EP2066149A2 - Flat LED lights with heat-dispersing board, in particular for furniture - Google Patents

Abstract

The lamp (1) has LED modules having discrete, flat individual LEDs, and an LED power driver for producing current flow through the LED modules and/or individual LEDs. A housing formed from a semiconductor plate (2) and a cover (3), surrounds the power driver and/or the LED modules and/or LEDs. Temperature sensors e.g. semiconductor temperature sensors, are arranged within the housing and/or are in control or effective connection with the LED modules and/or LEDs so that the current flow of the LED modules and/or LEDs is lowered or deactivated during sensing a pre-specified temperature rise.

Description

The invention relates to a particular intended for furniture flat lamp with a heat-dissipating board on which one or more LED modules are applied in each thermally conductive contact, each having at least one discrete, flat single LED. Furthermore, the flat lamp comprises one or more LED current drivers for generating a suitable current flow, for example in the range between 20-700 milliamperes by the one or more LED modules and / or individual LEDs. The board of the flat lamp is connected to an at least partially transparent cover, resulting in a housing that surrounds the one or more current drivers and / or the one or more LED modules or individual LEDs.

Flat LED modules or single LEDs for mounting on SMD printed circuit boards with dimensions of 2.5 mm x 2.5 mm x 0.6 mm are already available on the market (see www.lexedis.com). Already in EP 1 729 059 A2, the design of LED modules that is as flat as possible (total height of luminaire body and LED operating device <10 millimeters) is stimulated. Among other things, the use of a flat piezoelectric transformer and the use of foil cables for the power supply serve this purpose. Particularly suitable LED modules are those without housing after the chip-on-board technology proposed, which are characterized by a small height of a few millimeters and a high light output and their metal backside an efficient dissipation of the operation of a variety allow heat generated by LEDs on the LED module.

Also in EP 1 519 106 flat LED lights are proposed, in whose housing at least one constant current source is accommodated for a plurality of LEDs. It is propagated a compact and miniaturized design. To power the LEDs, a lateral feed is provided with attached in the housing wall contact elements.

In these known flat lights there is the problem that when using strong luminous and / or a plurality of LEDs within the miniaturized flat lamp housing, a significant heat accumulation can occur. There is a risk that the operational reliability and safety of the LEDs is impaired. For example, if LEDs reach an operating temperature of 60 ° Celsius, the probability of failure can rise sharply.

Are known circuits for controlling a LED with temperature compensation ( DE 10 2006 040 711 A1 ) and the temperature-dependent power supply of an LED ( DE 198 10 827 A1 ). According to the former reference, a pulse width modulation controller is influenced by means of cold or thermistor so that the current flow of the LEDs is adjusted accordingly. The circuit according to the second-mentioned reference does without a temperature sensor by the LED operating current is compared with a reference. Common to both sources is that the disclosure is limited to circuit principles, but practical building instructions and concepts for deployable especially in the furniture sector flat-lighting products are not removable.

DE 10 2006 040 711 describes a circuit for controlling a LED with temperature compensation. The aim is to linearly regulate the luminosity and color of the LED according to temperature changes and to compensate for temperature-related changes in the properties of the LED. A controller compares a sawtooth voltage from a sawtooth generator with the output voltage of a temperature detector and generates a corresponding pulse width modulation voltage (PWM) with a duty cycle determined by the comparison result.

The invention has for its object to increase the operating reliability of a LED flat lamp with tightly enclosed in a housing single LEDs or LED modules. To solve the specified in claim 1 protection flat lamp is proposed. optional, advantageous embodiments of this invention will become apparent from the dependent subclaims.

According to the invention, one or more temperature sensors are arranged in the interior of the flat lamp surrounded by the housing. These are set in operative connection with the LED modules or individual LEDs in such a way that they can detect their respective operating temperatures and, moreover, can influence them in terms of control technology. Thus, the way is opened to the function according to the invention, when detecting a pre-specified and possibly impermissible temperature rise (beyond a predetermined temperature threshold addition) to limit or prevent the flow of current through the LED modules or individual LEDs. Thus, if the temperature in the housing increases to critical values, this can be detected with the sensor-LED structure according to the invention and the respective LED current can be regulated downwards or reduced or completely switched off. An advantage achieved thereby is that the thermal boundary conditions for the individual LEDs and their pn junctions can be kept optimal or at least within the tolerable range. Another achievable advantage is the potential energy savings; Sensory temperature sensing can be used to determine if there is an unnecessary amount of heat energy that not only degrades diode reliability, but also unnecessarily increases energy costs.

It is within the scope of embodiments according to the invention if control means are interposed or arranged between the current driver (s) and the temperature sensor (s). The control means then receive the sensor signals, process them and, depending on the received temperature sensor signals, generate control signals for the current drivers in the sense of reliable LED current operation. This structure has the advantage that it is easy to insert electronic control units such as microcontrollers or the like, by means of which intelligent operating strategies can be programmed. Alternatively or additionally, hard-wired logic or switching mechanisms are also applicable, with which equivalent Functions are feasible. Via output interfaces of the control unit and a respective drive input of the current driver (s), the LED current flow can be adjusted according to the LED operating and / or ambient temperature. The temperature information signals from the sensors may be of analog or digital format, and for example in microcontrollers, parallel input interfaces and analog / digital converters are typically formed on a chip.

