DE102007006438A1 - Homogeneous electrical consumer e.g. LED, arrangement controlling circuit, has consumers forming lines, where number of consumers serially connected in lines is selectable based on operating voltage and/or operational current - Google Patents

Abstract

The circuit (1) has consumers (L1, L2) e.g. LEDs, serially connected with each other and forming lines (Z1, Z2). The number of consumers serially connected in the lines is selectable based on operating voltage (Vbat) and/or operational current. Switches (S1-S3) enable connection of individual consumers to the lines, and string lines with the consumers and the switches are arranged between two supply lines. Connecting lines are provided between the string lines, and the switches and/or the consumers are arranged in the connecting lines.

Description

The The invention relates to a circuit for simultaneous control an arrangement of a plurality of in particular similar consumers, in which several consumers are connected in series and one strand form and at the several strands can be operated in parallel.

A preferred application of the present invention is in the simultaneous Control of an arrangement of light-emitting diodes, resistive heating elements or the like, preferably similar electrical consumers, of which a plurality are arranged distributed over a certain area becomes. A concrete application is the arrangement of several Light-emitting diodes in lights of a motor vehicle, in which by a area Arrangement of LEDs, the usual bulbs, for example, for the tail light, the Brake light or the like. Be replaced.

gegeben ist. Die Flussspannung V_D liegt typischerweise bei 3 Volt. In dem Versorgungsnetz eines Kraftfahrzeugs, in dem eine Leuchtdiodenanordnung betrieben werden soll, kann die zur Verfügung stehende Versorgungsspannung V_BAT bis zu 16 Volt betragen, so dass der Wirkungsgrad im Falle der Ansteuerung einer einzigen LED nur etwa 18% beträgt. Dies kann dadurch verbessert werden, dass zwei Leuchtdioden in Serie geschaltet werden, weil hierdurch der Wirkungsgrad verdoppelt wird:

Without being limited to this specific application, the invention will be described below with reference to a light-emitting diode arrangement. Typically, a light emitting diode is always operated in a current-controlled manner, since the luminous intensity is proportional to the current flowing through the light-emitting diode. As in 10 illustrated, a known transistor control ensures that a diode current I _{D flows} through the LED when a supply voltage V _{BAT is} greater than the forward voltage V _{D of} the LED. Then the LED starts to light up, the efficiency being due to the relationship

given is. The forward voltage V _D is typically at 3 volts. In the supply network of a motor vehicle in which a light-emitting diode array is to be operated, the available supply voltage V _{BAT can be} up to 16 volts, so that the efficiency in the case of driving a single LED is only about 18%. This can be improved by connecting two light emitting diodes in series, because this doubles the efficiency:

For a lamp unit, many LEDs are typically used in a field or array, so that in principle more than two LEDs can be connected in series. However, care must be taken that the supply voltage V _{BAT is} greater than the sum of the forward voltages of the series-connected LEDs or - more generally - the voltage drops on the series-connected consumers. Since in a motor vehicle, a supply voltage can also drop to about 6 volts, no circuit of three series-connected LEDs can be realized easily, because due to the fluctuating supply voltage in a motor vehicle at the lowest occurring supply voltages, the voltage for the operation of the lighting is not more would be enough.

Around nevertheless to increase the efficiency and a larger number operate in series in a light-emitting diodes in a motor vehicle to be able to are called DC / DC voltage converters such as Buck, Boost or Buck / Boost used. A DC / DC voltage converter generates a stable output voltage in adjustable height, from which the light-emitting diodes can be fed. This makes it possible the LEDs to arrays or arrays of a certain size, z. B. four strands with three light emitting diodes connected in series, d. H. 12 in total LEDs, hard to connect. These arrangements are increasingly replacing the common lightbulbs for turn signals, Tail lights, Brake lights, headlights and the like ..

A disadvantage of these currently used arrangements is the use of a DC / DC voltage converter, whose schematic diagram as an industrial chip for light-emitting diode array drive in 11 is shown. Such a voltage converter requires at least one coil and one capacitor, usually even several coils and capacitors. This causes high costs, since on the one hand cause the components as such costs and on the other hand, the assembly, the test and the maintenance of the finished module are expensive. Also problematic in the automotive environment are the electromagnetic compatibility disturbances caused by the characteristics of the switching regulators. In addition, the required volume of such voltage converter is comparatively large, so that due to the often small footprint restrictions in design must be accepted.

Object of the present invention is therefore to provide a circuit for the simultaneous activation of a Arrangement similar consumer of the type mentioned above, which has a high efficiency and without electromagnetic interference secreting control electronics, in particular without DC / DC voltage converter, gets along.

