EP2667687B1 - Operation control device and method for operating a lighting assembly - Google Patents

Description

The present invention relates to an operation control device and a method for operating a lighting device. In particular, the luminous means arrangement has a series connection of a plurality of light-emitting diodes or consists of such a series circuit. By way of the operating control device, it is also possible to operate a plurality of such illuminant arrangements, that is to say, for example, a plurality of series connections of light-emitting diodes.

When operating the light source, such as light-emitting diodes, there is a need to be able to adjust the brightness of the lamps. Especially at high dimming levels and low brightness often causes a flicker of the bulbs.

DE 10 2010 002 072 A1 For example, to increase the dynamic range of light emitting diodes, it is proposed to provide an adjustable resistor in series with a control switch driven by a pulse width modulated control signal. The current through the LEDs can thereby be pulse width modulated by the control switch. On the other hand, the amplitude of the current can be specified by the adjustable resistor, so that two parameters for brightness adjustment are available. Thus, the amplitude and the pulse width of the current are adjusted. A similar procedure also describes DE 10 2010 000 672 A1 ,

Out EP 1 576 858 B1 is an operation control device and a method for operating a lighting device from a series connection of light-emitting diodes known. The aim of the device described therein is to omit the control switch provided in series with the lamp arrangement. For this purpose, the operation control device has a converter controlled by a switching signal. The signal used to drive the transducer to provide an output current to the lamp assembly at the output of the transducer is combined with the pulse width modulated control signal used to adjust the brightness. The higher-frequency switching signal is generated only when the control signal serving to control the brightness has a predetermined digital value, for example the value "1". The switching signal is equal to "0" when the control signal assumes its other state, for example corresponds to the digital value "0". By combining the switching signal with the control signal, the control switch can be omitted. The converter, which provides the current for the luminous means arrangement, is, so to speak, operated only in phases analogous to the previously used pulse-width-modulated control signal for adjusting the brightness.

Out WO 2011/039678 A1 For example, a method and an operation control device for operating a lighting device are known. An input circuit supplies a DC input voltage, the input side of which is applied to a controlled by a control device based on a switching signal converter which provides an output current and an output voltage at its output, wherein the lamp assembly is connected to the output of the converter. To the output, an output capacitor is connected in parallel to the lamp arrangement, to which the output voltage is applied. To control the brightness of the luminous means arrangement, the control device controls a control switch which is connected in series with the luminous means arrangement is switched. The controller may drive the converter with the control switch open to prevent the output capacitor from discharging. This should keep output current and output voltage constant.

The operating control devices known from the prior art do not always operate satisfactorily at high dimming levels. There may be flicker effects. For example, the DALI standard requires a pulse width of 0.1% for the smallest possible brightness (DALI = 1) for a pulse width modulated control signal. The DALI standard defines a brightness value of 0.1% of the maximum brightness for DALI = 1. When driving light sources where the brightness can be reduced by pulse width modulation, there is an exponential relationship between the duty cycle and the brightness. As a result, the control signal is also driven with 0.1% duty cycle. At usual frequencies for the pulse width modulation of over 100 Hz and up to 400 Hz, this leads to very short turn-on times. Since the luminous flux does not rise infinitely steeply by the luminous means arrangement when switched on, the low pulse width can lead to an approximately triangular current profile through the luminous means arrangement. However, this in turn means that the desired luminous flux and thus the desired brightness can no longer be set as intended via the pulse width modulation.

It can therefore be regarded as an object of the present invention to provide an operating control device and a method for operating a lighting arrangement which reduces flickering effects even at low pulse widths of a brightness of the lighting arrangement adjusting pulse width modulated control signal avoids.

This object is achieved by an operating control device having the features of claim 1 and a method having the features of claim 8.

According to the invention, the operation control device has an input circuit for providing a DC input voltage. The input circuit can be formed, for example, by a rectifier circuit which generates the DC input voltage from a mains voltage. The DC input voltage is provided to a converter, for example a buck converter, a step-up converter or a flyback converter, which provides an output current at its output. The light-emitting device is arranged at the output of the buck converter. A controller controls the buck converter by means of a switching signal to adjust the output current.

Parallel to the lamp arrangement, an output capacitor is connected to the output of the buck converter, to which the output voltage is applied. In series with the lamp assembly is a control switch. This is opened and closed by a preferably pulse-width-modulated control signal of the control device for adjusting the brightness of the lamp arrangement.

