SEMI-CONDUCT LIGHT SOURCE AND MEASURING METHOD

Abstract

In at least one embodiment, the semiconductor light source (1) comprises several light strings (2) and a control unit (3), wherein - each of the light strings (2) comprises several optoelectronic semiconductor chips (21) for light generation, such as µLEDs, - the lighting strings (2) are operated in the same manner, and - the control unit (3) includes a comparison module (31) which is configured to detect at least one electrical parameter (P) from each of the lighting strings (2) and to use numerical values ​​for the individual lighting strings (2) of the detected at least one electrical parameter (P) for fault analysis.

Description

[0001] A semiconductor light source is specified. Furthermore, a measurement method for such a semiconductor light source is described.

[0002] Documents US 7 878 ​​103 B1 and US 2014 / 0 152 180 A1 concern LED circuits.

[0003] One task to be solved is to specify a semiconductor light source in which defects can be reliably detected.

[0004] This problem is solved, among other things, by a semiconductor light source and by a measurement method with the features of the independent claims. Preferred embodiments are the subject of the dependent claims.

[0005] According to at least one embodiment, the semiconductor light source comprises several light strings. Each light string comprises one or more optoelectronic semiconductor chips. The semiconductor chips are configured for generating radiation, in particular visible light. The visible light can be generated directly in a semiconductor layer sequence of the respective optoelectronic semiconductor chip, or the respective optoelectronic semiconductor chip can be associated with at least one phosphor that converts at least part of the radiation emitted directly from the respective optoelectronic semiconductor chip into radiation of a different wavelength.

[0006] The semiconductor layer sequences of optoelectronic semiconductor chips each have at least one active zone, which is configured to generate radiation via electroluminescence during operation. The generated radiation is incoherent in the case of a light-emitting diode chip (LED chip) or, in the case of a laser diode chip (LD chip), particularly coherent. The semiconductor layer sequences are preferably based on a III-V compound semiconductor material. The semiconductor material is, for example, a nitride compound semiconductor such as Al. n In 1-n-m Ga m N or a phosphide compound semiconductor material such as Al n In 1-n-m Ga m P or also an arsenide compound semiconductor material such as Al n In 1-n-m Ga m As or like Al n Ga m In 1-n-m As k P 1-k, where 0 ≤ n ≤ 1, 0 ≤ m ≤ 1, n + m ≤ 1, and 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, n + m ≤ 0.95, and 0 < k ≤ 0.5 hold true. The semiconductor layer sequences may contain dopants and 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 specified, even though these may be partially replaced and / or supplemented by small amounts of other substances.

[0007] Several types of optoelectronic semiconductor chips can be combined in the lighting circuits. The term 'types' refers, for example, to different emission colors. It is possible that the optoelectronic semiconductor chips are the sole light source of the semiconductor light source.

[0008] 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 configured to electrically control and operate the optoelectronic semiconductor chips, in particular the optoelectronic semiconductor chips grouped into lighting strings. For example, the at least one control unit determines the current applied to the individual lighting strings 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 associated 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 environmental conditions, such as temperature and humidity, and / or are operated synchronously with each other, 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 comparator module. The at least one comparator module is configured to detect at least one electrical parameter from each of the lighting strings. For example, the electrical parameter is a forward voltage. A numerical value of the electrical parameter is determined for each of the lighting strings. For example, the forward voltage is detected for each of the lighting strings.

[0011] According to at least one embodiment, the at least one comparison module is configured to use the numerical values ​​of the detected at least one electrical parameter for the individual lighting strings for fault analysis. This means, for example, that the numerical values, such as the individual forward voltages of the lighting strings, are compared with each other. If a comparison reveals a deviation that is too large from a target value, such as a threshold value, or a target value range, such as a range of values ​​between two threshold values, the at least one comparison module detects a fault. The fault is, for example, a defect or a failure of at least one optoelectronic semiconductor chip in the at least one affected lighting string.