This object is achieved according to the invention with the features of claim 1, in particular in that the number of consumers connected in series in a string can be selected as a function of the operating voltage and / or the operating current. The basic idea of the invention is thus not to pre-regulate the operating or supply voltage V _BAT , but to distribute the respectively currently available supply voltage V _BAT to as many light-emitting diodes as possible. A supply voltage V _{BAT which is} too low for a particular line length can be _detected , for example, if the measured current flow of the operating current does not reach the desired or set level even by overriding the relevant control transistor. If this is the case, then the strand length, ie the number of consumers located in the strand, is reduced by so many consumers until the desired current flow is restored. If enough current flows, it may be attempted, for example at certain time intervals, to increase the length of the strand by or to the maximum possible number of consumers. However, as already stated, it is not necessary for the present invention that the consumers are light-emitting diodes. Rather, the present invention is applicable in all cases in which a plurality of preferably similar consumers are to be operated in an arrangement simultaneously. For the sake of simplicity, however, the advantages of the invention will be described below with reference to a light-emitting diode arrangement, which represents a particularly preferred embodiment of the invention.

By using the largest possible number of series-connected light emitting diodes in a strand, the efficiency can be significantly increased because the arrangement is flexibly adapted to the currently available supply voltage V _BAT . As a result, additional DC / DC voltage converter with external components are unnecessary, which in turn also have a certain power loss. Since it is known which diode voltage drops approximately at each LED in operation, the maximum number of LEDs per strand can be determined simply by the fact that the available operating voltage at least equal to the sum of the diode or Flussspannungen the serial in one strand switched LEDs must be.

Around the invention proposed flexible strand length can realize the arrangement of the consumer according to the present Have invention switch, which is the connection of individual consumers allows for a strand. The arrangements of the consumer or the light-emitting diode arrays form in the Contrary to the prior art therefore no hardwired unit more. Instead, depending on the available supply voltage individual consumers or individual groups together from consumers over Switches integrated into the circuit are connected to each other Strands with a desired one Number of consumers to realize. Through this flexible connection of loads or light-emitting diodes enables the present invention therefore, operating an array with a fixed total of Consumers in different operating modes, d. H. with different Strand number and a different number of in a strand in Series switched consumers.

Around to avoid that consumers who are not connected in one go not be used at all in certain switch positions, it is particularly according to the invention advantageous if at least some of the consumers in the arrangement by means of several interacting switches at least two different ones strands is switchable. In this way it is possible to flexibly different Strand lengths too form, with all or most of the existing in the arrangement Consumer are controlled in the control.

in this connection has been found to be a particularly flexible arrangement given then, if the arrangement of the consumer two supply lines, especially a live Line and the mass has, between which in particular parallel Strand lines are arranged with consumers and switches. This allows individual consumers the different strands connected in a simple manner become.

According to the invention can be achieve a particularly flexible arrangement in that between the strand leads connecting lines are provided, in which Switches and possibly consumers are arranged. Through this Connecting lines it is possible one or more strand lines with consumers arranged therein to interconnect a total strand and in this way strands with to reach a large number of consumers connected in series.

This is it particularly advantageous when adjacent to a connection point a branch line with a connecting line in the string line a switch and / or a consumer and in the connecting line a switch and / or a consumer are arranged. Through this Arrangement can be made at any connection point by actuating appropriate Switch flexibly selected which consumers are connected in a string. It is particularly advantageous if by connecting lines and stranded circuits closed circuits are switchable, in which at least one consumer and several switches are arranged, so that this cycle can be interrupted at appropriate places can be to the existing consumers in this cycle the one or the other strand.

Around easy to control these switches and a simple implementation to achieve the circuitry is, according to a particularly preferred embodiment the invention provides that preferably as switching transistors trained switch in a chip with connections for connection to tracks a board are integrated. In the printed circuit boards of the board can then the respective consumers, for example the light-emitting diodes the wished Be arranged. This allows a single chip with defined connections to provide for a variety of concrete arrangements used by consumers alike can be. For example, the board can also be flexible Printed circuit board, which is a particularly variable arrangement of the individual Consumer in the room allows.

There the effect of the consumer often not achieved by the supply voltage, but of that actually flowing Operating current depends, It is advantageous if in a strand not the applied operating voltage, but the operating current through a string to a constant Value is regulated. This ensures that fluctuations in the Flow voltage, mismatch, aging and temperature of consumers have no influence on their properties, for example the luminosity of the Light-emitting diodes, have.

To may in one, preferably in each switchable strand at least a switch transistor as a control transistor for adjusting the operating current be provided. This can, for example, with the aforementioned chip be integrated.

