Electric circuit arrangement

Abstract

 The present solution relates to a device for operation and control of constant current light emitting diode, LED, lamps. The device comprising at least one circuit board (405) comprising LED drive and control circuits. The device further comprises at least one user control input (101,212), at least one LED power output interface (105, 210) and at least one power supply connection (110, 205). The circuit board (405) is arranged to fit into an apparatus junction box and the circuit board (405) further comprises a micro controller controlling supply current on the LED output interface (150, 210).

Description

TECHNICAL FIELD

[0001] The present solution relates to an electric circuit arrangement. More particularly the present solution relates to a LED control drive box for operation and control of light diodes.

BACKGROUND

[0002] The technology development of Light Emitting Diodes (LED) is very fast, and new techniques are rapidly published on the market. New combinations of control, light sources and apparatus drive boxes make it difficult for users to know which type of devices to use to achieve the desired result. This is particularly relevant because of the mix of techniques within LED lighting where the drive technique is completely or partly integrated into the light source itself and gives rise to lamps of different types where the light can or can not be controlled. Also in LED lighting a case to case based decision must be taken on which type of drive technique vs control technique that shall be used to achieve a good result.

[0003] 230 V LED lamps with power from 1W can be designed as a cold light lamp which also comprises a drive device as power supply for the diode. This is the reason why these types of lamps do not need any external drive devices. However, a drawback is that the lamp can not be controlled/dimmed.

[0004] An electronic low voltage transformer which can be dimmed and which gives 12V high frequency 22-45 kHz AC can be used to drive LED lamps. These types of lamps are common today. A general electric trailing edge dimmer can normally be used to dim a lamp, unless the product specification states that the lamp is not dimmable. In that case, separate drive devices and control devices are needed.

[0005] Normally, specific LED drive devices are used which gives a constant voltage of 12 VDC or constant currents of 350, 700 or 1050 mA etc. for operation of light diodes. A LED drive device acts as a power supply for the light diodes. It converts 50Hz AC 230V (or other voltage, such as 120V used in the US) input to the low DC voltage required by the light diodes in question. The LED drive device function is similar to the functions of a high frequency (HF) device. The similarity lies in that it delivers the correct starting voltage and then controls the current which flows to the lamp after the start.

[0006] To control/dim light diodes, LED drive devices are used in addition to separate control devices giving pulse width modulated (PWM) current (PWM control devices) which are placed between the drive device and the light diode. Separate 1 - 10 Vdc control devices or separate push button switches are used for control of PWM control devices. The PWM circuit is as an exception integrated in the drive device. However, today's drive devices for light diodes with built-in PWM circuit are large and require a large space.

[0007] There are several problems related to power supply and control of light diodes which have constantly increasing effect. The problems are related to for example that operation and control in principle must be performed as stated above by using separate devices for power supply and control. This leads to matching problems when it comes to choosing the correct control device for a given drive device.

[0008] This implies further space problems related to fitting the devices into existing installation boxes, such as apparatus boxes or other limited spaces. Problems related to space is a general problem in the field of LED light, such as in down lights, floor, wall and table armatures where the development goes in the direction of smaller and smaller armatures because of the extremely small dimensions of the light diodes. This gives smaller and smaller space for those units required for operation and control of the light diodes.

[0009] Most dimmers today use off the shelf circuitry for control, however their flexibility and possibility to be adapted to system requirements are limited within each circuitry.

[0010] Rotary knob dimmers (also named wheel dimmers) are used in installation boxes and are an assembly form for control devices which has been accepted to a large extent on the market which also have been distributed to a large extent today. Rotary knob dimmers are used for control of 230V halogen lamps, 12V halogen lamps, incandescent light, fluorescent lighting etc. Approximately 700 000 rotary knob dimmers are deposited on the Swedish market each year, which emphasizes the importance of adapting the size of drive and control devices to today's standard installation boxes. An operation and control device which will fit into the shape of a rotary knob dimmer will also solve a substantial mounting problem on the market which has no sufficient solution today.

