Semiconductor light source and measuring method

Abstract

In at least one embodiment, the semiconductor light source (1) comprises a plurality of light sections (2) and a control unit (3), wherein - each of the light sections (2) comprises a plurality of optoelectronic semiconductor chips (21) for generating light, such as µLEDs, - the light sections (2) are operated in the same way, and - the control unit (3) comprises a comparison module (31) which is configured to detect at least one electric parameter (P) of each of the light sections (2) and to use numerical values for the individual light sections (2) of the detected at least one electric parameter (P) for a fault analysis.

Description

[0001] Description

[0002] SEMICONDUCTOR LIGHT SOURCE AND MEASUREMENT METHODS

[0003] A semiconductor light source is specified. Furthermore, a measurement method for such a semiconductor light source is specified.

[0004] The publications US 7 878 ​​103 Bl and US 2014 / 0 152 180 Al concern LED circuits.

[0005] One problem to be solved is to provide a semiconductor light source in which errors can be reliably detected.

[0006] This problem is solved, inter alia, by a semiconductor light source and a measuring method having the features of the independent patent claims. Preferred developments are the subject of the dependent claims.

[0007] According to at least one embodiment, the semiconductor light source comprises a plurality of luminaire strands. Each of the luminaire strands comprises one or more optoelectronic semiconductor chips. The semiconductor chips are designed to generate radiation, in particular to generate visible light. The visible light can be generated directly in a semiconductor layer sequence of the optoelectronic semiconductor chip in question, or at least one phosphor is assigned to the optoelectronic semiconductor chip in question, which phosphor at least partially converts radiation emitted directly by the optoelectronic semiconductor chip in question into radiation of a different wavelength. The semiconductor layer sequences of the optoelectronic semiconductor chips each have at least one active zone which, during operation, is designed to generate radiation by means of electroluminescence.The generated radiation is incoherent in the case of a light-emitting diode chip (LED chip for short), or in the case of a laser diode chip (LD chip for short), particularly coherent. The semiconductor layer sequences are preferably based on a II IV compound semiconductor material. The semiconductor material is, for example, a nitride compound semiconductor material such as Al. n In]__ n-m Ga m N or a phosphide compound semiconductor material such as Al n In]__ n-m Ga m P or an arsenide compound semiconductor material such as Al n In]__ n-m Ga mAs or like Alj^Gaj^In^. -j^AspP^-p, where in each case 0 < n < 1, 0 < m < 1 and n + m < 1 as well as 0 < k < 1. For example, for at least one layer or for all layers of the semiconductor layer sequence 0 < n < 0.8, 0.4 < m < 1 and n + m < 0.95 as well as 0 < k < 0.5 applies. The semiconductor layer sequences can contain dopants as well as additional components. For the sake of simplicity, however, only the essential components of the crystal lattice of the semiconductor layer sequence, i.e. Al, As, Ga, In, N or P, are given, even if these can be partially replaced and / or supplemented by small amounts of other substances.

[0008] Several types of optoelectronic semiconductor chips can be combined with one another in the lighting strands. The term ‘types’ refers, for example, to different emission colors. It is possible for the optoelectronic semiconductor chips to be the only light source of the semiconductor light source. According to at least one embodiment, the semiconductor light source comprises one or more control units, also referred to as driver ICs. The at least one control unit is designed to electrically control and operate the optoelectronic semiconductor chips, in particular the optoelectronic semiconductor chips combined to form the lighting strands. For example, the at least one control unit determines which current intensity is applied to the individual lighting strands and optoelectronic semiconductor chips and for how long.For this purpose, the at least one control unit has, for example, one or more current outputs to which the at least one assigned lighting string is connected.

[0009] According to at least one embodiment, the lighting strings are operated in a similar manner. For example, the optoelectronic semiconductor chips of the respective lighting strings are subject to the same ambient conditions, such as temperature and humidity, and / or are operated synchronously with one another, for example, with the same current intensities.

[0010] According to at least one embodiment, the at least one control unit (3) comprises at least one comparison module. The at least one comparison module is designed to record at least one electrical parameter for each of the lighting strands. For example, the electrical parameter is a forward voltage. A numerical value of the electrical parameter is determined for each of the lighting strands. For example, the forward voltage is therefore recorded for each of the lighting strands. According to at least one embodiment, the at least one comparison module is designed to use the numerical values ​​of the recorded at least one electrical parameter for the individual lighting strands for error analysis. This means, for example, that the numerical values, such as the individual forward voltages of the lighting strands, are compared with one another.If a comparison reveals an excessive deviation from a target value, such as a threshold value, or a target value range, such as a value range between two threshold values, an error is detected by at least one comparison module. The error could be, for example, a defect or failure of at least one optoelectronic semiconductor chip of the at least one respective lighting string.

