Abstract:
A regulation circuit is provided for making available a constant current supply on the basis of a transformer principle, in which there flows through the luminescent diodes a triangular a.c. current varying periodically around a d.c. current value. Circuitry is provided so that both the charging and the discharging current of an inductive reactance connected in series to the luminescent diodes, functioning as a storage choke for filtering of mains harmonics, flows as diode current through the luminescent diodes. An advantage of this method consists in a significant reduction of the overall power loss of the LED illumination module. According to one embodiment, the ceramic circuit board of the LED illumination module has a direct mains current supply, which, for protection from mechanical damage, is accommodated in a transparent housing having a highly transparent polymer mass serving as an optically active lens surface.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This Application is a Division of application Ser. No. 11/028,297, filed Jan. 4, 2005, which is a Continuation of application PCT/EP03/06952 filed on Jun. 30, 2003, the entire contents of each of which are incorporated herein by reference, and the latter of which was published in German but not English as WO 2004/006629 A2 on Jan. 15, 2004, the priority of which is claimed herein (35 U.S.C. §120) and which claims priority of German Application No. 102 30 103.4 filed Jul. 4, 2002, the priority of which is also claimed herein (35 U.S.C. §119). 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a current supply for LEDs. Thereby, a transformer principle is put to use which generates a triangular a.c. current, which varies periodically around a d.c. current value, through the luminescent diodes. By means of this process it is provided that both the charging and also discharging current of an inductive reactance in the load circuit flows as diode current through the luminescent diodes. 
     2. Description of the Related Art 
     High-power light emitting semiconductor luminescent diodes (“Light-Emitting Diodes”, LEDs), briefly referred to as light diodes, have long since achieved their place in many fields in which there is need for optical display systems or illumination systems having low energy consumption, such as e.g. in traffic and signaling technologies. Through decisive technical innovations in the field of light emitting semiconductor components, with the aid of which there can today be obtained a higher light yield and an extension of the color spectrum over the entire wavelength range of visible light between 780 nm (violet) and 380 nm (dark red), optoelectronics is, in terms of lighting technology, embracing completely new markets. 
     For the attainment of a uniform illumination of surfaces, diffuser plates are employed as a rule. Due to the mains operation, above all in case of outdoor applications, light housings are usually necessary in order to protect the electronic components employed from the penetration of moisture. 
     In order to understand the central idea of the present invention, there will be briefly explained below the most important features of conventional processes and technologies according to the state of the art for the production of semiconductor luminescent diodes, above all the so-called “Chip-On-Board” (COB) Technology, which has greatly increased in significance in the last few years. 
     In “Chip-On-Board” (COB) Technology, the raw LED-chip is applied to the circuit board, with conductive adhesive, with the structure and the terminals upwards (“face up”). This procedure is called, in Anglo-American terminology, “die bonding”. After the curing of the adhesive there is effected in a further working step the connection of the chip terminals with the circuit board with the aid of a wire bonder, known from the production of integrated circuits. Thereby, the individual chip terminals and the circuit board are connected by a gold wire. Through the employment of special circuit board materials excellent heat conduction properties can be attained. From this there results a longer working life and a higher light yield per unit area. After application of a polymeric layer, the LED array is protected from mechanical damage due to shock or vibrations. Special circuit boards with reflector layers thereby serve for light bundling and increase of light intensities at smaller emission angles. 
     In comparison to conventional LED modules, through the employment of luminescent diodes which are applied to a circuit board as an LED array by means of COB technology, there can be produced efficient illumination units of high light yield, long working life, space-saving construction and a relatively slight cost outlay. Due to the light current values which can be attained, these modules are interesting not only as signalling or background illumination, but can be directly put to use as illumination means. LED arrays produced with COB technology having an emission angle of 180° permit a bright illumination of surfaces with a homogeneous light distribution, which is comparable with illumination by means of illumination equipment with fluorescent lamps operated at 40 to 50 mA. A further plus point is the 50% lesser current consumption in comparison with such illumination equipment. 
     Point light sources formed of high power luminescent diodes with COB technologies are ideally suited for small work and reading lights, as flexibly employable light sources in spot illumination, as central light source for orientation lights etc. 