The control device is set up to control the buck converter with the control switch open in such a way that the output capacitor charges during a charging period, which ends in particular with the next closing of the control switch. During the charging period, no luminous flux flows through the lamp arrangement, since the control switch is open. Before switching on the lamp current, the output capacitor charged. As the charging time increases, the capacitor voltage and output current at the buck converter increase. The control device controls the charging time period or the start of the charging period such that the output current at the output of the buck converter before the closing of the control switch as possible corresponds to the luminous flux through the lamp assembly. Additionally or alternatively, the control device determines the charging time duration such that the capacitor voltage at the output capacitor at the time of closing the control switch corresponds as far as possible to the illuminant voltage at the illuminant arrangement when the control switch is closed. The control device can change the charging time duration by measuring the current profile and / or the voltage profile at the lamp arrangement in order to obtain the smallest possible change in the current and / or the voltage at the lamp arrangement when the control switch is closed. The current increase phase of the output current thus takes place, at least partially, even before the closing of the control switch.

This has the consequence that even at very short pulse widths of the pulse width modulated control signal already at the time of closing the control switch, a sufficiently large output current at the output of the buck converter is available and therefore a high dimming level can be set accurately and without flickering the lamp assembly. The invention is therefore suitable and provided in particular for the operating states in which the dimming level is above a predetermined limit value, that is to say for small brightnesses of the lighting device arrangement. This limit value can be predetermined by the fact that the rise time of the luminous flux is smaller down to a predetermined desired value and in particular by at least a factor of 1.5 to 2 is smaller than that corresponding to the dimming level Pulse width.

Preferably, the frequency of the pulse width modulated control signal is smaller by several orders of magnitude than the switching frequency of the switching signal with which the buck converter is driven. For example, there may be three orders of magnitude between these two frequencies. In a preferred embodiment, the frequency of the pulse width modulated control signal is about 100 to 200 Hz and the frequency of the switching signal about 300 kHz.

• die Zeitdauer des Ladezeitraums,
• den Tastgrad des Wandlers während des Ladezeitraums,
• den Ausgangswert der Spannung am Kondensator bzw. am Ausgang des Wandlers zu Beginn des Ladezeitraums.

In one embodiment, means for measuring the luminous flux are provided by the luminous means arrangement and / or means for measuring the illuminant voltage applied to the illuminant arrangement. The measured values can be transmitted to the control device for evaluation. On the basis of the result of the evaluation, the control device adapts at least one and preferably a plurality of parameters in order to change the luminous flux and / or the luminous flux and in particular to regulate it to the assigned desired value. The controller may set one or more of the following parameters:

• the duration of the loading period,
• the duty cycle of the transducer during the charging period,
• the output value of the voltage at the capacitor or at the output of the converter at the beginning of the charging period.

To regulate current and voltage, at least two of the three parameters mentioned are set. The parameters are determined and set in such a way that at the switching time of the control switch from the open to the closed state, the change of the output current and / or the output voltage is as small as possible and preferably equal to zero.

Because of the high frequencies and the short periods in which the luminous flux increases to its desired value, the controller is not fast enough to perform a regulation in the strict sense. Therefore, it is advantageous for the measured values of the luminous flux and / or the luminous flux to be measured over a certain period of time and stored in a memory before the control device evaluates the measured values in order to check whether the charging period has to be adjusted. The measurement and storage of the measured values can take place over several periods of the control signal before an evaluation takes place.

1. 1. Ist der Leuchtmittelstrom und die Ausgangsspannung beim Schließen des Steuerschalters zu niedrig, wird zunächst der Tastgrad des Schaltsignals des Wandlers erhöht und wenn dieser bereits 100% beträgt, wird die Zeitdauer des Ladezeitraums vergrößert.
2. 2. Wenn der Ausgangsstrom beim Schließen des Steuerschalters zu groß ist, wird der Ladezeitraum verkürzt.
3. 3. Ist dadurch die Spannung beim Schließen des Steuerschalters zu niedrig, wird der Anfangswert der Ausgangsspannung am Ausgangskondensator zu Beginn des Ladezeitraums erhöht.
4. 4. Ist die Ausgangsspannung beim Schließen des Steuerschalters zu groß, wird der Anfangswert der Ausgangsspannung durch gezieltes Entladen des Ausgangskondensators vor Beginn des Ladezeitraums verringert.
5. 5. Ist der Leuchtmittelstrom beim Schließen des Steuerschalters zu klein, wird der Ladezeitraum vergrößert. Sollte umgekehrt der Leuchtmittelstrom zu groß sein, kann der Ladezeitraum verkürzt und/oder der Tastgrad des Schaltsignals des Wandlers verringert werden.
6. 6. Steigt der Leuchtmittelstrom nach dem Schließen des Steuerschalters weiter an, wird der Tastgrad des Schaltsignals des Wandlers nach dem Ende des Ladezeitraums verringert. Umgekehrt wird dieser Tastgrad erhöht, wenn der Leuchtmittelstrom IL nach dem Schließen des Steuerschalters sinkt.