Around to be able to adjust to changing operating voltages, points the circuit preferably has a controller for setting the number the consumer per strand and the number of strands using activity the above switch on.

For this purpose, the controller, taking into account the current operating voltage V _BAT and the forward voltage V _D falling at the loads, can determine the number of consumers that can be connected in series and divide the total number of consumers by the number of consumers that can be connected in series. In this way, the number of strands can be determined, wherein in the case of a remaining (division) remainder of consumers a residual strand with a smaller number of consumers (eg light-emitting diodes) remains.

There due to the circuitry on each string, i. H. also on a residual strand, the same voltage drops, must be on this residual strand a higher one Power loss fall off than at the fully filled strands. At the waste of power loss Heat typically arises. Because big Heat sources, however usually unwanted can be provided to avoid high power losses the control a remaining strand by removing each fills one consumer from an original full strand until the number of consumers in the remainder of the number of consumers in a strand corresponds to the balance of the residual strand consumer were taken away. As a result, although the power loss in the actually full strands elevated, the particularly high power loss with strong heat development in the one However, residual strand avoided. This leads to a smoother warming the switch assembly, for example in a chip, and avoids selective heat sources.

There however, the total warming the circuit arrangement or the chip can rise sharply, if in all strands a higher one Power loss occurs, can be provided according to the invention that the Control the compensation of a remaining strand by setting a maximum number of consumers limited to a full Strand are taken away. Furthermore, can be determined according to the invention How many of the existing full strands will compensate for a remaining one Reststrangs are used. This definition can, for example limited to one or two consumers per strand, depending on the resulting power loss adjusted or by a percentage Determination of the number of consumers in a string or the number the strands be achieved.

Furthermore, in the circuit according to the invention vorgese a temperature monitoring device hen, which turns off when determining an excess temperature individual strands with consumers, in each case a strand is switched off with the smallest number of consumers connected in series, since this is the power loss is greatest.

The previously described controller and the temperature monitoring device may be common or each for be integrated into a chip, preferably in the chip, in which is also the individual switches and possibly the control transistors to set the operating current in a string. This allows it is the present invention in a single electronic component implement, which as a chip with appropriate connectors universal for one Variety of concrete arrangements of consumers on fixed or flexible boards is provided. The tracks on a circuit board are, for example, guided in such a way that the switches for interconnecting the series-connected consumers a strand are respectively contained in the chip and at their terminal sides outputs to the consumers.

Further Advantages, features and applications of the invention result also from the following description of exemplary embodiments and the drawing. All are described and / or illustrated illustrated features for itself or in any combination the subject matter of the present Invention, also independent from their summary in the claims or their back references.

It demonstrate:

1 an inventive arrangement in a schematic diagram with 2 light-emitting diodes (LEDs);

2a to 2c a circuit arrangement with 12 LEDs and 16 switches in different switching states or operating modes;

3 the theoretically achievable efficiency as a function of the available supply voltage for the arrangements according to 2 ;

4a to 4c a circuit arrangement in the form of a wiring matrix with 6 LEDs in different switching states;

5a to 5d a circuit arrangement in the form of an interconnection matrix with 7 LEDs in different switching states;

6a to 6d a circuit arrangement in the form of an interconnection matrix with 8 LEDs in different switching states;

7a to 7d a circuit arrangement in the form of an interconnection matrix with 10 LEDs in different switching states;

8th the efficiency for various circuits and operating modes in tabular form;

9a to 9d a circuit arrangement in the form of an interconnection matrix with 16 LEDs in different switching states;

10 a conventional circuit for driving LEDs with a MOS power source and

11 the block diagram of a known chip for LED array drive.

1 explains a circuit according to the invention 1 for simultaneous control of an arrangement of similar light-emitting diodes (LED) L1, L2, in which a plurality of consumer-connected LEDs L1, L2 are connected in series and form a strand Z1, with basically several strands Zj are operable in parallel, such as from 2a to 2c seen.

The number of consumers connected in series Zj in series Li is dependent on the voltage in a voltage or current source 2 Available operating voltage or operating current selectable. This will be in 1 illustrated in a simple example with two LEDs L1 and L2. When in the voltage source 2 opposite to mass 3 available operating voltage V _{BAT is} less than 6 volts and the falling across a light emitting diode voltage V _{D is} about 3 volts, the switch S2, wel remains cher in a light emitting diodes L1 and L2 connecting conductor is open. By contrast, the switches S1 in the string Z1 and S3 in the string Z2 are closed so that only one LED L1 or L2 is operated per string. In this first operating mode, the two LEDs L1 are operated in parallel in a first string Z1 and L2 in a string Z2, since the supply voltage V _{BAT of} less than 6 volts is not sufficient to connect several LEDs in series. In this case, therefore, the operating current I _{D flows} both through the strand Z1 with the light-emitting diode L1 and through the strand Z2 with the light-emitting diode L2.

