WO2017081020A1

WO2017081020A1 - Current control circuit and circuit arrangement for the same

Info

Publication number: WO2017081020A1
Application number: PCT/EP2016/077001
Authority: WO
Inventors: Peter Kempf
Original assignee: Chromasens Gmbh
Priority date: 2015-11-09
Filing date: 2016-11-08
Publication date: 2017-05-18
Also published as: DE102015119241B4; DE102015119241A1

Abstract

The invention relates to a current control circuit (30) for distributing a current from a common current source (P1) to a multiplicity of parallel consumer networks (40) at a predefined current distribution ratio, and to a circuit arrangement (100) having the current control circuit (30) and the consumer networks (40). The current control circuit (30) has, for each of the consumer networks (40), a self-blocking power transistor (T1) in series with the consumer network (40); a working resistor (R2) in series with a power transistor (T1), on the side of the latter that faces away from the consumer network (40), wherein a working potential (V3) is defined between the working resistor (R2) and the power transistor (T1); a control resistor (R2), one side of which is connected to a control reference potential (V6) that is uniform for the entire current control circuit (30); a control transistor (T2), which is connected in a current path formed between the working potential (V3) and the other side of the control resistor (R2), facing away from the control reference potential (V6). The control electrode of the control transistor (T2) is connected to the control electrodes of the control transistors (T2) of all other consumer networks (40), in order to form a base potential (V7) that is common to all control transistors (T2). A current path which leads via a compensating resistor (R5) to a reference working potential (VA) that is different from the base potential (V7) branches off from the common base potential (V7). A control electrode of the power transistor (T1) is connected to the current path between the control transistor (T2) and the control resistor (R2) which are provided for exactly one other of the consumer networks (40). For each of the consumer networks, a control diode (D2) is provided between the reference work potential (V8) and the current path formed between the control transistor (T2) and the control resistor (R2). Furthermore, the current control circuit (30) has a Zener diode (D3), which is connected between the control reference potential (V6) and a potential defined by the interconnected sides of the working resistors (R2) that face away from the respective power transistor (T1).

Description

Stromsteuerschaltunq and Schaltunqsanordnunq with it

The present invention relates to a current control circuit and a circuit arrangement comprising the current control circuit and a plurality of parallel consumer networks, each having a plurality of series-connected LEDs. The power control circuit is for distributing a current from a common power source to the plurality of power grids at a predetermined current dividing ratio.

In optical inspection devices, in particular in optical spectrometers, circuits are used in which a plurality of light sources, each comprising a plurality of diodes, emit light with a predefined, in particular the same luminosity. With an external constant current source, a predetermined current is supplied. In order for the same current to flow through all the diodes, it is basically desirable to arrange all the diodes in a single current branch. However, this is not always possible, since the voltage across the individual diodes (approximately 3 to 4V) would add in each case, the required total supply voltage increases considerably. For approval reasons, however, you do not want to use voltages above 48V. Therefore, it may be necessary to distribute the diodes to several, parallel-connected current branches. The accuracy of the distribution of the total supply current to the current branches over a wide current range (for example for dimming the brightness) is important here.

Controlling the current through diodes is not easy, as the behavior of the diodes is extremely non-linear. The hotter a diode gets, the better it conducts. As a result, it draws more electricity, which would make them even hotter. An active control of the current is therefore necessary.

For the described application, it is known to use a current mirror in which one LED chain branch mirrors the current of the other branch. However, it must be decided after the printed circuit board production, which branch is the reference to operate the other then mirrored. The decision as well as dimensioning of the mirroring is set manually with the help of wire bridges after production. Some such circuit proposals of current mirrors are known in the art, but all of which do not allow automatic current sharing which eliminates manual calibration after production. While there are circuit proposal for current dividers, none have been identified that are useful for applications of the above-mentioned high current requirements.

Further circuits for driving light-emitting diodes are disclosed in US 2007/008091 1 A1, US 2014/0062314 A1, WO 201 1/150772 A1, WO 2014/0539933 A1, JP 2013-157493 A. It is therefore an object of the present invention to provide a current control circuit for distributing a current from a common current source into a plurality of parallel current branches having a predetermined current dividing ratio of respective supply currents in the current branches to supply a respective consumer network in each branch current through the respective supply current which fulfills at least one of the following requirements:

- an automatic power split;

- an improvement in accuracy;

Robustness (for example, to current and circuit element tolerances);

- good dynamic behavior (especially when switching on and off, as well as in pulse mode);

- simplicity in construction;

- Reusability of the same LED chain structure as in the previous lighting, as well as the same power transistors;

high efficiency (in particular small power loss of the control circuit)

Adaptability to unequal flow sharing ratios over a wide range; such as

- Expandability to multiple (more than two) LED chain branches.

The object is achieved at least in part by the features of the independent claims. Advantageous developments and embodiments form the subject of the dependent claims.