     From DE 100 26 661 A1 there is known a universal compact LED illumination module which can be employed for indoor and outdoor lights in mains operation and without employment of further operating devices, such as e.g. mains transformers or specially dimensioned switch power unit parts. The light emitting semiconductor components provided as light sources are thereby controlled and supplied with current via a capacitor power unit part. In the preferred embodiment of this invention, the light emitting surfaces of the individual luminescent diodes emerge lens-like from the molding mass. As outer structural form for the LED illumination module disclosed herein there serves a molding mass (e.g. a casting resin) or a housing in which the electronic components are mounted protected from the penetration of moisture. The module can thereby be operated as a lamp or light directly from a current supply mains, can be positioned anywhere, and can be economically produced. 
     In the case of conventional capacitor power unit parts according to the state of the art (in contrast to the electronic solution in accordance with the invention) the effective value of the input alternating voltage can be selected to be variable (e.g. between 100 V AC  and 277 V AC ); even a supply of the mains part with d.c. voltage is possible. 
     Since, however, in the case of a capacitor mains power unit circuit the size of the capacitors employed increases strongly with increasing operating power, only low powers can be realized with such a mains power unit with acceptable structural size. Further, the performance of the electrolytic capacitors conventionally employed in the capacitor mains power units deteriorates with a number of operating hours. For the reasons mentioned above there is needed for the operation of high power LEDs (having an operating power of up to 4 W) the employment of alternative electronic solutions. 
     SUMMARY OF THE INVENTION 
     Starting from the above-mentioned state of the art, the present invention is concerned with the object of providing a current supply for luminescent diodes which can be adapted in simple manner to different LEDs. Beyond this, naturally, a good efficiency should also be attained. 
     This object is achieved in accordance with the invention by means of the features of the independent claims. Advantageous exemplary embodiments, which further develop the concept of the invention, are defined in the dependent claims. 
     The present invention discloses a regulation circuit in accordance with the preamble of claim  1 , which can be adapted in simple manner to the prevailing current demands of an LED. 
     With the employment of the switching principle in accordance with the invention, also a plurality of luminescent diodes connected in series can be connected to low voltages of more than 30 W. The regulation circuit thereby acts as a constant current source. 
     The process realized with the aid of this regulation circuit works in accordance with a transformer principle, with which there flows through the LED a triangular current periodically varying around a d.c. current value. Thereby, with the aid of a circuitry provision, it is provided that both the charging and also the discharging current of an inductive reactance connected in series to the luminescent diodes as a storage choke flows as diode current through the luminescent diodes. The advantage of this procedure consists in a reduction of the overall power losses of the LED illumination module. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Below, the invention will be described in more detail with reference to the accompanying drawings. 
         FIG. 1  is an exemplary embodiment of an LED illumination module, comprised of an arrangement of a plurality of luminescent diodes connected in series, fed with a.c. current via a current supply mains, which are applied on a circuit board as LED dice in a “Chip-On-Board” (COB) technology. 
         FIG. 2   a  is a first variant of a regulation circuit for making available a regulated current supply for LEDs, in which a signal transfer member employed in the feedback branch for galvanic decoupling (potential separation) is realized as an opto-coupler diode, 
         FIG. 2   b  is a second variant of the regulation circuit in accordance with the invention, for making available a regulated current supply for LEDs, in which a signal transfer member employed in the feedback branch for galvanic decoupling (potential separation) is realized as a level or potential offset stage and 
         FIG. 3  is a temporal development of the current flowing through a luminescent diode. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the following, the functions of the component groups contained in an exemplary embodiment of the present invention, as illustrated in  FIGS. 1 to 3 , will be described in more detail. The significance of the symbols provided with reference signs in  FIGS. 1 to 3  can be taken from the accompanying list of reference signs. 
     In  FIG. 1 , the basic structure of an LED illumination module  100  is schematically illustrated in longitudinal section. It has an arrangement of luminescent diodes D 1 , . . . , DN, connected in series, fed with a.c. current, which are applied to a circuit board  102  as so called LED dice in a “Chip-On-Board” (COB) technology. 
     However, the invention can just as well be employed for the control of other configurations of LEDs and in particular an individual LED. 
     In accordance with an exemplary embodiment of the invention, the heat conducting ceramic circuit board  102  of the LED illumination module  100  has a direct mains current supply, consisting of a mains part  104  and a connection cable, plug and/or socket  108  for connection to an a.c. current mains led out of the mains part  104  to the side. The luminescent diodes D 1 , . . . , DN are accommodated, for protection from mechanical damage, in a transparent housing  106  having a highly transparent polymer mass  110  serving as optically active lens surface. 
