Lighting device with a LED-module

0001The invention relates to a lighting arrangement with an LED module according to the preamble of patent claim 1, particularly in the form of a signal generator or a signal Traffic lights.

0002Signaling device for signaling or traffic light systems are in increasingly equipped with LED light sources. An LED light source differs from a conventional Light source such as an incandescent lamp, substantially in following points:<ul><li>The efficiency of LEDs decreases with increasing temperature from. In contrast, increases in conventional Light sources such as incandescent efficiency. Therefore, in LED light sources have a certain reserve of light output provide to the brightness requirements for a specified temperature range and in particular at to meet an increase in temperature.</li><li>The efficiency of the LEDs decreases during the LED lifetime due to aging slowly. This efficiency loss is in conventional LED light sources by a Oversizing, so also a reserve of Compensated light output at the beginning of life.</li><li>An LED light source consists of a plurality of individual Light points. This large number of light points arise new forms of fault conditions (failure images). Thus, compared to conventional light sources with a LED light source, for example, half of the LEDs have failed, while the other half yet is intact and remains lit. In a conventional Light source with a light bulb means a failure however, generally a total failure.</li></ul>

0003Thus, with conventional light sources with incandescent lamps of two states, the proper operation and the Total failure be considered, the latter can be comparatively reliably detected since then no Current stops flowing through the bulb. With LED light sources however, exist in addition to the proper operation and the Total failure, a plurality of intermediate states in which on the one hand only a part of the LEDs is defect, or alternatively the light output significantly due to aging although dropped, but the LED light source still is functional. It is only with some - if also large - likely a direct relationship between current flow and light output.

0004In many applications, especially in traffic lights and Signaling systems, it is necessary that the LED light sources predetermined minimum requirements with respect to their optical meet output variables. Due to the described aging But as well as the numerous error-intermediate states can in Contrast can not be considered to be an incandescent lamp which, that this checked at the beginning of the operation Minimum requirements are complied with, as long as the LED light source has not failed completely.

0005Although it is basically at traffic lights or signals due said different failure mechanisms desirable that different in LED light sources error Degree or various severities (for Example "20% light loss", "40% light loss," etc.) be detected differentiated. This requires, however correspondingly more complex interfaces between the other Components of the traffic light or signal conditioning. The can in existing installations costly retrofitting of the entire System require. Would be more advantageous, an LED light source here, the extent possible with a light bulb is compatible.

0006Furthermore, as already mentioned, due to the aging at conventional LED light sources at the beginning of the operation of a comparatively high light intensity provided, the particular is well above the required minimum intensity to despite the aging as long as possible the required meet minimum values. With LED light sources according to the state art is this high initial light intensity, typically in the order of 100% over the Minimum requirements achieved by a either corresponding plurality of LEDs used or LEDs relatively high currents are operated. The former alternative is associated with increased costs, the latter may in turn to a accelerated aging or a shorter lead life. In addition, such LED light sources the road users at the beginning of the operation appear uncomfortably bright.

0007Overall, should a switch with an LED light source, For example, a traffic light or signal conditioning, preferably have the following properties:<ul><li>The required minimum brightness and Luminance distributions, for example, in accordance with EN 12368, are met over the entire period of use.</li><li>The required minimum brightness, for example according to EN 12368, be only slightly, preferably by about 20%, exceeded so that the signal transmitter is not too bright.</li><li>The lifespan of an auto switch should be as large as possible and focus particularly not by an adverse operating far further than the minimum requirements be affected. </li><li>The siren has a dimming device that the For example, the light intensity is reduced by half. This is and by some countries or municipalities for traffic light Signaling systems required.</li><li>The signal transmitter is switched off as soon as the minimum requirements, For example, with respect to brightness, luminous intensity distribution or luminance, are below.</li><li>The signal generator has a simple structure as possible, especially without complex interfaces. Preferably is the signal generator with conventional control circuits compatible.</li><li>The siren has a low energy consumption.</li></ul>

0008In conventional LED light sources is to ensure these requirements, among other things, the current flow through the individual LED chains monitored. If one or several Chains interrupted in case of error, then an Disconnection of the LED light source. some Embodiments of this elaborate and complex electronic circuits used.

0009Partly with conventional LED light sources will also depend is considered that due to the large number of LEDs a failure individual points of light with little or no to Below the minimum brightness results. Here are consciously taken requirement violations in buying if the possible error no serious damage to appear to cause.

0010It is an object of the present invention, an improved to provide lighting arrangement with an LED light source, the particular for use as a signal transmitter of a light or is signal conditioning suitable.

