DE102015120551B4 - Device and method for determining an aging information of an LED module - Google Patents

Abstract

The invention relates to a device for determining an aging information of an LED module, comprising: a memory unit for storing a voltage-age characteristic of the LED module, a voltage input for reading in a forward voltage of the LED module, and an evaluation unit for determining the aging information based on the voltage-age characteristic and the forward voltage, wherein the memory unit is configured to store voltage-age characteristics for a plurality of LED modules, and wherein the Device further comprises a selection device for determining a voltage-age characteristic to be used, wherein the selection device is adapted to determine the voltage-age characteristic to be used based on the read forward voltage.

Description

The invention relates to a device for determining an aging information of an LED module. The invention also relates to an LED module and a method for determining an aging information of an LED module.

LEDs typically have a longer life expectancy than traditional bulbs such. As incandescent or even compact fluorescent lamps. Nevertheless, LEDs have aging phenomena such. B. a decreasing luminous flux. There is thus a need to be able to determine an aging of an LED module.

It is known that an aging of an LED module can be detected by a light sensor arranged in or on the LED module. However, this has the disadvantage that the light sensor z. B. may be disturbed by stray light and a suitable attachment of the light sensor must be provided in the vicinity of the LEDs.

It is also known to make statements about the progress of aging through theoretical assumptions about aging. For example, it can be assumed that a fixed maximum life expectancy of the LEDs and thus made by recording the duration of the light, a statement about the aging. This can but z. B. Production fluctuations that cause individual LED modules to age earlier than others are not detected.

WO 2013/160446 discloses an arrangement for assessing the condition of an electronic unit used for lighting purposes. In the process, a point in a reference space is to be assigned to different physical measured values and it is to be recognized whether this point lies within a predefined permissible reference range.

US 2011/0089855 A1 discloses a driver circuit for semiconductor light sources having a constant current light source. A controller in a test mode estimates the degree of light source degeneration due to a feedback voltage and adjusts the constant current light source to compensate for the aging of the light source.

Other driver circuits for semiconductor light sources, which also determine from physical or electrical parameters conclusions about the degree of aging of connected semiconductor light sources, are from the DE 10 2010 039 012 A1 . US 2003/0071821 A1 and the DE 10 2009 017 989 A1 known.

It is an object of the present invention to provide an apparatus and a method which enables a reliable determination of an aging information of an LED module.

The object is achieved by a device according to claim 1 and by a method according to claim 11.

The knowledge of the aging voltage characteristic allows the device to determine aging information from the read forward voltage. Thus, aging information can be determined with little effort, taking into account not only theoretical assumptions about aging, but also actual measured values of the LED module. This makes it possible to detect even premature aging of an LED module.

The voltage input may be an analog input and the device may include an A / D converter. In other embodiments of the invention, the voltage input is a digital input and a forward voltage of the LED module is converted outside the LED module into a digital signal.

The memory unit can, for. B. store only a single parameter that describes the aging curve. For example, the temporal evolution of the forward voltage could be described as the aging progresses through a constant slope (from an initial forward voltage) and the stored parameter may be the value of the slope (positive or negative). In other embodiments of the invention, the memory unit is configured to store further information about the temporal evolution of the forward voltage. The memory unit may be programmable, d. H. comprising a writable memory. In other embodiments, the memory unit has a memory that is written once (eg, during production) and can not be changed thereafter.

It is understood that in embodiments of the invention, the memory unit and the evaluation unit can be realized as a unit. For example, a processor may be programmed to function both as a memory unit and as an evaluation unit.

The times at which the reading in of the forward voltage takes place can be at regular intervals from one another. For example, the device may include a D / A converter that reads in forward voltages at a fixed clock rate. For example, the forward voltage may be at regular intervals of several seconds or be read in for several minutes. Since a rather slow change of the forward voltage is to be assumed, the device can advantageously be designed to read in at intervals of more than 10 minutes, preferably more than 100 minutes.

The forward voltage can be tapped at the positive and negative terminals of the LED module. The LED module may be configured to be powered by a constant current source. This is the case in particular when the LED module does not have its own control electronics.

According to a further embodiment of the invention, the device further has a temperature input for reading in a temperature of the LED module, wherein the evaluation unit is designed to determine the aging information based on the read-in temperature.

This has the advantage that an even more accurate determination of the aging information is possible because the aging of the LED module also depends on the ambient temperature. The temperature input can also be a digital input or an analogue input.