A particularly advantageous embodiment of the invention is to set up the control unit to supply pulse-modulated control or actuating signals to a respective control input of the current driver (s), for example switch-on and switch-off pulses with a modulated duration. According to a particular realization example of the invention, the duty cycle (ratio of pulse period duration to pulse duration) in the pulse width modulation depends on the temperature input signals received in the control unit.

Advantageously, current drivers are used to implement the invention, which can be influenced by a particular analog control input. This opens the way to training in which the temperature sensors with analog signal outputs can directly increase or decrease the current flow or the current from the current drivers through the individual LEDs or LED modules. The effect that can be achieved is that one or more subordinate control units for controlling the current drivers, regardless of the temperature in the housing, are not loaded with a temperature management that takes place solely via the temperature sensors in conjunction with an optionally separate control input. Alternatively, it is within the scope of the invention to apply the (respective) output of the temperature sensor (s) to the (respective) control input of the current driver (s) parallel to the control output of the control unit. Beyond the output of the temperature sensor and thus dependent on the prevailing ambient and / or LED operating temperature within the flashlight housing to adjust as a ground potential level at the drive input of the current driver and adjust depending on the temperature change in the sense of a reliable LED operation, especially so that the LEDs are not too hot because of excessive current flow. The control signals from the control unit are then superimposed on this basic potential.

In terms of an expedient embodiment of the invention, the current driver has a particular switchable constant current source with a control input for actuation by control means. With such a switchable power source or sink, there are opportunities for diverse power management and thus a flexible adaptability to fluctuating temperature conditions and requirements. For further details on the LED operation with such a constant current switch is on the earlier utility model application DE 20 2007 011 973.9 as well as the same priority, older European patent application 08163063.4 of the same applicant. With a current driver, which is equipped with such a constant current switch, it is also advantageous to realize a change between DC operation and pulse width modulation current operation for the LEDs, depending on the temperature conditions, when the exceeding of a predetermined temperature threshold is detected via the temperature sensors. Then the current drivers or their constant current switches are activated accordingly.

According to a further embodiment of the invention, an embodiment is proposed to achieve a simple circuit structure and to save building components to realize the one or more temperature sensors with a temperature-dependent resistor (cold or thermistor), the current reduction at inadmissibly increasing temperature in the circuit of each individual LED is integrated and possibly reduces the flow of electricity. In particular, the resistor can be realized as a PTC thermistor (PTC) or with a positive temperature coefficient, which is arranged in series with the (respective) single LED.

According to a further embodiment of the invention, the constant current source is realized with a transistor emitter circuit whose emitter current corresponds to the current flow through the individual LEDs or determines or influences this and can be set via an emitter resistor.

According to a further embodiment of the invention, the flat lamp has a voltage source with a negative temperature coefficient and / or with a decreasing voltage as the temperature rises. Preferably, the temperature-voltage converter may comprise an output side disposed inverter. Appropriately, voltage source is realized with a voltage divider with a temperature-dependent resistor (NTC, PTC).

According to a further embodiment of the invention, the flat lamp has at least two holding magnet arrangements arranged in the region of the housing wall, which in each case also form or have electrical contact elements for supplying or supplying electric current (AC / DC) or signals.

According to a further embodiment of the invention, the flat lamp has a housing which is watertight sealed by means of full encapsulation and / or silicone compound.

According to a further embodiment of the invention, the flat lamp has electrical contact elements (17) which are arranged for connection to an electrical alternating current network (AC) in the region of the housing wall and fed to a rectifier diode (GL).

An advantageous development of the flat lamp according to the invention is to further expand it with circuit-technical means for controlling and / or status display or as an orientation light display (eg with emergency light). It is also possible to use individual LEDs for this purpose, not just multi-LED arrangements.

In the context of the invention, it is expedient to define level ranges for analog control signals to realize the switching and dimming of the flat lamp, z. B. 0-0.5 volts (corresponding to digital "low") for the off-state and 0.6-5 volts corresponding to the dimming range 1% -100% in the on state (digital, for example, according to the pulse width of a PWM signal ).

It is within the scope of the invention to integrate one or more electrical fuses in the light structurally and / or circuitry.

In the context of the invention, suitable temperature sensors are, for example, hot or cold conductors or else integrated semiconductor temperature sensors (solid-state circuits) which supply a current or voltage proportional to the temperature. In connection with digital electronic control units, semiconductor temperature sensors which are known per se are also expedient, which deliver a temperature-dependent digital signal pattern or temperature data at the output and can supply, for example, a parallel interface of a microcontroller.

When realizing the temperature sensor with a temperature-dependent voltage source, the use of a voltage divider with a temperature-dependent resistor is appropriate. This achieves the advantage of a simple circuit structure with few and inexpensive components.

