DE102018110696B3 - Operating device and method for operating a lamp arrangement - Google Patents

Abstract

The invention relates to an operating device (10) and to a method for operating a lighting arrangement (17). A converter unit (12) is provided with a DC voltage (UG). On the output side, the lamp arrangement (17) is connected to the converter unit (12). A control unit (19) controls a converter switch (30) of the converter unit (12). The converter unit (12) has a converter inductance (32) arranged in series with the converter switch (30). The control unit (19) is provided with a nominal current intensity (I) characterizing the luminous power of the luminous arrangement (17) for an inductor current (IL) flowing through the converter inductance (32), and the control unit (19) generates a converter switching signal (W) which converts the transformer switch (17). 30) switches to its conducting state or its blocking state. If the inductance current (IL) reaches a predefinable peak current value (IP), the converter switch (30) is switched to its blocking state. When the target current (I) is less than the average current at minimum peak current value (IP), the converter unit (12) operates in a discontinuous mode of operation having an active phase duration (ts) and a passive phase duration (tn).

Description

The invention relates to an operating device and a method for operating a light-emitting device, which is connected to the operating device.

The problem is dimming to low luminous powers. When dimming by pulse width modulation high frequencies can be achieved, thereby increasing the switching losses and critical frequencies in terms of electromagnetic compatibility or disturbing noises can arise. Out DE 10 2013 216 877 A1 the insertion of a turn-off after each switching cycle of a converter switch is known, so that a discontinuous operation takes place during which a current flows through the lamp assembly during an active phase and then a turn-off is inserted, in which no current flows (passive phase duration), before the current flow is made possible again in the subsequent switching cycle.

Out DE 20 2016 105 453 U1 For example, an operating device and a method for operating a light-emitting diode are known. The operating device has a clocked converter unit with a controllable switch and an inductance, a control unit and a measuring circuit, which measures the inductance current at a shunt and transmits it to the control unit. If the inductance current has returned to zero, the switch is actuated, so that the inductance current rises again.

WO 2016/050689 A2 describes a clocked electronic energy converter that can be used for dimmable ballasts. The known insertion of an additional off-time after each switching cycle is considered critical, since when switching a converter switch in the blocking state voltage oscillations occur at the converter switch, in particular by parasitic energy-storing elements. To solve this problem, it is therefore proposed to insert a turn-off time in a discontinuous operating mode at the end of each switching cycle whose duration is tuned to the natural frequency of the circuit such that the next turn-on of the converter switch takes place in a minimum of the oscillating voltage at the converter switch. This allows the switch-on of the converter switch regardless of the currently transmitted power almost optimal switching discharge.

In such an approach, the selection of the switch-on of the converter switch is of considerable importance. For this purpose, the added Zusatzausschaltdauer must be adapted to the natural frequency of the resonant circuit formed, which requires that the natural frequency is known. The natural frequency depends concretely on parasitic effects and the component properties, which in practice can not be easily calculated due to tolerances of the electrical properties of the components used and must then be determined empirically in individual cases. By this method, the turn-off time is quantized by the natural frequency.

It can therefore be regarded as an object of the present invention to provide an operating device and a method for operating a lighting arrangement, by means of which the setting of low luminous powers can be achieved in a simple manner, without the natural frequency being determined and taken into consideration got to.

This object is achieved by an operating device with the features of claim 1 and a method having the features of claim 19.

The operating device according to the invention has a converter unit with input terminals and output terminals. To the input terminals, a DC voltage can be applied, for example, from a DC voltage source. The lamp arrangement can be connected to the output connections. The converter unit has a converter switch and a converter inductance. The converter switch can be controlled by a control unit. This is set up to control the converter unit or the converter switch based on a desired current. This desired current intensity is predetermined by a signal or a setting value and describes the dimming level of the lighting arrangement. The desired current intensity relates to an average value of a current flowing through the converter unit, which flows at least partially through the lamp unit. For example, the desired current intensity may be an average value of an inductor current flowing through a converter inductance IL described below, which is also referred to below as the mean inductance current.

The operating device also has a measuring circuit. The measuring circuit is set up to detect at least one measured variable which describes an inductance current flowing through the converter inductance. The at least one measured variable is transmitted to the control unit.

The control unit has a converter switching device that is configured to generate a converter switching signal for the converter switch. The converter switching device can be designed as an integrated circuit, for example by a standard component available on the market, which can also be called PFC-IC ("PFC" stands for "Power Factor Correction"). The circuit or function realized by means of the PFC-IS described here is not set up for power factor correction. Rather, the PFC-IC allows an advantageous possibility for the realization of the converter switching device.

The converter switching signal is generated by the converter switching means such that the converter switch is switched to the conducting state once in a single switching clock when the at least one measured variable indicates a zero crossing of the inductance current, and once each switched to the blocking state when the at least one Measured indicates that the inductor current has reached a predetermined current limit. At each zero crossing of the inductor current, the converter switch is turned on and off again when the inductor current has reached the preset current limit. The converter switching device can follow the switching clocks in a continuous mode of operation directly successive.

If the predetermined desired current level resulted in a maximum value of the current value (peak current value) which is smaller than the minimum adjustable peak current value, the control unit operates the converter unit in a discontinuous operating mode. In the discontinuous mode of operation, the peak current value of the inductor current is constant and corresponds to the smallest possible settable value, referred to as the minimum peak current value. In this discontinuous mode of operation, a total duration of a single period is divided into an active phase duration and a passive phase duration. The ratio of active phase duration to passive phase duration is determined based on the desired current strength. The active phase duration corresponds to a number of switching cycles of the converter unit. During the active phase duration, the converter switch is switched by the converter switching signal. During the passive phase duration, the switching of the converter switch is inhibited. In the passive phase duration, the converter switch remains in its blocking state.

