles equipped with these light sources.

[0015] To operate semiconductor light sources as light sources for a lamp in a vehicle light, one or more more or less complex electronic control circuits are required, which can be arranged, for example, on one or more lamp carriers of the lamp and housed inside the lamp.

[0016] A simple example of an electronic control circuit involves equalizing the brightness of individual LEDs or LED strings within a group of LEDs operating together and mounted on one or more light carriers. Such an electronic control circuit consists of at least one or more series resistors to adapt the forward voltage of the LEDs to the vehicle's electrical system. For example, it is known to sort LEDs according to forward voltage and intensity using a process called binning. To compensate for differences between several LED strings, each consisting of LEDs with the same forward voltage and intensity connected in series, and to achieve a homogeneous brightness distribution among adjacent LED strings with different forward voltages and intensities, at least each LED string is equipped with a different series resistor.

[0017] When used as light sources in vehicle lights, semiconductor light sources require separate failure detection. This is due to the generally low power consumption of LEDs and OLEDs. For example, a control unit installed in a vehicle is unable to detect a change in the power draw from the vehicle's electrical system corresponding to the failure of one or a few LEDs or OLEDs, as the resulting change in the electrical system voltage is below the voltage fluctuations that occur during normal vehicle operation. An electronic circuit arrangement for failure detection, for example, located in the vehicle light, detects the failure of one or more semiconductor light sources in the light using one or more comparators and informs the control unit.Such an electronic circuit arrangement for failure detection can be implemented, for example, by an electronic control circuit mounted on the light source carrier.

[0018] The use of semiconductor light sources instead of conventional light sources, especially in vehicle lights, also results in changes to the technical design of the power supply.

[0019] Unlike conventional light sources with a nearly constant ohmic resistance, semiconductor light sources have a non-linear current / voltage characteristic. To utilize their high efficiency and consistently high luminous efficacy, semiconductor light sources must be operated at a precise operating point. Otherwise, fluctuating brightness and poor efficiency would result. Due to manufacturing variations in semiconductor light sources, their operating point cannot be precisely set using a simple voltage source. This is only possible with a constant current source, also known as an LED driver. This is a more or less complex electronic control circuit comprised of one or more electronic components, for example, mounted on the substrate of a semiconductor light source.An LED driver can either be built discretely with individual electronic components, or comprise an integrated electronic circuit component, such as a driver IC (IC; Integrated Circuit).

[0020] It is important to emphasize here that the term "LED driver" does not imply any restriction regarding the types of semiconductor light sources that can be connected. Therefore, in the following text, the term "LED" will be used to refer to any type of semiconductor light source, unless explicitly stated otherwise.

[0021] Common LED drivers include: LED series resistors, linear LED drivers, and switched-mode LED drivers.

[0022] The cheapest option is the LED series resistor. This consists of a resistor connected in series with the LED. It limits the current flow to a pre-calculated value. This LED driver variant is, of course, extremely inexpensive, but it has some disadvantages, such as the power dissipation as heat, which is proportional to the voltage drop across the resistor. This at least partially negates the advantages of the LED's high efficiency. Furthermore, the LED reacts directly to fluctuations in the supply voltage with fluctuations in brightness, since this cost-saving version lacks active regulation.

[0023] A linear LED driver converts a higher input voltage to the set operating current of the LED. Due to the voltage difference between the input and output, the linear LED driver has a control range to compensate for fluctuating on-board voltage. This prevents any brightness fluctuations of the LED.

[0024] Linear LED drivers have the disadvantage that the voltage drop and operating current of the LED result in power loss. This is simply converted into heat, reducing the LED's efficiency. Advantages include active control, simple circuit design, and a low price.

[0025] A switched-mode LED driver operates similarly to a switched-mode power supply. Due to the high switching frequency in the switched-mode LED driver, energy can be transferred from the input to the output with minimal losses. Switched-mode LED driver ICs exhibit very high efficiencies, well over 90%.

[0026] This allows the connected LED to operate efficiently at its ideal operating point. A disadvantage of switched-mode LED drivers is the increased circuitry required for necessary interference suppression measures. This type of driver is therefore primarily suitable for high-power LED lamps and is consequently one of the most expensive options.

[0027] LED vehicle taillights, which have lower power outputs compared to LED vehicle headlights, typically use linear LED drivers.

[0028] For the sake of completeness, it should be mentioned that LEDs may also require additional electronic control circuits. Examples of these are: for regulating and / or controlling the brightness or luminosity of the LEDs, for example by pulse-width modulated (PWM) switching of the power supply for pulsed operation outside the range perceptible to the human eye, for compensating or avoiding electromagnetic interference, for example constructed from capacitors and / or ferrites, for protecting the LEDs, for example from an overvoltage of the vehicle electrical system or from incorrect polarity, for example comprising one or more Zener diodes.

[0029] A modern LED driver for automotive applications already includes an electronic control circuit for LED failure detection. It features at least: It features a vehicle electrical system connection for power supply via connection to a vehicle's electrical system, a control signal input for applying a control signal to the LED driver to control a lighting function, a constant current LED output switchable by means of a control signal applied to the control signal input, and an LED failure signal output for outputting a failure signal. Furthermore, it can include a PWM generator for fixed or variable adjustment of the light emission of the one or more LEDs connected to the constant current LED output, and thus the brightness of the lighting function they perform.

[0030] Multi-channel LED drivers for automotive applications are also known, which, potentially utilizing synergy effects, correspond to a number of LED drivers equal to the number of channels. Multi-channel LED drivers can include a programmable control unit to implement, for example, specific, recurring light sequences, such as a welcome light sequence when unlocking a vehicle, by means of a sequence of switching operations for various constant current outputs to which different LEDs fulfilling or contributing to various lighting functions or partial lighting functions are connected or can be connected.

[0031] Providing one illuminating surface for each lighting function is disadvantageous both from a design point of view and with regard to optimizing the installation space and weight of vehicles in general and vehicle lights in particular.

[0032] It is known, for example, to implement the taillight and brakelight functions on the same illuminated area. In this case, the light sources illuminating the area are supplied with a higher current when the brakelight function is required than when the taillight function is required.

