DE102012207457A1 - Circuit for controlling e.g. LEDs of lamp or lamp system, has driver controlling LED-segments, including electronic switches, and coupled with rectified power supply voltage by separate voltage source - Google Patents

Abstract

The circuit has LED-segments (101-103) connected in series, and including multiple semiconductor luminous elements connected in series. The luminous elements in two of the LED-segments are different. A driver controls the LED-segments, and includes electronic switches (SW1-SW3) e.g. MOSFETs, where one of the LED-segments is bridgeable based on the switches. The driver is coupled with a rectified power supply voltage by a separate voltage source. The source is formed by a voltage divider, an auxiliary voltage source, and a zener diode, and controlled based on an average value of the voltage. The rectified power supply voltage is a pulsed direct voltage.

Description

The invention relates to a circuit for driving semiconductor light elements and a lamp, a light or a lighting system with such a circuit.

It is known to operate an LED module comprising a plurality of light-emitting diodes by means of a single-stage or multi-stage switching power supply which is connected upstream of the LED module. If the LED module has a power range greater than 25W, an additional power factor correction (PFC) is required. At low electrical power usually a linear regulator is used.

Above certain light or power classes where e.g. a plurality of LEDs are to be operated in one module or in a plurality of LED modules, circuit arrangements are known in which many LED chips are connected in series. The forward voltage of this series circuit can be of the order of the mains voltage.

In a simple embodiment, LEDs connected in series are operated directly on the AC voltage network. This leads to a strong light modulation, a so-called "flicker", and an energy-inefficient use of LEDs. For higher power classes, this approach continues to cause problems with normative power factor and harmonic specifications.

Furthermore, it is known to connect the series circuit of LEDs a rectifier. Again, there are the above problems.

Furthermore, it is known to change the interconnection of the LED series circuit in time synchronization with the mains voltage modulation.

So shows DE 10 2010 040 266 A1 an LED luminaire with an integrated circuit, a rectifier and a series of series-connected LEDs operated by a rectified AC signal. The integrated circuit has power switches that can individually and selectively short a corresponding group of different groups of LEDs in an LED array over which the rectified AC signal is applied. As the voltage across the row increases, the integrated circuit controls the power switches to increase the number of LEDs through which current flows, while the integrated circuit controls the power switches by the number as the voltage across the train decreases of LEDs, through which electricity flows, decrease.

The object of the invention is to improve the known solution and to provide an efficient way of controlling semiconductor light elements.

This object is achieved according to the features of the independent claims. Further developments of the invention will become apparent from the dependent claims.

• – mit mindestens zwei in Reihe geschalteten Segmenten, die jeweils mehrere in Reihe geschaltete Halbleiterleuchtelemente aufweisen,
• – wobei die Halbleiterleuchtelemente in zumindest zwei der Segmente unterschiedlich sind,
• – mit je einem Treiber zur Ansteuerung eines Segments, wobei der Treiber mindestens einen elektronischen Schalter aufweist, anhand dessen das Segment überbrückbar ist,
• – bei der die Treiber über mindestens eine Spannungsquelle mit der gleichgerichteten Netzspannung gekoppelt sind.

To solve the problem, a circuit for driving semiconductor light elements is proposed,

• With at least two segments connected in series, each having a plurality of semiconductor light elements connected in series,
• Wherein the semiconductor light elements are different in at least two of the segments,
• Each having a driver for driving a segment, wherein the driver has at least one electronic switch, by means of which the segment can be bridged,
• - In which the drivers are coupled via at least one voltage source with the rectified mains voltage.

The driver may be a circuit arrangement that can be used to drive a segment.

The drivers are thus operated by a rectified mains voltage in the form of a pulsating DC voltage. It is advantageous that the rectification of the mains AC voltage must provide no memory (capacitor). In particular, no (smoothing) electrolytic capacitor must be provided, which is designed for the entire height of the mains voltage. This reduces the susceptibility to errors and allows a more compact design of the circuit.

By means of the electronic switch, a switching function is electronically controlled. The electronic switch may comprise a transistor, a MOSFET, an operational amplifier, a comparator or a component which can be acted upon by a switching function.

The semiconductor light elements are, for example, LEDs, LED chips or LED modules. A semiconductor light-emitting element can also comprise at least one OLED (organic light-emitting diode) or a module with at least one OLED.

By means of the at least one voltage source, an offset voltage can be set for the drivers. It is also possible that the currents for the semiconductor light elements of the segments are adjusted by the multiple voltage sources, e.g. symmetrized.

A further development consists in that the drivers are coupled to the rectified mains voltage via at least one voltage source.

An additional embodiment is that each driver is coupled to the rectified mains voltage via a separate voltage source.

• – eines Spannungsteilers;
• – einer Hilfsspannungsquelle;
• – einer Zenerdiode.

A development is that the at least one voltage source can be realized by means of:

• - a voltage divider;
• An auxiliary power source;
• - a zener diode.

It is also a possibility that the voltage source can be controlled depending on an average value of the rectified mains voltage.

Thus, based on the (controllable) voltage source, a relationship to the average mains voltage can be established. Based on the voltage sources for the multiple drivers, it is possible to symmetrize the currents for the semiconductor light elements of the segments.

For example, a longer-term averaging can take place over a network period or over several network periods of the network voltage. The (longer term) averaging can depend on a peak, a mean, or the like. respectively. In this case, the mains voltage may already be rectified or it may be an AC mains voltage.

An additional development is that the drivers can be supplied with a rectified mains voltage.

A development is that at least two of the segments have semiconductor light elements which are at least partially different in their forward voltages, their colors, their sizes, their designs and / or their numbers.

Another development is that the driver comprises a predicate.

The predicate may e.g. be a comparator or include such. The comparison element can be designed as (at least) one operational amplifier or as at least one transistor.

The comparison element compares a first reference potential, e.g. one side of the rectified mains voltage, with a second reference potential, e.g. a potential at the end or in the respective segment.

In particular, it is a development that the segments are connected in series with a current regulator.

Based on the current controller, the current in the segments can be specified. At the current regulator, a predetermined voltage may drop, e.g. the voltage that does not drop across the serially connected semiconductor light elements.

The current regulator can self-adjust a current or it can be used to set a current.

It is also a development that the current regulator can be controlled by means of dimming.

One option is that the current controller is controlled and thus a brightness control (dimming) of the semiconductor light elements can be achieved. The driving can be done in different ways, e.g. via a potentiometer, a DALI system, a microcontroller or a 1-10V interface.

Furthermore, it is a development that the current controller has a resistive element or a linear regulator.

In the context of an additional development, the segment with the greatest forward voltage has at least twice as much forward voltage as the segment with the lowest forward voltage.

For example, the segment with the greatest forward voltage may have at least 60% greater forward voltage than the segment with the second largest forward voltage.

A next development is that the electronic switch of the driver is active with a switching frequency which has at least twice the network frequency or a multiple of the network frequency.

In particular, the switch of the driver which drives the segment with the greatest forward voltage can be operated with a switching frequency of at least 100 Hz.

An embodiment is that at least one of the drivers has a capacitor which is arranged parallel to semiconductor light elements of the segment to which the driver is assigned.

In particular, the capacitor may be arranged in parallel only to a part of the semiconductor light elements of the segment.

One embodiment is that the capacitor is arranged in or together with the driver which drives the segment with the greatest forward voltage.

Also, one such (buffer) capacitor can be arranged in each of several drivers, which are preferably those drivers which drive the segments from the several segments whose semiconductor light-emitting elements have the greatest forward voltages.

A next embodiment is that the capacitor is designed to be interchangeable via a detachable connection.