     For attaining a bundled homogeneous light distribution in the region of the main emission directions of the individual luminescent diodes D 1 , . . . , DN, the LED illumination module  100  in accordance with the invention further has so-called Fresnel lenses in the form of a lens plate which is positioned centrally above each luminescent diode D 1 , . . . , DN within the transparent housing, and adhesively fixed at the side. 
     In order to avoid the occurrence of air bubbles on the side of the circuit board  102  on which the luminescent diodes D 1 , . . . , DN are applied, upon casting of the highly transparent polymeric mass  110  within the transparent housing  106 , holes are provided in the circuit board  102 . In the production of the LED illumination module  100  the individual unhoused LED diodes D 1 , . . . , DN are, within the framework of an injection molding process or another suitable molding process directly injected around with the highly transparent polymer mass  110 . Thereby, the polymer mass  110  is of a thermally good conducting material, which acts in an electrically insulating manner. 
     Since white light cannot be generated with the aid of individual luminescent diodes there is provided in accordance with the invention the addition of a color conversion medium into the polymer mass  110  in the region of the main emission direction above the position of the monochromatic photon radiation of the luminescent diodes D 1 , . . . , DN emitting in the spectral range of the color blue. 
     Due to the space saving arrangement of the employed components and the employment of the above-mentioned efficient COB production process, the structural height of the overall arrangement of the LED illumination module  100  in accordance with the invention is not more than for example 1.0 cm. 
     In accordance with one exemplary embodiment of the basic invention, the individual luminescent diodes D 1 , . . . , DN are dimmable, whereby for dimming the brightness of the photon radiation emitted from them a control via radio or infrared signals or via a microcontroller connected to a bus is conceivable. 
     For ensuring a direct mains current supply of the circuit board  102 , the mains part  104  can in accordance with the invention be operated in a voltage input range from 100V to 277V. Thereby it can also be provided that the mains part  104  can be operated with a.c. voltage and also with d.c. voltage and along with the operation of individual LEDs can be employed for operation with serial connected and also for operation with parallel connected luminescent diodes D 1 , . . . , DN. 
     The inner sides of the transparent housing  106  (with the exception of the light emitting regions) are, in accordance with the invention, of a thermally good conducting material that on the outside, used for heat discharge, is covered with an electrically non-conducting material. Thereby, the transparent housing  106  can be contacted with the aid of a plug, socket and/or connection cable  108  led out of the housing to the side. 
     In accordance with one exemplary embodiment of the basic invention it is provided that around each individual luminescent diode D 1 , . . . , DN, formed as LED die, a parabolic or funnel-shaped reflector of a reflector plate of a thermally good conducting highly reflecting material, which reflector plate is electrically insulated on the underside, is placed on the circuit board  102  from above. Each individual reflector thereby is of a plastic with mirrored inner side. 
     The rear side of the circuit board  102  is, in accordance with the invention, coupled to a cooling body, which serves for transferring the discharge heat arising upon operation of the LED illumination module  100  to the housing  106  or to a holder (not shown). 
     With reference to  FIGS. 2   a  and  2   b , two variants of a regulation circuit in accordance with the invention will now be explained. 
     Via a rectifier full-bridge circuit V 1 , the positive and/or mains half-waves of the a.c. current I Netz  delivered from a current supply mains are rectified. At the storage capacitor C 1 , connected with the earth node, at the output of the rectifier full bridge V 1  there is thus applied a smoothed and rectified intermediate circuit voltage U C1  varying with the mains voltage Unetz . 
     After the application of a suitably dimensioned control voltage U G  to the gate of a first semiconductor power switch M 1 , for example realized as a self-blocking n-channel MOS field effect transistor, this first electronically controllable switching stage is electrically conducting, so that a drain current begins to flow, which as a consequence of the storage choke L 1  acting as an energy store, continuously increases and flows as diode current I D  through the luminescent diodes D 1 , . . . , DN. The rise of this diode current I D  upon charging of the storage choke L 1  is detected by a first low-voltage shunt measurement resistance R 5 , which at the same time is arranged in the load circuit of the first power switch M 1  and in the control circuit of the second power switch Q 1  and is connected with the earth node. Along with the two power switches M 1  and Q 1 , in accordance with the invention, a time-dependent control for switching over between the charging and discharging processes occurring in the storage choke L 1  may be provided. 
     This shunt measurement resistance R 5  may thereby preferably be constituted as a potentiometer for dimming the light intensity I V  [mcd] (i.e. the brightness), proportional to the diode current I D  [mA], of the photon radiation emitted from the luminescent diodes D 1 , . . . , DN. 
