EP3091819B1 - Method for operating a control unit for a series connection of semiconductor light sources comprising light module and control device - Google Patents

Description

The invention relates to a method according to the preamble of claim 1 and a control device according to a non-independent claim.

The US 2007/159118 A1 discloses a motor vehicle headlamp with a DC voltage source and a diode array having a plurality of light emitting diodes connected in series. The forward voltage of a diode string is measured. Average Vav data is stored. The measured forward voltage and the stored data are used in a comparison. A short circuit is detected.

It is known that a failure of a single light emitting diode of a series circuit of LEDs by monitoring the individual LEDs, for example is detected via light sensors or via a voltage tap of the individual light-emitting diode and the monitoring of the respective signals.

From the DE 101 31 824 A1 a circuit device for the failure detection of light-emitting diodes in a motor vehicle is known in the failure detection means comprise switching means which compare a detected in a light-emitting diode potential with a dependent of a voltage of a vehicle electrical system reference potential and effect depending on this comparison, the output of a corresponding failure detection signal can.

The object of the invention is therefore to improve the error detection.

The object underlying the invention is achieved by a method according to claim 1 and a control device according to an independent claim. Advantageous developments are specified in the subclaims. Features which are important for the invention can also be found in the following description and in the drawings, wherein the features can be important both alone and in different combinations for the invention, without being explicitly referred to again.

By determining the voltage applied to the series circuit and their evaluation sensor is saved on the light module, such as the light sensors and / or voltage measuring sensors. In addition, additional separate measuring lines between the light module and the controller accounts. Thus, in particular, the sensors can be relocated to the controller, which constructs the light modules cheaper and error-prone and can be produced.

In an advantageous embodiment, a compensated actual voltage is determined as a function of a determined actual current through the series connection. This can advantageously be detected a change in the actual current and the actual voltage can be compensated accordingly. In an advantageous embodiment, the compensated actual voltage is determined as a function of a determined actual temperature of the semiconductor light sources. Thus, the compensated actual voltage can advantageously be determined temperature-compensated.

In an advantageous embodiment, the error is detected when the compensated actual voltage is outside a first limit around the reference voltage. This advantageously creates a tolerance range for detecting the error.

In a further advantageous embodiment, the error is detected when the compensated actual voltage is at several measuring times of the measured actual voltage outside the first limit to the reference voltage. This advantageously achieves that the detection of the error is done on a secure database.

In an advantageous embodiment, the reference voltage is then updated as a function of the compensated actual voltage when the compensated actual voltage is within a second limit around the reference voltage. In order for a drift compensation is advantageously created, which in particular a component aging and a compensation of the component tolerance is created.

In an advantageous embodiment, the reference voltage is determined as an exponentially smoothed value from a plurality of compensated actual voltages. This also compensates for component drift and component tolerance. In particular, by this drift compensation or component tolerance compensation, the error detection can be significantly improved.

Other features, applications and advantages of the invention will become apparent from the following description of embodiments of the invention, which are illustrated in the figures of the drawing. All described or illustrated features, alone or in any combination form the subject matter of the invention, regardless of their summary in the claims or their dependency and regardless of their formulation or representation in the description or in the drawing. The same reference numbers are used for functionally equivalent quantities and features in all figures, even in different embodiments.

Figur 1

eine schematisch dargestellte Beleuchtungseinrichtung für Kraftfahrzeuge;

Figur 2

ein schematisches Schaltbild;

Figuren 3 bis 5

jeweils ein schematisches Blockdiagramm; und

Figur 6

ein schematisch dargestelltes Spannungs-Zeit-Diagramm.

Hereinafter, exemplary embodiments of the invention will be explained with reference to the drawings. In the drawing show

FIG. 1

a schematically illustrated illumination device for motor vehicles;

FIG. 2

a schematic diagram;

FIGS. 3 to 5

each a schematic block diagram; and

FIG. 6

a schematically illustrated voltage-time diagram.

In FIG. 1 a lighting device for motor vehicles is designated in its entirety by the reference numeral 1. The lighting device 1 is formed in the illustrated embodiment as a motor vehicle headlight. Of course, the lighting device 1 as a lamp or the like, which is arranged at the rear or side of the motor vehicle, be formed. In particular, the lighting device 1 is a turn signal for the motor vehicle. The headlight 1 comprises a housing 2, which is preferably made of plastic. In a light exit direction 3, the headlight housing 2 has a light exit opening, which is closed by a transparent cover 4. The cover 4 is made of colorless plastic or glass. The disk 4 may be formed as a so-called clear disk without optically effective profiles (for example, prisms). Alternatively, the pane 4 may be provided, at least in regions, with optically active profiles, which in particular cause a scattering of the light passing through in the horizontal direction.