Preferably, the measured time profile of the luminous flux and / or the measured time profile of the luminous flux is compared with an associated setpoint value. If the luminous flux and / or the illuminant voltage at the time of closing the control switch after expiration of the charging period is too small or too large, one or more of the following measures can be performed by the control device:

1. 1. If the luminous flux and the output voltage when closing the control switch is too low, first the duty cycle of the switching signal of the converter is increased and if this is already 100%, the duration of the charging period is increased.
2. 2. If the output current is too large when the control switch is closed, the charging time will be shortened.
3. 3. Is this the voltage when closing the control switch too low, the initial value of the output voltage at the output capacitor is increased at the beginning of the charging period.
4. 4. If the output voltage when closing the control switch is too large, the initial value of the output voltage is reduced by deliberately discharging the output capacitor before the beginning of the charging period.
5. 5. If the lamp current when closing the control switch is too small, the charging period is increased. Conversely, should the luminous flux be too large, the charging period can be shortened and / or the duty cycle of the switching signal of the converter can be reduced.
6. 6. If the luminous flux continues to increase after closing the control switch, the duty cycle of the switching signal of the converter is reduced after the end of the charging period. Conversely, this duty cycle is increased when the luminous flux IL decreases after closing the control switch.

The voltage applied to the output of the converter output voltage or the capacitor voltage of the output capacitor can be changed as a parameter by the control unit for adjusting the output current or the output voltage. It depends on the value of the output voltage at the output capacitor at the beginning of the charging period. At the time of switching off the lamp arrangement of the output capacitor is charged to the lamp voltage. In the meantime, to adjust the voltage at the output capacitor, the output capacitor has to be discharged: either passively via an existing measuring device, for example a voltage divider, or active via a reverse operation of the converter.

Preferably, the switching signal generated by the control device for controlling the converter does not change its state when the control switch is open outside and / or within the charging time period. During the charging period, the capacitor can thereby be charged continuously and at least partially discharged outside the charging period via the converter or a measuring device. As a measuring device for measuring the voltage, for example, a voltage divider may be connected to ground. A certain discharge current from the output capacitor always flows across the voltage divider. As an alternative to this embodiment, it is also possible to charge or discharge the output capacitor when the control switch is open via the control of the converter.

In a preferred embodiment, the input circuit is formed by a rectifier circuit which generates the DC input voltage from a mains voltage. As a rectifier circuit can serve, for example, a flux converter, a flyback converter or a combination thereof.

The rectifier circuit can also provide a first DC input voltage and a second DC input voltage with different amounts. In this embodiment, only the difference between the first DC input voltage and the second DC input voltage is applied to the two series-connected controlled switching means of the converter. By this design, switching losses can be reduced to the switching means of the buck converter.

• Figur 1 ein Blockschaltbild einer ersten Ausführungsform einer Betriebssteuervorrichtung zum Betreiben einer Leuchtmittelanordnung,
• Figur 2 ein Ausführungsbeispiel eines Tiefsetzstellers für die Betriebssteuervorrichtung nach Figur 1,
• Figur 3 einen schematischen, beispielhaften zeitlichen Verlauf des Leuchtmittelstroms durch die Leuchtmittelanordnung sowie das Steuersignal zum Ansteuern des Steuerschalters zur Einstellung der Helligkeit der Leuchtmittelanordnung gemäß dem Stand der Technik,
• Figur 4 einen schematischen beispielhaften zeitlichen Verlauf des Steuersignals zur Ansteuerung des Steuerschalters, des Schaltsignals zur Ansteuerung des Tiefsetzstellers, des Ausgangsstroms des Tiefsetzstellers sowie der Ausgangsspannung des Tiefsetzstellers beim Ausführungsbeispiel gemäß Figur 1 der Betriebssteuervorrichtung,
• Figuren 5A bis 5D jeweils einen beispielhaften Verlauf des Leuchtmittelstromes, des Ausgangsstromes und der Ausgangsspannung während und nach dem Ladezeitraum zur Veranschaulichung der Erfindung und
• Figur 6 ein Blockschaltbild eines zweiten Ausführungsbeispiels einer Betriebssteuervorrichtung.

