EP2412206B1 - Dimmable operating unit and lighting system for increasing the life expectancy of leds and oleds - Google Patents

Description

The present invention relates to an operating device for operating an LED or an OLED and to a lighting system with such an operating device.

For a correct control of an LED, a supply current, for example, supplied from the mains, must be adjusted so that it corresponds to the operating characteristics of the LED.

In this case, in most cases an AC / DC converter is necessary. Furthermore, the current or the voltage must be limited so that both correspond to the optimum operating point of the LED. This operating point is chosen so that a maximum of light is emitted. However, the operating point must still be within a permissible range.

It is known that the light output of an LED decreases during operation. With constant power supply, the intensity drops in the simplest case with time exponentially.

Depending on the manufacturer, the steepness of this waste is different and some manufacturers may also observe an overlapping of two different waste curves.

Qualitatively, however, it always comes down to exponential decay. Due to this, the waste is particularly strong, especially in a first phase of operation, for example in the first 20 to 200 hours.

This also has the disadvantage that in the case of lighting by LEDs in the long term, no time-constant brightness can be guaranteed.

The life expectancy of light emitting diodes - in particular light emitting diodes with organic components (OLEDs) - are today quite limited and must be ensured by expensive encapsulation and complex production processes. It would therefore be highly desirable to be able to increase the life expectancy of these components without resorting to even more expensive production or encapsulation techniques.

US 7138 970 B2 shows a method of operating an LED lighting system within a line scan camera, comprising an LED and a light sensor. The LED operates at pulse rate modulation at less than 100% duty cycle to reduce LED aging and increase life expectancy. The light sensor is set to a higher sensitivity. After the brightness of the LED decreases during operation, the duty cycle is gradually increased to 100%.

US 6236 331 B1 shows an electronic control device for an LED traffic light. The control circuit ensures a constant luminous intensity of the traffic light, which complies with the legal requirements and is below the maximum possible brightness of the LEDs. Constant brightness is achieved by a light sensor that measures the brightness of a separate LED. If necessary, the brightness is readjusted by the control unit. As a result, the life expectancy of the LEDs is increased and the traffic light can longer comply with the legal standard. In a particular embodiment, the lamp is set to maximum brightness and set to lower brightness during dusk and night. The Ambient brightness is detected via another light sensor.

Now there is the problem that while keeping the luminous intensity of an LED constant over its lifetime is desired, at the same time an active regulation of the luminous intensity should be enabled. This is especially important if the lighting should have a dimming function.

The invention addresses this problem and provides a solution to how the operating characteristics of LEDs become more consistent and adaptable.

This object is achieved by the features of the independent claims. The dependent claims further form the central idea of the invention in a particularly advantageous manner.

The invention thus proposes the use of a suitable control in a first operating phase of the LED or OLED.

For this purpose, a control gear is designed so that it can operate at least one LED or OLED. In this case, it has a control electronics for adapting a supply current to the operating characteristics of the at least one LED. The operating device restricts the maximum power of the at least one LED or OLED in a first operating phase to a predetermined level. The operating device ignores an incoming external dimming command or converts it, for example, by scaling down so that the LED or OLED power does not exceed the predetermined level in the first phase of operation.

For OLEDs, it can be beneficial if they use a given current during the first few hours of operation For example, incoming dimming commands are ignored during this time and the OLED is operated with a predetermined current or a current in a predetermined current corridor. Within the corridor, incoming dimming commands can optionally be implemented.

The predetermined level is below the maximum allowable power supply of the at least one LED. This ensures that the maximum possible light intensity of the LED is deliberately prevented during a first operation.

The invention further provides that the predetermined level changes over the operating time in the first operating phase of the at least one LED in such a way that it approaches the maximum permissible power supply.

The first phase of operation is terminated when the predetermined level has reached the maximum allowable power supply.

The predetermined level changes over the operating time of the first operating phase of the at least one LED so that the light intensity of the at least one LED remains constant.

The predetermined level may linearly increase over the operating time in one embodiment.

The predetermined level may increase logarithmically in a further embodiment over the operating time.

Alternatively, the predetermined level may increase over the operating time but also following any other non-linear curve.