According to one aspect of the present invention, there is provided a current control circuit for distributing a current from a common power source to a plurality of parallel load networks having a predetermined current dividing ratio. Each of the consumer networks has in particular a plurality of series-connected LEDs. The power control circuit has a self-locking one for each of the power networks Power transistor, in particular field effect transistor, preferably MOSFET, in series with the consumer network; a load resistor in series with the power transistor on its side remote from the load side, wherein a working potential is defined between the load resistor and the power transistor; a control resistor whose one side is connected to a common control reference potential for the entire current control circuit, a control transistor, in particular bipolar transistor, which is connected in a formed between the working potential and the other, remote from the control reference potential side of the control resistor current path on. In this case, the control electrode of the control transistor is connected to the control electrodes of the control transistors of all other consumer networks to form a base common to all control transistors. A control electrode of the power transistor is connected to the current path between the control transistor and the control resistor, which are provided for exactly another of the consumer networks.

In this current control circuit, the current is detected by the individual power networks by means of the load resistors and coupled by means of the control transistors to the power transistor of another consumer network. This cross-coupling or negative feedback independently regulates the ratio of the currents through the individual consumer networks.

The coupling of the common base potential with the current paths between the control transistor and the control resistor may be formed by means of control diodes, wherein a respective control diode between each current path between the control transistor and the control resistor and the base potential is arranged. In this current path, there is a gate potential for driving the respective power transistor of the other consumer network. By coupling the base potential by means of the control diodes, the base potential is coupled to the respective largest gate potential of all consumer networks.

Preferably, the control electrodes of all current branches are connected to each other and form a reference working potential, which is connected by means of a compensation resistor to the base potential. Furthermore, the current control circuit may have a Zener diode which is connected between the control reference potential and a potential defined by the interconnected sides of the load resistors facing away from the respective power transistor.

For the purposes of the present invention, a plurality is a number of two or more. The plurality of consumer networks is preferably two, three or four. A consumer network is within the meaning of the invention, any circuit that requires the supply of electricity and causes a voltage drop. Preferably, the consumer network has a series connection of a plurality of light-emitting diodes, that is to say a so-called LED chain. However, the application of the invention is not limited to the supply of LED chains. In this case, a conductor section can be designed in any desired manner, for example as a conductor track, connection pad or potential lake on a printed circuit board, a cable, a busbar, a stranded wire or the like. If in the context of the invention in the physical sense of a specific, specifically designated potential is spoken, including a conductor section to understand that has the so-called potential. That is, when a circuit element is connected to a potential, this is to be understood in the sense of the invention as meaning that the circuit element is connected to the potential-carrying conductor section. If two circuit elements are described as being parallel, this is to be understood in the sense of the invention as meaning that the circuit elements are connected in parallel between a first conductor section (a first potential) and a second conductor section (a second potential). A current sink potential in the context of the invention is a potential that is lower than an input potential of a circuit. In concrete terms, the current sink potential may be a collective sink potential of a circuit arrangement with the consumer networks and the current control circuit. In particular, but not necessarily, the current sink potential is identical to the zero potential (the "ground") of the current source. The current sink potential can also be decoupled from the zero potential by an ohmic resistor. In the context of the invention, a control reference potential is a same external potential for the entire current control circuit, that is to say with respect to all branches of the current control circuit, which is decoupled from the consumer networks by an ohmic resistor (scaling resistor). When a circuit element is connected in series in a current path, in the case of the transistor this refers to the connection of the main electrodes (source / drain for a field effect transistor and collector / emitter for a bipolar transistor) in the current path, in the case of bipolar circuit elements to the two poles. Unless otherwise stated, identically named circuit elements in all branches of the current control circuit can be understood to be dimensioned the same.

By the current control circuit described above, the current is automatically distributed to the plurality of parallel load networks so that a predetermined current division ratio can be maintained with high accuracy and stability. The power control circuit has a simple structure and can be applied to two or more power networks. It is robust against current and circuit element tolerances and has good dynamic performance and low power dissipation. With the same working resistances, a uniform current sharing ratio between all consumer networks (50:50 for two consumer networks) can be achieved. The circuit allows the reuse of Thung transistors of conventional power control circuits and requires no further changes to the structure of existing, provided in the consumer networks LED chains.

The control transistor according to the present invention may be a bipolar transistor. These can be constructed as an NPN transistor or as a PNP transistor. Depending on the design of the control transistor, the order and polarization of the circuit elements of the power control circuit with each other and with respect to the consumer networks may need to be adjusted.

If the control transistor is an npn transistor, the load networks are provided on the side of a common main supply potential supplied by the power source, and the load resistors are connected to a common current sink potential. In each case (ie, with respect to each one of the consumer networks), the working potential is a source potential of the power transistor and connected to an emitter of the control transistor, the control electrode of a power network associated with a power transistor is connected to the collector of another consumer network associated control transistor is Control resistor connected to the collector of the control transistor, the control reference potential connected via a scaling resistor to the main supply potential and the control diode is connected so that their flow direction points to the reference working potential. Furthermore, the zener diode is connected so that its direction of flow points from the current sink potential to the control reference potential.