The passive phase duration can be chosen to be sufficiently long that the voltage oscillation decays across the converter switch before the converter switch is switched back to the conducting state in the subsequent switching cycle of the next active phase duration. As a result, exact knowledge of the phase position of the voltage oscillation across the converter switch is not necessary. The passive phase duration should therefore not fall below a minimum duration. The passive and active phase duration can be adapted to each other taking into account the minimum duration for the passive phase duration, so that the target current is reached. It has been shown that the frequency of this control (reciprocal of the total duration of active phase duration and passive phase duration) can be selected at about at least 2 to 3 kHz, resulting in a flicker-free operation of the lamp assembly.

The luminous means arrangement preferably has at least one luminous means and in particular at least one semiconductor illuminant. If a plurality of semiconductor illuminants are used in the luminous means arrangement, they can be connected in series and / or in parallel with one another. As light sources, for example light emitting diodes can be used.

It is preferred if the control unit is adapted to operate the transducer unit in a continuous mode of operation when the average desired current magnitude results in a peak current value at least as great as the minimum peak current value. In this case, the switching clocks close to each other directly. In other words, the passive phase duration in continuous mode is zero.

It is also advantageous if the control unit is set up to first calculate a time duration calculating value for the active phase duration, which is a number, based on the average setpoint current intensity and a predefined total duration setpoint value for the active and passive phase duration and / or a predefined minimum value of the passive phase duration at switch clock periods, and to round this number of switch clock periods to an integer, thereby obtaining the active phase duration. Thus, the active phase duration corresponds to at least one switching clock period or even twice, three times, etc. the switching clock period for a switching clock.

In a preferred embodiment, the control unit is set up to determine a first limit value describing a total duration of active and passive phase duration based on the desired current strength and a first boundary condition and based on the desired current strength and a second boundary condition a second describing a total duration of active and passive phase duration Limit value to be determined. The first boundary condition may be a target frequency describing the total duration. The second boundary condition may be a minimum duration for the passive phase duration. On the basis of these two boundary conditions, a lower limit value of an actual frequency can be determined as the first limit value and an upper limit value of the actual frequency as the second limit value. The actual frequency corresponds to the reciprocal of the Total duration and thus describes the switching frequency between active and passive phase duration per unit time.

It is advantageous if the control unit is set up to vary the actual frequency for switching between active and passive phase duration between a plurality of frequency values from the lower limit value to the upper limit value. As a result, any noise development can be influenced without changing the luminous power.

The control unit can also be configured to calculate the passive phase duration as a function of the determined active phase duration in such a way that the average desired current intensity is achieved.

The passive phase duration can be determined and adjusted independently of the switching clock cycle duration of the switching clocks that are generated in the active phase duration. It is therefore irrelevant whether or not the passive phase duration corresponds to an integer multiple of the switching clock period.

It is also advantageous if the control unit is set up to measure and store an actual value for the active phase duration. Subsequently, the measured actual value can be used to calculate the passive phase duration and adjust it if necessary, in order to make a fine adjustment, so to speak. In this case, for example, the average current intensity of the current flowing through the lamp arrangement can be better adapted to the average desired current or the length of the passive phase duration to achieve a desired frequency or total duration of active and passive phase duration can be achieved.

In a preferred embodiment, the converter circuit is designed as a down converter. The buck converter is also referred to as a buck converter or buck converter.

In one embodiment, the converter circuit has a converter capacitor arranged in parallel with the output terminals. The converter capacitor is therefore connected in parallel with the lamp arrangement when the lamp arrangement is connected.

In one embodiment, the converter circuit has a converter diode. The cathode of the converter diode is electrically connected to the converter switch and the anode of the converter diode is electrically connected directly to the converter capacitor.

In a preferred embodiment, the measuring circuit has a measuring coil assigned to the transducer inductance. Depending on the magnetic field in the transducer inductance, a measuring voltage is induced in the measuring coil which is used as a measured variable. The induced measurement voltage is descriptive of an inductor current flowing through the converter inductance.

Additionally or alternatively, the measuring circuit may have a current measuring resistor. The current measuring resistor is preferably connected in series with the output terminals or in series with the lamp arrangement connected thereto. The voltage across the current measuring resistor is therefore descriptive of a current flowing through the lighting device during operation.

To generate a DC voltage to supply the converter unit, a DC voltage source can be used, which can be formed in particular by a DC-DC converter. The DC-DC converter can convert a mains voltage into a rectified DC voltage for supplying the converter unit.

• 1 ein Blockschaltbild eines Ausführungsbeispiels einer Betriebsvorrichtung zum Betreiben einer Leuchtmittelanordnung,
• 2 ein Blockschaltbild eines Ausführungsbeispiels einer Wandlereinheit und einer Steuereinheit der Betriebsvorrichtung aus 1,
• 3 das Ausführungsbeispiel der Wandlereinheit und der Steuereinheit gemäß 2 mit einer Wandlerschalteinrichtung, die durch einen integrierten Schaltkreis zur Leistungsfaktorkorrektur gebildet ist,
• 4 und 5 jeweils ein beispielhafter zeitlicher Verlauf eines Induktivitätsstromes durch eine Wandlerinduktivität bei den Ausführungsbeispielen gemäß der 2 und 3 in einem kontinuierlichen Betriebsmodus,
• 6 eine schematische Prinzipdarstellung der Ermittlung einer aktiven Phasendauer und einer passiven Phasendauer für einen diskontinuierlichen Betriebsmodus der Wandlereinheit und
• 7 eine schematische Darstellung des diskontinuierlichen Betriebsmodus beim Betrieb der angeschlossenen Leuchtmittelanordnung mit einer geringen mittleren Stromstärke des durch die Leuchtmittelanordnung fließenden Stroms.

