Lighting circuit for an automotive lighting device generating

Abstract

One aspect of the present invention relates to a lighting circuit for an automotive lighting device, the lighting circuit comprising a plurality of light sources configured to generate a luminous flux level, an integrated circuit configured to supply a drive current to bias a luminous flux level of at least one light source of the plurality of light sources, and a compensation circuit connected with the integrated circuit. The compensation circuit is configured to adjust an intensity of a current driving at least one light source of the plurality of light sources, a level of the current adjustment depending on a detected temperature change of the at least one light source of the plurality of light sources. The luminous flux level is maintained within a range of luminous flux levels based on the detected temperature change of at least one of the plurality of light sources.

Description

Technical Field

[0001] The technical field of this invention is automotive lighting.

[0002] The present invention relates to a lighting circuit for an automotive lighting device that generates a constant level of luminous flux independent of temperature, and a method for controlling the luminous flux level generated by at least one of a plurality of light sources. Background Technology

[0003] Automotive lighting encompasses all lighting functions on a motor vehicle, including interior and exterior lighting. Exterior lighting includes front lighting, rear lighting, and turn signals. Headlights are intended to illuminate the road ahead in conditions of reduced visibility (such as at night or in heavy rain or fog), while taillights and turn signals are used for optical communication with other road users to improve safety.

[0004] Commercially available solid-state light-emitting devices, such as light-emitting diodes (LEDs), are commonly used in automotive lighting applications. It is well known that automotive lighting applications typically employ commercially available integrated current drivers. These integrated current drivers force a constant current through the light source over a wide temperature and operating voltage range, allowing for simple and convenient operation of one or more light sources in low-power applications with drive currents ranging from 10 to 150 mA, thus avoiding the complex designs required for discrete components. The current driver regulates the current flowing through the light source. An integrated current driver is a current driver integrated into an integrated circuit. An integrated circuit is a set of electronic circuits on a small, flat piece of semiconductor material (also called a “chip”). Integrated circuits used in automotive lighting applications can include various components such as resistors, negative temperature coefficient thermistors (referred to as NTCs in this application), or positive temperature coefficient thermistors (referred to as PTCs in this application). The use of commercially available components, such as integrated current drivers and / or resistors and / or NTCs and / or PTCs, is an important premise of this invention.

[0005] These commercial light sources exhibit luminous flux thermal dependence, which can be significant. In other words, the level of luminous flux produced by the light source depends on temperature. In this patent application, the term "temperature" is used for the junction temperature and / or ambient temperature of the automotive lighting assembly. Junction temperature refers to the temperature of the active region of the light source. Ambient temperature refers to the temperature surrounding the light source. The operation of the light source, along with other heat sources such as driving electronics and light conversion components, raises the temperature.

[0006] The main mechanism leading to reduced light output efficiency is related to nonradiative recombination via the well-known Shockley-Read-Hall and Auger recombination processes. However, each type of light source has its own specific luminous flux level profile for a given temperature range. In this application, the profile characterizing the luminous flux level produced by the light source according to temperature is referred to as the thermal drift characteristic profile of the light source. The thermal drift characteristic profile of a light source depends on the technology of the light source, especially the semiconductor material used as the active material. For example, light sources such as Nichia™ NFSW172AT use first-generation technology based on gallium nitride (GaN), while light sources such as Dominant™ DWA MKG and Dominant™ DWY MKG use quaternary alloys (Al) based on... x Ga 1–x ) 0.5 In 0.5 P's second-generation technology. Figure 1 Examples of luminous flux produced by three light sources with junction temperatures ranging from -40°C to +70°C and for different current intensities driving the LEDs are shown. Figure 1 As shown, the level of luminous flux generated by the light source also depends on the intensity of the current driving the light source.