[0012] It is possible that at least one comparison module is configured to issue an error message if the error analysis reveals a fault. The error message is then sent, for example, to a control unit of a device, such as a motor vehicle, in which the semiconductor light source is installed.

[0013] In at least one embodiment, the semiconductor light source comprises several light strings and a control unit, wherein - each of the lighting strands comprises one or more optoelectronic semiconductor chips for light generation, - the lighting strings are operated in the same way, and - the control unit includes a comparison module that is set up to record at least one electrical parameter from each of the lighting strings and to use numerical values ​​for the individual lighting strings of the recorded at least one electrical parameter for fault analysis.

[0014] For example, fault detection of individual LEDs in LED segments or lighting strings is based on voltage measurement. This means, for instance, that single-LED fault detection is possible in larger LED segments. A fault could be, for example, an open electrical circuit or a short circuit. Fault detection can be independent of environmental influences, such as temperature, or of the aging of the optoelectronic semiconductor chips.

[0015] In some LED applications, particularly in the automotive industry, the failure of individual LEDs within a luminaire is undesirable, as such failures could compromise safety or negatively affect the design. Therefore, fault detection of individual short-circuited or open LEDs is necessary.

[0016] In larger luminaires with high LED density, series or parallel connection of LEDs is common, making electronic monitoring of a single LED generally impossible. When 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 and / or number of parallel strings.

[0017] Short circuits or open connections in LED circuits can be detected by measuring the forward voltage and comparing the value to a corresponding reference. In series and / or parallel connections of LEDs, variations in forward voltage, which can occur due to binning, temperature, and / or aging of the individual LEDs, can accumulate to such an extent that, in the worst case, the cumulative variation exceeds the signal being measured—that is, a voltage change caused by a short circuit or open contact of an LED. Binning refers specifically to the classification of LEDs into a particular class, where all LEDs within the class exhibit the same properties within predefined tolerances, such as the same emission color or the same forward voltage.

[0018] The semiconductor light source described here solves this problem, for example, by comparing the forward voltages of several similar series and / or parallel circuits. By using a reference, co-occurring disturbances, such as temperature and potentially aging, can be averaged out during measurement, thus increasing the sensitivity of fault detection.

[0019] The lighting strings and LED segments are operated primarily by means of a driver IC, whose driver channels can be configured as current sources or sinks. The number of LEDs in the circuit, i.e., per lighting string, is, for example, 1, 5, or 10. Interference is minimized by a local, adjacent arrangement of two or more LED segments or lighting strings, which are operated primarily in common mode, and by the measurement evaluation within the driver IC, in order to enable fault detection in larger series and / or parallel circuits. For example, the difference in forward voltages between any two adjacent lighting strings within a segment is calculated and compared to a corresponding threshold value. If the difference in forward voltages exceeds the threshold value, a fault is registered.Monitoring of the lighting strings and LED segments, as well as fault detection, is integrated into the driver IC, for example. IC stands for integrated circuit.

[0020] This allows multiple locally adjacent lighting strings within a segment to be used as references to each other. The driver IC assigns the lighting strings and / or segments that serve as references to one another. By using a driver IC with ADC measurements on the driver channels, individual initial values ​​and error limits can be stored for each lighting string and / or segment. A single ADC within the IC can be used for voltage measurement, similar to a differential measurement, so that individual channels to be compared are routed to the same ADC, corresponding to multiplexing. This eliminates the error deviation on the absolute measured value of the ADC and thus increases the detection accuracy.