The invention relates to an operating hours counter, by means of which the change of the predetermined level is regulated as a function of the operating time.

The invention also relates to a memory, such as a One Time Programmable Memory, which specifies the temporal change of the predetermined level.

In addition, the invention may comprise a measuring device, preferably a light sensor, which detects the light intensity of the at least one LED when operating at the power of the predetermined level and supplies the measured values to the control unit.

The control unit can thereby adjust the predetermined level by means of supplied measured values so that the light intensity of the at least one LED remains constant during operation with the power of the predetermined level.

An external dimming command of the light intensity can be made via an interface.

The invention further provides that in the case of a dimming command coming from the outside, the light intensity of the dimming value actually set on the at least one LED takes place as a function of the predetermined level.

This means that the actual dimming of the at least one LED is scaled down according to the current value of the predetermined level.

It is conceivable here that an incoming dimming command from outside can take place by means of a user input.

It is also possible that an incoming dimming command from outside can be done by adaptive adaptation to external conditions, such as daylight.

In addition, an incoming dimming command from outside can be done by means of an input from another system, for example an external sensor device or a central circuit.

The adjustment of the brightness of the at least one LED can be done via a power control with a limited value, for example via a pulse width modulation.

Alternatively, an adjustment of the brightness of the at least one LED via a current control is conceivable.

It is further provided that at least one OLED or a combination of LEDs and OLEDs can be operated instead of the at least one LED.

Finally, the invention provides a system comprising a central control unit, a bus and at least two operating devices connected to the bus for operating in each case at least one LED. Each operating device includes a control electronics for Adaptation of a bus supply current to the operating characteristics of the at least one LED. The maximum power of each LED is limited in a first phase of operation to a predetermined level below the maximum allowable power supply.

The invention further relates to an operating device for operating at least one LED or OLED having an interface for supplying external dimming commands from a central control unit or a sensor and a control electronics for controlling or regulating a supply current to the operating characteristics of the at least one LED or OLED depending on incoming dimming commands, wherein the operating device controls the supplied power or the supplied current of the at least one LED in a first phase of operation to a predetermined level or sets, and the operating device ignores an external dimming command or so implemented, in particular downscaled that the LED - or OLED power does not exceed the predetermined level in the first phase of operation or falls below.

In addition, an incoming dimming command is implemented in a suitable manner.

The predetermined level approaches within the first phase of operation the value of the maximum allowable power supply.

The central control unit also has an interface, via which an incoming dimming command from the outside of the light intensity can take place.

An incoming dimming command can be ignored by the corresponding operating device during the first phase of operation of an LED.

Alternatively, however, an incoming dimming command can be rescaled so that the actual dimming of each LED takes place as a function of the predetermined level.

Fig. 1

zeigt qualitativ den zeitlichen Verlauf des Intensitätsabfalls bei konventionellem und bei erfindungsgemäßem Betrieb einer LED,

Fig. 2

zeigt schematisch ein Ausführungsbeispiel eines erfindungsgemäßen Betriebsgeräts,

Fig. 3

zeigt ein beispielhaftes Verfahren, wie ein Dimmbefehl in Abhängigkeit des vorbestimmten Pegels skaliert werden kann, und

Fig. 4

zeigt schematisch ein Ausführungsbeispiel eines erfindungsgemäßen Systems mit zwei Betriebsgeräten.

Further features, advantages and features of the present invention will now be described with reference to the figures of the accompanying drawings and the detailed explanation of an embodiment.

Fig. 1

shows qualitatively the time course of the intensity decrease in conventional and inventive operation of an LED,

Fig. 2

shows schematically an embodiment of a control gear according to the invention,

Fig. 3

shows an exemplary method of how a dimming command can be scaled depending on the predetermined level, and

Fig. 4

schematically shows an embodiment of a system according to the invention with two operating devices.

Fig.1 shows qualitatively the time course of the intensity decrease with LEDs. Here is the Light intensity vertical and time horizontal, both with arbitrary units, drawn.

Row 1 represents the drop in intensity of an LED, which is constantly operated with the normal operating parameters for them. It can be clearly seen that the intensity initially drops very sharply and in the further course of the waste stagnates more and more. This roughly corresponds to an exponential curve.

