Control device, circuit device and method

Abstract

The invention relates to a control device for controlling a light-emitting diode field having n LEDs, wherein n>2, the control device having output terminals at which control signals for controlling controllable switching elements can be obtained, the control device defining a switch-on time point and / or a switch-off time point (I) of a pulse by means of the control signals and being able to control one or more controllable switching elements during a defined pulse so as to close or open, wherein a number of k groups can be determined, each LED being assigned to one of the k groups, so that each of the k groups contains m j light-emitting diodes, where 1≤j≤k and #imgabs0# can determine the reference time point a for each group j =a 1 …a k , and can be based on the reference time point a j =a 1 …a k Determine the on-time point and / or off-time point of the pulse of each LED of each group #imgabs1# where 1≤p j ≤m j .

Description

Technical Field

[0001] The invention relates to a control device for controlling a light emitting diode field having n LEDs, wherein n>2, the control device having outputs at which control signals for controlling controllable switching elements can be obtained, with which the switch-on time and / or switch-off time of a pulse can be defined by means of the control signals And one or more controllable switching elements can be controlled to close or open during a determined pulse.

[0002] The invention further relates to a circuit arrangement and a method for operating the circuit arrangement. Background Art

[0003] In the light emitting diode field, the brightness of each individual pixel is controlled by a pulse width modulated (current) signal having pulses with a pulse width PW=0...100%.

[0004] In today's systems, all LEDs in the light-emitting diode field are usually ein = 0 and then at the end of their respective pulses at time point Turn off in sequence.

[0005] This results in a strong pulse current load in the supply of such a light-emitting diode field, especially at the switch-on time t ein = 0. This in turn increases the power requirements for these systems and may lead to EMV (electromagnetic compatibility) issues.

[0006] Such LED fields are found, for example, in newly developed LED headlights, which have tens of thousands of LEDs in the field. Here, it is desirable to reduce the maximum current in the system and to make the current curve more uniform overall in order to achieve better EMC conditions and a more favorable LED power supply concept.

[0007] The present invention addresses this point. Summary of the invention

[0008] The object of the present invention is to specify a control device, a circuit arrangement and a method by means of which the maximum value of the current consumed by a light emitting diode field, ie the maximum current, can be reduced.

[0009] According to the invention, the object is achieved in a first variant by a control device for controlling a light-emitting diode field having n LEDs, where n>2, the control device having outputs at which control signals for controlling controllable switching elements can be obtained, with which the switch-on time and / or switch-off time of the pulses can be defined by means of the control signals One or more controllable switch elements (4) can be controlled to close or open during a determined pulse, wherein the number of k groups can be determined, each LED is assigned to one of the k groups, so that each of the k groups contains m j light-emitting diodes, where 1≤j≤k and A reference time point a can be determined for each group j =a1…a k , and can be based on the reference time point a j =a1…a k Determine the on-time and / or off-time of the pulse for each LED of each group Where 1≤p j ≤m j .

[0010] The individual LEDs of the light emitting diode field are grouped and assigned different reference time points to determine the switch-on time point and / or switch-off time point so that the pulses are distributed over the clock cycle. This measure reduces the maximum current in the system and flattens the current curve.

[0011] The required brightness distribution usually has a small gradient in brightness between adjacent LEDs, ie adjacent LEDs must have a similar brightness and therefore a similar pulse. This is the case in particular when the light-emitting diode field is used in a headlamp and the target light distribution is intended there.

[0012] In order to maximize the advantages of the proposed invention, it is therefore advantageous to assign each LED to one of the k groups so that adjacent LEDs are assigned to different groups. The LEDs in a group should be distributed so that no LED blocks of adjacent light emitting diodes are formed within a group.

[0013] The following is an example of how the light-emitting diodes can be advantageously allocated to k groups. It is assumed that this is a matrix LED system in which the LEDs are arranged in columns and rows. Other geometries can be easily divided in a similar manner.