Preferred embodiments of the invention will become apparent from the dependent claims, the description and the drawings. Hereinafter, preferred embodiments of the invention will be explained in detail with reference to the accompanying drawings. Show it:

• 1 a block diagram of an embodiment of an operating device for operating a lamp assembly,
• 2 a block diagram of an embodiment of a converter unit and a control unit of the operating device from 1 .
• 3 the embodiment of the converter unit and the control unit according to 2 with a converter switching device, which is formed by an integrated circuit for power factor correction,
• 4 and 5 in each case an exemplary time profile of an inductance current through a converter inductance in the exemplary embodiments according to FIG 2 and 3 in a continuous mode of operation,
• 6 a schematic diagram of the determination of an active phase duration and a passive phase duration for a discontinuous mode of operation of the converter unit and
• 7 a schematic representation of the discontinuous mode of operation in Operation of the connected lamp assembly with a low average current of the current flowing through the lamp assembly current.

In 1 is a block diagram of an embodiment of an operating device 10 illustrated. The operating device 10 has a DC voltage source 11 on, the output side, a DC voltage UG provides.

To the DC voltage source 11 is a transducer unit 12 connected. The converter unit 12 has a first input connection 13 and a second input terminal 14 , between which the DC voltage UG provided. The converter unit 12 also has a first output port 15 and a second output terminal 16 , wherein a lighting arrangement 17 with at least one luminous means and, according to the invention, at least one semiconductor illuminant 18 to the output terminals 15 . 16 connected. Are several semiconductor lamps 18 in the lamp arrangement 17 present, they can be connected in series and / or parallel to each other. Each semiconductor illuminant 18 is for example formed by a light emitting diode.

The converter unit 12 is through a control unit 19 controllable. The control unit 19 is from a dimmer 20 a dimming signal D transmitted, which is a nominal current I _should for an average of one by the transducer unit 12 flowing current dictates, of which in turn a mean value of a through the lamp assembly 17 flowing light source I1 depends .. The control unit 19 controls the transducer unit 12 depending on the dimming signal D and in particular depending on the desired current intensity I _should and sets by means of the converter unit 12 the actual amperage according to the requested nominal amperage I _should on.

As it is in 1 is schematically illustrated, is the DC voltage source 11 For example, by a DC-DC converter 21 formed by a controller 22 is controllable. Alternatively, the control unit could 19 both for controlling the converter unit 12 , as well as the DC-DC converter 21 be used. The DC-DC converter 21 converts an input-side mains voltage U.N. in the rectified DC voltage UG ,

In 2 is a block diagram of the control unit 19 and the transducer unit 12 for an embodiment of the operating device 10 illustrated. Between the first input connection 13 and the second input terminal 14 is the DC voltage UG on. By way of example, the second input terminal is 14 connected to a reference potential, for example, a ground potential M , The converter unit 12 has a controllable converter switch 30 in the embodiment by a semiconductor switch and in particular a field effect transistor 31 is formed. The drain terminal of the field effect transistor 31 is with the first input port 13 connected. The source terminal of the field effect transistor 31 is via a transformer inductance 32 with the first output terminal 15 connected. In addition, the source terminal of the field effect transistor 31 with the cathode of a converter diode 33 whose anode is connected to the second output terminal 16 connected is. Between the output terminals 15 . 16 and thus parallel to the lamp arrangement 17 is also a converter capacitor 34 connected.

For generating a converter switching signal W for switching the converter switch 30 has the control unit 19 a converter switching device 35 on. The converter switching device 35 has a control output 36 to which the converter switching signal W is provided. The control output 36 is with a non-inverting input of an AND gate 37 connected. The exit of the and gate 37 is connected to a control terminal of the converter switch 30 and, according to the gate terminal of the field effect transistor 31 connected. The exit of the and gate 37 is for example via a driver 55 to the gate terminal of the field effect transistor 31 connected.

Another, inverting input of the AND gate 37 is with an output of a first comparator 38 connected. An input of the first comparison element 38 is with a first counter 39 connected. A counting input 40 of the first counting member 39 is with the output of the and gate 37 connected. The first counting member 39 and the first comparison member 38 form a first counting unit 41 ,

To the control unit 19 According to the example also belongs a second counting unit 42 which is a second counting member 43 and a second comparison element 44 having, with the second counting member 43 connected is. The second counting member 43 has an internal clock for generating a count clock to the second comparator 44 is transmitted. The second comparison element 44 has an output port that comes with a reset input 45 of the second counting member 43 and a reset input 45 of the first counting member 39 connected is. About the output, the second comparator 44 a reset signal R to reset the first counter member 39 and the second counting member 43 provide.

A start input 46 of the second counting member 43 is with the output of the first comparator 38 connected. The first comparison element 38 provides an operating mode signal at its output B ready.

In the embodiment described here is also a third counting unit 47 present, which is a third counting member 48 and one with the third counter 48 connected detection element 49 having. A detection input 50 of the detection element 49 is at the output of the first comparator 38 connected.