[0021] The semiconductor light source described here incorporates, for example, the following aspects, individually or in any combination: - A comparative system consisting of two or more individual LED light strings within an LED segment is operated, which are exposed to very similar environmental conditions and are, for example, located close to each other locally. - Several such systems can be installed on one LED module, so that the semiconductor light source can be composed of several groups of light strings. - Individual / flexible grouping of the driver channels to be compared is possible. - It is possible to determine the voltage differences from the individually measured voltage values ​​of the lighting strings within a system. - It is possible to operate the lighting strings and / or LED segments to be compared within a system using constant current sources or constant current sinks with ideally the same current. - Different temperatures of the lighting strings and / or segments being compared can be avoided. - Identical operating conditions for the lighting strings and / or segments being compared, in particular identical aging, can be ensured. - Individually defined initial / reference values ​​for the voltage at a defined current in a lighting string and / or segment can be stored in a non-volatile memory. - Measured values ​​from the production line can be used as a starting value, for example a starting value, also known as the 0 h value. Newly read reference values ​​can be taken into account. - A limit value for the voltage deviation at a defined current, tailored to the system, in particular to two closely spaced light strings and / or segments, can be stored in a non-volatile memory. - 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 individually set. - It is possible to maintain error tolerances, for example 6-sigma ranges. - Repetitive measurements, for example at 10 ms intervals, of the voltage drops across the lighting strings and / or segments to be compared at a defined current can be measured directly at the driver channel using an ADC. - When using pulse width modulation, or PWM for short, measurements can be taken during an on-time. - An evaluation of the differential voltage of the system at a defined current is feasible. - If the differential value between the lighting strings and / or segments being compared exceeds the set limit, an error may be registered. - Individual control of the driver channels is possible. - Switching off lighting strings and / or segments in case of a fault is possible, either as an alternative or in addition to feedback to a higher-level control unit.

[0022] The semiconductor light source described here can be used to achieve, for example, the following effects, individually or in any combination: - Due to similar environmental conditions, voltage-altering influences, such as temperature, humidity and / or corrosion, affect both lighting strings and / or LED segments being compared equally. - The disturbances affect the lighting strings and / or segments being compared equally and are eliminated in the comparative measurement, allowing larger lighting strings and / or segments to be checked for faults. - By grouping the channels, the bus load in controlling the IC can be reduced. For example, only one control signal runs over the bus for all lighting strings being compared. - By directly measuring voltage differences, for example using a subtractor, very high resolution can be achieved over small voltage ranges. For example, 8 bits are possible at, say, 3 V. This allows for higher measurement accuracy. - Flexible, individual operation of the lighting strings and / or LED segments to be compared is possible if no fault detection is necessary. - Temporary individual power supply to the lighting strings can be carried out. - Driver ICs with dual individual outputs can be used, allowing for continuous individual power supply to the lighting strings. - Fault detection does not necessarily have to be used or is only used temporarily. - No separate measuring line or component on the LED module is required for fault detection. - Large symbols or lighting patterns to be displayed in a device with the semiconductor light source, using large light strings and / or LED segments, can be divided across multiple driver channels. - Greater design freedom is possible. - Individually defined initial voltages / reference values ​​stored in a non-volatile memory (NVM) offer flexible adaptation to various LED systems that can be installed in the semiconductor light source. - Individual initialization can be programmed without changing the hardware. - Resetting to a new initial value is programmable. - Individually stored limit values ​​in a non-volatile memory offer flexible adaptation to different LED systems in the semiconductor light source. - An initial comparative measurement can be carried out on 100% functioning lighting strings and / or optoelectronic semiconductor chips to enable an initial calibration to the measuring leads, so that any initial voltage differences no longer have an effect on the fault analysis. - Higher reliability can be achieved in fault detection.

[0023] According to at least one embodiment, some or all of the optoelectronic semiconductor chips within some or all of the lighting strings are electrically connected in series. This means that pure series circuits or mixtures of series and parallel circuits are possible. For example, the number of parallel circuits is at most 50%, 30%, or 15% of the number of optoelectronic semiconductor chips in the respective lighting string.

[0024] According to at least one embodiment, some or all of the light strings are mounted on a common substrate. This common substrate is, for example, a circuit board, such as a printed circuit board or a metal-core circuit board, or even a film.

[0025] According to at least one embodiment, some or all of the lighting strings are configured to operate simultaneously. This means that when one lighting string is operated, all other assigned lighting strings are also operated. In other words, the assigned lighting strings have the same or approximately the same operating times. Only lighting strings assigned to a reference unit need to be operated simultaneously. Other lighting strings can be operated independently.