[0014] For k = 2, the individual LEDs of the light-emitting diode field should be allocated to group 1 and group 2 as follows:

[0015] 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2…

[0016] 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1…

[0017] 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2…

[0018] …

[0019] For k=3, the individual LEDs of the light-emitting diode field can be assigned to groups 1, 2 and 3 as follows:

[0020] 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3…

[0021] 2 3 1 2 3 1 2 3 1 2 3 1 2 3 1…

[0022] 3 1 2 3 1 2 3 1 2 3 1 2 3 1 2…

[0023] …

[0024] For k=5, an advantageous allocation of the individual LEDs of the light-emitting diode field is, for example, as follows:

[0025] 1 4 2 5 3 1 4 2 5 3…

[0026] 2 5 3 1 4 2 5 3 1 4…

[0027] 3 1 4 2 5 3 1 4 2 5…

[0028] 4 2 5 3 1 4 2 5 3 1…

[0029] …

[0030] Advantageously, the reference time point a j =a1…a k Can be randomly selected. This saves computational effort in the control device.

[0031] However, the goal may be to separate the switch-on and switch-off times as far apart as possible from one another, since a reduction in the maximum current is achieved by not switching on all LEDs simultaneously or briefly one after the other.

[0032] Advantageously, the reference time point a j =a1…a k It can be determined as follows:

[0033] k=1:a1 can be freely selected,

[0034] k=2:a1=0,a2=T,

[0035] k>2:a1=0,

[0036] and i=1...k-2,

[0037] Where T is the clock period.

[0038] By determining the reference time point a j=a1…a k The on time point and the off time point of the pulse for each LED in a group can be determined.

[0039] It can be provided that the on-time point of the pulse for each LED in a group can be calculated according to the following formula based on a

[0040]

[0041] And the turn-off time point of the pulse for each LED in a group can be calculated according to the following formula:

[0042]

[0043] Among them, a j =a1…a k ,

[0044] =The pulse width of the pth light-emitting diode in the jth group, in % of T.

[0045] The switch-on and switch-off points in time of the pulse for each light-emitting diode in a group can be calculated for all desired implementation forms according to the given formula.

[0046] For the situation mentioned at the beginning, all LEDs should be turned on at the beginning of the clock cycle, which means that the reference time point a j = 0. If we insert this value of a into the formula, we get and All pulses are therefore switched on at the beginning of a clock cycle and switched off again after the pulse duration of each light-emitting diode.

[0047] The same principle applies if all LEDs are to be switched off simultaneously at the end of the clock cycle and a separate switch-on time must be calculated for each pulse. In this case, the reference time a j =T is inserted into the formula. It is easy to see that the pulse for each light emitting diode has its own turn-on time point and a common turn-off time point at the end of the clock cycle.

[0048] For each reference time point a within the clock cycle j , the formula shows how long each pulse is turned on before the reference time point and how long each pulse is turned off after the reference time point. Based on the given formula, the pulses are distributed as evenly as possible within a clock cycle.

[0049] Since the number of k groups to be formed is limited by technical possibilities, k should be chosen according to the principle of "as large as necessary, but as small as possible".

[0050] According to the invention, the object is achieved in a second variant in that the control device

[0051] - According to the formula Calculate pulse width PW i The average value M PW

[0052] - Based on the average value M PW According to the formula Determine the number of k groups,

[0053] - Assign each LED to one of k groups.

[0054] According to the invention, the control device can be designed such that it can store simulation results to determine the optimal number of k.

[0055] It can then be provided that the method for creating a control device comprises at least the following steps:

[0056] - simulating in the simulation the desired brightness distribution to be achieved with the aid of the light-emitting diode field,

[0057] - Determine the pulses of the individual LEDs in a group for the desired brightness distribution with the aid of simulation,

[0058] - Current distribution in the LED field based on pulse simulation for different number of groups,

[0059] - determine the optimal number of k groups based on the current distribution,

[0060] - Transmitting information determined on the basis of the simulation to a control device.