The possibilities of temperature management can be further extended if z. B. in or on the wall of the flashlight housing at least one control and / or sensor element is integrated, for example, in addition to the outside temperature (outside of the flashlight housing) respond or can sense this. The corresponding temperature information can be processed, for example, in a housing-internal microcontroller as a control unit and in a Include drive signal for the LED current drivers. Furthermore, the operating and / or sensor elements are expediently connected to a bus line or another information channel in order to send out data and / or commands from the internal LED temperature and current management to external components. These may be, for example, parts of a lighting network with a plurality of light units, which are coupled with each other as a network node via a bus or other communication system information technology. For more details, refer to the earlier utility model application DE 20 2007 014 369.9 as well as the same priority, older European patent application 08 166 368.4 directed.

Adhesive and / or adhesive pads and in particular holding magnets, which are each arranged in the region of the housing wall, are suitable for fastening or holding the flat lamp to pieces of furniture, ceilings, etc. When using at least two holding magnet arrangements (with permanent magnet on or in the housing and ferromagnetic counterpart on the piece of furniture or other mounting location) the advantage of saving on components and space savings is achieved, which in turn can ultimately benefit the temperature management according to the invention. Because the two holding magnet arrangements can also be used as electrical contact elements for feeding or supply of electrical current or signals.

Figur 1

eine Flachleuchte mit Gehäuses im Längsschnitt,

Figur 2

eine Schaltungsanordnung zur temperaturabhängigen

Beeinflussung

des LED-Stromflusses,

Figur 3

eine alternative Schaltungsanordnung zur temperaturabhängigen Ansteuerung einer LED,

Figur 4a, 4b

jeweils schaltungstechnische Realisierungen eines Temperatur-Spannungswandlers,

Figur 5

eine weitere Schaltungsvariante für die erfindungsgemäße Flachleuchte,

Figur 6

eine weitere Schaltungsvariante für die erfindungsgemäße Flachleuchte,

Figuren 7-9

einzelne LED-Module mit temperatur- und stromregulierenden Schaltungen sowie Ansteuer- und Statusanzeige-Einreichungen,

Figur 10

eine prinzipielle Schaltungsskizze für einen weiteren LED-Stromkreis,

Figur 10a

eine Ersatzschaltung für einen NTC-Widerstand,

Figur 11

eine Prinzipschaltungsskizze zur Variierung des Diodenstroms,

Figur 12a-12d

Schaltungsanordnungen für weitere Konstantstromkreise,

Figur 13a, 13b

unterschiedliche Ausführungen von Stromstellern für große Ströme,

Figur 14a

eine Blockschaltbild-Darstellung für einen temperaturbeeinflussten Konstantstrom-Regelkreis für kleine Ströme,

Figur 14b

eine Blockschaltbild-Darstellung für einen temperaturbeeinflussten Konstantstrom-Regelkreis für große Ströme.

Further details, features, combinations of features, advantages and effects on the basis of the invention will become apparent from the following description of preferred embodiments of the invention and from the drawings. These show with schematic schematic diagrams in:

FIG. 1

a flat lamp with housing in longitudinal section,

FIG. 2

a circuit arrangement for temperature-dependent

influencing

the LED current flow,

FIG. 3

an alternative circuit arrangement for temperature-dependent control of an LED,

Figure 4a, 4b

each circuit technical realization of a temperature-voltage converter,

FIG. 5

a further circuit variant for the flat lamp according to the invention,

FIG. 6

a further circuit variant for the flat lamp according to the invention,

Figures 7-9

individual LED modules with temperature and current regulating circuits as well as control and status display submissions,

FIG. 10

a schematic circuit diagram for another LED circuit,

FIG. 10a

an equivalent circuit for an NTC resistor,

FIG. 11

a schematic circuit diagram for varying the diode current,

FIGS. 12a-12d

Circuit arrangements for further constant current circuits,

FIGS. 13a, 13b

different versions of current regulators for large currents,

Figure 14a

a block diagram representation of a temperature-influenced constant current control circuit for small currents,

FIG. 14b

a block diagram representation of a temperature-influenced constant current control circuit for large currents.

According to FIG. 1 the flat lamp 1, a housing 2, 3, which is composed of a board or printed circuit board 2 and a cover connected thereto 3. As indicated by the hatching, the cover 3 is suitably made of plastic, for. Transparent acrylic.
The joints between the circuit board 2 and the cover 3 can be sealed watertight by silicone compound. Alternatively, the cover 3 can be realized by a waterproof plastic full encapsulation, in which then the individual components are embedded within the housing 2, 3.