[0026] According to at least one embodiment, the operating times of the corresponding lighting strings differ from each other 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 strings.

[0027] According to at least one embodiment, the temperatures of the associated lighting strings differ from each other by a maximum of 10 °C, 5 °C, or 2 °C. This means, for example, that all optoelectronic semiconductor chips of the respective lighting strings have the same or approximately the same temperature during operation of the semiconductor light source.

[0028] According to at least one embodiment, the relative ambient humidity of the associated lighting strings differs from each other by no more than ten percentage points, or by no more than five percentage points, or by no more than 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 relative humidity.

[0029] Thus, the corresponding lighting strings are specifically designed to be operated in such a way that the operating temperature, operating humidity and / or operating time or aging are the same or approximately the same.

[0030] According to at least one embodiment, the associated light strings are located close to one another. This means, for example, that the distance between adjacent light strings is at most 1 cm, 4 mm, or 2 mm. These distances can also apply to adjacent optoelectronic semiconductor chips within the light strings. The distance between the adjacent light strings is, for example, a distance between the supports of the respective light strings and / or a distance between optoelectronic semiconductor chips of the respective light strings.

[0031] According to at least one embodiment, the at least one comparator module is configured to determine differences in the numerical values ​​for the lighting strings and compare them with at least one threshold value stored in the comparator module. The threshold value can also be referred to as a limit value. For example, a fault is assumed to exist if the differences in the forward voltages of the relevant lighting strings are below and / or above certain limit values.

[0032] According to at least one embodiment, some or all of the lighting strings have the same construction. Identical construction means, for example, that these lighting strings have the same number and / or composition of optoelectronic semiconductor chips. For example, these lighting strings each have a specific number A of LED chips for a first color, a specific number B of LED chips for a second color, and optionally a specific number C of LED chips for a third color, and optionally a specific number D of LED chips for a fourth color. Identical construction can also mean that the same other active electrical components are present, such as sensors or diodes for protection against electrostatic discharge.

[0033] According to at least one embodiment, the same threshold values ​​apply to identically constructed lighting strings. Therefore, for the purposes of fault analysis, these lighting strings can be treated identically.

[0034] According to at least one embodiment, some or all of the light strings have different structures. This means, for example, that these light strings have different numbers of optoelectronic semiconductor chips and / or different compositions of optoelectronic semiconductor chips, i.e., in particular, differing ensembles of emission colors of the optoelectronic semiconductor chips.

[0035] According to at least one embodiment, different threshold values ​​apply to the differently constructed lighting strings. This makes it possible to extend the fault analysis to differently constructed lighting strings.

[0036] According to at least one embodiment, the comparison module comprises at least one storage unit, such as an NVM. Optionally, the at least one storage unit is configured to dynamically store the at least one threshold value. Dynamically means that the at least one threshold value can be changed, either by the control unit itself or externally, for example via a wired or wireless data connection.

[0037] According to at least one embodiment, the lighting strings are configured to operate with the same non-zero total current when the electrical parameter is detected. This means that the total currents through the respective lighting strings differ from each other by, for example, a factor of no more than 1.1, 1.05, or 1.02. In particular, the electrical parameter is the forward voltage of the respective lighting strings.

[0038] According to at least one embodiment, the comparison module comprises one or more measurement analog-to-digital converters (ADCs). The ADC, which determines the numerical values ​​of the lighting strings for at least one electrical parameter, can thus be an integral part of the control unit, i.e., the driver IC.

[0039] According to at least one embodiment, all numerical values ​​of the at least one electrical parameter are acquired using the same measuring ADC. The numerical values ​​are acquired, for example, by means of time-division multiplexing, so that the relevant channels are measured sequentially.

[0040] According to at least one embodiment, the comparator module is configured to record the time course of 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, the recording frequency is at least once per hour, at least once per minute, at least 1 Hz, 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.