[0033] A disadvantage of this so-called bi-function is that when the taillight function is active, the brake light function is only clearly visible if the illuminated area used for the bi-function is constantly observed.

[0034] This results in reduced road safety.

[0035] DE 10 2004 036 137 A1 discloses a light source with multiple LEDs as light sources for two different lighting functions, where the luminous areas intended for their realization overlap in a common luminous area. The light source comprises an LED driver arrangement with separate inputs for control signals to request the two lighting functions. Each input has means for generating its own pulse-width modulated clock signal for exactly one of the two lighting functions. A resistor is arranged between each of the means for generating its own pulse-width modulated clock signal and an output. The LEDs or LED strings consisting of several LEDs arranged in series are connected to the output. The ratio of the two resistors corresponds to the inverse ratio of the respective luminous fluxes of the two lighting functions.

[0036] WO 2021 / 186467 A1 discloses the ability to supply different current levels to LEDs intended for the realization of two lighting functions, depending on the lighting function currently required.

[0037] German patent DE 10 2004 050 655 A1 discloses the ability to connect LEDs or LED strings consisting of several LEDs arranged in series, intended to implement multiple lighting functions of the same light color but different brightness, in parallel to several outputs that can be switched depending on a currently requested lighting function. In practice, however, only one output is active at any given time, which then powers the LEDs. The different brightness levels are generated by pulse-width modulation.

[0038] One of the underlying concepts of the invention is to flank the illuminating surface serving the realization of the bi-function with additional illuminating surfaces, each assigned to only one of the two lighting functions realized by the bi-function. At least one of the additional illuminating surfaces is assigned to one lighting function, and at least one remaining additional illuminating surface is assigned to the other lighting function of the two lighting functions realized by the bi-function.

[0039] One difficulty associated with the use of LEDs is the implementation of the required LED failure detection in this concept underlying the invention.

[0040] This is due to the fact that if the failure of an LED in a lighting function implemented by LEDs is detected, this lighting function must be completely switched off.

[0041] If the two lighting surfaces realizing light functions overlap in an overlapping area comprising a common lighting surface also referred to as a bi-light function lighting surface, it must be ensured that a defective lighting function, in which a failure of an LED has been detected, is switched off on the entire lighting surface intended for its realization, whereas the remaining lighting function can still be activated.

[0042] In order to implement a diagnostic concept for LED failure detection in a vehicle light with a common lighting surface, which is provided for two additional lighting functions, preferably of the same light color but, for example, different luminous intensity, and which, in the case of LEDs as light sources, provides for the deactivation of the LED string implementing the respective lighting function for both the common lighting surface and the possibly additional one or more separate lighting surfaces in the event of a fault, it is necessary to deactivate the common lighting surface only for the lighting function in which the presence of a fault has been diagnosed.

[0043] However, if, in the case of a diagnosed fault in one light function, the remaining light function is requested, it is desirable to continue using the common light surface for the remaining light function, i.e., not to deactivate it.

[0044] This means that the bi-functional light surface is preferably only switched off for both light functions if an LED of the bi-functional light surface is actually defective.

[0045] Analog electronic control circuits that achieve this have limited robustness. Implementation using a microcontroller, on the other hand, is very expensive. Without costly logic controlled by a microprocessor, a robust implementation is currently impossible.

[0046] One object of the invention is to provide a light source with a cost-effective LED control of two light functions of a vehicle light realized by overlapping light surfaces in a bi-light function light surface, which enables robust and reliable operation while simultaneously contributing to increased road safety.

[0047] In particular, the object of the invention is to provide a cost-effective light source with LED failure detection in conjunction with a bi-light function illuminating surface.

[0048] Furthermore, it is an object of the invention to provide a vehicle light equipped with a corresponding light source, which has at least two light functions that overlap in a bi-light function light surface.

[0049] A related objective of the invention can be considered to be the provision of a cost-effective method for operating a light source with LED control of two light functions realized by overlapping light surfaces in a bi-light function light surface for a vehicle light.

[0050] The problem is solved by the features of the independent claim. Advantageous embodiments are described in the claims, the drawings, and the following description, including those pertaining to the drawings.

[0051] A first object of the invention relates to a light source with several LEDs as light sources intended and / or contributing to fulfilling at least two lighting functions of a vehicle light, each realized within an overlapping area of ​​overlapping lighting surfaces forming a common lighting surface. The light source has an LED driver arrangement with integrated LED failure detection for the LEDs connected to each switchable output provided by a switchable constant current source. Each of the lighting functions is thus realized by a lighting surface, which is composed of the common lighting surface and each of its own individual lighting surfaces.

[0052] The LED driver assembly has at least five switchable outputs, each providing a constant current source, and at least two inputs assigned to these switchable outputs. Because of the LEDs connected to them, which are advantageously connected in series as LED strings to adapt to the voltage level, the switchable outputs are also referred to as constant current LED outputs. The inputs assigned to the switchable outputs, which can be connected to a vehicle's control unit, are also called control signal inputs. For example, the LED driver assembly can have as many inputs, each assigned to one of the switchable outputs. Furthermore, the LED driver assembly has a power supply connection, also referred to as a vehicle electrical system connection, and at least one LED failure signal output.

[0053] The LED driver array can comprise several individual LED drivers, also known as single-channel LED drivers. Alternatively or additionally, it can also comprise one or more multi-channel LED drivers.

[0054] The light source advantageously comprises at least one LED driver arrangement with separate inputs for the two lighting functions and several switchable outputs, each representing a preset constant current source, referred to as constant current outputs or LED constant current outputs. At least five outputs are provided. These are: at least one first output providing a first current for the LED string for the LEDs used as light sources of the possibly existing separate illuminating area of ​​one lighting function, at least one second output providing a second current that is twice as high as the first current for the LED string for the LEDs used as light sources of the possibly existing separate illuminating area of ​​the other lighting function, and at least three further outputs, each providing the first current, a first further output, a second further output and a third further output for the LED string for the LEDs used as light sources of the common illuminating area.

[0055] The first output and the three other outputs are each designed as low-current constant current outputs, the second output is designed as a high-current constant current output.