According to FIG. 1 are several single LEDs or LED modules LED spaced apart. These are controlled by an operating electronics E and supplied with a current flow or operating current. The operating electronics E includes components such as one or more constant current sources, control and / or sensor elements, pulse width modulation generators, rectifiers, DC controllers, etc., which will be explained in more detail below. For supplying power to the operating electronics E and the LEDs driven therefrom, use is made of a contact or feed-in socket 4 into which, for example, connection means of a flat line (not shown) can be plugged for the purpose of feeding supply direct or alternating current (for example, from the general alternating current network). Suitably, the contact socket 4 is formed on a front or transverse side of the elongated in the example flat lamp housing 2, 3, so that an adjacent (not shown) flat light could be introduced with a connector. For the same purpose, the illustrated flat lamp 1 has at the opposite end face a projecting connector 5, to which the fed via the contact socket 4 operating energy can be looped by means not shown lines. This can indirectly also supply an adjacent and connected via the connector 5 flat lamp with operating power. The back of the flat lamp 1, the terminals 5, 4 may be mounted in the form of simple lines or sockets. On the side or rear wall can optionally also firmly connected to the housing means for Mounting and mounting on blind holes of the mounting surface be provided, for example, furniture or ceilings. The fastening means may be in resilient retaining clips or in threaded connectors, wherein the one or more retaining clips are designed for hole diameter of preferably 30-80 millimeters. The resilient retaining clips are also suitable for engaging behind thin plates or walls through through holes.

According to FIG. 1 can, as indicated by dashed lines, the circuit board 2 also protrude from the housing 2, 3 and thereby form a cooling projection 2a. Preferably, the circuit board 2 or board for performing cooling functions as a metal core or ceramic is formed. According to FIG. 1a is the actual lamp 1 and the lamp core in comparison to the height of the housing 2, 3 applied to a relatively thin cooling plate 2b. FIG. 1b shows an embodiment, according to which the lamp 1 is embedded within a slightly thicker designed compared to the aforementioned thin cooling plate 2b cooling plate 2c or otherwise structurally integrated. By allowing further heat sinks to easily be brought into contact due to the cooling protrusion 2a or the cooling plates 2b, 2c easily accessible from the outside, the heat dissipation efficiency can be increased.

Another (not shown) possibility of cooling is the use of very small fan running z. B. with only three millimeters height, which are available in the market itself. In the printed circuit board 2 or board could be an inlet and outlet ventilation duct, preferably formed on the back of the board. It can then be mounted a commercially available flat fan in flow communication with the ventilation shaft. The airflow generated by the miniature flat fan contributes to increased cooling either in continuous operation or by switching on the fan from critical temperatures.

By means of targeted optical means arranged in the area of the light exit side of the luminaire 1, it is possible to achieve that an illuminated object for the viewer is glare-free to look at. A means may be, for example, to align the surface structure of the lamp so that light is emitted only to one side, for example, with 30 ° -60 ° exit angle. Alternatively or additionally, the LED itself can be adapted in each case by optical means for such a task, for example with what are known as "lightpipes" which are attached to the LED housing. In a housing in transparent acrylic version, it is conceivable to achieve glare-free roughening of the acrylic surface.

According to Figure 1c can be a lateral alignment of the optics or the light rays L by a beveled relative to a horizontal arrangement of the corresponding luminaire exit region of the housing reach (see. Slant angle φ in Figure 1c ). In addition, the luminaire designed in this way can be provided with contact points K _t at its bottom-side edges with light rays L emerging from the oblique surface. This housing design is suitable, for example, in the case of the LED modules according to FIG Fig. 7 - 9 ,

Generally suitable for the luminaire according to the invention is a per se known SMD design ("surface-mounted devices").

The light exit surface can be realized with a fluorescent coating (eg white-luminescent fluorophore) and / or an antibacterial coating (eg nanotechnological silver coating), which also has advantageous effects on electromagnetic compatibility (EMC) behavior. For the direction of light, the arrangement of so-called louvred grids on the LEDs is also advantageous.

According to the example of FIG. 1 are within the housing 2, 3 still three temperature sensors ∂ ₁ , ∂ ₂ and ∂ ₃ arranged at a distance from each other. A first temperature sensor ∂ ₁ is arranged for the direct detection of an LED temperature, a second temperature sensor ∂ ₂ for itself freestanding for detecting the housing interior environment and a third temperature sensor ∂ ₃ for detecting the temperature of the operating electronics. All LED and Other electronic components are expediently soldered as surface-mounted components (surface-mounted device - SMD) directly on the circuit board 2 or otherwise connected. Due to the direct installation, especially with the LEDs, a heat dissipation via the printed circuit board is provided, which may not be sufficient under certain circumstances. Alternatively or additionally, the chip-on-board technology known per se ("chip on the board") can also be used with the LEDs and the operating electronics. Both techniques result in a minimization of the height or promote the flat design for the LED light. In order to be able to attach these easily to a piece of furniture 6, magnetic fixings are each provided from a permanent magnet plate 7 arranged inside the housing 2, 3 and a ferromagnetic counterpart 8 fastened to the piece of furniture 6. Due to the magnetic attraction or adhesion between the permanent magnet plate 7 and the counterparts 8, the flat lamp 1 is held on the underside of the piece of furniture 6. As already mentioned above, the permanent magnet fixings 7, 8 can also be used as contact elements for the power supply of the operating electronics E and / or the LEDs, alternatively or additionally to the contact socket 4 or to the plug connector 5. Another alternative or additional fastening element is still possible Insert adhesive pads 9, which is sandwiched between the top of the housing 2, 3 and the bottom of the piece of furniture 6 is arranged.