[0061] The invention further relates to a circuit arrangement for controlling a light emitting diode field. The circuit arrangement according to the invention comprises a control device according to the invention, a current source for each LED and a light emitting diode field, the light emitting diode field comprising at least two series circuits, each of which comprises at least one light emitting diode and a controllable switching element, the control terminal of each controllable switching element being connected to an output of the control device.

[0062] In this context, it can be provided that each current source of the circuit arrangement according to the invention can be regulated by the control device, wherein when the controllable switching element is closed, the current i=i max , and when the controllable switching element is turned on, the current i=0.

[0063] The method for operating a circuit arrangement according to the invention comprises at least the following steps:

[0064] - the number of k groups is determined by the control device or is transmitted to the control device or is determined randomly,

[0065] - assign each LED to a group,

[0066] - Determine a reference time point a for each group j =a1…a k ,

[0067] -Based on the reference time point a j =a1…a k Determine the on and off time points of the pulses for each light emitting diode of each group

[0068] The control device (1) determines the switching-on time and switching-off time of the pulses of each light-emitting diode of each group The controllable switching element is controlled to be closed or opened.

[0069] The method for operating the second variant of the circuit arrangement also comprises at least the following steps:

[0070] -According to the formula Calculate all pulse widths PW i The average value M PW

[0071] - According to the average value M PW According to the formula Determine the number of k groups,

[0072] - Assign each LED to one of k groups.

[0073] The advantage of the present invention is that as the number of groups increases, the maximum current in the light emitting diode field decreases significantly and becomes more continuous.

[0074] Since the number of groups cannot reasonably be increased indefinitely, the invention also provides the possibility of achieving a reasonable cost / benefit trade-off. BRIEF DESCRIPTION OF THE DRAWINGS

[0075] The present invention is described in detail below with reference to the accompanying drawings. The accompanying drawings are as follows:

[0076] Figure 1 A block diagram showing a circuit arrangement according to the invention for controlling a light emitting diode field;

[0077] Figure 2a , 2b A flow chart is shown for illustrating the determination of reference time points and switch-on and switch-off time points;

[0078] Figure 3An exemplary diagram showing a pulse distribution according to the present invention when k=5;

[0079] Figure 4 The simulated current distribution for different group numbers for the real brightness distribution is shown. DETAILED DESCRIPTION

[0080] Figure 1 A block diagram of a circuit arrangement 5 according to the invention for controlling a light-emitting diode field 2 is shown.

[0081] The circuit arrangement 5 according to the invention can be realized, for example, by an integrated circuit, in particular a commercial chip or an ASIC. Other embodiments of the circuit arrangement 5 are entirely conceivable.

[0082] The light-emitting diode field 2 is assumed here to be a matrix LED system, such as is used in newly developed motor vehicle headlights.

[0083] Individual light emitting diodes LED 11 ,LED 12 , ... are arranged in rows and columns with respect to one another. However, the invention is not limited to a light emitting diode field having light emitting diodes arranged in rows and columns.

[0084] It is easy to imagine that the light emitting diode field 2 has light emitting diodes LED 11 ,LED 12 , different arrangements of…

[0085] Today's headlamps use 15,000 to 25,000 LEDs. 11 ,LED 12 ,…LED system.

[0086] The individual LEDs can be operated by means of a controllable switch element 4 which is controlled to be switched on or off. The individual LEDs are set to be switched on or off during the duration of the controllable switch element 4 being closed. 11 ,LED 12 ,…’s brightness.

[0087] Individual light emitting diodes LED 11 ,LED 12 ,… can be determined with the aid of image data, which can be transmitted from the controller 8 to the control device 1.

[0088] It is also conceivable to transmit the desired brightness value directly to the control device 1 .

[0089] The controllable switching element 4 is switched on and off at a high frequency that is invisible to the human eye.

[0090] In addition to the light emitting diode field 2, the circuit arrangement 5 according to the invention comprises at least one current source 6. The current source 6 is an adjustable current source 6.

