EP2584870B1 - LED-Lamp with variable intensity - Google Patents

Description

The invention relates to an LED lamp (LED: light emitting diode), in particular an LED spotlight, with at least three LEDs, each of the LEDs is designed to emit a light with the same spectral property, as well as with a control unit for controlling the LEDs. Moreover, the invention relates to a method for controlling such an LED light.

A known such LED light can be adjusted by means of pulse width modulation (PWM) in their brightness. For pulse width modulation, the LEDs are switched on and off in very short time intervals so that "on times" and "off times" result for the LEDs. These time intervals are so short that under normal circumstances no corresponding brightness fluctuations are perceived by a human observer.

However, when this LED lamp is used indoors for lighting when shooting movies, there is a general problem that when the light is dimmed, a "flicker in the camera" is generated. In other words, it usually happens that due to the frequency with which the camera captures the images, the "off times" of the LEDs cause certain images less and other images receive more light from the LED light , This can lead to unwanted brightness fluctuations on the films, which are perceptible as such. This problem also exists in particular with "high-frequency" PWM techniques, since today's camera and film technologies likewise use a comparatively high frequency (HD).

To avoid this, it is known to dim an LED lamp by changing the supplied current. The disadvantage here, however, that this leads to a, usually undesirable change in the color temperature of the light emitted by the LED light; This significantly reduces the quality of the lighting. In addition, this type of dimming adversely affects the life of the LEDs.

From the US 2007/0211463 A1 is an LED lamp for tunnel lighting known. The luminaire comprises a plurality of groups of LEDs, wherein more or fewer LED groups can be switched on to change the brightness.

The invention has for its object to provide a corresponding improved LED light; In particular, the LED light should be better suited for lighting when shooting movies. In addition, an improved method for controlling a corresponding LED light to be specified.

This object is achieved according to the invention with the objects mentioned in the independent claims. Particular embodiments of the invention are indicated in the dependent claims.

According to the invention is a LED luminaire, in particular a LED spotlight provided having or the LEDs in a total number N for light emission in an external space of the LED lamp, where N ≥ 3 applies and wherein each of N LEDs designed the total to is to emit a light with the same spectral property. Furthermore, the LED lamp has a control unit for controlling the LEDs; the control unit is designed to set the luminaire optionally in one of a plurality of different operating modes, wherein in each of the different operating modes a respective different part number n of the total of N LEDs, with 0 ≦ n ≦ N , and the respective remaining N - n LEDs are turned off.

In this way, it can be achieved that is emitted from the LED light light in different levels of brightness, with each brightness level each of the LEDs switched to this 100%, ie without dimming, light emits. This makes it possible to prevent the LEDs from being switched on and off in rapid time sequences, as is the case with the known PWM technology. Corresponding unwanted brightness fluctuations in film recordings can be thus reliably avoid. In addition, it is possible to prevent the color temperature of the light emitted by the lamp from changing as the brightness level changes.

Preferably, the control unit is further configured to put the LED light in one of the different modes depending on a predetermined dimming value. This allows easier adjustment of the brightness.

According to the invention, in at least one mode of operation of the different modes of operation, at least one of the N LEDs is turned on and at least one other of the N LEDs is off, with the following: Let j be exactly the part number of the total of N LEDs turned on in the considered mode the control unit is further configured to selectively switch on one of a plurality of different sub-groups of in each case j LEDs of the total of N LEDs in order to place the LED light in the operating mode in question. This preferably applies to any operating mode in which at least one of the LEDs is switched on and at least one of the LEDs is switched off. In this way, a certain level of brightness can be achieved by switching on different subgroups of the LEDs, which can reduce the turn-on of the individual LEDs to achieve the relevant brightness level, so that overall the life of the LED lamp can be extended.

In this case, the configuration is preferably such that the different subgroups do not overlap, so that each of the total of N LEDs can only be part of one of the different subgroups. As a result, a simplified design of the control unit is made possible in particular.

Preferably, the control unit is further configured to determine which of the subgroups is turned on to place the LED light in the mode of operation considered. This makes it easier to operate the LED light.

Preferably, the LED light further comprises a detection unit which is adapted to continuously detect for each of the subgroups a respective current value, which represents a summed up over a certain period duty cycle of the respective subgroup; As a period, for example, the operating time of the LED light can be selected. On the basis of these values, that subgroup can be determined and set for activation - ie for switching on the corresponding LEDs - which has the shortest switch-on duration so far. This can extend the life of the LED lamp overall.