According to FIG. 2 a single LED or LED module LED is operated with a constant current source K as a current driver with a known transistor emitter circuit, in which the emitter resistor R _E significantly affects the current or the current flow through the LED. This current flow is further influenced by a PTC thermistor resistance, which increases its DC resistance with temperature (positive temperature coefficient). As a result, in the event of rising temperatures it is ensured that the current flow through the LED is sufficiently reduced and the probability of failure of the LEDs does not rise unacceptably because of excessively high temperatures.

The embodiment according to FIG. 3 is different from the after FIG. 2 in that a temperature sensor is not inserted in the operating current path with the constant current I _K , but instead a drive input 10 of the constant current source K is actuated by a temperature / voltage converter 11 via a base resistor R _B1 . Temperature-voltage converters are available on the market as integrated semiconductor temperature sensors (solid state circuits) with an output voltage proportional to their temperature. In order to obtain a temperature-voltage conversion with a negative temperature coefficient is according to FIG. 3 downstream of the output of the temperature-voltage converter 11, an inverting transistor amplifier 11a, from which a temperature-dependent voltage U _∂ via the base resistor R _{B1 to} the drive input 10 of the constant current source K is supplied. In addition, the drive input 10 is connected to an output of a switching element S, which, as in FIG. 3 indicated as transistor switch can be executed. The switching element S is driven via its base resistance R _B2 by a control output of a current controller 12 operating, for example, on the basis of the pulse width modulation, which may be part of a control unit.

The operation of the circuit according to FIG. 3 is as follows: As the temperature increases, the current-dependent voltage U _∂ decreases and thus reduces the LED current flow through the base-emitter voltage U _{BE of} the constant current source K at its drive input 10. Thus, the base level of the corresponding according to a set PWM pattern pulsating constant current I _K humiliated.

According to FIGS. 4a, 4b the temperature-dependent voltage transformer can be realized by means of temperature-dependent voltage dividers. According to FIG. 4a is used as a temperature-dependent resistor (thermistor) NTC NTC thermistor with a negative temperature coefficient, one terminal is connected to ground, and the other terminal is connected to a second voltage divider resistor and the tap of the falling temperature with increasing voltage D _∂ is used. Conversely, after FIG. 4b a PTC PTC with exactly opposite temperature behavior arranged so that a terminal on the positive pole of the operating voltage U _B is located. The other terminal is connected to the grounded, second voltage divider resistor and serves to tap the falling voltage U _∂ with increasing temperature. The respectively generated temperature-dependent voltages D _∂ can be applied to the control input of the constant current source K in order to reduce the current flow through the one or more LEDs as the temperature increases.

In FIG. 5 is an example of an operating electronics E shown, which is designed to get along without over the circuit board 2 heat sink. About the in FIG. 1 illustrated contact socket 4 (or contact plug or connector 5 is a DC or AC power AC / DC supplied with a maximum level ≤ 48 volts the operating electronics E. The terminals for the input voltage U _E immediately downstream is a rectifier diode GL, at the cathode terminal itself the operating voltage U _B results. in principle, other rectifier means, for. example, full-wave rectifier in Graetz circuit, use can also find within the scope of invention, but the use of a single rectifier diode GL as shown herein in any event sufficient If one or more smoothing capacitors C _GL are arranged to ground, parallel to the smoothing capacitors C _GL is a device H for generating an auxiliary voltage U _H, for example in the amount of 5 volts for an externally (for example outside the housing) operable control and / or Sensor unit B / S (such as in the older utility model application 20 2007 014 369.9 as well as the same priority, older European patent application 08 166 368.4 described). Such operating and / or sensor units, which are in operative connection with the environment outside the housing 2, 3 and each serve to close an electrical contact, for example for switching on or dimming the flat lamp, can be: manually actuated pushbuttons, pressure sensors, touch sensors or switches, proximity sensors or switches; Brightness sensors or brightness switch, pyrosensor, gas sensor, Humidity sensor, vibration / inclination sensor, magnetic or capacitive or optical sensors, the latter three in particular with switching function. Further, on the basis of the invention, radio receivers or other means for wireless communication, electro-acoustic transducers (microphone, speakers in particular each with thin transducer membranes), signaling devices and an autonomous power supply serving solar cells and other energy storage components can be integrated. The output 13 of the control and / or sensor unit B / S is connected in parallel with a connection line 14 to an external bus or other communication system BUS (see the earlier utility model application 20 2007 014 369.9 as well as the same priority, older European patent application 08 166 368.4 the same applicant) and on the other hand connected to the drive input of a Strometreiberschalters S _IK . The output of the current driver switch S _IK is connected to the control input 10 of the constant current source K, which serves as a current driver, so that depending on the state of the control and / or sensor unit B / S or the current driver or constant current sources K activated or inactivated or the assigned LEDs can be switched on or off.