[0011] These problems regarding matching, space and mounting tend to slow down the application of the new LED technique for lighting purposes which gives large advantages regarding energy efficiency in the world, and the environmental benefits that comes with it.

SUMMARY

[0012] It is thus an object of the present invention to provide an improved dimmer with both drive devices and control devices for use in narrow places. The objects of this invention are obtained as described in the accompanying claims.

[0013] The objectives set forth above are achieved by providing, in a first aspect of the present invention, a device for operation and control of constant current light emitting diode, LED, lamps
the device comprising:

• at least one circuit board comprising LED drive and control circuits,
• at least one user control input;
  at least one LED power output interface: and
• at least one power supply connection for providing power to the circuit board and to provide output power on the LED power output interface,
  wherein the device is arranged to fit into an apparatus junction box, preferably with an inner diameter of 60 mm or less, and wherein the circuit board further comprises a micro controller for controlling the current on the LED power output interface in relation to signals obtained by the micro controller from the user control input and from a measuring unit detecting output current to the LED.

[0014] The same device may be applied for operation and control of constant voltage LED:s - the same arrangement being beneficial for mounting in very narrow places with the size of an apparatus junction box.

[0015] The micro controller may be arranged to detect signals on the user control input and to analyze the signals from the user control input in order to determine type of user control interface. The type of user control interface may be one of switch, potentiometer, push button, or pulse type. The micro controller may be arranged to detect a derivative of the signal on the user control input for determining the type of user control.

[0016] A second aspect of the present invention is provided, an arrangement for operation and control of light emitting diodes, LED,
the arrangement comprising

• a plurality of circuit boards comprising LED drive and control circuits,
• a connection arrangement arranged between each of the plurality of circuit boards;
• at least one user control input; and
• at least one power supply connection,
  wherein the arrangement is arranged to fit into an apparatus junction box or equivalent narrow spaces and wherein the plurality of circuit boards each comprises a micro controller controlling supply current on a LED output interface.

[0017] The arrangement may be comprised in a housing. In the arrangement, each of the plurality of circuit boards may be comprised in a housing.

[0018] Thanks to a small footprint, e.g. circular, and flat design of drive and control circuits for operation and control of light diodes of the constant current type, the devices occupies a minimum amount of space and may fit into a standard apparatus junction box.

[0019] An advantage of the present solution is that the dimmer/driver solution comprises control devices and drive devices which save space compared to having separate devices. The dimmer/driver solution is small which requires little space. The solution provides an advantage of fitting into apparatus junction boxes on today's market which are of "standard" size. There are also environmental and energy efficient advantages with the present solution. The size and design provides easy and simple mounting of the dimmer/driver solution for electricians on the field. Since the solution accepts several different types of user control interfaces, it also provides a flexible installation setup for the electrician on the field. Furthermore, the solution according to the present invention may provide a prolonged lifetime of LED lamps.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The invention will now be further described in more detail in the following detailed description by reference to the appended drawings illustrating embodiments of the invention and in which:

Fig. 1 is a schematic block diagram illustrating a dimmer box for operation and control of light diodes.

Fig. 2 is a schematic block diagram illustrating an exemplary embodiment of a circuit arrangement.

Fig. 3a and b is a schematic block diagram illustrating example of a modular arrangement.

Fig. 4A to E is a schematic block diagram illustrating examples of applications of the present invention.

Fig. 5 is a schematic block diagram of part of an exemplary embodiment of a circuit arrangement.

DETAILED DESCRIPTION

[0021] The present solution relates to a device for operation and control of constant current light emitting diode (LED) lamps. The solution comprises modular circular arrangements of drive circuits and control circuits in apparatus box formats with multiple control input terminals for operation and control of light diodes and connection arrangement between the modules, in addition to a synchronization function for synchronizing pulse width modulation signals in each module in the modular arrangement.