In particular, this (buffer) capacitor can be arranged over the detachable connection at a location other than the circuit. Thus, the capacitor can be easily replaced via the detachable connection.

It is also an embodiment that at least one of the drivers has a series circuit of a capacitor and a diode, wherein this series circuit is arranged parallel to the semiconductor light elements of the segment, which drives the driver.

The series connection of capacitor and diode is a peak detector for the respective segment.

Another development is that at least one decoupling diode is arranged between each two segments.

It is also a further embodiment that a device for mixing the light provided by a plurality of segments is provided.

For example, it is possible to provide an optical system by means of which emitted light a plurality of semiconductor light-emitting elements is mixed.

• – der Treiber einen elektronischen Kurschluss-Schalter umfasst, anhand dessen das dem Treiber zugeordnete Segment kurzschließbar ist,
• – wobei der Basis-Anschluss des Kurzschluss-Schalters über ein erstes strombegrenzendes Element mit dem Kollektor-Anschluss eines elektronischen Vergleichs-Schalters verbunden ist,
• – wobei der Emitter-Anschluss des Vergleichs-Schalters mit einem Anschluss des Segments, dem der Treiber zugeordnet ist, verbunden ist,
• – wobei der Basis-Anschluss des Vergleichs-Schalters mit einem Pol der gleichgerichteten Netzwechselspannung verbunden ist.

An additional embodiment is that

• The driver comprises an electronic short-circuit switch, by means of which the segment assigned to the driver can be short-circuited,
• Wherein the base terminal of the short-circuiting switch is connected via a first current-limiting element to the collector terminal of an electronic comparison switch,
• Wherein the emitter terminal of the comparison switch is connected to a terminal of the segment to which the driver is assigned,
• - Wherein the base terminal of the comparison switch is connected to a pole of the rectified AC line voltage.

For example, the short-circuit switch is a pnp transistor and the comparison switch is an npn transistor. Accordingly, in a dual embodiment, pnp and npn transistors can also be reversed with appropriate potential matching. As switches, other electronic switches, e.g. Transistors, Mosfets, or similar be provided.

At the base-emitter junction of the comparison switch, the potential at the respective segment (e.g., a comparison point within the LED string) is compared with the potential of the current rectified half-wave. Accordingly, an activation of the respective segment by the driver can take place as a function of the magnitude of the rectified mains alternating voltage.

Optionally, the base terminal of the comparison switch may be connected to a pole of a voltage source which represents an offset voltage with respect to the potential of the rectified AC line voltage.

The above object is also achieved by a lamp, a luminaire or a lighting system with a circuit as described herein.

The lamp, light or the lighting system may be an LED light source.

The above-described characteristics, features, and advantages of this invention, as well as the manner in which they will be achieved, will become clearer and more clearly understood in connection with the following schematic description of exemplary embodiments which will be described in detail in conjunction with the drawings. In this case, the same or equivalent elements may be provided with the same reference numerals for clarity.

Show it:

1 a schematic circuit arrangement for driving three LED segments, wherein the individual LED segments have different numbers of LEDs and the LED segments can each be bridged or short-circuited by means of a parallel electronic switch;

2 a schematic circuit for driving three LED segments, wherein the LED segments have different numbers of LEDs, wherein between individual LEDs partially a decoupling diode and parallel to a selection of the LED segments a capacitor is arranged;

3 a schematic circuit arrangement for controlling a plurality of electronic switches by means of comparators;

4 based on the representation of 3 a plurality of voltage sources for symmetrizing the currents between individual LED segments;

5 an alternative schematic circuit arrangement for driving a plurality of electronic switches by means of discrete components;

6 a detailed presentation of in 5 shown modules 522a to 522d ;

7 an alternative circuit arrangement to 5 ;

8th an alternative circuit arrangement, substantially on the circuit according to 7 based and provides several voltage sources that can be used to control or symmetrize the individual LED segments.

Operation of an LED chain at a mains voltage

An LED chain comprises several segments (LED segments) connected in series with each other. If necessary, further components can be arranged between the LED segments. Each LED segment may have a plurality of LEDs connected in series with each other.

A mains voltage refers to an alternating voltage as e.g. provided by an electrical supply network. The mains voltage can be converted via a rectifier into rectified mains half-waves (also referred to as "half-waves" or "pulsating mains voltage"). The rectifier may be implemented as a one-way or a two-way rectifier.

To control the series-connected LED segments combinatorial possibilities of the LED segments corresponding forward voltages are exploited. According to the number of LEDs connected in series in a segment, a forward voltage results. Different numbers of LEDs connected in series result in different forward voltages for different LED segments. The number of LED segments is denoted by M below.

It should be noted that different LEDs of the same or different type (e.g., different LED modules and / or LEDs of different colors) may be connected in series. It is also possible for individual LEDs to comprise a parallel connection of at least one semiconductor light-emitting element.

Parallel to at least one LED segment, in particular parallel to a plurality of LED segments, electronic switches can be provided which short-circuit individual or multiple LED segments. By controlling the electronic switches can be achieved that the voltage at the LED segments U _LED (t) of the rectified mains voltage U _in (t) (ie the above half-waves) follows (or is tracked): U _LED (t) = U _LED (t _i , I) = U _i (I), where U _i (I) is a total voltage of the non-bridged LEDs for the switching state i at a current I.

In this case, the LED segments are preferably designed differently, i. have at least partially mutually different forward voltages. In particular, at least two of the LED segments have different numbers and / or types of LEDs. In other words, not all LED segments with the same number of LEDs of the same type are equipped in the same interconnection. In this way, the individual LED segments are activated or deactivated at different times (during the course of the rectified mains voltage) and possibly also at different times per network period, ie. operated at a different frequency.

It can be used to control the switch (to bridge the LED segments) and frequencies that are higher than the mains frequency. As a result, there are a large number of switchable states that can be combined in order to control the different switches. The number of possible switching states N is thus considerably larger (2 ^M ) than the number of LED segments M.

i

den Schaltzustand,

SW_m

mit m = 1 bis 3 den Schalter,

0

einen offenen Schalter,

1

einen geschlossenen Schalter

U_f1(I) bis U_f3(I)

eine Vorwärtsspannung der nicht überbrückten LEDs bei dem Strom I für das LED-Segment 1 bis 3.

bezeichnen. i SW₁ SW₂ SW₃ U_i(I) 1 1 1 1 2 0 1 1 U_f1(I) 3 1 0 1 U_f2(I) 4 0 0 1 U_f1(I) + U_f2(I) 5 1 1 0 U_f3(I) 6 0 1 0 U_f1(I) + U_f3(I) 7 1 0 0 U_f2(I) + U_f3(I) 8 0 0 0 U_f1(I) + U_f2(I) + U_f3(I) The following tabular list shows examples of possible combinations in an arrangement with three LED segments, where

i

the switching state,

SW _m

with m = 1 to 3 the switch,

0

an open switch,

1

a closed switch

U _f1 (I) to U _f3 (I)

a forward voltage of the non-bridged LEDs in the current I for the LED segment 1 to 3.

describe. i SW ₁ SW ₂ SW ₃ U _i (I) 1 1 1 1 2 0 1 1 U _f1 (I) 3 1 0 1 U _f2 (I) 4 0 0 1 U _f1 (I) + U _f2 (I) 5 1 1 0 U _f3 (I) 6 0 1 0 U _f1 (I) + U _f3 (I) 7 1 0 0 U _f2 (I) + U _f3 (I) 8th 0 0 0 U _f1 (I) + U _f2 (I) + U _f3 (I)

The residual stress U _in (t) - U _LED (t) falls off on a current regulator. With a plurality of LED segments with different (many) LEDs connected in series, a variety of different total forward voltages for the LED chain can be realized, so that this total voltage is very close to the current mains voltage. The residual voltage is thus small compared to the mains voltage.