0011In the invention, a lighting arrangement having a LED module and a power supply for the electrical supply of LED module provided, one of an optical produces output of the LED module dependent measurement signal is, the measurement signal is fed into the power supply, and the power supply, the electrical supply of the LED module by means of the measuring signal controls so that, in operation, the LED module a predetermined target output complies. Ebenson may be provided within the scope of the invention that the Power supply, the electrical supply to the LED module in Dependence of the measurement signal interrupts to, for example, to avoid operating outside the standard specifications.

0012As the optical output can be used to Beispeil brightness be used. Here, the LED module generated as Measuring signal is preferably a signal when a particular predetermined brightness level is reached. Optionally several brightness levels with different signals be specified. The power supply, which the LED module with power supplies, evaluates this measurement signal and thus provides the Operating current for the LED module so that the desired Brightness level just reached and the brightness of the LED module is kept constant.

0013The invention is particularly suited to a signal transmitter Traffic light or signal system and has the following advantages:<ul><li>The LED module complies with the required minimum brightness, expediently being the brightness level of the LED module is selected according to the minimum brightness.</li><li>The LED module is only slightly, about 20% lighter, as prescribed and in particular not appear uncomfortable light. This standard setting can observe very closely.</li><li>The LED module is operated just with the power is required to comply with the standard specifications. This resulting in a low energy consumption and a high Lifespan.</li></ul>

0014Overall, the feedback of the optical Output, for example, the brightness of the LED module, both the aging effect and the thermal offset behavior of the LEDs. At the same time the Energy consumption is minimized and maximized the lifespan.

0015Default way in the invention as optical Output or optical target output size the Brightness, the total optical output power, the Luminous intensity distribution, the luminance or a function these quantities used.

0016This enables in particular the compliance with standard specifications for traffic signal control, which is also on the Luminous intensity distribution and luminance distribution can extend.

0017It is between a two-dimensional LED light source and a to distinguish dot-shaped LED light source. At a -scale LED light source, the LEDs over the entire Light-emitting surface distributed, each LED or each LED group is assigned a separate condenser. At a point-shaped LED light source, however, the LEDs, preferably tightly packed in the center of a common Condenser arranged. The condenser thus places optical element, for example a lens, for imaging the Light generated from the LEDs, for example in the direction of the Road users at a traffic light or signal conditioning, represent.

0018Such array LED light source thereby has the Property that already each LED or LED group associated with the condenser, optionally substituted with downstream diffusion plate, the prescribed having light intensity distribution. Therefore, with this LED light source to ensure the light distribution no monitoring of the function of the LEDs required.

0019are In a point-like LED light source on the other hand LEDs or various areas of the LED module assigned different transmission directions, so that a Function control of the respective LEDs is necessary.

0020For the luminance distribution is such Distinction also appropriate. Here, however, is at the surface light source, a functional check of the LEDs necessary because each LED or LED group a certain covering the area of ​​the light exit surface of the signal generator. When the point light source illuminates the other hand, each LED almost the entire light exit area, which any inhomogeneities due to failed LEDs hardly occur and therefore does not check the function of the LEDs must become.

0021A functional check of LEDs must therefore at a point-like LED light source to ensure the Luminous intensity distribution in a two-dimensional LED light source carried out to ensure the luminance distribution will.

0022This function controls the LEDs is preferably optically performed using the generated light. Also one Function control using the electrical LED parameters, Example of the operating current of each LED or LED groups is possible, however, and due to the above described aging and associated therewith Reduction in the efficiency an additional optical Function check is advisable.

0023is In a preferred embodiment of the invention provided that a control module (controller), the optical Desired output size dictates. Such a control module is used to control the power supply and determine the general health of the lighting arrangement, approximately, whether the lighting arrangement is on or off or is operated in dimmed Zutand. The power supply is for the electrical supply of the LED module between Control module and LED module connected. Preferably at the invention, the Beleuchtungsanordung carried out so that conventional drive circuits, in particular for Incandescent lamps are provided can be used. This requires that no additional, for LED modules specific interfaces are needed.

0024Furthermore, it is advantageous to design the power supply so, that the power supply in case of failure, the supply of the LED module interrupts that no more current from the power supply flows. For the control module corresponding to a failure a conventional light bulb: when current flows, is the Bulb functional, whereas if no current flows, is defective bulb. On the part of the control module can This can be detected without additional control lines between the control module and power supply would be needed. This resulting in an advantageous cost savings. In the Invention is sufficient, for example, a conventional Two-wire cable as connection between control module and PSU.