[0022] Figure 1 illustrates schematically a dimmer drive box 200 (a LED driver/control unit) for operation and control of constant current LED lamps. At least one circuit board (not shown) is comprised in a casing of the box 200. A circuit arrangement comprising drive and control circuits are provided on the circuit board(s). The drive and control circuits are designed to fit within a substantially circle shaped form with a diameter of approximately 50mm and with an output power of minimum 9 W; however other minimum powers may be applicable, being smaller or larger, e.g. 6 W or 18 W. Changing the output power may change the geometrical size. Ignition wires are connected to the circuit board(s). Some of the ignition wires are connected to a user control input 212 on the box 200. These wires are connected to a user control interface, e.g. a switch, in the other end adapted to control the operation of the circuit board. Other ignition wires are connected to an LED power output interface 210 for connection to a load such as for example a LED lamp. The box 200 also comprises a sensor (not shown) which detects the type of switch connected to the control input 212, such as for example a push button switch, a rotary knob dimmer, a touch dimmer, a potentiometer, a remote control dimmer etc. The control signals to a dimmer may for example have the values 1 - 10 VDC using a 1 - 10 V rotary button knob. The circuit board also comprises a power supply connection 205. The power supply connection 205 may for example be a regular 230VAC power supply - however other supply voltages may be applicable, such as from 100 VAC and up including line voltages in US and Europe. A micro controller (not shown) is arranged to detect signals from the user control input and to analyze the detected signals, e.g. using a derivative procedure, in order to automatically determine the type of user control interface, i.e. if the type of user control interface is for example a switch, a potentiometer, or push button type. Furthermore the micro controller is arranged to control the LED lamp output light in response to the user control, e.g. using a pulse width modulation (PWM) solution.

[0023] The dimmer drive box 200 may also comprise a current control device 220 for setting (maximum) output current, e.g. a jumper or a dip-switch. This current control device 220 may adjust the output current to for example 350mA, 500mA, 700mA or 1050mA. This current control device 220 may provide an input to the micro controller which controls the device The solution provides two different control configurations, constant current and/or PWM for the same type of load.

[0024] The dimmer drive box 200 may also comprise a synchronization communication interface for synchronizing pulse width modulation signals in each box 400 when a plurality of boxes 400 is stacked.

[0025] The circuit arrangement is provided on a circuit board having a flat and in one embodiment substantially circular design; however, other shapes of the circuit board may be applicable. The circuit arrangement is adapted to operate and control LED lamps of the constant current type. This flat and substantially circular design provides a size and form that is adaptable in standard apparatus junction boxes, for instance for mounting inside walls. An example of the circuit board is shown schematic in the block diagram in Figure 2. The dotted lines in figure 2 show barriers between the different parts of the circuit - the two parts are galvanically separated from each other. The solid line represents the box 200 in figure 2. The circuit board comprises an EMI unit 305 providing safety functions regarding electromagnetic interferences to the circuit. The EMI 305 is connected to a transformer 310. A regulator 315, e.g. a flyback regulator, is optionally connected between the EMI 305 and the transformer 310 or the regulator may be directly connected to the transformer. An opto coupler 320 is connected between the regulator 315 and a secondary regulator 325 to differentiate between the primary and secondary side, separating them galvanically. The secondary regulator 325 is the unit that makes it possible to stack a plurality of circuit boards and to synchronize them. Output from the transformer 310 is also connected to the secondary regulator 325. The secondary regulator 325 has a synchronizing wire 335 and wires connected to a dimmer device 330; it should be noted that the dimmer device 330 may be part of the circuit board. A measuring unit 340 (MEAS) is connected between the transformer 310 and the load 345, e.g. an LED lamp, and the measuring unit 340 is arranged to measuring the present output signal, e.g. the current, to the load.