The control unit 19 also has a measuring circuit 56 on. The measuring circuit 56 has, for example, a measuring coil 57 , that of the transformer inductance 32 is assigned such that a magnetic field of the Wandlerinduktivität 32 a voltage in the measuring coil 57 can induce. The in the measuring coil 57 induced voltage describes an inductance current IL caused by the transducer inductance 32 flows. The measuring coil 57 is on the one hand with the ground potential M and on the other hand, via a first ohmic resistance 58 with a first fair entrance 59 the converter switching device 35 connected. The in the measuring coil 57 induced voltage forms a first measure S1 , that of the converter switching device 35 is supplied.

To the measuring circuit 56 also includes a current measuring resistor 60 , The current measuring resistor 60 is on the one hand with the second output terminal 16 the transducer unit 12 as well as a second fair entrance 61 the converter switching device 35 and on the other hand with the ground potential M connected. The at the current measuring resistor 60 The applied voltage is therefore characteristic of the transformer inductance 32 flowing inductor current IL if the converter diode 33 at conductive converter switch 30 locks. The at the current measuring resistor 60 applied voltage forms a measurand S2 , that of the converter switching device 35 is supplied. The measuring coil 57 allows a measurement of the inductance current IL even if the converter diode 33 conducts and the inductor current IL through the converter diode 33 and not by the current sense resistor 60 flows.

When the lamp arrangement is connected 17 the inductance current flows IL by the parallel connection of the lamp arrangement 17 and the converter capacitor 34 , wherein a luminous flux I1 through the lamp arrangement 17 and a capacitor current I2 through the converter capacitor 34 flows: IL = I1 + 12. The through the converter unit 12 provided inductance current IL is therefore characteristic of the luminous flux I1 so that to set a desired luminous power according to the dimming signal D a current setpoint Isoll for the mean value of the inductance current IL can be specified as the mean inductance IL referred to as.

Based on 4-7 will the operation of the operating device 10 with the control unit 19 and the transducer unit 12 according to 2 explained.

Performs the set current I _should for the mean inductance current IL that via the dimming signal D is requested, to a maximum value of the current (peak current value IP ) that is at least as large as a minimum adjustable peak current value IP _min , the converter unit can 12 be operated in a continuous mode of operation, as in the 4 and 5 is shown schematically by way of example. The counting units 41 . 42 . 47 are not active and the operating mode signal B is LOW (digital zero), so that the converter switching signal W via the AND gate 37 to the control terminal of the converter switch 30 (Here the gate of the field effect transistor 31 ) is forwarded. The converter switching device 35 evaluates the at the first fair entrance 59 applied first measured variable S1 and at the second fair entrance 61 applied second measured variable S2 out. About the first measurand S1 becomes a zero crossing of the inductor current IL determined. About the second measurand S2 it is determined whether by the converter inductance 32 flowing inductance current IL a predeterminable or adjustable peak current value IP has reached. At a zero crossing of the inductor current IL becomes the converter switching signal W HIGH (digital one), and the converter switch 30 is switched to its conducting state. An inductance current begins IL to flow, which is constantly increasing. As soon as the inductor current IL has reached the current limit IG, the converter switching device switches 35 the converter switching signal W from HIGH to LOW, whereby the converter switch 30 goes into its blocking state. About the transformer inductance 32 , the lighting arrangement 17 and the converter diode 33 can continue an inductance current IL flow, which decreases continuously and finally reaches the value zero. This zero crossing is in turn by the converter switching device 35 detected and the converter switch 30 will be switched on again in the next switching cycle.

In each switching cycle is the converter switch 30 during a turn-on period te conducting and during a subsequent turn-off period ta blocking. At the beginning of each switching cycle, the converter switch 30 is switched to its conducting state with the end of the on-time te switched to its off state, and remains in this state during the off-time ta until the end of the switching clock when the inductor current IL has a zero crossing. The sum of the switch-on time te and the switch-off time ta corresponds to a switch clock period TP ,

The in the 4 and 5 illustrated operating mode of the converter unit 12 can as continuous operating mode or critical operating mode are referred to, in which the current flow of the inductor current IL by switching the converter switch 30 is immediately effected again as soon as the zero crossing of the inductor current IL was determined. The interruption period of the inductance current IL between two consecutive switching cycles is as short as possible in this continuous mode of operation. For the correct calculation of the mean inductance current IL , this interruption period must be considered. For this purpose, for example, a correction factor describing the interruption period can be introduced. The individual switching clocks in the continuous mode of operation close substantially directly to each other and the interruption period is as short as it is technically possible.

By comparing the 4 and 5 It can be seen schematically that the reduction of the luminous power in the continuous operating mode by lowering the peak current value IP can be reached. The peak current value IP can be based on the nominal current I _should for the mean inductance current IL be determined, for example, in the converter switching device 35 in that the dimming signal or another signal describing the luminous power can be transmitted for this purpose. This results in the switching clock period TP decreases and the switching frequency of the converter switch 30 is increased. At a very low requested luminous power, ie a very low peak current value IP For example, the switching frequency becomes very high, and the continuous mode of operation is not suitable or not designed for even greater dimming, for example, from a switching frequency of about 200 kHZ. It becomes a minimum peak current value IP _min determined or predetermined, which must not be fallen below. According to the invention, therefore, is switched from the continuous mode of operation in the discontinuous mode of operation, when the target current I _should to a peak current value IP which is less than the minimum peak current value IP _min ,

In this discontinuous mode of operation, the peak current value becomes IP not further reduced, but at the minimum peak current value IP _min kept constant. This results in a minimum switching cycle period TP _min (at IP = IP _min ), as it is in 7 is shown. To a further lowering of the luminous power of the lamp assembly 17 to enable, in the discontinuous mode of operation of the converter unit 12 an active phase duration ts and a passive phase duration tn determined and set alternately, in the sum of a total duration TG correspond. During the active phase duration, the switching of the converter switch 30 analogous to continuous operation, whereas the converter switch 30 during the passive phase duration tn remains in its blocking state. The active phase duration ts is either the same size as a minimum switching cycle period TP _min or equal to several minimum switching clock periods TP _min , In 7 By way of example, a discontinuous mode of operation is shown in which the active phase duration ts is the same size as three minimum switching cycle periods TP _min , This is immediately followed by the passive phase duration tn while the converter switch remains nonconductive.