[0056] The first output is connected to the LED string of any existing dedicated lighting surface or lighting function.

[0057] The LED string of any other existing, separate lighting area for the other lighting function is connected to the second output.

[0058] The LED string of the common lighting surface is connected to the three other outputs.

[0059] The outputs are controlled in such a way that when the first light function is requested, the first and the first subsequent output deliver a constant current of the first current strength, and when this current is delivered, a current delivery from the second subsequent output or the third subsequent output is interrupted.

[0060] If the LED string of a dedicated or shared lighting area fails, the first and the first subsequent output are switched off according to a predefined diagnostic concept. This ensures that even when the first lighting function is requested, no current is supplied to the first and the first subsequent output, thus preventing the interruption of current supply to the second or third subsequent output when the second lighting function is requested simultaneously.

[0061] Furthermore, the outputs are controlled in such a way that when the second lighting function is requested, the second output delivers a constant current of the second current strength, and the second and third further outputs each deliver a constant current of the first current strength, which first current strengths add up to the second current strength through the LED string of the common lighting surface.

[0062] It is important to emphasize that if the first lighting function is requested simultaneously with the second lighting function, the current output of either the second or the third output is blocked. This can be interpreted as a priority circuit that applies to a request for the first lighting function.

[0063] In the event of a failure of the LED string of one separate lighting area or the common lighting area, the second as well as the second and the third further outputs are switched off according to the intended diagnostic concept.

[0064] This means that, without any further circuit logic, it is possible to operate the common illuminated area in accordance with the prescribed diagnostic concept.

[0065] By doubling the number of outputs per LED string and supplying two different current levels to the respective outputs assigned to each lighting function, the lighting functions can be operated with three different levels each. A first, weak level at one output with the first, weakest current level, a second level at the other output with the second, doubled current level, and a third level, when both outputs are operated simultaneously, with a third current level that is three times the sum of the current levels of the first and second outputs.

[0066] It is important to emphasize that the invention can be realized by using not just one constant current output and associated control signal input combination for one LED string, which LED driver arrangement comprises several LED drivers and / or a multi-channel LED driver, but several, preferably at least three, in an LED driver arrangement with multiple outputs for connecting each of the LED strings used to illuminate a lighting surface, and which comprises several LED drivers and / or a multi-channel LED driver.

[0067] Further features relate to LED failure detection and diagnosis, and the associated shutdown of the LED string.

[0068] A second object of the invention relates to a vehicle light equipped with such a light source and having at least two lighting functions that overlap in a common lighting area.

[0069] The invention allows the realization of a vehicle light using a method for operating a vehicle light with LEDs as light sources of a luminous surface for realizing at least two light functions of the same light color, but different brightness, with a first luminous surface serving to realize a first light function and comprising a first LED string comprising at least one LED, a second luminous surface serving to realize a second light function and comprising a second LED string comprising at least one LED, and with a common luminous surface serving to realize both the first and the second light functions and comprising a common LED string comprising at least one LED, comprising an LED driver with at least two inputs each serving to supply a request signal for activating light functions and several constant current outputs, wherein: The first LED string is connected to a first constant current output providing a first current, the second LED string to a second constant current output providing twice the first current, and the common LED string to a third, a fourth and a fifth constant current output, each providing the first current. are connected, and when the first light function is requested by a switch-on signal applied to one input, a constant current of the respective current strength is delivered to the first and third outputs; when the second light function is requested by a switch-on signal applied to the remaining input, a constant current of the respective current strength is delivered to the second, fourth and fifth outputs; and when both light functions are requested by switch-on signals applied to both inputs, a constant current of the respective current strength is delivered to the first, second, fourth and fifth outputs.

[0070] It is evident that the invention is realized through a surprising LED driver channel allocation in combination with a very specific parameterization of the LED driver.

[0071] It is also evident that the invention provides a cost-effective and reliable solution for controlling LEDs as light sources within a common illuminating surface, preferably of the same light color but, for example, different brightness, in order to realize at least two different lighting functions.

[0072] In order to apply a diagnostic concept for LED failure detection in a vehicle light with a common lighting surface, which is provided for two additional lighting functions of the same light color but different luminous intensity, which may additionally use separate lighting surfaces, and which, in the case of LEDs as light sources, provides for the deactivation of the LED string realizing the respective lighting function for both the common lighting surface and for the possibly additional one or more separate lighting surfaces in the event of a fault, the invention makes it possible to deactivate the common lighting surface only for the lighting function in which the presence of a fault has been diagnosed.

[0073] If, however, a fault is diagnosed in one lighting function and the remaining lighting function is requested, the invention allows the common lighting surface to continue to be used for the remaining lighting function, i.e., it does not need to be deactivated. Instead, the remaining lighting function can be operated with the constant current provided for it.

[0074] Beyond a complete solution to the given problem, circumventing the disadvantages of the prior art, the advantages include significant cost savings, as no microcontroller is required for implementation. Likewise, no analog circuitry is necessary for implementing the logic. The logic is parameterized within the LED driver. The invention enables a reduction in the number of components required. Furthermore, it offers a technically robust and reliable solution. No additional software is needed in the microcontroller. Fewer analog components, particularly semiconductors, are required for its implementation.

[0075] The vehicle light may have one or a combination of the features described above and / or below in connection with the light source, just as the light source may have and / or implement one or a combination of several features described above and / or below in connection with the vehicle light.

[0076] The light source and / or the vehicle light may alternatively or additionally have one or a combination of several features described in the introduction in connection with the prior art and / or in one or more of the documents mentioned in connection with the prior art and / or in the following description of the embodiments shown in the drawings.

[0077] Additional advantages over the state of the art, beyond the complete solution of the task at hand and / or the advantages mentioned above for the individual features, are listed below.