     Now, as soon as the base-emitter voltage U BE  of a second electronically controllable switching stage Q 1 , formed e.g. as a bipolar npn transistor, reaches in certain switching threshold, the semiconductor power switch Q 1  becomes electrically conducting, so that a collector current I C  begins to flow and the gate voltage U G  of the first electronically controllable switching stage M 1  temporally sinks to a “low” level, through which the switching stage M 1  is in turn blocked for a short time. This has the consequence that the diode current I D  built up via the storage choke L 1  is diverted through a free-running diode DF and a second low-voltage shunt measurement resistance R 4 , connected in series to the free-running diode, in the branch parallel to the series connection of the luminescent diodes D 1 , . . . , DN and the inductive reactance X L1 . 
     With the aid of this relatively simple circuitry measure a danger to the first semiconductor power transistor M 1  due to the induction voltage U L1  dropped at the inductive reactance X L1  upon switching off of the drain current I D  (upon blocking of the M 1 ), which can amount to a multiple of the operating voltage, is avoided. 
     The voltage U R4  dropping at the low-resistance shunt measurement resistor R 4  thereby serves for the detection of the decay of the diode current I D  through the luminescent diodes D 1 , . . . , DN, in the free-running current path, which is bonded to a minimum value by means of the switching threshold of the second electronically controllable switching stage Q 1 . 
     After feedback of the diode current I D  flowing through the luminescent diodes D 1 , . . . , DN, tapped at the second measurement resistor R 4 , to the control input of the first switching stage M 1  via a signal transfer member U 1  for galvanic decoupling (potential separation) of the voltage U R4  dropping at the second measurement resistance R 4  and the gate voltage U G  of the first switching stage M 1 , this transferred, decaying diode current I D  acts as a “new” gate current I G . This has the consequence that the gate voltage U G  of the first electronically controllable switching stage M 1  remains at the level value “low” and thus the switching stage M 1  remains blocked for so long until the current flow through the signal transfer member U 1  has fallen below a certain threshold. After the switching stage M 1  has begun again to conduct, the above described procedure is continued in a periodically recurring sequence. 
     With the process in accordance with the invention, thus both the charging and also the discharging current I L1  of the inductive reactance X L1  flow as diode current I D  through the arrangement of the serially connected luminescent diodes D 1 , . . . , DN of the LED illumination module  100  in accordance with the invention, so that there is provided a triangular current swinging periodically around a middle value. 
     The signal transfer member U 1  employed in the feedback branch of the current I D  flowing through the luminescent diodes D 1 , . . . , DN, tapped off at the second measurement resistance R 4 , to the control input of the first switching stage M 1 , which member is employed for galvanic decoupling (potential separation) of the voltage U R4  dropping at the second measurement resistance R 4  and the control voltage U G  of the first switching stage M 1 , may thereby be formed preferably as opto-coupler diode (c.f.  FIG. 2   a ) or as level offset stage (c.f.  FIG. 2   b ). A Zener diode Z 1  here serves as voltage limiter for stabilization of the control voltage U G  of the first electronically controllable semiconductor power transistor M 1  which can be tapped off at the output terminals of the opto-coupler diode or level offset stage U 1 . 
     In the realization of the second variant of the regulation circuit  200   b  in accordance with the invention, with level or potential offset stage U 1 , there are needed, additionally to the components necessary for the first variant  200   a  with opto-coupler diode, two transistor stages T 1  and T 2  and a voltage divider which is formed by means of the two resistances R 6  and R 7 . 
     In  FIG. 3  the temporal development of the diode current I D  flowing through the luminescent diodes D 1 , . . . , DN is illustrated. There is involved, as illustrated, a triangular a.c. current periodically oscillating around a middle value, the frequency of which a.c. current is determined by the switching thresholds of the control voltages U G  and U BE  needed for control of the two power transistors M 1  and Q 1 , the size of the inductance of the choke coil L 1  connected upstream of the luminescent diodes D 1 , . . . , DN, and the instantaneous value of the intermediate circuit voltage U C1  dropping at the storage capacitor C 1 . For the example sketched out in  FIG. 3 , these parameters are so dimensioned that the resulting diode current I D  preferably has a frequency of less than 100 kHz. 
     The d.c. current offset, forming the middle value of the obtained diode current I D , can be set by means of suitable dimensioning of the two shunt measurement resistances R 4 , R 5 , in order to adapt the current source to the LED concerned. In this way an economical adaptation of the diode current I D  to differing LEDs is made possible without additional circuitry measures. 
     In contrast to conventional capacitive mains parts in accordance with the state of the art, the solution in accordance with the invention is substantially more space saving. Beyond this, also application specific integrated circuits (ASICs), having a comparatively small space requirement, are conceivable. 
     
