Lighting device for vehicle interior lighting

Abstract

The disclosure relates to a lighting device (100) for vehicle interior lighting, comprising: at least one dimmable light source (105); a current driver (104) for supplying the at least one dimmable light source (105) with a control current (106), with which the at least one light source (105) assumes a brightness corresponding to the control current (106); and a microcontroller (103) which, in response to a dimming request signal (102), is designed to determine a dimming value (107) for dimming the at least one light source (105) and to transmit said dimming value to the current driver (104), wherein the current driver (104) is designed to set the control current (106) for supplying the at least one light source (105) in response to the dimming value (107) so that the at least one light source (105) assumes a brightness corresponding to the dimming value (107), and wherein the microcontroller (103) is designed to determine the dimming value (107) as a new dimming value (107) on the basis of a current dimming value (107b) and a dimming value change (107c), the dimming value change (107c) being based on the dimming request signal (102).

Description

[0001] LIGHTING DEVICE FOR VEHICLE INTERIOR LIGHTING

[0002] Technical area

[0003] The present invention relates to the field of vehicle illumination, in particular to ambient lighting and vehicle interior lighting using light-emitting diodes (LEDs) and other light sources. In particular, the invention relates to a lighting device for vehicle interior lighting and a method for dimming a lighting device for vehicle interior lighting.

[0004] State of the art

[0005] Ambient and functional lighting in vehicle interiors is often dimmable. In order for the human eye to perceive a dimming process as uniform and continuous, the luminous intensity of the lighting must be changed logarithmically. This is technically achieved by changing the electrical current through the light source logarithmically. Generating this logarithmic control and storing the logarithmic characteristic curve on the microcontroller requires a high amount of memory. Calculating the logarithmic characteristic curve using the power law on the microcontroller requires a high amount of computing power and a high

[0006] In addition, these known implementations have the disadvantage that at low light levels and limited resolution of the brightness levels, no

[0007] Brightness changes on the LED are visible, and therefore the user does not receive direct feedback from the lighting system. Description of the invention

[0008] An object of the invention is therefore to create an advantageous concept for dimmable lighting of the vehicle interior with which the above-mentioned disadvantages can be overcome.

[0009] In particular, it is an object of the invention to provide a dimmable vehicle interior lighting which requires little computing and memory resources and can reliably perform dimming so that changes in brightness on the LED can be perceived by the user even at low light intensity.

[0010] The object is achieved by the subject matter of the independent claims. Advantageous developments of the invention are specified in the dependent claims, the description, and the accompanying figures.

[0011] The invention generates this logarithmic control with particularly little memory and computing effort in the control circuit (control IC) of the lighting.

[0012] The inventive solution is based on the concept presented below.

[0013] The control IC receives the dimming request from the user externally. Using the dimming routine, it calculates a time-varying brightness signal, which is used in the downstream current driver to power an LED. This dimming routine is particularly efficient because it can iteratively calculate the future value from the current value and, in particular, avoids computationally intensive multiplication and exponentiation. Memory required to store the entire characteristic curve on the microcontroller is not required here. With low-cost microcontrollers used as control ICs, memory and computing power are limited.

[0014] The new dimming routine avoids the computationally intensive evaluation of the power law by simplifying the algorithm by using only addition, subtraction, and bitshifting as operators, while avoiding computationally intensive multiplication and exponentiation. Furthermore, the new dimming routine is designed so that the change in light intensity during the dimming process is always large enough to be perceptible, allowing the lighting to always respond directly to the user request with a change in light intensity. With precise calculations using the logarithmic law and limited PWM accuracy, this is not always the case in conventional systems, as rounding is required for control on a real microcontroller. This leads to the logarithmic characteristic curve, which is implemented on a microcontroller, producing no brightness changes at the controlled LED at the beginning of the dimming process.

[0015] The dimming routine presented here does not have this disadvantage. The characteristic curve of the dimming routine deviates slightly from the exact logarithmic behavior, which the human eye cannot consciously detect. The exact logarithmic behavior can, for example, be expressed in the form be displayed.

[0016] The dimming routine presented here can be easily applied to all LEDs and lighting products dimmed using PWM or linear constant current control. This enables the use of smaller and more cost-effective microcontrollers. The dimming routine presented here saves memory and computing power compared to conventional control circuits.

[0017] In addition, the solution presented here has the advantage that brightness changes on the LED are visible even at low light intensity, thus providing the user with direct feedback from the lighting system.