[0007] Special attention is paid to maintaining stable luminescence. Light sources in automotive lighting must be designed to comply with the color and brightness limits specified in the application specifications. Specifically, the technical specifications for signal lights (including rear license plate lights, turn signals, position lights, brake lights, rear outline marker lights, reversing lights, turn signals, rear fog lights, parking lights, daytime running lights, and side marker lights) in automotive lighting in UN Economic Commission for Europe (UNECE) member states are detailed in UN Regulation 148 (United Nations Agreement, 3rd edition, amended, on the adoption of the unified United Nations technical regulations applicable to wheeled vehicles, and the conditions of mutual recognition of approvals granted pursuant to these UN regulations, and the mutual recognition of approvals granted pursuant to these UN regulations). Since the emitted luminous flux and peak wavelength of a light source depend on ambient temperature (E. Fred Schubert, Junction and carrier temperatures, Light-Emitting Diodes, 2nd ed., Cambridge University Press, 2006), some work has focused not only on correcting for junction temperatures but also on luminous flux drift caused by variations in ambient temperature. For example, US Patent US01048507SB2 discloses a system that switches between two discrete currents based on a specific temperature threshold, thereby increasing the bias current of the light source as the temperature rises. French Patent Application FR3096759A1 discloses a system that increases the bias current using discrete values ​​when the luminous flux drops below a threshold. Both systems require a flux detector and logic for switching the bias current in discrete steps. A microcontroller is then included in the design to process the flux measurement and adjust the bias current accordingly. Therefore, these systems are complex and relatively large.

[0008] The following documents are known from the prior art:

[0009] - US2016242254A1, titled "Automotive Lamp Comprising A LED Lighting Device (including LED lighting device for automotive lamps)".

[0010] - US2018302973A1, titled "automotive lamp with compensation of the luminous flux of the light source", and...

[0011] - WO2022268879A1, titled "procédé de fonctionnement d'un dispositif d'éclairage automobile (operation method of automobile lighting device)".

[0012] Therefore, there is a need for a lighting circuit that generates a constant level of luminous flux independent of temperature for efficient automotive lighting devices. Furthermore, this lighting circuit needs to be compact and preferably manufactured using commercially available components. Summary of the Invention

[0013] According to a first aspect of the present invention, the above-mentioned requirement is met by providing a lighting circuit for an automotive lighting device, the lighting circuit comprising:

[0014] - Multiple light sources configured to produce luminous flux levels;

[0015] - An integrated circuit configured to supply drive current to bias the luminous flux level of at least one of a plurality of light sources; and

[0016] - A compensation circuit connected to an integrated circuit, configured to adjust the intensity of the current driving at least one of a plurality of light sources, the level of current adjustment depending on a detected temperature change at the at least one of the plurality of light sources; and

[0017] The luminous flux level is maintained within a range based on the detected temperature change of at least one of the multiple light sources.

[0018] This invention provides a lighting circuit for an automotive lighting device that generates a constant level of luminous flux independent of temperature by using an integrated circuit with a specially designed thermal model. In this application, the term "thermal model" refers to the lighting circuit adjusting the intensity of the current driving the light source according to temperature. A compensation circuit provides input to the integrated circuit. Based on the input from the compensation circuit, the integrated circuit adjusts the intensity of the current driving the light source, compensating for changes in the luminous flux level of the light source due to variations in the temperature of the automotive lighting assembly. The integrated circuit for the designed automotive lighting assembly is specific to the characteristics of LEDs. In particular, the thermal model of this integrated circuit is specific to the thermal drift characteristic curve of the light-emitting diode. Therefore, regardless of the temperature variation of the automotive lighting assembly, the lighting circuit ensures that the luminous flux generated by the light-emitting diode is maintained within a certain luminous flux level range.

[0019] In addition to the features mentioned in the preceding paragraphs, a lighting circuit according to one aspect of the invention may also have one or more of the following additional features, which may be considered individually or in any technically feasible combination:

[0020] - The compensation circuit includes a first resistor connected in series with the sensing circuit;

[0021] - The compensation circuit includes a second resistor and a negative temperature coefficient thermistor, which are connected in parallel.

[0022] - The compensation circuit is configured to adjust the intensity of the current driving at least one of the multiple light sources by adjusting the equivalent resistance value based on the detected temperature change of at least one of the multiple light sources.

