DE102021131026A1 - Method for testing at least one light-emitting diode of a lighting device, in particular of a motor vehicle - Google Patents

Abstract

The invention relates to a method for testing at least one light-emitting diode (4) of a lighting device (1), which has a control unit (2) having a microcontroller (6) and a DC voltage converter (7) with a coil (9) for operating the light-emitting diode (4). assigned. The microcontroller (6) uses a first variable representing an input voltage (UE) of the DC-DC converter (7), a second variable representing an output voltage (UA) of the DC-DC converter (7) and a current flowing through the coil (9). Current size determined. The light-emitting diode (4) is checked by means of the microcontroller (6) as a function of the values determined and as a function of the current value determined.

Description

The invention relates to a method for testing at least one light-emitting diode of a lighting device, in particular of a motor vehicle.

The EP 1 915 630 B1 discloses a system having a controller configured to turn on a light emitting diode and control power dissipation in it. A clocking device is also provided, which is designed to generate a clock signal, a frequency of the clock signal being determined in accordance with a measured current and/or a measured temperature of a light-emitting diode. The U.S. 8,487,633 B2 an arrangement for fault detection of electrical consumers in motor vehicles can be seen as known. In addition, from the AT516515B1 a circuit arrangement for the operation of light-emitting diodes is known.

The object of the present invention is to create a method so that at least one light-emitting diode of a lighting device, in particular of a motor vehicle, can be tested in a particularly advantageous manner.

According to the invention, this object is achieved by a method having the features of patent claim 1 . Advantageous configurations of the invention are the subject matter of the dependent claims.

The invention relates to a method for testing at least one light-emitting diode of a lighting device, in particular of a motor vehicle. This means that it is preferably provided that in the method the lighting device and thus the light-emitting diode are components of a motor vehicle, which can preferably be designed as a motor vehicle, in particular as a passenger car. In particular, the method is carried out, for example, during operation of the motor vehicle which, for example, is driving along a roadway or is stationary during operation. The lighting device is, for example, a headlight, in particular a front headlight. The light-emitting diode is designed, for example, to provide a low beam of the lighting device, in particular of the headlight and very particularly of the front headlight. It is also conceivable that the lighting device is a blinker, which is also referred to as a direction indicator or direction indicator and is designed to provide information about a change in the direction of travel of the motor vehicle or to announce this. The lighting device includes at least one light-emitting diode, which is also referred to as a light-emitting diode, luminescence diode or LED. In particular, it is conceivable that the lighting device comprises at least one additional light-emitting diode or several additional light-emitting diodes, the light-emitting diodes of the lighting device being electrically connected to one another, for example, thereby forming a light-emitting diode chain, also referred to as an LED chain. For example, the light-emitting diodes of the lighting device are arranged or connected in series. It is conceivable that exactly one light-emitting diode of the lighting device or exactly one of the light-emitting diodes of the lighting device is checked in the method, or that some but not all of the light-emitting diodes of the lighting device or all the light-emitting diodes of the lighting device are checked in the method.

In the method, the lighting device is assigned a control unit for operating the light-emitting diode, in particular the lighting device. The control unit is an electronic control unit, in particular an electronic computing device. The feature that the control unit is designed to operate the light-emitting diode means in particular that the control unit is designed to activate the light-emitting diode that is initially deactivated, for example, so that the activated light-emitting diode provides or emits light, in particular in such a way that the light emitted or provided by the light-emitting diode is emitted to an area surrounding the lighting device. In this case, for example, a person in the vicinity can visually perceive the provided or emitted light with their eyes. Furthermore, for example, the control device can deactivate the initially active light-emitting diode, as a result of which the provision or emission of the light is ended. In the method, the control unit has a microcontroller, which is arranged, for example, on a circuit board of the control unit. In the method, the control device also has a DC-DC converter, which is arranged on the circuit board, for example. For example, the DC-DC converter and the microcontroller are connected to one another via a data bus arranged on the circuit board and also simply referred to as a bus, so that the microcontroller can control the DC-DC converter and thereby operate it, for example via the data bus. In this case, the DC-DC converter has, in particular at least or precisely, a coil. In particular, the coil is an inductive, passive component with an inductance. In particular, the coil is formed by at least one or more windings.