       
         
               
             
               
               
             
           
               
                   
               
               
                 List of reference signs 
               
             
          
           
               
                 No. 
                 Circuitry symbol 
               
               
                   
               
               
                 100 
                 LED light strip system, comprised of an arrangement of a 
               
               
                   
                 plurality of luminescent diodes D1, . . . , DN connected in series, 
               
               
                   
                 fed via a current supply mains with a.c. current I netz?  which are 
               
               
                   
                 applied to a circuit board as LED dice in a “Chip-On-Board” 
               
               
                   
                 (COB) technology 
               
               
                 102 
                 Heat conductive ceramic circuit board 
               
               
                 104 
                 Mains part for ensuring a direct mains current supply of the 
               
               
                   
                 circuit board 104 
               
               
                 106 
                 Transparent housing for protection of the circuit board 102, and 
               
               
                   
                 the luminescent diodes D1, . . . , DN mounted thereon as LED 
               
               
                   
                 dice, from mechanical damage 
               
               
                 108 
                 Connection cable, plug and/or socket for connection to an AC 
               
               
                   
                 current mains, led out to the side from the supply part 104 
               
               
                 110 
                 Highly transparent polymer mass, placed in the transparent 
               
               
                   
                 housing 108, serving as optically active lens surface 
               
               
                 200a 
                 First variant of the regulation circuit in accordance with the 
               
               
                   
                 invention for making available a regulated current supply for an 
               
               
                   
                 arrangement of a plurality of luminescent diodes D1, . . . , DN of a 
               
               
                   