[0011] It is possible for the at least one comparison module to be configured to output an error message if the error analysis reveals an error. The error message is sent, for example, to a control unit of a device, such as a motor vehicle, in which the semiconductor light source is installed.

[0012] In at least one embodiment, the semiconductor light source comprises several light strings and a control unit, wherein

[0013] - each of the luminaire strands comprises one or more optoelectronic semiconductor chips for generating light,

[0014] - the lighting strings are operated in the same way, and

[0015] - the control unit comprises a comparison module which is set up to record at least one electrical parameter from each of the lighting strands and to use numerical values ​​for the individual lighting strands of the recorded at least one electrical parameter for a fault analysis. For example, fault detection of individual LEDs in LED segments or in the lighting strands is carried out on the basis of a voltage measurement. This means, for example, that individual LED fault detection is possible in larger LED segments. A fault is, for example, an interrupted electrical line section or an electrical short circuit, also referred to as open or short. The fault detection can take place independently of environmental influences, such as temperature, or of aging of the optoelectronic semiconductor chips.

[0016] In some LED applications, particularly in the automotive industry, failures of individual LEDs in a luminaire are undesirable, as such failures could compromise safety or adversely affect the design. Fault detection of individual short-circuited or open LEDs is therefore necessary.

[0017] For larger luminaires with a high LED density, series or parallel connection of LEDs is common, so electronic monitoring of a single LED is generally no longer possible. If multiple LEDs are connected in series and / or parallel, fault detection of a short circuit or open circuit becomes increasingly difficult with increasing string length / number of parallel strings.

[0018] Short circuits or open connections in LED circuits can be detected by measuring the forward voltage and comparing the value with a corresponding reference. When LEDs are connected in series and / or parallel, the variations in the forward voltages, which can occur due to binning, temperature and / or aging of the individual LEDs, for example, add up in the worst case to such an extent that the cumulative variation exceeds the signal to be measured, i.e. a voltage change due to a short circuit or open contact, of an LED. Binning is understood in particular as the assignment of LEDs to a certain class, whereby within the class all LEDs have the same properties within specified tolerances, for example the same emission color or the same forward voltage.

[0019] With the semiconductor light source described here, this problem is solved, for example, by comparing the forward voltages of several similar series and / or parallel circuits. By using a reference, parallel disturbances, such as temperature and, under certain circumstances, aging, can be averaged out during the measurement, thus increasing the sensitivity of error detection.

[0020] The lighting strands and the LED segments are operated in particular with the help of a driver IC, whose driver channels can be designed as current sources or sinks. The number of LEDs in the circuit, i.e. per lighting strand, is for example 1, 5 or 10. The interference is to be minimized by a local adjacent arrangement of two or more LED segments or lighting strands, which are operated in particular in common mode, and the measurement evaluation in the driver IC in order to enable fault detection in larger series circuits and / or parallel circuits. For example, the difference between the forward voltages of two neighboring lighting strands within a segment is calculated and compared with a corresponding limit value. If the difference between the forward voltages exceeds the limit value, an error is registered.The monitoring of the lighting strings and LED segments, as well as error detection, are integrated into the driver IC. IC stands for integrated circuit.

[0021] This means that several locally adjacent lighting strands within a segment can be used as a reference for each other. The driver IC is used to assign the lighting strands and / or segments, which serve as a reference for each other. By using a driver IC with ADC measurements on the driver channels, individual initial values ​​and error limits can be stored for the individual lighting strands and / or segments. A single ADC in the IC can be used for the voltage measurement, like a differential measurement, so that individual channels to be compared are switched through to the same ADC, corresponding to multiplexing.

[0022] This eliminates the error deviation on the absolute measured value of the ADC and thus increases the detection accuracy.

[0023] In the semiconductor light source described here, for example, the following aspects are realized, individually or in any combination:

[0024] - A comparative system is operated consisting of two or more individual LED light strings within an LED segment, which are exposed to very similar environmental conditions and are, for example, located close to each other locally.

[0025] - Several such systems can be installed on one LED module, so that the semiconductor light source can be composed of several groups of light strands.

[0026] - An individual / flexible grouping of the driver channels to be compared is possible.

[0027] - It is possible to determine the voltage differences from the individually measured voltage values ​​of the lighting strands within a system.

[0028] - It is possible to operate the luminaire strings and / or LED segments to be compared within a system using constant current sources or constant current sinks with ideally the same current.

[0029] - Different temperatures of the luminaire strands and / or segments to be compared can be avoided.

[0030] - The same operating conditions for the light strings and / or segments to be compared, in particular the same aging, can be guaranteed.

[0031] - Individually defined initial values / reference values ​​for the voltage at a defined current in a lighting string and / or segment can be stored in a non-volatile memory.

[0032] - Measured values ​​from the production line can be used as a baseline value, for example a start value, also called a 0 h value.