Advantageous embodiments of the invention will become apparent from the dependent claims and the description. The drawing is to be used as a supplement. Hereinafter, embodiments of the invention will be explained with reference to the accompanying drawings. Show it:

• FIG. 1 FIG. 2 a block diagram of a first embodiment of an operating control device for operating a lighting arrangement, FIG.
• FIG. 2 an embodiment of a buck converter for the operation control device according to FIG. 1 .
• FIG. 3 a schematic, exemplary time profile of the luminous flux through the luminous means arrangement and the control signal for driving the control switch for adjusting the brightness of the luminous arrangement according to the prior art,
• FIG. 4 a schematic exemplary timing of the control signal for driving the control switch, the switching signal for controlling the buck converter, the output current of the buck converter and the output voltage of the buck converter in the embodiment according to FIG. 1 the operating control device,
• FIGS. 5A to 5D each an exemplary course of the luminous flux, the output current and the output voltage during and after the charging period to illustrate the invention and
• FIG. 6 a block diagram of a second embodiment of an operation control device.

In FIG. 1 the block diagram of an embodiment of an operation control device 10 is shown. The operating control device 10 is used to operate a lighting arrangement 11. In the exemplary embodiment, the lighting arrangement 11 has at least one series connection of a plurality of light sources and preferably of a plurality of light emitting diodes 12. In FIG. 1 two light emitting diodes 12 are shown, wherein the number depending on the application can also be larger or smaller.

The operation control device 10 has an input circuit 15 which provides an input DC voltage UE. The input DC voltage UE can be smoothed via an input capacitor CE. In the exemplary embodiment, the input circuit 15 is a rectifier circuit 16 which generates a rectified input DC voltage UE from a mains voltage UN.

The input DC voltage UE is on the input side to a converter, which is formed in the embodiment described below by a buck converter 17. Instead of a buck converter 17 and a boost converter, a flyback converter or other converter can be used.

An embodiment of the buck converter 17 is in FIG. 2 illustrated. The DC input voltage UE is applied to a series connection of a controlled first switching means 18 and a controlled second switching means 19. The first switching means 18 is connected to the positive potential of the input DC voltage UE, while the second switching means 19 is connected to ground GND. The junction 20 between these two switching means 18, 19 is connected via an inductance L to the output 21 of the buck converter 17. The two controlled Switching means 18, 19 are controlled via a switching signal S, wherein one of the two switching means 18 or 19 is closed and the respective other switching means 19 and 18 is opened. The inductance L is therefore connected either via the second switching means 19 to ground GND or via the first switching means 18 to the positive potential of the Eingansgleichspannung UE. The switching signal S is generated by a control device 22.

Between the output 21 and the ground GND an output capacitor CA is connected. At the output capacitor CA is the output voltage UA of the buck converter 17, which corresponds to the capacitor voltage. The output 21 of the buck converter is also connected to the lamp assembly 11. In series with the lamp arrangement 11, a control switch 23 controlled by the control device 22 by means of a control signal P is arranged. In addition, in the first embodiment, an ohmic resistor R is connected in series with the lamp assembly 11 and the control switch 23.

In the exemplary embodiment, the output voltage UL is measured and transmitted to the control device 22. For this example, serve an unillustrated connected to the output 21 voltage divider. The output voltage UA corresponds to the luminous flux UL when the voltage drop across the ohmic resistor R is neglected. The illuminant voltage UL corresponds, for example, approximately to the output voltage UA.

Furthermore, the luminous flux IL is measured and transmitted to the control device 22. As an alternative, only one of these two measured values can also be detected and transmitted to the control device 22. For detecting the luminous flux IL, for example, the voltage drop measured at the ohmic resistance R.

The control device 22 is also transmitted a dimming signal D. The dimming signal D indicates which brightness of the lighting device 11 is to be set. Based on the dimming signal in the embodiment, the pulse width of the pulse width modulated control signal P and thus the effective value of the luminous flux IL via the control switch 23 is set, as shown schematically with reference to FIG. 3 is illustrated.

FIG. 3 shows an example of a time course of the control signal P for driving the control switch 23 in the control of the prior art. If this control signal P has the state "1", the control switch 23 is closed. If this control signal P has the state "0", then the control switch 23 is open. Depending on the switching state of the control switch 23, and thus of the control signal P, a luminous flux IL is established by the luminous means arrangement 11. If the control signal P has a rising edge from 0 to 1, then the luminous flux IL rises during a current increase phase T0 to approximately to a desired value Isoll. Due to the switching of the buck converter and the dimensioning of the LC low pass, the output current IA provided by the buck converter 17 fluctuates (so-called "ripple"), so that the luminous flux IL fluctuates around its nominal value Isoll following the current increase phase T0. If a falling edge occurs in the control signal P, the luminous flux IL drops to zero.