[0041] According to at least one embodiment, some or all of the lighting strings comprise at least two, at least five, at least eight, or at least ten optoelectronic semiconductor chips. Alternatively or additionally, this number is at most 200, at most 100, or at most 50.

[0042] According to at least one embodiment, the semiconductor light source comprises at least three, at least four, at least six, or at least ten of the light strings. Alternatively or additionally, this number is at most 300, at most 100, or at most 50.

[0043] According to at least one embodiment, the control unit is configured to compare the numerical values ​​of the lighting strings assigned to it in pairs. For example, if the three numerical values ​​V1, V2, and V3 are available for the forward voltage, V1 is compared with V2, V1 with V2, and V2 with V3. In other words, a rolling comparison can be performed. Alternatively, it is possible to compare the numerical values ​​with an average of the numerical values.

[0044] According to at least one embodiment, the lighting strings are operated using PWM. The measurement of numerical values, for example, for the forward voltage, is preferably performed during the on-time while the at least one lighting string in question is energized. For example, the measurement starts at the beginning of an energization phase, also known as a duty cycle, and lasts at most as long as the duty cycle. The measurement of the associated numerical value is then preferably coupled to the corresponding PWM frequency and synchronized with the PWM control.

[0045] According to at least one embodiment, the lighting strings are grouped into several groups of at least two lighting strings each. It is possible that the lighting strings within some or all of the groups have the same configuration. This allows for efficient comparison between the lighting strings within the groups.

[0046] The groups can also be referred to as segments. The groups are thus formed from the individual light strings, which are then compared with each other. Several light strings therefore form a segment, i.e., a group.

[0047] According to at least one embodiment, there is a separate control unit for each group. Alternatively, all groups are assigned to one control unit, or there is at least one control unit to which more than one group is assigned.

[0048] According to at least one embodiment, the at least one control unit is configured to perform the fault analysis for each group individually. This means that the fault analysis is performed at the group level. Whether a fault exists within one group can therefore be determined independently of the other groups.

[0049] 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), and in particular not a laser, with a particularly small size. It is possible that a growth substrate is removed in micro-LEDs, so that the height of such micro-LEDs is, for example, in the range of 1.5 µm to 10 µm. Such micro-LEDs can be provided on wafers with support structures that can be removed without damaging the micro-LED.

[0050] A micro-LED does not necessarily have to have a rectangular emission surface. For example, a micro-LED can have an emission surface that, when viewed from above, is less than or equal to 100 µm or less than or equal to 70 µm in any lateral dimension of the emission surface. For example, in rectangular micro-LEDs, one side length, especially when viewed from above, is less than or equal to 70 µm or less than or equal to 50 µm.

[0051] Currently, the primary application for micro-LEDs is in displays. Micro-LEDs form pixels or subpixels 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 augmented reality (AR) applications, particularly for smart glasses. Further applications are also being developed, especially in data communication and pixelated lighting applications. Various notations for micro-LED can be found in the literature, such as µLED, µ-LED, uLED, u-LED, or Micro Light Emitting Diode.

[0052] Furthermore, a measurement method is specified for operating a semiconductor light source, as described in connection with one or more of the embodiments mentioned above. Features of the semiconductor light source are therefore also disclosed for the measurement method, and vice versa.

[0053] In at least one embodiment, the measuring method comprises the following steps, in particular in the specified order and / or repeatedly: - Recording at least one electrical parameter for the lighting strings, and - Using at least one electrical parameter for fault analysis of the lighting strings.

[0054] The following section provides a more detailed explanation of a semiconductor light source and a method described herein, with reference to the drawing and illustrated examples. Identical reference numerals indicate identical elements in the individual figures. However, the figures are not to scale; rather, individual elements may be exaggerated for clarity.