[0078] The invention is explained in more detail below with reference to exemplary embodiments shown in the drawing. The relative sizes of the individual elements in the figures do not always correspond to their actual sizes, as some shapes are simplified and others are enlarged for clarity in relation to other elements. Identical reference numerals are used for identical or equivalently functioning elements of the invention. Furthermore, for the sake of clarity, only those reference numerals necessary for describing the respective figure are shown in the individual figures. The illustrated embodiments merely represent examples of how the invention can be implemented and do not constitute an exhaustive limitation. The figures are shown schematically: Fig. 1 is a schematic representation of an embodiment of a light source with several LEDs as light sources for two different lighting functions of the same color but different brightness levels, with the lighting areas provided for their realization overlapping in a common lighting area (bi-functional lighting area), including SL n-1 and BL n-1 in Table 1, including the logic table. Fig. 2 is a schematic representation of an embodiment of a light source with several LEDs as light sources for two different lighting functions of the same color but different brightness levels, with the lighting areas provided for their realization overlapping in a common lighting area (bi-functional lighting area), including SL n-1 and BL SLM in Table 2, including the logic table.3. A detail of an embodiment of a light source with a 3-level lighting function, wherein the output designated as channel 1 is for a brightness level at night, the output designated as channel 2 is for a brightness level at dusk, and the two outputs designated as channels 1 and 2 together are for a brightness level during the day.

[0079] A in Fig. 1 , Fig. 2 , Fig. 3 Light source 01, shown in whole or in part, includes: Several LEDs 02 as light sources for two different lighting functions, advantageously of the same light color, but preferably of different brightness, with the luminous areas provided for their realization overlapping in a common luminous area, also referred to as a bi-functional luminous area; at least one LED driver arrangement 03 with separate inputs 04 for control signals for requesting the two lighting functions; and several switchable outputs 05, each representing a preset constant current source, hereinafter referred to as constant current outputs or LED constant current outputs, wherein preferably at least five outputs 05 are provided, to which the LEDs 02, 21, 22, 23 or LED strings of several LEDs 02 of the luminous areas arranged in series are connected, which are assigned to the lighting functions. wherein, in addition to the LEDs 22, 23 connected to their own first and second outputs 54, 55, the LEDs 21 of the common luminous area are connected not only to one, but in parallel to several, preferably three, further outputs 51, 52, 53 simultaneously.

[0080] In other words, in addition to LEDs 22, 23 of separate luminous surfaces located outside the common luminous surface, which are connected to separate first and second outputs 54, 55, at least the LEDs 21 of the common luminous surface are connected to several further outputs 51, 52, 53.

[0081] It is important to emphasize that the invention can be realized by using not just one LED constant current output and associated control signal input combination for one LED string, which LED driver arrangement 03 comprises several LED drivers and / or a multi-channel LED driver, but several, preferably at least three, LED constant current output and associated control signal input combinations for one LED string, also referred to as driver channel, for short.

[0082] An advantageous further development relates to a light source 01 with several LEDs 02 as light sources for two different lighting functions of the same light color but different brightness levels, with the lighting surfaces intended for their realization overlapping in a common lighting surface (bi-functional lighting surface), comprising at least one LED driver arrangement 03 with separate inputs 04 for control signals for requesting the two lighting functions and several switchable outputs 05 representing preset constant current sources, hereinafter referred to as constant current outputs or LED constant current outputs, wherein at least five outputs 05 are provided, to which the LEDs 02 or LED strings of several LEDs 02 of the lighting surfaces arranged in series are connected, wherein: Each of the lighting functions is preferably implemented by a luminous surface, which consists of the common luminous surface and each of its own luminous surfaces, to a first output 54 which at least one LED 22 or the at least one LED string of an optionally existing independent luminous surface of one lighting function is connected, to a second output 55 which at least one LED 23 or the at least one LED string of an optionally existing independent luminous surface of the other lighting function is connected, to three further outputs 51, 52, 53 which at least one LED 21 or the at least one LED string of the common luminous surface is connected, the first output 54 and the three further outputs 51, 52, 53 are each designed as low-current constant current outputs, and the second output 55 is designed as a high-current constant current output,When one lighting function is requested, the first output 54 and the first further output 51 are switched on, and when the first output 54 and the first further output 51 are switched on, the current output of the second further output 52 or the third further output 53 is always interrupted, i.e., for example, both when one lighting function is requested and when the other lighting function is requested simultaneously, and when the other lighting function is requested, the second output 55 and the second further output 52 as well as the third further output 53 are switched on, provided that when one lighting function is requested simultaneously with the first output 54 and the first further output 51 being switched on, the current output of the second further output 52 or the third further output 53 is interrupted.wherein the current output of the second further output 52 or the third further output 53 is interrupted when the first output 54 and the first further output 51 are switched on and the other light function is requested simultaneously, so that the current outputs of the LEDs 21 connected to the low-current further outputs 51, 52, 53 add up to a total current corresponding to the current output of the high-current output (here: the second output 55) when the other lighting function is requested, regardless of whether the first 54 and first further output 51 are switched on or not.

[0083] The light source 01 advantageously comprises at least one LED driver arrangement 03 with separate inputs 04 for the two lighting functions and several switchable outputs 05, each representing a preset constant current source, hereinafter referred to as constant current outputs or LED constant current outputs. At least five outputs are required: at least one low-current output 54 providing a first current for the LED string for the LEDs 22 used as light sources of the optionally existing separate illuminating area of ​​one lighting function; at least one high-current output 55 providing a second current, preferably twice as high as the first current, for the LED string for the LEDs 23 used as light sources of the optionally existing separate illuminating area of ​​the other lighting function; and at least three low-current outputs 51, 52, 53, each providing the first current, a first further output 51, a second further output 52, and a third further output 53 for the LED string for the LEDs 21 used as light sources of the common illuminating area. planned.

[0084] The outputs 05 are controlled in such a way that when the first light function is requested, the first 54 and the first further output 51 deliver a constant current of a first, low current strength, and a current output of the second further output 52 or the third further output 53 is always blocked when the first 54 and first further output 51 are switched on.

[0085] Furthermore, outputs 05 are controlled in such a way that when the second lighting function is requested, the second output 55 delivers a constant current of a second, high current strength, and the second 52 and the third further output 53 each deliver a constant current of the first current strength, which first current strengths add up to the second current strength through the LED string of the common lighting area.