Row 2, on the other hand, represents the drop in intensity of an LED during operation according to the invention. It can be seen that the LED in the first phase of operation, i. is operated in the starting phase of operation with a power that is below the maximum allowable power. The maximum permissible power should correspond to the normal operating parameters of the LED. The duration of this first phase of operation depends on the design and geometry of the components used (LED / OLED) and typically takes between 20 and 200 hours. In the simplest case, a suitable drive could be such that the light intensity of the OLED is e.g. to 80% of the initially possible maximum light intensity keeps constant.

Since due to the natural aging, the light intensity decreases continuously, must be readjusted continuously. Thus, a constant light intensity can be achieved.

The end of the first phase of operation is reached when the LED is operated at the maximum allowable power. In Fig. 1 So the end of the start phase is reached at about 12 o'clock.

Following the first phase of operation, the drive parameters are kept constant, as is normal Operation would be common. As a result, the light intensity will slowly drop.

However, it can be seen that the intensity itself now drops more slowly than if the light emitting diode (LED / OLED) had been driven normally during the first phase of operation.

In Fig. 2 a schematic embodiment of the operating device 1 for operating at least one LED and / or OLED 9 is shown.

The operating device consists essentially of a control electronics 2 and a control unit 3. Control electronics 2 and control unit 3 communicate via an interface 7. Optionally, the operating device may have a memory 4 and / or an operating hours counter 11.

The control electronics 2 adjusts the supply current 5 so that it has suitable operating parameters for the power supply 6 of at least one LED and / or at least one OLED 9. The control electronics can for this purpose comprise an AC-DC converter, and an electronic circuit for current and voltage adjustment or limitation.

The control unit 3, however, is responsible for an intelligent control of the control electronics. The control unit 3 controls the drive unit according to the principle of the invention, as in the description Fig.1 has been explained. In addition, it is responsible for other, for example, user-initiated inputs and the corresponding control of the control electronics. It is also possible that they are the control electronics regulates adaptively. The control unit thus generally represents an intelligent controller which can perform mathematical calculations or represents electronic data processing.

It should be emphasized here that this arrangement is to be regarded as purely logical-functional. It does not represent a hardware-technical arrangement. This means that the hardware-implemented arrangement can deviate from this. For example, it is conceivable that the control unit is implemented as an integrated circuit. However, it is possible that a part of the drive electronics is implemented in the same integrated circuit. It is also possible that the memory and / or the operating hours counter are also located in the same integrated circuit or on the same substrate.

In one embodiment, the control unit has an operating hours counter 11. This is used to count the operating hours and thus to increase the power supplied to the at least one LED successively during operation. In the simplest case, a linear increase in power would be conceivable. However, the increase is preferably logarithmic in order to optimally compensate for the light intensity of the at least one LED dropping exponentially with the operating time. Alternatively, the time history of the power can follow any other nonlinear curve.

Also, the time course can not only consist of a continuous curve, but also have individual discrete values.

In another embodiment, no measurement takes place, even no operating hour count. Instead, a memory 4 has a time-predetermined course of the predetermined level. For this purpose, it may be provided that a starting value below 100% current value is selected for the time profile (for example 80%), which is increased according to a predetermined curve over a defined period of time to 100% current value. This increase may be linear or preferably also logarithmic or exponential, as described above, so as to compensate for an exponential decrease in intensity.

An implementation is conceivable by means of so-called OTPs (One Time Programmable Memory). The programmed curve is traversed to 100% current value in the first operating phase. Thereafter, the at least one LED is operated at 100% current value when switched on again.

This information of the time course can be supplied to the control unit 3, which in turn controls the LED operation by means of the control electronics.

In a third embodiment, the compensation of the drop in intensity of the at least one LED by a measuring device 12 takes place. This is connected by means of an interface 8 to the control unit. It should be noted, however, that the measuring device can be integrated both externally and in the control unit, for example, can be located on the same substrate or in the same integrated circuit.

The measuring device is preferably a light sensor.