If the control transistor is a pnp transistor, the load resistors are connected to a common main supply potential supplied by the power source, and the load networks are provided on the side of a common sink current potential. In each case (ie, with respect to each one of the consumer networks), the working potential is a drain potential of the power transistor and connected to a collector of the control transistor, the control electrode of a power network associated with a power transistor is connected to the emitter of another consumer network associated control transistor is Control resistor connected to the emitter of the control transistor, the control reference potential is connected via a scaling resistor to the current sink potential, and the control diode is connected so that its flow direction points away from the reference working potential. Further, the Zener diode is connected so that its flow direction is from the main supply potential to the control reference potential. In a further development, a compensation capacitor is connected in parallel with the compensation resistor. The dimensioning of the compensation capacitor can be used to optimize the dynamic behavior of the current control circuit.

Preferably, the power source is a DC power source. Alternatively, the power source may be a pulsed power source.

In a preferred embodiment, the load resistors are fixed resistors. By dimensioning the load resistors, the current sharing ratio can be set. In an alternative embodiment, the working resistors are adjustable resistors (i.e., potentiometers). As a result, an adjustment of the current division ratio is possible.

The working resistors thus have in particular a resistance ratio to one another, which may be selected according to the predetermined current division ratio.

The predetermined current dividing ratio may optionally be a uniform or an uneven current dividing ratio.

Preferably, the supply voltage, which results from a difference between the main supply potential and the current sink potential, is less than or equal to a predetermined limit value. The predetermined limit value may be, for example, 48 V, which facilitates the approval of a device equipped with the circuit. Depending on the legal or voluntary industrial specifications, the given limit may also be chosen differently in other or changed legislatures and / or technical contexts.

According to another aspect of the present invention, there is also provided a circuit arrangement having a plurality of parallel load networks, each of which in particular has a plurality of light emitting diodes in series, and a current control circuit for distributing a current from a common power source to the plurality of parallel power supply networks provided with a predetermined current division ratio. According to the invention, the current control circuit is constructed as described above.

In a preferred embodiment, the consumer networks are identical, constructed in particular with an identical number of LEDs of identical type. Other objects, features, features and advantages of the present invention will become more apparent from the description of preferred embodiments illustrated in the accompanying drawings.

1 shows a circuit arrangement with a current control circuit according to a first exemplary embodiment of the present invention.

Fig. 2 shows a circuit arrangement with a current control circuit according to a second embodiment of the present invention. Fig. 3 shows a circuit arrangement with a current control circuit according to a third embodiment of the present invention.

The figures are schematic circuit diagrams in the usual symbolic representation of the circuit elements. In the figures, for the sake of clarity, reference numerals may have an alphabetic prefix depending on the type of the designated circuit element or the designated physical quantity. In the circuit arrangements shown, a prefix C denotes a capacitor, a prefix D denotes a diode, a prefix P denotes a current source, a prefix R denotes an ohmic resistor, a prefix T denotes a transistor, a prefix U denotes an electrical voltage and a prefix V denotes an electrical potential. The counting of the circuit elements or physical quantities with a specific prefix, that is to say within a specific group of circuit elements or physical quantities, is functional in nature and should not be an indication of the number of circuit elements in the circuit arrangement. Unlike a conventional representation in circuit diagrams, in which each individual circuit element has its own counter, in the present figures, all circuit elements have the same or similar function on the same counter. It is possible, if appropriate, to prefer, but not in any case necessarily, that circuit elements with the same counter have the same typing and / or dimensioning. It should also be noted that physical quantities, which are given the same reference number in the figures, may be variable and may, but do not always have to, assume different values at different points in the circuit arrangement.

To simplify the description and the understanding, it is assumed here that all conductor sections of the illustrated circuit arrangements are comparatively short and at least essentially free of potential losses. Thus, a conductor portion extending between two or more circuit elements can be addressed by being assumed to be constant potential. So if, for example, described below, If a switching element is connected to a certain potential, this can be read so that the circuit element is connected to that conductor section which is addressed by the specific potential.

1 shows a circuit arrangement 100 with a current control circuit 30 according to a first exemplary embodiment of the present invention.

As shown in FIG. 1, in the circuit arrangement 100, a supply circuit 10 (dash-dotted line in the figure), two parallel current branches 20 which are supplied with power by the supply circuit 10, and a current control circuit 30 (indicated by dot-dashed lines in the figure) are provided ,

The supply circuit 10 has a current source P1 whose negative pole is connected to a zero potential V0 and whose output potential is fed via a series resistor R1 to a main supply potential V1, which is common to all current branches 20 and the current control circuit 30.

Each branch 20 branches off from the main supply potential V1 and in each case has a consumer network 40 (dash-dotted line in the figure). Each consumer network 40 has a plurality of light-emitting diodes D1 connected in series. It should be noted that the power supply networks 40 may be arranged on a same board as the remaining parts of the circuit arrangement or may alternatively be provided externally and integrated into the circuit arrangement 100 by means of connection terminals 60 or the like. At each of the light-emitting diodes D1 of the consumer networks 40, a voltage drop U1 takes place, so that in each case a consumer potential V2 prevails at an output of the consumer networks 40.