Inside the headlight housing 2, two light modules 5, 6 are arranged in the illustrated embodiment. The light modules 5, 6 are arranged fixed or relative to the housing 2 movable. By a relative movement of the light modules 5, 6 to the housing 2 in the horizontal direction, for example, a dynamic cornering light function can be realized. In a movement of the light modules 5, 6 about a horizontal axis, ie in the vertical direction, a headlight range control will be realized. The light modules 5, 6 are for generating a desired light distribution, for example a low beam, a high beam, a city light, a highway light, a motorway light, a fog light, a static or dynamic Kurvenlicht- or any other static or adaptive Light distribution formed. The light modules 5, 6 generate the desired light function either alone or in combination with each other by the light module 5 of each individual light module; 6 supplied partial light distributions are superimposed to the desired total light distribution. The light modules 5, 6 can be designed as reflection modules and / or as projection modules. Of course, more or less than the illustrated two light modules 5, 6 may be provided in the headlight housing 2.

On the outside of the headlight housing 2, a control unit 7 is arranged in a control unit housing 8. Of course, the control unit 7 can also be arranged at any other point of the headlamp 1. In particular, a separate control device can be provided for each of the light modules 5, 6, wherein the control devices can be an integral part of the light modules 5, 6. Of course, the control unit 7 may also be arranged remotely from the headlight 1. The control unit 7 serves to control and / or regulate the light modules 5, 6 or of subcomponents of the light modules 5, 6, such as light sources of the light modules 5, 6. The control of the light modules 5, 6 or the subcomponents by the control unit. 7 takes place via connecting lines 10, which in FIG. 1 are shown only symbolically by a dashed line. About the lines 10 is a supply of the light modules 5, 6 with electrical energy. The lines 10 are through an opening in Headlight housing 2 is guided in the control unit housing 8 and connected there to the circuit of the control unit 7. If a plurality of control devices are provided as an integral part of the light modules 5, 6, the lines 10 and can account for the opening in the headlight housing 2.

For better EMC shielding, the control unit housing 8 consists of an electrically conductive material, in particular of metal, preferably of die-cast aluminum. Also for better EMC shielding the lines 10 are shielded, in particular by means of a line 10 surrounding metal braid or a metal-plastic braid. In the control unit housing 8, an opening is further provided, in which a plug / socket element 9 is arranged. Via the plug / socket element 9, the control unit 7 with a higher-level control unit (for example, a so-called body controller) and / or a power supply of the motor vehicle (for example, a vehicle battery) may be connected.

The light modules 5, 6 of the illumination device 1 use as light sources one or more semiconductor light sources, in particular light emitting diodes (LEDs). LED headlights 1, which have a large number of LEDs, are increasingly used. By switching individual LEDs or individual LED groups off and on, variable light distributions can be achieved. Such headlights 1 are referred to as pixel or matrix headlights. Usually several LEDs are connected in a series circuit (also branch or chain).

FIG. 2 shows a schematic circuit diagram 12 comprising the control unit 7 and by way of example the light module 5, wherein the Control unit 7 and the light module 5 are electrically connected to each other by means of the line 10. The light module 5 comprises a series connection of semiconductor light sources 14b, 14c and 14z. The control unit 7 comprises a current source 16 and a measuring resistor 18. An actual voltage 20 applied to the series connection of the semiconductor light sources 14 is measured in the control unit 7. By means of the measuring resistor 18, an actual current 22 is measured by the series connection of semiconductor light sources 14. In FIG. 2 not shown form a temperature sensor is arranged on the light module 5, with which an actual temperature in the region of the semiconductor light sources 14 is determined. Of course, several temperature sensors may be present. In one embodiment, the temperature sensor is a temperature-dependent resistor. Accordingly, an additional measuring line between the light module 5 and control unit 7 according to the line 10 is available for determining the actual temperature.

FIG. 3 12 shows a schematic block diagram 24. The block diagram 24 is part of the presented method for operating the control device 7. A block 26 is supplied with the actual voltage 20, the actual current 22 and the actual temperature 28. Depending on the actual voltage 20, the actual current 22 and the actual temperature 28 of the block 26 generates a compensated actual voltage 30, which in the following FIG. 4 is explained in more detail. The compensated actual voltage 30 is supplied to a block 32 and a block 34. The block 32 determines a reference voltage 36 as a function of the compensated actual voltage 30 and supplies it to the block 34. The determination of the reference voltage 36 by the block 32 is in FIG. 5 explained in more detail. The block 34 detects in response to the compensated actual voltage 30 and in response to the reference voltage 36 an error 48 of the series circuit of Semiconductor light sources 14.