In order to be able to test the light-emitting diodes and thus the lighting device in a particularly advantageous manner, in particular for the functionality of the light-emitting diode, in a first step of the method the microcontroller is used to determine a first, in particular electrical, variable which represents an input voltage of the DC-DC converter. Furthermore, in the first step of the method, the microcontroller is used to determine a second, in particular electrical, variable which represents an output voltage of the DC/DC converter. The feature that the respective variable represents the input voltage or output voltage is to be understood in particular as meaning that the respective variable correlates with the input voltage or output voltage, and therefore indicates the input voltage or output voltage. To put it another way, for example, the respective variable is a measure of the input voltage or output voltage of the DC-DC converter. Furthermore, in the first step of the method, the microcontroller is used to determine a current variable that represents an electrical current flowing through the coil. The electrical current flowing through the coil is also referred to as the coil current. If a current is mentioned before and in the following, then unless otherwise stated, this means an electric current. Thus the coil current is an electric current. The feature that the current magnitude represents the coil current means in particular that the current magnitude is related to the coil current, in particular dependent on the coil current. In particular, the magnitude of the current can indicate the coil current. In particular, it is conceivable that the current magnitude indicates the coil current. If, for example, the coil current changes, the magnitude of the current changes as a result, for example, in particular to the same extent. Expressed again in other words, it is possible, for example, to draw conclusions about the current actually flowing through the coil, for example, from the magnitude of the current.

In a second step of the method, the light-emitting diode is checked by the microcontroller as a function of the values determined and as a function of the current value determined, in particular with regard to the functionality of the light-emitting diode. In other words, the method provides for the first variable, the second variable and the current variable to be used to conclude whether the light-emitting diode is functional and therefore emits light or can emit light or not. If, for example, it is determined on the basis of the first variable, the second variable and the current variable that the light-emitting diode provides light, then it is concluded that the light-emitting diode works, and is therefore functional or functional. However, if it is determined on the basis of the first variable, the second variable and the current variable that the light-emitting diode does not emit any light, then it is concluded, for example, that the light-emitting diode is inoperative or non-functional, and therefore non-functional. The method makes it possible to test the light-emitting diode with only a very small amount of wiring and with a particularly small number of electrical or electronic components and thus in a particularly cost-effective manner. In particular, the method according to the invention makes it possible to test the light-emitting diode compared to conventional solutions with fewer lines and fewer resistors, in particular shunt resistors, so that higher efficiency and lower costs can be achieved compared to conventional solutions.

The invention is based in particular on the considerations and findings that lighting devices such as the lighting device used in the method according to the invention, in particular of motor vehicles, and therefore light functions, in particular of motor vehicles, are safety-relevant components or functions, it being particularly conceivable that the lighting device or light functions have an ASIL classification and are therefore subject to ASIL requirements, i.e. should meet ASIL requirements. This usually requires additional hardware measures, ie physical, in particular electrical or electronic, components that make it possible to meet corresponding requirements such as ASIL requirements, in particular with regard to the fact that the lighting device can be tested in particular for its functionality. For this purpose, an additional current measurement is usually provided at or on a cathode side of the light-emitting diode, which in turn necessitates additional, separate cathode lines, for example in a headlight wiring harness, and additional shunt resistors. For example, the control device is connected to the lighting device via the aforementioned headlight wiring harness, also referred to simply as the wiring harness. The method according to the invention now makes it possible to avoid an additional current measurement on or on the cathode side and thus additional, separate cathode lines and shunt resistors, so that the lighting device can be tested effectively, efficiently, cost-effectively and compactly using the method according to the invention.