This detects the intensity of the light emitted by the at least one LED. This value is transmitted to the control unit. This can calculate the discrepancy between the actual value of the light intensity and the target value. The target value used for this purpose is the light intensity that was set at the beginning of the first operating phase. The control unit now controls the activation of the at least one LED in such a way that the discrepancy between the actual value and the nominal value is compensated. In this way, the at least one LED always shines bright in the first phase of operation.

Now, it is further provided that the brightness of the at least one LED is also adjustable from the outside. This means that outside forced dimming is possible.

This can be done as user input as a dimming command. It is also conceivable that this takes place adaptively. In the latter case, the illumination can be adapted by the at least one LED to the ambient light. For this purpose, it makes sense to use a further sensor, for example a daylight sensor, which measures the ambient light.

In addition, it is conceivable that a dimming command is initiated by another system, for example a central control. In particular, it is possible that the operating device is connected via an interface 12 to a bus. The resulting advantageous features become apparent in the description Figure 4 explained in more detail.

It is now necessary for the control unit to calculate the activation parameters of the at least one LED as a function of the incoming dimming command and the discrepancy between the actual and desired values or the time profile of the predetermined level.

Fig. 3 represents an exemplary method of how the calculation can be done. This example assumes that the level is adjusted using a light sensor.

When the LED is first turned on in step S101, initial initialization is initiated. In this, in S102, the light of the LED is set at the predetermined level, for example, 80% of the maximum allowable power. Then the light intensity I _{IST, MAX is} measured. In S103, this value is assigned to the variables I _{SOLL, MAX} . This value serves as a reference for the further adaptation of the predetermined level in the course of the first operating phase. Of course, this Erstinitialisierung from S101 to S103 takes place only once when the first start of the LED.

In S104, the actual light intensity I _{IST is} measured again. This is compared with the setpoint in S105. If a discrepancy occurs between the two, the predetermined level is adjusted so that the actual and setpoint are the same.

As already mentioned, it is conceivable to adapt the predetermined level to an operating hours counter and / or to use a memory.

In this case, the initialization from S101 to S103 becomes unnecessary.

The adjustment of the predetermined level in S104 and S105 can be done directly in this case. This means that no measurement of the light intensity and no calculation of the level to be used is necessary. Instead, the level can be successively increased directly following a predetermined curve during operation.

In S106, an external dimming command D is measured, which has been set on a user interface, for example. Then, the actual light intensity I _{IST is} calculated depending on the preset level P and the dimming value D.

In the simplest case, this is a multiplication of the two values, as shown by formula (1). $$I_{\mathit{IS}}=P\times D$$

For example, if the currently valid level would be 90% of the maximum permissible power and dimming level of 50%, the light intensity would I _IS 45%. It should be noted that the preset level changes over the operating time also in a linear or non-linear manner. There is also the possibility that the actual light intensity I _{IST to} be set is calculated from a nonlinear formula. This means that the actual light intensity to be set is I _IST scaled down in a non-linear manner.

In a further embodiment, however, the determination of the actual light intensity I _{IST to be set} could also take place via a table (look-up table). This can be stored, for example, in the memory 4. In this case, the table can assign to each combination of a dimming value and a preset level an actual light intensity I _IST to be set.

However, any other form of calculation is possible. All that matters is that, on the one hand, the aging of the LED is compensated and, on the other hand, the actual light intensity, in particular its properties which have a subjective effect on the observer, correspond to the set value. Compensation of the set dimming value must therefore always take place dynamically in the first operating phase, that is to say according to the currently valid preset level.

The intensity value determined in S107 is converted by the control unit into corresponding operating parameters for the LED. These are supplied to the control electronics so that the LED lights up in the desired manner. For this purpose, for example, a pulse width modulation or a current control can be used.

In S108, it is determined whether the LED is still in the first operating phase. This can preferably be determined via the current level. If this is lower than the maximum permissible power, then the LED is still in the first operating phase.

When using an hour meter, a predetermined operating time can also be defined as the first operating phase.

In the event that a given curve is traversed, it can be defined that the first operating phase is over when the curve is completely traversed.

If the first phase of operation is not yet over, it returns to S104. Optionally, a time t may be waited before re-adjusting the level in S104.

If the first operating phase is already over, the level is no longer changed. In this case, jump directly to S106. Optionally, a time t can be waited again.