In a further embodiment of the invention it is provided that the device further comprises a look-up table which associates the forward voltage of the LED module with aging information, in particular a life expectancy and / or a residual life expectancy.

The use of a look-up table has the advantage that a reliable determination of the aging information is possible even for more complicated aging-voltage characteristics. For example, the time-voltage curve of an LED module may have a constant slope at the beginning of its lifetime, but depart with a constant slope as the aging progresses.

In a further embodiment of the invention, it is provided that the storage unit is configured to store aging-voltage characteristics for a plurality of LED modules, and wherein the apparatus further comprises a selection device for determining an aging-voltage characteristic to be used.

Different LED modules have different aging-voltage characteristics. According to the invention, an LED module stores different aging-voltage characteristics and is thus suitable for analyzing different LED modules. The selection device can be implemented in different ways. The selection can be done by a user, e.g. By a switch through which various aging-voltage characteristics to be used can be selected. In other embodiments, the selection device may be configured to automatically detect the aging voltage characteristic corresponding to the connected LED module.

According to the invention, it is provided that the selection device is designed to determine the aging-voltage characteristic to be used from the read-in forward voltage.

The determination of the aging voltage characteristic to be used from the read-in forward voltage can, for. Example, take place in that a certain range of forward voltage is assigned to a specific LED module and thus a specific aging voltage characteristic. This is particularly useful when different LED modules that can be evaluated with the same device, working in different areas of the forward voltage. In other embodiments of the invention, the detection of the voltage-age characteristic to be used may also be made by identifying the LED module by other characteristics of the forward voltage.

In a further embodiment of the invention, the apparatus further comprises an alarm unit configured to output an alarm signal when the aging information specifies an age greater than a predetermined maximum age and / or when the aging information Aging information specifies a residual life expectancy that is less than a predetermined minimum residual life expectancy.

The issuing of an alarm signal when a predetermined maximum age is exceeded or below a predetermined minimum residual life expectancy has the advantage that a user of the LED module can be forewarned about the occurring loss of the luminous power or about an imminent failure of the LED. module.

A first alarm signal may refer to a first early warning and a second alarm signal to an advanced aging, which may cause a failure of the LED module soon.

The device may be designed to control the LED module so that this the alarm signal in the form of a flashing, z. B. in the form of a flashing when switching on the LED module outputs.

In a further embodiment of the invention, it is provided that the voltage input is an analog input and the device further comprises voltage divider pre-circuit, wherein the voltage divider pre-circuit comprises a series circuit of a first resistor, a second resistor and a Zener diode, wherein the analog input is connected to the voltage divider pre-circuit, wherein the analog input is connected in particular via a resistor to the voltage divider pre-circuit.

The voltage divider pre-circuit has the advantage that the measuring range can be optimized, d. H. z. B. a high voltage of the LED module can be reduced to a lower voltage at the voltage input of the device.

In a further embodiment of the invention it is provided that the device further comprises a bus interface and / or a radio interface, which is adapted to output the aging information.

Thus, the information on the aging or remaining life expectancy of various LED modules in a building can be centrally recorded. This can easily give an overview of where and when which LED modules are expected to be replaced.

The radio interface can be a WLAN module that is designed to record a radio connection with a WLAN and with the Internet. The radio interface may also be a radio module which is designed to connect to a mobile radio network and thus to establish a connection to the Internet. Thus, it is possible that the device can communicate via the aging information via the Internet. For example, the aging information may be communicated to a maintenance company. The employees of the maintenance company then know that soon LED modules have to be replaced. Using BUS protocols for lighting technology (eg DALI, DMX, etc.), the occurrence of such faults can be interrogated and, if necessary, a group exchange can be initiated without the lighting system failing or not fulfilling its lighting task. Using appropriate maintenance tools (service box, ...), it would be possible for a technician to verify the status of the luminaire on site.

In a further embodiment of the invention it is provided that the device is a plug-in device which is adapted to be plugged onto an LED module and / or on an electronic ballast device.

Advantageously, the device can be simply clamped to the positive and negative terminal of the LED module. Thus, it is particularly easy to retrofit a way to determine aging information in existing LED modules and / or electronic ballasts. The plug-in device may have a temperature sensor which is arranged on the plug-in device so that it faces the LED module in the plugged state, that is, can determine the temperature of the LED module. The temperature sensor can be connected to a temperature input of the device.