[0055] They show: Fig. 1 a schematic circuit diagram of an embodiment of a semiconductor light source described herein, Fig. 2 to 4 schematic top views of exemplary embodiments of semiconductor light sources described herein, Fig. 5 and Fig. 6 schematic circuit diagrams of exemplary embodiments of semiconductor light sources described herein, and Fig. 7 a schematic block diagram of an embodiment of a measurement method for semiconductor light sources described here.

[0056] In Fig. Figure 1 schematically illustrates a semiconductor light source 1. The semiconductor light source 1 comprises several light strings 2. Each of the light strings 2 comprises several optoelectronic semiconductor chips 21, for example, LED chips or LD chips, and may optionally include phosphors. 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, for example, LED chips with different emission colors. The light strings 2 can have the same or different structures.

[0057] Within the lighting strings 2, the optoelectronic semiconductor chips 21 are at least partially arranged in an electrical series circuit. According to Fig. 1. The lighting strings 2 are configured as pure series circuits. In Fig. The figures shown are only two light strings 2 as an example; however, there can be more than two light strings 2.

[0058] Furthermore, the semiconductor light source 1 includes a control unit 3. A comparator module 31 is located in the control unit 3. All lighting strings 2 are connected to the control unit 3, for example, electrically in parallel to each other. Thus, the control unit 3 can have a separate electrical output for each of the lighting strings 2.

[0059] The lighting strings 2 are operated in the same manner. This means, in particular, that the lighting strings 2 are located close to each other. For example, the distance between the lighting strings 2 is at most 5 mm or at most 2 mm. This distance is, for example, the distance between the nearest optoelectronic semiconductor chips 21 of the two lighting strings 2. Due to the small distance between them, both lighting strings 2 are subject to the same environmental conditions, such as temperature and humidity. The lighting strings 2 can also be operated with the same current I1 = I2, so that the same electrical operating conditions can prevail. To compensate for the aging of the lighting strings 2 relative to each other, it is possible to operate the lighting strings 2 with the same operating times, for example, synchronously.

[0060] The comparison module 31 is designed to compare one or more electrical parameters P of the lighting strings 2. For example, parameter P is an electrical forward voltage with numerical values ​​V1, V2 across the lighting strings 2. Alternative or additional electrical parameters P include, for example, response times for voltage build-up or drop-down, currents, or capacitances. This is also possible in all other embodiments.

[0061] The comparison module 31 can store one or more threshold values. In comparison module 31, the numerical values ​​of parameter P of the lighting strings 2 are then compared with each other. For example, one or more differences are calculated from the determined numerical values, perhaps by subtracting them from one another. The resulting difference (at least one of which is) is then compared with the threshold values. This comparison allows a decision to be made as to whether or not a fault exists in one of the lighting strings 2.

[0062] In the example of the Fig. Accordingly, a voltage difference dV = V1 - V2 or dV = |V1 - V2| is compared with at least one threshold value. If dV lies outside a predefined range of values ​​for dV, an error occurs and the comparison module 31 can output an error message.

[0063] As in all other examples, it is possible to subtract original values ​​from the numerical values ​​of parameter P as measured at a specific time. In other words, only a drift or shift of the numerical values ​​of parameter P relative to an initial value is considered and compared with at least one threshold value.

[0064] In the example of the Fig. This means that the difference dV can then be given by: dV = (V1-V10) - V2-V20) or dV = |(V1-V10) - V2-V20)|, where V10 and V20 are the numerical values ​​of the forward voltage at an operating time of 0 h, i.e., of the luminaire strings 2 that have just been produced. Such a measurement at 0 h of operating time allows variations in the parameter of the luminaire strings 2, which are caused, for example, by binning, to be eliminated. The numerical values ​​V1 and V2 can be measured repeatedly, for example, periodically, and then compared with the threshold values ​​to perform the fault analysis.

[0065] By determining at least one parameter P for identically operated, and in particular identically constructed, lighting strings 2, effects due to otherwise different environmental influences or aging can be reduced or eliminated, and a precise fault determination of the lighting strings 2 is made possible.