In order to be able to test the light-emitting diode in a particularly simple and cost-effective manner, it is provided in one embodiment of the invention This means that when testing the light-emitting diode, a current flowing out of the light-emitting diode via its cathode, and consequently leaving the light-emitting diode via its cathode, is not taken into account. In other words, the light-emitting diode, also simply referred to as a diode, has the named cathode in particular as exactly one or only cathode and, in particular, exactly one anode, with when an electric current flows through the light-emitting diode, the electric current from the anode to the Cathode and thus flows in a forward direction of the light-emitting diode. In particular, an electric current can only flow through the light-emitting diode in the forward direction and thus only from the anode to the cathode. In order to avoid an excessive amount of cabling and an excessive number of components for testing the light-emitting diode, it is preferably provided that when testing the light-emitting diode, a consideration, i.e. in particular a determination of the current flowing out of the light-emitting diode via the cathode, i.e. a current flowing on the side of the cathode is omitted. The current flowing out of the light-emitting diode via the cathode is also referred to as the cathode current, which is preferably not taken into account when testing the light-emitting diode. As a result, a corresponding effort, in particular cabling and installation space effort, for determining the cathode current can be avoided, so that the light-emitting diode can be tested in a particularly simple and cost-effective manner.

A further embodiment is characterized in that the current magnitude represents a current flowing on the anode side of the light-emitting diode as the current flowing through the coil. The current flowing on the anode side is also referred to as the anode current, which flows on a side of the light-emitting diode that is also referred to as the anode side. The anode current is therefore to be understood as meaning an electrical current which, in particular in the method, flows into the light-emitting diode via the anode and is therefore supplied to the light-emitting diode via the anode. It is therefore preferably provided to use the anode current as the current variable, with the anode current flowing, for example, in particular outside of the current converter, in particular outside of the control unit. In particular, it is conceivable that the anode current is provided by the current transformer. As a result, the light-emitting diode can be tested in a particularly simple and at the same time effective manner. The anode current correlates, in particular directly, with the coil current, in particular in such a way that, in particular in a first approximation, the anode current corresponds at least essentially to the coil current. The anode current is therefore a particularly advantageous and easy to determine, in particular to measure, measured variable that represents the coil current particularly well.

It has also been shown to be particularly advantageous if the current flowing through the coil is measured as the current magnitude and thereby determined by means of the microcontroller. In other words, it can be provided, for example, that the anode current is measured as the current variable representing the coil current and thereby determined by means of the microcontroller, in particular outside of the current transformer and very particularly outside of the control unit, with the anode current representing the coil current in particular in that the anode current , in particular directly, depends on the coil current or results from the coil current, it being particularly conceivable that, in particular in a first approximation, the anode current corresponds to the coil current. However, it has proven to be particularly advantageous if, in particular within the current transformer, the microcontroller measures the coil current as the current magnitude and thereby determines that the current magnitude is the coil current in this embodiment. As a result, the light-emitting diode can be tested particularly precisely, simply and effectively.

In a further, particularly advantageous embodiment of the invention, a current output by the DC-DC converter is measured by the microcontroller as the current magnitude representing the current flowing through the coil and is thereby determined. The current delivered by the DC-DC converter is also referred to as converter current and is provided by the DC-DC converter, also simply referred to as converter, and therefore flows out of the DC-DC converter, it being particularly conceivable for the converter current to be measured outside of the DC-DC converter, in particular outside of the control unit . In particular, it is conceivable for the converter current to be measured inside the control unit, but for example outside the DC voltage converter, and thereby determined. It is particularly conceivable that the anode current depends on the converter current or results from the converter current, it being possible in particular for the converter current to correspond to the anode current. In particular, it is conceivable that the converter current depends on the coil current or results from the coil current, in particular such that, for example, the DC-DC converter has a capacitor with a capacitance, the coil current being smoothed by means of the capacitor, in order to thereby generate the converter current from the coil current , which is, for example, the anode current or can correspond to the anode current. As a result, the light-emitting diode can be tested particularly effectively and efficiently.