In a further embodiment of the invention it is provided that the device further comprises a constant current source for supplying the LED module with a constant current, wherein the device is adapted to constant the luminous flux of the LED module by adjusting the constant current based on the aging information to keep.

This has the advantage that the LED module continues to deliver a constant luminous flux despite its inevitable aging. For example, the voltage-age characteristic can directly associate a luminous flux yield with a voltage that has been read. In another embodiment, the voltage-age characteristic of a read voltage assigns a life of the LED module and a second characteristic assigns the life of the LED module, a corresponding luminous flux efficiency. Typically, the luminous flux of the LED module decreases with increasing age.

In one embodiment of the invention it is provided that the device is designed to determine from the aging information a luminous flux yield of the LED module and to adjust the constant current based on the luminous flux yield, in particular based on a reciprocal of the luminous flux yield.

In one embodiment, the voltage-age characteristic may associate a particular read forward voltage with an age of 1000 light hours. A second characteristic curve can assign a luminous flux yield reduced to 80% to this age. Thus, by increasing the constant current by 25%, the device can keep the luminous flux constant. In other words, the device may be designed to adapt the constant current to the inverse of the remaining luminosity (as a proportion of the original luminosity). Thus, the luminous flux can be kept constant. Typically, an increase of the constant current takes place with increasing age of the LED module.

The aforementioned object is also achieved by an LED module comprising a plurality of LEDs and a device according to one of the above embodiments.

Integrating the device for determining the aging information on the LED module has the advantage that no separate device is required and the functionality for determining the aging information can be integrated directly in the LED module.

• – Einlesen einer Vorwärtsspannung des LED-Moduls, und
• – Bestimmen der Alterungs-Information basierend auf einer gespeicherten Spannungs-Alter-Kennlinie und der Vorwärtsspannung.

The above-mentioned object is also achieved according to the invention by a method for determining an aging information of an LED module, the method comprising:

• - Reading a forward voltage of the LED module, and
• Determining the aging information based on a stored voltage-age characteristic and the forward voltage.

According to one embodiment, it is provided that the method comprises a step of first waiting for a predetermined settling time after switching on the LED module before the further method steps are carried out. Thus, it can be prevented that voltage fluctuations attributable to a normal transient response after power-up are erroneously used to determine the aging information and thus lead to a falsified determination of the aging information.

Preferred embodiments of the invention are described below with reference to the accompanying figures. The figures show the following:

1 shows a schematic block diagram of a device according to the invention for determining an aging information of an LED module,

2 shows a schematic representation of a control circuit according to the invention for maintaining a constant luminous flux,

3 shows a circuit diagram of a voltage divider pre-circuit of a device according to the invention for determining an aging information of an LED module, and

4 shows voltage-age characteristics of different LED modules.

1 shows a device 100 that is a storage unit 110 , a voltage input 120 and an evaluation unit 130 having. Optional (in 1 not shown), the device further comprises a temperature input.

The storage unit 110 preferably comprises a non-volatile memory having a voltage-age characteristic of an LED module 200 stores.

The voltage input 120 is with the LED module 220 via a supply line 122 connected. In the supply line, a resistor and / or other components may be provided.

The evaluation unit 130 is configured to determine an aging information based on the voltage-age characteristic and the voltage read in at the voltage input.

2 shows a schematic representation of a control loop 200 , At the input of the control loop, a desired luminous flux φ _soll (t) is determined. This will be minus one of a subtraction unit 202 deducted correction value φ _aging (t) a controller 210 fed. The controller determines a current I (t), which is an LED module 220 is supplied. On the LED module 220 a voltage U _LED (t) is determined from that in a device 230 the correction value φ _aging (t) is determined. In addition, that of the LED module 220 actually generated luminous flux φ _is (t) to be determined. Preferably, the current I (t) is controlled such that the generated luminous flux φ _is kept constant (t).

3 shows a circuit of an arrangement 300 for determining aging information, wherein between an array of LEDs 320a . 320b . 322a . 322b an LED module and a voltage input of the device 100 a voltage divider pre-circuit 310 is arranged. In other embodiments, the voltage divider pre-circuit is part of the device 100 , The voltage divider pre-circuit 310 includes a first resistor 312 and a second resistor 314 that with a zener diode 316 are connected in series. Between the first resistance 312 and the second resistor 314 a voltage is tapped and via a feed resistor 318 the voltage input 120 the device 100 fed.