[0023] - The equivalent resistance is based at least in part on the multiplication factor of the integrated circuit;

[0024] - The equivalent resistance is based at least in part on the detected temperature change of at least one of the multiple light sources;

[0025] - The compensation circuit enables the integrated circuit to maintain a constant flux and adjust the intensity of the current driving at least one of multiple light sources.

[0026] - When the sensing circuit includes a positive temperature coefficient thermistor, the compensation circuit is adapted to adjust the intensity of the current driving at least one of the multiple light sources.

[0027] A second aspect of the invention relates to a method for controlling the luminous flux level produced by at least one of a plurality of light sources, the method comprising:

[0028] - A thermal drift curve of the luminous flux level generated by at least one of the multiple light sources within a temperature variation range of at least one of the multiple light sources, identified by a compensation circuit, wherein the thermal drift value is determined at a predetermined drive current intensity of the integrated circuit driving at least one of the multiple light sources.

[0029] - An electrical curve, identified by a compensation circuit, showing the luminous flux level produced by at least one of a plurality of light sources within the range of driving current intensity, the electrical curve being determined at a predetermined temperature of at least one of the plurality of light sources.

[0030] - A compensation circuit calculates a compensation curve for the intensity of the driving current required to drive at least one of the multiple light sources within a temperature range using thermal drift and electrical curves. This compensation curve defines the required driving current intensity for each temperature within the temperature range in order to maintain the luminous flux level within the specified range.

[0031] - The compensation circuit calculates an equivalent resistance value for at least one of the multiple light sources at each temperature within the temperature range. This equivalent resistance value is used to adjust the drive current of at least one of the multiple light sources based on the temperature value of at least one of the multiple light sources as defined by the compensation curve.

[0032] - The luminous flux level generated by at least one of multiple light sources is controlled by a compensation circuit.

[0033] The method according to the second aspect of the invention may also have one or more of the following features, which can be considered individually or in any technically feasible combination:

[0034] - After identifying the electrical characteristic curve and before calculating the compensation curve, the method further includes:

[0035] - For each temperature within the temperature range, calculate the adjusted temperature value using the following method:

[0036] - Obtain the temperature value at the pad of at least one of multiple light sources; and

[0037] - Apply the correction factor to the obtained temperature value; and

[0038] - Calculate the adjusted temperature value based on the applied correction factor, which corresponds to the junction temperature of at least one of the multiple light sources.

[0039] A third aspect of the invention relates to an automotive lighting device comprising a housing and a lighting circuit according to the invention.

[0040] A fourth aspect of the invention relates to a computer program comprising instructions for performing the method according to the invention.

[0041] The fifth aspect of the invention relates to a computer-readable storage medium on which a computer program according to the invention is recorded. Attached Figure Description

[0042] Other features and advantages of the invention will become apparent from the description given below by way of example, and not limitation, with reference to the accompanying drawings, in which:

[0043] Figure 1 An example of the luminous flux produced by three LEDs at junction temperatures ranging from -40°C to +70°C and at different current intensities driving the LEDs is shown.

[0044] Figure 2 This is a schematic diagram illustrating an example of the steps of method 100 according to the present invention.

[0045] Figure 3 An example of a compensation circuit with an architecture compatible with the present invention is shown.

[0046] Figure 4 The luminous flux values ​​of three different LED models are shown within a certain temperature range. Detailed Implementation

[0047] For clarity, identical or similar elements in the accompanying drawings are labeled with the same reference numerals. Furthermore, the same variable appearing in different paragraphs has a unique name.