[0033] - Newly read reference values ​​can be taken into account.

[0034] - A limit value for the deviating voltage at a defined current, tailored to the system, in particular to two closely spaced lighting strands and / or segments, can be stored in a non-volatile memory.

[0035] - Depending on the properties of the LEDs used, such as color, semiconductor material system, segment size, binning and / or aging, the limit values ​​can be stored individually.

[0036] - It is possible to maintain error tolerances, for example 6-sigma ranges.

[0037] - Repetitive measurements, for example in 10 ms intervals, of the voltage drop across the luminaire strands and / or segments to be compared at a defined current can be measured directly on the driver channel using an ADC.

[0038] - When using pulse width modulation, or PWM for short, measurements can be taken during an on-time.

[0039] - An evaluation of the di f ferential voltage of the system at a defined current is feasible.

[0040] - If the di f ferential value between the luminaire strands and / or segments to be compared exceeds the set limit value, an error can be registered.

[0041] - Individual control of the driver channels is possible.

[0042] - Switching off lighting strands and / or segments in the event of a fault is possible, alternatively or in addition to feedback to a higher-level control unit.

[0043] With the semiconductor light source described here, the following effects can be achieved, for example, individually or in any combination:

[0044] - Due to similar environmental conditions, voltage-changing influences, such as temperature, humidity and / or corrosion, have the same effect on both light strings and / or LED segments being compared.

[0045] - The interference affects the lighting strings and / or segments being compared equally and is eliminated in the comparison measurement, allowing larger lighting strings and / or segments to be tested for errors. - By grouping the channels, the bus load on the IC control system can be reduced. For example, only one control signal runs over the bus for all lighting strings being compared.

[0046] - By directly measuring the voltage differences, for example, using a subtractor, the measurement can be achieved with very high resolution over a small voltage range. For example, 8 bits are possible for 3 V. This allows for greater measurement accuracy.

[0047] - Flexible, individual operation of the luminaire strings and / or LED segments to be compared is possible if no error detection is necessary.

[0048] - Temporary individual power supply of the lighting strands can be carried out.

[0049] - Driver ICs with double individual outputs can be used so that the lighting strands can be permanently powered individually.

[0050] - Error detection does not necessarily have to be used or is only used temporarily.

[0051] - No separate measuring line or component on the LED module is required for error detection.

[0052] - Large symbols or lighting patterns with large light strings and / or LED segments to be displayed in a device with the semiconductor light source can be divided into several driver channels.

[0053] - Greater design freedom is possible.

[0054] - Individually defined initial voltages / reference values ​​stored in a non-volatile memory (NVM) offer flexible adaptation to different LED systems that can be installed in the semiconductor light source.

[0055] - Individual initialization is programmable without changing the hardware. - Resetting to a new initial value is programmable.

[0056] - Individually stored limit values ​​in a non-volatile memory offer flexible adaptation to different LED systems in the semiconductor light source.

[0057] - An initial comparison measurement can be carried out with luminaire strings and / or optoelectronic semiconductor chips that are still 100% functional in order to enable an initial calibration to the measuring lines, so that any initial voltage differences no longer have any effect on the error analysis.

[0058] - Greater reliability in error detection can be achieved.

[0059] According to at least one embodiment, within some or all of the lighting strings, some or all of the optoelectronic semiconductor chips are electrically connected in series. This means that pure series connections or mixtures of series connections and parallel connections can be present. For example, the number of parallel connections is at most 50%, at most 30%, or at most 15% of the number of optoelectronic semiconductor chips in the corresponding lighting string.

[0060] According to at least one embodiment, some or all of the luminaire strands are mounted on a common carrier. The common carrier is, for example, a circuit board, such as a printed circuit board or a metal-core board, or even a foil.

[0061] According to at least one embodiment, some or all of the lighting strings are configured to be operated simultaneously. This means that when one lighting string is operated, all other associated lighting strings are also operated. In other words, the associated lighting strings have the same or approximately the same operating times. Only lighting strings associated with a comparison unit need to be operated simultaneously. Other lighting strings can be operated independently.

[0062] According to at least one embodiment, the operating times of the associated lighting strands differ from one another by a factor of at most 1.2, or by a factor of at most 1.1, or by a factor of at most 1.05. This applies alternatively or additionally to the optoelectronic semiconductor chips of the respective lighting strands.

[0063] According to at least one embodiment, temperatures of the associated light strings differ from one another by at most 10°C, or by at most 5°C, or by at most 2°C. This means, for example, that all optoelectronic semiconductor chips of the respective light strings have the same or approximately the same temperature during operation of the semiconductor light source.