Since the individual voltage drops U1 may be different due to the non-linearity of the LEDs D1 described above, experience shows that each consumer potential V2 will adjust in each current branch 20, which is why the currents I in the consumer networks 40 may be different without active current control. The current control circuit 30 serves to control the supply currents I divided into the current branches 20 from the main supply potential V1 with a predetermined, here uniform, current division ratio. The current control circuit 30 has two control branches 50, each of which is assigned to one of the current branches 20 and has both circuit elements in the respectively assigned current branch 20 and circuit elements outside the respective associated current branch 20. Thus, a power transistor T1 and a load resistance R2, which are connected downstream of the load network 40 in series in the order given in the respective branch 20, essential components of the current control circuit 30. The power transistor T1 is a self-locking field effect transistor, more specifically a self-locking MOS-FET but the scope of the invention is not limited to this particular case. The power transistor (MOSFET) T1 thus has a source s and a drain d as main electrodes and a gate g as a control electrode. In each case, the drain d of the respective power transistor T1 is connected to the downstream end of the respective consumer network 40 and is thus at the consumer potential V2. The source s of the power transistor T1 is connected to one side of the respective load resistor R2 and thus defines a working potential V3 for the load resistor R2. The other end of the load resistor R2 is connected to a common for all branches 20 sink potential V4. The current sink potential V4 in the present exemplary embodiment is identical to the zero potential V0 of the current source P1, but can in principle be any potential that is a suitable sink for the supply current (ie with respect to the main supply potential V1 taking into account the loads that occur). As will be described in more detail below, a voltage drop U2 occurring across the load resistor R2 is an essential variable for controlling the partial currents in the current branches 20.

The current control circuit 30 also branches from the main supply potential V1 and initially has a scaling resistor R3 to scale the main supply potential V1 to a relatively lower main control potential V6, from which each control branch 50 is supplied. The control main potential V6 is also connected via a Zener diode D3 connected in the blocking direction to the common current sink potential V4. In other words, this also means that the low-side sides of the load resistors R2 of the current branch 20 are connected via the Zener diode D3 to the common control main potential V6 of the control branches 50. Each control branch 50 is connected via a control resistor R4 to the control main potential V6. Downstream of the control resistor R4, a control transistor T2 is provided. The control transistor T2 is in the present embodiment, a bipolar transistor (BPT), more specifically, an npn transistor. In other words, the control transistor T2 has a collector c and an emitter e as main electrodes and a base b as a control electrode. The collector c of the control transistor T2 is connected to the control resistor R4, and the emitter of the control transistor T2 is connected to the working potential V3 of the respective current branch 20. Via the emitter e of the control transistor T2, the working voltage U2 is tapped as a voltage drop across the load resistor R2, since this voltage drop corresponds to the difference between the working potential V3 and the common current sink potential V4. This is important for the current control since the voltage drop across the armature Beitswiderstand R2, thus the working voltage U2 and thus the working potential V3, proportional to the current flowing in the respective branch 20 current I is.

The bases b of the control transistors T2 of the two control branches 50 are connected together and thus have a common base potential V7, via which they are supplied with power. For this purpose, the collector sides c of all control branches 50 are connected via a respective control diode D2 to a common control main potential V8, which in turn is connected to the common base potential V7 via a parallel connection of a balancing capacitor C1 and a balancing resistor R5. The current control circuit 30 is completed by the collector side c of the control transistor T2 of the control branch 50 assigned to a current branch 20 being connected to the gate g of the power transistor T1 of the respective other current branch 20.

As an exemplary compilation of circuit elements, the following types and dimensions can be specified:

3 pF,

LXK 2 - PW 14 (default LED type)

1 N914 (alternatively: 1/2 BAW 56),

Zener diode 15 V / 0.5 W (DFLZ33),

PULSE (0 mA - 2000 mA for 1 με - 1 με or 1 με - 20 με or 140 με -1 s)

0.001 Ω

1 Ω,

1kQ,

10 kQ,

50 kQ,

PMV 31 XN

BC547B (alternatively: BCM e 847 DS)

The characteristics of the typifications given can be found in the relevant data sheets of the manufacturers and are therefore not explained in detail here.

The automatic control of the currents I of the current branches 20 takes place with the circuit arrangement described above as follows. As described above, the working potential V3 of each current branch 20 is tapped by means of an emitter circuit with the two control transistors T2. The two control transistors are supplied with the same base potential V7. Depending on the voltage drops U2 on the load resistors R2, so ultimately in response to the work potentials V3, a base current distributed over the control transistors T2.

Since the collector sides of the control transistors T2 are connected to the gate of a power transistor T1 of the other current branch 20, an increase of the working potential V3 of a branch 20 via the respective control transistor T2 is amplified, whereby the current flow in the other branch 20 is increased.