In contrast, when the operating current V _{BAT is} greater than 6 volts, the switches S1 and S3 are opened and the switch S2 is closed, so that the LEDs L1 and L2 are connected in series. This switching arrangement represents the second operating mode which is activated when the operating voltage V _{BAT is} greater than the sum of the forward voltage V _D dropped across the serially connected LEDs.

In In practice, the switching of these modes of operation is often not from the available dependent battery voltage but from the current flowing through the current source. Especially with current-controlled consumers such as, for example, LEDs a switch depends from the flowing stream necessary or useful. This ensures that fluctuations in the Forward voltage, mismatch and aging and temperature of the LEDs have no influence on their luminosity.

In contrast, in the hardwired light-emitting diode arrays of the prior art, it was always necessary to ensure a sufficient operating voltage V _BAT , which is derived from the forward voltage V _D and the number of LEDs connected in series. This requires a not inconsiderable effort to provide the necessary operating voltage in a suitable manner, especially in applications with fluctuating operating voltage, such as motor vehicles. According to the present invention, however, a certain number of LEDs, depending on the available on-board or supply voltage or available diode current to parallel strands Zj series-connected LEDs Li summarized, with the actual distribution of the LEDs Li on the strands Zj can be determined on the basis of the falling at the individual LEDs Li forward voltage V _D.

Common high-luminance LEDs Li in automotive applications have a forward voltage V _D of typically about 3 volts. The operating voltage V _BAT is for automotive application in the worst case, such as a cold start at low temperatures, about 6 volts. In this case, two LEDs L1 and L2 can be connected in series. From an available operating voltage V _BAT of 9 volts, three LEDs L1, L2, L3 can be connected in series. From an operating voltage of 12 volts, the maximum number of LEDs Li in a string Zj amounts to four.

• a) 6V < V_BAT < 9V: 6 Stränge Z1 bis Z6 mit zwei seriellen LEDs L1 und L2,
• b) 9V < V_BAT < 12V: 4 Stränge Z1 bis Z4 mit drei seriellen LEDs L1 bis L3,
• c) 12V < V_BAT: 3 Stränge Z1 bis Z3 mit vier seriellen LEDs L1 bis L4.

In an LED arrangement according to the invention with 12 LEDs L1 to L12, this results in three typical operating modes:

• a) 6V <V _BAT <9V: 6 strings Z1 to Z6 with two serial LEDs L1 and L2,
• b) 9V <V _BAT <12V: 4 strings Z1 to Z4 with three serial LEDs L1 to L3,
• c) 12V <V _BAT : 3 strings Z1 to Z3 with four serial LEDs L1 to L4.

An operating mode with two strings and six LEDs is also possible with operating voltages above 18 volts. In the considered example of an application in a motor vehicle, however, such operating voltages only occur in a pulse-like manner, so that this operating mode is described in relation to FIGS 2a to 2c described circuit matrices is not realized.

As explained above, derive the number of strands Zj and the number of operating modes of the total number of used LEDs Li, where it is advantageous if the total number of LEDs used the least common multiple of the number of LEDs Li per operating mode and per string Zj is. Basically leave itself, as explained below with reference to further embodiments, also any other total numbers of LEDs Li in interconnect matrices realize.

2a shows the interconnection of a total of 12 LEDs L1 to L12 in a wiring matrix, which two supply lines 4 of which in each case one to a voltage source, not shown 2 and the other to the crowd 3 connected as basically in 1 shown. Between the two supply lines 4 are stranded pipes 5 with consumers (LEDs Li) and switches (Sk) arranged, which can be integrated into a chip. The same applies to a total of 12 ports in the chip, including the plus pole and the ground.

The LEDs L1 to L12 are usually connected directly to the circuit board, so that the connection can be realized with little effort between the chip with the integrated switches S1 to S16 and the LEDs Li, since the chip can be arranged for example on the same circuit board as the LEDs.

For the in 2a illustrated operating mode with a supply voltage V _BAT <9 volts and therefore only two series-connected LEDs Li are each the switches S2, S3, S6, S8, S11, S14 and S15 in the connecting lines 6 between the string lines 5 opened and the switches S1, S4, S5, S7, S9, S10, S12, S13 and S16 in the six stranded lines 5 closed, so that each of the strand lines 5 forms a strand Z1 to Z6.

