EP2656687B1 - Driving apparatus for led - Google Patents

Description

The invention relates to an LED operating arrangement for operating a plurality of serially connected LED arrangements, according to the preamble of claim 1. The invention further relates to a method for operating such an LED operating arrangement.

An LED operating arrangement is particularly suitable for supply with changing supply voltage, for example when supplied via a commercial AC source. Such an LED operating arrangement is for example in the published patent application DE 10 2007 041 131 A1 described. In this case, for each of the bypass arrangements, the applied supply voltage is compared with predetermined threshold values and, depending on the result, the respective bypass arrangement is controlled for bridging the associated LED arrangement or for blocking. As the supply voltage increases, the series-connected LED arrangements are thus successively switched on, so that a comparatively efficient conversion of the electrical energy into light radiation is achieved.

However, it should be noted that the electronic components for determining the respective reference voltages as well as the LEDs used production variations their electronic properties are subjected, for example in the case of the LEDs with respect to the respective forward voltage, the temperature behavior and / or the change of these quantities with the aging of the device. For this reason, security areas must be provided in the design of such circuits with respect to these characteristics, which is associated with additional power losses in the circuit, which ultimately the efficiency is limited.

The publication DE 198 41 490 A1 relates to a circuit arrangement for protecting a series circuit of multiple LEDs before failure. For this purpose, the LEDs are each a bypass device in the form of a Zener diode connected in anti-parallel, with an increased voltage drop at one of the Zener diodes indicates the failure of the associated LED and can be operated by bridging the defective LED, the LED series circuit.

The publication US 2004/0233145 A1 relates to an LED drive circuit having a plurality of LEDs arranged in series, a voltage detection circuit for detecting a rectified supply voltage and a plurality of current control units. The current control units are controlled by the voltage detection circuit as a function of the level of the supply voltage for reconfiguration of the LED series arrangement.

The publication US 2009/0230883 A1 relates to a generic LED operating arrangement for operating a plurality of serially connected LED arrays, wherein the LED arrays each have a first and a second terminal, the series circuit of the LED arrays is connected to a supply voltage, and wherein at least some of the plurality of LED assemblies each designed as a controllable resistor bypass arrangement is associated such that in each case a bypass terminal of the bypass arrangement is connected to a terminal of the associated LED array, and the respective bypass arrangement further comprises at least one control terminal and bridges the associated LED arrangement in an operating state, wherein the at least one control terminal the respective bypass arrangement is connected to an output of an associated current sensor.

The invention has for its object to improve the efficiency of the known LED operating arrangements.

This object is achieved by the present invention device-side already with an LED operating arrangement with the features of claim 1. The LED operating arrangement according to the invention is characterized in that the respective bypass arrangement as controllable resistance by the output signal of the associated current sensor in intermediate states between the first and the Further operating state is controlled to control the current flowing through the respective bypass means current, and that the respective bypass assembly associated current sensor for detecting a current flow through an LED array is formed, which in the series circuit of the LED devices downstream and in the series circuit of the LED Arranged sequentially to the LED array, which is associated with the respective bypass arrangement, so that the current detected by the associated current sensor of the respective bypass arrangement composed of the current through the respective Bypassan order flowing current and the current flowing through the respective LED array, which is associated with the respective bypass arrangement.

The assignment of a bypass arrangement to an LED arrangement makes it possible that the respective LED arrangement can be bridged by the associated bypass arrangement, insofar are connections or inputs and outputs of the bypass arrangement parallel to the associated LED array or parallel to a series circuit which at least the associated LED array, but possibly also includes other components such as an associated current sensor for the bypass arrangement. As used herein, the term "adjacent" refers to two consecutive LED arrays in series with respect to two LED arrays, regardless of whether there are other components such as a current sensor or a current or voltage source in series between these two LED arrays of LED arrays are arranged. The adjacent two LED arrays may, for example, be arranged downstream of one another downstream of the series circuit.

In general, in the case of the LED operating arrangement according to the invention, the respective bypass arrangements are designed as controllable resistors in such a way that, in addition to the states a), conductive, i. bridging the associated LED array and b) blocking, i. the respective assigned LED arrangement not bridging also other intermediate states are adjustable in operation, such that e.g. can assemble a total current through an LED array by a portion of current flowing through an adjacent LED array and a portion of current flowing through a bypass array associated with the adjacent LED array.

An LED arrangement may comprise a single LED, but also a plurality of LEDs, in particular in a series connection. Furthermore, the term LED or light-emitting diode is here understood very broadly and generally includes light-emitting electronic components, in particular organic LEDs.

Characterized in that in the LED operating arrangement according to the invention, a current control of the respective bypass arrangement means a respective current sensor is realized, manufacturing differences of electrical properties of the components, in particular the respective LEDs, such as forward voltage, temperature behavior and change of these parameters can be automatically taken into account by aging during operation. The safety designs described above for generic LED operating arrangements are unnecessary, so that ultimately the efficiency of the LED operating arrangement according to the invention can be further improved compared to the conventional arrangements. Moreover, in the case of the LED operating arrangement according to the invention, it is not absolutely necessary to use LEDs with as identical electronic characteristics as possible, since the circuit automatically adapts to the specific properties of the respective LED or LED arrangement. In addition, it can be achieved with the invention that the harmonic content of the current flowing through the series arrangement of the LED arrays is reduced.