With this cross-coupling of the current I is tapped in one of the current branches 20 as working potential V3, amplified and used to control the flow of current in the other branch 20 current.

The "amplification" takes place by reducing the potential difference (V7-V3) between the base and the emitter at the control transistor T2 when the working potential V3 is increased, so that the electrical resistance of the transistor T2 between the collector side c and the emitter side e This also increases the voltage drop between the collector side c and the emitter side E. This additional voltage drop adds to the increased working potential V3 and forms the gate potential V5, with which the power transistor T1 of the respective other current branch 20 is driven In the present exemplary embodiment, since the two resistors R2 of the two current branches are identical, the two currents in the two current branches 20 are regulated to the same value Currents becomes in proportion of the two contradictions R2 is set. By varying the two resistors R2, the ratio of the currents in the two current branches can be changed accordingly. Basically, you can also form one or both resistors R2 by a potentiometer, so that the current ratio is freely adjustable.

It should be noted that when the gate potential V5 of a power transistor T1 has increased over a certain range, it is difficult to counterbalance and rebalance.

Therefore, the gate potential V5 of the power transistors T1 is respectively set to the reference working potential V8 by means of the control diodes D2, the reference working potential V8 corresponding to the respective higher of the two amplified working potentials V3 which form the gate potentials V5 of the power transistor T1. About the compensation resistor R5 is a base current for the control transistors T2 generated from the control main potential V8 out. This has the effect that the larger the main control potential V8, the larger the base current at the control transistors T2 and the more these transistors T2 conduct. As a result, more voltage drops at the upstream control resistors R4. The control resistors R4 are preferably set so that the gate voltage across the power transistors T1 can not exceed a predetermined threshold, which in the present case is about 1V.

In the control branch 50, the voltage through the zener diode D3 is limited to an appropriate value of about about 33V. As a result, a constant behavior of the circuit is ensured independently of the potential difference V1 -V4 and thus independent of the total current of the current source PI.

As shown in FIG. 1, one of the consumer networks 40 (in FIG. 1 the right-hand consumer network 40) has one light-emitting diode D1 more than the other consumer network 40. The additional light-emitting diode D1 is offset from the remaining light-emitting diodes D1 by a further connection terminal 60. Of the two terminals 60, which clip the additional light-emitting diode D1, each branches off a stub, which leads to a respective further terminal 60, via which the additional light-emitting diode D1 can be bridged. The additional light-emitting diode D1 can, for example, be used for checking the current flow or, for example, by adding or bridging the additional light-emitting diode D1, for testing the control circuit.

The circuit concept separates the power control with the power transistors T1 from the regulation of the current, which is realized with a control transistor pair T2, T2. As a result, a high control gain is realized, which has a very precise current division / mirroring result. The control transistor pair T2, T2 operates with coupled bases as differential amplifiers. The amplified current difference, which is tapped as a voltage by means of the emitter e via the load resistors R2, is then applied via the collector outputs c to the gates g of the power transistors T1. The power transistors T1 were taken over in the actual implementation as a self-blocking MOSFETs of an existing LED circuit. These are so-called "digital power transistors", which are to be brought through a small gate voltage range from blocking to turn on (high gain of the gate voltage on the MOSFET on-resistance).

A special feature of the present invention lies in the definition of the Referenzarbeitspotenti- as V8 (also referred to as a reference operating point), since the supply voltage varies in the application over a wide range in order to dim the LED strands can. The reference Operating point is stabilized to obtain a high control gain. The working point stabilization is achieved by two measures:

1 . Extracting a constant voltage V3 by means of the zener diode D3

2. Feedback of the collector voltages to the base of the NPN pair T2, T2 by means of the diodes D2, D2.

It is understood that the skilled person will be able to suitably adapt the circuit arrangement according to the type and number of LEDs used (default D1) and to select suitable circuit elements.

FIG. 2 shows a circuit arrangement 200 having a current control circuit 30 according to a second exemplary embodiment of the present invention.

As shown in FIG. 2, in the circuit arrangement 200, there are provided a supply circuit 10, four parallel current branches 20 which are supplied with power by the supply circuit 10, and a current control circuit 30.

Unlike the circuit arrangement 100 of the first exemplary embodiment, the current control circuit 30 does not have two, but four control branches 50, corresponding to the number of current branches 20 to be supplied and controlled. Otherwise, the structure and the connection of each of the circuit parts 10, 20, 30, 40, 50 analogously apply to what was said for the preceding embodiment, so that a renewed description is omitted to avoid repetition. For reasons of clarity, FIG. 2 omits a re-drawing of the circuit parts 10, 30, 40.

For clarity, it should be noted that all the current branches 20 as well as the current control circuit 30 branch off from the main supply potential V1 supplied by the supply circuit 10, all control branches 50 branch off from the potential V6 supplied by the scaling resistor 50, the bases of all four control transistors T2 to the common base potential V7 lead and the gate of the power transistor T1 of each current branch 20 with the collector of the control transistor T2 are connected to exactly one another branch 20 associated control branch 50.