[0086] It is important to emphasize that if the first lighting function is requested simultaneously with the second lighting function, and the first output 54 and the first additional output 51 are switched on, the current output of either the second output 52 or the third additional output 53 is blocked, i.e., interrupted, even if the second output 52 and the third additional output 53 are switched on by the request for the other lighting function. This can be interpreted as a priority circuit that applies to a request for the first lighting function.

[0087] When one lighting function and the other lighting function are requested simultaneously, the following occurs in the Fig. 1 The requirement shown in Table 1 stipulates that when one lighting function is requested, the current output of the second additional output 52 or the third additional output 53 is blocked (channel 3, assigned to the third additional output 53, is set to 0 mA if another lighting function, configured as a taillight SL, is requested simultaneously with the requested brake light BL). In this case, the first additional output 51 outputs a constant low current, which then adds to the constant low current of the unblocked, remaining third 53 or second additional output 52 to form a constant high current.

[0088] It is important to emphasize at this point that the statements made previously regarding an interruption or blocking of the current output of the second further output 52 or the third further output 53 when the first output 54 and the first further output 51 are switched on can initially be interpreted as meaning that the rule of interrupting or blocking the current output of the second further output 52 or the third further output 53 applies when the first light function is requested.The specific formulation depending on whether the first output 54 and the first further output 51 are switched on is significant with regard to a preferred embodiment of the invention described below. This embodiment is connected to LED failure detection and a diagnostic concept, specifically the associated deactivation of the first output 54 and the first further output 51 in the event of a failure of the LED 02 or the LED string of a separate illuminating surface 22 or the common illuminating surface 21. This configuration not only provides for a dependency on a requirement of the lighting functions, but also prescribes a deactivation of outputs for the diagnostic concept in the event of a detected LED failure, which is independent of the requirement of lighting functions.This is necessary, for example, to be able to perform a prescribed shutdown of one lighting function when a failure of an LED 22 of one of the separate lighting surfaces of one lighting function is detected, without affecting the common lighting surface when the other lighting function is being implemented.

[0089] For the sake of completeness, it should be mentioned that the terms "one light function", "another light function", "a separate light surface" and "another separate light surface" are synonymous with the terms "first light function", "second light function", "first separate light surface" and "second separate light surface" used elsewhere in this document.

[0090] To enable LED failure detection, the light source 01 advantageously includes, for example, LED failure detection means integrated into the LED driver assembly 03. In this context, the light source can have an LED failure signal output.

[0091] The invention therefore comprises a previously described light source 01 with several LEDs 02 as light sources intended and / or contributing to fulfilling at least two lighting functions of a vehicle light, each of which overlaps within an overlapping area of ​​a common lighting surface, also referred to as a bi-functional lighting surface. The light source 01 has an LED driver assembly 03 with LED failure detection preferably integrated into the LED driver assembly 03 for the LEDs 02, 21, 22, 23 connected to each LED constant current output provided by a switchable constant current source.

[0092] Advantageously, according to a planned diagnostic concept, if a failure of an LED 22 or an LED string of its own lighting area or of an LED 21 or an LED string of the common lighting area is detected, the first output 54 and the first further output 51 are switched off.

[0093] According to the intended diagnostic concept, if a failure of an LED 23 or an LED string of the other own illuminating surface or of an LED 21 or an LED string of the common illuminating surface is detected, the second output 55 as well as the second further output 52 and the third further output 53 are also switched off.

[0094] This means that, without any further circuit logic, it is possible to operate the common illuminated area in accordance with the prescribed diagnostic concept.

[0095] It is evident that this subject matter of the invention is characterized by a Fig. 2 The illustrated light source 01 with several LEDs 02 as light sources for two different lighting functions can be realized in a common lighting surface (bi-functional lighting surface), comprising the common lighting surface and two separate LEDs 02, 21, 22, 23 each serving only one of the two lighting functions, or LED strings consisting of several LEDs 02 arranged in series, an LED driver arrangement 03 with: separate control signal inputs 04 for the two lighting functions requesting control signals, at least five switchable LED constant current outputs assigned to the control signal inputs, each providing a constant current source, and integrated LED failure detection for the LEDs 21, 22, 23 connected to each LED constant current output provided by a switchable constant current source.

[0096] Such a light source 01 is characterized by at least one first LED constant current output providing a first current, to which the LEDs 22 of the separate illuminating area assigned to one lighting function are connected, at least one second LED constant current output providing a second current twice as high as the first current, to which the LEDs 23 of the other separate illuminating area assigned to the other lighting function are connected, and at least three further LED constant current outputs, each providing the first current, a first further LED constant current output, a second further LED constant current output and a third further LED constant current output, to which the LEDs 21 of the common illuminating area assigned to both lighting functions are all connected simultaneously in parallel, where the LED constant current outputs are as shown in Table 2 in Fig. 2 are represented in such a way that: When one lighting function is requested, the first output 54 and the first further output 51 deliver a constant current of the first current strength, and when the first output 54 and the first further output 51 are switched on, the current output of the second further output 52 or the third further output 53 is interrupted and thus blocked, and when the other lighting function is requested, the second output 55 delivers a constant current of the second current strength and the second further output 52 and the third further output 53 each deliver a constant current of the first current strength, which first current strengths add up to the second current strength through the LEDs 21 of the common lighting surface.wherein, when an additional lighting function is requested simultaneously, the first output 54 and the first further output 51 are switched on and current output from the second further output 52 or the third further output 53 is blocked, and the first currents of the two further outputs 51, 52, 53 that are active in this case, namely the continuous first further output 51 and the second further output 52 or the first further output 51 and the third further output 53, add up to a total current corresponding to the second current when the other lighting function is requested, regardless of whether the first lighting function is requested or not, and wherein, upon detection of a failure of an LED 21,22 of one lighting function, the first output 54 and the first further output 51 are switched off, and thus a current output of the second further output 52 or the third further output 53 is continuous and unblocked even when one lighting function is requested, and the first currents of the two further outputs 52, 53 active in this case, namely the continuous second further output 52 and the third further output 53, add up to a total current corresponding to the second current when the other lighting function is requested, regardless of whether one lighting function is requested or not.

[0097] Furthermore, the light source 01 can advantageously have or include a vehicle electrical system connection integrated, for example, into the LED driver arrangement 03.