Because of this low residual voltage, the current regulator can be designed, for example, as a simple and cost-effective linear regulator. The current regulator may also be designed so that the current follows (almost) ideally the mains voltage, so that a power factor of the circuit is close to 1.0 and no (significant) harmonics occur.

In extreme cases, the current regulator can even be omitted, e.g. if the dynamics of the LED characteristic with a limited current modulation is sufficient to fill the intervals between the switching stages.

A possible dimensioning of the LED segments is that a first LED segment has a number A of LEDs connected in series, another (next) LED segment has a number A / 2, another LED segment has a number A / 4, etc. If, for example, an index m identifies an LED segment, this relationship can be represented by A _m = A _{m +} 1/2 where m = 1 ... M identifies the different M LED segments.

For the sake of simplification, it is assumed that the LED voltage U _i (I) is current-independent, ie U _i (I) ~ U _i (I _nominal ), then this design leads to equidistant voltage values. This arrangement is favorable, but not necessarily optimal, since the density of the switching states in the current maximum for the power loss plays a greater role than in the field of current zero crossings.

1 illustrates the relationship described above with reference to a schematic circuit arrangement for driving three LED segments 101 . 102 and 103 , where the LED segment 101 a series connection of four LEDs, the LED segment 102 a series connection of two LEDs and the LED segment 103 has a single LED. The LED segment 101 is bridged with a switch SW ₃ arranged parallel thereto, the LED segment 102 is bridged with a switch SW ₂ arranged in parallel and the LED segment 103 is bridged with a switch SW ₁ arranged parallel thereto. The switches SW ₁ to SW ₃ are designed as electronic switches, for example transistors or field-effect transistors, which are controlled by a control unit (not in FIG 1 shown).

The LED segments 101 to 103 are with each other and with a current regulator 104 connected in series. At the current regulator 104 it can be a resistive element, in particular a linear regulator. Alternatively, it is also possible that the current regulator 104 is an active current regulator.

One option is that the current controller is controlled and thus a brightness control (dimming) of the LEDs can be achieved. The drive can be implemented in different ways, e.g. a potentiometer, a DALI system or a 1-10V interface.

An AC mains voltage 105 , eg 230VAC, is connected via a rectifier 106 converted into a pulsating mains voltage and with the series circuit comprising the LED segments 101 to 103 as well as the current regulator 104 , connected. In the series circuit, a time varying current I (t) flows. At the LED segment 101 falls forward voltage U _f3 , on the segment 102 the forward voltage U _f2 and at the LED segment 103 the forward voltage U _f1 , if the respective LED segment is not bridged by means of the associated parallel switch SW ₁ to SW ₃ .

Additional conditions for optimizing the switching processes

For example, the number of LEDs per segment may be determined as a first quantity and the switching frequency of the electronic switches for bridging the LED segments may be determined as a second quantity. These two quantities can be optimized by means of two or three of the secondary conditions explained below. Preferably, the secondary conditions for the entire operating voltage range or at least for a large part of the operating voltage range are met.

• (A) Ein unterbrechungsfreier Stromfluss (ohne Oberwellen) wird erreicht, wenn U_in(t) – U_LED(t) >= U_P(t) (1) erfüllt ist, wobei U_P die Summe parasitärer Spannungsabfälle in Gleichrichterdioden, Schaltern, etc. bezeichnet.
• (B) Eine Minimierung der Verlustleistung wird erreicht, wenn INT(0..T)[(U_in(t) – U_LED(t))·I(t)] => minimal (2) erfüllt ist, wobei

  INT(0...T)[...]

  einem Integral über eine Netzperiode

  entspricht.

The first two constraints (A) and (B) are:

• (A) An uninterrupted flow of current (without harmonics) is achieved when U _in (t) - U _LED (t)> = U _P (t) (1) is satisfied, where U _P denotes the sum of parasitic voltage drops in rectifier diodes, switches, etc.
• (B) Minimization of power dissipation is achieved when INT (0..T) [(U _in (t) -U _LED (t)) * I (t)] => minimum (2) is satisfied, where

  INT (0 ... T) [...]

  an integral over a network period

  equivalent.

• (C) Ein gewünschtes Verhältnis zwischen den Strömen in den LED-Segmenten wird erreicht, wenn INT(0..T)[I(t)·SW_m(t)]/(I_Soll,m·T) = 1 für alle m (3) erfüllt ist, wobei

  SW_m(t)

  einen Schaltrhythmus (0: Schalter ist geschlossen, 1: Schalter ist offen) für das Segment m zur Zeit t und

  I_Soll,m

  einen gewünschte Strom für das LED-Segment m

  bezeichnen.

Another optimization condition (C) is added if the ratio of the average currents in the different LED segments is important, eg the current density in all LEDs should be the same. This applies in particular if this ratio of the average currents over the entire operating voltage range is to be maintained.

• (C) A desired ratio between the currents in the LED segments is achieved when INT (0..T) [I (t) * SW _m (t)] / (I _{ref, m} * T) = 1 for all m (3) is satisfied, where

  SW _m (t)

  a switching rhythm (0: switch is closed, 1: switch is open) for the segment m at time t and

  I _{Soll, m}

  a desired current for the LED segment m

  describe.

An alternative to the constraint (C) would be if the light of all LED segments were mixed so that differences in brightness did not play a (significant) role. In this case, the constraint (C) can be omitted.

It is also possible to design the LED chip sizes and the distances between the chips in the LED segments differently, so that the current densities in the LED segments are adapted to the average current of the respective LED segment.

The secondary condition (C) is particularly advantageous if the LED segments contain different types or types (for example colors) of LEDs and the activation of the switches (switching rhythm per segment i) is used to distribute the power as needed. Possible applications include an electronic calibration of the color locus, a tracking of a white point over the lifetime and modules with an adjustable white point.

By way of example, it is assumed below for a clear representation that the switching stages i for a particular current I are sorted in ascending order according to the LED voltage U _i (I).

Solution strategy for the constraints (A) and (B)

• – im 1. und 3. Quadranten der Netzspannung, also bei steigender Netzspannung, der Wechsel vom Schaltzustand i zum nächsten Schaltzustand i + 1 dann erfolgt, wenn die Nebenbedingung (A) für den Schaltzustand i + 1 gerade erfüllt wird und
• – im 2. und 4. Quadranten der Netzspannung, also bei sinkender Netzspannung, der Wechsel vom Schaltzustand i zum nächsten Schaltzustand i – 1 genau dann erfolgt wenn die Nebenbedingung (A) für den Schaltzustand i gerade nicht mehr erfüllt wird.

The constraints (A) and (B) are then optimally fulfilled when

• - In the 1st and 3rd quadrant of the mains voltage, ie with increasing mains voltage, the change from the switching state i to the next switching state i + 1 then takes place when the secondary condition (A) for the switching state i + 1 is just fulfilled and
• - In the 2nd and 4th quadrant of the mains voltage, ie with decreasing mains voltage, the change from the switching state i to the next switching state i - 1 occurs exactly when the secondary condition (A) for the switching state i just is no longer met.

This circuit diagram can be achieved for example by a microcontroller with an analog-to-digital converter (A / D converter). Alternatively, circuits (see below) may be provided, which manage without a microcontroller and are particularly cost-effective to implement.

w = 2·pi·f

die Netzfrequenz (wird auch mit dem kleinen griechischen Buchstaben Omega abgekürzt) und

I(t)

den eingeprägten Strom des Stromreglers

bezeichnen.For an ideal sinusoidal mains voltage U (t) = U ₀ × sin (wt) would be the switching time t _i = arcsin (U _i (I (t)) / U ₀ ) / w, (4) in which

w = 2 · pi · f

the mains frequency (also abbreviated to the small Greek letter Omega) and

I (t)

the impressed current of the current controller

describe.