In other words, in this embodiment, four consumer networks 40 are provided, in each of which a plurality of light-emitting diodes D1 are arranged. The individual power branches 20 with respective consumer network 40 are via a respective associated control branch 50 of Current control circuit 30 coupled in a circular manner. Otherwise, this circuit arrangement 200 works in the same way as with two current branches 20.

The more current branches 20 are present, the more difficult and sensitive is a stable current control. Simulations have shown that with the circuit concept according to the invention, the currents in three or four current branches can be well controlled.

3 shows a circuit arrangement 300 with a current control circuit according to a third exemplary embodiment of the present invention. The circuit arrangement 300 shown in FIG. 3 of this embodiment is functionally equivalent to the circuit arrangement 100 of the first exemplary embodiment shown in FIG. 1, with the difference that instead of an NPN transistor, a PNP transistor is used as the control transistor T2 and, instead of the NMOS power transistor, a PMOS transistor. Power transistor T1 can be used. This principle difference requires a reversal of the circuit structure, that is, the order of the circuit elements. Thus, in each branch 20 of the working resistance R2 is at the main supply potential V1, followed by the self-blocking power transistor T1 with source s and then at the drain d the consumer network 40, which finally falls to the current sink potential V4. The working potential V3 is tapped at the drain d of the power transistor T1 and is located at the collector c of the control transistor (PNP transistor) T2, whose emitter e falls via the control resistor R3 to the common control main potential V6. The scaling resistor R3 carries the common control main potential V6 to the current sink potential V4. The control diode D2 leads from the common reference working potential V7 to the emitter side e of the respective control transistor T2, and the gate g of the power transistor T1 is also on the emitter side e of the control transistor T2 of the other current branch 20. The zener diode has from the main supply potential V1 to the control main potential V6.

In other words, unlike the case of control by npn transistors, the working potential V3 of each current branch 20 is tapped here by means of a collector circuit with the two control transistors (pnp transistors) T2. The two control transistors are supplied with the same base potential V7. Depending on the voltage drops U2 on the load resistors R2, so ultimately in response to the work potentials V3, a base current distributed over the control transistors T2. Thus, the current control circuit 30 operates in principle as well as in the first embodiment, only in the reverse arrangement direction. A detailed description of the functional Theory is therefore omitted to avoid repetition, instead, reference is made to the description of the first embodiment, which is analogous to apply. It should also be noted that the working voltage U2 here results as the difference between the main supply potential V1 and the working potential V3, which is obtained here as the source potential of the power transistor T1.

The circuit arrangements 100, 200, 300 are basically provided for the DC operation. Simulations have shown that they can also be operated pulsed. The circuits show good dynamic behavior.

With different load resistors R2 different power distributions in the individual power branches 20 can be adjusted. The load resistors R2 can also be embodied by potentiometers, so that the current flow in individual current branches 20 can be set individually by hand. The circuit concept described above was first simulated in a circuit simulation software (LTSpice), then implemented and tested. The simulations cover unequal current conditions, as well as extension to several branches. The implementation was carried out for equal current ratios and two branches. The circuit was tested both in simulation and in practice by bridging a single LED D1 times in one, sometimes in the other current branch 20. The resulting asymmetry of the total flux voltages of the LED strings would lead to very different currents in the two current branches 20 without the current control circuit 30 according to the invention. Table 1 below shows, by means of a measurement protocol, the effect of the current control circuit 30 according to the invention according to the first embodiment, which is shown in FIG. 1 and explained above.

Total current l (R1) [mA] 200 600 1000 1400 1800 symmetrical (no LED bridged)

Supply voltage V1 -V4 [V] 30,86 34,40 36,10 37,30 38,20

Working current left branch I (R2) [mA] 102.3 303 504 705 907

Working current right branch I (R2) [mA] 101, 9 303 504 705 907

Loss voltage left branch V2-V3 [V] 0.047 0.055 0.1 14 0.213 0.440

Loss voltage right branch V2-V3 [V] 0,017 0,055 0,076 0,193 0,389 asymmetrical (one LED bridged)

Supply voltage V1 -V4 [V] 30,86 34,40 36,10 37,30 38,20

Working current left branch l (R2) [mA] 103.0 304 505 706 908

Operating current right branch I (R2) [mA] 102.0 303 504 705 907

Loss voltage left branch V2-V3 [V] 2,836 2,974 3,103 3,242 3,388

Loss voltage right branch V2-V3 [V] 0.017 0.055 0.104 0.153 0.209

Table 1: Measurement results at the circuit realization

From Table 1 it can be seen that the current control circuit 30 compensates for almost 100% of the asymmetry provoked by bridges of an LED, this is a very reliable estimate of the reliability of the current control, because in practical application it is more a matter of compensating for different forward flux voltages Light-emitting diodes D1, which in total have far less drastic effects than the bridging of a light-emitting diode D1.