This in FIG. 3 illustrated behavior is then no problem if the pulse width W, during which the control signal P has the value "1" is significantly greater, for example, at least four to five times greater than that Current increase phase T0. At very high dimming levels, if only a low brightness is to be set for the light-emitting device 11, flicker effects can occur, however, because a falling edge of the control signal P already occurs again before or shortly after the light-flux IL reaches the setpoint Isoll in FIG. 3 is schematically illustrated by the dot-dashed control waveform. This would lead to a triangle-like shape of the luminous flux IL. A set by pulse width modulation brightness can not be precisely adjusted in this way, because during the turn-on of the control switch 23, no approximately constant luminous flux IL, but only a rising edge of the luminous flux IL occurs, which drops again after opening the control switch 23.

This problem is solved by the operation control device 10 according to the invention or the method according to the invention ( FIG. 5 ) Fixed. The principle of the invention will be described with reference to the schematic representations in FIG FIG. 4 explained. As in FIG. 4 Let it be assumed that, at a first time t1, the control signal P has a rising edge and the control switch 23 is closed. After this first time t1, the control device 22 controls the switching means 18, 19 of the buck converter with a predetermined switching frequency via the switching signal S, so that adjusts the output current IA corresponding to the current flowing through the lamp assembly 11 light source IL at the output of the buck converter 17.

The input DC voltage UE is applied across the inductance L and the output capacitor CA. It is assumed that at the beginning of the charging period ΔT at the initial time t0 = t1 - .DELTA.T the output current IA of the buck converter the output value I0 and the output voltage UA have the output value U0. During the charging period ΔT, the output voltage UA, that is to say the capacitor voltage at the output capacitor CA, increases. Also, the output current IA increases. Ideally, the charging period .DELTA.T is selected so that at the first time t1, at which the control switch 23 is closed, the output voltage UA of the lamp voltage UL when the switch 23 is closed and / or the output current IA flowing through the lamp assembly 11 when the switch 23 is closed Illuminant current IL corresponds. This ideal case is in the FIGS. 4 and 5D shown. The output current IA and the output voltage UA ideally have no jump in closing the control switch 23 at the first time t1. Regardless of the pulse width W of the control signal P, the luminous flux IL or the luminous flux UL are already sufficiently large at the time of closing the control switch 23 to be able to adjust the brightness of the luminous arrangement 11. The current increase phase T0 of the output current IA is, so to speak, brought forward and takes place even before the closing of the control switch 23. Regardless of the pulse width W can therefore be done via the pulse width modulation accurate brightness control of the lamp assembly 11.

• Der Ausgangsstrom IA des Tiefsetzstellers 17 soll dem Sollwert des Leuchtmittelstroms IL entsprechen und
• die Ausgangsspannung UA, die am Ausgangskondensator CA anliegt, soll der Leuchtmittelspannung UL bei eingeschalteter und mithin stromdurchflossener Leuchtmittelanordnung 11 entsprechen.

At the first time t1, the following specifications are to be fulfilled:

• The output current IA of the buck converter 17 should correspond to the desired value of the luminous flux IL and
• the output voltage UA, that at the output capacitor CA is applied, the illuminant voltage UL with switched on and thus current-carrying lamp assembly 11 correspond.

Then, when the lighting device 11 is turned on at the first time t1, the output current IA, which has previously charged the output capacitor CA, flows through the lighting device 11.

• die Dauer eines Ladezeitraums ΔT unmittelbar vor dem ersten Zeitpunkt t1 zum Aufladen des Ausgangskondensators CA,
• der erste Tastgrad G1 des Schaltsignals S während des Ladezeitraums ΔT;
• Der Anfangswert U0 der Ausgangsspannung UA am Ausgangskondensator CA zu Beginn der Ladezeitraums ΔT.

The measured values transmitted to the control device 22, which describe the instant and the respective value of the current and the voltage at the output 21 of the converter or at the illuminant arrangement 11, can be stored in a memory 24 before the evaluation. In order to meet the above-specified specifications for the control, the following parameters are varied or set in the exemplary embodiment by the control device 22 as a function of the evaluation result:

• the duration of a charging period ΔT immediately before the first time t1 for charging the output capacitor CA,
• the first duty G1 of the switching signal S during the charging period ΔT;
• The initial value U0 of the output voltage UA at the output capacitor CA at the beginning of the charging period ΔT.

In addition, the second duty cycle G2 of the switching signal S can also be varied after the end of the charging period ΔT when the control switch 23 is closed in order to set the luminous flux IL.