In order to effectively provide this automatic adaptation for the respective LED arrangement, several, preferably all, bypass arrangements suitably comprise their own current sensors assigned to them, so that, in particular, the attainment of the respective forward voltage of the associated LED arrangement can be determined.

At least several, preferably (n-1) of the n LED arrangements or also all of the n LED arrangements may be assigned a bypass arrangement as described above.

According to the invention, the current sensor, which is associated with the respective bypass arrangement, is designed to detect a current flow through an LED arrangement, which is arranged downstream downstream of the LED arrangement, which is associated with the respective bypass arrangement. By This design measure can be measured via the current sensor of the instantaneous current, which is passed through the bypass arrangement, as well as the current component, which flows through the bypass arrangement associated with the LED array, and used for the control of the bypass arrangement.

Preferably, the respective current sensor comprises a bypass arrangement. at least one resistor, in particular, the current sensor may be formed as a single resistor. The current to be detected is passed through the current sensor, the resulting voltage drop can be provided as a control signal, the associated bypass arrangement. The respective current sensor can also be designed as a resistor network, in particular as a parallel connection of resistors.

As already explained above, preferably several of the bypass arrangements associated current sensor are provided, which are expediently arranged in each case in series with the series-connected LED arrays. In this embodiment, therefore, resistors included in the current sensor and the LED arrays themselves are connected in a common series arrangement. It may be expedient if the respective current sensor, in particular the respective resistor arrangement, is provided in series between the two adjacent LED arrays.

Preferably, one terminal of the respective current sensor is connected to a control terminal of the associated bypass arrangement and another terminal of the respective current sensor is connected to a bypass terminal of the associated bypass arrangement.

Preferably, a bypass connection of a bypass arrangement can directly without an interconnection via other components with a first terminal of the associated LED array and another bypass terminal of the bypass arrangement may be connected via a current sensor to a second terminal of the associated LED arrangement, which current sensor may be arranged in a series connection of LED arrangements and current sensors. On the other hand, the first and second bypass connections of a bypass arrangement can each be directly connected without any interconnection via other components to a respective terminal of the associated LED arrangement.

First and second terminals of the associated LED array may be the two supply terminals of the LED arrays. The two bypass connections can represent the bypass input and the bypass output, wherein as explained between input and output of the bypass arrangement in addition to a short circuit and a complete blockage and intermediate states are adjustable, in particular those of a controllable resistor and / or a controllable current source.

One or more of the described by-pass arrangements may also include more than a single control input. In this case, multiple signals are used to control the bypass arrangements.

Particularly advantageously, at least one of the plurality of bypass arrangements comprises a normally-on transistor such as a FET, in particular, such a bypass arrangement may be designed essentially as a self-conducting transistor. In this case, however, it is also possible for a bypass arrangement to comprise a self-blocking transistor, in particular as a self-blocking transistor.

As far as resistors or resistors connected as a current sensor in the series together with the LED assemblies are provided, they can be dimensioned at an alternating supply voltage as in a sinusoidal AC voltage to adapt the supply current to this supply voltage, in particular to optimize the efficiency and harmonic content of the LED operating arrangement. The accuracy of such an adaptation generally increases with the number of LED arrays which are each assigned a bypass arrangement.

For example, it may be expedient if the resistances arranged in the series connection with the LED arrangements increase continuously in their resistance value in the direction of current flow.

Conveniently, the bypass arrangements may be connected in series, i. the input of a bypass arrangement is connected to an output of an adjacent bypass arrangement, wherein several, in particular all bypass arrangements can be connected in series in this way.

To protect the series-connected LED arrangements, a current limiting device can be provided which can be provided between the supply voltage terminals of the LED operating arrangement and in series with the series connection of the LED arrangements or within this series connection.

The LED operating arrangement expediently has an AC voltage-fed rectifier for providing a pulsating DC voltage supply with which the series connection of the LED arrangements can be fed. In particular, in such a pulsating DC power supply, the resistance values of the connected in series with the LED assemblies current sensors or resistors for adjusting the time profile of the flow through the series connection of the LED assemblies to the temporal Adjusted course of the pulsating DC voltage.

Advantageously, it can also be provided that one or more, in particular all, bypass arrangements have at least one further control terminal which scans the cathode voltage of the LED arrangement, which is arranged downstream of the associated LED arrangement of the bypass arrangement. Both control signals may e.g. be guided via respective series resistors in parallel to the gate of the respective transistor of the bypass arrangement. Characterized in that in addition to the output signal of the current sensor in this embodiment, a further signal that depends on the forward voltage of the downstream adjacent LED array, is used to control the bypass arrangement, can be a performance optimization for the last-mentioned LED array perform.