With the simplistic assumption U _i (I) ~ U _i (I _nom ) = U _i applies t _i = arcsin (U _i / U ₀ ) / w (5). The values t _i from equation (5) can be stored, for example, in the form of a value table for a time control, for example in a low-cost microcontroller or an application-specific integrated circuit (ASIC).

• (i) Bei ansteigender Netzspannung (im 1. und 3. Quadranten) werden Schaltzeitpunkte t_i’ = t_i + dt_i gezielt verzögert, so dass die Ströme wunschgemäß verteilt werden. Im Fall der fallenden Netzspannung (im 2. und 4. Quadranten) werden die Schaltzeitpunkte vorverlegt, so dass die Nebenbedingung (C) besser erfüllt wird.
• (ii) Die Kurvenform des eingeprägten Stromes I(t) des Stromreglers wird so modifiziert, dass die Nebenbedingung (C) besser erfüllt wird.
• (iii) Die Anzahlen der LEDs pro LED-Segment werden so bestimmt, dass die Nebenbedingung (C) besser erfüllt wird.

Solution strategy for the constraint (C) The constraint (C) can be fulfilled or improved, for example, by means of the following measures:

• (i) With increasing mains voltage (in the 1st and 3rd quadrant) switching times t _i '= t _i + dt _i deliberately delayed, so that the streams are distributed as desired. In the case of falling line voltage (in the 2nd and 4th quadrant), the switching times are advanced, so that the secondary condition (C) is better met.
• (ii) The waveform of the impressed current I (t) of the current controller is modified so as to better satisfy the constraint condition (C).
• (iii) The numbers of LEDs per LED segment are determined so that the constraint condition (C) is better satisfied.

The measure (i) can generally fully satisfy the constraint (C), but has the disadvantage that the constraint (B) is thereby (slightly) violated. Overall, this can lead to a slightly increased power loss.

The values dt _i are preferably the subject of a numerical optimization as a function of the mean input voltage U _in . The values t _i 'may, for example, be stored in a memory of a microcontroller for all input voltages U _in .

The measure (ii) is limited for example by specifications of the power factor and harmonics. This limitation depends on the performance class (e.g., greater or less than 25W) as required by applicable standards. A current component with the frequency of the third mains harmonic is allowed within certain limits in the standards and possibly has a positive effect on the secondary condition (C).

The measure (ii) can be achieved, for example, by modifying the control of the current controller 104 , For example, the third harmonic of the current could be introduced as a function of the average mains voltage. The design of the controller can be done eg via a numerical optimization.

The measure (iii) can be optimized for only one operating voltage point.

For example, the measures (iii) and possibly also (ii) can be optimized for the rated voltage. The measure (i) can then be corrected over the entire operating voltage range.

Exemplary concretization

An ideal delay of the switching time dt _i may possibly not be determined purely analytically and may also not be unique.

There are more switching times dt _i as LED segments are present. Thus, there are more manipulated variables than are required for the fulfillment of the secondary conditions. The optimization problem can be solved numerically as a nonlinear optimization problem according to the constraint (C) taking into account (compliance) the constraint (A). Here, the constraint (B), as explained above, can be violated to some extent.

For example, the sum of the error squares, that is to say deviations of the segment currents from the respective nominal current of the LED segment, can be used as an optimization _quantity E _err (U _in , t _i ').

The following is a concrete example of such an optimization task. It assumes a four-stage arrangement (four LED segments) with the following parameters: the first LED segment has 6 LEDs connected in series, the second LED segment has 12 LEDs connected in series, the third LED segment has 24 in series switched LEDs and the fourth LED segment has 51 series connected LEDs. Furthermore, the following relationships apply: Forward voltage per LED: Uf = 3.2V (at rated current I _rated ) Parasitic tension: Up = 6.2V Power factor: PF = 1.00 (ideal sinusoidal voltage and current curve)

A theoretical efficiency is a function of the input voltage and a measure of the asymmetry of the average current distribution between the segments. The theoretical efficiency eff _{th is} calculated from the ratio of the LED voltage U _i to all other voltage drops. Possible dynamic switching losses are not taken into account here for the sake of simplified representation. eff _th = INT (0..T) [U _LED (t) * I (t)] / INT (0..T) [U _in (t) * I (t)]

In this case, almost over the entire operating voltage range, an electrical efficiency of more than 90% can be achieved. The switching voltages of the individual electronic switches, which are each connected in parallel to one of the four LED segments, are for example fixed and follow the secondary conditions (A) and (B), resulting in an optimized efficiency.

Exemplary optimization of LED efficiency

In addition, a current modulation by the current setting I (t) in the current regulator as well as the switching rhythm in the control of the electronic switches can lead to an undesired light modulation and to a suboptimal efficiency of the LED operation.

The reduction in LED efficiency is a consequence of the so-called droop effect. The higher current in the time-limited switch-on phases of the LED segments leads to a reduced efficiency compared to a continuous constant current operation with the same average current. For the same efficiency as in continuous constant current operation, a larger chip area would have to be used to lower the current density in the LED chips. In other words, chip area utilization is worse in clocked mode than in constant current mode.

2 shows a schematic circuit for driving three LED segments, wherein the LED segments have different numbers of LEDs, between individual LEDs partially a decoupling diode and parallel to a selection of the LED segments a capacitor is arranged.

In the 2 shown circuit refers in parts to the circuit according to 1 , In contrast to 1 the series circuit comprises a diode D1, the LED segment 101 , a diode D2, the LED segment 102 , the LED segment 103 and the current regulator 104 , The diodes D1 and D2 are decoupling diodes. The diodes D1 and D2 are poled as the LEDs, ie all the cathodes of the diodes point in the direction of the negative pole.

The switch SW ₃ is parallel to the series circuit of diode D1 and LED segment 101 arranged. The switch SW ₂ is parallel to the series circuit of diode D2 and LED segment 102 arranged. The switch SW ₁ is parallel to the LED segment 103 arranged.

Additionally is in 2 parallel to the LED segment 101 a capacitor C3 and parallel to the LED segment 102 a capacitor C2 is arranged.

The circuit according to 2 avoids the disadvantage of unwanted light modulation described above. By the capacitors C2 and C3 (which are designed for example as electrolytic capacitors), a continuous operation of the LEDs is possible. The current modulation depends on the capacitance of the capacitor and the slope of the LED characteristic. The larger the capacitor, the lower the modulation.

The decoupling diodes D1 and D2 between the LED segments prevent the discharge of the capacitors C2 and C3 via the switches.

To prevent unwanted flicker at twice the line frequency, the LED segment with the highest forward voltage (in the example of FIG 2 the LED segment 101 ) are buffered, for example, with a correspondingly large-sized capacitor C3 connected in parallel.

The remaining LED segments may be e.g. be operated with a frequency higher than twice the mains frequency and therefore contribute little or no noticeable flicker.

It is advantageous that the buffer capacitor (in the example of the 2 the capacitor C3) only needs to be designed for a lower than the maximum mains voltage. In 2 This reduced voltage is determined by the forward voltage U _{f3 of} the LEDs of the LED segment 101 ,

Preferably, all LED segments (in particular those LED segments with a forward voltage which is higher than a predetermined threshold value) can be buffered with capacitors connected in parallel. However, if an LED segment includes only a few LEDs or only a single LED, the buffer capacitor can be dispensed with (see in this regard, for example, the LED segment 103 in 2 ).