[0026] The secondary regulator 325 may be controlled by a micro controller unit or a micro processor unit, such as an 8 bit controller, or a hardware based controller such as an ASIC (Application Specific Integrated Circuit) or FPGA (Field Programmable Gate Array) The solution with regulator and transformer 310 gives the desired voltage in one step as compared to solutions where two steps are required to provide the desired voltage. The transformer is designed for the specific supply voltage at the installation, e.g. 230 or 110 volts 50/60 Hz depending on location.

[0027] The secondary regulator comprises a micro controller or similar processing unit 601 (MCO) and a comparator 602 as shown in Fig. 5. The micro controller provides a reference signal through a reference signal output interface 606 to the comparator which also receives a signal related to the measurement of the current output to the LED's. The micro controller also comprise a measurement signal input interface 604, a processor 605, and a common interface unit 607. The common interface unit provides a plurality of communication/connection interfaces 603 with different external units, such as the dimmer 330 user control, maximum current setting, synchronization with other dimmer drive boxes, and so on. Depending on configurations set during installation, for instance reference to maximum current output, and dimmer level set by a user during operation, the reference signal will be set accordingly. Furthermore, the comparator provides a quick feedback solution for enabling a stable constant current setting output to the LED lamp. The comparator in turn provides a control signal through a connector 608 to the primary side via the opto coupler for controlling the output current. It should be noted that the micro controller may be arranged to provide a feedback signal directly by receiving the measured current signal and determining changes needed to keep the current stable; however, in such a solution the micro controller need to be fast enough to handle sudden changes, whereas the comparator solution is inherently fast enough to handle sudden changes.

[0028] The solution according to the present invention provides a small footprint circuitry enabling installation in a small volume, e.g. as provided in an installation box in a wall of a building. Furthermore, the present invention provides a cost effective solution for handling a plurality of different user control solutions and easy configuration between different output current levels.

[0029] A plurality of circuit boards 405 may be connected together in a modular way to form a modular arrangement 415 either by connecting a plurality of boxes 400 each comprising a circuit board 405 as illustrated in Figure 3a, or by directly connecting a plurality of circuit boards 405 via connection arrangements 410 as schematically illustrated in Figure 3b.

[0030] Irrespective of the way of connecting the modules, each module may for example have a power of minimum 9W; however, other effects may be applicable. A modular arrangement 415 comprising three modules will then have an effect of 3 X 9W, which all may be fitted together in an apparatus junction box. This effect makes it possible to use the present solution in small spaces such as down lights and LED armature for walls, ceilings, tables, floors, and in wall boxes.

[0031] As shown in figure 3a and 3b, connectors 410 are provided between the circuit boards 405 and between boxes 400 for connecting the modules together. The connection arrangements between the base units 410 give the modular arrangement 415 scalable powers up to 27 W in a standard installation box, which is a multiple of 9W.

[0032] The modular arrangement 415 or the circuit board 405 is equipped with multiple control inputs. The number of control inputs can be adjusted dependent on the system requirements. The control inputs make it possible to control the modules in the module arrangement 415 by means of for example a 1 - 10V potentiometer, via a pulse control unit, or with a push button control. The processor controlling the secondary regulator handles the user control input and determines which type of control means that is applicable; this means that one may install two different types of user interfaces at the same location and the processor may determine which is in operation at any time, e.g. both a 1-10 V dimmer and a push button solution may be connected at the same time. This universal user control determination provides a flexible solution for installment of the device.

[0033] The modular arrangement 415 is also equipped with multiple output drive currents. The number of output drive currents can also be adjusted dependent on the system requirements.