[0098] The LED driver assembly 03 therefore has at least five switchable outputs 05, each providing a constant current source, and at least two inputs 04 assigned to the switchable outputs. The switchable outputs 05 are also referred to as LED constant current outputs because of the LEDs 02 connected to them, which are advantageously connected in series as LED strings to adapt to the voltage level. The inputs 04 assigned to the switchable outputs 05, which can be connected to a vehicle control unit, are also referred to as control signal inputs. For example, the LED driver assembly 03 can have as many inputs 04, each assigned to one of the switchable outputs 05.Furthermore, the light source 01, for example the LED driver arrangement 03, has a connection for power supply, also called a vehicle electrical system connection, intended for connection to a vehicle electrical system, and optionally at least one LED failure signal output.

[0099] The LED driver arrangement 03 can comprise several individual LED drivers, also known as single-channel LED drivers. Alternatively or additionally, it can also comprise one or more multi-channel LED drivers.

[0100] One in Fig. 3 The advantageous further development of the light source 01 shown provides that the LED driver arrangement 03 of the light source has twice the number of outputs 05 for the LEDs 21, 22, 23 or LED strings assigned to the individual illuminating surfaces and the common illuminating surface, wherein the LEDs 21, 22, 23 of the illuminating surfaces are connected, in addition to the first output 54, the second output 55 and the three further outputs 51, 52, 53, to which they are already connected, to respective double outputs 57, each of which delivers its own current, for example higher, preferably twice, or for example weaker, preferably half, than the respective single outputs 56, in order to operate the lighting functions, for example, depending on the viewing distance and / or ambient brightness, with, for example, three different brightness levels each.

[0101] By doubling the number of outputs 05 per LED string and supplying two different current strengths to the respective outputs 56 and 57 assigned to each lighting function, the lighting functions can be operated with three different brightness levels. A first, weak level at one output (e.g., a single output 56) with the first, weakest current strength; a second level at the other output (e.g., a dual output 57) with the second, doubled current strength; and a third level, when both outputs 56 and 57 are operated simultaneously, with a third current strength that is three times the sum of the current strengths of the first and second outputs 56 and 57.

[0102] Such a light source 01 advantageously has at least one brightness level control signal input 06.

[0103] The LED driver assembly 03 of the light source 01 advantageously comprises one or more linear LED drivers. These are cost-effective electronic assemblies with a reasonably high efficiency, i.e., acceptable power loss, particularly in rear light applications.

[0104] The LED driver arrangement 03 of the light source can alternatively or additionally include one or more PWM generators (PWM; Pulse Width Modulation) for regulating and / or controlling the brightness or luminosity of the LEDs 02 by means of pulse-width modulated clocking of the power supply for pulsed operation outside the range perceptible to the human eye.

[0105] The PWM generator, or rather the PWM generators, are advantageously operated in push-pull mode at the low-current outputs 51, 52, 53, 54, 56, which add up to a high current.

[0106] Basically, there are two ways to generate a high current from high-current LEDs when both lighting functions are required simultaneously for bright light output: Firstly, the currents of, for example, two low-current outputs connected to the same LEDs can be added when the affected low-current outputs are switched on simultaneously, both with and without a PWM generator. Secondly, if a PWM generator is present, the power supplies of the affected low-current outputs can be clocked in opposite directions such that the current pulses of one low-current output fall within the pauses between successive current pulses of the other low-current output.

[0107] Both measures increase the light emission, i.e. the brightness of the LEDs 02 connected to both affected low-current outputs 51, 52, 53, 54, 56.

[0108] A second object of the invention relates to a vehicle light equipped with such a light source 01, having at least two lighting functions that overlap in a common lighting area.

[0109] For example, this is a vehicle light with a light interior at least partially enclosed by a light housing with at least one light opening and a light lens closing this opening, and at least one light source contained therein comprising several LEDs 02 as light sources for at least two light functions of the vehicle light realized when looking from outside the light interior at the light lens or through it by means of overlapping light surfaces in at least one common light surface (bi-functional light surface), comprising a light source 01 as described above.

[0110] The vehicle light is preferably designed as a rear light for a motor vehicle.

[0111] The invention allows the realization of a vehicle light using a method for operating a vehicle light with LEDs as light sources of a luminous surface for realizing at least two light functions of the same light color, but different brightness, with a first luminous surface serving to realize a first light function and comprising a first LED string comprising at least one LED, a second luminous surface serving to realize a second light function and comprising a second LED string comprising at least one LED, and with a common luminous surface serving to realize both the first and the second light functions and comprising a common LED string comprising at least one LED, comprising an LED driver with at least two inputs each serving to supply a request signal for activating light functions and several constant current outputs, wherein: The first LED string is connected to a first constant current output providing a first current, the second LED string to a second constant current output providing twice the first current, and the common LED string to a third, a fourth and a fifth constant current output, each providing the first current. are connected, and when the first light function is requested by a switch-on signal applied to one input, a constant current of the respective current strength is delivered to the first and third outputs; when the second light function is requested by a switch-on signal applied to the remaining input, a constant current of the respective current strength is delivered to the second, fourth and fifth outputs; and when both light functions are requested by switch-on signals applied to both inputs, a constant current of the respective current strength is delivered to the first, second, fourth and fifth outputs.

[0112] Further advantageous embodiments of such a method are evident from the preceding description of the control of the outputs 05 of the LED driver arrangement 03 of the light source 01. This allows a light signature with bi-function, for example tail light / brake light (SL / BL), to be implemented cost-effectively.

[0113] The bi-function here is an LED string that can be operated, for example, at taillight and brake light levels.

[0114] Bi-functions, such as taillight (SL) and brakelight (BL), implemented on a bi-functional lighting surface flanked by dedicated light-emitting surfaces, are increasingly in demand. These functions are combined using dedicated SL and / or BL LEDs 22, 23. In particular, specific logic is required for implementing diagnostic behavior, depending on the diagnostic concept. To avoid using costly and unreliable analog circuitry or an additional intelligent component such as a microcontroller, a specific channel assignment and parameterization of an LED driver arrangement 03 is used to implement the necessary logic for the diagnostic behavior.