FIG. 5 goes, analogous as FIG. 3 , from a temperature-voltage converter 11 with a downstream inverter 11a, for example inverting transistor, operational or other amplifier, whose output -U _{∂ in} parallel to the (respective) control input 10 of the one or more constant current sources K and a control input 15 of a DC DC converter is supplied with externally adjustable output voltage and / or other DC adjuster 16. As indicated in the illustrated embodiment dotted lines, the connection of the temperature sensor output to the control input 15 is optional. The same applies to the connection of the temperature sensor output to the control input 10 of the constant current source (s) K. Thus, the temperature monitoring function can be realized that with increasing temperature in the housing 2, 3 to critical values, the input voltage -U _∂ at the control input 10 of or the constant current sources K and / or (alternatively or additionally) is lowered at the control input 15 of the DC adjuster 16. For the Constant current source (s) K results in the generation of a reduced current flow through the single LEDS or LED modules LED, which, as in FIG. 5 indicated, independent LED networks of different structures (see the earlier utility model application DE 20 2007 011 973.9 as well as the same priority, older European patent application 08163063.4 of the same applicant). The adjustment of the current flow through the LEDs can be adjusted according to FIG. 5 by controlling effect on the constant current sources K and / or (alternatively or additionally) on the DC adjuster 16 bring about, which is expedient anyway for reducing the DC supply level of, for example, 48 volts to 12 volts for operation of the LEDs with only high DC power supply. Via its control input 15, the output voltage U _A of, for example, 12 volts within a voltage window or a voltage tolerance ± x to the necessary adjustment of the LED current flow at increasing (or falling) temperatures vary. If, as is known, the DC-DC converter 15 is operated, for example, with pulse width modulation or pulse sequence modulation, the ratio of internal switch-on and switch-off duration or the frequency of the current pulses and thus the output voltage U _A or the LED current flow can be varied via the control input 15 be lowered, in particular, when the sensed temperature increases inadmissible. Likewise, an input voltage of, for example, 12 volts can be converted to a higher voltage.

The LED temperature monitoring system according to FIG. 6 is different from that FIG. 5 essentially by the use of a microcontroller μC. This is powered by the auxiliary voltage generator H, for example, with a 5 volt supply voltage. On the input side it is connected to the outputs of the control and / or sensor unit B / S and the temperature-voltage converter 11. Furthermore, the microcontroller .mu.C is coupled via a bidirectional data output with the connection line 14 to the external communication system BUS. On the output side, the microcontroller μC controls the DC-DC converter 16 via the control input 15 the control input 10 optionally with pulse width modulation signals PWM the constant current source or the current driver K and / or a binary switching output the current driver switch S _IK for switching on and off of the constant current sources K. The with this in FIG. 6 drawn embodiment achieved is, inter alia, that flexibly loading specific software, the temperature monitoring of the LEDs to specific requirements and constraints and customer requirements can be flexibly adjusted. Thus, the microcontroller (or other control means) programmatically (and / or circuitry) be adapted to control the one or more temperature sensors or the current driver K upon detection of a specified temperature increase and corresponding signal output that to reduce the average value of the current flow, a conversion of (previous) DC operation takes place on pulse width modulation operation.

The invention is not limited to the illustrated embodiments. So can at FIG. 6 the control of the current drive switch S _IK as after FIG. 5 directly by the operating and / or sensor unit B / S (and not by the microcontroller). Furthermore, despite the use of the microcontroller .mu.C, the output of the temperature-voltage converter could be connected directly to the control input 15 of the DC adjuster 16 and / or the control input 10 of the constant current source K. Such bypasses of the microcontroller .mu.C can reduce software cost and increase operational reliability due to elimination of potential software errors.

In FIG. 7 is a designed for miniature LED module with temperature compensation shown. Within a module housing 70 is a series circuit of an input capacitor 71 as a capacitive series resistor, a light emitting LED 72, a temperature-dependent resistor 73 which decreases the current flow with increasing temperature (PTC thermistor or PTC), and - only optional - a preferably externally controllable diode as Rectifier actuator 74 attached. For the latter can also a thyristor or a triac, optionally with phase control or phase-section control, or find a simple diode use. The LED is designed for operation with alternating current and provided on its module housing 70 with corresponding terminals AC. Furthermore, a control terminal C is attached to the outside of the housing, which could be realized with the actuator 74, a known phase-angle or phase-section drive.

According to FIG. 8 the circuit is designed in the module housing 70 for DC operation. In turn, a control input C is formed in the housing wall, which can be actuated as a function of the temperature and accordingly drives an npn transistor whose emitter terminal is connected to an LED 72. The transistor, the LED and a downstream shunt resistor can be bridged by a protective element S, for example by a thyristor realized by-pass or by a zener diode. Alternatively or in addition to the thyristor, the protective element S could also be realized with a varistor (voltage-dependent resistor).

Furthermore, the module housing 70 is still provided with a shunt connection I +, over which the current flow through the LED 72 can be increased with appropriate wiring.

For the LED module according to FIG. 9 Within the module housing 70, the LED 72 is driven by a DC / DC converter with a clock generator and a regulator on an integrated circuit IC. The set point is a temperature-dependent signal ∂ is fed to the IC. Depending on the LED 72 is driven. In addition, still another LED 92, which does not serve the lighting, but only a status or signal display, be operated by the IC. To create a resonant circuit, the LED module is externally connected to a coil which is internally fed to the IC. The latter has a pulse width modulation output to the coil.

All LED modules according to Figures 7-9 can each be provided with a single or each with multiple LED chips.