An advantageous embodiment consists in providing ("buffering") only those LED segments with capacitors connected in parallel, which have the most series-connected LEDs or the greatest forward voltages. For example, only the LED segment with the greatest forward voltage or the two LED segments with the largest forward voltages can be buffered accordingly.

For example, the capacitance required for the capacitors is approximately the same for all LED segments because the available voltage swing decreases with the shorter chains, but at the same time the frequency is higher for the shorter chains.

Using the example of the tabulated list shown above, it can be seen that for each half the voltage, and thus half the voltage swing dU _m , the frequency doubles in the switching rhythm. The to be bridged currentless phases of duration dt _m are therefore only half as long. For the same desired current I _{Soll, m} (symmetrical), for example, all capacitors C _{m are the} same size. The stresses are different: Q = I _{target, m} · dt _m = C _m · dU _m (6).

Automatic generation of the switching rhythm

The control of the switch in 1 and 2 exemplified electronic switch SW ₁ to SW ₃ can be done by means of a control unit, such as a microcontroller. Due to the variable ("floating") potentials, this can be done using a potential-free (galvanically isolated) control. Such a realization is relatively expensive and therefore expensive.

3 shows a schematic circuit arrangement for controlling a plurality of electronic switches by means of comparators.

As already with regard to 1 explains, the AC line voltage 105 via a rectifier 106 rectified and the rectified "pulsating" line voltage between two nodes 301 and 302 created.

A series connection from the LED segment 101 , a diode D3, the LED segment 102 , the diode D2, the LED segment 103 , the diode D1 and the current regulator 104 connects the knots 301 and 302 , Parallel to the LED segment 101 is the capacitor C3, parallel to the LED segment 102 is the capacitor C2 and parallel to the LED segment 103 a capacitor C1 is arranged.

The switch SW ₃ is parallel to the series circuit of LED segment 101 and diode D3 arranged. The switch SW ₂ is parallel to the series circuit of LED segment 102 and diode D2 arranged. The switch SW ₁ is parallel to the series circuit of LED segment 103 and diode D1.

The switch SW ₃ is via the output of a comparator 303 driven. Parallel to the LED segment 101 is a voltage divider comprising a series circuit of resistors 304 and 305 arranged, wherein the center tap of this voltage divider with the inverting input of the comparator 303 connected is. The knots 301 and 302 are a voltage divider comprising a series circuit of resistors 306 and 307 connected, wherein the center tap of this voltage divider with the non-inverting input of the comparator 303 connected is.

The switch SW ₂ is via the output of a comparator 308 driven. Parallel to the LED segment 102 is a voltage divider comprising a series circuit of resistors 309 and 310 arranged, wherein the center tap of this voltage divider with the inverting input of the comparator 308 connected is. The node above the LED segment 102 and the node 302 are a voltage divider comprising a series circuit of resistors 311 and 312 connected, wherein the center tap of this voltage divider with the non-inverting input of the comparator 308 connected is.

The switch SW ₁ is via the output of a comparator 313 driven. Parallel to the LED segment 103 is a voltage divider comprising a series circuit of resistors 314 and 315 arranged, wherein the center tap of this voltage divider with the inverting input of the comparator 313 connected is. The node above the LED segment 103 and the node 302 are a voltage divider comprising a series circuit of resistors 316 and 317 connected, wherein the center tap of this voltage divider with the non-inverting input of the comparator 313 connected is.

The control of the electronic switches SW ₁ to SW ₃ is carried out according to 3 based on the comparators 303 . 308 and 313 , The control is preferably carried out in such a way that the switches SW ₁ to SW ₃ are opened when the voltage between the reference potential of the LED segments (in the example according to FIGS 3 at the top of the respective LED segment) and the node 302 is greater than the forward voltage of the respective LED segment.

The voltage difference between the reference potential of the LED segment m (at the top of each LED segment) and the node 302 is also referred to below as the voltage difference (or control voltage) US _m for the LED segment m.

This voltage difference US _m also includes the voltage drop of all between the LED segment m and the node 302 lying other LED segments. If the LED segment m is switched active, the voltages at the other LED segments US _j are also affected for all j <m, whereby these LED segments also switch almost simultaneously. This results in the desired switching rhythm.

The voltage of the LED segment m can be measured directly by the comparator if the chain has a buffer capacitor C _m . Otherwise, the voltage on the LED segment may be replicated via an analog reference voltage or via a sample-and-hold circuit.

5 and 6 show a circuit arrangement with such a sample-and-hold circuit and four LED segments. The comparators explained above are in 5 and 6 implemented cost-effectively by means of discrete components.

An AC mains voltage 501 is over a rectifier 502 with two nodes 503 and 504 connected. The knot 503 is about a resistance 531 and a diode 505 with a knot 530 connected, wherein the cathode of the diode 505 in the direction of the knot 530 shows. The knot 530 is about a resistance 506 with the node 504 connected. The knot 530 is at the base of a pnp transistor 508 connected, the emitter of the transistor 508 is about a resistance 507 with the node 503 and the collector of the transistor 508 is with a connection 523 a module 522a connected.

5 shows several modules 522a to 522d , each with connections 523 to 528 and are each made comparable. An exemplary realization of the modules 522a to 522d is in 6 shown.

A module 518 includes a series connection of five LEDs, one module 519 includes a series connection of 12 LEDs, one module 520 includes a series of 24 LEDs and a module 521 includes a series connection of 54 LEDs. The connections 524 and 525 of the module 522a are with the module 518 , the connections 524 and 525 of the module 522b are with the module 519 , the connections 524 and 525 of the module 522c are with the module 520 and the connections 524 and 525 of the module 522d are with the module 521 connected. The cathodes of the LEDs of the modules 518 to 521 are here in the direction of the node 504 aligned.

The connection 526 of the module 522a is with the connection 523 of the module 522b , the connection 526 of the module 522b is with the connection 523 of the module 522c and the connection 526 of the module 522c is with the connection 523 of the module 522d connected. The connection 526 of the module 522d is with the node 504 connected.

The knot 503 is via a voltage source 509 (optionally via four different controllable voltage sources) with one node 529 connected.

The knot 529 is about a resistance 510 with the connection 527 of the module 522a and via a series circuit of the resistor 510 and a resistance 511 with the connection 528 of the module 522a connected. The knot 529 is about a resistance 512 with the connection 527 of the module 522b and via a series circuit of the resistor 512 and a resistance 513 with the connection 528 of the module 522b connected. The knot 529 is about a resistance 514 with the connection 527 of the module 522c and via a series circuit of the resistor 514 and a resistance 515 with the connection 528 of the module 522c connected. The knot 529 is about a resistance 516 with the connection 527 of the module 522d and via a series circuit of the resistor 516 and a resistance 517 with the connection 528 of the module 522d connected.

6 shows the internal structure of the modules 522a to 522d as well as their connections 523 to 528 ,

The connection 523 is over a diode 601 with the connection 524 connected, wherein the cathode of the diode 601 in the direction of the connection 524 shows. The connection 524 is still on a diode 602 with a knot 606 connected, wherein the cathode of the diode 602 in the direction of the knot 606 shows. The connection 523 is also connected to the drain of an n-channel mosfet 607 connected. The source connection of the mosfet 607 is with the connection 526 connected. The knot 606 is over a capacitor 610 with the connection 526 connected. The knot 606 is also about a resistance 615 with the base of an npn transistor 617 connected. The base of the transistor 617 is about a resistance 616 with the connection 526 connected.

The connection 525 is over a diode 603 with a knot 621 connected, wherein the cathode of the diode 603 in the direction of the knot 621 shows. The knot 621 is over a capacitor 609 with the connection 526 connected. The connection 525 is via a series connection of two LEDs 604 and 605 with the connection 526 connected, the cathodes of the LEDs 604 and 605 in the direction of the connection 526 demonstrate.