It may also be added that there are two different possibilities for adjusting the predetermined level in S104 and S105.

In a first embodiment, the light intensity is momentarily raised to the predetermined level, i. the maximum permitted by the operating device light intensity, set and so performed a comparison between the actual and setpoint. As the setpoint, the one set in S103 is used.

In a second embodiment, the light intensity set by the dimming is maintained. The dimming value is calculated into the measured light intensity in such a way that the actual value can be determined by calculation when the LED is operated at the predetermined level.

In this way, again, a comparison with the target value set in S103 can be performed.

Since the first execution may possibly lead to a kind of flashing, execution 2 is to be preferred, as long as an error-free compensation of the dimming value is possible. Therefore, it is also conceivable to use this procedure in S102 and S103 to determine I _{SOLL, MAX} .

In Figure 4 the features according to the invention are advantageously applied to a system.

The system 16 consists of a central bus unit 17 and three operating devices 15, wherein only the first operating device is shown in detail.

The central bus unit is connected to an electrical power supply 10. Furthermore, it has an interface 8 via which a dimming command can be received. This can be done by a user input. An input device, for example a rotary knob, can be present for this purpose on the central bus unit or externally. A display device, such as a display is conceivable, for example, to display the preset level per LED / LED module or the set dimming value. In addition, this can be done by a measuring device 12. It may be a light sensor and / or a motion sensor. It is also conceivable that such a sensor as a device 13 on the central bus unit located. In addition, the dimming command can be carried out by an external system.

For communication with the operating devices or for their power supply, there is a bus 14, which connects the central bus unit and operating devices. However, it is conceivable that the communication bus (or address bus) and the power supply bus are two different devices. For example, the communication can take place via a radio interface and the power supply via a cable.

Each operating device has its own "intelligence" in the form of a central control unit 3 and optionally a memory 4 and / or an operating hours counter 11. In addition, it comprises a control electronics 2 and a connection 6 for connecting at least one LED 9. Instead of the at least one LED, any combination of LEDs and OLEDs can be used again. Also conceivable is the connection of an LED module or an LED chain, consisting of any combination of LEDs and OLEDs.

Again, each LED or LED module is operated in a first phase of operation at a predetermined level which is below the maximum allowable power supply. This is increased in the manner described above during the first phase of operation. In this case, the regulation of the predetermined level is performed by each operating device for the connected thereto LED or the LED module individually. This is particularly advantageous when a single LED or a single LED module is replaced once and thus this is at the beginning of the first phase of operation.

This would also be feasible by the central bus unit for each operating device (or for the connected LEDs) would calculate a predetermined level. The level could then be assigned to the operating device by means of a unique address.

A dimming command entering into the central bus unit, or a dimming command set by the central bus unit, can be forwarded to each operating device. This is then preferably processed locally in each operating device. In this case, an adaptation of the light intensity to the dimming command is again carried out as a function of the predetermined level.

In another embodiment, dimming commands are ignored by any control gear whose LEDs are still in the first phase of operation. In this way, the LEDs in the first phase of operation always light up brightly.

LIST OF REFERENCE NUMBERS

1

control gear

2

control electronics

3

control unit

4

Storage

5

Power supply from the mains

6

Power supply of the LED

7

Interface between control electronics and operating device

8th

Interface for setting the operating mode

9

LED or OLED

10

AC power

11

Hour meter

12

measurement device

13

sensors

14

bus

15

control gear

16

system

17

Central bus unit

Claims (19)

1. Operating device for operating at least one LED (9) or OLED, comprising:

   - an interface for supplying external dimming commands from a central control unit or a sensor

   - control electronics (2) to control or regulate a supply current to the operating characteristics of the at least one LED or OLED as a function of incoming dimming commands,

   characterized in that

   - in a first operating phase, the operating device is limited to a predetermined level below the maximum permissible power supply of the at least one LED or OLED, wherein the first operating phase is triggered with the first activation of the LED,

   - the operating device ignores or downscales an external dimming command in the first operating phase so that the maximum power of the at least one LED does not exceed the predetermined level in the first operating phase,