In order to be able to test the light-emitting diode particularly well with a particularly small amount of components and lines, it is provided in a further embodiment of the invention that the microcontroller is used to measure a current flowing into the light-emitting diode via its anode, i.e. the anode current, as the current flowing through the Coil current representative current size measured and thereby determined. In other words, it is provided in this embodiment of the invention that the microcontroller measures the anode current, in particular outside the DC-DC converter and, for example, inside the control unit, as a result of which the light-emitting diode can be tested in a particularly advantageous manner.

A further embodiment is characterized in that a buck converter is used as the DC voltage converter. As a result, the light-emitting diode can be operated and tested in a particularly advantageous manner. The DC-DC converter, in particular the buck converter, is a driver, also referred to as an LED driver, or a component of a driver, also referred to as an LED driver, via which the light-emitting diode can be advantageously operated, in particular by means of the microcontroller.

In order to be able to test the light-emitting diode particularly precisely and thus meaningfully, it is provided in a further embodiment of the invention that a ripple variable is determined by means of the microcontroller, which is a ripple, also referred to as a ripple, in particular residual ripple, of a current output by the DC-DC converter and /or characterized by the current flowing through the coil, the light-emitting diode being checked by means of the microcontroller as a function of the determined ripple size. This embodiment makes use of the fact that the current (converter current) delivered by the DC-DC converter is wavy and thus has wave crests and wave troughs, with the ripple magnitude in particular indicating a difference between one of the wave troughs and one of the wave crests, it being preferably provided that one wave crest immediately, i.e. directly, which is followed by a trough or vice versa. The light-emitting diode can be tested particularly advantageously and in particular particularly simply and precisely on the basis of the waviness.

In order to be able to test the light-emitting diode particularly simply and precisely, a further embodiment of the invention provides for the ripple, in particular the residual ripple, to be measured by means of the microcontroller and the ripple size to be determined using the measured ripple, in particular residual ripple. Alternatively, it is conceivable that the ripple size is stored in a data memory of the control unit and is retrieved from the data memory and thereby determined. As a result, the light-emitting diode can be checked particularly easily.

In a further, particularly advantageous embodiment of the invention, the input voltage is measured as a third variable by means of the microcontroller. The measured input voltage or the third variable is corrected using at least one first correction value, as a result of which the first variable is determined from the third variable. For example, the first correction value is stored in the data memory. The microcontroller also measures the output voltage as a fourth variable, with the output voltage or the fourth variable being corrected using at least one second correction value, as a result of which the second variable is determined, in particular calculated, from the fourth variable. For example, the second correction value is stored in the data memory. Provision is also made for the microcontroller to measure a fifth variable representing the current flowing through the coil, which is corrected using at least one third correction value, whereby the current variable is determined, in particular calculated, from the fifth variable. As a result, the light-emitting diode can be checked particularly precisely, so that, for example, safety requirements for the lighting device or the motor vehicle can be met particularly well overall.

The microcontroller can use the first variable, the second variable and the current variable to carry out a plausibility check, which can advantageously be used to check the light-emitting diode. This plausibility check is implemented, for example, by a plausibility check algorithm that is executed or processed by the microcontroller. The plausibility check algorithm or the plausibility check can be used instead of measuring the cathode current in order to check the light-emitting diode in a particularly simple, cost-effective, effective and precise manner.

• 1 eine schematische Darstellung einer Leuchteinrichtung und eines Steuergeräts, mittels welchem die Leuchteinrichtung geprüft wird;
• 2 eine schematische Darstellung eines als Buck-Wandler ausgebildeten Gleichspannungswandlers des Steuergeräts;
• 3 Verläufe zum Veranschaulichen eines Verfahrens zum Prüfen der Leuchteinrichtung; und
• 4 eine weitere schematische Darstellung der Leuchteinrichtung und des Steuergeräts.