The initial value U0 of the output voltage UA at the output capacitor CA can be set by deliberately discharging before the beginning of the charging period ΔT. In a step-down converter 17 or another converter used in place of the step-down converter 17 with two controlled switching means 18, 19, an active, targeted discharging of the output capacitor CA can take place by reverse operation, so that its voltage at the beginning of the charge period ΔT has the desired initial value U0. Alternatively or additionally, a discharge of the output capacitor CA via a measuring device for measuring the output voltage UA done. As a measuring device can serve, for example, a voltage divider. A certain discharge over this voltage divider always takes place. To vary this discharge via a voltage divider, for example, one of the two voltage divider resistors to increase the discharge current from the output capacitor CA can be bridged by a suitable controllable switching means.

The output voltage UA at the output capacitor CA is known at the beginning of the charging period ΔT. The voltage applied to the lamp assembly 11 lamp voltage UL with the control switch closed 23 and in the conductive state of the lamp assembly 11 is known. A regulation of the transient response upon closing of the control switch 23 is not possible because this transient process takes place in a much too short time, for example, within about 40 microseconds. During the first startup, therefore, a setting is specified by the control device 22, which prevents the output voltage UA at the output capacitor CA when closing the control switch 23 exceeds the light source voltage UL, which is applied to the light-emitting device 11 during flow of a luminous flux IL. To set the mentioned parameters by the Control device 22 evaluates this the time course of the luminous flux IL and the light source voltage UL. It depends not only on the amount, but also on the time course of the voltage and the current at the lamp assembly 11. Based on FIGS. 5A to 5D the process is exemplified.

The starting time t0 indicates the start of the charging period ΔT. At the output time t0, the output capacitor CA is charged. At the first time t1, the luminous flux IL should reach the setpoint Isoll. As in FIG. 5A shown by way of example, the luminous flux IL increases too late or too slow and also does not reach the setpoint Isoll. The control device 22 therefore increases the time duration of the charging period ΔT and increases the first duty cycle G1 of the switching signal S during the charging period. Since the luminous flux IL tends to decrease after reaching the breakdown voltage of the luminous means arrangement 11, the second duty cycle G2 of the switching signal S is also increased after the first time t1.

By changing these parameters, the example given in FIG FIG. 5B illustrated situation. The luminous flux IL is still smaller than the desired value Isoll at the first time t1 and only rises after this first time t1. After reaching the breakdown voltage of the lamp arrangement 11, the luminous flux IL tends to increase, so that the second duty cycle G2 of the switching signal S is slightly reduced again by the control device 22. The control device 22 increases in the embodiment, the time duration of the charging period .DELTA.T again. Also, the first duty cycle G1 of the switching signal S can be further increased, unless it is already set to G1 = 1 (corresponds to 100%) is.

After this renewed correction by the control device 22 results for the next switching on the lamp assembly 11 in the example, the in FIG. 5C illustrated situation. During the charging period .DELTA.T the output current IA increases too much via the inductance L. The time duration of the charging period ΔT is therefore reduced by the control device 22. Assuming that the initial value U0 of the output voltage UA at the output capacitor CA could not be changed at the output time t0, then an optimum would have been reached. According to the invention, the initial value U0 can be adapted by deliberately discharging the output capacitor CA before the start of the charging period ΔT. In this case, the initial value U0 is increased to match the output voltage UA at the time of closing the control switch 23 to the charging period ΔT shortened by the controller 22 because of the excessively high luminous flux IL.

Finally, by iteratively changing the parameters in FIG. 5D reached situation shown, wherein the luminous flux IL after the end of the charging period .DELTA.T when closing the control switch 23 corresponds to the setpoint Isoll and also maintains this setpoint. The output voltage UA at the first time t1 corresponds to the luminous means voltage UL when the luminous means arrangement 11 is switched on.

• Ist der Leuchtmittelstrom IL und die Ausgangsspannung UA zum ersten Zeitpunkt t1 beim Einschalten des Steuerschalters 23 zu niedrig, wird zunächst der erste Tastgrad G1 des Schaltsignals S erhöht und wenn dieser bereits 100% beträgt, wird die Zeitdauer des Ladezeitraums ΔT vergrößert.

The control device 22 has the following setting options by evaluating the time profile of the luminous flux IL and the luminous means voltage UL:

• Is the luminous flux IL and the output voltage UA is too low at the first time t1 when the control switch 23 is turned on, the first duty cycle G1 of the switching signal S is initially increased, and if this is already 100%, the time duration of the charging period ΔT is increased.

If the output current IA is too large at the time t1, the charging period ΔT is shortened. If the voltage at time t1 is too low as a result, the initial value U0 of the output voltage UA at the output capacitor CA is increased at the beginning of the charging period ΔT.