[0018] According to a first aspect of the invention, the above-described object is achieved by a lighting device for vehicle interior lighting, comprising: at least one dimmable light source; a current driver for supplying the at least one dimmable light source with a control current, with which the at least one light source assumes a brightness corresponding to the control current;and a microcontroller configured to determine a dimming value for dimming the at least one light source in response to a dimming request signal and to transmit it to the current driver, wherein the current driver is configured to adjust the control current for supplying the at least one light source in response to the dimming value so that the at least one light source assumes a brightness corresponding to the dimming value, wherein the microcontroller is configured to determine the dimming value as a new dimming value based on a current dimming value and a dimming value change, wherein the dimming value change is based on the dimming request signal;

[0019] Such a lighting device offers the technical advantage of saving memory and computing power compared to conventional dimming devices. This enables the use of smaller and more cost-effective microcontrollers. The dimming routine implemented in the microcontroller and shown above, in which the new dimming value is determined based on the current dimming value and a dimming value change, is particularly efficient because it can iteratively calculate the future value from the current value. Memory requirements for saving the entire characteristic curve on the microcontroller are not required here. The new dimming routine avoids the computationally intensive evaluation of the power law by simplifying it by using only addition and subtraction and bit shifting as operators, but avoiding computationally intensive multiplication and exponentiation.

[0020] According to an exemplary embodiment of the lighting device, the microcontroller is designed to determine, when the dimming request signal is present, a new dimming value which differs from the current dimming value and which causes a change in the brightness of the at least one light source which is perceptible in particular by a user.

[0021] This provides the technical advantage that even at low light intensity, a perceptible change in brightness is visible at at least one light source, thus providing the user with direct feedback from the lighting device.

[0022] According to an exemplary embodiment of the lighting device, the dimming value follows a non-logarithmic temporal progression.

[0023] This achieves the technical advantage that, unlike with the logarithmic curve, where low light intensity or small dimming values ​​result in a slight change in brightness per dimming step. Due to rounding and / or resolution limitations on the microcontroller, this leads to the same dimming value being maintained over several steps and the dimming process is therefore not noticeable to the user, the non-logarithmic curve does not have such adverse effects. Each dimming step leads to a change in brightness that is noticeable to the user. The non-logarithmic curve can, for example, represent a section-by-section linear approximation to the logarithmic curve, where each linear section leads to a change in brightness.

[0024] According to an exemplary embodiment of the lighting device, the dimming value change is based on an addition or subtraction and a bit shift.

[0025] This provides the technical advantage of saving memory and computing power when only addition, subtraction, or shift operations need to be performed. This allows the microcontroller to be smaller and more cost-effective.

[0026] According to an exemplary embodiment of the lighting device, the dimming value change comprises integer changes of the dimming value in a positive or negative direction.

[0027] This has the advantage that both dimming up and dimming down can be achieved and that there is a change in brightness in each dimming step.

[0028] According to an exemplary embodiment of the lighting device, the microcontroller is configured to determine the dimming value change based on the current dimming value and one or more predetermined dimming value parameters.

[0029] This provides the advantage that, due to the predefined parameters, no unknowns need to be determined, for example, based on solving equations or systems of equations. The dimming value parameters are known, and only one equation is required to determine the new dimming value from the old dimming value and the known dimming value parameters. This makes determining the new dimming value very simple, allowing the microcontroller to be simple and, in particular, requires less memory and computing power than conventional microcontrollers used in dimming devices.According to an exemplary embodiment of the lighting device, the microcontroller is configured to determine the dimming value change and the new dimming value based on the following relationships: As(t) = a - ((b - dimming value(t)) » c), Dimming value(t+1) = Dimming value(t) ± As(t), where “dimming value(t)” denotes the current dimming value, “dimming value(t+1)” denotes the new dimming value, “As(t)” denotes the current dimming value change and “a”, “b” and “c” denote the predetermined dimming value parameters and where “»” denotes a shift to the right by a number of c bits, (t) denotes the current magazine or dimming step, (t+1) represents the subsequent or new magazine or dimming step.

[0030] This offers the advantage that the calculation can be performed during the microcontroller's runtime. In particular, it allows for faster calculation of the PWM step by avoiding exponentiation of the current PWM step, and memory space can be saved by avoiding storing the entire logarithmic characteristic and large floating-point numbers.

[0031] According to an exemplary embodiment of the lighting device, the parameter a corresponds to a predetermined maximum global brightness change between two dimming steps, the parameter b lies in a range of a predetermined maximum dimming value, and the parameter c lies in a range around the value c = Iog2(b / a).