                 LED light strip system 100, connected in series, applied to a 
               
               
                   
                 circuit board 102 as LED dice, fed with a.c. current I NETZ  via a 
               
               
                   
                 current supply mains, in which the signal transfer member 
               
               
                   
                 employed in the feedback branch for galvanic decoupling 
               
               
                   
                 (potential separation) is realized as an opto-coupler diode 
               
               
                 200b 
                 Second variant of the regulation circuit in accordance with the 
               
               
                   
                 invention for making available a regulated current supply for an 
               
               
                   
                 arrangement of a plurality of luminescent diodes D1, . . . , DN of a 
               
               
                   
                 LED light strip system 100, connected in series, applied to a 
               
               
                   
                 circuit board 102 as LED dice, fed with a.c. current I NETZ  via a 
               
               
                   
                 current supply mains, in which the signal transfer member 
               
               
                   
                 employed in the feedback branch for galvanic decoupling 
               
               
                   
                 (potential separation) is realized as a level offset or potential 
               
               
                   
                 offset stage. 
               
               
                 300 
                 Temporal development of the current I D , flowing through a 
               
               
                   
                 plurality of series-connected high power luminescent diodes 
               
               
                   
                 D1, . . . , DN of such an LED light strip system, after carrying out 
               
               
                   
                 the process in accordance with the invention for regulated 
               
               
                   
                 current supply for such an arrangement 
               
               
                 C1 
                 Storage capacitor for making available a smoothed and 
               
               
                   
                 rectified intermediate circuit voltage U C1  (varying with the 
               
               
                   
                 mains voltage U NETZ ) at the output of the rectifier full bridge V1 
               
               
                 D1, . . . , DN 
                 High power luminescent diodes (LEDs) of a LED light strip 
               
               
                   
                 system, connected in series, applied to a circuit board as LED 
               
               
                   
                 dice, realized within the scope of a “Chip-On-Board” (COB) 
               
               
                   
                 technology 
               
               
                 DF 
                 Free-running diode, connected in parallel to the series 
               
               
                   
                 connection of the high power luminescent diodes D1, . . . , DN and 
               
               
                   
                 the inductive reactance X L1  in the load circuit, for avoiding a 
               
               
                   
                 danger to the first semiconductor power transistor M1 due to 
               
               
                   
                 the induction voltage U L1 , which can amount to a multiple of 
               
               
                   
                 the operating voltage, dropping at the inductive reactance X L1   
               
               
                   
                 upon switching off of the drain current (I D ) (in the case of a 
               
               
                   
                 blocking of M1) 
               
               
                 M1 
                 First electronically controllable semiconductor power switch, 
               
               
                   
                 realized as field effect transistor (FET) e.g. as self-blocking 
               
               
                   
                 n-channel MOSFET having the control voltage U G   
               
               
                 Q1 
                 Second electronically controllable semiconductor power 
               
               
                   
                 switch, realized as bipolar npn-transistor having the control 
               
               
                   
                 voltage U BE   
               
               
                 R1 
                 Low voltage charge/discharge resistance in the branch parallel 
               
               
                   
                 to the series circuit of the high power luminescent diodes 
               
               
                   
                 D1, . . . , DN and the inductive reactance X L1   
               
               
                 R2 
                 Effective resistance of the ballast choke L 1   
               
               
                 R3 
                 Series resistance in the control circuit of the bipolar 
               
               
                   
                 npn-transistor Q1 
               
               
                 R4 
                 Second low voltage shunt measurement resistance (“shunt”) - 
               
               
                   
                 connected in series to the free-running diode DF - for detecting 
               
               
                   
                 the decay of diode current I D  in the free-running current path, 
               
               
                   
                 i.e. in the branch parallel to the series connection of the high 
               
               
                   
                 power luminescent diodes D1, . . . , DN and the storage choke, the 
               
               
                   
                 diode current flowing through the high power luminescent 
               
               
                   
                 diodes D1, . . . , DN and the storage choke L 1  during a discharge 
               
               
                   
                 process occurring in the storage choke L 1 , the decay being 
               
               
                   
                 limited to a minimum value with the aid of the first switching 
               
               
                   
                 stage M1, 
               
               
                 R5 
                 First low voltage shunt measurement resistance (“shunt”) for 
               