In terms of the method, the above-described problem is solved by the features of method claim 10. The inventive method is characterized in that the respective bypass arrangement is further controlled as controllable resistance by the output signal of the associated current sensor in intermediate states between the operating state of bridging the associated LED array and the operating state of not bypassing the respective bypass arrangement for controlling by the respective Bypasseinrichtung flowing current and that by means of the respective associated current sensor, the current is detected, which flows through the LED array, which is arranged in the series circuit of the LED devices downstream and in the series circuit of the LED arrays successively to the respective LED array, which is associated with the respective bypass arrangement, wherein the sum of the current flowing through the respective LED arrangement and the current supplied by this LED arrangement is supplied by the current detected by means of the respective associated current sensor ordered bypass arrangement flowing current is detected.

Conveniently, the method according to the invention can be set up in such a way that the instantaneous value of the current flowing through the respective LED arrangement is detected by the respective current sensor.

Depending on the operating state, an LED arrangement can be bridged by means of its associated bypass arrangement. The control of the bypass arrangement can take place by means of the detection of the instantaneous value of a current flow through an LED arrangement which follows in the series connection of the LED arrangements on the LED arrangement which is assigned to this bypass arrangement. The described control of a bypass arrangement takes place in several of the bypass arrangements included, in particular in all bypass arrangements, which are each associated with an LED arrangement.

In the method according to the invention, the sum of the current flowing through an LED arrangement and the current bridged by the bypass arrangement assigned to this LED arrangement is expediently detected by means of a respective current sensor, wherein the respective bypass arrangement is controlled by an output signal of this current sensor. As a result, it is achieved that the control of the respective bypass arrangement takes into account both the bridged current and the current flowing through the associated LED arrangement, and thus the achievement of the specific forward voltage at the respective LED arrangement is detected.

Conveniently, a bypass arrangement is operated as a controllable resistor with increasing supply voltage initially in the bridged state, in which the associated LED array is bridged, with increasing current flow through the downstream LED array of resistance the bypass arrangement is increased until a predetermined limit current is reached by the downstream LED array. By this measure it can be achieved that the timing of the self-adjusting current flow is adjusted by the series connection of the LED arrays to the timing of the supply voltage, so that the Efficiency can be optimized.

Conveniently, it may further be provided that after reaching the predetermined limit current through the respective bypass arrangement with further increasing supply voltage of the current flowing through the bypass means current is kept substantially constant and an increasing voltage at the bypass device drops until the specific forward voltage of the associated LED array is reached. This forward voltage represents the threshold voltage at which the LED array conducts. The resistance of the bypass arrangement is just controlled in this phase of operation insofar that the current flowing through the bypass device is approximately constant. Also by this method step, the time profile of the current flowing through the LED arrays current can be adjusted to the time course of the supply voltage to increase the efficiency.

Preferably, the resistance of the bypass arrangement is increased after reaching the specific forward voltage of the associated LED array with increasing supply voltage by an increasing current flow through this LED array, so that the current flow through the bypass arrangement is reduced.

The inventive method makes it possible that, adapted to the time profile of the supply voltage, the series-connected LED arrays, successively and adapted to the respective specific forward voltage by controlling the individual bypass arrangements, with current flowing through and thus contribute to light generation. This process takes place in the same way when the supply voltage drops, ie in this case the individual LED arrays are successively bridged by switching on the bypass arrangements.

Figur 1

eine erfindungsgemäß gestaltete LED-Betriebsanordnung in einer Prinzipskizze,

Figur 2

die in Figur 1 dargestellte LED-Betriebsanordnung detaillierter,

Figur 3a, b

den zeitlichen Verlauf verschiedener Spannungs- bzw. Stromgrößen innerhalb der LED-Anordnung gemäß. Figur 2,

Figur 4 a - f

den zeitlichen Verlauf der Einzelströme durch die jeweiligen LED-Anordnungen bei einer LED-Betriebsanordnung gemäß Fig. 2 mit sechs LED-Anordnungen,

Figur 5 a, b

den zeitlichen Verlauf der an LED-Betriebsanordnung gemäß Figur 2 mit sechs LED-Anordnungen anliegenden pulsierenden Gleichspannung mit dem sich ergebenden Gesamtstrom für eine Netzperiode,

Figur 6

eine weitere Ausführungsform einer erfindungsgemäßen LED-Betriebsanordnung,

Figur 7

eine weitere Ausführungsform einer erfindungsgemäß ausgebildeten LED-Betriebsanordnung,

Figur 8 a, b

den zeitlichen Verlauf verschiedener Stromund Spannungsgrößen innerhalb der LED-Betriebsanordnung gemäß Figur 7, und

Figur 9

im Vergleich den zeitlichen Verlauf des Gesamtstroms durch die LEDs über eine Netzperiode für die in den Figuren 2 und 7 dargestellten Ausführungsformen bei sechs in Reihe geschalteten LED-Anordnungen

zeigt.The invention will now be elucidated by describing some embodiments with reference to the accompanying drawings, in which: FIG

FIG. 1

an inventively designed LED operating arrangement in a schematic diagram,

FIG. 2

in the FIG. 1 illustrated LED operating arrangement in more detail,

FIG. 3a, b

the time course of different voltage or current quantities within the LED array according to. FIG. 2 .