Advantageously, for this purpose, the control unit is further configured to determine, depending on the values that have been previously detected by the detection unit, which of the subgroups is turned on in order to put the LED light in the operating mode under consideration. With "switching on a subgroup", of course, a switching on of the LEDs of the relevant subgroup is indicated. Advantageously, in the sense of the above embodiment, the one of the subgroups whose value represents the shortest duty cycle or, if appropriate, one of the subgroups whose values represent the shortest turn-on durations is determined. The latter makes sense if at least two of several possible subgroups have the same shortest value.

According to the invention, the LED light is configured in such a way that, when the operating mode changes from a current operating mode to a subsequent operating mode, the subgroups of the current operating mode and the subgroups of the subsequent operating mode can be superimposed by control by the control unit, for which purpose a corresponding operating current is varied. This avoids that the change between the two operating modes appears "jerky".

A particularly simple design of the LED light is possible if all N LEDs have the same power. In this case, in particular structurally identical LEDs can be used. Also advantageous for a simple design, all N LEDs are arranged on a circuit board.

By way of example, the total number N of LEDs may be at least 25, so that the following applies: N ≥ 25. This makes it possible, for example, to realize a square field for emitting light with a matrix-type arrangement of 5 × 5 LEDs. Even more preferred is the total number N ≥ 49. The larger N is selected, the more different operating modes and thus brightness levels can be realized with the LED lamp.

Particularly suitable is the LED light in the form of an LED spotlight for movie lighting in interiors due to the above-mentioned relationships.

According to a further aspect of the invention, a method is provided for driving an LED luminaire according to the invention, comprising the following steps: (a) input of the dimming value into the control unit, (b) assignment of one of the operating modes to that in step (a) (d) optionally selecting one of a plurality of possible subgroups of LEDs that can be switched on to the operating mode assigned in step (b), using as a selection criterion the current values that have been previously acquired by the detection unit and (d) in a change of the mode of operation from a current mode to a subsequent mode, the subgroups of the current mode and subgroups of the subsequent mode are superimposed by a control by the control unit, for which a corresponding operating current is varied.

Fig. 1

eine schematische Skizze zu einer LED-Leuchte gemäß dem Ausführungsbeispiel,

Fig. 2

eine Skizze einer Lichtabgabefläche der LED-Leuchte bei einer Ausführungsvariante mit N = 7 x 7 = 49 LEDs und

Fig. 3

eine Skizze zu unterschiedlichen Betriebsarten im Fall einer Ausführungsvariante mit N = 3 x 3 = 9 LEDs.

The invention is explained in more detail below with reference to an embodiment and with reference to the drawings. Show it:

Fig. 1

a schematic sketch of an LED lamp according to the embodiment,

Fig. 2

a sketch of a light emitting surface of the LED lamp in a variant with N = 7 x 7 = 49 LEDs and

Fig. 3

a sketch of different operating modes in the case of a variant with N = 3 x 3 = 9 LEDs.

In Fig. 1 is a schematic diagram of an LED lamp according to the embodiment shown. The LED lamp has LEDs 2, the total number of which is generally designated N here. In this case, N ≥ 3, so there are at least three LEDs 2 are provided. The LEDs 2 are designed to emit light in an outer space of the LED light and arranged in the LED light. In the in Fig. 1 shown embodiment, nine LEDs 2 are shown by way of example, ie N = 9, the LEDs 2 are arranged in a matrix of a matrix of 3 x 3 LEDs. All N LEDs are preferably arranged on a common board 4.

In Fig. 2 an exemplary embodiment with a field of 7 x 7 = 49 LEDs is shown as an example. It shows Fig. 2 a view of the board 4 opposite to the main emission of the LED light. In particular, it can be provided that the LEDs 2 represent the only light source of the LED lamp.

The LED light may be, for example, an LED spotlight, in particular an LED spotlight for indoor movie lighting.

The total of N LEDs are each designed to emit a light with the same spectral property. In a particularly simple embodiment, all LEDs 2 have the same power. In particular, all N LEDs can be identical LEDs. In this case, the LEDs 2 may be formed, for example, for emitting white light.

Furthermore, the LED lamp has a control unit 6 for controlling the LEDs 2. In this case, the control unit 6 is adapted to set the LED light either in one of several different modes B1 , B2 , ..., wherein in each of the different modes B1 , B2, ... a respective other part number n of the total N LEDs are switched on and the remaining N - n LEDs are switched off. In this case, 0 ≤ n ≤ N.