[0032] For example, the parameter b can be in a range from 50% to 100%, preferably in the range from 80% to 100%, of the specified maximum dimming value. For example, the parameter c can be in a range from 50% to 150%, preferably in the range from 80% to 120%, of the above-mentioned value, c = Iog2(b / a).

[0033] This offers the advantage that the three dimming value parameters are easy to determine. For example, it is sufficient to know the maximum dimming value and the maximum global brightness change between two dimming steps to determine the three dimming value parameters.

[0034] According to an exemplary embodiment of the lighting device, the at least one light source comprises one or more light-emitting diodes. This offers the advantage that light-emitting diodes are now used in many vehicle applications, offer high luminosity, and are cost-effective to manufacture.

[0035] According to an exemplary embodiment of the lighting device, the current driver is designed to adjust the control current for supplying the at least one light source based on pulse width modulation, PWM, wherein a proportion of an on-phase of the PWM to a total time is determined by the dimming value.

[0036] This offers the advantage of easily regulating the power of loads such as LEDs and other light sources. Instead of controlling these components via the operating voltage and / or current, pulse-width modulation simply interrupts the voltage or current for a short period of time. This creates a specific ratio between voltage pulses and pauses, which can be used to adjust the brightness of the light source.

[0037] According to an exemplary embodiment of the lighting device, the current driver is configured to adjust the control current for supplying the at least one light source according to a linear constant current control, and wherein an amplitude of the control current is based on the dimming value.

[0038] This offers the advantage of providing a simple alternative to power regulation using PWM. Analog dimming can thus be implemented efficiently using an analog circuit, for example, using a regulated current source that can be easily constructed. For example, operational amplifiers and other analog circuit elements that are inexpensive to manufacture can be used for this purpose. Another advantage over PWM implementation is flicker-free lighting, which can be achieved with this approach.

[0039] According to an exemplary embodiment of the lighting device, the dimming request signal comprises a start signal or a stop signal, and the microcontroller is configured to continuously determine new dimming values ​​when the start signal is present and to leave the dimming value unchanged when the stop signal is present. This offers the advantage that the lighting device can be operated easily and efficiently by the user. They only need to enter the start signal and wait until the brightness approaches the desired value, then activate the stop signal.

[0040] According to an exemplary embodiment of the lighting device, the start signal indicates dimming in a positive direction or in a negative direction; and the microcontroller is configured to determine the new dimming value based on the current dimming value and a positive dimming value change when dimming in a positive direction is indicated; and to determine the new dimming value based on the current dimming value and a negative dimming value change when dimming in a negative direction is indicated.

[0041] This offers the advantage that the microcontroller can efficiently execute the iterative dimming routine. This allows both dimming up and down to be performed efficiently.

[0042] According to an exemplary embodiment of the lighting device, the dimming request signal comprises information about a proportional brightness value with respect to a maximum brightness of the at least one light source, and the microcontroller is designed to determine the dimming value in accordance with the proportional brightness value.

[0043] This offers the advantage that the lighting device can be operated easily and efficiently by the user. They only need to enter the proportional brightness value, and the microcontroller executes the iterative dimming routine until the desired brightness value is reached. Of course, the user can also enter an absolute brightness value or another method of entering the desired brightness instead of the proportional brightness value.

[0044] According to an exemplary embodiment of the lighting device, the lighting device is configured to receive the dimming request signal externally via a switch, a push-button, a user interface with a display, or via a signal line. Alternatively, the lighting device has an integrated sensor system configured to detect a user input by means of a push-button, a switch, an integrated proximity sensor system, a touch sensor system, and / or a force sensor system and to convert it into the dimming request signal.

[0045] This offers the advantage of high flexibility for detecting the dimming request signal.

[0046] According to a second aspect of the invention, the above-described object is achieved by a method for dimming a lighting device for vehicle interior lighting, comprising at least one dimmable light source and a current driver for supplying the dimmable at least one light source with a control current, with which the at least one light source assumes a brightness corresponding to the control current, wherein the method comprises the following steps: determining a dimming value for dimming the at least one light source; transmitting the dimming value to the current driver; adjusting the control current for supplying the at least one light source by the current driver in response to the dimming value, such that the at least one light source assumes a brightness corresponding to the dimming value; wherein the determination of the new dimming value is based on a current dimming value and a dimming value change, wherein the dimming value change is based on a dimming request signal.