[0064] According to at least one embodiment, the relative ambient humidity of the associated lighting strings differs from one another by a maximum of ten percentage points, by a maximum of five percentage points, or by a maximum of two percentage points. This means, for example, that all optoelectronic semiconductor chips of the respective lighting strings are operated at the same or approximately the same humidity. Thus, the associated lighting strings are, in particular, configured to be operated in the same manner, such that the operating temperature, the operating humidity, and / or the operating time or aging are the same or approximately the same.

[0065] According to at least one embodiment, the mutually associated luminaire strands are located close to one another. This means, for example, that a distance between adjacent luminaire strands is at most 1 cm, or at most 4 mm, or at most 2 mm. These distances can also apply to adjacent optoelectronic semiconductor chips within the luminaire strands. The distance between the adjacent luminaire strands is, for example, a distance between supports of the respective luminaire strands and / or a distance between optoelectronic semiconductor chips of the respective luminaire strands.

[0066] According to at least one embodiment, the at least one comparison module is configured to determine differences in the numerical values ​​for the lighting strings and to compare them with at least one threshold value stored in the comparison module. The threshold value can also be referred to as a limit value. For example, it is assumed that an error is present if the differences, for example, in the forward voltages of the lighting strings in question are below and / or above certain limit values.

[0067] According to at least one embodiment, some or all of the luminaire strands have the same construction. Identical construction means, for example, that these luminaire strands have the same number and / or the same composition of optoelectronic semiconductor chips. For example, these luminaire strands each have a certain number A of LED chips for a first color and a certain number B of LED chips for a second color and optionally a certain number C of LED chips for a third color and optionally a certain number D of LED chips for a fourth color. Identical construction can additionally mean that the same additional active electrical components are present, such as sensors or diodes for protection against electrostatic discharges.

[0068] According to at least one embodiment, the same threshold value(s) apply to similarly constructed luminaire strings. Thus, for fault analysis purposes, these luminaire strings can be treated equally.

[0069] According to at least one embodiment, some or all of the luminaire strands are constructed differently. This means, for example, that these luminaire strands have different numbers of optoelectronic semiconductor chips and / or different compositions of optoelectronic semiconductor chips, i.e., in particular, different ensembles of emission colors of the optoelectronic semiconductor chips.

[0070] According to at least one embodiment, different threshold values ​​apply to differently constructed lighting strings. This makes it possible to extend the error analysis to differently constructed lighting strings.

[0071] According to at least one embodiment, the

[0072] The comparison module comprises at least one memory unit, such as an NVM. Optionally, the at least one memory unit is configured to dynamically store the at least one threshold value. Dynamic means that the at least one threshold value can be changed, either by the control unit itself or externally, for example, via a wired connection or a wireless data connection.

[0073] According to at least one embodiment, the lighting strands are configured to be operated with an identical total current strength other than zero when the electrical parameter is detected. This means that the total current strengths through the respective lighting strands differ from one another, for example, by a maximum factor of 1.1, by a maximum factor of 1.05, or by a maximum factor of 1.02. In particular, the electrical parameter is the forward voltage of the respective lighting strands.

[0074] According to at least one embodiment, the comparison module comprises one or more measurement analog-to-digital converters (measurement ADCs). The ADC, which determines the numerical values ​​of the lighting strings of the at least one electrical parameter, can thus be an integral component of the control unit, i.e., the driver IC.

[0075] According to at least one embodiment, all numerical values ​​of the at least one electrical parameter are acquired using the same measurement ADC. The numerical values ​​are acquired, for example, using time-division multiplexing, so that the relevant channels are measured sequentially.

[0076] According to at least one embodiment, the comparison module is configured to record a time profile of the at least one electrical parameter. This means, for example, that the relevant numerical values ​​are recorded multiple times. The recording can be periodic or aperiodic. For example, a recording frequency is at least once per hour or at least once per minute or at least 1 Hz or at least 10 Hz or at least 50 Hz. Alternatively or additionally, this frequency is at most 1 kHz or at most 0.1 kHz.

[0077] According to at least one embodiment, some or all of the luminaire strands comprise at least two, or at least five, or at least eight, or at least ten of the optoelectronic semiconductor chips. Alternatively or additionally, this number is at most 200, or at most 100, or at most 50.

[0078] According to at least one embodiment, the semiconductor light source comprises at least three or at least four or at least six or at least ten of the luminaire strands. Alternatively or additionally, this number is at most 300 or at most 100 or at most 50.

[0079] According to at least one embodiment, the control unit is set up to compare the numerical values ​​of the lighting strands assigned to this control unit, each in pairs. If, for example, the three numerical values ​​V1, V2, V3 are available for the forward voltage, V1 is compared with V2 and V1 with V2 and V2 with V3. In other words, a rolling comparison can be made. Alternatively, it is possible to compare the numerical values ​​with an average of the numerical values. According to at least one embodiment, the lighting strands are operated with PWM. The measurement of the numerical values, for example for the forward voltage, is preferably carried out during the on-time during which the at least one lighting strand in question is energized. For example, the measurement starts at the beginning of an energization phase, also referred to as the duty cycle, and lasts a maximum of as long as the duty cycle.The measurement of the assigned numerical value is then preferably coupled to the corresponding PWM frequency and synchronized with the PWM control.