The passive phase duration tn can be independent of the minimum switching clock period TP _min be determined and set.

1. 1. das Verhältnis zwischen der aktiven Phasendauer ts und der passiven Phasendauer tn ist so gewählt, dass die Leuchtleistung der Sollleuchtleistung möglichst nahekommt;
2. 2. die passive Phasendauer tn ist mindestens so lang wie eine vorgegebene Mindestdauer oder liegt innerhalb eines vorgegebenen Solldauerbereichs für die passive Phasendauer tn;
3. 3. die Gesamtdauer TG aus aktiver Phasendauer ts und passiver Phasendauer tn entspricht möglichst einer vorgegebenen Gesamtsolldauer oder liegt innerhalb eines vorgegebenen Solldauerbereichs für die Gesamtdauer TG.

Starting from a continuous operation with the minimum switching cycle period TP _min , which represents a threshold value of the luminous power for the transition from continuous operation to discontinuous operation, becomes the proportion of the active phase duration ts to the total duration TG determined according to the proportion of the requested nominal luminous power to the limit of the luminous power. This results initially in a time duration calculating value tr. This time duration calculating value tr corresponds to a calculated factor multiplied by the switching cycle period TP according to the minimum switching clock period, for example TP _min , The computational factor is rounded off or rounded up to an integer (natural number including one without zero) (see 6 ). Subsequently, the passive duration tn to the determined active phase duration ts adapted so that one or more of the following conditions are fulfilled as ideally as possible:

1. 1. the ratio between the active phase duration ts and the passive phase duration tn is chosen so that the luminous power of the nominal luminous power comes as close as possible;
2. 2. the passive phase duration tn is at least as long as a predetermined minimum duration or is within a predetermined target duration range for the passive phase duration tn ;
3. 3. the total duration TG from active phase duration ts and passive phase duration tn If possible corresponds to a predetermined total target duration or is within a predetermined target duration range for the total duration TG ,

By the above-mentioned third condition, a desired frequency can be achieved in the discontinuous operation mode, so that flickering of the lighting arrangement 17 is avoided.

In addition, the passive phase duration tn be chosen sufficiently long, so that voltage oscillations when switching the converter switch 30 from the senior to the blocking state may occur due to the attenuation have subsided (see above second condition).

The following is based on 6 on the basis of an example, the parameters for carrying out the discontinuous operation will be explained.

It is assumed by way of example that the luminous power provided by the dimming signal D 25% of the maximum luminous power is required. It is also assumed that the luminous efficiency in continuous operation can be reduced to 50% of the maximum luminous power. Therefore, starting from the minimum peak current IP _min a duty cycle between active phase duration ts and passive phase duration tn of 50% in order to obtain the desired luminous power corresponding to 25% of the maximum possible luminous power.

Let be a target frequency as parameter or first boundary condition _goal from 3000 Hz assumed a flicker of the bulb assembly 17 to prevent.

wobei PWM das Tastverhältnis ist, beispielsgemäß 50%, und n die Anzahl der Schalttakte während der aktiven Phasendauer ts angibt. Für die Zielfrequenz f_Ziel gilt: $$\frac{1}{f_{Ziel}}=T{P}_{min}\cdot n+tn=TG$$

Where: $$PWM=\frac{T{P}_{min}\cdot n}{T{P}_{min}\cdot n+tn}$$

where PWM is the duty cycle, for example 50%, and n is the number of switching cycles during the active phase duration ts indicates. For the target frequency f _goal applies: $$\frac{1}{f_{Ziel}}=T{P}_{min}\cdot n+tn=TG$$

From the equations (1) and (2) can then be the number n of the switching cycles for the active phase duration ts be determined: $$n=\frac{PWM}{T{P}_{min}\cdot f_{Ziel}}$$

For the numerical values assumed here by way of example, the duty cycle PWM = 0.5, the minimum switching cycle period TP _min is for example 10 μs and the target frequency f _goal is 3000 Hz. This results in the calculated number n * of the switching cycles for the active period ts to n * = 16.67 as arithmetic result. Since the number n of switching cycles can only be an integer, the calculated value n * is rounded up or down, for example to n = 17. For a minimum switching cycle period TP _min results in the passive phase duration tn as follows: $$tn=\frac{T{P}_{min}\cdot n}{PWM}-T{P}_{min}\cdot n=170\mu s$$

By rounding the calculated value n ^* for the number of switching cycles to an integer value, the predetermined target frequency f _goal not exactly reached. From equation (2), the actually resulting actual frequency f _is be determined, which in the present numerical example f _is = 2941 Hz. This actual frequency f _is , which results on the basis of this first boundary condition, can be used as a limit value and in particular a lower limit for defining a frequency range.