   - the operating device detects the end of the first operating phase and the level of the maximum power supply no longer changes when the end of the first operating phase is determined.
2. Operating device (1) according to claim 1,
   characterized in that
   the operating device regulates or determines the supplied power or the supplied current of the at least one LED in the first operating phase.
3. Operating device according to claim 1 or 2,
   characterized in that
   the predetermined level changes over the operating time in the first operating phase of the at least one LED or OLED in such a way that it approaches the maximum permissible power supply.
4. Operating device according to one of the preceding claims,
   characterized in that
   the first operating phase is then ended when the predetermined level has reached the maximum permissible power supply.
5. Operating device according to one of the preceding claims,
   characterized in that
   the predetermined level so changes over the operating time of the first operating phase of the at least one LED that the light intensity of the at least one LED remains constant.
6. Operating device according to one of the preceding claims,
   characterized in that

   - the predetermined level increases linearly over the operating time, or

   - the predetermined level increases logarithmically over the operating time, or

   - the predetermined level increases non-linearly over the operating time.
7. Operating device according to one of the preceding claims,
   characterized in that
   the operating device comprises an operating hour counter (11) by means of which the change of the predetermined level is regulated as a function of the operating time.
8. Operating device according to one of the preceding claims,
   characterized in that
   the operating device has a memory (4), for example a one-time programmable memory, which gives the temporal change of the predetermined level.
9. Operating device according to one of the preceding claims,
   characterized in that
   the operating device comprises a measuring device (12), preferably a light sensor, wherein the measuring device determines the light intensity of the at least one LED during operation at the power of the predetermined level and supplies the measured values to the control unit.
10. Operating device according to one of the preceding claims,
    characterized in that
    the control unit (3) so adapts the predetermined level by means of the measured values supplied, that the light intensity of the at least one LED remains constant during operation with the power at the predetermined level.
11. Operating device according to one of the preceding claims,
    characterized in that
    the operating device has an interface (8) via which an incoming dimming command of the light intensity may be received.
12. Operating device according to one of the preceding claims,
    characterized in that
    in the case of a dimming command from the outside, the light intensity of the dimming value actually set at the at least one LED as a function of the predetermined level.
13. Operating device according to one of the preceding claims,
    characterized in that
    in the case of a dimming command coming from the outside, the actual value set at the at least one LED is down-scaled according to the current value of the predetermined level.
14. Operating device according to one of the preceding claims,
    characterized in that

    - a dimming command coming from the outside is ignored during the first operating phase, and/or

    - a dimming command coming from the outside may be made by means of adaptation to external conditions, for example daylight, and/or

    - a dimming command coming from the outside may be made by means of an input from another system, for example an external sensor device or a central circuit.
15. Operating device according to one of the preceding claims,
    characterized in that
    the brightness of the at least one LED is adjusted via power control with a limited value, preferably via pulse-width modulation.
16. Operating device according to one of the preceding claims,
    characterized in that
    the brightness of the at least one LED is adjusted via a current control.
17. Operating device according to one of the preceding claims,
    characterized in that
    at least one OLED or a combination of LEDs and OLEDs may also be operated in place of the at least one LED (9).
18. System (16), comprising a central control unit (13), a bus (14), and at least one operating device (15) according to one of the preceding claims connected to the bus by means of an interface.
19. Method for the optimized operation of at least one LED by means of an operating device according to one of the claims 1 to 17 with the following method steps:

    - supplying an external dimming command coming from a central control unit or a sensor by means of an interface of the operating device;

    - controlling or regulating a supply current to the operating characteristics of the at least one LED as a function of the incoming dimming command by means of the control electronics of the operating device,

    characterized in that

    - the maximum power of the at least one LED in a first operating phase is limited to a predetermined level under the maximum permissible power supply of the at least one LED by means of the operating device, wherein the predetermined level approaches the value of the maximum permissible power supply within a first operating phase, wherein the first operating phase is triggered with the first switching on of the LED, and, wherein in the first operating phase, an external dimming command is ignored or downscaled so that the at least one LED does not exceed the predetermined level in the first operating phase,

    - the operating device determines the end of the first operating phase of the LED, and

    - when the end of the first operating phase is determined, the level of the maximum power is no longer changed.

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