If the output voltage UA is too high at the first time t1, the initial value U0 of the output voltage UA is reduced by deliberately discharging the output capacitor CA before the beginning of the charging period ΔT. If the luminous flux IL is too small at the first time t1, the charging period ΔT is increased. Conversely, should the luminous flux IL be too large at the first time t1, the charging period .DELTA.T can be shortened and / or the first duty cycle G1 of the switching signal S can be reduced.

If the luminous flux IL continues to increase after the first time t1, the second duty cycle G2 of the switching signal S is reduced after the first time t1. Conversely, this second duty cycle G2 is increased after the first time t1, when the luminous flux IL decreases after the first time t1.

In FIG. 6 a second embodiment of an operation control device 10 is illustrated. Matching parts with the first embodiment according to FIG. 1 have the same reference numerals. In that regard, reference is made to the above description. Only the differences are explained below.

In contrast to the first exemplary embodiment, the input circuit 15 provides a first DC input voltage UE1 and a second DC input voltage UE2 having different DC voltage values. The first DC input voltage UE1 is applied to a series connection of a first input capacitor CE1 and a second input capacitor CE2. The voltage at the second input capacitor CE2 corresponds to the second input direct voltage UE2, which is therefore smaller than the first input direct voltage UE1. Both input DC voltages UE1, UE2 are positive. The voltage difference between these two DC input voltages UE1, UE2, ie the voltage at the first input capacitor CE1, is applied to the series connection of the two controlled switching means 18, 19. When the first switching means is closed, the inductance L is connected to the potential corresponding to the first input direct voltage UE 1. When the second switching means 19 is closed, the inductance L is connected to the potential of the second input direct voltage UE2. The voltage difference between the two input DC voltages UE1, UE2 can be for example 2 or 3 volts. Thus, only the voltage difference between the two input DC voltages UE1, UE2 is present at the respectively open switching means 18 or 19 of the buck converter 17. As a result, the switching losses when switching the switching means 18, 19 are significantly reduced. Incidentally, the second embodiment corresponds to FIG. 6 the first embodiment, so that reference is made to the above description.

Operating the buck converter 17 with two input DC voltages UE1, UE2 as in FIG. 6 represented and as described above can also be realized independently of the remaining operation of the operation control device become. This is an independent invention idea to see.

The invention relates to a method and an operating control device 10 for operating a lamp arrangement 11, which in particular has a series connection of light-emitting diodes 12. The operating control device 10 has a buck converter 17, which is controlled by a control signal 22 via a switching signal S and provides an output current IA at its output 21. At this output 21, both the lamp assembly 11, and an output capacitor CA is connected. A control switch 23 is controlled via a pulse width modulated control signal P by the controller 22 and is in series with the lamp assembly 11. Before closing the control switch 23 is charged in a charging time .DELTA.T the Ausgangskondenstor CA and the output current IA increases. As a result, the current increase phase T0 is already carried out before the closing of the control switch 23, so that even with small pulse widths W of the control signal P, flicker effects of the illuminant arrangement 11 are avoided.

LIST OF REFERENCE NUMBERS

10

Operation control device

11

Lamp positioning

12

led

15

input circuit

16

Rectifier circuit

17

Buck converter

18

first switching means

19

second switching means

20

junction

21

output

22

control device

23

control switch

24

Storage

CE

input capacitor

CE1

first input capacitor

CE2

second input capacitor

CA

output capacitor

D

dimming signal

G1

first duty cycle

G2

second duty cycle

IL

Lamp power

isoll

Current setpoint

IT

tolerance

L

inductance

P

control signal

R

Ohmic resistance

S

switching signal

S1 to S7

steps

t0

Start time

t1

first time

.DELTA.T

Charging period

T0

Current rise phase

U0

output value

UA

output voltage

UE

DC input voltage

UE1

first DC input voltage

UE2

second DC input voltage

UL

Lamp voltage

W

pulse width

Claims (8)

1. Operation control device (10) for operating a lighting arrangement (11),

   - with an input circuit (15) for provision of an input direct current voltage (UE),

   - with a control device (22),

   - with a converter (17) which is controlled by the control device (22) using a switching signal (S), and at which the input DC voltage (UE) is present on the input side and which provides an output current (IA) and an output voltage (UA) at its output (21), wherein the lighting arrangement (11) is connected to the output (21) of the converter (17),

   - with an output condenser (CA) at which the output voltage (UA) is applied,

   - with means for measuring the lighting current (IL) through the lighting arrangement (11),