At the in Fig. 1 Thus, for example, a first operating mode B1 can be provided, in which none of the LEDs is switched on, that is to say n = 0, a second operating mode B2 , in which one of the LEDs is switched on, that is, n = 1 , a third operating mode B3 , in which two of the LEDs are turned on, that is, n = 2, etc., so that a total of N + 2 , so here eleven different modes B1 ... B11 provided are. Since a different number n of LEDs illuminates in each operating mode, the brightness of the light emitted by the LED light is fundamentally different in each operating mode; In the case mentioned, eleven different brightness levels for the light output of the LED light can be achieved or nine different brightness levels between the operating mode in which none of the LEDs is switched on ( n = 0) and the operating mode in which all LEDs are switched on ( n = N ). In each mode of operation, each of the total of N LEDs can either be switched on or off, ie in particular not dimmed. This makes it possible in particular to achieve a brightness adjustment for the LED lamp without PWM control.

However, the number of different operating modes or brightness levels is not limited to N + 2, because fewer operating modes or brightness levels can be provided. At the in Fig. 1 3 x 3 = 9 LEDs shown, alternatively, for example, only four different modes can be provided, wherein in the first mode B1 none of the LEDs is turned on, so n = 0 , in the second mode B2 exactly three of the LEDs are turned on, ie n = 3 applies, in the third mode B3 exactly six of the LEDs are turned on, so n = 6 applies and in the fourth mode B4 all LEDs are turned on, so n = 9 applies. In this way, four different brightness levels for the light output of the LED light can be achieved.

More generally, therefore , a maximum of N + 2 can be provided for the number of different operating modes B1 , B2, ... Or brightness levels.

Advantageously, the control unit 6 is further adapted to put the LED light in one of the different modes B1 , B2, ... in dependence on a predetermined dimming value. This allows easier brightness adjustment of the LED light. In particular, the control unit 6 can have a control interface 61 for this purpose. Advantageously, it is further provided that a dimm value input by a user, analog or digital control signal via the control interface 61 is read; In this case, preferably by the control interface 61 as a function of the number of provided brightness levels or modes, ie in the context of "Functional range" of the LED lamp, a corresponding number of different control signals or dimming values offered for selection. Furthermore, it can be provided that the input control signal is subsequently interpreted in an interpretation unit 62 of the control unit 6 in order to assign one of the operating modes B1 , B2, ... To the control signal. For this purpose, it can be provided that the control signal is occupied by a dimming curve. For example, one of the operating modes B1 , B2, ... Is assigned to the control signal which comes closest to the desired amount of light in accordance with the manipulated variable or, depending on the place of use, is generally rounded up or down.

Preferably, in at least one mode of operation Bj of the different modes B1 , B2, ..., at least one of the N LEDs is turned on and at least one other of the N LEDs is turned off, with the following: Let j be exactly the part number of the total of N LEDs included in the considered operating mode Bj are turned on, then the control unit 6 is further configured to optionally one of several different subgroups U1, U2, ... of each j LEDs of the total N LEDs turn on to the LED light in the considered mode Bj offset. This preferably applies to each of the operating modes B1 , B2, ..., In which at least one of the N LEDs is switched on and at least one is switched off.

This is exemplified by the Fig. 3 explained in more detail, in which for the case N = 9 four different modes B1 ... B4 are provided. In the first line, the first operating mode B1 is sketched, in which all LEDs are switched off. The second line outlines the second operating mode B2 , in which n = 3 LEDs are switched on, in the third line the third operating mode B3, in which n = 6 LEDs are switched on, and in the fourth line, the fourth operating mode B4 , in which all nine LEDs are switched on. In the second and the third operating mode, three different possibilities of switched on and off LEDs are shown side by side.

The second operating mode B2 , in which exactly j = 3 LEDs are switched on, is now considered in more detail below, ie B2 = Bj. In this considered operating mode Bj , at least one of the LEDs 2 is switched on and at least one of the LEDs 2 off. Furthermore, three different subgroups U1, U2, U3 are formed, each of which comprises exactly j = 3 LEDs.

In Fig. 3 the first subgroup U1 is sketched in the second line on the left, in the middle the second subgroup U2 and on the right the third subgroup U3.

The control unit 6 is designed to selectively switch on one of the three subgroups U1, U2, U3 of in each case j = 3 LEDs in order to place the LED light in the second operating mode B2 or in the operating mode Bj considered.

Thus, for example, if the LED lamp is put in the second mode B2 three times in succession, the control unit 6 can switch on the first subgroup U1 for the first time , the second subgroup U2 for the second time, and the third subgroup U3 for the third time. In this way, for the second operating mode B2 compared to the hypothetical case in which one and the same subset of LEDs is activated by the control unit 6 each time the LED light is switched to the second operating mode B2 , the service life is at least approximated increase the LED light by a factor of three.