Compared with the measured actual voltage 20, the compensated actual voltage 30 comprises a compensation of variable variables, such as temperature and / or aging drift, which are reflected directly in the actual voltage 20 and would make monitoring of the light module 5, 6 more difficult. In contrast, by means of the compensated actual voltage 30, a monitoring in dependence on the actual voltage 20 can be performed.

The compensated actual voltage 30 is determined as a function of the voltage applied to the series circuit 20 actual voltage. The reference voltage 36 is determined in the block 32 as a function of the compensated actual voltage 30. In block 34, the compensated actual voltage 30 is compared with the reference voltage 36. Depending on the comparison, block 34 determines an error of the series connection of semiconductor light sources 14.

FIG. 4 FIG. 12 schematically illustrates a block diagram as part of the block 26 FIG. 3 , The measured actual temperature 28 is fed to an addition point 42. Likewise, a reference temperature 44 of the addition point 42 is supplied. A temperature difference 46 results from the subtraction of the reference temperature 44 from the actual temperature 28. The temperature difference 46 represents a comparison of the reference temperature 44 with the actual temperature 28. By this comparison with the reference temperature 44 is the Actual temperature 28 normalized. A first voltage value 48 is formed from the multiplication of the temperature difference 46 and a temperature coefficient 50 by means of the multiplication point 52. A compensated actual voltage 30a is obtained from the addition of Actual voltage 20 and the first voltage value 48 is formed by means of the addition point 54.

A current difference 56 is formed by means of the addition point 58 from the subtraction of a reference current 60 from the actual current 22. The current difference 56 represents a comparison of the reference current 60 with the actual current 22. By this comparison with the reference current 60, the actual current 22 is normalized. A second voltage value 62 is determined by means of the multiplication point 64 as the product of the current difference 46 and a current coefficient 66 determined from a characteristic curve. A compensated actual voltage 30b is determined by means of the addition point 68 as the sum of the second voltage value 62 and the compensated actual voltage 30a.

According to FIG. 4 the compensated actual voltage 30b is output as compensated actual voltage 30 from the block 26. Of course, the compensated actual voltage 30 a can also be output as compensated actual voltage 30 from the block 26. Of course, instead of the compensated actual voltage 30a, the measured actual voltage 20 can also be supplied to the addition point 68 in order to output the sum of the measured actual voltage 20 as compensated actual voltage 30 from the block 26.

The reference temperature 44 can originate, for example, from a reference measurement or a plurality of reference measurements for the light module 5 or 6. In another embodiment, when the light module 5, 6 is switched on for the first time, the temperature is measured and stored as reference temperature 44 in a non-volatile memory. The temperature coefficient 50 depends on the light-emitting diode type and the number of LEDs and is determined from a characteristic curve. The temperature coefficient 50 is stored in a non-volatile memory.

The reference current 60 can be determined from a reference measurement or several reference measurements and stored in a non-volatile memory of the control unit 7. The current coefficient 66 is dependent on the type of light emitting diode and the number of light-emitting diodes and is stored in a non-volatile memory of the control unit 7. Of course, in one embodiment, the reference current 60 can also be measured during the first switch-on of the control unit 7 and stored in a non-volatile memory of the control unit 7.

The control unit 7 is supplied with information about the installation location of the illumination device. When the light module 5, 6 is switched on for the first time, the control unit 7 stores this installation location. If the controller 7 detects a change in the installation site, the stored reference measurements of the reference temperature 44 and / or the reference current 60 are invalidated and the reference measurement is performed again.

FIG. 5 shows an embodiment of the block 32 in a schematic block diagram FIG. 3 , In the present case, the reference 36 is determined as an exponentially smoothed value from a plurality of compensated values of the actual voltage 30. For this purpose, a voltage difference 70 is determined from a subtraction of a reference voltage 36 (n-1) determined at the instant n-1 from the compensated actual voltage 30 (n) at the time n by means of the addition point 72. A product 74 results from the multiplication of the voltage difference 70 with a forgetting factor 76, which preferably assumes a value of less than 0.05. The reference voltage 36 (n) at time n is taken from the Addition of the product 74 with the reference voltage 36 (n-1) at time n-1 determined by the addition point 78.

FIG. 6 shows a schematically illustrated voltage-time diagram 80. When you first turn on the controller 7, the value of the first measurement 82 of the reference voltage 36 is determined. If the values of the measurements 84, 86 and 88 are each within a second limit 90 about the reference voltage 36 at the respective time, then the reference voltage 36 is updated as a function of the compensated actual voltage 30 according to the block 32.

If the control unit 7 is switched off, then the current value of the measurement 92 of the reference voltage 36 is stored in a non-volatile memory of the control unit 7. After a renewed switching on of the control unit 7, the value of the measurement 92 is used as a starting point for the further calculation or adaptation of the reference voltage 36. Exemplary are in FIG. 6 further measurements and the course of the reference voltage 36 shown. For example, the measurements 94, 96 and 98 are not used to update the reference voltage 36 according to the block 32, since they are outside the second limit 90 by the respective value of the reference voltage 36.