[0066] For example, the voltage differences that occur when one of the optoelectronic semiconductor chips 21 in one of the lighting strings 2 fails are on the order of 1 V or 100 mV, for example, when ten optoelectronic semiconductor chips 21 are connected in series. 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. Therefore, by adjusting the parameters of the similarly operated, closely spaced lighting strings 2, the accuracy of the fault analysis can be significantly increased.

[0067] In the Fig. Figures 2 to 4 show several examples of the lighting strings 2. According to Fig. In 2, a total of seven optoelectronic semiconductor chips 21 are present, for example, in an alternating arrangement of first semiconductor chips 21A for the emission of green light and second semiconductor chips 21B for the emission of red light. All semiconductor chips 21A, 21B can be arranged in a linear arrangement on a common support 4.

[0068] Furthermore, as in all other examples, it is possible that the first semiconductor chips 21A are assigned to a first lighting string 2 and the second semiconductor chips 21B to a second lighting string, and thus the semiconductor chips 21A, 21B of different lighting strings 2 are arranged linearly and regularly alternating, linearly and arbitrarily alternating, or two-dimensionally mixed, for example on a common support 4. The Fig. The semiconductor chips 21A, 21B, 21C, 21D, 21E, illustrated with different emission colors, can therefore also symbolize different light strings 2.

[0069] In Fig. Figure 3 shows that five third and five fourth semiconductor chips 21C and 21D are present, each arranged in its own row. The semiconductor chips 21C and 21D can each be arranged in their own series, and 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 to emit violet or ultraviolet light, and phosphors (not shown) can be assigned to the semiconductor chips 21D.

[0070] According to Fig. The lighting string 2 is divided into several carriers 4, such as printed 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, as well as optionally semiconductor chips 21E for white light. The carriers 4 can be connected to each other by means of an electrical connecting line 42. Furthermore, an electrical connection 41 can be provided for connecting to the control unit 3. Fig. 4 not drawn, be present.

[0071] The lighting strands 2 of the Fig. 1, Fig. 5 and Fig. Six can be structured, for example, as in connection with the Fig. 2 to 4 illustrated, including mixtures of the construction types of Fig. 2 to 4 can be realized.

[0072] Furthermore, the statements regarding Fig. 1 in the same way for the Fig. 2 to 4, and vice versa.

[0073] In Fig. Figure 5 shows that the semiconductor light source 1 has several groups 5A, 5B, 5C of lighting strings 2. Each group 5A, 5B, 5C has its own control unit 3. Each of the groups 5A, 5B, 5C has the same environmental conditions and / or the lighting 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 lighting strings 2 within each of the groups 5A, 5B, 5C have the same design. This allows a precise fault analysis to be performed for each of the groups.

[0074] Groups 5A and 5B are structured as described in connection with Fig. Figure 1 illustrates this. In connection with group 5C, it is shown that more than three lighting strings 2 can be present, for example, N-4 lighting strings 2, where N is a natural number greater than or equal to seven, so that group 5C has at least three lighting strings 2. The electrical parameter P, which is used for fault analysis, is, for example, again the forward voltage, so that V5..VN numerical values ​​for the forward voltage of group 5C are recorded. These numerical values ​​are, for example, compared with each other in a rolling manner to determine the differences dV, so that a numerical value V i with a numerical value V j is compared to V i , V j ∈ [5; N] ℕ with i ≠ j. For example, an error message is only issued if a minimum number of differences dV lie within an error range.

[0075] The differences dV between the voltages V1..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 different lighting strings 2 within each of the groups 5A, 5B, 5C can be measured via multiplexing.

[0076] To control the lighting strings 2, it is possible to send only one control signal to the control units 3 per group 5A, 5B, 5C, or per group of several lighting strings 2. For example, the lighting strings 2 within group 5A, or even across groups 5A and 5B, are all operated with the same control signal. This reduces the load on a data bus while still allowing a sufficiently large number of lighting strings 2 to be used for reliable fault analysis. For identical lighting strings 2, pairing can be used during control to reduce the amount of bus data required.