Figure 4 a - f

the time course of the individual currents through the respective LED arrangements in an LED operating arrangement according to Fig. 2 with six LED arrangements,

FIG. 5 a, b

the time course of the LED operating arrangement according to FIG. 2 pulsating DC voltage applied to six LED arrays with the resulting total current for one mains period,

FIG. 6

a further embodiment of an LED operating arrangement according to the invention,

FIG. 7

a further embodiment of an inventively designed LED operating arrangement,

Figure 8 a, b

the time course of various current and voltage within the LED operating arrangement according to FIG. 7 , and

FIG. 9

In comparison, the time course of the total current through the LEDs over a network period for in the Figures 2 and 7 illustrated embodiments in six series-connected LED assemblies

shows.

FIG. 1 shows a schematic diagram of the basic structure of an LED operating arrangement according to the invention. This has two network connections, via which the arrangement 1 is supplied with an AC voltage, which is converted via a rectifier 10 into a pulsating DC voltage with the voltage VGL. This voltage is applied to a series circuit of n LED arrays, each having a specific forward voltage. Depending on the embodiment, these LED arrangements may comprise one or more LEDs, in particular a plurality of LEDs in a row arrangement. Although not limited thereto, it is assumed in the following that the n LED arrangements have the same structure, but in particular have slightly different forward voltages due to the unavoidable production variations, ie that they transition into the conducting state at slightly different voltages.

In the series connection of the LED arrangements, a current limiter 110 is also provided, which limits the total current through the circuit. Starting from ground, the second LED arrangement LED2 and each further upstream LED arrangement up to the last arrangement LEDn has an associated bypass arrangement 20a to 20 (n-1) which, depending on the operating situation, bridges the associated LED arrangement. For this purpose, the respective bypass arrangement 20i, i = a ..... (n-1) two terminals A1, A2 and a control terminal S on. For clarity of illustration, these connections are solely for the by-pass arrangement 20a in FIG FIG. 1 specified. The Bypass arrangement 20a is associated with the LED2, ie, depending on the operating situation, the bypass arrangement 20a bridges the LED arrangement LED2. For this purpose, a terminal A1 is connected via the current sensor 100b to the anode of the LED array LED2, the terminal A2 is coupled directly to the cathode of the LED array LED2.

In the described embodiment, a current sensor 100a to 100 (n-1) is provided between each two LED arrays, these current sensors are thus also in series with the serially connected LED arrays and together with them form a series circuit. The output of each current sensor 100a to 100 (n-1) is connected to the control input S of the respective bypass arrangement.

How out FIG. 1 can be seen, the respective current sensor detects a sum current, which is composed by the current through an LED array and the current flowing through the this arrangement associated with the LED bypass arrangement, that is bridged. The current sensor 100a measures, for example, the summation current which is composed by the current through the arrangement LED2 and the current of the bypass arrangement 20a bridged via the connections A1, A2. Thus, in the described embodiment, the current sensor 100a measures the current flowing through the downstream LED array, ie, the LED array LED1. This situation applies to all of the current sensors of the bypass arrangements used, for example, the current sensor 100b measures the total current, which is composed by the LED array LED3 and the current through the bypass arrangement 20b and which corresponds to the current through the downstream LED array LED2.

FIG. 2 shows the in FIG. 1 illustrated LED operating arrangement again, wherein both the bypass assemblies 20a - 20 (n-1) and the current limiting device in detail are shown. In the illustrated embodiment, the bypass arrangements 20a to 20 (n-1) comprise a self-conducting field effect transistor 21a to 21 (n-1), wherein a series resistor 22a to 22 (n-1) is respectively arranged between the gate of the respective transistor and the control input S. ,

The current sensors 100a to 100 (n-1) in the embodiment of FIG FIG. 2 designed as resistors, wherein at the control input S of the respective bypass arrangement, the voltage is applied, which drops at the associated current sensor, ie the resistor.

According to the invention, the bypass arrangements 20a to 20 (n-1) are not only driven to bridge the respective associated LED array or blocking, but depending on the operating situation, these bypass arrangements are generally used as a controllable resistor and / or controllable current source for setting intermediate values controlled so that a parallel connection to the respective associated LED arrangement is realized with adjustable resistance or adjustable the power source.

The functioning of the in the FIGS. 1 and 2 illustrated LED operating arrangements according to the invention will be described below with further reference to the FIGS. 3a, b . 4a to f and 5a, b explained. In the following, it is assumed that the series circuit has a total of six LED arrangements and correspondingly five bypass arrangements, each with associated current sensor.