Further details of the invention result from the following description of a preferred exemplary embodiment with the associated drawings. It shows:

• 1 a schematic representation of a lighting device and a control unit, by means of which the lighting device is tested;
• 2 a schematic representation of a designed as a buck converter DC-DC converter of the control unit;
• 3 Curves to illustrate a method for testing the lighting device; and
• 4 another schematic representation of the lighting device and the control unit.

Elements that are the same or have the same function are provided with the same reference symbols in the figures.

1 shows a schematic representation of a lighting device 1 and a control unit 2, the lighting device 1 and the control unit 2 being, for example, components of a motor vehicle designed in particular as a motor vehicle, particularly as a passenger car. The lighting device 1 and the control unit 2 are, for example, two separately configured and therefore individual components that are connected to one another, for example, via a line device 3, in particular in such a way that the line device 3 transmits at least one, in particular, electrical signal and/or data and/or an electrical Current can be transmitted in particular from the control unit 2 to the lighting device 1 and received by the lighting device 1 . For example, the line device 3 is a cable harness. For example, the line device 3 is designed separately from the lighting device 1 and separately from the control device 2 and is connected to them.

The lighting device 1 has in the 1 shown embodiment several light-emitting diodes 4, which are also simply referred to as diodes or LEDs. In 1 an arrow 5 indicates a respective transmission direction of the respective light-emitting diode 4, the respective light-emitting diode 4, in particular precisely, having a respective anode + and, in particular precisely, a respective cathode -. An electric current can only flow along or in the forward direction and thus from the respective anode + to the respective cathode - through the respective light-emitting diode 4, with no electric current being able to flow through the respective light-emitting diode 4 in the opposite direction.

The control unit 2 has a microcontroller 6, which is also referred to as an MCU or μC. Furthermore, the control unit 2 has a DC voltage converter 7, which is also referred to as a DC/DC converter or simply as a converter. 2 12 shows an embodiment of the DC/DC converter 7. In the embodiment shown in the figures, the DC/DC converter 7 is a buck converter. It can be seen that the microcontroller 6 and the DC-DC converter 7 are connected to one another via a data bus 8, also referred to simply as a bus, via which, for example, a signal, in particular an electrical signal, can be transmitted from the microcontroller 6 to the DC-DC converter 7 and received by the DC-DC converter 7. in particular in order thereby to control and thus operate the DC-DC converter 7 by means of the microcontroller 6 . The DC-DC converter 7 is a driver or part of a driver, by means of which the light-emitting diodes 4 can be operated and in particular activated and deactivated.

For example, the lighting device 1 is a headlight, in particular a headlight arranged on the front of the motor vehicle, of the motor vehicle. It is also conceivable that the lighting device 1 is a direction indicator. If the respective light-emitting diode 4 is functional and activated, the light-emitting diode 4 provides a light. This means that the respective light-emitting diode 4 emits the light that is emitted, for example, to an environment of the lighting device 1, in particular of the motor vehicle, and can be visually perceived by a person in the environment with their eyes. Furthermore is off 1 It can be seen that the light-emitting diodes 4 are electrically connected to one another and are connected in series, for example, so that the light-emitting diodes 4 form a light-emitting diode chain, also referred to as an LED chain.

Out of 2 it can be seen that the DC-DC converter 7 has, specifically, a coil 9 with an inductance L, specifically, a capacitor 10 with a capacitance C, a first switch S ₁ and a second switch S ₂ . In particular during operation of the DC-DC converter 7, which is operated during operation, the DC-DC converter 7 also has an input voltage U E present at an input of the DC-DC converter 7 and thus at the DC-DC converter 7, and an output voltage _{U A which} is present at an output of the DC-DC converter 7 is applied or is provided or released by the DC-DC converter 7 in particular via its output. During the operation of the DC-DC converter 7, for example, the DC-DC converter 7 has exactly two different operating phases. During a first of the operating phases, switch S ₁ is closed, for example, while switch S ₂ is open. In particular, the DC-DC converter 7 is connected via its input to an energy source, in particular a current source, in particular via the microcontroller 6 and/or the energy source is a component of the microcontroller 6. The coil 9 is thus charged with electric current during or in the first operating phase. During the second phase of operation, the switch S ₂ is closed, and the Switch S ₁ is open, so that in or during the second operating phase the electrical current flows from the coil 9 into the capacitor 10 so that the capacitor 10 is charged in particular with the electrical current from the coil 9 .