[0080] According to at least one embodiment, the lighting strands are combined into several groups of at least two lighting strands each. It is possible for the lighting strands within some or all of the groups to have the same structure. This enables efficient comparison between the lighting strands within the groups.

[0081] The groups can also be referred to as segments. The groups are formed from the individual light strings, which are then compared with each other. Several light strings therefore form a segment, or group.

[0082] According to at least one embodiment, a separate control unit is provided for each group. Alternatively, all groups are assigned to the control unit, or there is at least one control unit to which more than one group is assigned.

[0083] According to at least one embodiment, the at least one control unit is configured to perform the error analysis for each of the groups individually. This means that the error analysis is performed at the group level. Whether an error exists within a group can thus be determined independently of the other groups.

[0084] According to at least one embodiment, some or all of the optoelectronic semiconductor chips are micro-LEDs. A micro-LED is, for example, any light-emitting diode (LED for short), and in particular not a laser, with a particularly small size. It is possible for a growth substrate to be removed in micro-LEDs, so that a height of such micro-LEDs is, for example, in the range of 1.5 pm to 10 pm. Such micro-LEDs can be provided on wafers with holding structures for the micro-LED that can be removed without destruction.

[0085] In principle, a micro-LED does not necessarily have to have a rectangular radiation emission area. For example, a micro-LED can have a radiation emission area that, viewed from above, is less than or equal to 100 pm or less than or equal to 70 pm in every lateral extent of the radiation emission area. For example, in the case of rectangular micro-LEDs, an edge length, particularly viewed from above, is less than or equal to 70 pm or less than or equal to 50 pm.

[0086] The main application of micro-LEDs is currently displays. Micro-LEDs form pixels or sub-pixels and emit light of a defined color. Due to their small pixel size and high density with close spacing, micro-LEDs are suitable for small monolithic displays for applications in the field of augmented reality (AR), particularly for data glasses. In addition, work is being done on other applications, particularly data communications and pixelated lighting applications. In the literature, you can find various notations for micro-LED, such as pLED, p-LED, uLED, u-LED or Micro Light Emitting Diode.

[0087] Furthermore, a measuring method is specified with which a semiconductor light source is operated as described in connection with one or more of the above-mentioned embodiments. Features of the semiconductor light source are therefore also disclosed for the measuring method, and vice versa.

[0088] In at least one embodiment, the measuring method comprises the following steps, in particular in the specified order and / or repeatedly:

[0089] - detecting at least one electrical parameter for the lighting strings, and

[0090] - Using at least one electrical parameter to analyse the faults in the lighting systems.

[0091] A semiconductor light source and a method described herein are explained in more detail below with reference to the drawings using exemplary embodiments. Like reference symbols indicate like elements in the individual figures. However, they are not drawn to scale; rather, individual elements may be exaggerated for clarity.

[0092] It shows :

[0093] Figure 1 is a schematic circuit diagram of an embodiment of a semiconductor light source described here, Figures 2 to 4 are schematic plan views of embodiments of semiconductor light sources described here,

[0094] Figures 5 and 6 are schematic circuit diagrams of embodiments of semiconductor light sources described here, and

[0095] Figure 7 is a schematic block diagram of an embodiment of a measuring method for semiconductor light sources described here.

[0096] Figure 1 schematically illustrates a semiconductor light source 1. The semiconductor light source 1 comprises a plurality of light strings 2. Each of the light strings 2 comprises a plurality of optoelectronic semiconductor chips 21, for example LED chips or LD chips, wherein phosphors can optionally be present. The optoelectronic semiconductor chips 21 within a light string 2 can all be identical in construction, or different optoelectronic semiconductor chips 21 can be combined with one another, for example LED chips with different emission colors. The light strings 2 can be constructed identically or differently from one another.

[0097] Within the lighting strands 2, the optoelectronic semiconductor chips 21 are at least partially present in an electrical series circuit. According to Figure 1, the lighting strands 2 are constructed purely as series circuits. In Figure 2, only two lighting strands 2 are shown as an example, but more than two lighting strands 2 can equally well be present. Furthermore, the semiconductor light source 1 comprises a control unit 3. A comparison module 31 is located in the control unit 3. All of the lighting strands 2 are connected to the control unit 3, for example electrically parallel to one another. Thus, the control unit 3 can have its own electrical output for each of the lighting strands 2.