[0047] Such a method offers the same advantages as the lighting device described above. This means that memory space and computing power can be saved compared to conventional dimming methods, enabling the use of smaller and more cost-effective microcontrollers. The dimming routine, in which the new dimming value is determined based on the current dimming value and a dimming value change, is particularly efficient because it can iteratively calculate the future value from the current value. Therefore, memory requirements for saving the entire characteristic curve are not required. The new dimming routine avoids the computationally intensive evaluation of the power law by a simplification that uses only addition and subtraction and bit shifting as operators, but avoids computationally intensive multiplication and exponentiation.

[0048] According to a third aspect of the invention, the object is achieved by a computer program with program code for executing the method according to the second aspect on a lighting device according to the first aspect. This achieves the technical advantage that the computer program can be easily executed on a lighting device, e.g., the microprocessor and the current driver of the lighting device.

[0049] Short character description

[0050] The invention is described in more detail below using exemplary embodiments and the figures. They show:

[0051] Fig. 1a is a schematic representation of the structure of an inventive

[0052] Lighting device 100 for vehicle interior lighting;

[0053] Fig. 1b is a schematic representation of the structure of an inventive

[0054] Lighting device 100 for vehicle interior lighting, in which the current driver is integrated in the microcontroller;

[0055] Fig. 2 shows a dimming curve 202 according to the invention in comparison with a conventional dimming curve 201; and

[0056] Fig. 3 is a schematic representation of a method 300 according to the invention for dimming a lighting device 100 for vehicle interior lighting.

[0057] The figures are merely schematic representations and serve only to illustrate the invention. Identical or equivalent elements are provided with the same reference numerals throughout.

[0058] In the following detailed description, reference is made to the accompanying drawings, which form a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. It is understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope of the present invention. The following detailed description, therefore, is not to be taken in a limiting sense. Further, it is to be understood that the features of the various embodiments described herein may be combined with one another unless specifically indicated otherwise.

[0059] The aspects and embodiments are described with reference to the drawings, where like reference numerals generally refer to like elements. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of one or more aspects of the invention. However, it may be apparent to one skilled in the art that one or more aspects or embodiments may be practiced with a lesser level of specific detail. In other instances, well-known structures and elements are shown in schematic form to facilitate describing one or more aspects or embodiments. It is understood that other embodiments may be utilized and structural or logical changes may be made without departing from the concept of the present invention.

[0060] The present disclosure describes PWM or linearly dimmed light sources, in particular LEDs and OLEDs (organic LEDs).

[0061] A light-emitting diode (LED) is a semiconductor device that emits light when an electric current flows in the forward direction. In the opposite direction, the LED blocks current. Thus, the electrical properties of the LED correspond to those of a diode. The wavelength of the emitted light depends on the semiconductor material and the diode's doping: The light can be visible to the human eye or in the infrared or ultraviolet range.

[0062] Pulse-width modulation (PWM) is also known as pulse width modulation (PBM), pulse duration modulation (PDM), or pulse length modulation (PLM). Pulse-width modulation (PWM) is a digital modulation method in which a technical quantity (e.g., electrical voltage) alternates between two values. A rectangular pulse is modulated at a constant frequency, with its width, or length, varying. The ratio between the pulse and the pause is called the duty cycle.

[0063] With pulse width modulation, the modulated signal has a fixed amplitude. The pulse duration depends on the amplitude of the information signal. The larger the information signal, the longer the pulse. Although the pulse width modulation signal is an alternating voltage, or rather a mixed voltage, it can be used to regulate the power of direct current consumers such as LEDs and other light sources. Instead of controlling these components via the operating voltage, pulse width modulation interrupts the voltage or current for a short time. This creates a specific ratio between current pulses and pauses. This ratio determines the effective current and thus the brightness of the light source.

[0064] This disclosure describes PWM drivers and, more generally, current drivers used in dimming. With a PWM driver, the LED luminous flux, or more generally the luminous flux of the light source, is adjusted by changing the ON / OFF duty cycle of a square wave signal. The frequency of a dimming PWM can, for example, be in the range of approximately 100 Hz, preferably in the range between 300 Hz and 1000 Hz or even higher, to avoid the stroboscopic effect when switching the light source on and off.

[0065] Other dimming methods can be used instead of PWM, such as linear constant current dimming. This can be achieved by using a regulated current source that operates using operational amplifiers and other analog circuit elements.

[0066] Fig. 1a shows a schematic representation of the structure of a lighting device 100 according to the invention for vehicle interior lighting.