A first period of time during which the switch S ₁ , in particular continuously, is closed and subsequently, for example, the switch S ₂ , in particular continuously, is open is also denoted by t _on , so that during _{t on} the DC-DC converter 7 is operated in its first operating phase becomes. A second period of time during which switch S ₁ is open, in particular continuously, and switch S ₂ is closed, in particular continuously, is also denoted by t _off , so that for example during t _off the DC-DC converter 7 is operated in its second operating phase.

A method is described below by means of which the light-emitting diodes 4 and thus the lighting device 1 can be tested in a particularly simple and at the same time precise manner. In a first step of the method, the microcontroller 6 is used to determine a first variable that represents the input voltage U _E of the DC-DC converter 7 . In addition, a second variable representing the output voltage U _A of the DC-DC converter 7 is determined by means of the microcontroller 6 . In addition, the microcontroller 6 is used to determine a current variable which represents an electric current flowing through the coil 9 and also referred to as the coil current. In a second step of the method, at least one of the light-emitting diodes 4 is checked as a function of the determined first variable, as a function of the determined second variable and as a function of the determined current variable, in particular for functionality.

The method preferably provides for the microcontroller 6 to measure the input voltage U _E as the third variable, the output voltage U _A as the fourth variable and the coil current as the fifth variable, in particular with a sufficient frequency and/or via an analog/digital converter. in a 1 Correction values, which are also referred to as calibration parameters, are stored in the data memory 11 of the control unit 2 shown particularly schematically. The calibration parameters are used to correct the measured third variable, the measured fourth variable and the measured fifth variable in order to determine, in particular to calculate, the first variable from the third variable, the second variable from the fourth variable and the current variable from the fifth variable. Thus, for example, in the present exemplary embodiment, the third variable is U _E , the fourth variable being U _A and the fifth variable I, ie the coil current. By correcting the third variable, the fourth variable and the fifth variable, the first variable, the second variable and the current variable are determined, in particular calculated, so that the first variable is a corrected input voltage U _E 'of the DC-DC converter 7, so to speak, and the second variable is a corrected output voltage U _A 'of the DC-DC converter 7 and the current magnitude is a corrected current I' flowing through the coil 9. In other words, the measured input voltage U _E , the measured output voltage U _A and the measured coil current labeled I are measured values that are determined, i.e. measured, by means of the microcontroller 6 and are corrected or calibrated by the calibration parameters in order to thereby to determine, in particular to calculate, the values U _E ' and U _A ' and the current value I'. The correction of U _E , U _A and I to U _E ', U _A ' and I' using the calibration parameters is explained below using U _E :

For example, calibration parameters k _UE and b _UE are used to correct U _E . Thus, for example, U _E ' results in: $${\text{u}}_{\text{E}}\text{'}={\text{k}}_{\text{UE}}*{\text{u}}_{\text{E}}+{\text{b}}_{\text{UE}\text{.}}$$

It can be seen that U _E , U _A and I (coil current) are actually measured variables or measured values measured by the microcontroller 6, from which U _E ', U _A ' and I', hence the first variable, the second variable and the current size, are determined, the first size, the second size and the current size then being used to test the at least one light-emitting diode 4 .