The knot 621 is with the collector of an npn transistor 611 connected. The emitter of the transistor 611 is about a resistance 608 with the gate terminal of the mosfet 607 connected. Furthermore, the emitter of the transistor 611 with the emitter of a pnp transistor 612 connected. The collector of the transistor 612 is with the connection 526 connected.

The knot 621 is with the emitter of a pnp transistor 613 connected. The collector of the transistor 613 is with the base of the transistor 611 , with the base of the transistor 612 and about a resistance 614 with the connection 526 connected.

The knot 621 is over a diode 620 with the collector of an npn transistor 619 connected, wherein the cathode of the diode 620 pointing in the direction of the collector. The emitter of the transistor 619 is with the emitter of the transistor 617 and about a resistance 618 with the connection 526 connected. The collector of the transistor 617 is with the base of the transistor 613 connected. The base of the transistor 619 is with the connection 527 connected and the connection 526 is with the connection 528 connected.

By way of example, the in 5 and 6 The circuit shown the following components or dimensions (resistors in ohms, capacitors in Farad): R_531 = 3.3k; R_506 = 200k, R_507 = 100; R_510 = 27k; R_512 = 47k; R_514 = 100k; R_516 = 200k; R_511 = R_513 = R_515 = R_517 = 3.3k; R_608 = 10; R_614 = 22k; R_616 = 3.3k; R_618 = 22k; C_609 = C_610 = 1μ. The resistance 615 depends on the module 522a to 522d different values, eg in module 522a 27k, in module 522b 47k, in module 522c 100k and in module 522d 200k.

In order to fulfill the above-described secondary condition (A), it may be advantageous to slightly reduce the voltage difference US _m as a comparison value to the respective LED chain voltage U _i . Thus, parasitic voltage drops Up at the decoupling diodes 601 and on the current regulator 508 be compensated. This reduction of the voltage differences US _m can be achieved by one or more voltage sources UO _m .

The voltage source 509 may, for example, a minimum voltage drop across the current regulator 104 Taxes. That's what the voltage source is for 509 For example, designed such that the current regulator 104 in each case of operation as intended (ie without power interruptions) can work. Furthermore, the mean voltage drop across the current regulator 104 preferably to minimize losses as much as possible.

Secondary condition (C) & symmetrization

4 shows based on the representation of 3 several voltage sources for symmetrizing the currents between the individual LED segments.

In contrast to 3 are in 4 the resistances 317 . 312 and 307 not directly with the node 302 connected. Instead, the resistance 317 via a voltage source 401 , the resistance 312 via a voltage source 402 and the resistance 307 via a voltage source 403 with the node 302 connected.

The voltage sources 401 to 403 are driven in response to an average of the input voltage. Such a mean value is in particular in relation to the mean (rectified) mains voltage. The voltage sources 401 to 403 are thus controlled taking into account the secondary condition (C) and cause a controlled switching delay for the LED segment m.

The voltage sources 401 to 403 can be used to control the current through the current regulator 104 to control; For example, the current regulator 104 be designed as a resistor, wherein the current through this resistor by means of the voltage sources 401 to 403 is adjustable.

Analogous to the numerical solution of the nonlinear optimization problem for the constraint condition (C) in the case of the timed circuit arrangement according to the above statements, the optimum values for the voltage sources UO _i (U _in ) can also be determined as a function of the effective input voltage U _{in, eff} .

This can be achieved, for example, by a numerical optimization, wherein an error function E _{rr is expressed} as a function of the voltages at the voltage source UO _m instead of the times t _i .

Thus, the asymmetry can be detected by the error function E _rr , for example. The error function E _rr is determined, for example, as a function of the voltages UO _m (U _in ).

The voltages UO _m (U _in ) can be adjusted as part of an optimization for all input voltages U _in such a way that the error function is minimal.

Alternatively or additionally, the error function E _{rr may be expressed} as a function of the length of the semiconductor _{light elements} (eg, the number of (respective) semiconductor light elements) and / or as a function of the voltage sources. In the context of numerical optimization, therefore, a favorable design can be determined taking into account, for example, the degrees of freedom: number of semiconductor light elements, number of segments, adjustment of voltage sources (per segment), current waveform (harmonics).

For example, in an arrangement with M LED segments M freely selectable parameters UO _m (U _in ) to optimize the constraint (C) are available.

Additional exemplary implementations

7 shows an alternative circuit arrangement 5 , An AC mains voltage 701 is over a rectifier 702 with two nodes 703 and 704 connected. The knot 703 is about a resistance 705 with a knot 759 connected. The knot 759 is over a diode 706 and a resistance 711 with the node 704 connected, wherein the cathode of the diode 706 in the direction of the knot 704 shows. The knot 759 is with the base of an npn transistor 752 connected. The emitter of the transistor 752 is about a resistance 753 with the node 704 connected.

The knot 703 is via a series circuit comprising an LED 712 , a module 707 and an LED 713 with a knot 760 connected. The module 707 includes a series connection of several LEDs, for example 54 LEDs. The knot 703 is over a capacitor 714 with the node 760 connected. The knot 703 is over a capacitor 716 with a knot 755 connected. The knot 760 is over a diode 715 with the node 755 connected, wherein the cathode of the diode 715 in the direction of the knot 755 shows. The knot 703 is with the emitter of a pnp transistor 717 connected. The collector of the transistor 717 is with the node 755 connected. The base of the transistor 717 is about a resistance 718 with the collector of an npn transistor 719 connected. The emitter of the transistor 719 is with the node 760 connected. The base of the transistor 719 is via a series connection of a resistor 720 and a diode 721 with a knot 761 connected, wherein the cathode of the diode 721 towards the base of the transistor 719 shows.

The knot 755 is via a series connection of an LED 722 , a module 708 and an LED 723 with a knot 756 connected. The module 708 includes 24 LEDs in series. The knot 755 is over a capacitor 724 with a knot 762 connected. The knot 762 is over a diode 725 with the node 756 connected, wherein the cathode of the diode 725 in the direction of the knot 756 shows. The knot 755 is over a capacitor 726 with the node 756 connected. The knot 755 is with the emitter of a pnp transistor 727 connected. The collector of the transistor 727 is with the node 756 connected. The base of the transistor 727 is about a resistance 728 with the collector of an npn transistor 729 connected. The emitter of the transistor 729 is with the node 762 connected. The base of the transistor 729 is via a series connection of a resistor 730 and a diode 731 with the node 761 connected, wherein the cathode of the diode 731 towards the base of the transistor 729 shows.

The knot 756 is via a series circuit comprising an LED 732 , a module 709 and an LED 733 with a knot 757 connected. The module 709 includes a series connection of twelve LEDs. The knot 756 is over a capacitor 734 with a knot 763 connected. The knot 756 is over a capacitor 736 with the node 757 connected. The knot 756 is with the emitter of a pnp transistor 737 connected. The collector of the transistor 737 is with the node 757 connected. The base of the transistor 737 is about a resistance 738 with the collector of an npn transistor 739 connected. The emitter of the transistor 739 is with the node 763 connected. The knot 763 is with a diode 735 with the node 757 connected, wherein the cathode of the diode 735 in the direction of the knot 757 shows. The base of the transistor 739 is via a series connection of a resistor 740 and a diode 741 with the node 761 connected, wherein the cathode of the diode 741 towards the base of the transistor 739 shows.