In FIG. 10 There are several ways to limit the current depending on the LED temperature. On the one hand, it is possible to connect an NTC resistor (thermistor) parallel to the LED, which leads to an increasing diversion of current flow with respect to the LED with increasing temperature. Further, the PTC resistor (PTC resistor) in parallel with the shunt resistor gives a non-linear temperature dependency of the total resistance of the parallel circuit formed by the shunt resistor and the NTC resistor. As the temperature increases, the Parallel-NTC -∂, parallel to the LED, increasingly diverts power to the LED. In PTC thermistor + ∂, which is connected in series between the LED and the current control transistor, an increase in temperature causes the current I _{L to be} reduced by the LED. According to FIG. 10a can be used in parallel with the shunt resistor and an equivalent circuit with resistor and switch instead of the PTC resistor / resistor, the last of a temperature sensor, in particular a cold or thermistor, is actuated.

According to FIG. 11 can the current flow I _L realized by the LED with a realized on the basis of a transistor constant current source K in addition to a shunt resistor to the emitter terminal. By means of a first control element C1, for example a current or voltage source, a pulse width modulator or a temperature sensor, the diode current value I _{L can be} varied. By means of a second control element C2, also connected to the base of the constant current source transistor K, the drive value at the transistor base can be reduced. In this case, a certain feedback of the current actual value or diode current I _L takes place in the control circuit. The control with the first control element C1 is thus expanded to a control loop by the addition of the second control element C2, for example potentiometer, actuator, temperature-influencing current source or the like.

In FIG. 12a is drawn another constant current circuit. The regulation of the current I _{List which} is as constant as possible for the LED is temperature-dependent via the second transistor T2. At its collector, which is connected to the base of the constant current transistor K, a terminal U _s is still attached for control purposes. According to FIG. 12b the control circuit is realized with an operational amplifier OV. Figures 12c and 12d show the opposite even more simplified circuit variants.

Figures 13a and 13b show DC / DC current controller for large currents. Common to both circuits is a pulse generator P relatively high frequency, which controls a switching element Sw. Furthermore, a coil, a diode and a variable resistor R _c are each connected in series with the LED, the diode being optional, since the LED itself already fulfills a rectifier function.

Figure 14a shows a constant current control circuit for small currents with a setpoint generator Set and a regulator Reg, wherein a comparison with the actual current I _{List of} a module with an LED takes place. Depending on this, the controller controls a switching element module. Further, a temperature sensor ∂ is arranged, which both the setpoint generator set, the controller Reg and an actual value detection module, for. B. shunt resistor module influenced. Similarly, the temperature sensor ∂ influences according to FIG. 14b the setpoint generator and regulator components of a DC / DC stage with a coil and also a shunt resistor module. The latter circuit is suitable for large currents. The stage DC / DC can after FIG. 13a or 13b be executed. As far as the current sensor θ influences the regulator Reg, a feedforward control can be realized by means of the corresponding temperature value.

After all, the temperature limitation can be made by the LED circuit itself, by a constant-current control circuit or by a control circuit.

LIST OF REFERENCE NUMBERS

1

flat light

2.3

casing

2

circuit board

2a

cool advantage

2b, 2c

Thinner or thicker cooling plate

3

cover

L

light rays

φ

oblique angle

K _t

contact point

LED

Single light emitting diode or module

e

operating electronics

4

Contact socket

5

Connectors

∂

temperature sensor

6

furniture

7

Permanent magnet plates

8th

ferromagnetic counterpart

9

adhesive pads

K

Constant current source or current driver

R _E

emitter resistor

PTC

PTC

U _B

operating voltage

U _BE

Base-emitter voltage

I _K

constant current

10

control input

R _B1 , R _B2

base resistance

11

Temperature-voltage converter

11 a

inverting transistor amplifier

S

switching element

12

power plate

U _∂

current-dependent voltage

U _E

input voltage

AC / DC

AC or DC power supply

GL

Rectifier diode

H

Auxiliary voltage generator

U _H

auxiliary voltage

R _H

Series resistor for U _H

C _H

Electrolytic capacitor for U _H

D _H

Zener diode for auxiliary voltage

B / S

Operating and / or sensor unit

13

Exit from B / S

14

connecting line

BUS

communication system

S _IK

Current driver switch

15

control input

16

DC chopper

± _X

DC chopper variation window

.mu.C

microcontroller

PWM

Pulse-width modulation signals

17

contact element

70

module housing

71

input condensate

72

LED

73

temperature-dependent resistance

74

Rectifier actuator

C

control input

S

protection element

IC

integrated circuit

I ₊

Besides Hunt connector

92

Signal indicator LED

K

Constant current source

I _L

LED current flow

C1, C2

controls

U _S

Control input voltage

T2

second transistor

OV

operational amplifiers

R _C

rheostat

P

pulse generator

sw

switching element

set

Setpoint generator

Reg

regulator

Claims (15)