[0048] This invention relates to a lighting circuit for an automotive lighting device. The lighting circuit includes multiple light sources configured to generate a certain level of luminous flux. The lighting circuit also includes an integrated circuit configured to supply a drive current to bias the luminous flux level of at least one of the multiple light sources. The lighting circuit further includes a compensation circuit connected to the integrated circuit. The compensation circuit is configured to adjust the current intensity driving at least one of the multiple light sources. The level of current adjustment depends on a detected temperature change of at least one of the multiple light sources. The lighting circuit is exposed to temperature changes, for example, between -40°C and +70°C. The light sources of the automotive lighting assembly generate luminous flux, the level of which depends on the temperature value of the lighting circuit. The luminous flux level also depends on the current intensity driving the light sources. The compensation circuit adjusts the intensity of the current driving the light sources. The level of current adjustment depends on the temperature value of the lighting circuit. The lighting circuit according to the invention enables a constant luminous flux to be obtained. Regarding "constant luminous flux," it means maintaining the luminous flux level within a range of luminous flux levels, for example, maintaining the flux at a constant level, for example, a variation range of 15%, more preferably 5%. The achievement of constant luminous flux is due to specific features of the compensation circuit. In practice, the compensation circuit adjusts the intensity of the current driving the light source to compensate for changes in the luminous flux level of the light source caused by variations in the temperature of the lighting circuit. In other words, the compensation circuit compensates for adjustments in the luminous flux level caused by temperature changes by precisely tuning the adjustment level of the current driving the light source. The light source can be predetermined, and in this case, the object of the present invention is to design a compensation circuit suitable for a predetermined light source.

[0049] Therefore, to obtain a stable luminous flux, the compensation circuit is designed to adjust the current intensity according to the light source temperature to compensate for the luminous flux drift caused by such temperature changes. As a preliminary approximation, the relationship between the LED's bias current and the intensity of its emitted light can be considered linear (D. Peng and K. Liu, "Modeling Study of Red LED Spectral Characteristics", J. Phys.:Conf. Ser., 1746, 012003, 2021).

[0050] (1)

[0051] in:

[0052] - It is relative luminous flux.

[0053] - It is a proportionality constant.

[0054] - I is the intensity of the current driving the LED.

[0055] The proportionality constant is a parameter specific to each LED model. In fact, this relationship is a simplified model of the LED. Therefore, it is assumed that the luminous flux is linear with the bias current of the component, and therefore it is also assumed that the relationship between flux and current is linear.

[0056] Furthermore, when the bias current is constant, the relative luminous flux It can be expressed as a function of temperature (J. Yan, H. Liu, W. Zhao and Y. Su, “Temperature compensation for LED filament standard lamps”, SPIE Conference Proceedings 11189, Optical Metrology and Inspection for Industrial Applications VI, 111891N, November 18, 2019):

[0057] (2)

[0058] in:

[0059] It is the temperature coefficient of LED.

[0060] It is the junction temperature of the LED.

[0061] It is the reference junction temperature, which is usually 25°C.

[0062] From these two formulas (1) and (2), it can be seen that the luminous flux drift caused by the change in internal temperature can be modeled as the thermal dependence of the bias current:

[0063] (3)

[0064] in It is a constant, representing the intensity of a fixed current.

[0065] Therefore, if the drive system can generate bias current Its behavior, which follows the opposite of the previous formula, can compensate for the thermal drift of the emitted light, that is:

[0066] (4)

[0067] in It is a constant factor, which includes the heat dependence of formula (3).

[0068] By using a compensation circuit to adjust the current driving the light source, the size of the lighting circuit can be minimized. Furthermore, due to the small size of the compensation circuit, it can be positioned close to the light source, thus affecting the temperature changes of both the light source and the compensation circuit similarly. Ensuring that the adjustment of the current driving the light source compensates for the adjustment of the luminous flux level caused by temperature variations is advantageous. Moreover, such a compensation circuit can consist only of commercially available components, such as one or more resistors and / or one or more thermistors.

[0069] The current value can be generated from a commercially available integrated driver (switching or linear system) according to formula (1), such as the Elmos™ 522.8X or Elmos™ 522.9X. Therefore, as... Figure 3 The compensation circuit presented in the paper needs to have a resistor. It is defined as:

[0070] (5)

[0071] in:

[0072] - K is the current amplification factor of the compensation circuit, which is a constant for a given compensation circuit;

[0073] - It is the reference voltage for the compensation circuit;

[0074] - It is a constant factor that includes the temperature dependence of formula (3).