While the above embodiments and the simulations and test circuits are designed to be split 1: 1, the application of the present invention is not limited to the same current ratio distribution. For division into unequal currents, only the ratio of the working resistors R2 must be selected accordingly. One can also vary this ratio by means of different control resistors R4. The capacitor C1 can be chosen to optimize the dynamic characteristics in the practical circuit.

With the circuit arrangements 100, 200, 300 described above with reference to a plurality of embodiments or the current control circuit 30 provided there, it was possible according to the simulation and test results

- an automatic power split; - an improvement in accuracy (<5% deviation);

an improvement of the robustness against current intensity and circuit element tolerances;

- a good dynamic behavior when switching on and off, as well as in pulse mode;

a simple structure by a small number of circuit elements;

- The possibility of recycling the same LED chain structure as in the previous lighting, as well as a recycling of the same power transistors;

- High efficiency due to low power loss of the control circuit

be achieved. The circuit furthermore has the advantage that it can also be adapted over a wide range of unequal current division ratios, and can be extended to a plurality (ie two or more) LED chain branches.

The exemplary embodiments explained above have a current source P1, which generates current pulses with a different duration (1 με -1 s) and with different current strength (0.1 nA-2A). The invention can also be operated with a current or voltage source with a constant output voltage or with a constant current signal.

Even short pulses can be safely and reliably controlled in the desired ratio with the current control circuit according to the invention. The current control circuit according to the invention thus shows a very fast response.

In the embodiments explained above, the power transistors T1 are designed as self-locking field-effect transistors. Self-conducting transistors can also be used in the context of the invention, wherein the potential V4 applied to the gate electrode should then be correspondingly inverted. In the case of normally-isolated field-effect transistors, it may be expedient first to apply a blocking potential to these when the entire current control circuit is switched on, before the regulation by the current control circuit becomes effective.

The present invention has been described in terms of several embodiments which describe the distribution of a supply current to two or more parallel current branches 20 with respective consumer networks 40, each of the consumer networks 40 being constructed, for example, as an LED array having a plurality of light emitting diodes D1 connected in series , However, the current control circuit 30 described is also applicable to other types of consumer networks 40 connected in parallel, in which the most exact possible compliance with a specific current division ratio is desired or required. Non-linear consumers can be used and yet a predetermined distribution is achieved. In the case of more than two current branches 20, it is also conceivable to choose a nested arrangement in which two or three current branches are combined and controlled in parallel and a plurality of such parallel circuits are combined and controlled to form an overall parallel circuit, instead of connecting and connecting all current branches 20 in parallel In other words, each of the parallel circuits is understood as a consumer network. In this way, a two- or multi-stage control can be made, although may require a more complex circuit structure and more circuit elements, but may have control advantages. In the context of this application, the term control is used throughout. In the context of this application, this term does not differentiate between a simple feed-forward control and a control with feedback of the control variable.

It should also be pointed out that the qualitative designation of circuit elements such as resistors as ballast resistor, load resistor, scaling resistor, control resistor, compensation resistor, diodes as control diodes, capacitors as balancing capacitors, transistors as control or power transistors only the functional assignment within the Circuit arrangements are used and no limitation in the design, typing and dimensioning of these circuit elements must mean, unless this is explicitly mentioned in the context.

List of reference signs and symbols

10 supply circuit R1 ballast resistor

20 current branch R2 working resistance

30 Current control circuit R3 Scaling resistor

40 consumer network R4 control resistor

50 Control branch R5 compensation resistance

60 connection terminal

100 circuit arrangement T1 power transistor (Feldeffekttran¬

200 circuit arrangement sistor, in particular MOSFET)

300 circuit arrangement T2 control transistor (bipolar transistor, npn or pnp)

b base

c collector U1 voltage drop across a LED d drain U2 working voltage (voltage drop e emitter via working resistor R2)

g gate

s Source of zero potential

V1 main supply potential

C1 equalizing capacitor V2 consumer potential

V3 work potential

D1 LED (LED) V4 Current sink potential

D2 control diode V5 gate potential

D3 Zener diode V6 control main potential

V7 base potential

P1 current source V8 reference working potential

Claims

claims

1 . A current control circuit (30) for distributing a current from a common power source (P1) to a plurality of parallel load networks (40) at a predetermined current split ratio,

wherein the power control circuit (30) for each of the power networks (40) comprises:

a power transistor (T1), in particular field effect transistor, preferably MOSFET, in series with the consumer network (40;

a load resistor (R2) in series with the power transistor (T1) on its side remote from the load network (40), a working potential (V3) being defined between the load resistor (R2) and the power transistor (T1);

a control resistor (R4) having one side connected to a control reference potential (V6) common to the entire current control circuit (30);

a control transistor (T2), in particular a bipolar transistor, which is connected in a current path formed between the working potential (V3) and the other side of the control resistor (R4) remote from the control reference potential (V6), the control electrode, in particular base (b), the control transistor (T2) is connected to the control electrodes, in particular bases, of the control transistors (T2) of all other consumer networks (40) to form a common base potential (V7) common to all the control transistors (T2) connected to the current paths between the control transistor (T2) and the control resistor (R4) is coupled;

and wherein a control electrode of the power transistor (T1) is connected to the current path between the control transistor (T2) and the control resistor (R2) provided for exactly another one of the power networks (40).