               
                   
                 detecting the increase of diode current I D  flowing through the 
               
               
                   
                 high power luminescent diodes D1, . . . , DN, which increase is 
               
               
                   
                 restricted to a maximum value with the aid of the second 
               
               
                   
                 switching stage Q1, the shunt preferably realized as a settable 
               
               
                   
                 resistor (potentiometer) for brightness dimming of the high 
               
               
                   
                 power luminescent diodes D1, . . . , DN, which at the same time is 
               
               
                   
                 arranged in the load circuit of the first power switch M1 and 
               
               
                   
                 the control circuit of the second power switch Q1, and is also 
               
               
                   
                 connected with the ground node 
               
               
                 R6 
                 First resistance of a voltage divider consisting of R6 and R7 for 
               
               
                   
                 the level or potential offset stage provided as signal transfer 
               
               
                   
                 member U1 within the scope of the second variant of the 
               
               
                   
                 regulation circuit 200b in accordance with the invention 
               
               
                 R7 
                 Second resistance of a voltage divider consisting of R6 and R7 
               
               
                   
                 for the level or potential offset stage provided as signal transfer 
               
               
                   
                 member U1 within the scope of the second variant of the 
               
               
                   
                 regulation circuit 200b in accordance with the invention 
               
               
                 T1 
                 First transistor stage, realized as bipolar pnp transistor, for the 
               
               
                   
                 level or potential offset stage provided within the scope of the 
               
               
                   
                 second variant of the regulation circuit 200b in accordance with 
               
               
                   
                 the invention as signal transfer member U1 
               
               
                 T2 
                 Second transistor stage, realized as bipolar npn transistor, for 
               
               
                   
                 the level or potential offset stage provided within the scope of 
               
               
                   
                 the second variant of the regulation circuit 200b in accordance 
               
               
                   
                 with the invention as signal transfer member U1 
               
               
                 U1 
                 Signal transfer member in the feedback branch of the current I D   
               
               
                   
                 flowing through the power luminescent diodes D1, . . . , DN, 
               
               
                   
                 tapped off at the second measurement resistance R4, to the 
               
               
                   
                 control input of the first switching stage M1, the member for 
               
               
                   
                 galvanic decoupling (potential separation) of the voltage U R4   
               
               
                   
                 dropped at the second measurement resistant R4 and the 
               
               
                   
                 control voltage U G  of the first switching stage M1, realized as 
               
               
                   
                 opto-coupler diode (c.f. FIG. 2a) or as level or potential offset 
               
               
                   
                 stage (c.f. FIG. 2b) 
               
               
                 V1 
                 Rectifier full bridge for rectifying the positive and/or negative 
               
               
                   
                 half-waves of the a.c. current I NETZ  delivered from a current 
               
               
                   
                 supply mains 
               
               
                 X L1   
                 Inductive reactance of a coil L1, as ballast choke for filtering of 
               
               
                   
                 harmonics, connected in series to the high power luminescent 
               
               
                   
                 diodes D1, . . . , DN, for extending the current flow duration of 
               
               
                   
                 the current flowing through the high power luminescent diodes 
               
               
                   
                 D1, . . . , DN 
               
               
                 Z1 
                 Zener diode as voltage limiter for stabilization of the input 
               
               
                   
                 voltage U Z1  at the output terminals 3 and 4 of the opto-coupler 
               
               
                   
                 diode, level or potential offset stage U1 
               
               
                 μP 
                 Microprocessor for regulating the series resistor R3, constituted 
               
               
                   
                 as a potentiometer for the purpose of dimming the high power 
               
               
                   
                 luminescent diodes D1, . . . , DN