For the in 2 B shown Verschaltungsmatrix the 12 LEDs L1 to L12 is a supply voltage V _BAT between 9 volts and 12 volts available, so that per string Zi three LEDs can be connected in series. As in a string line 5 in each case only two LEDs are arranged, are in this case switch Sk in the connecting lines 6 closed, so that in each case three LEDs are interconnected from two strand lines to a strand Zj. The resulting four strands Z1 to Z4 can be tracked along the closed switches Sk. The first strand Z1 comprises the light-emitting diodes L1, L2 and L3, which are connected in series by closing the switches S2 and S3. The second string Z2 is achieved by the series-connected LEDs L5, L6 and L4 with the switch S6 closed. The third string Z3 is achieved by closing the switches S9 and S11 and leads to an interconnection of the LEDs L7, L8 and L10. Finally, by closing the switches S14 and S15, the LEDs L11, L12 and L9 are connected together to form a string Z4.

2c shows the remaining three strands Z1 to Z3 for an operating mode in which more than 12 volts are available as the operating voltage V _BAT , so that in each case 4 LEDs per line Z1 to Z3 are connected in series.

The notation of the reference numbers corresponds to that in FIG 2a and 2 B so on a detailed description of the 2c can be waived.

It is obvious that the operating voltage V _{BAT can} also assume intermediate values of the multiple of the forward voltage V _D. However, a regulation of the current through the respective strings Zj keeps the luminous intensity of the LEDs Li constant for each operating voltage V _BAT . Since the current through the LEDs Li is directly proportional to their luminous intensity, a current control also compensates for side effects such as thermal dependencies and mismatch of the LED forward voltages V _D. For the required power sources, the respective switches Sk are used.

The current regulation itself is not the core of this invention, since current regulation circuits, as may be used in the individual strings Zj, are widely used in the art. Compared with solutions that use a pulse width modulation for luminous intensity adjustment, a solution with a regulated diode current I _{D has} the advantage that no EMC radiation is generated because no switching operations occur in the current control, so that in the context of the inventive circuit, a current control of a pulse width modulation preferable is.

The linear current control is known to produce a power loss. Therefore, the efficiency for in the 2a to 2c realized circuit in 3 represented as a function of the available operating voltage V _BAT . The course of the efficiency is similar in each case to the equation V _D / V _BAT . However, if the voltage or the current for the next longer strand Zj is sufficient with a further light-emitting diode Li, the efficiency increases abruptly.

bestimmt. Der Faktor k hängt von der jeweiligen Stranglänge, d. h. der Anzahl der in Serie geschalteten LEDs Li in einem Strang Zj ab. In dem vorbeschriebenen Beispiel mit einer Serienschaltung von 2, 3 und 4 LEDs Li beträgt der Faktor K jeweils 2, 3 und 4. Sobald die Versorgungsspannung V_BAT jeweils die Summe der benötigten Flussspannungen der beteiligten LEDs Li erreicht, steigt der Wirkungsgrad sprunghaft an.Expressed mathematically, the efficiency is due to the relationship

certainly. The factor k depends on the respective strand length, ie the number of series-connected LEDs Li in a strand Zj. In the example described above with a series connection of 2, 3 and 4 LEDs Li, the factor K is 2, 3 and 4 respectively. As soon as the supply voltage V _{BAT reaches} the sum of the required forward voltages of the participating LEDs Li, the efficiency increases abruptly.

However, the illustrated efficiency of 100% with an ideal supply voltage V _BAT is still only a theoretical value which does not take into account the on resistance of the switches Sk. In a real circuit also arise due to losses due to the resistors of the switch Sk losses, the relationship n · V D + I D · R S <V BAT <(n + 1) · V D + I D · R S applies. The switches Sk designed as switching transistors or the like must accommodate the voltage difference V _{BAT -n.V D.} In the case of an arrangement or array of 12 light emitting diodes Li, the efficiency in the worst case is 66.7%. In other words, the power loss is 50% of the net power.

at a light-emitting diode power of 5 watts corresponds to a power loss of 2.5 watts, which comes from the chip with the integrated switches Sk typically in the form of heat dissipated must become.

In contrast to the previous solutions with a hardwired number of LEDs in a string and a regulation of the operating voltage is used by the flexible connection of individual LEDs Li depending on the available operating voltage V _BAT, the LED Li itself as a voltage-dividing element. However, the excess voltage, which is calculated from the difference between the operating voltage and the sum of the forward voltages of the individual LEDs Li of a string Zj, is converted into the current sources or the switches Sk. Under normal operating conditions in a motor vehicle, the height of the on-board voltage is about 14 volts, resulting in an optimum operating module of three strings Zj with four serially connected LEDs Li to a residual voltage of about 2 volts. The efficiency for this case is 86% and is equivalent to or even better than a solution with a DC / DC voltage converter according to the prior art.