At the in Fig. 2 exemplary variant shown with 7 x 7 = 49 LEDs 49 different brightness levels can be achieved between the mode without light output ( n = 0) and the mode with maximum light output ( n = N ). In this case, due to the relationships shown, for example, with a dimming of 50%, the lifetime of the lamp can be doubled; In principle, as dimming increases, the lifetime extension that can be achieved increases linearly.

For the optional decision to be made, which of the several possible subgroups U1, U2, ... Is selected for switching on in the individual case, the control unit 6 preferably has a subgroup assignment unit 63.

As in the case of the Fig. 3 In the example shown, the different subgroups U1, U2, U3 are preferably "non-overlapping", which expresses that each of the total of nine LEDs can only be part of one of the different subgroups U1, U2, U3 .

A particularly simple embodiment of the control unit 6 can be achieved if the control unit 6 is designed to merely switch the j = 3 LEDs of one of the subgroups U1, U2, U3 on or off in order to move the LED light into the second operating mode B2 or B2. into the considered operating mode Bj . In particular, it can thus be provided that in each mode of operation, each of the total of N LEDs is either only on or off, but not dimmed as such.

A particularly simple handling of the LED light is made possible when the control unit 6 is designed to "automatically" determine which of the subgroups U1, U2, U3 is turned on to the lamp in the second operating state B2 or in the considered operating state Bj to move. In this way it can be avoided that one of the subgroups U1, U2, U3 has to be selected manually for this purpose.

For this purpose, the LED light preferably also has a detection unit 8, which is designed to continuously record a respective current value for each of the subgroups U1, U2, U3 , one, over a certain period of time, for example the operating time of the LED light , accumulated duty cycle represents. This value can then be used by the control unit 6 as a suitable selection criterion in the selection or determination of one of the subgroups U1, U2, U3 . Accordingly, the detection unit 8 is connected to the control unit 6, as in FIG Fig. 1 symbolically indicated by a double arrow 10. The detection unit 8 preferably has a memory for storing the values.

For example, the value may be an absolute time, any unit proportional to the duty cycle, or a corresponding ratio of the subgroups to each other.

In particular, in this case, the control unit 6 may be designed to determine which of the subgroups U1, U2, U3 is turned on, depending on the values representing the switch-on periods and which have previously been detected by the detection unit 8, about the LED light in the second operating mode B2 or in the considered operating mode Bj .

Preferably, the control unit 6 is designed in such a way that that one of the subgroups U1, U2, U3 is determined or determined to be switched on, the value of which represents the shortest duty cycle, or optionally one of those subgroups U1, U2, U3 whose values are the shortest duty cycle represent.

The above considerations are, of course, more general, not limited to the case N = 9 and not limited to the second mode B2 as "considered" mode Bj. It is obviously advantageous if corresponding subgroups are formed for all modes in which at least one of the LEDs is turned on and at least one is turned off.

In this case, the number of LEDs that are present in a subgroup, basically any values assumed; In particular, a subgroup may already be formed by a single LED. The control unit 6 is preferably designed to individually switch on and off or control each of the total of N LEDs.

1. (a) Eingabe eines bzw. des Dimm-Werts in die Steuereinheit 6,
2. (b) Zuordnung einer der Betriebsarten B1, B2, ... zu dem in Schritt (a) eingegebenen Dimm-Wert,
3. (c) gegebenenfalls Auswahl einer von mehreren möglichen Untergruppen U1, U2, ... von LEDs, die zu der in Schritt (b) zugeordneten Betriebsart eingeschaltet werden können, wobei als Auswahlkriterium die aktuellen Werte verwendet werden, die vorab durch die Erfassungseinheit 8 erfasst worden sind und die die aktuellen Einschaltdauern der Untergruppen U1, U2, ... repräsentieren.

The method for controlling an LED luminaire according to the invention can accordingly have the following steps:

1. (a) input of a dimming value into the control unit 6,
2. (b) assigning one of the operating modes B1 , B2, ... to the dimming value entered in step (a),
3. (c) optionally selecting one of a plurality of possible subgroups U1, U2, ... of LEDs that can be switched on in the operating mode assigned in step (b), wherein the current values are used as the selection criterion, which is detected in advance by the detection unit 8 have been and represent the current duty cycles of the subgroups U1, U2, ....

Preferably, that subgroup is selected, whose duty cycle is the shortest or one of those subgroups whose duty cycles are the shortest.