   - and with a control switch (23) which is controlled by the control device (22) for adjusting the brightness of the lighting arrangement (11) and which is connected in series with the lighting arrangement (11),

   characterised in that

   - the control device (22) predefines a nominal value for the output voltage (UA) when the control switch (23) is opened which is equal to the lighting voltage (UL) when the control switch (23) is closed, and a nominal value (Isoll) for a lighting current (IL) when the control switch (23) is closed,

   - that means for measuring the output voltage (UA) present at the output of the converter are present, and the measured value for the lighting current (IL) and the measured value for the output voltage (UA) are transmitted to the control device (22) for analysis, wherein the control device (22) is configured to store the measured values in a memory (24) before analysis,

   - that the control device (22) compares the stored measured value for the lighting current (IL) and the stored measured value for the output voltage (UA) with the respective assigned nominal value (Isoll, UL),

   - and that the control device (22) is configured to actuate the converter (17) when the control switch (23) is opened such that the converter (17) charges the output condenser (CA) during a charging duration (ΔT) before the next closure (t1) of the control switch (23), so that the output current (IA) at the output (21) of the converter (17) rises during the charging duration (ΔT) before the control device (22) closes the control switch (23), wherein the control device (22), depending on the comparison, adjusts at least two of the following parameters for adaptation of the lighting current (IL) and the output voltage (UA) to the respective nominal value:

   - the charging duration (ΔT),

   - a starting value (U0) of the voltage of the output condenser (CA) at the start of the charging duration,

   - a sampling level of the switching signal (S) controlling the converter (17) during the charging duration (ΔT).
2. Operation control device (10) according to claim 1, characterised in that the control device (22) actuates the control switch (23) by a pulse-width-modulated control signal (P).
3. Operation control device (10) according to claim 2, characterised in that the frequency of the pulse-width-modulated control signal (P) is smaller by several orders of magnitude than the switching frequency of the switching signal (S) with which the control device (22) actuates the converter (17).
4. Operation control device (10) according to any of the preceding claims, characterised in that the lighting arrangement (11) comprises a series circuit of several light-emitting diodes (12).
5. Operation control device (10) according to any of the preceding claims, characterised in that the first sampling level (G1) of the switching signal (S) generated by the control device (22) for actuating the converter (17) is constant within the charging duration (ΔT) and/or differs from the second sampling level (G2) after the end of the charging duration (ΔT).
6. Operation control device (10) according to any of the preceding claims, characterised in that the input circuit (15) is formed by a rectifier circuit (16) which generates the input DC voltage (UE) from a network voltage (UN).
7. Operation control device (10) according to any of the preceding claims, characterised in that the rectifier circuit (16) generates a first input DC voltage (UE1) and a second input DC voltage (UE2) of differing amounts, wherein the converter (17) comprises two controlled switching means (18, 19) connected in series and wherein the voltage difference between the two input DC voltages (UE1, UE2) is present at the series circuit of the two controlled switching means (18, 19).
8. Method for operating a lighting arrangement (11) with the following steps:

   - generation of an input DC voltage (UE),

   - generation of an output current (IA) for the lighting arrangement (11) from the input DC voltage (UE) at an output (21) of a converter (17),

   - actuation of a control switch (23) which is connected in series to the lighting arrangement (11) for adjusting the brightness of the lighting arrangement (11),

   - measurement of the lighting current (IL) through the lighting arrangement (11), characterised by the steps:

   - predefinition of a nominal value for the output voltage (UA) when the control switch (23) is opened which is equal to the lighting voltage (UL) when the control switch (23) is closed, and of a nominal value (Isoll) for a lighting current (IL) when the control switch (23) is closed,

   - measurement of the output voltage (UA) present at the output of the converter and transmission of the measured value for the lighting current (IL) and the measured value for the output voltage (UA) to a control device (22) for analysis, wherein the control device (22) is configured to store the measured values in a memory (24) before analysis,

   - comparison of the respective stored measured value for the lighting current (IL) and for the output voltage (UA) with the respective assigned nominal value (Isoll, UL),

   - actuation of the converter (17) when the control switch (23) is opened such that the converter (17) charges an output condenser (CA) at the output (21) of the converter (17) during a charging duration (ΔT) before the next closure (t1) of the control switch (23), so that the output current (IA) at the output (21) of the converter rises during the charging duration (ΔT) before the control device (22) closes the control switch (23), wherein the control device (22), depending on the comparison, adjusts at least two of the following parameters for adaptation of the lighting current (IL) and the lighting voltage (UL) to the respective nominal value,

   - the charging duration (ΔT),

   - a starting value (U0) of the voltage of the output condenser (CA) at the start of the charging duration,

   - a sampling level of the switching signal (S) controlling the converter (17) during the charging duration (ΔT).

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