0025In a preferred embodiment of the invention includes the Power supply has a comparison device for comparison of the optical output of the optical target output size, wherein at a predetermined deviation of the optical Output from the optical target output size the Power supply, the electrical supply to the LED module interrupts. This ensures that the LED module is switched off defined once any standard specifications are no longer met. Advantageously, this Shutdown immediately recognizable from the outside, so that a prolonged operation, for example, with inadequate Brightness, is avoided.

0026The LED module can also be an error signal to the power supply give, as soon as the corresponding optical output prescribed minimum requirements below, so that PSU then the electrical supply of the LED module interrupts.

0027The power supply interruption occurs preferably by the defined and irreversible destruction of a component, for example, a fuse. These Embodiment, it is both cost without large Expense repaired again. It is particularly preferred while the current flow is interrupted by the power supply so that then the adapter receives no power. As already As described, this interruption of a upstream control module can be easily detected. Thus In particular conventional drive circuits in the Invention can be used without additional control lines required between the control module and the power supply would.

0028Between the power supply and the LED module are in Invention, no complicated interfaces necessary. To the Example, with only two additional lines between LED light source and power supply feedback to the Brightness level occur, then the current supply to the LED module is evaluated.

0029If the part of the LED module is an error, the for Violation of standard specifications leads, can more extensively the Measurement signal produced by optical outputs transmitted via the supply lines to the power supply will. It could, for example, an "artificial short-circuit" the LED light source are generated, which in turn from the power supply is detected and then as a means of overcurrent protection as a fuse for interrupting the supply and disconnection of the power supply leads. In this case, as Measurement signal, the total power consumption or the to understand the total resistance of the LED module.

0030Overall, by the interaction of the LED module and PSU, which is based in particular that the LED module a measurement signal, optionally in several stages, is generated, and the power supply of this measurement signal and evaluates accordingly responds, an efficient and safe operation of Beleuchtungsanordung guaranteed. It can For example, for normal operation, the dimmed operation, in case of error or exceeding the service life, So if despite increased operating current due to Aging phenomena not the optical output of the LEDs insufficient, different measurement signals are generated.

0031Other features, benefits and advantages of the invention are below with reference to embodiments in explained in connection with Figures 1 to 7th

0032Show it<sl><li>Figure 1 shows a block diagram of a first embodiment an illumination arrangement according to the invention,</li><li>2 is a block diagram of a second Embodiment of an inventive Lighting arrangement,</li><li>Figure 3 shows the dependence of the optical output power of the time in a third embodiment of a Lighting arrangement according to the invention,</li><li>Figure 4 shows the dependence of the optical output power of the time at illumination arrangement according to the prior Technology, </li><li>Figure 5a and 5b is a partial circuit diagram of a fourth Embodiment of an inventive Lighting arrangement and a waveform for different operating states,</li><li>Figure 6 is a circuit diagram of a fifth embodiment an illumination arrangement according to the invention and</li><li>Figure 7 is a circuit diagram of a sixth embodiment an illumination arrangement according to the invention.</li></sl>

0033Identical or functionally identical elements in the figures the same reference numerals.

0034The shown in Figure 1 in block diagram Lighting arrangement, preferably a traffic light system comprises, an LED module 1 with a plurality of LEDs, a power supply 2 and a control module. 3

0035The control module 3 is thereby the target operational state of 4 LED module before, for example, a normal operation oden a dimmed operation. Preferably, this requirement is based on the the output voltage of the control module 3 to the power supply 2 transfer.

0036The power supply unit evaluates this input via the operating state from, for example, by the magnitude of the input voltage. Furthermore, the power supply 2 to the electrical supply 5 is used the LED module 1, which is in accordance with this provision 5 the target operational state ceases.

0037The LED module 1 generated from an optical Output, for example, the brightness, a measurement signal 6, which is transmitted to the power supply. 2 Thus, particularly a decrease in the optical output as about the brightness and / or a failure of LEDs on the PSU 2 are signaled.

0038The power supply unit 2 controls the electric power supply 5 according to the measurement signal by 6, so that a predetermined optical target output size, such as a minimum brightness, is complied with. The optical target output size preferably determined by the control module by the Example for the respective operating state, a corresponding optical desired output size is defined.