[0098] The lighting strands 2 are operated in the same way. This means in particular that the lighting strands 2 are close to one another. For example, the distance between the lighting strands 2 is at most 5 mm or at most 2 mm. This distance is, for example, a distance between the nearest optoelectronic semiconductor chips 21 of the two lighting strands 2. Due to the small distance between them, the same ambient conditions, such as temperature and humidity, exist for both lighting strands 2. The lighting strands 2 can also be operated with the same current II = 12, so that the same electrical operating conditions can exist. In order to compensate for aging of the lighting strands 2 relative to one another, it is possible for the lighting strands 2 to be operated with the same operating times, for example synchronously with one another.

[0099] The comparison module 31 is set up to compare one or more electrical parameters P of the lighting strands 2 with one another. For example, the parameter P is an electrical forward voltage with numerical values ​​V1, V2 across the lighting strands 2. Alternative or additional electrical parameters P are, for example, reaction times for a voltage build-up or drop, current intensities or capacitances. This is also possible in all other exemplary embodiments. One or more threshold values ​​can be stored in the comparison module 31. The numerical values ​​of the parameter P of the lighting strands 2 are then compared with one another in the comparison module 31, for example one or more differences are formed from the determined numerical values, for example by subtracting the numerical values ​​from one another. The resulting at least one difference is compared with the threshold values.Based on the comparison, it can be decided whether there is a fault in one of the lighting strands 2 or not.

[0100] In the example of Figure 1, a voltage difference dV = VI - V2 or dV = | vi - V2 | is compared with at least one threshold value. If dV lies outside a predefined value range for dV, an error exists, and the comparison module 31 can output an error message.

[0101] As in all other examples, it is possible to subtract original values ​​from the numerical values ​​of the parameter P, as measured at a specific point in time. In other words, only a drift or shift in the numerical values ​​of the parameter P relative to an initial value is taken into account and compared with at least one threshold value.

[0102] In the example of Figure 1 this means that the difference dV can be given as : dV = (V1 -V1 Q ) - V2 -V2 Q ) or dV = , where V1 Q and V2 Q are the numerical values ​​of the forward voltage at an operating time of 0 h, i.e., of the luminaire strings 2 currently being produced. By taking such a measurement at 0 h of operating hours, variations in the parameter of the luminaire strings 2, which may be caused, for example, by binning, can be eliminated. The numerical values ​​VI, V2 can be measured repeatedly, for example periodically, and then compared with the threshold values ​​in order to perform the error analysis.

[0103] By determining the at least one parameter P for similarly operated, in particular identically constructed, luminaire strings 2, effects due to otherwise different environmental influences or aging can be reduced or eliminated and a precise error determination of the luminaire strings 2 is possible.

[0104] For example, the voltage differences that occur in the event of a fault in one of the optoelectronic semiconductor chips 21 in one of the lighting strings 2 are in the order of magnitude of 1 V or 100 mV, for example, with ten optoelectronic semiconductor chips 21 in a series circuit. Voltage differences due to temperature changes are already in the mV range per optoelectronic semiconductor chip 21, and different operating times can also lead to voltage differences of several tens of mV. By comparing the parameters of the similarly operated, closely located lighting strings 2, the accuracy of the fault analysis can be significantly increased.

[0105] Figures 2 to 4 show several examples of the light strings 2. According to Figure 2, a total of seven optoelectronic semiconductor chips 21 are present, for example, in an alternating arrangement of first semiconductor chips 21A for emitting green light and second semiconductor chips 21B for emitting red light. All semiconductor chips 21A, 21B can be present in a linear arrangement on a common carrier 4.

[0106] Furthermore, as in all other examples, it is possible for the first semiconductor chips 21A to be assigned to a first lighting strand 2 and the second semiconductor chips 21B to be assigned to a second lighting strand, and thus for the semiconductor chips 21A, 21B of different lighting strands 2 to be arranged in a linearly regular alternating manner, in a linearly randomly alternating manner, or in a two-dimensionally intermixed manner, for example, on a common carrier 4. The semiconductor chips 21A, 21B, 21C, 21D, 21E illustrated in Figures 2 to 4 with different emission colors can thus also symbolize different lighting strands 2.

[0107] Figure 3 shows that there are five third and five fourth semiconductor chips 21C, 21D, each arranged in its own row. The semiconductor chips 21C, on the one hand, and the semiconductor chips 21D, on the other hand, can each be arranged in their own series circuit, whereby these two series circuits can be connected in parallel. For example, the semiconductor chips 21C are configured to emit blue light and the semiconductor chips 21D are configured to emit violet or ultraviolet light, whereby, in particular, phosphors not shown can be assigned to the semiconductor chips 21D.

[0108] According to Figure 4, the lighting strand 2 is divided into a plurality of carriers 4, such as circuit boards. Each of the carriers 4 can comprise triples or quadruples of semiconductor chips 21, for example semiconductor chips 21A for green light, semiconductor chips 21B for red light and semiconductor chips 21C for blue light and optionally semiconductor chips 21E for white light. The carriers 4 can be connected to one another by means of an electrical connecting line 42. Furthermore, an electrical connection 41 for connecting to the control unit 3, not shown in Figure 4, can be present.