The correction values (calibration parameters) are determined, for example, during a check of the control unit 2, the check of the control unit 2 also being referred to as a control unit check. The control device test is carried out, for example, at one end of an assembly line along which, for example, at least control device 2 or a structural unit comprising control device 2 and, for example, also lighting device 1 is assembled, ie manufactured. For this reason, the control unit test is also referred to as an end-of-line test. For example, a testing device is connected to control device 2 . The test device is used, for example, to determine a difference between the third, fourth or fifth variable measured by microcontroller 6 during the control unit test and the actual input voltage U _E or output voltage U _A or the coil current, with the respective correction value being determined in this way and in particular stored in data memory 11 is stored that the difference when measured by means of the microcontroller 6 third or fourth or fifth variable is corrected by means of the correction value, is at least reduced or eliminated.

The microcontroller 6 checks, for example, whether the first variable (U _E ') is greater than a first limit value and smaller than a second limit value. For example, the microcontroller 6 checks, for example, whether the second variable (U _A ') is greater than a third limit and less than a fourth limit. The microcontroller also checks, for example, whether the current magnitude (I') is greater than a fifth limit value and less than a sixth limit value. If the first variable is greater than the first limit value and smaller than the second limit value, and if the second variable is larger than the third limit value and smaller than the fourth limit value, and if the current variable is larger than the fifth limit value and smaller than the sixth limit value, then determines that the tested light-emitting diode 4 is in order, that is, functional.

3 shows diagrams 12, 13, 14 and 15, on whose respective abscissa 16 the time is plotted. U _E is plotted on the ordinate 17 of diagram 12 . I _g is plotted on the ordinate 18 and I _s /I _g is plotted on the ordinate 19 of the diagram 14 . The coil current denoted by I _L (the current flowing through the coil 9) is plotted on the ordinate 20 of the diagram 15. A course 21 thus illustrates the coil current, which, as from 3 is recognizable, is wavy, and therefore has a ripple, in particular residual ripple.

$$\mathrm{\Delta }\text{I}=\left({\text{U}}_{\text{E}}\text{'}-{\text{U}}_{\text{A}}\text{'}\right)*{\text{t}}_{\text{ein}}/\text{L}$$

Since the coil current is wavy, the coil current has crests 22 and troughs 23 . A ripple of the coil current denoted by ΔI is also referred to as a ripple and is a difference between the lowest point of the trough 23 and the highest point of the immediately following crest 22. In this case, for example, a ripple size is determined by means of the microcontroller 6, which characterizes the ripple of the coil current , The light-emitting diode 4 being checked by means of the microcontroller 6 as a function of the determined ripple size. For example, the microcontroller 6 checks whether the following equations are fulfilled: $$\mathrm{\Delta }\text{I}={\text{t}}_{\text{out of}}/\text{L}$$

$$\mathrm{\Delta }\text{I}=\left({\text{u}}_{\text{E}}\text{'}-{\text{u}}_{\text{A}}\text{'}\right)*{\text{t}}_{\text{a}}/\text{L}$$

If the equations are satisfied and the above conditions are met, then the first size is greater than the first limit and less than the second limit, the second size is greater than the third limit and less than the fourth limit, and the current size is greater than the fifth limit and is smaller than the sixth limit value, it can be concluded that the tested light-emitting diode 4 is functional. The calibration parameters (correction values), also referred to as calibration data, are preferably protected against falsification by a checksum, for example CRC16.

In particular, the method provides that, for testing the respective light-emitting diode 4, a current flowing out of the respective light-emitting diode 4 via its respective cathode and also referred to as cathode current is not taken into account. This causes how out 4 recognizable and illustrated there by crosses 24, lines 25 provided with the crosses 24 and an electrical resistor 26 provided with one of the crosses 24 and designed, for example, as a shunt resistor are omitted in comparison to conventional solutions or do not have to be used to switch the light-emitting diodes 4 to be checked, so that the light-emitting diodes 4 can be checked in a particularly simple and inexpensive manner. In 4 a ground connection, via which the light-emitting diode 4 is connected to an electrical ground, is denoted by 27, and a further ground connection is denoted by 28, with the ground connection 28 also being able to be omitted by the method described. The light-emitting diodes 4 can thus be tested with a particularly low outlay on lines and components, so that costs, weight and installation space can be saved. At the same time, the respective light-emitting diode 4 can be tested effectively and precisely, in particular with regard to its desired functionality.