[0075] This means that a variable resistor whose resistance value is exponentially related to temperature can be used in the compensation circuit. In an example, the compensation circuit of the present invention may include a first resistor connected in series with a sensing circuit. In a preferred example, the compensation circuit of the present invention may include a first resistor connected in series with a second resistor. The first resistor is also connected in series with a negative temperature coefficient thermistor (referred to as NTC in this application). The second resistor and the NTC can be considered as the sensing circuit. The second resistor and the NTC are connected in parallel, and the NTC is placed close to the pad of the light source. Regarding "close," it means, for example, between 5 and 30 mm, and preferably between 5 and 15 mm. This distance can be adjusted for a given application if necessary. Thermal simulation also helps to find the optimal location for the component. Figure 3 An example of such a compensation circuit is shown, where R1 is the resistance of the first resistor, R2 is the resistance of the second resistor, and RNTC is the resistance of the NTC. Therefore, Figure 3 The compensation circuit has an equivalent resistance labeled REQ.

[0076] Due to the light source Since the resistance is always negative, NTCs may be suitable devices for compensating for thermal drift in luminous flux. In fact, the nominal resistance of an NTC decreases exponentially with temperature.

[0077] (6) .

[0078] in:

[0079] It is NTC at ambient temperature The resistance below,

[0080] It is NTC at ambient temperature The resistance below,

[0081] B is a constant of NTC.

[0082] As can be seen from equation (6), the thermal dependence of the NTC can be expressed as the reciprocal of temperature. To configure a resistor that varies with temperature in a similar manner to that expressed in equation (6), a resistor such as... Figure 3 The compensation circuit shown. The equivalent resistance of this compensation circuit. Calculated as:

[0083] (7)

[0084] In addition, the internal junction temperature of the light source (denoted as Tj) was obtained experimentally using a commonly used indirect measurement method (J. Bielecki, AS Jwania, F. ElKhatib, and T. Poorman, “Thermal Considerations for LED Components in an Automotive Lamp,” Proceedings of the Twenty-Third Annual IEEE Semiconductor Thermal Measurement and Management Symposium, 2007, pp. 37–43). This method includes measuring the temperature of the pad pins. This is combined with the thermal resistance value expressed in Kelvin / watt provided by the light source manufacturer. Given the operating power P, the junction temperature can be calculated using the following formula:

[0085] (8)

[0086] in:

[0087] It is the junction temperature of the light source.

[0088] It is the temperature of the light source's solder pads.

[0089] It is the thermal resistance of the light source.

[0090] P is the power value.

[0091] In the preferred example of the compensation circuit, the NTC is placed close to the light source pad. Therefore, the ambient temperature T in formula (6) corresponds to the pad temperature in formula (7). In this way, formula (7) can be expressed in terms of junction temperature as:

[0092] (9)

[0093] Appropriate selection , , And the B parameter can lead to The behavior within a certain temperature range is related to the resistance in formula (5). Very close. Regarding "very close," it means... Behavior and resistance The difference in behavior between them is less than 10%. Therefore, a stable luminous flux can be maintained by using an integrated commercial driver to generate a temperature-varying current by introducing a resistor network that includes a thermistor as a resistor shunt.

[0094] Figure 4 The luminous flux values ​​obtained by three different LED models are shown over the temperature range. For each graph, Figure 4 The relative compensated and uncompensated luminous flux levels are shown within a temperature range. "Compensated luminous flux" refers to the use of the compensation circuit according to the invention to compensate for thermal drift of the emitted light. "Uncompensated luminous flux level" refers to the absence of any measures to compensate for thermal drift of the emitted light. Figure 4 The bias current for driving an LED for a luminous flux compensation example is also shown. Figure 4 A, Figure 4 B and Figure 4 C corresponds to the first, second, and third embodiments, respectively. As from... Figure 4 As can be seen, the compensated luminous flux level determined by this invention can remain relatively stable over a wide temperature range. Furthermore, the luminous flux level does not change drastically within this temperature range.