In order to avoid a "jerky" brightness change in a change from a current mode to an immediately subsequent mode, the LED light can continue to be designed such that in this change, if necessary, the subgroups of the current mode and the subgroups of the subsequent mode by a Control can be superimposed by the control unit 6, for which purpose a corresponding operating current is varied. For this purpose, the control unit 6 may in particular have a crossfade unit 64 for each subgroup. This can be realized for example by means of software or by an analog module. The output of the cross-fade unit 64 is an interface to a driver 12 of the LEDs 2; This driver 12 can be realized analog or digitized.

Claims (11)

1. LED lamp in the form of a LED spotlight for film lighting in interior spaces, having

   - LEDs (2) in a total number of N, for light output into an exterior space of the LED lamp, wherein N ≥ 3 applies and wherein each of the total N LEDs (2) is designed to emit a light with one and the same spectral property,

   - a control unit (6) for triggering the LEDs (2),

   wherein the control unit (6) is designed to move the LED lamp optionally into one of several different operating modes (B1, B2, ...),
   wherein in each of the different operating modes in each case another partial number n of the total N LEDs (2) with 0 ≤ n ≤ N, are switched on, and in each case the remaining N - n LEDs (2) are switched off,
   wherein in at least one operating mode (Bj) considered of the different operating modes (B1, B2, ...) at least one of the N LEDs is switched on and at least another of the N LEDs is switched off and thereby the following applies: If j is precisely the partial number of the total N LEDs, which are switched on in the operating mode (Bj) considered, then the control unit (6) is furthermore designed, to switch on one of several different sub-groups (U1, U2, ...) of in each case j LEDs of the total N LEDs, in order to move the LED lamp into the operating mode (Bj) considered, characterized in
   that the LED lamp is designed in such a manner that when changing the operating mode from a current operating mode to a subsequent operating mode, if applicable, the sub-groups of the current operating mode and the sub-groups of the subsequent operating mode are cross-faded via a triggering by the control unit (6), wherein for this purpose an appropriate operating current is varied.
2. LED lamp according to Claim 1,
   in which the control unit is furthermore designed to move the LED lamp in dependence on a pre-determined dimming value into one of the different operating modes (B1, B2, ...).
3. LED lamp according to Claim 1 or 2,
   wherein the different sub-groups (U1, U2, ...) are non-overlapping, so that each of the total N LEDs can only be part of one of the different sub-groups (U1, U2, ...).
4. LED lamp according to any one of the preceding claims,
   in which the control unit (6) is furthermore designed to determine which of the sub-groups (U1, U2, ...) is switched on, in order to move the LED lamp into the operating mode (Bj) considered.
5. LED lamp according to any one of the preceding claims,
   further having,

   - a detection unit (8), which is designed to continuously detect for each of the sub-groups (U1, U2, ...) an in each case current value, which represents a switch-on time of the respective sub-group summed up over a specific time period, wherein the time period is, for example, the operating duration of the LED lamp.
6. LED lamp with the features mentioned in Claims 4 and 5,
   in which the control unit is furthermore designed, in dependence on the values, which have previously been detected by the detection unit (8), to determine which of the sub-groups (U1, U2, ...) is switched on, in order to move the LED lamp into the operating mode (Bj) considered.
7. LED lamp according to Claim 6,
   wherein that of the sub-groups (U1, U2, ...) is determined, the value of which represents the shortest switch-on time or, if applicable, one of the sub-groups (U1, U2, ...) is determined, the values of which represent the shortest switch-on times.
8. LED lamp according to any one of the preceding claims,
   in which all N LEDs (2) have the same output.
9. LED lamp according to any one of the preceding claims,
   in which all N LEDs (2) are arranged on a circuit board (4).
10. LED lamp according to any one of the preceding claims,
    in which N ≥ 25, preferably N ≥ 49 applies.
11. Method for triggering a LED lamp according to Claim 7,
    comprising the steps:

    (a) input of a dimming value into the control unit (6),

    (b) assignment of one of the operating modes to the dimming value inputted in step (a),

    (c) if applicable, selection of one of several possible sub-groups (U1, U2, ...) of LEDs, which can be switched on to the operating mode assigned in step (b)" wherein as selection criterion the current values are used, which have been detected in advance by the detection unit (8) and represent of the switch-on times of the sub-groups (U1, U2, ...) and

    d) when changing the operating mode from a current operating mode to a subsequent operating mode the sub-groups of the current operating mode and the sub-groups of the subsequent operation mode are cross-faded via a triggering by the control unit (6), wherein for this purpose an appropriate operating current is varied.

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