[0034] The box 400 as illustrated in figure 3a may for example have a height of 15mm and the distance between two boxes 400 may for example be 5mm. In total, a modular arrangement 415 comprising three boxes 400 may for example have a total height of 55mm. The modular arrangement 415 shown in figure 3a and 3b may fit into a standard apparatus junction box when there is a need for high power in devices such as for example rotary knob dimmers (which are a standard embodiment for installation devices for control of light). The diameter of the circular apparatus dimmer drive box 400 with casing may for example have a diameter of 57mm in order to fit into standard apparatus junction boxes, however other standard junction boxes exists with diameters of 70, 64, 60, 54 and 51 mm. In order for the circuit board 405 fitted inside the box 400 to fit such smaller junction boxes it may have a diameter of approximately 46 mm. These dimensions make it easy to fit the box 400 into standard apparatus junction boxes commonly used on the market today. It should be appreciated that non-circular apparatus junction boxes may be applicable as well, e.g. rectangular boxes for mounting in ceiling configurations.

[0035] When connecting and stacking a plurality of boxes 400, care must be taken regarding synchronization of pulse width modulation signals in each box 400. The synchronization may be provided by a synchronization communication interface. There may be several alternatives to provide synchronization of the modules. One alternative may be to use a synchronize wire where the micro controller on each module is programmed to listen to the wire to decide if it should be a master micro controller or not. The micro controller listens on the wire and if it has not heard any signal for a random time delay it will transmit on the wire and thus informing other controllers connected on the synchronization interface that it takes command as master. If the micro controller detects that another micro controller is the master micro controller it becomes a slave micro controller. Another alternative to synchronize the modules is to physically short circuit appropriate control input wires or connect them to the synchronization communication interface. In one embodiment, each controller is master to begin with until they read data on the synchronization interface. The master will not read any data on this synchronization interface and will be the only one transmitting since it is the only one receiving signals on the user control interface.

[0036] As mentioned above, the dimmer box 400 may be connected to a number of different dimmer types, such as for example toggle switch or rotary knob dimmer.

[0037] Fig. 4 illustrates a number of different applications using the present invention. In Fig. 4A is shown the example discussed earlier in this document with one control unit 501, e.g. a wheel dimmer or push button, connected to a LED driver/control unit 502 in turn controlling a LED lamp 503.

[0038] In Fig. 4B is shown a variation where one control unit 501 controls a plurality of LED driver/control units 502 each controlling a LED lamp 503. The number of LED driver/control units 502 or LED lamps 503 is not limited to the two shown but may be any number of units: 2, 3, 4, 5, 10, 20, or even higher depending on installation configuration.

[0039] Fig. 4C shows still another variation, where a plurality of control units 501 is connected to one LED driver/control unit 502. It should be appreciated that the number of control units 501 is not limited to the two shown but may be any number such as 3, 4, 5 or further up to 10 or more.

[0040] Fig. 4D shows yet another variation of usage of the present invention, where one control unit 501 is connected to a stacked LED driver/control unit 504 comprising a plurality of LED driver/control units 505, and the stacked LED driver/control unit 504 is in turn connected to a plurality of LED lamps 503. It should be appreciated that the number of LED driver/control units 505 in the stacked unit is not limited to the two shown, but may be any suitable number such as for instance 3 or more. In many applications three are used for increasing the total effect deliverable to the LED lamp 503 as discussed earlier in this document.

[0041] Fig. 4E shows a simplified example of the solution of Fig. 4D, where one control unit 501 is connected to one stacked LED driver/control unit 504, comprising a plurality of LED driver/control units 505, and where the stacked unit controls one LED lamp 503.

[0042] The LED driver/control unit 505 is arranged to operate together with several such units so as to output a synchronized control current to the LED lamp. This may be achieved by several different alternatives:

Each LED driver/control unit 505 is identical and software in each unit is arranged to detect the presence of units connected to each other as discussed earlier in this document. These then operate according to a master/slave interoperation's relationship.

Two different variations of LED driver/control units 505 are connected to each other, one master version with full operational configuration and one optimized as slave, i.e.

comprising somewhat simplified electronic configuration, in order to even further reduce costs.

[0043] The "stacked" LED driver/control unit may comprise one single "larger" LED driver/control unit capable of outputting a larger control current, e.g. 20 W, to the LED lamp(s) 503. The "stacked" LED driver/control unit is then not to be considered stacked.