[0067] The lighting device 100 comprises at least one dimmable light source 105; a current driver 104 for supplying the at least one dimmable light source 105 with a control current 106, with which the at least one light source 105 emits a luminous flux corresponding to the control current 106 and thus assumes a corresponding brightness; and a microcontroller 103.

[0068] The microcontroller 103 is configured to determine a dimming value 107 for dimming the at least one light source 105 in response to a dimming request signal 102 and to transmit it to the current driver 104. The current driver 104 is configured to adjust the control current 106 for supplying the at least one light source 105 in response to the dimming value 107, so that the at least one light source 105 assumes a brightness corresponding to the dimming value 107.

[0069] The microcontroller 103 is configured to determine the new dimming value 107 based on a current dimming value 107b and a dimming value change 107c, wherein the dimming value change 107c is based on the dimming request signal 102.

[0070] The microcontroller 103 can be configured to determine, when the dimming request signal 102 is present, a new dimming value 107 which differs from the current dimming value 107b and which causes a change in the brightness of the at least one light source 105, which is perceptible in particular by a user 101.

[0071] For example, the dimming value 107 may follow a non-logarithmic time course, in particular a sectionally linear approximation to a logarithmic time course.

[0072] The dimming value change 107c can, for example, be based on an addition and / or subtraction and / or shift operation. This allows the new dimming value at time (t+1) to be easily determined from the current dimming value at time (t) and the dimming direction. Only simple arithmetic operations such as addition and subtraction as well as bit shift operations are necessary. The microcontroller 103 can be very simply constructed for this purpose and does not require a large memory or significant computing power. For example, three memory cells are sufficient to store the three parameters a, b, and c, instead of the multitude of N memory cells for each support point when evaluating the logarithmic curve.

[0073] In an alternative embodiment, as shown in Figure 1 b, the current driver 104 can be integrated in the microcontroller 103.

[0074] The dimming value change 107c can, for example, comprise integer changes to the dimming value 107 in a positive or negative direction. In the positive direction, a dimming up is generated, and in the negative direction, a dimming down. The microcontroller 103 can be configured to determine the dimming value change based on the current dimming value 107b and one or more predetermined dimming value parameters. These dimming value parameters determine how the new dimming value is determined from the current dimming value. The dimming value parameters can be previously determined fixed parameters that are known when determining the new dimming value or stored in a constant memory. Although the dimming value parameters are fixed parameters, they can be updated during a system upgrade if necessary.

[0075] A preferred variant of the lighting device 100 is presented in more detail below.

[0076] The microcontroller 103 may be configured to determine the dimming value change 107c, for example, based on the following relationship:

[0077] As(t) = a - ((b - Dimming value(t)) » c), where “Dimming value(t)” denotes the current dimming value 107, “As(t)'' denotes the dimming value change 107c and “a”, “b” and “c” denote the predefined dimming value parameters and where “»” denotes a shift to the right by a number of c bits.

[0078] The parameter a can correspond to a specified maximum global brightness change between two dimming steps. The parameter b can be within a range of a specified maximum dimming value. The parameter c can be within a range around the value c = Iog2(b / a).

[0079] For example, the parameter b can be in a range from 50% to 100%, preferably in the range from 80% to 100%, of the specified maximum dimming value. For example, the parameter c can be in a range from 50% to 150%, preferably in the range from 80% to 120%, of the above-mentioned value, c = Iog2(b / a).

[0080] The at least one light source 105 can, for example, comprise one or more light-emitting diodes (LEDs). The at least one light source 105 can further comprise other types of light sources, such as incandescent lamps, fluorescent lamps, halogen lamps, glow lamps, laser diodes, lasers, OLEDs, electroluminescent films, etc.

[0081] The current driver 104 may be configured to adjust the control current 106 for supplying the at least one light source 105 based on pulse width modulation, PWM, wherein a proportion of an on-phase of the PWM to a total time is determined by the dimming value 107.

[0082] Alternatively, the current driver 104 can be configured to linearly adjust the control current 106 for supplying the at least one light source 105. The amplitude of the control current 106 can be based on the dimming value 107.

[0083] The dimming request signal 102 can include a start signal and / or a stop signal. The microcontroller 103 can be configured to determine a new dimming value 107 when the start signal is present and to leave the dimming value 107 unchanged when the stop signal is present.

[0084] The lighting device 100 may be configured to receive the dimming request signal 102 externally via a switch, a push button, a user interface with a display, or via a signal line.