It is first assumed that the applied pulsating DC voltage VGL passes through a zero crossing to positive voltage values. All self-conducting field effect transistors 21a to 21 (n-1) are first turned on, so that the rising voltage VGL neglecting the falling between the drain and source in the transistors Voltages at the anode of the current flow downstream last LED array LED 1 is applied. The FIGS. 3a, b show the time course of various current and voltage variables within the LED array according to FIG. 2 , FIG. 3a shows for a short time interval, the rise of the pulsating DC voltage VGL and the dependent thereon time course of the guided through the bypass arrangements 20a and 20b or .. bridged current I (21a) or I (21b). In the same time scale is in FIG. 3b the temporal course of the voltage applied to the control input S of the bypass device 20a and generated by the current sensor 100a control voltage VS (21a) and the time course of the currents I (LED1) and I (LED2) through the two LED arrays LED1 and LED2.

Since initially the rising, applied to the anode of the LED delegation LED1 rectified supply voltage VGL is smaller than the forward voltage of LED1, no load current flows, so far, the control voltage VS (21a) is identical zero, so that the .Transistor 21a first in the normally-off Condition remains. After about 0.5 ms, the rectified supply voltage reaches the forward voltage of the LED array LED1 of about 50 volts, LED1 conducts, and a current I (LED1) flows through the bypass arrangements 20 (n-1) to 20a, the current-sensing resistance sensor 100a, the diode array LED1 and the total current limiting device to ground, said total current limiting device is in turn formed by a normally-on FET 111 and a formed as a resistance current sensor 112. The voltage drop at the current sensor 100a generates a negative control voltage VS (21a) at the control input S, ie a negative gate-source voltage at the transistor 21a. When this voltage reaches the gate threshold voltage of the transistor 21a, the current flowing through the bypass arrangement 20a is limited to the ratio of the gate threshold voltage to the resistance value of the current sensor 100a. please refer FIGS. 3a , b. This current remains substantially constant in the example described in the time interval between about 0.5 ms to about 1.05 ms, the bypass arrangement 20a operates in this interval as a constant current source, so that between the two terminals A1, A2 of the bypass arrangement 20a, ie between the Drain-source terminals of the transistor 21 a, the difference between the forward voltage of the LED array LED 1 and the further increasing supply voltage VGL drops. Since in the described embodiment, the respective bypass arrangement of the series connection of the associated LED array and the upstream current sensor is connected in parallel, this voltage is also applied to the series connection of the formed as a resistance current sensor 100b and the LED array LED2. In the specified time interval between about 0.5 and about 1.05 ms, the current I (LED1) is kept constant.

As stated, the LED arrays LEDn to LED1 are constructed substantially identically, inasmuch as the upstream LED array LED 2 becomes conductive when the instantaneous value of the pulsating DC voltage VGL reaches about 100 volts. Then, the LED array LED 2 is also conductive and it flows a current through the designed as a resistor current sensor 100b. The voltage drop generated thereby at this leads to a negative control voltage at the bypass arrangement 20b, so that also in this the conducted or bridged current is limited. In the example given, the resistance of the current sensor 100b is significantly lower than the resistance of the current sensor 100a, so that the described connection of the transistor 21b and the current sensor 100b is now limited to a higher current. This current through the LED array LED2 is now added to the current which is passed through the bypass arrangement 20a, whereby in the current sensor 100a, a higher negative control voltage for the transistor 21a is generated. In the in FIG. 3a As illustrated, this negative control voltage VS (21a) then increases from about -0.75 volts to about -1.25 volts. Thus, the drain-source path of the transistor 21 a of the bypass device 20 a even higher impedance, in the example given so high that the current I (21 a) to about. Zero drops. The bypass arrangement 20a blocks, so that the entire current passed through the LED array LED1 current through the LED assembly. LED2 flows, see FIG. 3b from which it can be seen that both currents I (LED1) and I (LED2) are identical after reaching the threshold voltage for the second LED arrangement. In the time interval between the times T = 1.05 ms and T = 1.6 ms, the bypass arrangement 21b now operates as a current source, essentially as a constant current source in a manner similar to that described for the bypass arrangement 20a.

If the instantaneous value of the pulsating DC voltage VGL now reaches the sum of the forward voltages for the arrangements LED1, LED2 and LED3, the last-mentioned LED arrangement also assumes the conductive state at the time of approximately t = 1.6 ms FIGS. 3a, b illustrated time courses. The resistance value of the current sensor 100b is set in the given example so that when the third forward voltage is reached, the current I (21b) provided via the bypass arrangement 21b again drops sharply, but not to about zero as in the present step but to a comparatively low one Value. Only after reaching the forward voltage of the further LED arrangement is the bypass device 21b then transferred into the blocking state due to the further increased current flow through the current sensor 100b.