[0095] These three embodiments have the following characteristics: Figure 3 The architecture is shown in the diagram. These three embodiments can be used with commercially available integrated current drivers, such as the Elmos™ 522.82 or Elmos™ 522.92. In the first implementation, the LED is a Dominant DWA MKG™, and the first resistor has a first resistance value R1 of 5 kΩ, the second resistor has a second resistance value R2 of 15 kΩ, and the negative temperature coefficient thermistor has a third resistance value RNTC of 15 kΩ / 3380, a rated current of 50 mA, and a temperature of 50 degrees Celsius. In this first embodiment, the compensated flux change is approximately 4.2%, while the uncompensated flux change is approximately 59.7%.

[0096] In the second embodiment, the LED is a Dominant DWY MKG™, the first resistor has a first resistance value R1 of 1.5 kΩ, the second resistor has a second resistance value R2 of 40 kΩ, and the negative temperature coefficient thermistor has a third resistance value RNTC of 45 kΩ / 3380, a rated current of 50 mA, and a temperature of 50 degrees Celsius. In this second embodiment, the change in compensated flux is approximately 13.1%, while the change in uncompensated flux is approximately 115%.

[0097] In the third embodiment, the LED is a Nichia NFSW172AT™, the first resistor has a first resistance value R1 of 11.5 kΩ, the second resistor has a second resistance value R2 of 4.2 kΩ, and the negative temperature coefficient thermistor has a third resistance value RNTC of 10 kΩ / 3380, a rated current of 50 mA, and a temperature of 50 degrees Celsius. In this third embodiment, the change in compensated flux is approximately 2.2%, while the change in uncompensated flux is approximately 8.2%.

[0098] A second aspect of the invention relates to a method for controlling the luminous flux level generated by at least one of a plurality of light sources.

[0099] Figure 2 This is a schematic diagram illustrating the steps of an example of method 100 according to the present invention. Necessary steps in the example of method 100 are indicated by solid-line rectangles, and optional steps are indicated by dashed-line rectangles.

[0100] The first step 110 of method 100 is to identify, by a compensation circuit device, a thermal drift profile of the luminous flux level produced by at least one of the plurality of light sources within a temperature variation range of at least one of the plurality of light sources. For example, the temperature range may be between -40°C and +70°C. The thermal drift profile must be determined under a predetermined current intensity driving at least one of the plurality of light sources.

[0101] The second step 120 of method 100 is to generate an electrical curve, identified by a compensation circuit, showing the luminous flux level produced by at least one of the plurality of light sources within a range of driving current intensity. For example, the intensity range may be between 10 and 70 mA. The electrical curve must be determined at a predetermined temperature for at least one of the plurality of light sources.

[0102] A third optional step 130 of method 100 is to calculate an adjusted temperature value for each temperature within the temperature range. The adjusted temperature value is calculated by: first, obtaining the temperature value at the pad of at least one of the multiple light sources; second, applying a correction factor to the obtained temperature value; and third, calculating the adjusted temperature value based on the applied correction factor. The adjusted temperature value corresponds to the junction temperature of at least one of the multiple light sources.

[0103] The fourth step 140 of method 100 involves calculating a compensation curve by a compensation circuit for the intensity of the current driving at least one of the multiple light sources within a temperature range of at least one of the multiple light sources. This compensation curve is calculated for the temperature range of the automotive lighting assembly using thermal drift and electrical characteristic curves. The compensation curve defines the required current intensity to drive at least one of the multiple light sources for each temperature within the temperature range, in order to maintain the luminous flux level within the luminous flux level range.

[0104] The fifth step 150 of method 100 involves the compensation circuit calculating an equivalent resistance value for each temperature within the temperature range of at least one of the multiple light sources. The equivalent resistance value is used to adjust the drive current of at least one of the multiple light sources based on the temperature value of at least one of the multiple light sources, as defined by the compensation curve.

[0105] The sixth step 160 of method 100 involves a compensation circuit controlling the luminous flux level generated by at least one of the multiple light sources. By varying the drive current supplied to the multiple light sources, the luminous flux level output from the multiple LEDs can be maintained substantially stable. The integrated circuit can vary the drive current based on the equivalent resistance value provided by the compensation circuit. A suitable equivalent resistance value is determined by the compensation circuit using the thermal model described in the preceding paragraphs.