The knot 757 is via a series connection of an LED 742 , a module 710 and an LED 743 with a knot 758 connected. The module 710 includes a series connection of five LEDs. The knot 757 is over a capacitor 744 with a knot 764 connected. The knot 764 is over a diode 745 with the node 758 connected, wherein the cathode of the diode 745 in the direction of the knot 758 shows. The knot 758 is also connected to the collector of the transistor 752 connected. The knot 757 is over a capacitor 746 with the node 758 connected. The knot 757 is with the emitter of a pnp transistor 747 connected. The collector of the transistor 747 is with the node 758 connected. The base of the transistor 747 is about a resistance 748 with the collector of an npn transistor 749 connected. The emitter of the transistor 749 is with the node 764 connected. The base of the transistor 749 is via a series connection of a resistor 750 and a diode 751 with the node 761 connected, wherein the cathode of the diode 751 towards the base of the transistor 749 shows.

The knot 761 is via a voltage source 754 with the node 704 connected.

With regard 7 It should be noted that the cathodes of the LEDs are each in the direction of the node 704 are aligned.

By way of example, the in 7 1, the following components or dimensions (resistors in ohms, capacitors in Farad) are shown: R_705 = 200k; R_711 = 3.3k; R_753 = 100; R_720 = R_730 = R_740 = R_750 = 220k; R_718 = 220k; R_728 = 1 10k; R_738 = 56k; R_748 = 27k; C_716 = C_726 = C_736 = C_746 = 1p; C_714 = 47μ; C_724 = C_734 = C_744 = 1μ.

The capacitor 714 is comparatively large and works as a buffer capacitor for the LEDs of the module 707 as well as the LEDs 712 and 713 , It is advantageous that the capacitor 714 must be designed only for the voltage dropping at these LEDs and not for the full height of the mains voltage. Accordingly, the capacitor 714 be smaller and thus designed to save space. One option is that the capacitor 714 an electrolytic capacitor; In particular, the capacitor 714 the only electrolytic capacitor in the 7 be shown circuit. The capacitor 714 can be carried out via corresponding lines separately from the compact remaining circuit. In particular, it is possible to use the capacitor 714 as exchangeable (eg pluggable) component to provide. This ensures that if the electrolytic capacitor fails 714 This can be easily and quickly replaced and thus the circuit is functional again after a short time.

The capacitors 716 . 726 . 736 and 746 represent small parasitic capacitances, which may also be omitted in a real circuit, because such small capacity results due to the circuit structure itself.

Also the diodes 721 . 731 . 741 and 751 are optional and can be saved if necessary, if the transistors 719 . 729 . 739 and 749 are designed according to voltage or can be interpreted.

By sizing the in 7 shown circuit can be achieved that the transistor 717 operated at a switching frequency of about 100Hz; a possibly due to this switching frequency perceptible flicker is by the (buffer) capacitor 714 prevented. The transistor 727 works with a switching frequency of about 200Hz, the transistor 737 with a switching frequency of about 400Hz and the transistor 747 with a switching frequency of approx. 800Hz.

The combination of capacitor 714 and diode 715 represents a peak detector (peak detector) for the LED segment comprising the module 707 as well as the LEDs 712 and 713 Accordingly, set the capacitor 724 and the diode 725 a peak detector for the LED segment comprising the module 708 as well as the LEDs 722 and 723 , the capacitor 734 and the diode 735 a peak detector for the LED segment comprising the module 709 as well as the LEDs 732 and 733 and the capacitor 744 and the diode 745 a peak detector for the LED segment comprising the module 710 as well as the LEDs 742 and 743 represents.

The transistors 719 . 729 . 739 and 749 act as comparators. The mode of operation will be described below by way of example with reference to the lowest level for the LED segment comprising the module 710 as well as the LEDs 742 and 743 described.

The resistance 750 is in combination with the capacitor 744 designed so that the capacitor 744 even during the longest expected switch-on of the transistor 747 not completely discharged. The voltage source 754 indicates a voltage offset as a minimum voltage, eg equal to 6V, which is present at the transistor 752 should not fall below. The transistor 749 compares the voltage 6V minus the voltage at the node 758 , Turns the transistor 747 through, so will the module 710 and the LEDs 742 and 743 bridged ("shorted"). It also shifts the operating points of the remaining drive units for the other LEDs.

It should be noted that the LEDs connected in series represent one LED segment per stage. Each LED segment is controlled by a separate driver, which in the example of 7 In particular, the two transistors and the described peak detector has. The drivers are controlled by the rectified mains voltage (less by the voltage source 754 provided voltage offsets).

In 7 becomes the voltage source 754 used as a common voltage source for the multiple drive units of the LED segments. Optionally, a plurality of voltage sources may be provided, for example a voltage source for each drive unit of the LED segment.

8th shows an alternative circuit arrangement, substantially on the circuit according to 7 based and provides several voltage sources that can be used to control the individual LED segments.

An AC mains voltage 801 is over a rectifier 802 with two nodes 803 and 805 connected. The knot 803 is about a resistance 808 with a knot 859 connected. The knot 859 is about a resistance 809 with the node 805 connected. The knot 859 is at the base of an npn transistor 811 connected. The emitter of the transistor 811 is about a resistance 810 with the node 805 connected. The knot 803 is via a series connection of an LED 817 and an LED 818 with a knot 860 connected. The knot 860 is via a series connection of a module 813 and a diode 825 with a knot 856 connected, wherein the cathode of the diode 825 in the direction of the knot 856 shows. The knot 803 is over a capacitor 819 with the node 860 connected. The knot 803 is with the emitter of a pnp transistor 820 connected. The collector of the transistor 820 is with the node 856 connected. The base of the transistor 820 is about a resistance 821 with the collector of an npn transistor 822 connected. The emitter of the transistor 822 is with the node 860 connected. The base of the transistor 822 is via a series connection of a resistor 823 and a diode 824 as well as a voltage source 855 with the node 805 connected, wherein the cathode of the diode 824 towards the base of the transistor 822 shows.

The knot 856 is via a series connection of an LED 826 and an LED 827 with a knot 861 connected. The knot 861 is via a series connection of a module 814 and a diode 834 with a knot 857 connected, wherein the cathode of the diode 834 in the direction of the knot 857 shows. The knot 856 is over a capacitor 828 with the node 861 connected. The knot 856 is with the emitter of a pnp transistor 829 connected. The collector of the transistor 829 is with the node 857 connected. The base of the transistor 829 is about a resistance 830 with the collector of an npn transistor 831 connected. The emitter of the transistor 831 is with the node 861 connected. The base of the transistor 831 is via a series connection of a resistor 832 , a diode 833 and a voltage source 854 with the node 805 connected, wherein the cathode of the diode 833 towards the base of the transistor 831 shows.

The knot 857 is via a series connection of an LED 835 and an LED 836 with a knot 862 connected. The knot 862 is about a module 815 that with a diode 843 connected in series, with a node 858 connected, wherein the cathode of the diode 843 in the direction of the knot 858 shows. The knot 857 is over a capacitor 837 with the node 862 connected. The knot 857 is with the emitter of a pnp transistor 838 connected. The collector of the transistor 838 is with the node 858 connected. The base of the transistor 838 is about a resistance 839 with the collector of an npn transistor 840 connected. The emitter of the transistor 840 is with the node 862 connected. The base of the transistor 840 is via a series connection of a resistor 841 , a diode 842 and a voltage source 853 with the node 805 connected, wherein the cathode of the diode 842 towards the base of the transistor 840 shows.

It should be noted that the number of diodes 817 . 818 , which are parallel to the capacitor 819 (Correspondingly in the other segments) are arranged, for example only two. There are also other (eg different) numbers of diodes per segment possible.