Second current control circuit (30) according to claim 1, characterized in that the coupling of the common base potential (V7) from each by means of a control diode (D2) between the current path between the control transistor (T2) and the control resistor (R2) and the base potential (V7) is trained.

3. Current control circuit (30) according to claim 2, characterized in that the control electrodes (D2) of all current branches are connected to each other and form a reference working potential (V8) which is connected by means of a compensation resistor (R5) to the base potential (V7).

4. Current control circuit (30) according to any one of claims 1 to 3, characterized in that the current control circuit (30) comprises a Zener diode (D3) connected between the control reference potential (V6) and one of the interconnected, from the respective power transistor (T1 ) opposite sides of the load resistors (R2) defined potential is connected.

5. Current control circuit (30) according to claim 3 or 4, characterized in that the control transistor (T2) is an npn transistor, wherein

the consumer networks (40) are provided on the side of a common main supply potential (V1) supplied by the current source (P1),

the load resistors (R2) are connected to a common current sink potential (V4),

with respect to each of the consumer networks (40)

the working potential (V3) is a source potential of the power transistor (T1) and connected to an emitter (e) of the control transistor (T2),

the control electrode of the power transistor (T1) associated with a consumer network (40) is connected to the collector (c) of the control transistor (T2) associated with another consumer network (40),

the control resistor (R2) is connected to the collector (c) of the control transistor (T2),

the control reference potential (V6) is connected to the main supply potential (V1) via a scaling resistor (R3), and

the flow direction of the control diode (D2) to the reference working potential

(V8) indicates

and wherein the flow direction of the Zener diode (D3) points from the current sink potential (V4) to the control reference potential (V6).

6. Current control circuit (30) according to claim 3 or 4, characterized in that the control transistor (T2) is a pnp transistor, wherein

the working resistors (R2) are connected to a common main supply potential (V1) supplied by the current source (P1),

the consumer network (40) are provided on the side of a common current sink potential (V4),

with respect to each of the consumer networks (40)

the working potential (V3) is a drain potential of the power transistor (T1) and connected to a collector (c) of the control transistor (T2), the control electrode of the power transistor (T1) associated with a consumer network (40) is connected to the emitter (e) of the control transistor (T2) associated with another consumer network (40),

the control resistor (R2) is connected to the emitter (e) of the control transistor (T2),

the control reference potential (V6) is connected to the current sink potential (V4) via a scaling resistor (R3), and

the direction of flow of the control diode (D2) points away from the reference working potential (V8),

and wherein the flow direction of the Zener diode (D3) points from the main supply potential (V1) to the control reference potential (V6).

7. Current control circuit (30) according to one of the preceding claims, characterized in that the compensation resistor (R5), a balancing capacitor (C1) is connected in parallel.

8. Current control circuit (30) according to one of the preceding claims, characterized in that the current source (P1) is a DC power source.

9. Current control circuit (30) according to one of claims 1 to 7, characterized in that the current source (P1) is a pulsed current source (P1).

10. Current control circuit (30) according to one of the preceding claims, characterized in that the working resistors (R2) are fixed resistors.

1 1. Current control circuit (30) according to one of claims 1 to 9, characterized in that the working resistors (R2) are adjustable resistors.

12. Current control circuit (30) according to any one of the preceding claims, characterized in that the working resistances (R2) have a resistance ratio to each other, which is selected according to the predetermined current division ratio.

The current control circuit (30) according to one of the preceding claims, characterized in that the predetermined current dividing ratio is a uniform current dividing ratio.

14. Current control circuit (30) according to any one of claims 1 to 12, characterized in that the predetermined current division ratio is an uneven current division ratio.

15. Current control circuit (30) according to one of the preceding claims, characterized in that a supply voltage, which results from a difference between the main supply potential (V1) and the current sink potential (V4) is less than or equal to a predetermined limit, wherein the predetermined Limit is 48 V in particular.

A circuit arrangement (100, 200, 300) comprising a plurality of parallel load networks (40), each having a plurality of light emitting diodes (D1) connected in series, and a current control circuit (30) for distributing a current from a common power source (P1) to said plurality of parallel consumer networks (40) at a predetermined current division ratio, said current control circuit (30) being constructed according to one of the preceding claims.

17. Circuit arrangement (100; 200; 300) according to claim 16, characterized in that the consumer networks (40) are constructed identically, in particular with an identical number of light emitting diodes (D1) of identical type.

18. Circuit arrangement (100, 200, 300) according to one of the preceding claims, characterized in that each of the consumer networks has a non-linear consumer, in particular a light-emitting diode.

19. Current control circuit according to one of the preceding claims, characterized in that the consumer networks (40) each have a plurality of series connected light emitting diodes (D1).