[0044] In the following an example will be described for a dimmer driver system for controlling and driving a LED lamp with 9 W, max 700 mA and max 30 V from a supply voltage of 230 VAC. The first step in the solution is a half wave rectification of the incoming supply voltage of 230 VAC. This voltage is thereafter buffered using capacitances in order to provide a constant DC voltage.

[0045] Next step is the flyback converter with a switch circuit that operates at frequencies of the order 130 kHz; however, it should be noted that this is not fixed.

[0046] When the circuit is used as constant current driver, the current is measured through the load via a resistor. The signal from the resistor is connected to an operational amplifier which amplifies the signal from 0-70 mV to 0-2.5V. The amplified signal is connected to a comparator which compares the measured and amplified signal with a reference voltage signal. If the current is too large compared to the reference signal the comparator will send a signal via the opto-coupler to the switch circuit which then will shut down the feed to the primary side of the transformer. By using a comparator an analog feedback loop is created, which can react rapidly. An alternative method may be to use the processor and measure the current and let it control the signal to the opto-coupler.

[0047] In order to set the reference voltage signal, the processor sets the voltage signal digitally. This is transferred from digital to analog using for instance an R2R digital to analog converter (DAC). The measured signal indicative of the current is converted to digital using an analog to digital converter (ADC) and inputted in the processor. If the current is too large the processor decreases the reference voltage to the comparator via the DAC or respectively increases the reference voltage if the current is too small.

[0048] In order to determine the maximum voltage the load is to be driven at, a switch is located on the circuit board with settable positions for desired current drive level, e.g. 350 mA, 500 mA,, 700 mA or 1050 mA. This switch may be for instance a DIP switch. In this example the DIP-switch is set to 700mA and this is detected by the processor and the reference voltage may be controlled accordingly.

[0049] When the driver/dimmer is switched off, no current goes through the LED's. This would normally result in that the voltage over the load is driven to a maximum, e.g. 27 V depending on a zener diode provided in relation to the opto-coupler. This could in turn result in the destruction of the LED's or non desired operation of the LED's, for instance flickering action when the lamp is turned on. In order to avoid this undesired behavior, the voltage over the load is measured and regulated by the processor to a constant value during a shut down period. Alternatively, a minimum voltage level may be ramped up slowly when the lamp is turned on to create a soft build up.

[0050] As discussed earlier, there are three different ways to set the dimmer level for the load. This may be controlled by the user by controlling a standard 1-10 V dimmer, a potentiometer, or a push button. With the standard 1-10 V dimmer the regulator creates a 10 VDC source with the use of a boost circuit. The boost circuit has the purpose of amplifying a 2.5 VDC supply voltage to 10 VDC. This is done by driving the current through a coil and then disconnects the supply and lead the energy in the coil through a diode to a capacitor which is charged to desired value. This value is limited by a zener diode in parallel with a capacitor. The output voltage is then steered down by a standard external 1-10 V dimmer. The 1-10V dimmer draws current until the correct voltage is provided over the dimmer and is regulated by the user through a rotational wheel. The voltage level (1-10V) is divided down using a voltage splitting to 0.25 - 2.5 V and converted to a digital signal for the processor and handled by the regulating feedback loop in the processor. The same control solution as for the 1-10V dimmer control may handle a push button control by interpreting a 0V signal as that a push button is connected and pushed. A quick push on the push button shuts down/turns on the diodes and if the user holds in the push button the system will dimmer the current up or down alternatively.

[0051] An alternative user control is the potentiometer solution which uses the same connectors as for the other user control solutions; however, the processor need to be informed about this solution and this may be done using a switch. The processor may then determine suitable set value using a voltage divider algorithm.

[0052] In order to provide correct voltage to the processor/microcontroller independent of which voltage that is over the load, a low loss voltage regulator adapted to the processor/microcontroller is used. In order to disconnect the load completely without breaking the power supply to the processor/microcontroller, a transistor is used in series with the load and this transistor is controlled by the processor/microcontroller.