[0085] Alternatively, the lighting device may have an integrated sensor system, which may be configured to detect a user input by means of a button, a switch, an integrated proximity sensor system, a touch sensor system and / or a force sensor system and to convert it into the dimming request signal 102.

[0086] Thus, the dimming request signal 102 can be detected by various means.

[0087] In one embodiment of the lighting device 100, the dimming request signal 102 can be input or actuated by the user 101. Thus, the lighting device 100 can include a pressure-sensitive area where the user can make their inputs, e.g., enter the start signal for the dimming process and / or the stop signal for the dimming process. Alternatively, another input device can be attached to the lighting device with which the user 101 can make their inputs for dimming.

[0088] Alternatively, the lighting device 100 may have an input interface with which the lighting device 100 can receive the dimming request signal 102, for example via cable or wirelessly.

[0089] The start signal can, for example, indicate dimming in the positive direction or dimming in the negative direction.

[0090] The microcontroller 103 can be configured to determine the new dimming value 107 based on the current dimming value 107b and a positive dimming value change 107c when dimming in the positive direction is indicated; and to determine the new dimming value 107 based on the current dimming value 107b and a negative dimming value change 107c when dimming in the negative direction is indicated.

[0091] The dimming request signal 102 can, for example, include information about a proportional brightness value relative to a maximum brightness of the light source 105, and the microcontroller 103 can be configured to determine the dimming value 107 according to the proportional brightness value. Thus, the microcontroller 103 can, for example, allow the iterative dimming process described above to continue until the brightness of the light source 105 reaches the proportional brightness value of the maximum brightness. The same applies to a dimming process in a changed brightness direction.

[0092] Here, too, the dimming request signal 102 can be input or actuated by the user 101. Thus, the lighting device 100 can comprise an input device similar to the screen of a smartphone, by means of which the user can enter the proportional brightness value. Alternatively, as described above, the proportional brightness value can also be received via an interface from another device, for example, from a control panel in the cockpit of the vehicle, via which the user 101 can make their inputs.

[0093] The user's dimming request can preferably be transmitted via a switch, a push-button, a UI (user interface) with a display (etc.), or directly to the lighting device 100 using a push-button, switch, integrated proximity sensor, touch sensor, and / or force sensor. The dimming request signal 102 can thus be transmitted externally to the lighting device 100, or the lighting device 100 can detect the user input itself using integrated sensor technology and thereby generate the dimming request.

[0094] In the following, various embodiments of the dimming routine for controlling at least one light source, in particular an LED, are described.

[0095] The control during the dimming process of an LED can be achieved using PWM (pulse width modulation). The LED is switched on and off at a high frequency. The current during the "on" phase is constant. This is perceived by the human eye as reduced brightness, with the proportion of the LED's "on" phase in relation to the total time reflecting the proportional brightness of the maximum brightness. The control takes place at the output of a microcontroller. A second variant is linear constant current dimming of the LED. In this case, the current is changed directly and adjusted between off and maximum current during the dimming process. The algorithm presented here can be used for both variants.

[0096] The calculation algorithm for controlling the LED presented here is an iterative process. The previous value is used to calculate the next value in the dimming routine. The calculation is performed using the following relationship:

[0097] Dimming value (t+1) = Dimming value (t) ± As (t), where the dimming value reflects the brightness of the LED at one point in time, and As describes the brightness change at the next point in time during the dimming process. When dimming up, an addition occurs, while when dimming down, a subtraction occurs. The brightness change As can be determined as follows:

[0098] As (t) = a - ((b - dimming value(t)) » c) Here, a, b and c are constant and a corresponds to the maximum change in brightness between two time steps, b is in the range of the maximum dimming value and c is in the range log 2 (b / a). The operator "" describes a shift to the right by c bits.

[0099] The dimming value and the brightness change are integer values. The calculation algorithm for a dimming routine with a 10-bit integer (maximum value 1023) is shown in Figure 1a.

[0100] The calculation takes place during the runtime of the microcontroller 103 and offers the following advantages:

[0101] 1. Faster calculation of the PWM step by avoiding exponentiation of the current PWM step.

[0102] 2. Saving memory space by avoiding storing the entire logarithmic characteristic curve and by avoiding storing large floating-point numbers.

[0103] The dimming routine ensures that As > 1. This means that the brightness is incremented in each dimming step. This is not necessarily achieved with the classic logarithmic characteristic curve with a limited set of discrete values ​​(see Figure 2). This property of the algorithm offers the additional advantage that the user experiences a brightness change in each step. This improves the user experience.