[0115] One possible diagnostic concept is as follows: SL is subject to the so-called n-1 criterion, which states that if one SL LED string fails, the remaining SL LED strings should remain activated. BL is subject to Single Lamp Mode (SLM), which states that if one BL string fails, all other BL strings should also be deactivated. The same concept applies to the Bi-function LED strings. Furthermore, for the Bi-function, if one BL string fails and SL is requested, the Bi-function should remain activated with an SL level. This additional complexity can be achieved through a specific electronic circuit connecting the LED strings to the LED driver, as well as through the parameterization of the intelligent LED drivers, which ultimately reflects the inventive feature.

[0116] This specific electronic configuration of the LED driver assembly 03 consists, firstly, in the fact that not only one LED driver channel is used to control an LED 21 or an LED string of the bi-functional lighting surface, but, depending on the diagnostic concept, two or more driver channels are used in parallel. The LED driver assembly 03 is parameterized such that the driver channels for the corresponding bi-functionality are activated or deactivated depending on the requested lighting function. The prioritization of the switching signals SL / BL is also relevant here, as explained below.

[0117] Essential for the LED driver assembly 03 is the ability to operate it in so-called stand-alone mode. This means that the LED driver assembly 03 has a signal input to process the information "activation SL" and "activation BL". Ideally, the activation of SL or BL can be prioritized relative to each other. Preferably, the LED driver assembly 03 has one or more diagnostic groups internally to ideally allow a freely configurable portion of the LED driver channels to operate in single-lamp mode (SLM) or multi-lamp mode (n-1 criterion). Preferably, the currents of the respective LED driver channels can be individually parameterized.

[0118] Furthermore, a 3-level lighting function can be implemented using multiple driver channels for an LED string, as shown in the following. Fig. 3 explained in more detail.

[0119] A developmental challenge is implementing the diagnostic / failure detection concept, especially for the dual-function lighting, as this requires a certain level of logic / intelligence. For example: If a fault is detected in the other lighting function (e.g., brake light function BL) that cannot be compensated for by the remaining LEDs available for the other lighting function, then all BL LEDs must be deactivated (so-called Single Lamp Mode - SLM). This also necessitates that the dual-function lighting area be deactivated. However: If a lighting function SL (e.g., tail light function SL) is requested, then the dual-function lighting area should be reactivated with the corresponding SL light or brightness level.

[0120] This if-error logic "then off, but if SL is requested then on (IF-Else)" can currently be implemented either with an expensive microcontroller, or with a large analog circuit comprising several transistors and / or diodes, resulting in an expensive and not very robust concept.

[0121] The invention provides a surprising and cost-effective solution for implementing this if-error logic.

[0122] In Fig. 1 and the one related to Fig. 1 Table 1 shows a bi-function light source 01 that fulfills a so-called n-1 criterion for one light function designed as a taillight function, abbreviated taillight SL, and another light function designed as a brakelight function, abbreviated brakelight BL.

[0123] For example, pure SL should be operated at 10mA and pure BL at 20mA. Furthermore, the bi-functional LED string in the illuminated area should draw 10mA when SL is requested, 20mA when BL is requested, and also 20mA when both SL and BL are requested. Both functions are subject to the n-1 criterion. Thus, if one LED string fails, the other LED strings of the function remain active.

[0124] To implement the bi-function, three driver channels provided by the additional outputs 51, 52, 53 are required for each bi-function illuminated area in this embodiment. For pure SL or pure BL, only one driver channel is required, provided by the first output 54 or the second output 55, respectively (see figure). Fig. 1 .

[0125] The switching signals from SL and BL are schematically represented on the input side via inputs 04 IN 0 and IN 1 respectively. IN 0 has a higher priority than IN 1.

[0126] The parameterization of the LED driver arrangement 03 is such that when the SL is activated via IN 0, 10mA flows through driver channels 1 and 4, corresponding to the first output 51 and the first output 54, for example. Thus, pure SL and bi-function have the required SL current level.

[0127] If only BL is requested, 10mA each flows through driver channel 2 and driver channel 3, corresponding to the second output 52 and the third output 53, and 20mA flows through driver channel 5, corresponding to the second output 55. Pure BL thus has a current of 20mA, and the combined current for the Bi function is also 20mA. The BL level is reached.

[0128] When SL and BL are requested, 10 mA flows through driver channels 1, 3, and 4, corresponding to the first additional output 51, the third additional output 53, and the first output 54, respectively, and 20 mA flows through driver channel 5, corresponding to the second output 55. This results in a total current of 20 mA for LED 21 and the LED string of the bi-functional light panel: 10 mA for SL and 20 mA for BL. Since SL is requested and has a higher priority than BL, 0 mA flows through driver channel 2, corresponding to the second additional output 52. The current output of the second additional output 52 is then interrupted if SL is requested simultaneously with BL.

[0129] Regarding failure behavior, no SLM (Selective Light Management) is defined for the n-1 criterion. In the event of an LED failure, the remaining LED strings of the respective lighting function remain illuminated.

[0130] In Fig. 2 and the one related to Fig. 2 Table 2 shows a bi-function light source 01 with a so-called n-1 criterion for one light function designed as a taillight function, abbreviated taillight SL, and SLM for another light function designed as a brakelight function, abbreviated brakelight BL.

[0131] This embodiment behaves like the previous embodiment with regard to driver channel assignment and current setting. The difference lies in the diagnostic setting of the LED driver assembly 03. Here, the corresponding BL driver channels are grouped into a diagnostic group and operated in the SLM.

[0132] As shown in Table 2, driver channels 2, 3, and 5, corresponding to the second additional output 52, the third additional output 53, and the second output 55, are combined in the diagnostic group (Diag. Group) BL. If one BL LED string fails, the remaining BL LED strings are deactivated. In particular, LED 21, or rather the LED string of the bi-functional illuminated area, behaves as required by deactivating the BL-relevant driver channels. However, if SL is also requested, the SL level of 10 mA is still reached. The same correct behavior is achieved even if one bi-functional string were to exhibit a fault.