The error 40 of the series connection of the semiconductor light source 14 is detected when the compensated actual voltage 30, for example in the form of a value of one of the measurements 100 to 108, is outside a first limit 110 around the respective value of the reference voltage 36.

In one embodiment, the error 40 is detected when the compensated actual voltage 30 in the form of the measurements 100 to 108 at several times outside the first limits 110 is about the reference voltage 36.

In one embodiment, the error 40 is detected in response to a value of an error counter. For example, with a value of the error counter of 0, the error counter increments the reference voltage 36 upon detection of the measurement 100 outside the first boundary 110. The same applies to the measurements 102 to 108. However, if a measurement 112 within the first limit 110 or within the second limit 90 is around the reference voltage 36 between the measurements 102 and 104, the error counter is decremented. Thus, the error counter has a value of 1 in the measurement 100, a value of 2 in the measurement 102, a value of 1 in the measurement 112, a value 2 in the measurement 104, a value of 3 in the measurement 106, and 3 in the measurement Measurement 108 has a value of 4. If the threshold value for detecting or for determining the error 40 is, for example, at a value of 4, the error 40 in the control unit 7 is determined during the measurement 108. Thus, the error 40 is detected when the compensated actual voltage 30 is at a plurality of measurement times of the measured actual voltage 20, in particular at least 4 measurement times of the measured actual voltage 20, outside the first limit 110 to the reference voltage 36.

Claims (10)

1. Method for operating a control device (7) for a light module (5; 6), comprising a series connection of semiconductor light sources (14), of a lighting means (1) for a motor vehicle, an actual voltage (20) that is applied to the series connection being detected, characterized in that a compensated actual voltage (30) is detected depending on the applied actual voltage (20), in that the compensated actual voltage (30) is detected by means of a reference temperature (44) and a temperature coefficient (50) and/or the compensated actual voltage (30) is detected by means of a reference current (60) and a current coefficient (66), in that a reference voltage (36) is detected depending on the compensated actual voltage (30), in that the compensated actual voltage (30) is compared with the reference voltage (36), and in that a fault (40) of the series connection is detected depending on the comparison.
2. Method according to claim 1, wherein when the compensated actual voltage (30) is detected by means of the reference current (44) and the current coefficient (50), an actual current (22) through the series connection is detected, and wherein the compensated actual voltage (30) is detected depending on the actual current (22), the reference current (60) and the current coefficient (66).
3. Method according to claim 1 or claim 2, wherein when the compensated actual voltage (30) is detected by means of the reference temperature (44) and the temperature coefficient (50), an actual temperature (28) in the region of the semiconductor sources (14) is detected, and wherein the compensated actual voltage (30) is detected depending on the actual temperature (28), the reference temperature (44) and the temperature coefficient (50).
4. Method according to any of the preceding claims, wherein the fault (40) is identified when the compensated actual voltage (30) is outside a first limit (110) of the reference voltage (36).
5. Method according to any of the preceding claims, wherein the fault (40) is identified when the compensated actual voltage (30) is outside the first limit (110) of the reference voltage (36) at a plurality of measurement times of the measured actual voltage (20), in particular at least four measurement times of the measured actual voltage (20).
6. Method according to any of the preceding claims, wherein the reference voltage (36) is updated depending on the compensated actual voltage (30) when the compensated actual voltage (30) is inside a second limit (90) of the reference voltage (36).
7. Method according to claim 6, wherein the magnitude of the first limit (110) is greater than the magnitude of the second limit (90).
8. Method according to any of the preceding claims, wherein the reference voltage (36) is detected as an exponentially smoothed value from a plurality of compensated actual voltages (30).
9. Control device (7) for a light module (5; 6), comprising a series connection of semiconductor light sources (14), of a lighting means (1) for a motor vehicle, the control device being designed to detect an actual voltage (20) applied to the series connection, characterized in that the control device is further designed to detect a compensated actual voltage (30) depending on the applied actual voltage (20), to detect the compensated actual voltage (30) by means of a reference temperature (44) and a temperature coefficient (50) and/or to detect the compensated actual voltage (30) by means of a reference current (60) and a current coefficient (66), to detect a reference voltage (36) depending on the compensated actual voltage (30), to compare the compensated actual voltage (30) with the reference voltage (36), and to detect a fault (40) of the series connection depending on the comparison.
10. Lighting means (1) for a motor vehicle, comprising a light module (5; 6) and a control device (7) according to claim 9, wherein the control device (7) is connected to the light module (5; 6).

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