[0091] It is conceivable that the circuit arrangement 5 according to the invention provides a circuit for each light emitting diode LED in the light emitting diode field 2. 11 ,LED 12 , ... has a current source 6 and a controllable switching element 4. Such a design is possible, for example, in the novel LED headlamp mentioned at the beginning.

[0092] Furthermore, at least one control device 1 according to the invention is provided in the circuit arrangement 5 according to the invention. The control device 1 preferably has a plurality of outputs 3. The control device 1 is connected via these outputs 3 to an adjustable current source 6 and a controllable switching element 4 of the light emitting diode field 2.

[0093] The control device may also have at least one input 9. For example, image data for determining the required brightness can be transmitted via this input.

[0094] The control device 1 according to the invention is designed such that the light emitting diodes LED for implementing the light emitting diode field 2 11 ,LED 12 ,…the processing steps required to obtain the desired brightness distribution can be run autonomously or independently.

[0095] This is achieved in the control device 1 according to the invention by firstly determining the number of k groups and assigning each LED to one of the k groups.

[0096] On the one hand, the required number of groups can be determined by calculation in the control device 1 during operation.

[0097] It is also conceivable to predetermine the number of groups and transmit it to the control device 1 .

[0098] The control device 1 is also provided with a device for determining a reference time point a j =a1…a k Unit 7 of

[0099] Reference time point a j =a1…a k It can be determined in different ways. If the computational effort is to be minimized, the value can be selected randomly, for example, using a random generator.

[0100] The unit 7 is preferably designed in such a way that it calculates the reference time a from the determined group value. j =a1…a k .

[0101] In the circuit arrangement according to the invention, unit 7 is designed such that it determines the reference time a as follows, taking into account the number of groups: j =a1…a k :

[0102] k=1:a1 can be freely selected,

[0103] k=2:a1=0,a2=T,

[0104] k>2:a1=0,

[0105] and i=1...k-2,

[0106] Where T is the clock period.

[0107] Then, based on the available reference time point a j =a1…a k According to the control device 1 of the present invention, the on and off time points of the pulses of each LED in a group can be determined.

[0108] For this purpose, the switch-on time and switch-off time for calculating the pulses of each LED in a group are stored in the unit 7. In the current case, the following formula is provided to the unit:

[0109] Connection time

[0110] Shutdown time

[0111] Based on the determined switch-on time or switch-off time, the controllable switching element 4 is controlled to be closed or opened.

[0112] When the controllable switch element is closed, the adjustable current source provides the required current i in order to make the selected light emitting diode emit light and achieve the desired brightness distribution.

[0113] Figure 2a , 2b A flow chart is shown for better explanation of the determination of the reference time and the switching-on and switching-off times. Figure 2a The outer loop is shown and Figure 2b The inner loop is shown.

[0114] As a preparatory measure, Figure 1 One of the variants described in , determines the number of groups k and assigns each light emitting diode to a group, so that each group contains m j This information is entered into the system in a suitable manner.

[0115] The flowchart begins in an outer loop, in which the individual groups are traversed or executed one after another. Thus, the value of j runs from j=1 to j=k.

[0116] First, set j:=1, that is, consider the first group among the k groups.

[0117] In a first step, a reference time a1 for the first group is now determined according to one of the proposed methods. As already explained, this can be done, for example, randomly, according to a stored table or by using the formula explained.

[0118] After determining the reference time point for the group currently under consideration, the inner loop of the application is started.

[0119] In the inner loop, for each assigned LED p of the group considered in this traversal j The switch-on time and the switch-off time are determined recursively.

[0120] p j The value of traverses all values ​​until the corresponding group m is reached j The number of LEDs in the

[0121] First, j=1, so that the first group of light emitting diodes p1 is traversed.

[0122] For this purpose, p1 is initially set to :=1, ie the first light-emitting diode of the first group is taken into account.

[0123] Next, the switch-on time and the switch-off time of the light-emitting diode are determined based on the reference values ​​for the first group.