This process, which is described for the downstream first bypass arrangements, continues with increasing pulsating DC voltage VGL until, with appropriate design of the circuit, all the LED arrangements are connected in series have gone into the leading state. With further increasing DC voltage VGL, the total current is then limited by the current limiter 111, 112. With the falling of the applied voltage VGL, the process described in reverse order, the LED assemblies are successively bridged by the associated Bypassan-orders until the end alone the LED array LED1 is still traversed by current, which after the voltage drop VGL also blocks under their forward voltage.

As can be seen from the above illustration, the LED operating arrangement according to the invention has a plurality of series-connected LED arrangements, of which several are each assigned a bypass arrangement with which the associated LED arrangement can be bridged in an operating state. In addition, however, these bypass arrangements of the LED operating arrangement according to the invention are also set up and connected in order to act as a controllable resistor or as a controllable current source, wherein the control is realized by means of an output signal of a current sensor. Due to the fact that this current sensor detects both the current passed through the bypass arrangement and the current flowing through the LED arrangement, which is assigned to the respective bypass arrangement, it is achieved that the reaching or exceeding of the voltage is independent of any reference voltages Forward voltage of this LED array can be detected so that the control of the bypass arrangement automatically adapts to the electronic properties of the associated LED array.

The FIGS. 4a-f show over a network period, the time courses of the individual currents through the respective LED arrays in an inventively designed LED operating arrangement, which comprises a series connection of six such LED arrays. It puts FIG. 4a the timing of the downstream first LED array LED 1, FIG. 4b the temporal current flow through the second LED array LED2 and ultimately FIG. 4f the time course of the current through the sixth LED array LED6 again. The curves show the successive switching on and off of the respective LED arrangements over the network period. As can be seen, the illumination times of the individual LED arrays are different over the period.

As explained above, the current jumps at the switching of the respective LED arrays upon reaching the respective forward voltage by selecting the respective current sensor or the resistance value of this current sensor 100a to 100f to the course of the applied pulsating DC voltage VGL. Adjusted to the efficiency of the operating arrangement to optimize. In that sense, ideally in their entirety in FIG. 4a shown current jumps are not equidistant, but are adapted to the slope of the supply voltage or in the present case the pulsating DC voltage VGL. FIG. 5a shows the applied DC voltage VGL and FIG. 5b the total current, ie the current I (LED1) through the first LED array LED. 1

It should be noted that at the in FIG. 2 illustrated embodiment of an LED operating arrangement according to the invention, the LED array LED1 can also be arranged between the high output of the rectifier 10 and the LED array LEDn. Also in this case, the LED array LED1 adjacent to the LED array LED2 is to be regarded as between the two alone, the voltage source with the supply voltage VGL is located. For the purposes of the present invention, the term "adjacent" in relation to two LED arrangements designates two successive LED arrangements in the series connection, regardless of whether other elements, such as a current sensor or a current sensor, exist between these two LED arrangements Voltage source are arranged in series.

FIG. 6 shows a further embodiment of an inventively designed LED operating arrangement, which is only slightly different from the in FIG. 2 differentiates. Again, in a series arrangement of n LED devices (n-1), bypass arrangements 30a to 30 (n-1) are interconnected, which are each controlled by a signal of a stand alone current detector 100a to 100 (n-1). The same components are in terms of execution according to Fig. 2 provided with the same reference numerals. Although identical to the one in FIG. 2 As shown, the self-conducting field-effect transistors 31a to 31 (n-1) are different in that they are included in the redesigned bypass arrangement 30a to 30 (n-1). The bypass arrangements 30a to 30 (n-1), in turn, comprise a signal terminal S which, like the one in FIG FIG. 2 illustrated embodiment receives its control signal from a provided in the series circuit of LED arrays current sensor 100a to 100 (n-1), which are also formed here as resistors with well-defined resistance. The only difference to Fig. 2 is that the bypass arrangements according to FIG. 6 a second control terminal S2 which senses the cathode voltage of the LED array, which is adjacent to the associated LED array of the bypass arrangement downstream of the flow. Both control signals are conducted via respective series resistors in parallel to the gate of the respective transistor 31a to 31 (n-1).

Except for the fact that the respective bypass arrangement is supplied with two control signals, so differs in FIG. 6 illustrated LED operating arrangement not from the in FIG. 2 shown. That in the Figures 3 - 5 described temporal behavior is very similar, but the current jumps when reaching the respective threshold voltage of an LED array are in the in FIG. 6 illustrated embodiment also to the real threshold voltage of the LED assembly adapted which of the bypass arrangement is connected downstream. (The described parallel connection of the two control signals to the gate of the respective transistor has the consequence that at increased forward voltage in the downstream adjacent LED arrangement a reduced constant current is set in the bypass arrangement or an increased constant current at a lower forward voltage to set a constant electric power for the downstream adjacent LED array.

FIG. 7 shows a further embodiment of an inventively designed LED operating arrangement, with respect to the in FIG. 2 illustrated embodiment solely by the design of the bypass arrangement, the design of the Gesamtstrombegrenzers 120 and the placement of the LED array LED1 differs in the series connection of the LED assemblies. In this respect, the same components are again provided with the same reference numerals.