[0133] In Fig. 3 and the one related to Fig. 3 Table 3 shows a light source 01 that fulfills a 3-level light function.

[0134] In Fig. 3 This diagram illustrates a possible configuration of a 3-level lighting function. The three levels refer to the three adjustable brightness or light levels, for example, to adjust the light intensity for day / twilight / night. Two driver channels are preferably used for this purpose, corresponding to a single output 56 and a dual output 57. One driver channel, corresponding to the single output 56, drives a low current for the night level. The other driver channel, corresponding to the dual output 57, drives a medium current for the twilight level. If both driver channels, corresponding to both the single output 56 and the dual output 57, are activated simultaneously, the currents are added, and the day level is achieved. Optionally, the driver channels can be assigned to a diagnostic group for operation in the SLM (Selective Light Management).

[0135] The 3-level lighting function is preferably implemented with one LED driver, particularly preferably within the LED driver arrangement 03. However, it would also be conceivable to implement the 3-level lighting function, or generally a multi-level lighting function, with two or more LED drivers or using one or more multi-channel LED drivers.

[0136] The light source 01, like the vehicle light, can alternatively or additionally have individual or a combination of several features mentioned in the introduction in connection with the state of the art and / or in one or more of the documents mentioned in relation to the state of the art and / or in the description below.

[0137] The invention can alternatively or additionally be realized by or in connection with a method which may include individual or combinations of the features described for the light source 01 and / or the vehicle light and / or method steps realizing and / or realized by these.

[0138] The invention is particularly applicable in the field of the manufacture of vehicle lights, especially motor vehicle lights.

[0139] The invention has been described with reference to preferred embodiments. However, it is conceivable to a person skilled in the art that modifications or changes to the invention can be made without departing from the scope of protection of the following claims. Bezugszeichenliste

[0140] 01 Light source 02 LED 03 LED driver assembly 04 Input 05 Output 06 Brightness level control signal input 21 LEDs of the common light-emitting surface, 22 LEDs of one separate light-emitting surface, 23 LEDs of the other separate light-emitting surface 51 first additional output 52 second additional output 53 third additional output 54 first output 55 second output 56 single output 57 double output

Claims

1. An illuminant (01) comprising a plurality of LEDs (02) as illuminating light sources of their own luminous surfaces and of a common luminous surface for two different light functions with overlap of the luminous surfaces provided in the common luminous surface (bi-function) to realise these light functions, comprising at least one LED driver arrangement (03) with separate inputs (04) for control signals in order to request the two light functions and with a plurality of switchable outputs (51, 52, 5, 54, 55) each constituting preset constant-current sources, to which the plurality of LEDs (02) or LED strips of a plurality of LEDs (02) arranged in series are connected, wherein the LEDs (21) of the common luminous surface are connected in parallel to a plurality of outputs (51, 52) of the switchable outputs, wherein each of the light functions is realised by a luminous surface, which is composed of the common luminous surface and in each case one luminous surface of the own luminous surfaces.

2. The illuminant according to claim 1, wherein: - at least one first LED (22) of the plurality of LEDs of one of the own luminous surfaces of the one light function is connected to a first output (54) of the switchable outputs, - at least one second LED (23) of the plurality of LEDs of another own luminous surface of the other light function is connected to a second output (55) of the switchable outputs, - the LEDs (21) of the plurality of LEDs of the common luminous surface are connected to three further outputs (51, 52, 53) of the switchable outputs, - the first output (54) and the three further outputs (51, 52, 53) are each designed as low-current-energised constant-current outputs, and the second output (55) is designed as a high-current-energised constant-current output, - the first (54) and the first further output (51) are switched on when the one light function is requested, and a current output of the second further output (52) or of the third further output (53) is always interrupted when the first (54) and the first further output (51) are switched on, and - the second output (55) and the second (52) and the third further output (53) are switched on when the other light function is requested.

3. An illuminant according to claim 1 or 2, wherein the illuminant comprises means for LED failure detection.

4. The illuminant according to claim 3, wherein the first (54) and the first further output (51) are switched off upon detection of a failure of an LED (22, 21) of the one own luminous surface or of the common luminous surface, and the second and the second and third further outputs are switched off upon detection of a failure of an LED (23, 21) of the other own luminous surface or of the common luminous surface.

5. The illuminant according to one of the previous claims, wherein the illuminant comprises an on-board power supply.

6. The illuminant according to one of the previous claims, wherein the LED driver arrangement (03) comprises a plurality of single-channel LED drivers.

7. The illuminant according to one of the previous claims, wherein the LED driver arrangement (03) comprises one or more multi-channel LED drivers.

8. The illuminant according to one of the previous claims, with a double number of outputs (05) for the LEDs (02) or LED strips assigned to the own luminous surfaces and to the common luminous surface, wherein, in order to operate the light functions with different brightness levels, the LEDs (02, 21, 22, 23) of the luminous surfaces, in addition to already being connected to the single outputs (56) comprising the first output (54), the second output (55) and the three further outputs (51, 52, 53), are also connected to particular double outputs (57), each of which emits an own current other than the particular single outputs (56).

9. The illuminant according to claim 8, wherein the illuminant has at least one brightness level control signal input (06).

10. The illuminant according to one of the previous claims, wherein the LED driver arrangement (03) comprises one or more linear LED drivers.

11. The illuminant according to one of the previous claims, wherein the LED driver arrangement (03) comprises one or more PWM generators (PWM: pulse width modulation).

12. The illuminant according to claim 11, wherein the PWM generator is operated in push-pull mode for the outputs (51, 52, 53, 54, 56) energised with low currents that add up to a high current.

13. A vehicle lamp, with a lamp interior that is at least partially enclosed by a lamp housing with at least one light opening and with a light lens closing this light opening, and with at least one illuminant (01) accommodated therein and comprising a plurality of LEDs (02, 21, 22, 23) as light sources for at least two light functions of the vehicle lamp realised on the basis of luminous surfaces overlapping in at least one common luminous surface (bi-function), comprising an illuminant (01) according to one of the preceding claims.

14. The vehicle lamp according to claim 13, wherein the vehicle lamp is designed as a tail lamp for a motor vehicle.

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