Flat lamp (1) in particular for furniture (6), with a heat-dissipating board, printed circuit board (2) or other support element, whereupon one or more LED modules (LED) are applied in each heat-conductive contact, the or each at least one discrete, having flat single LED, and with at least one LED current driver (K) for generating a current flow through the one or more LED modules and / or individual LEDs, and with the printed circuit board (2), at least partially transparent cover ( 3), whereby a housing (2, 3) is formed, which surrounds the current driver (s) (K) and / or the one or more LED modules and / or individual LEDs,
characterized in that within the housing (2,3) one or more temperature sensors (∂) are arranged in such a manner with the LED modules and / or individual LEDs in control or operative connection, that upon sensing a predetermined temperature rise of the current flow (I _K ) of the LED module (s) and / or individual LEDs is reduced or switched off. Flat lamp (1) according to claim 1, characterized in that within the housing (2,3) of the current or the driver (K) provided with one or more control means, coupled and / or connected, and the output signals of the or the temperature sensors (∂) are connected or coupled to the respective control means of the one or more current drivers (K), and the or the control means and / or circuitry are designed and / or adapted to signal or a pre-specified temperature rise by the or the temperature sensors (∂) the or to drive the current driver (K) such that the current flow (I _K ) of the one or more LED modules and / or individual LEDs is reduced or turned off. Flat lamp (1) according to claim 2, characterized in that the one or more control means comprise an electronic control unit, such as microcontroller (μC), field programmable or application specific integrated circuit, with control signal output means, such as pulse or switching output (PWM), the or is connected to a (respective) drive input of the current driver (s) for adjusting the (respective) current flow through the one or more LED modules or individual LEDs, the control unit having one or more, analog and / or digital signal inputs, the the one or more temperature sensors (∂) are coupled to detect and process the pre-specified temperature rise. Flat lamp (1) according to claim 3, characterized in that the control unit is program and / or circuitry adapted to supply the respective control input (10) of the current or the current driver (K) on / off pulses, which depend on the temperature Input signals are pulse width modulated. Flat lamp (1) according to one of the preceding claims, characterized in that the one or more current drivers (K) each comprise a drive input (10) at which the one or more temperature sensors (∂) with their outputs for influencing the (respective) current driver ( K) generated current flow (I _K ) are applied. Flat lamp (1) according to claim 5, characterized in that within the housing (2,3) or the current driver (K) provided with one or more control means, coupled and / or connected, which is a (respective) on / off switch (S, S _IK ), which is connected to the (respective) control input (10) of the current or the current driver (K), wherein at the control input (10) parallel to the on / off switch (S, S _IK ) of the or the temperature sensors (∂) are applied with their outputs for influencing the current flow (I _K ) generated by the (respective) current driver (K). Flat lamp (1) according to claim 6, characterized in that the control means comprise a control unit (.mu.C, B / S), which is the output side connected to the on / off switch (S, S _IK ) for its actuation or coupled. Flat lamp (1) according to claim 7, characterized in that the on / off switch (S) comprises a switching transistor whose base input to a control signal output of the control unit (PWM, μC), and its collector output in parallel with the control input (10) of the (respective ) Current driver (K) and the (respective) output of the temperature sensor or sensors (∂) is connected. Flat lamp (1) according to one of the preceding claims, characterized in that the one or more current drivers (K) comprise a training or constant current source with a drive input (10) for actuation by control means, and the constant current source when actuated or drive for impressing a constant current (I _K ) is designed in the one or more LED modules and / or individual LEDs. Flat lamp (1) according to one of the preceding claims, characterized in that the or at least one of the temperature sensors (∂) as a temperature-voltage converter (11) or as a temperature-dependent voltage source, in particular integrated semiconductor temperature sensor is formed, the voltage output with a (respective ) Ansteuereingang (10) of the or the current driver (K) and / or an analog signal input of an electronic control unit (.mu.C) is connected or coupled. Flat lamp (1) according to one of the preceding claims, characterized in that in the wall of the housing (2,3) at least one example, ambient light, tactile pressure, touch, external and / or internal temperature and / or approach responsive control and / or sensor element (B / S) is integrated, whose output with the control input of an on / off switch (S _IK ) for the current flow of the or the current driver (K) or the or the LED modules or single LEDs connected or coupled. Flat lamp (1) according to claim 11, characterized in that the output of the control and / or sensor element (B / E) is connected to at least one bus, Informationssignal- or other connecting line (14), in one in the region of the housing (2,3) arranged contact element (17) for connection to an external information or communication system (BUS) ends. Flat lamp (1) according to one of the preceding claims, characterized by fastening and / or holding means in the form of adhesive and / or adhesive pads (9) and / or holding magnets (7), which are arranged in the region of the housing wall. Flat light (1) according to one of the preceding claims, characterized in that the cover (3) is realized with a transparent potting compound, with transparent acrylic and / or congruent with the one or more LED modules and / or individual LEDs. Flat lamp (1) according to one of the preceding claims, characterized by a DC chopper (16) or other DC converter, in the input region of the circuit of the LED modules or single LEDs for voltage / constant current conversion and / or adaptation to a housing-internal Operating Span arranged and to change its output voltage / its output current has a setting input (15) which is coupled to at least one output of the or the temperature sensors and / or one or more control means, such as microcontroller (.mu.C).

Images