0039If an operation in accordance with the predetermined optical Desired output size is no longer possible because For example, too many LEDs are defective, or no longer makes sense, because as the electric supply to 5 Compensation of aging-related performance degradation on to would rise high values, interrupts the power supply 2, electrical supply 5 of the LED module 2. This will make the LED module defines off. This is directly from externally visible so that a prolonged operating outside the standard specifications, the at a traffic light traffic could jeopardize, is avoided.

0040Furthermore, such a shutdown 7 to the control module passed. This can, for example, realized by be that a fuse blows and so the PSU is a total shut down. Concerning the Control module, this shutdown 7 characterized recognized be that the power supply receives no power. This corresponds to the failure of a bulb, so that conventional Control modules can be used for incandescent lamps. Proceeding, the control module failure otherwise signal, at a traffic light, for example by flashing with an intact LED module yellow emission color.

0041This lighting apparatus has the following advantages: <ul><li>Compliance with the standard specifications is with high security guaranteed. There are no stages error messages like about "20% failure", "40% failure" necessary.</li><li>detects the power supply 2, whether the predetermined Requirements are met, otherwise an Shutdown by the power supply 2 and the Power supply. 2</li><li>The light source does not appear not uncomfortably bright because Minimum requirements during the entire operating period are barely exceeded.</li><li>The power supply unit 2, regardless of the color used and uses the LED brightness class used will.</li><li>The lifetime is over conventional devices elevated.</li><li>The energy consumption is over conventional devices reduced.</li></ul>

0042Figure 2 shows a block diagram of another Embodiment of the invention.

0043The LED module 1 comprises a LED-array 1a with a plurality parallel-connected LED strings (LED series circuits), to the operating current by means of a suitable electronic Circuit 22 is divided equally. Such Circuit will be explained in connection with Figure 6 in more detail.

0044An optical monitoring of all LEDs would comparatively consuming. Therefore, from a reference LED chain preferably for suppression of stray light with a photosensitive device under a cover is housed, with the help of this photosensitive Device determines the brightness and with a suitable electronic circuit 1b converted into a measurement signal 6, which is then passed on to the power supply.

0045The LEDs in the reference LED chain and the LEDs of the LED array originate preferably from the same production lot. There continue the reference LED chain with the same current is energized and both the reference LED chain and the LED array the same thermal and chemical influences are exposed, the reference LED chain provides a very reliable information on the overall brightness of the LED array.

0046The transmitted to the power supply measuring signal 6 is preferably formed so as optical output also different Levels of brightness of the LED module, for example for the Normal mode or a dimmed operation signaled can be. The power supply controls the operating current for the LED module 1 and LED array 1a so that the corresponding optical desired output size, about a desired brightness level, for example, by the controller is specified, reached and slightly exceeded.

0047To ensure compliance with the requirements regarding luminance and ensure light distribution, are the LED array the individual LED chains or corresponding LED-areas electrically monitored. Are the standard specifications no longer met, then feedback is 23 to the power supply triggered for example by an artificially generated Short circuit of the LED light source. The power supply to respond this error occurs, for example, with the melting through a Fuse, so that no current input side flows. This decrease is the input-side current at the same time (not shown) as a signal to the control module.

0048In Figure 3, the brightness 8 are as optical output P and the operating current 9 (I) of an LED module at a Embodiment of the invention in dependence of the Operating time t. The brightness is constant over 8 a predetermined minimum brightness 10 held. For this purpose, 9, the operating current is increased over time to provide a to compensate for age-related decrease in brightness. When a predetermined maximum current 24 crossing the power supply switches the LED module from eventually.

0049Figure 4 shows the corresponding quantities of A lighting device according to the prior art. Here is the operating current 9 constant, there will be no regulation. To the age-related decrease in brightness 8 under the to avoid minimum brightness level 10, is at the beginning of the operation a much larger initial brightness required. Nevertheless, the brightness decreases after a certain Operating time under the predetermined minimum brightness without that a shutdown occurs. The achievable operating time is in this case significantly shorter than in the invention.

0050Figure 5a shows an example of a part of a further Embodiment of the invention for a LED module for Confirmation of brightness levels. The LED module includes a Plurality of parallel strings of LEDs not ( shown), one of said LED-series connections as Reference LED chain 11 is provided. Preferably, these reference LED chain 11 serves only to Confirmation of the brightness level, and not for illumination. By means of a current distribution circuit 12 is the Reference LED chain 11 with the same operating current as the other LED chains of the LED module is operated.