[0104] Fig. 2 shows a dimming curve 202 according to the invention in comparison to a conventional dimming curve 201.

[0105] The two dimming curves 201, 202 differ in that they calculate the current PWM value differently. In the inventive dimming curve 202, the calculation is performed using a simple approximation with initial modification. In the classic logarithmic characteristic curve 201, the calculation is performed by determining the logarithmic or exponential time profile, which requires computational and memory-intensive processing.

[0106] Using the above-mentioned dimming parameters a, b, and c, dimming curve 202 is obtained. Dimming curve 202 is an example dimming curve for a 10-bit PWM. This means that parameter b is equal to 1023 or lies within a range of 1023, for example, 50% to 100% or preferably 80% to 100% of 1023, because the number of bits for a 10-bit PWM is equal to (2 to the power of 10) minus 1, i.e., equal to 1023.

[0107] The dimming parameter a corresponds to the maximum brightness change between two dimming levels. The two dimming steps that result in a maximum brightness change are the last two dimming steps according to Figure 2, i.e., dimming steps 216 and 217 in the example shown in Figure 2. Dimming curve 202 shows a change in the PWM value, i.e., the brightness, of a=16.

[0108] The third dimming parameter c is determined from a and b by the following relationship: c = Iog2 (b / a) = Iog2 (1024 / 16) = 8 or lies within a range around this value, for example, within 50% to 150% or preferably 80% to 120% around this value. It is understood that Figure 2 merely shows an exemplary dimming curve 202. For other PWM drivers, other dimming parameters a, b, and c result.

[0109] Fig. 3 shows a schematic representation of a method 300 according to the invention for dimming a lighting device 100 for vehicle interior lighting.

[0110] The method 300 serves to dim a lighting device 100 for vehicle interior lighting, having at least one dimmable light source 105 and a current driver 104 for supplying the at least one dimmable light source 105 with a control current 106, with which the at least one light source 105 assumes a brightness corresponding to the control current 106, as described above for Figure 1a, for example.

[0111] The method 300 comprises determining 301 a dimming value 107 for dimming the at least one light source 105, as described above for Figure 1a, for example.

[0112] The method 300 includes transmitting 302 the dimming value 107 to the current driver 104, as described above for Figure 1a, for example.

[0113] The method 300 comprises adjusting 303 the control current 106 for supplying the at least one light source 105 by the current driver 104 in response to the dimming value 107, so that the at least one light source 105 assumes a brightness corresponding to the dimming value 107, wherein the determining 301 of the new dimming value 107 is carried out based on a current dimming value 107b and a dimming value change 107c, wherein the dimming value change 107c is based on a dimming request signal 102, for example as described above with reference to Figure 1a.

[0114] Furthermore, a computer program with a program code for carrying out the method 300 on a lighting device with a microcontroller and a current driver, as described above, for example, can be provided.

[0115] LIST OF REFERENCE SYMBOLS

[0116] 100 lighting devices

[0117] 101 users

[0118] 102 Dimming request, dimming request signal

[0119] 103 Microcontroller or microprocessor

[0120] 104 power drivers or hardware drivers

[0121] 105 at least one light source, LED

[0122] 106 Control current for controlling the brightness of at least one light source

[0123] 107 new or next or future dimming value at time t+1

[0124] 107b current dimming value at time t

[0125] 107c Dimming value change

[0126] 201 conventional dimming curve

[0127] 202 dimming curve according to the invention

[0128] 300 Method for dimming a lighting device

[0129] 301 first step: Determine dimming value

[0130] 302 second step: Transfer dimming value

[0131] 303 third step: Setting control current

Claims

PATENT CLAIMS 1. Lighting device (100) for vehicle interior lighting, comprising: at least one dimmable light source (105); a current driver (104) for supplying the at least one dimmable light source (105) with a control current (106) with which the at least one light source (105) assumes a brightness corresponding to the control current (106);and a microcontroller (103) configured to determine a dimming value (107) for dimming the at least one light source (105) in response to a dimming request signal (102) and to transmit it to the current driver (104), wherein the current driver (104) is configured to adjust the control current (106) for supplying the at least one light source (105) in response to the dimming value (107) so that the at least one light source (105) assumes a brightness corresponding to the dimming value (107), wherein the microcontroller (103) is configured to determine the dimming value (107) as a new dimming value (107) based on a current dimming value (107b) and a dimming value change (107c), wherein the dimming value change (107c) is based on the dimming request signal (102).