At the in FIG. 7 illustrated embodiment of an LED operating arrangement according to the invention, the LED array LED1 is disposed between the high output of the rectifier 10 and the LED array LEDn. Also in this case, the LED array LED1 is disposed adjacent to the LED array LED2, since between them both the current limiter 120 and the voltage source with the supply voltage VGL is located. In the current sensor 100a, the current flowing through LED1 current I (LED1) is detected and the output signal of the current sensor is applied to the control input S of the bypass device 40a, which is associated with the LED array LED2.

The interconnection of the respective bypass arrangement with respect to the sequence of LED arrays and respective current sensors is otherwise identical to that in FIG FIG. 2 shown .betriebsanordnung. But the internal design of the current limiter and the bypass arrangements is different to the above, but also according to FIG. 7 Bypass arrangements included bypass connections A1, A2 and a control input S. In addition, an auxiliary terminal H is provided, the corresponding terminals are shown by way of example and for clarity of illustration only for the bypass arrangement 40a. All bypass arrangements 40a to 40 (n-1) are again constructed identically. They each comprise a self-locking field-effect transistor whose drain or source is connected to the terminal A1 or A2. Via the auxiliary terminal H and the series resistors 42a, 43a, the pulsating DC voltage VGL is connected to the gate of the transistor 41a and thus serves to charge the same, so that the transistor already in the presence of a very low voltage VGL in the conductive state. In this respect, once again, after the zero crossing of the applied voltage VGL, all the bypass arrangements 40a to 40 (n-1) are conductive, so that the associated LED arrangements LED2 to LEDn are bridged.
Between the gate and source of the transistor 41a, the resistor 45a is provided.

The FIGS. 8a, b show time profiles of different current and voltage within the LED array according to FIG. 7 , similar to this in the FIGS. 3a, b with respect to the embodiment according to FIG. 2 is shown.

The FIGS. 8a, b again show a short section over a period interval starting from the zero crossing of the pulsating DC voltage VGL. After a little more than 0.5 ms, the threshold voltage of the LED array LED1 is reached, and after the rise of the current flowing through the LED1 until a current threshold determined by the controllable Zener diode 44a and the output signal of the current sensor 100a is reached, which over the interval between 0.5 ms and about 1.03 ms is kept approximately constant. In this interval, the bypass arrangement operates essentially as a constant current source, ie as a controlled resistor, such that the current flowing through the bypass arrangement remains constant. In this time interval, in turn, the difference between the threshold voltage of the LED array LED1 and the further increasing voltage VGL drops via the drain-source of the transistor 41a. If VGL reaches the sum of the forward voltages of the two LED arrays LED1 and LED2 conducts LED2, so that the additional current also leads to a further voltage drop at the current sensor 100a, and the transistor 41a goes into the blocking state, I (41a) drops to approximately zero , please refer FIG. 8a , In the embodiment shown, the circuit is designed so that after about 1.6 ms when VGL reaches the next forward voltage, more precisely the sum of the forward voltages of the LED arrays LED1, LED2 and LED3, the bypass device 40b also blocks, the current I (41b ) through transistor 41b drops to about zero, see FIG. 8a. FIG. 8b shows the gate-source voltage VGS (41a) of the bypass device 40a. The jump of this gate-source voltage on reaching the threshold voltage for the LED arrangement LED 2 leads to a jump to such values that this bypass arrangement 40a blocks. The further decrease in the gate-source voltage associated with the connection of the further LED arrangements is over FIG. 8b can be seen, but has no effect, since the bypass arrangement 40a already completely blocks.

The process described continues as the pulsating DC voltage VGL increases until all the LED arrays connected in series have become conductive when the circuit is designed accordingly. As the DC voltage VGL continues to increase, the total current is then limited by the current limiter. When falling of the applied voltage VGL, the process described in reverse order, the LED assemblies are successively bridged by the associated bypass arrangements until no LED array is traversed by current.

FIG. 9 shows the resulting total current I (LED1) for the self-conducting transistor embodiment in the bypass arrangements (indicated by SL) and for the self-blocking transistor embodiment in the bypass arrangements (indicated by SP) for the period of one grid period. Both embodiments give a comparable result.

LIST OF REFERENCE NUMBERS

1,2,3

LED operating arrangement

10

rectifier

20i

Bypass arrangement, i = a ... n-1

21i

Self-conducting field effect transistor, i = a ... n-1

22i

Series resistor, i = a ... n-1

30i

Bypass arrangement, i = a ... n-1

31i

Self-conducting field effect transistor, i = a ... n-1

32i

Series resistor, i = a ... n-1

33i

Series resistor, i = a ... n-1

40i

Bypass arrangement, i = a ... n-1

41i

Self-blocking field effect transistor, i = a ... n-1

42i

Series resistor, i = a ... n-1

43i

Series resistor, i = a ... n-1

44i

Controllable Zener diode, i = a ... n-1

45i

Gate-source resistance, i = a ... n-1

100i

Current sensor, i = a ... n-1

110

current limiter

111

Self-conducting field effect transistor

112

current sensor

113

dropping resistor

120

current limiter

121

Self-locking field effect transistor

122

current sensor

A1,

A2 bypass connection (source, drain connection)