0051A photodiode PD detects the optical output power the reference chain. The generated by the photodiode Photo-current generated at the resistors R1 and R2 different voltages with which the gate terminals the transistors T1 and T2 are driven. About these two transistors T1 and T2 as well as downstream Optocoupler OC1 and OC2 is from the photocurrent of Photodiode generates a two-stage luminance signal For example, the states of "dimming" and "Normal" can signal. This signal is in the form of a Resistance between terminals 13a and 13b.

0052The waveform is shown in Figure 5b. plotted is the resistance between the terminals 13a and 13b in Depending on the brightness of the LED module or the Reference LED chains. With increasing brightness, according the transition from the off state A via the dimmed Condition B until the normal state C, the photocurrent increases by the resistors R1 and R2, and thus the gate-source voltage at the transistors T1 and T2, the gate-source voltage is at T1 higher than the gate voltage of T2. with increasing Gate-source voltage increases and the respective drain-source current, so that the current through the drain-source path each parallel LEDs of optocouplers OC1 and OC2 is correspondingly reduced. This increases turn the output-side resistance of optocoupler OC1 and OC2, the series - having at OC1 further Parallel connection of RC - between the terminals 13a and 13b rests.

0053The two-stage waveform shown in Figure 5b comes about because in low light initially only the current through T1 increases because its gate-source voltage is greater due to the series circuit of R1 and R2 as in T2 and in particular the threshold only at T1 and still is not reached at T2, so that the optical coupler OC2 maximum driven remains. With increasing brightness finally exceeded the threshold of T2, so rises from this point also the output resistance of Optocoupler. 2

0054The resistors R1 and R2, together with the respective Threshold voltage such that the two-stage Waveform to the operating states "dimmed operation" and "Normal operation" is adapted.

0055In Figure 6 is an overall diagram of a Embodiment of the invention, comprising a power supply 2 and an LED module 1 with a LED array 1a and in Figure 5 shown circuit 1b for feedback of brightness level presented to the power supply. 2 Optionally, additional modules between the power supply and the LED array (arrow X) provided be. This is precisely in connection with Figure 7 explained.

0056The LED array 1a has in parallel a plurality LED chains 14. The LED chains 14 and the reference LED chain 11 are respectively operated with the same current. To this end, each serving the anode-side series circuit the LED string with the base-emitter path of a transistor TK and an emitter resistor RE and the compound of Bases of these transistors. The emitter resistors in this case have the same value. Alternatively, be provided different emitter resistors, wherein then a division of the currents in the LED chains carried out in accordance with the reciprocal emitter resistor values. By connecting the respective collector connected to the base TK in the transistors through the diodes and the DK Resistors RK is a for the stable operation of the Transistors TK required base current of the LED chains diverted. If an LED chain is interrupted, remains advantageously the set current distribution on the maintained other LED chains. Likewise, the Shorting individual LEDs compensated. Overall, therefore a defect of LEDs in the form of a short circuit or Interruption ( "burn") intercepted effectively.

0057As already mentioned in connection with Figures 5a and 5b is described by the reference LED chain 11 of the LED module a measurement signal generated that optical of a Output of the LED module, for example, the brightness dependent and in the form of a resistor between the Terminals 13a and 13b is fed into the power supply. 2 According regulates the power supply 2 to the operating current and / or the operating voltage of the LED module so that a predetermined optical target output size, such as a minimum brightness, is complied with, or it will turn off the LED array.

0058In Figure 7 are more circuit modules 16, 17, 18 and 19 shown that at each cumulatively or alternatively the Invention, especially in a circuit according to Figure 6 (Arrow X), may be used.

0059Module 16 includes a transistor having an "artificial Short circuit "can cause. On the part of the power supply 2 is in such an artificial short-circuit the electrical the LED module supply is interrupted or even the entire Power supply disconnected. this is preferably a Fuse provided that the supply line irreversibly interrupts.

0060This module 16 is preferred in accordance with a circuit Module 18 driven in turn by a Signal line 20 (see FIG. 6), a signal is fed, the failure of one or more strings of LEDs of the LED array displays.

0061If the AC adapter to process an "artificial Short circuit "is designed, can also by module 16 and 17 a corresponding failure of LED chains indicative Signal for the control line 13a, 13b of the power supply generated will.

0062In module 18 finally is a variable resistor and / or a thermal resistance provided which also in the Measuring signal between the pilot lines 13a and 13b flows. This can, for example, changes in the Operating temperature and an associated change in the Brightness of the LED array are considered.

0063The explanation of the invention based on the embodiments is not self-evident as limiting the invention to understand this. Instead, individual aspects of various embodiments in the scope of the invention be freely combined.