In However, a lighting unit does not exist in concrete applications always from 12 light-emitting diodes Li. The principle, the supply voltage However, variable distribution to several consumers also applies in this case.

In this case, taking into account the actual operating voltage V _BAT, the number of consumers that can be connected in series is determined and the total number of consumers is divided by the number of consumers that can be connected in series. This gives the number of strands Zj, leaving a residual strand with a smaller number of consumers in the case of a remaining remainder of consumers. In this case, it makes sense to fill a remaining residual strand by removing one consumer each from an originally full strand until the number of consumers in the remaining strand corresponds to the number of consumers in an originally completely filled strand, that is to compensate for the residual strand consumer were taken away. In this case, it makes sense to limit the number of consumers who have been taken off a full strand to, for example, one or two consumers.

This inventive method is preferably realized by a controller, which in the previously described chip with the switches Sk can be integrated. In this way, the chip forms a universal device, the a certain number of maximum available strands and switching options pretending, wherein the special arrangement of the LEDs or other Consumers through a design of the board or traces is freely definable.

This Concept will be described again below with concrete examples become.

If the total number of LEDs used, Li, does not allow a complete decomposition other than in the already described case of 12 LEDs (12 = 3 × 2 × 2), the interconnection of the matrix will be modified accordingly. For this purpose, the total number of all LEDs Li is first divided by the number of series-connected LEDs Li, which is determined by the available supply voltage V _BAT . If a remnant remains of LEDs Li, so many strands Zj are reduced by one LED, as there are excess LEDs. These are placed in the residual strand from the other LEDs, which distributes the total power loss over several strands. This leads to the result that the complete strands have switched one LED Li more in series than the remaining strands, which now also include the originally full strands, to which one (or more) LEDs have been taken away.

These Arrangement allows a distribution of the total losses incurred several switches Sk (transistors) in different strands Zj and serves to avoid so-called hotspots on the chip surface, since the power loss on a total of more different switch Sk is split.

For a better understanding follow wiring examples with 6, 7, 8, 10 and 16 LEDs in the 4 . 5 . 6 . 7 and 9 ,

In the event that in the in 4a switching circuit of six LEDs L1 to L6 are exclusively controlled with open switches Sk, a series connection of two LEDs per string and three LEDs per string (6 = 3 × 2) presents no problems in dividing the individual LEDs Li into strings Zj both circuit variants are in the 4b (two LEDs Li per string Zj) and 4c (three LEDs Li per string Zj).

4a FIG. 12 illustrates an open circuit matrix with six LEDs L1 to L6, in which all switches S1 to S7 are opened and provided with reference numerals. In the 4b and 4c In addition, the respective strands Zj, j = 2 or 3 are indicated.

However, an interconnection of four LEDs Li in series, which would be possible with a supply voltage V _BAT greater than 12 volts and the forward voltage V _{D of} a diode of 3 volts, would mean that only two LEDs L5 and L6 are available for the second string Z2 stand. This would mean a comparatively large power loss in the second strand Z2.

According to the procedure described above, the remainder of two LEDs L5 and L6 in the second string Z2 is therefore modified such that from the completely filled strand Z1 with the four light-emitting diodes L1 to L4 a light-emitting diode L4 instead of the first strand Z1 the second strand Z2 is assigned. In this case, the power dissipated evenly on the strands Z1 and Z2, each having three series-connected LEDs L1 to L3 (for Z1) and L4 to L6 (for Z2). This example corresponds to the one in 4c shown interconnection and is therefore not shown separately.

In the 5a to 5d Different circuit matrices are shown for the case that a total of seven LEDs L1 to L7 are to be controlled simultaneously. 5a again shows the unconnected state with open switches S1 to S6. In the concrete wiring examples 5b . 5c and 5d In addition, the formed strands Zj are indicated accordingly. This also applies to the other circuit arrangements shown.

With a total of seven LEDs L1 to L7, a residue remains with each interconnection, since the number 7 is a prime number. In a series circuit of a maximum of two LEDs Li in a string Zj (ie, a supply voltage V _BAT of less than 9 volts) gives three full strands Z2, Z3 and Z4 and a string Z1 with only one LED L1. This is in 5b shown. 5d shows a series circuit of four LEDs L4, L5, L6 and L7 in the string Z2 (full strand at a supply voltage V _BAT greater than 12 volts) and an interconnection of the LEDs L1, L2, L3 in the string Z1, which is not completely filled , In the in 5b and 5d However, a redistribution of the LEDs would bring no change in power dissipation.