H

Auxiliary voltage connection

I (LEDi, i = 1 ... n)

Current flow through the ith LED array

LEDi

LED arrangement, i = l ... n

N, L

mains connection

S, S2

control connection

SEE

Pulsating DC voltage

VN

mains voltage

VS (21i, i = a ... n-1)

Control voltage of the transistor 21i

VGS (41i, i = a ... n-1)

Gate-source voltage of the transistor 41i

Claims (10)

1. LED operating assembly (1, 2, 3) for operating a plurality of serially connected LED arrays (LEDi, i = 1...n) respectively having a first and a second terminal, comprising a supply voltage (VN, VGL) connected with the series connection of said LED arrays (LEDi, i = 1...n);
   a plurality of circuit arrangements each of which comprising:

   one of said LED arrays (LEDi, i = 1...n), a bypass arrangement (20, i = a...n-1), comprising a first and a second bypass terminal (A2, A1) as well as at least one control terminal (S), wherein said first bypass terminal (A2) is connected with the first terminal of said LED array (LEDi, i = 1...n) and wherein said bypass arrangement (20i, i = a...n1) is designed as a controllable resistor;

   a current sensor (100a ... n-1), wherein said current sensor (100a ... n-1) includes an output for delivering an output signal, and wherein said current sensor (100a ... n-1) is disposed on the downstream side of the current flow of said LED array and is configured for detecting the current flow through said LED array (LEDi, i = 1...n);

   and wherein said control terminal (S) of the bypass arrangement (20i, i = a...n-1) is connected with the output of said current sensor (100a ... n-1) and said controllable resistor is adjustable on the basis of said output signal in such a manner that the bypass arrangement is operable in a first operating state, which bridges said LED array (LEDi, i = 1...n), in a further operating state, which does not bridge said LED array (LEDi, i = 1...n), or in intermediate operating states between said first operating state and said second operating state; characterized in that said circuit arrangements are connected in series, wherein in each circuit arrangement said current sensor (100a, ... n-1) is connected in series with said LED array (LEDi, i = 1...n) so that the current detected by said current sensor (100a ... n-1) is the current through said bypass arrangement (20i, i = a...n-1) and said LED array (LEDi, i = 1...n).
2. LED operating assembly according to claim 1, characterized in that said current sensor (100a .. n-1) comprises a resistor.
3. LED operating assembly according to one of the claims 1 or 2, characterized in that said current sensor (100a .. n-1) has a terminal which is connected with said second bypass terminal (A2).
4. LED operating assembly according to claim 3, characterized in that in each circuit arrangement, except of the uppermost circuit arrangement on the upstream side of the current flow, said second bypass terminal (A1) is connected with the first bypass terminal (A2) of the circuit arrangement preceding in the upstream direction.
5. LED operating assembly according to one of the claims 1 to 4, characterized in that each bypass arrangement (20i; 30i, i = a...n-1) comprises a normally-on transistor or a self-locking transistor.
6. LED operating assembly according to one of the claims 2 to 5, characterized in that resistors of the current sensors (100a ...n-1) provided in the series connections of the LED arrays (LEDi, i = 1 ... n) increase steadily in their resistance value on the downstream side of the current flow, wherein said LED operating assembly (1, 2, 3) is designed in such a manner that when receiving current, it connects said LED arrangements (LEDi, i = 1...n) in sequence.
7. LED operating assembly according to one of the claims 1 to 6, characterized in that said bypass arrangements (20i; 30i; 40i, i = a...n-1) are connected in series.
8. LED operating assembly according to one of the claims 1 to 7, characterized in that the supply voltage (VN, CGL) is a pulsating DC voltage (VGL) that is provided by a rectifier that is supplied with an AC voltage.
9. LED operating assembly according to one of the claims 1 to 8, characterized in that in at least one of the circuit arrangements, said bypass arrangement (30i, i = a...n-1) comprises an additional control terminal (S2) that is connected with the LED array of said circuit arrangement, which is arranged on the downstream side of the current flow in the series connection of the circuit arrangements subsequently to said at least one circuit arrangement.
10. Method for operating a LED operating assembly (1, 2, 3) according to one of the claims 1 to 9, comprising the following steps:

    operating the LED array (LEDi, i = 1...n) at the operating voltage; and

    comprising the following steps in each circuit arrangement:

    detecting the current through the LED arrangement (LEDi, i = 1...n) and the bypass arrangement (20; 30i, i = a...n-1) by means of a current sensor (100a ..n-1);

    adjusting the controllable resistor of the bypass arrangement (20; 30i, i = a...n-1) on the basis of the output signal from the current sensor (100a ..n-1);

    operating the LED array (LEDi, i = 1...n) in one of the first, second operating states or in the intermediate operating states.

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