4 shows a diagram 400 with voltage-age characteristics 410 . 420 for two different LED modules. The vertical axis 402 refers to the forward voltage measured at the LED module, the horizontal axis 404 on the age (related to the operating time) of the LED module.

The first voltage-age characteristic 410 runs essentially constant rising, the forward voltage of the first LED module thus increases substantially continuously. The second voltage-age characteristic 420 , which refers to a second LED module, however, is decreasing and has a non-constant slope. These different voltage-age characteristics can be stored in a memory unit of a device according to the invention and thus the device can predict aging information for different LED modules.

LIST OF REFERENCE NUMBERS

100

contraption

110

Memory unit

120

Voltage input

122

supply

130

Evaluation unit

150

LED module

200

loop

202

subtraction

210

regulator

220

LED module

230

contraption

300

arrangement

310

Voltage divider prescreening

312

first resistance

314

second resistance

316

Zener diode

318

Feeding resistance

320a

Arrangement of LEDs

320b

Arrangement of LEDs

322a

Arrangement of LEDs

322b

Arrangement of LEDs

400

diagram

402

vertical axis

404

horizontal axis

410

first voltage-age characteristic

420

second voltage-age characteristic

Claims (11)

Contraption ( 100 ) for determining an aging information of an LED module, comprising: - a memory unit ( 110 ) for storing a voltage-age characteristic of the LED module, - a voltage input ( 120 ) for reading in a forward voltage of the LED module ( 150 ; 220 ), and - an evaluation unit ( 130 ) for determining the aging information based on the voltage-age characteristic ( 410 . 420 ) and the read forward voltage, the memory unit ( 110 ) is adapted to voltage-age characteristics for a plurality of LED modules ( 150 ; 220 and wherein the apparatus further comprises a selection device for determining a voltage-age characteristic to be used, wherein the selection device is configured to determine the voltage-age characteristic to be used based on the read forward voltage. Contraption ( 100 ) according to claim 1, further comprising a temperature input for reading in a temperature of the LED module, wherein the evaluation unit is adapted to determine the aging information based on the read temperature. Contraption ( 100 ) according to one of the preceding claims, further comprising a look-up table, which is adapted to the forward voltage of the LED module ( 150 ; 220 ) Aging information, in particular a life, a residual life expectancy and / or a probability of failure to assign. Contraption ( 100 ) according to one of the preceding claims, further comprising an alarm unit which issues an alarm signal if the aging information specifies an age which is greater than a predetermined maximum age and / or if the aging information has a remaining Life expectancy specified that is less than a predetermined minimum residual life expectancy. Contraption ( 100 ) according to one of the preceding claims, wherein the voltage input ( 120 ) is an analog input and the device ( 100 ) further comprises a voltage divider upstream circuit ( 310 ), wherein the voltage divider pre-circuit comprises a series connection of a first resistor ( 312 ), a second resistor ( 314 ) and a zener diode ( 316 ), wherein the analog input is connected to the voltage divider pre-circuit, wherein the analog input in particular via a resistor ( 138 ) is connected to the series circuit. Contraption ( 100 ) according to one of the preceding claims, wherein the device further comprises a bus interface and / or a radio interface, which is adapted to output the aging information. Contraption ( 100 ) according to one of the preceding claims, wherein the device is a plug-in device which is adapted to a LED module ( 150 ; 220 ) and / or to be plugged onto an electronic ballast device. Contraption ( 100 ) according to one of the preceding claims, further comprising a constant current source for supplying the LED module ( 150 ; 220 ) with a constant current, wherein the device is adapted to keep the luminous flux of the LED module constant by adjusting the constant current based on the aging information. Contraption ( 100 ) according to one of the preceding claims, wherein the device is adapted to determine from the aging information, a luminous flux yield of the LED module and to adjust the constant current based on the luminous flux yield, in particular based on a reciprocal of the luminous flux yield. LED module ( 150 ; 220 ), comprising a plurality of LEDs and a device according to one of the preceding claims. Method for determining an aging information of an LED module ( 150 ; 220 ), comprising: - reading in a forward voltage of the LED module ( 150 ; 220 ), and - determining the aging information based on a stored voltage-age characteristic and the forward voltage, wherein a memory unit ( 110 ) is adapted to voltage-age characteristics for a plurality of LED modules ( 150 ; 220 ), and the method further comprises: selecting a voltage-age characteristic to be used, the selecting comprising determining the voltage-age characteristic to be used based on the read-in forward voltage.

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