The situation is different for a series circuit of three LEDs in a full strand (supply voltage V _BAT between 9 and 12 volts), since in this case two completely filled strands Z1 and Z2 and a residual strand would be generated with only one LED L1, in which comparatively high power loss occurs. Therefore, it makes sense in this case to assign a LED Li from a completely filled strand Zj the residual strand with only one LED Li, so that one to the in 5c shown Verschaltungsmatrix passes, in which the first strand Z1 three LEDs L1, L2, L3 is fully filled and the two strands Z2, Z3 as residual strands each have two LEDs L4, L5 and L6, L7 connected in series. The power loss is thus distributed simultaneously to the two residual strands Z2, Z3. The interconnection matrix according to 5b arise at a supply voltage V _BAT <9 volts, the circuit according to 5c for a supply voltage between 9 and 12 volts and the wiring matrix according to 5d for a supply voltage> 12 volts, assuming that a supply voltage of 15 volts can not be permanently provided.

6a shows an open circuit matrix with eight LEDs L1 to L8 and the switches S1 to S9. The in the 6b . 6c and 6d realized Verschaltungsmatrizen correspond supply voltages V _BAT less than 9 volts, between 9 volts and 12 volts and greater than 12 volts, where - as in all other examples - a forward voltage of the LEDs Li of 3 volts is assumed.

In the case of a simultaneous activation of eight LEDs L1 to L8, a series connection of two LEDs Li per line Zj or four LEDs Li per line Zj poses no problems (8 = 2 × 2 × 2). These variants are in the 6b and 6d shown. An interconnection of three LEDs Li in series per string Zj, which at a supply voltage V _BAT between 9 volts and 12 volts is possible leads to two completely filled strands Z1 and Z2, each with three LEDs L1, L2, L3 and L5, L6, L4. The third strand Z3 represents a residual strand with only two LEDs L7, L8 ( 6c ). However, the application of the redistribution rule described above in this case does not bring about a change in the distribution of the power loss since a strand which is not completely filled must always remain.

Corresponding interconnection matrices are suitable for controlling 10 LEDs ( 7a to 7d ), wherein 7a again shows an unswitched arrangement. The same applies to the 9a to 9d which shows an interconnection matrix with 16 LEDs for typical interconnection cases. Since the explanation of these figures corresponds to the above-described Verschaltungsmatrizen, is omitted a detailed description of these interconnections. In the 7b to 7d respectively. 9b to 9d the respective strands Zj are identified.

to Interpretation of the required heat dissipation for the in A chip produced power loss is the worst in the Trap achieved efficiency (WorstCase) important. For calculating This efficiency of the above-described switching matrices is crucial, how high the tension is, per string Zj over that in the string serial switched LEDs Li, over the series current sources and the switches Sk drops.

Since the current through the switches Sk, the current source and the light-emitting diodes Li in each strand is the same, it suffices to consider the voltage across the series-connected components for the efficiency calculation. The respective switching thresholds in the supply voltage V _BAT , which make it possible to connect another LED Li in series in a string Zj are at a realistic assumed forward voltages of V _D = 3 volts at 9 volts, 12 volts and 15 volts, where the threshold of 18 volts is not considered in the examples described above, as these are not reliably available in a supply network of a motor vehicle in the rule. However, the invention is not limited to the examples described above and can be extended depending on the available supply voltage.

In the table according to 8th find the efficiency calculations for the examples described above. This is described by way of example for the case of a light-emitting diode arrangement with six light-emitting diodes (6-LED array) and an operating voltage V _BAT of just 9 volts, which still does not allow switching to three series-connected LEDs Li per line Zj. In this case, there are three parallel strings Z1, Z2, Z3, each with two series-connected LEDs Li. The total, on all involved LEDs falling forward voltage is therefore 6 × V _D , which corresponds to the useful power. The residual voltage is 3 × (9 volts - 2 × V _D = 3 Vd), which corresponds to the maximum power dissipation. The efficiency is thus:

A complete list of the efficiencies for all the variants described above can be found in 8th , It can be seen that the efficiency is in the unlikely event of seven LEDs to be driven, even in the worst case, 58%. In the normal automotive environment, the operating voltage (on-board voltage) V _{BAT is} typically about 16 volts. Depending on the number of LEDs to be operated, the efficiency increases up to 86%.