Reference List

1

lighting device

2

control unit

3

management facility

4

led

5

Arrow

6

microcontroller

7

DC converter

8th

data bus

9

Kitchen sink

10

capacitor

11

data storage

12

diagram

13

diagram

14

diagram

15

diagram

16

abscissa

17

ordinate

18

ordinate

19

ordinate

20

ordinate

21

Course

22

wave crest

23

trough

24

Cross

25

Management

26

Resistance

27

ground connection

28

ground connection

+

anode

-

cathode

UE

input voltage

u.a

output voltage

S1

Switch

S2

Switch

L

inductance

C

capacity

tein

first time span

thousand

second time span

ΔI

ripple

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• EP 1915630 B1 [0002]
• US8487633B2 [0002]
• AT 516515 B1 [0002]

Claims (10)

Method for testing at least one light-emitting diode (4) of a lighting device (1), to which a control unit (2) having a microcontroller (6) and a DC voltage converter (7) with a coil (9) is assigned for operating the light-emitting diode (4). the steps: - by means of the microcontroller (6): determining a first variable representing an input voltage (UE) of the DC-DC converter (7), a second variable representing an output voltage (UA) of the DC-DC converter (7) and a one flowing through the coil (9). Current representing current size; and - By means of the microcontroller (6): checking the light-emitting diode (4) depending on the values determined and depending on the current value determined. procedure after claim 1 , characterized in that when checking the light-emitting diode (4), a current flowing out of the light-emitting diode (4) via its cathode (-) is not taken into account. procedure after claim 1 or 2 , characterized in that the current magnitude represents a current flowing on an anode (+) side of the light-emitting diode (4) as the current flowing through the coil (9). Method according to one of the preceding claims, characterized in that the current flowing through the coil (9) is measured as the current magnitude and thereby determined by means of the microcontroller (6). Method according to one of the preceding claims, characterized in that a current output by the DC voltage converter (7) is measured by the microcontroller (6) as the current magnitude representing the current flowing through the coil (9) and is thereby determined. Method according to one of the preceding claims, characterized in that a current flowing into the light-emitting diode (4) via its anode (+) is measured by means of the microcontroller (6) as the current magnitude representing the current flowing through the coil (9) and is thereby determined . Method according to one of the preceding claims, characterized in that a buck converter is used as the DC voltage converter (7). Method according to one of the preceding claims, characterized in that the microcontroller (6) is used to determine a ripple variable which represents a ripple (ΔI), in particular a residual ripple, of a current output by the DC-DC converter (7) and/or of the current through the coil ( 9) characterized by the current flowing, the light-emitting diode (4) also being checked by means of the microcontroller (6) as a function of the ripple size determined. procedure after claim 8 , characterized in that: - the ripple (ΔI), in particular residual ripple, is measured by means of the microcontroller (6) and the ripple size is determined on the basis of the measured ripple (ΔI), in particular residual ripple, or - the ripple size in a data memory (11) of the control unit (2) is stored and retrieved from the data memory (11) and thereby determined. Method according to one of the preceding claims, characterized in that: - the input voltage (U _E ) is measured as a third variable by means of the microcontroller (6), which is corrected by means of at least one first correction value, whereby the first variable is determined, - by means of the The microcontroller (6) measures the output voltage (U _A ) as a fourth variable, which is corrected using at least one second correction value, whereby the second variable is determined, and - the current flowing through the coil (9) is measured using the microcontroller (6). representative fifth variable is measured, which is corrected by means of at least one third correction value, as a result of which the current magnitude is determined.

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