2. Lighting device (100) according to claim 1, wherein the microcontroller (103) is configured to determine a new dimming value (107) when the dimming request signal (102) is present, which differs from the current dimming value (107b), and which causes a change in the brightness of the at least one light source (105), which is particularly perceptible to a user (101).

3. Lighting device (100) according to claim 2, wherein the dimming value (107) follows a non-logarithmic temporal progression.

4. Lighting device (100) according to one of the preceding claims, wherein the dimming value change (107c) is based on addition and / or subtraction as well as a bit shift.

5. Lighting device (100) according to one of the preceding claims, wherein the dimming value change (107c) comprises integer changes of the dimming value (107) in a positive or negative direction.

6. Lighting device (100) according to one of the preceding claims, wherein the microcontroller (103) is configured to determine the dimming value change based on the current dimming value (107b) and one or more predetermined dimming value parameters.

7. Lighting device (100) according to claim 6, wherein the microcontroller (103) is configured to determine the dimming value change (107c) and the new dimming value (107) based on the following relationships: As(t) = a - ((b - Dimmwert(t)) » c), Dimmwert(t+1) = Dimmwert(t) ± As (t), where “Dimmwert(t)” denotes the current dimming value (107b), “Dimmwert(t+1)” denotes the new dimming value (107), “As(t)'' denotes the dimming value change (107c) and “a”, “b” and “c” denote the specified dimming value parameters and where “»” denotes a shift to the right by a number of c bits.

8. Lighting device (100) according to claim 6 or 7, wherein the parameter a corresponds to a predetermined maximum global brightness change between two dimming steps, the parameter b lies in a range of a predetermined maximum dimming value, and the parameter c lies in a range around the value c = Iog2(b / a).

9. Lighting device (100) according to one of the preceding claims, wherein the current driver (104) is configured to adjust the control current (106) for supplying the at least one light source (105) based on pulse width modulation, PWM, wherein a proportion of an on-phase of the PWM to a total time is determined by the new dimming value (107).

10. Lighting device (100) according to any one of claims 1 to 8, wherein the current driver (104) is configured to adjust the control current (106) to supply the at least one light source (105) according to a linear constant current control, and wherein an amplitude of the control current (106) is based on the dimming value (107).

11. Lighting device (100) according to one of the preceding claims, wherein the dimming request signal (102) comprises a start signal or a stop signal and wherein the microcontroller (103) is configured to determine the new dimming value (107) when the start signal is present and to leave the current dimming value (107b) unchanged when the stop signal is present.

12. Lighting device (100) according to claim 11, wherein the start signal indicates dimming in a positive direction or in a negative direction; and wherein the microcontroller (103) is configured to determine the new dimming value (107) based on the current dimming value (107b) and a positive dimming value change (107c) when dimming in a positive direction is indicated; and to determine the new dimming value (107) based on the current dimming value (107b) and a negative dimming value change (107c) when dimming in a negative direction is indicated.

13. Lighting device (100) according to one of the preceding claims, wherein the dimming request signal (102) comprises information about a partial brightness value with respect to a maximum brightness of the at least one light source (105) and wherein the microcontroller (103) is configured to determine the new dimming value (107) according to the partial brightness value; and / or wherein the at least one light source (105) comprises one or more light-emitting diodes.

14. Lighting device (100) according to one of the preceding claims, which is configured to receive the dimming request signal (102) externally via a switch, a push button, a user interface with a display, or via a signal line; or which has integrated sensors configured to detect user input by means of a push button, a switch, an integrated proximity sensor, or a touch sensor. To detect sensory and / or force sensory input and convert it into the dimming request signal (102).

15. Method (300) for dimming a lighting device (100) for vehicle interior lighting, comprising at least one dimmable light source (105) and a current driver (104) for supplying the at least one dimmable light source (105) with a control current (106) by which the at least one light source (105) assumes a brightness corresponding to the control current (106), wherein the method comprises the following steps: Determining (301) a dimming value (107) to dim the at least one light source (105); Transfer (302) of the dimming value (107) to the current driver (104); Setting (303) the control current (106) to supply the at least one light source (105) by the current driver (104) in response to the dimming value (107), so that the at least one light source (105) assumes a brightness corresponding to the dimming value (107); wherein determining (301) a new dimming value (107) is based on a current dimming value (107b) and a dimming value change (107c), wherein the dimming value change (107c) is based on a dimming request signal (102).

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