In the case an overtemperature On the chip, a temperature monitor always turns on first Strand Zj with the at least serial LEDs Li off, because for this have to the serial switches Sk and the power sources the most power loss implement. This has the advantage that on the one hand, the thermal load of the chip the strongest decreases, but on the other hand, the overall luminosity least influenced is because only a few LEDs are turned off. Should several strands the Can have at least a minimum number of LEDs and not be fully occupied, so can if necessary only one strand Zj be switched off. The rest, too not completely filled or occupied strands Zj can then filled with the now freed LEDs to full strands, to reduce their power loss.

This shows that with the inventive wiring of LEDs in dependent of the operating voltage V _BAT different strand arrangements, a high degree of performance can be achieved without a Vorabregelung the operating voltage. This leads to lower manufacturing costs, a higher reliability of the circuit by reducing the complexity, due to the saved switching elements to a lower weight of the circuit and a reduced overall volume. Furthermore, an EMC radiation is avoided.

The inventive principle, the load consisting of more than one consumer with a variable supply voltage to connect so that the supply voltage without conversion maximum is charged, applies in addition to the concrete described using light-emitting diodes Example also for other loads, such as resistive heating elements.

1

circuit

2

voltage or power source

3

Dimensions

4

supply lines

5

string cables

6

interconnectors

Li

led LED, i = 1, ..., n

zj

strand several series-connected LEDs, j = 1, ..., m

sk

Switch, k = 1, ..., l

V _BAT

Operating voltage, supply voltage

V _D

forward voltage

I _D

diode current

Claims (15)

Circuit for the simultaneous control of an arrangement of similar consumers (Li), in particular of light-emitting diodes, resistive heating elements or the like., In which a plurality of consumers (Li) are connected in series and form a strand (Zj) and in which a plurality of strands (Zj) are operable in parallel , characterized in that the number of in a string (Zj) serially connected consumer (Li) in dependence on the operating voltage (V _BAT ) and / or the operating current (I _D ) is selectable. Circuit according to Claim 1, characterized that arrangement of the consumer (Li) switch (Sk) has, which enable the connection of individual consumers (Li) to a string (Zj). Circuit according to Claim 2, characterized that a part of the consumer (Li) in the arrangement by means of several cooperating switch (Sk) of at least two different strands (Zj) is switchable. Circuit according to one of the preceding claims, characterized in that the arrangement of the consumers (Li) two supply lines ( 4 ), between which strand lines ( 5 ) are arranged with consumers (Li) and switches (Sk). Circuit according to Claim 4, characterized in that between the stranded conductors ( 5 ) Connecting cables ( 6 ) are provided, in which switch (Sk) and / or consumers (Li) are arranged. Circuit according to Claims 4 and 5, characterized in that adjacent to a connection point of a branch line ( 5 ) and a connection line ( 6 ) in the line ( 5 ) a switch (Sk) and / or a consumer (Li) and in the connecting line ( 6 ) a switch (Sk) and / or a consumer (Li) are arranged. Circuit according to one of Claims 2 to 6, characterized in that the switches preferably designed as switching transistors (Sk) into a chip with connections are integrated for connection to printed conductors of a circuit board. Circuit according to one of the preceding claims, characterized in that the operating current (I _D ) is controlled by a string (Zj) to a constant value. Circuit according to Claim 8, characterized that in one strand (Zj) a switch transistor as a control transistor is provided for adjusting the operating current. Circuit according to one of Claims 2 to 9, characterized that a control for adjusting the number of consumers (Li) per strand (Zj) and number of strands (Zj) by means of actuation of the switches (Sk) is provided. A circuit according to claim 10, characterized in that the controller, taking into account the current operating voltage (V _BAT ) determines the number of series-connectable consumers (Li) and the total number of consumers (Li) by the number of series-connectable loads (Li) divides to determine the number of strands (Zj), leaving a residual strand (Zj) with a smaller number of consumers (Li) in the case of a remaining remainder of consumers (Li). Circuit according to Claim 11, characterized that the controller has a remaining remainder strand (Zj) by removal from one consumer (Li) from an originally full strand (Zj) fills until the Number of consumers (Li) in the residual strand (Zj) of the number of Consumers (Li) in a string (Zj) equals, to compensate of the residual strand (Zj) consumer (Li) were taken away. Circuit according to Claim 12, characterized that the control balancing a remaining strand (Zj) by setting a maximum number of consumers (Li) limited, which are taken away a full strand (Zj). Circuit according to one of the preceding claims, characterized in that a temperature monitoring device is provided which is when determining an excess temperature individual strands (Zj) with consumers (Li) turns off, with one strand (Zj) with the smallest number of consumers connected in series (Li) is switched off. Circuit according to one of Claims 9 to 13, characterized that the switches (Sk), the controller and / or the temperature monitor integrated into a chip.