Another, second boundary condition may be a minimum duration of the passive phase duration tn his. The minimum duration can be specified so that the oscillation of the voltage at the converter switch 30 , which follow the zero crossing of the inductor current IL adjusted by the existing attenuation in the system has decayed sufficiently. The above equations (1) and (2) apply accordingly. For example, tn = 56 μs can be selected as the minimum duration for the passive phase duration. When used in equation (1), the number of switching cycles for the number of switching cycles of the active phase duration is rounded off ts : n = 6.

Based on the number of switching cycles can then analogously to equation (4), the passive phase duration tn determined here, which results in tn = 60 μs.

For the resulting actual frequency f _is applies analogously to equation (2): $$f_{ist}=\frac{1}{TG}=\frac{1}{ts+tn}=8333Hz$$

This actual frequency f _is , which results on the basis of this second boundary condition, can be used as a limit value and in particular upper limit value for the definition of a frequency range.

Based on the above calculation on the one hand by the specification of a target frequency f _goal and second, by specifying a minimum duration for the passive phase duration tn In each case, a limit value for a frequency range can be determined. For example, based on the specification of the target frequency actual frequency f _is determined and this actual frequency f _is be used as lower frequency limit.

In addition, by specifying the minimum period of time for the passive phase duration tn an actual frequency f _is which can be used as the upper limit for the frequency. in the The range between the lower limit frequency and the upper limit frequency may depend on the choice of the number n of the switching cycles for the active phase duration ts different frequencies for the same duty cycle PWM are set according to the following relation: $$f\left(n\right)=\frac{PWM}{T{P}_{min}\cdot n}$$

It is possible, the number n of the switching cycles for the active phase duration ts to vary or modulate without changing the luminous power, whereby the resulting noise can be influenced. Taking into account the exemplary numerical values determined above, PWM = 50% can be achieved by varying the number n of switching cycles for the active phase duration at a duty cycle ts from n = 6 to n = 17 give twelve different frequencies f (n) according to equation (6), between which can be switched without changing the luminous power or the brightness of the lamp assembly.

It is also possible to vary the actual frequency arbitrarily in the entire spectrum between the lower limit frequency and the upper limit frequency, this being achieved only by a change in the duty cycle and thus the luminous power and the brightness. For this purpose, an algorithm can be used which uses the discrete possible frequencies f (n) according to equation (6) as support points and a change of the frequency f between the discrete values f (n) such that an average luminous power results which corresponds to the required luminous power and thereby minimizes the deviations of the luminous power from the mean luminous power (variance).

During the active phase duration ts and / or during continuous operation of the transducer unit 12 the switching on of the converter switch takes place 30 (Rising edge of the converter switching signal W) at a time at which the converter switch 30 applied, oscillating voltage (drain-source voltage) of the field effect transistor 31 ) has a first minimum. This corresponds to the zero crossing of the inductance current IL ,

The determined active phase duration ts is in the first comparison member 38 and the determined passive phase duration tn in the second comparison member 44 stored. About the first counting member 39 is the number of switching cycles via the counting input 40 detected. In the first comparison element 38 It checks if the active phase duration ts corresponding number of switching cycles is reached. If this is the case, the output of the first comparison element 38 the operating mode signal B switched from LOW to HIGH. The and gate 37 is thereby blocked, so to speak. It serves as a gate and can lock the converter switching signal W, which then no longer to the converter switch 30 is forwarded.

The counting member 39 is preferably incremented with the occurrence of a falling edge of the converter switching signal W. It can thereby be achieved that the switching operation of the operating mode signal B from LOW to HIGH, preferably directly to the falling edge of the converter switching signal W takes place. Through this temporal coordination spikes can be avoided.

The operating mode signal B will also be at the start entrance 46 transmitted, the second counting member 43 starts as soon as the power on signal B is switched from LOW to HIGH. In the second comparison member 44 it is checked whether the determined or stored passive phase duration tn has expired. Once this has been determined, the second comparator generates 44 a reset signal for the first counter 39 and the second counting member 43 , This will be in the first counting unit 41 causes the operating mode signal B is switched back from HIGH to LOW, which is the beginning of the next active phase duration ts marked. The and gate 37 the converter switching signal W can be applied to the converter switch 30 hand off. As the inductor current IL Zero causes the converter switching device 35 the switching of the converter switch 30 in the conductive state and it starts the next active phase duration ts , Once the number of preset switching cycles during the active phase duration ts reached, the and gate becomes 37 via the operating mode signal B locked again, the converter switch 30 also blocks and the passive phase duration tn starts. This process is repeated cyclically during the discontinuous operation, the duration of one cycle of the total duration TG equivalent.

By means of the optional third counting unit 47 can be the actual active phase duration ts be measured. About switching the operating mode signal B from LOW to HIGH is via the detection input 50 the registration unit 49 Activates and records the time based on the counts of the third counter 48 , At the end of the active phase duration ts becomes the operating mode signal B switched from LOW to HIGH, resulting in the detection element 49 and thus the exact time duration for the active phase duration ts is determined. This period of time may be used to determine and / or adjust the passive phase duration tn be used.

A regulation of the current flowing through the lamp arrangement does not occur in the described embodiment. The through the lamp arrangement flowing luminous flux I1 or the luminous power of the luminous means arrangement 17 is set or controlled without feedback of a corresponding measured value.