[0053] Using a PWM dimmer regulation it is also possible to provide a constant voltage solution for driving the LED's. In such a case the MEAS unit may be arranged to provide a signal responsive to the voltage instead of the current. However, the MEAS unit may be arranged to provide signals responsive of both the current and voltage.

[0054] It should be noted that the present invention is exemplified with use in an apparatus box, the solution is also applicable to other installations with an equivalent small space or volume placement.

[0055] The solution according to the present invention may prolong the life time expectancy of LEDs.

[0056] It should be noted that the word "comprising" does not exclude the presence of other elements or steps than those listed and the words "a" or "an" preceding an element do not exclude the presence of a plurality of such elements. The invention may at least in part be implemented in either software or hardware. It should further be noted that any reference signs do not limit the scope of the claims, and that several "means", "devices", and "units" may be represented by the same item of hardware.

[0057] The present invention is not limited to the above described embodiments. Various alternatives, modifications and equivalents may be used. Therefore, the above embodiments should not be taken as limiting the scope of the invention, which is defined by the appending claims.

Claims

1. A device for operation and control of at least one constant current light emitting diode, LED, lamp (345, 503),
the device comprising

- at least one circuit board (405) comprising LED drive and control circuits,

- at least one user control input (212);

- at least one LED power output interface ( 210); and

- at least one power supply connection (205) for providing power to the circuit board and to provide output power on the LED power output interface,

wherein the device is arranged to fit into an apparatus junction box of an inner diameter of 64 mm or less, and wherein the circuit board (405) further comprises a micro controller (501) controlling current on the LED power output interface (210) in relation to signals obtained by the micro controller from the user control input and from signals obtained from a measuring unit (340) detecting output current to the LED lamp.

2. The device according to claim 1,
wherein the micro controller is arranged to detect signals on the user control input (212) and to analyze the signals from the user control input (212) in order to determine type of user control interface.

3. The device according to claim 2,
wherein the type of user control interface is one of switch, potentiometer, rotary knob, push button, or pulse type.

4. The device according to claim 1,
wherein the micro controller is arranged to determine if it is to operate as master or slave.

5. The device according to claim 1
wherein the device has an output power of minimum 9W.

6. The device according to claim 1,
further comprising a synchronization communication interface.

7. The device according to claim 1,
further comprising at least one input used for setting maximum output current.

8. The device according to claim 7, wherein the maximum output current is settable to at least one of 350, 500, 700, and 1050 mA.

9. The device according to claim 1, wherein the device is arranged to fit in an apparatus junction box with an inner diameter smaller than 60 mm, or even more preferably smaller than 54 mm, or even more preferably smaller than 50 mm.

10. The device according to claim 2, wherein the micro controller is arranged to detect a derivative of the signal on the user control input for determining the type of user control.

11. The device according to claim 1, wherein the micro controller is arranged to provide a reference signal to a comparator (502) comparing output current with the reference signal and wherein the comparator in turn is arranged to provide a control signal for controlling the output current.

12. An arrangement (415) for operation and control of light emitting diodes, LED,
the arrangement (415) comprising

- a plurality of circuit boards (405) comprising LED drive and control circuits,

- a connection arrangement (410) arranged between each of the plurality of circuit boards (305);

- at least one user control input (212); and

- at least one power supply connection (205),

]wherein the arrangement (415) is arranged to fit into an apparatus junction box with an inner diameter of 64 mm or less, or equivalent volume, and wherein the plurality of circuit boards further comprises a micro controller controlling supply current on a LED output interface in relation to signals obtained by the micro controller from the user control input and from signals obtained from a measuring unit (340) detecting output current to the LED.

13. The arrangement (415) according to claim 12,
wherein the arrangement (415) is comprised in a housing (200, 400).

14. The arrangement (415) according to claim 12,
wherein each of the plurality of circuit boards (405) are comprised in a housing (200, 400).

Drawing