[0124] If this is achieved, the next step is to check p j Does the value of correspond to m j The value of , i.e., whether the inner loop has processed all the LEDs of the considered group.

[0125] If the answer to the query is "no", the value of pj is increased by 1 and the inner loop is run again.

[0126] If the answer to the query is "yes", the inner loop ends and returns to the outer loop.

[0127] In this case, a check is performed to determine whether the value of j corresponds to the value of k and thus whether all groups have been processed.

[0128] If the answer to the query is "no", the value of j is increased by 1, and the next group is considered. The recursion starts again.

[0129] If the query is answered with "yes", then all required calculations have been performed. The process ends.

[0130] Figure 3An exemplary diagram of a pulse distribution determined according to the invention for k=5 is shown.

[0131] On the x-axis is plotted time, in this case the clock period T.

[0132] The current of the adjustable current source 6 is plotted on the y-axis.

[0133] In the on state, the current i=i max , i=0 in the off state.

[0134] With the help of a j =a1…a5 The calculation method described is based on Figure 1 The computational model explained in results in the following reference time points:

[0135]

[0136] Based on these reference time points, by using Figure 1 The calculation formula given in determines the turn-on time point and the turn-off time point of the pulse for each light-emitting diode of each group.

[0137] This example shows a pulse in each of 5 groups. This means that there will be only one LED in each group. In practice, multiple / large numbers of LEDs are assigned to one group. The assumption that one LED is assigned to each of the k groups is only for the purpose of Figure 3 Clearer.

[0138] By determining the reference time and calculating the switch-on and switch-off times according to the invention, a uniform distribution of the pulses over the clock cycle is achieved.

[0139] In reality, a plurality of LEDs LED of LED field 2 are assigned to each group 11 ,LED 12 ,… Each of these light emitting diodes has a pulse for setting a desired brightness.

[0140] Therefore, the current required within one clock cycle is not constant i=i max Or i=0, but must be set according to the current requirement of the switched-on light-emitting diode.

[0141] The object of the invention is to reduce the maximum current in a circuit arrangement and to harmonize the current curve.

[0142] Figure 4 The simulated current distribution for different group numbers for the real brightness distribution is shown. In the present case, the group number k is not determined, but different numbers are compared to illustrate the influence of the group number k on the current distribution.

[0143] The switch-on and switch-off times are based on Figure 1 Calculated using the formula described in .

[0144] The simulation involves a realistic arrangement of thousands of LEDs that are Figure 1 The criteria shown in are assigned to different groups.

[0145] Here:

[0146] L1 represents the current curve when k=1. If all light-emitting diodes are turned on when a1=0,

[0147] L2 represents the current curve when k=2, where a1=0, a2=T is assumed.

[0148] L3 represents the current curve when k=3, where a1=0, a2=T / 2, a3=T,

[0149] L4 represents the current curve when k=5, assuming that a1=0, a2=T / 4, a3=T / 2, a4=3T / 4, and a5=T.

[0150] Here max Assume that it is dimensionless and i max =1.

[0151] As a result, it can be seen here that as the number of groups increases, the maximum current decreases significantly and the current curve becomes flatter and more continuous. However, as the number k increases, the reduction in the maximum current becomes smaller, which emphasizes the importance of determining the required number of groups shown. In order to achieve this, a cost / benefit trade-off must be made here, especially with the help of the present invention.

[0152] List of reference numerals:

[0153] 1 Control device

[0154] 2 LED Field

[0155] 3 Output

[0156] 4 Controllable switching elements

[0157] 5 Circuit Devices

[0158] 6 Current Source

[0159] 7 Units for determining reference time points

[0160] 8 Controller

[0161] 9 Input

[0162] led 11 ,LED 12 ,… Light Emitting Diode

[0163] Switching on or off time

[0164] a j =a1…a k Reference time point

Claims

1. A control device (1) for controlling a light-emitting diode field (2) having n LEDs, wherein n>2, the control device having outputs (3) at which control signals for controlling controllable switching elements (4) can be obtained, The control device (1) is suitable for: - Define the on and off time points of the pulse through the control signal - controlling one or more controllable switching elements (4) to close or open during a specific pulse, the switch-on time and switch-off time of the specific pulse being defined by the control signal, It is characterized in that The control device (1) is suitable for: - determining the number of k groups of LEDs or transmitting the number of k groups of LEDs, - Assign each LED to one of the k groups, so that each of the k groups contains m j light-emitting diodes, where 1≤j≤k and - Determine a reference time point a for each group j =a1…a k , -Based on the reference time point a j =a1…a k Determine the on and off time points of the pulses for each LED of each group Where 1≤p j ≤m j .

2. The control device (1) according to claim 1, characterized in that Each LED is assigned to one of the k groups such that adjacent LEDs are assigned to different groups.

3. The control device (1) according to claim 1 or 2, characterized in that: The reference time point a j =a1…a k Can be selected randomly.

4. The control device (1) according to claim 1 or 2, characterized in that: The control device (1) is adapted to determine the reference time point a as follows j =a1…a k : k=1: a1 can be freely selected, k=2:a1=0,a2=T, k>2:a1=0, and i=1...k-2, Where T is the clock period.

5. The control device (1) according to claim 1 or 2, characterized in that: The control device (1) is adapted to calculate the on-time point of the pulse for each LED in a group according to the following formula based on the reference time point: Among them, a j =a1…a k , The unit is a percentage of T, where T is the clock period.

6. The control device (1) according to claim 1 or 2, characterized in that: The control device (1) is adapted to: calculate the pulse turn-off time point for each LED in a group according to the following formula based on the reference time point: Among them, a j =a1…a k , The unit is a percentage of T, where T is the clock period.

7. The control device (1) according to claim 5 or 6, It is characterized in that The control device (1) is suitable for: -According to the formula Calculate all pulse widths PW i The average value M PW , - According to the average value M PW According to the formula Determine the number of k groups, - Assign each LED to one of k groups.

8. A method for programming a control device (1) according to any one of claims 1 to 7, comprising at least the following steps: - simulating in a simulation the desired brightness distribution to be achieved with the aid of the light-emitting diode field (2), - Determine the pulses of the individual LEDs in a group for the desired brightness distribution with the aid of simulation, - for different numbers of groups, the current distribution in the light emitting diode field (2) based on pulse simulation, - determine the optimal number of k groups based on the current distribution, - transmitting information determined on the basis of the simulation to a control device (1).

9. A circuit arrangement (5) for controlling a light emitting diode field (2), comprising: - A control device (1) according to any one of claims 1 to 7, - a current source (6) for each LED, - a field of light emitting diodes (2), The light emitting diode field (2) comprises at least two series circuits, each of which comprises at least one light emitting diode and a controllable switch element (4), wherein a control terminal of each controllable switch element (4) is connected to an output end (3) of a control device (1).

10. The circuit arrangement (5) as claimed in claim 9, characterized in that Each current source (6) of the circuit arrangement (5) can be regulated by the control device (1), wherein when the controllable switching element is closed, the current i=i max , and when the controllable switching element is turned on, the current i=0.

11. A method for operating a circuit arrangement (5) having the features of claim 9, comprising at least the following steps: - the number of k groups is determined by the control device (1) or is transmitted to the control device (1) or is determined randomly, - assign each LED to a group, - Determine a reference time point a for each group j =a1…a k , -Based on the reference time point a j =a1…a k Determine the on and off time points of the pulses for each light emitting diode of each group The control device (1) determines a specific switching-on time and a specific switching-off time for the pulses of each light-emitting diode of each group. The controllable switch element (4) is controlled to be closed or opened.

12. The method according to claim 11, comprising at least the following steps: -According to the formula Calculate all pulse widths PW i The average value M PW , - According to the average value M PW According to the formula Determine the number of k groups, - Assign each LED to one of k groups.

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