In 3 is an embodiment for the realization of the control unit 19 illustrated using a PFC IC. For example, an IC of the type MP44014 from MPS®, which is the converter switching device, is used as PFC-IC 35 forms. The structure and operation of this IC are known, so that it will not be discussed further. The IC used has eight connections. The IC connection "ZCS" forms the first measuring input 59 and the IC connection "CS" forms the second measuring input 61 , The IC connection "GATE" forms the control output 36 , An IC supply connection "VCC" is with a supply voltage UV connected and the ground terminal "GND" is connected to the ground potential M connected.

A first pulse width modulated signal PWM1 is over a second ohmic resistance 65 applied to the IC connection "MULT", and a second pulse width modulated signal PWM 2 is over a third ohmic resistance 66 to the IC input "FB" and via a series circuit of the third ohmic resistor 66 and a fourth ohmic resistance 67 applied to the IC connector "COMP". A first capacitor 68 connects the IC connection "MULT" to the ground potential M and a second capacitor 69 connects the "FB" and "COMP" IC connectors. The capacitors 68 . 69 limit the bandwidth of the pulse width modulated signals PWM1 . PWM 2 ,

These pulse width modulated signals PWM1 . PWM 2 are generated by a multiplier in the converter switching device 35 multiplied by each other and define the current limit IG. The multiplication of two pulse-width-modulated and filtered, in particular low-pass filtered, signals can achieve a quadratic characteristic and improve the resolution in digital quantization, especially at low current intensities.

The invention relates to an operating device 10 and a method of operating a lighting device 17 , A converter unit 12 becomes a DC voltage UG provided. On the output side is the lamp arrangement 17 to the transducer unit 12 connected. A control unit 19 controls a transformer switch 30 the transducer unit 12 on. The converter unit 12 has one in series with the converter switch 30 arranged transducer inductance 32 on. By means of a measuring circuit 56 At least one measured variable is detected, the one by the Wandlerinduktivität 32 flowing inductor current IL characterized. The control unit 19 becomes a target current I _should for an average value of the inductance current IL specified. The target current I _should characterizes the adjusting luminous power. From the nominal current I _should can be a peak current value IP for the inductance current IL be determined so that is the target current I _should corresponding mean value of the inductance current IL established. The control unit 19 generates a converter switching signal W which is the converter switch 30 switches to its conducting state or its blocking state. At the beginning of a switching cycle, the converter switch 30 switched to its conducting state when the inductor current IL has a zero crossing. The inductance current IL then rises and reaches the determined or predetermined peak current value IP , At this time, the converter switch 30 switched to its blocking state, which causes the inductor current IL sinks. Once the inductor current IL is equal to zero, the switching cycle is completed and the next switching cycle begins. When the set current I _should is smaller than an average value of the converter unit 12 flowing current at a predetermined minimum peak current value IP _min , which should not fall below, becomes the converter unit 12 operated in a discontinuous mode of operation, with an active phase duration ts includes one or more complete switching cycles and adhere to the active phase duration ts a passive phase duration tn followed. The active and passive phase duration ts . tn are tuned such that the inductor current IL at least substantially the desired current intensity I _should equivalent. Additionally, the passive phase duration tn be chosen so that it has a minimum duration. Alternately or additionally, while maintaining the ratio of the active phase duration ts to the passive phase duration tn a total duration TG be set or specified such that the passive phase duration tn a minimum duration does not fall below and / or a total duration setpoint is at least substantially achieved.

LIST OF REFERENCE NUMBERS

10

operating device

11

DC voltage source

12

converter unit

13

first input connection

14

second input connection

15

first output terminal

16

second output terminal

17

Lamp positioning

18

Semiconductor lamps

19

control unit

20

dimmer

21

DC converter

22

control

30

converter switch

31

Field Effect Transistor

32

transformer inductance

33

converter diode

34

conversion capacitor

35

Converter switching device

36

control output

37

And gate

38

first comparison element

39

first counting member

40

Counting

41

first counting unit

42

second counting unit

43

second counting member

44

second comparison element

45

Reset input

46

start input

47

third counting unit

48

third counter

49

determining member

50

detection input

55

driver

56

measuring circuit

57

measuring coil

58

first ohmic resistance

59

first fair entrance

60

Strommmesswiderstand

61

second fair entrance

65

second ohmic resistance

66

third ohmic resistance

67

fourth ohmic resistance

B

Operation mode signal

D

dimming signal

f _is

actual frequency

IP

Peak current value

IP _min

minimum peak current value

IL

inductor

M

ground potential

P _should

Target lighting performance

R

Reset signal

S

Converter switching signal

UG

DC

U.N.

mains voltage

UV

supply voltage

Ta

off period

Te

on period

tn

passive phase duration

TP

Switching clock period

ts

active phase duration

TG

Total period

Claims (19)