[0109] The luminaire strands 2 of Figures 1, 5 and 6 can, for example, be constructed as illustrated in connection with Figures 2 to 4, whereby mixtures of the designs of Figures 2 to 4 can also be realized.

[0110] Furthermore, the statements relating to Figure 1 apply equally to Figures 2 to 4, and vice versa.

[0111] Figure 5 shows that the semiconductor light source 1 has a plurality of groups 5A, 5B, 5C of light strings 2. Each group 5A, 5B, 5C has its own control unit 3. Each of the groups 5A, 5B, 5C has the same ambient conditions and / or the light strings 2 within each of the groups 5A, 5B, 5C are operated in the same way, for example with the same current, and / or the light strings 2 within each of the groups 5A, 5B, 5C have the same structure. This allows a precise fault analysis to be carried out for each of the groups.

[0112] The groups 5A, 5B are constructed as illustrated in connection with Figure 1. In connection with the group 5C it is shown that more than three lighting strands 2 can be present, for example N-4 lighting strands 2, where N is a natural number greater than or equal to seven, so that the group 5C has at least three of the lighting strands 2. The electrical parameter P which is used for the error analysis is, for example, the forward voltage, so that V5 ... VN numerical values ​​for the forward voltage for the group 5C are recorded. These numerical values ​​are, for example, compared with one another on a rolling basis in order to determine the differences dV, so that a numerical value Vj_ is compared with a numerical value Vj with Vj_ , Vj 6 [ 5 ; N] pj with ifj . An error message is only issued, for example, when a minimum number of differences dV lies within an error range.

[0113] The differences dV between the voltages VI . . VN are determined directly, for example, using a subtractor circuit. It is possible that within each of the groups 5A, 5B, 5C, the measurement of the numerical values ​​is performed on exactly one ADC of the control unit 3. This means that the various lighting strands 2 within each of the groups 5A, 5B, 5C can be measured via multiplexing.

[0114] To control the lighting strands 2, it is possible for only one control signal to be sent to the control units 3 per group 5A, 5B, 5C, or per several of the lighting strands 2. For example, the lighting strands 2 within group 5A or across groups 5A, 5B are all operated with the same control signal. This makes it possible to reduce the load on a data bus, while still allowing a sufficiently high number of lighting strands 2 to be used to enable reliable fault analysis. For similar lighting strands 2, pairing can thus be carried out during control in order to reduce the amount of bus data required.

[0115] Furthermore, the statements made in relation to Figures 1 to 4 apply equally to Figure 5, and vice versa.

[0116] Figure 6 illustrates that combined

[0117] Series connections and parallel connections may exist within the lighting strings 2. It is possible that the lighting strings 2 within a group 5 are again operated with the same current in order to conduct a reliable fault analysis.

[0118] As is possible in all other examples, differently constructed lighting strings 2 can be combined within a group 5. At least one threshold value for the difference dV must be set accordingly. It is possible that at least one threshold value can also be programmed during operation and not only at the factory, for example, only after the lighting strings 2 have been installed.

[0119] Furthermore, the statements made regarding Figures 1 to 5 apply equally to Figure 6, and vice versa.

[0120] Figure 7 shows a block diagram of the measurement procedure.

[0121] The described process steps are preceded, for example, by measuring the numerical values ​​for at least one electrical parameter at the beginning of operation of the luminaire strings 2 in order to obtain 0 h values. This can be done at the factory. These 0 h values ​​can, for example, serve as starting values ​​for calculating a difference.

[0122] In step S1, the numerical values ​​for the individual lighting strands are then measured, and a difference is calculated, for example. Step S1 can include subtracting the 0 h values ​​from the currently determined difference in order to reduce or eliminate variance due to, for example, binning tolerances. When measuring the numerical values, lighting strands 2 are operated, for example, with the same current; if no numerical values ​​are being determined, it is also possible that lighting strands 2 are operated with different currents.

[0123] In step S2, the error analysis is then carried out, for example based on the difference formation of the forward voltages and / or a comparison with the at least one threshold value.

[0124] The steps SI , S2 can be repeated cyclically .

[0125] Furthermore, the statements made in relation to Figures 1 to 6 apply equally to Figure 7, and vice versa.

[0126] The components shown in the figures preferably follow one another in the specified order, in particular directly one after the other, unless otherwise stated. Components that are not touching in the figures are preferably spaced apart. If lines are drawn parallel to one another, the associated surfaces are preferably also aligned parallel to one another. Furthermore, the relative positions of the drawn components to one another are correctly reproduced in the figures, unless otherwise stated.