The knot 858 is via a series connection of an LED 844 and an LED 845 with a knot 863 connected. The knot 863 is about a module 816 that with a diode 812 connected in series, with a node 864 connected, wherein the cathode of the diode 812 in the direction of the knot 864 shows. The knot 858 is over a capacitor 846 with the node 863 connected. The knot 858 is with the emitter of a pnp transistor 847 connected. The collector of the transistor 847 is with the node 864 connected. The base of the transistor 847 is about a resistance 848 with the collector of an npn transistor 849 connected. The emitter of the transistor 849 is with the node 863 connected. The base of the transistor 849 is via a series connection of a resistor 850 , a diode 851 and a voltage source 852 with the node 805 connected, wherein the cathode of the diode 851 towards the base of the transistor 849 shows.

The knot 864 is with the collector of the transistor 811 connected.

• – an dem Modul 813: 150V,
• – an dem Modul 814: 70V,
• – an dem Modul 815: 30V und
• – an dem Modul 816: 10V.

The modules 813 . 814 . 815 and 816 each have a series connection of LEDs. The series circuits of LEDs are in particular designed differently per module, so that at each of the modules 813 to 816 different voltages fall off. For example, the modules 813 to 816 be designed so that the following voltages drop:

• - on the module 813 : 150V,
• - on the module 814 : 70V,
• - on the module 815 : 30V and
• - on the module 816 : 10V.

With regard 8th It should be noted that the cathodes of the LEDs are each in the direction of the node 705 are aligned.

By way of example, the in 8th illustrated circuit on the following components or dimensions (resistors in ohms, capacitors in Farad): R_808 = 200k; R_809 = 3.3k; R_810 = 100; R_821 = R_830 = R_839 = R_848 = 10k; R_823 = R_832 = R_841 = R_850 = 1M; C_819 = C_828 = C_837 = C_846 = 1μ.

Other advantages:

The present operating circuit for LEDs has a high efficiency and can be manufactured at a low cost. Advantageously, it is possible to distribute the electrical power evenly or with a high degree of uniformity over the LED segments. Optionally, the power distribution can be controlled along the LED chain. The proposed solution also allows a power factor close to 1.0 and thus low or easily controllable harmonics. The circuit is centrally dimmable, e.g. via an adjustable linear regulator. Another advantage is the small installation space, since no magnetic components (throttles or similar) are required. Also from this follows a good electromagnetic compatibility.

LIST OF REFERENCE NUMBERS

101-103

LED segment

104

current regulator

105

AC line voltage

106

rectifier

SW ₁ to SW ₃

(electronic) switch

C1 to C3

capacitor

D1 to D3

(Decoupling) diode

301-302

node

303

comparator

304-307

resistance

308

comparator

309-312

resistance

313

comparator

314-317

resistance

401-403

voltage source

501

AC line voltage

502

rectifier

503-504

node

505

diode

506-507

resistance

508

PNP transistor

509

voltage source

510-517

resistance

518-521

Module (LED segment or part of an LED segment)

522a-522d

Module (see 6 )

523-528

Connections of the module 522a - 522d

529-530

node

531

resistance

601-603

diode

604-605

LED

606

node

607

Mosfet

608

resistance

609-610

capacitor

611

npn transistor

612-613

PNP transistor

614-616

resistance

617

npn transistor

618

resistance

619

npn transistor

620

diode

621

node

701

AC line voltage

702

rectifier

703-704

node

705

resistance

706

diode

707-710

module

711

resistance

712-713

LED

714

capacitor

715

diode

716

capacitor

717

PNP transistor

718

resistance

719

npn transistor

720

resistance

721

diode

722-723

LED

724

capacitor

725

diode

726

capacitor

727

PNP transistor

728

resistance

729

npn transistor

730

resistance

731

diode

732-733

LED

734

capacitor

735

diode

736

capacitor

737

PNP transistor

738

resistance

739

npn transistor

740

resistance

741

diode

742-743

LED

744

capacitor

745

diode

746

capacitor

747

PNP transistor

748

resistance

749

npn transistor

750

resistance

751

diode

752

npn transistor

753

resistance

754

voltage source

755-764

node

801

AC line voltage

802

rectifier

803

node

805

node

808-810

resistance

811

npn transistor

812

diode

813-816

module

817-818

LED

819

capacitor

820

PNP transistor

821

resistance

822

npn transistor

823

resistance

824-825

diode

826-827

LED

828

capacitor

829

PNP transistor

830

resistance

831

npn transistor

832

resistance

833-834

diode

835-836

LED

837

capacitor

838

PNP transistor

839

resistance

840

npn transistor

841

resistance

842-843

diode

844-845

LED

846

capacitor

847

PNP transistor

848

resistance

849

npn transistor

850

resistance

851

diode

852-855

voltage source

856-864

node

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102010040266 A1 [0007]

Claims (20)

Circuit for driving semiconductor light elements, With at least two segments connected in series, each having a plurality of semiconductor light elements connected in series, Wherein the semiconductor light elements are different in at least two of the segments, Each having a driver for driving a segment, wherein the driver has at least one electronic switch, by means of which the segment can be bridged, - In which the drivers are coupled via at least one voltage source with the rectified mains voltage. The circuit of claim 1, wherein each driver is coupled to the rectified mains voltage via a separate voltage source. Circuit according to one of the preceding claims, in which the at least one voltage source can be realized by means of: - a voltage divider; An auxiliary power source; - a zener diode. Circuit according to one of the preceding claims, in which the voltage source can be controlled as a function of an average value of the rectified mains voltage. Circuit according to one of the preceding claims, wherein the drivers are supplied with a rectified mains voltage. A circuit as claimed in any one of the preceding claims, wherein at least two of the segments comprise semiconductor light elements which are at least partially different in their forward voltages, colors, sizes, shapes and / or numbers. A circuit according to any one of the preceding claims, wherein the driver comprises a comparison element. Circuit according to one of the preceding claims, in which the segments are connected in series with a current regulator. A circuit according to claim 8, wherein the current regulator is controllable by means of dimming. Circuit according to one of claims 8 or 9, wherein the current regulator comprises a resistive element or a linear regulator. A circuit as claimed in any one of the preceding claims, wherein the segment having the largest forward voltage has at least twice as much forward voltage as the segment having the lowest forward voltage. Circuit according to one of the preceding claims, in which the electronic switch of the driver is active at a switching frequency which has at least twice the mains frequency or a multiple of the mains frequency. A circuit as claimed in any one of the preceding claims, wherein at least one of the drivers comprises a capacitor arranged in parallel with semiconductor light elements of the segment to which the driver is associated. The circuit of claim 13, wherein the capacitor is disposed in or together with the driver driving the segment with the largest forward voltage. Circuit according to one of claims 13 or 14, wherein the capacitor is designed to be interchangeable via a detachable connection. A circuit according to any one of claims 13 to 15, wherein at least one of the drivers comprises a series connection of a capacitor and a diode, said series connection being arranged parallel to the semiconductor light elements of the segment which the driver drives. Circuit according to one of the preceding claims, wherein at least one decoupling diode is arranged between each two segments. A circuit according to any one of the preceding claims, wherein means is provided for mixing the light provided by a plurality of segments. Circuit according to one of the preceding claims, - in which the driver has an electronic short-circuit switch ( 717 ), by means of which the segment assigned to the driver can be short-circuited, - the base terminal of the short-circuiting switch ( 717 ) via a first current-limiting element ( 718 ) with the collector terminal of an electronic comparison switch ( 719 ), the emitter terminal of the comparison switch ( 719 ) is connected to a terminal of the segment to which the driver is assigned, - the base terminal of the comparison switch ( 719 ) with one pole of the rectified AC line voltage ( 701 ) connected is. Lamp, luminaire or lighting system with a circuit according to one of claims 1 to 19.

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