Operating device (10), which is set up to operate a lamp arrangement (17) connected to it, with a converter unit (12), the input terminals (13, 14) for applying a DC voltage (UG), output terminals electrically connectable to the lamp arrangement (17) ( 15, 16), a controllable converter switch (30) and a Wandlerinduktivität (32), comprising a control unit (19) which is adapted to the converter unit (12) based on a desired current intensity (I _soll ) for an average value of the Transducer inductance (32) to drive current flowing inductor (IL), with a measuring circuit (56), which is adapted to measure at least one measured variable that characterizes the inductor current (IL), wherein the at least one measured variable is transmitted to a converter switching device (35) the converter switching device (35) is adapted to generate a converter switching signal (W) which converts the converter r (30) switches to the conducting state once during a switching clock when the at least one measured variable indicates a zero crossing of the inductance current (IL), and once into the blocking state when the at least one measured variable indicates that the inductance current (IL) has reached a predeterminable peak current value (IP), wherein the control unit (19) is adapted to operate the converter unit (12) in a discontinuous mode of operation when the desired current level (I _soll ) is less than a mean value of the inductor current (IL) at a predetermined minimum peak current value (I _Pmin ), wherein the control unit (19) is adapted to determine for the discontinuous operating mode based on the desired current intensity (I _soll ) a one active phase duration (ts) descriptive number of switching cycles and a passive phase duration (tn) . and during the active phase duration (ts) to allow the switching of the converter switch (30) by the converter switching signal (W) and during the passive phase duration (tn) to prevent the switching of the converter switch (30) in the conducting state. Operating device after Claim 1 characterized in that the control unit (19) is arranged to operate the transducer unit (12) in a continuous mode of operation when the desired current intensity (I _soll ) is at least as high as an average value of the inductor current (IL) at a predetermined minimum peak current value (I _Pmin ). Operating device after Claim 1 or 2 , characterized in that the control unit (19) is adapted to, based on the desired current intensity (I _soll ) and a predetermined Gesamtdauersollwert for the active and the passive phase duration (tn) first a time duration calculating value (tr) for the active phase duration (ts) and calculate the active phase duration (ts) based on this time duration calculation value (tr). Operating device after Claim 1 or 2 , characterized in that the control unit (19) is adapted to calculate based on the target current intensity (I _soll ) and a predetermined minimum value for the passive phase duration (tn) first a time duration calculating value (tr) for the active phase duration (ts) and the to determine active phase duration (ts) based on this time duration calculation value (tr). Operating device after Claim 3 or 4 , characterized in that the control unit (19) is arranged to select one of the time interval calculating value (tr) nearest integer multiples of the switching clock period (TP, TPmin) to obtain the active phase duration (ts). Operating device according to one of Claims 3 to 5 , characterized in that the control unit (19) is adapted to calculate the passive phase duration (tn) as a function of the active phase duration (ts) such that a resulting difference between the inductance current (IL) and the desired current intensity (I _soll ) as low as possible. Operating device according to one of the preceding claims, characterized in that the control unit (19) is adapted, based on the desired current intensity (I _soll ) and a first boundary condition a first duration (TG) of active and passive phase duration (ts, tn) descriptive first Determine limit and based on the target current strength (I _soll ) and a second boundary condition to determine a total duration (TG) of active and passive phase duration (ts, tn) describing second limit. Operating device after Claim 7 , characterized in that the first boundary condition is a target frequency (f _target ) describing the total duration (TG) and / or that the second boundary condition is a minimum duration for the passive phase duration (tn). Operating device after Claim 7 or 8th , characterized in that the first limit value corresponds to a lower limit value of an actual frequency (fist) for switching between active and passive phase duration and that the second limit value corresponds to an upper limit value of an actual frequency (fist). Operating device after Claim 9 , characterized in that the control unit (19) is adapted to vary the actual frequency (fist) for switching between active and passive phase duration between a plurality of frequency values from the lower limit to the upper limit. Operating device according to one of the preceding claims, characterized in that the control unit (19) is adapted to measure and store an actual value for the active phase duration (ts). Operating device after Claim 11 , characterized in that the control unit (19) is adapted to calculate the passive phase duration (tn) depending on the measured and stored actual value of the active phase duration (ts). Operating device according to one of the preceding claims, characterized in that the converter circuit (12) is designed as a down converter. Operating device according to one of the preceding claims, characterized in that the converter circuit (12) has a converter capacitor (34) which is connected in parallel with the output terminals (15, 16). Operating device after Claim 14 characterized in that the transducer unit (12) comprises a transducer diode (33) having its cathode directly electrically connected to the transducer switch (30) and the transducer inductor (32), and whose anode is directly electrically connected to the transducer capacitor (34). Operating device according to one of the preceding claims, characterized in that the measuring circuit (56) has a measuring inductor (57) associated with the transducer inductance (32) in which a voltage is induced as a measured variable by a magnetic field of the transducer inductance (32). Operating device according to one of the preceding claims, characterized in that the measuring circuit (56) has a current measuring resistor (60) which is connected in series with the output terminals (15, 16). Operating device according to one of the preceding claims, characterized in that a DC-DC converter (21) for generating the DC voltage (UG) is present. Method for operating a luminous means arrangement (17) by means of an operating device (10) comprising a converter unit (12) which has a converter switch (30), a converter inductor (32), input terminals (13, 14) to which a DC voltage (UG) is applied, and output terminals (15, 16) electrically connected to the lamp arrangement (17), a measuring circuit (56) which is set up for measuring at least one measured variable which characterizes an inductor current (IL) flowing through the converter inductance (32), presetting one Desired current intensity (I _soll ) for the inductance current (IL), - generating a converter switching signal (W), which switches the converter switch (30) during a switching clock in each case once in the conductive state, when the at least one measured variable indicates a zero crossing of the inductor current (IL) , and once in the blocking state, when the at least one measurand indicates that the inductance tsstrom (IL) has a predetermined peak current (IP) has been reached, - setting a discontinuous operation when the target current (I _soll) is smaller than a mean value of the inductance current (L) at a predetermined minimum peak current value (I _Pmin), wherein based on the Target current intensity (I _soll ) a number of switching clocks describing an active phase duration (ts) and a passive phase duration (tn) are determined, and allowing the switching of the converter switch (30) by the converter switching signal (W) during the active phase duration (ts) and inhibiting switching the converter switch (30) by the converter switching signal (W) during the passive phase duration (tn).

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