[0127] The invention described here is not limited by the description based on the exemplary embodiments. Rather, the invention encompasses any novel feature and any combination of features, including in particular any combination of features in the patent claims, even if this feature or combination itself is not explicitly stated in the patent claims or exemplary embodiments.

[0128] This patent application claims priority from German patent application 10 2023 119 778.9, the disclosure of which is hereby incorporated by reference.

[0129] Reference symbol list

[0130] 1 semiconductor light source

[0131] 2 lighting string 21 optoelectronic semiconductor chip

[0132] 3 Control unit

[0133] 31 Comparison module

[0134] 32 storage units

[0135] 4 carriers 41 electrical connection

[0136] 42 electrical connecting cable

[0137] 5 Group dV voltage difference

[0138] I total current through a phase P electrical parameter

[0139] S Process step

[0140] V forward voltage

Claims

Patent claims 1. Semiconductor light source (1) with - several lighting strands (2), at least some of which are combined in several groups (5) and at least one of the groups (5) comprises at least three of the lighting strands (2), and - a control unit (3), wherein - each of the luminaire strands (2) comprises several optoelectronic semiconductor chips (21) for generating light, - the lighting strands (2) within each of the groups (5) are operated in the same way, and - the control unit (3) comprises a comparison module (31) which is designed to detect at least one electrical parameter (P) from each of the lighting strands (2) and to use numerical values ​​for the individual lighting strands (2) of the detected at least one electrical parameter (P) for a fault analysis, - the comparison module (31) is designed to record a time profile of the electrical parameter (P), - the control unit (3) is designed to carry out an error analysis for each of the groups (5) individually, and - the control unit (3) is configured to compare the numerical values ​​of the lighting strands (2) for the at least one group (5) comprising at least three of the lighting strands (2) in pairs and to output an error message if a minimum number of differences between the numerical values ​​lies within an error range.

2. Semiconductor light source (1) according to the preceding claim, wherein within each of the luminaire strands (2) at least some of the optoelectronic semiconductor chips (21) are electrically connected in series.

3. Semiconductor light source (1) according to one of the preceding claims, in which all light strands (2) are mounted on a common carrier (4) and are designed to be operated simultaneously.

4. Semiconductor light source (1) according to one of the preceding claims, in which all light strings (2) are designed to be operated in the same way, so that - temperatures of the luminaire strands (2) do not vary by more than 5 °C, - operating times of the lighting strings (2) by a maximum factor of 1 , 1 and - a relative ambient humidity of the luminaire strands (2) differs from each other by a maximum of five percentage points.

5. Semiconductor light source (1) according to one of the preceding claims, in which the comparison module (31) is configured to determine differences between the numerical values ​​for the luminaire strands (2) and to compare them with at least one threshold value stored in the comparison module (31).

6. Semiconductor light source (1) according to the preceding claim, wherein at least some of the luminaire strands (2) are constructed identically and the same at least one threshold value applies to these luminaire strands (2).

7. Semiconductor light source (1) according to one of the two preceding claims, wherein at least some of the luminaire strands (2) are constructed differently from one another and different threshold values ​​apply to these luminaire strands (2).

8. Semiconductor light source (1) according to one of the three preceding claims, wherein the comparison module (31) comprises a memory unit (32) which is configured to dynamically store the at least one threshold value.

9. Semiconductor light source (1) according to the preceding claim, wherein the electrical parameter (P) is a forward voltage and the luminaire strands (2) are designed to be operated with an equal total current intensity different from zero when the electrical parameter (P) is detected.

10. Semiconductor light source (1) according to one of the preceding claims, wherein the comparison module (31) comprises a measuring analog-to-digital converter, measuring ADC, wherein all numerical values ​​are recorded with this measuring ADC.

11. Semiconductor light source (1) according to one of the preceding claims, wherein the comparison module (31) is configured to record the time course of the electrical parameter (P) with a recording frequency of at least once per hour and of at most 0.1 kHz.

12. Semiconductor light source (1) according to one of the preceding Claims, in which the luminaire strands (2) each comprise at least five and at most 100 of the optoelectronic semiconductor chips (21).

13. Semiconductor light source (1) according to one of the preceding claims, wherein a distance between adjacent light strands (2) is at most 1 cm.

14. Semiconductor light source (1) according to one of the preceding claims, wherein all groups (5) comprise either exactly two or exactly three of the luminaire strands (2).

15. Semiconductor light source (1) according to one of the preceding claims, which comprises at least ten of the luminaire strands (2), wherein several of the groups (5) comprise at least three of the luminaire strands (2).

16. Measuring method for a semiconductor light source (1) according to one of the preceding claims, comprising the steps: - detecting the at least one electrical parameter (P) for the lighting strands (2), and - Using the at least one electrical parameter (P) for a fault analysis of the lighting strands (2).

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