Claims

1. A lighting circuit for an automotive lighting device, the lighting circuit comprising: - Multiple light sources, which are configured to produce luminous flux levels; - Integrated circuit, configured to supply drive current to bias the luminous flux level of at least one of a plurality of light sources; as well as - A compensation circuit connected to an integrated circuit, the compensation circuit being configured to adjust the intensity of a current driving at least one of a plurality of light sources, the level of current adjustment depending on a detected temperature change of at least one of the plurality of light sources, the compensation circuit comprising: - The first resistor (R1) is connected in series with the sensing circuit. - The sensing circuit includes a second resistor (R2) and a negative temperature coefficient thermistor (NTC), which are connected in parallel. - The negative temperature coefficient thermistor is positioned at a distance of 5 to 30 millimeters from the pads of the light source, and The luminous flux level is maintained within a range based on the detected temperature change of at least one of the multiple light sources.

2. The lighting circuit of claim 3, wherein the compensation circuit is positioned close to the pad of at least one of the plurality of light sources.

3. The lighting circuit according to any one of the preceding claims, wherein the compensation circuit is configured to adjust the intensity of the current driving at least one of the plurality of light sources by adjusting the equivalent resistance (REQ) value based on a detected temperature change of at least one of the plurality of light sources.

4. The lighting circuit of claim 5, wherein the equivalent resistance (REQ) is at least partially based on the multiplication factor of the integrated circuit.

5. The lighting circuit of claim 5, wherein the equivalent resistance (REQ) is at least partially based on a detected temperature change of at least one of the plurality of light sources.

6. The lighting circuit according to any one of the preceding claims, wherein the compensation circuit enables the integrated circuit to maintain a constant supply voltage and adjust the intensity of the current driving at least one of the plurality of light sources.

7. The lighting circuit according to any one of the preceding claims, wherein when the sensing circuit includes a positive temperature coefficient thermistor, the compensation circuit is adapted to adjust the intensity of the current driving at least one of the plurality of light sources.

8. An automotive lighting device, comprising a housing and a lighting circuit according to any one of claims 1 to 9.

9. A method (100) for controlling the luminous flux level produced by at least one of a plurality of light sources, comprising: - A thermal drift curve of the luminous flux level generated by at least one of the multiple light sources within the temperature variation range of at least one of the multiple light sources, identified by the compensation circuit (110), wherein the thermal drift value is determined at a predetermined drive current intensity of the integrated circuit driving at least one of the multiple light sources. - An electrical curve of the luminous flux level generated by at least one of the plurality of light sources within the range of driving current intensity, identified by the compensation circuit (120), wherein the electrical curve is determined at a predetermined temperature of at least one of the plurality of light sources. - The compensation circuit calculates (140) a compensation curve for the intensity of the driving current required to drive at least one of the multiple light sources within a temperature range of at least one of the multiple light sources by using thermal drift curves and electrical curves. The compensation curve defines the intensity of the driving current required to drive at least one of the multiple light sources for each temperature within the temperature range in order to maintain the luminous flux level within the luminous flux level range. - The compensation circuit calculates an equivalent resistance (REQ) value (150) for each temperature within the temperature range of at least one of the multiple light sources. The equivalent resistance (REQ) value is used to adjust the drive current of at least one of the multiple light sources based on the temperature value of at least one of the multiple light sources as defined by the compensation curve. - The luminous flux level generated by at least one of the multiple light sources is controlled by the compensation circuit (160).

10. The method of claim 11, wherein after identifying (120) the electrical characteristic curve and before calculating (140) the compensation curve, the method further comprises: - For each temperature within the temperature range, calculate the adjusted temperature value (130) by means of the following method: o Obtain the temperature value at the pad of at least one of the multiple light sources; as well as o Apply the correction factor to the obtained temperature value; as well as o The adjusted temperature value is calculated based on the applied correction factor, and the adjusted temperature value corresponds to the junction temperature of at least one of the multiple light sources.

11. A computer program comprising instructions for performing the method according to any one of claims 11 to 12.

12. A computer-readable storage medium having the computer program of claim 13 recorded thereon.

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