[0077] Furthermore, the statements regarding the Fig. 1 to 4 in the same way for Fig. 5, and vice versa.

[0078] In Fig. Figure 6 illustrates that combined series and parallel circuits can exist within the lighting strings 2. It is possible that the lighting strings 2 within a group 5 are operated with the same current to enable reliable fault analysis.

[0079] As in all other examples, differently configured lighting strings 2 within a group 5 can be combined. The minimum threshold value for the difference dV must be set accordingly. It is possible that this minimum 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.

[0080] Furthermore, the statements regarding the Fig. 1 to 5 in the same way for Fig. 6, and vice versa.

[0081] In Fig. Figure 7 shows a block diagram of the measurement procedure.

[0082] The described process steps begin, for example, with measuring the numerical values ​​for at least one electrical parameter at the start of operation of the lighting strings 2 in order to obtain 0 h values. This can still be done at the factory. These 0 h values ​​can then serve, for example, as starting values ​​for calculating a difference.

[0083] In step S1, the numerical values ​​for the individual lighting strings are measured, and a difference is calculated, for example. Step S1 may include subtracting the 0 h values ​​from the currently determined difference to reduce or eliminate variance due to, for example, binning tolerances. Lighting strings 2 are operated with the same current during the measurement of the numerical values; if no numerical values ​​are currently being determined, it is also possible for lighting strings 2 to be operated with different currents.

[0084] In step S2, the error analysis is then carried out, for example by calculating the difference of the forward voltages and / or by comparing them with at least one threshold value.

[0085] Steps S1 and S2 can be repeated cyclically.

[0086] Furthermore, the statements regarding the Fig. 1 to 6 in the same way for Fig. 7, and vice versa.

[0087] The components shown in the figures preferably follow one another in the specified order, and in particular directly adjacent to one another, unless otherwise described. Components that do not touch each other in the figures preferably have a distance between them. If lines are drawn parallel to each other, the corresponding surfaces are preferably also aligned parallel to each other. Furthermore, the relative positions of the drawn components to each other are correctly represented in the figures, unless otherwise specified.

[0088] The invention described here is not limited by the description based on the exemplary embodiments. Rather, the invention encompasses every new feature as well as every combination of features, which in particular includes every combination of features in the patent claims, even if this feature or combination itself is not explicitly specified in the patent claims or exemplary embodiments. Reference symbol list 1 Semiconductor light source 2 light strings 21 optoelectronic semiconductor chip 3 Control unit 31 Comparison module 32 storage units 4 carriers 41 electrical connection 42 electrical connecting cable Group 5 dV voltage difference Total current through one strand P electrical parameter S process step V forward voltage QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] US 7 878 ​​103 B1

[0002] US 2014 / 0 152 180 A1

[0002]

Claims

[1] Semiconductor light source (1) with - several light strings (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) 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 an error analysis. [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 / or - the relative ambient humidity of the luminaire strands (2) differs by no more than five percentage points. [5] Semiconductor light source (1) according to one of the preceding claims, in which the comparison module (31) is designed to determine differences from 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 measurement analog-to-digital converter, measurement ADC, where all numerical values ​​are recorded with this measurement ADC. [11] Semiconductor light source (1) according to one of the preceding claims, wherein the comparison module (31) is configured to detect a time profile of the electrical parameter (P). [12] Semiconductor light source (1) according to one of the preceding claims, in which the light strings (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, which comprises at least three of the luminaire strands (2), wherein the control unit (3) is designed to compare the numerical values ​​of the lighting strands (2) in pairs. [15] Semiconductor light source (1) according to one of the preceding claims, which comprises at least four of the luminaire strands (2), wherein the lighting strands (2) are combined into several groups (5) of at least two of the lighting strands (2) each and the control unit (3) is designed to carry out the error analysis for each of the groups (5) individually. [16] Measuring method for a semiconductor light source (1) according to one of the preceding claims, comprising the steps: - detecting 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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