Open-loop control and / or closed-loop control device, circuit arrangement and method for controlling light-emitting diodes in a light-emitting diode field

Abstract

The invention relates to an open-loop control or closed-loop control device for open-loop control or closed-loop control of a light-emitting diode field having n light-emitting diodes, the device having an output end, by means of which an open-loop control or closed-loop control signal for open-loop control or closed-loop control of a controllable switching element can be intercepted, the open-loop control or closed-loop control device can define the switch-on time and / or switch-off time of a pulse by means of the open-loop control signal or the closed-loop control signal, and can control one and / or more controllable switching elements to be closed or open during the determined pulse, k groups are determined or 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 I(FI)#imgabs0# and the determined switch-on time and / or switch-off time of the pulses of each group are determined by an open-loop control or closed-loop control device so that the pulses overlap as little as possible.

Description

Technical Field

[0001] The invention relates to an open-loop control and / or closed-loop control device for open-loop control and / or closed-loop control of a light-emitting diode field, the open-loop control and / or closed-loop control device having an output at which an open-loop control and / or closed-loop control signal for open-loop control and / or closed-loop control of a controllable switching element can be tapped, wherein the switch-on and / or switch-off time of a pulse can be defined by the open-loop control signal and / or closed-loop control signal and one and / or more controllable switching elements can be controlled to close or open during the determined pulse. A circuit arrangement and a method for operating the circuit arrangement. Background Art

[0002] In the light-emitting diode field, the brightness of each individual light-emitting diode is controlled via a pulse width modulated (current) signal with pulses having a pulse width PW=0 to 100%.

[0003] This is usually done by switching the light emitting diodes on at the beginning of the PWM cycle and switching them off after the switch-on period selected to achieve the desired brightness. Thus, all LEDs are switched on simultaneously, but each LED may be switched off at a different switch-off time depending on the pulse width of the pulse.

[0004] This results in that when supplying such a light-emitting diode field, in particular at the switch-on time t 接通 = 0. This in turn increases the demands on the power supply of these systems and can lead to EMC problems.

[0005] Such light-emitting diode fields are found, for example, in newly developed LED headlights, which have tens of thousands of light-emitting diodes within the light-emitting diode field. It is desirable to reduce the maximum current in the system and to make the current curve uniform overall. In order to obtain a better EMC situation and enable a more favorable design of the LED power supply. Summary of the invention

[0006] The present invention begins here.

[0007] The problem underlying the invention is to improve an open-loop control and / or closed-loop control device of the type mentioned in the introduction in such a way that a desired light distribution is achieved and at the same time reduced dynamics in the total current and in the peak current are achieved.

[0008] According to the invention, this object is achieved in that an open-loop control and / or closed-loop control device for open-loop control and / or closed-loop control of a light-emitting diode field having n light-emitting diodes has an output end, with which an open-loop control and / or closed-loop control signal for open-loop control and / or closed-loop control of a controllable switching element can be intercepted, wherein the open-loop control and / or closed-loop control device can define the switch-on time and / or switch-off time of a pulse by means of the open-loop control signal and / or closed-loop control signal and can control one and / or more controllable switching elements to be closed or opened during the determined pulse, wherein a plurality of, i.e., k, groups are determined or 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 The determined switch-on time and / or switch-off time of the pulses of each group are determined by the open-loop control and / or closed-loop control means in such a way that the individual pulses overlap as little as possible.

[0009] By means of the open-loop control and closed-loop control means according to the invention, the switch-on and switch-off times of the LEDs are selected in such a way that not all LEDs are switched on simultaneously at the beginning of a clock cycle.

[0010] This measure reduces the maximum current in the system and flattens the current curve.

[0011] It may be provided that the brightness of each light emitting diode of one of the k groups can be controlled by adjusting the pulse width of the pulse to 0 to 100% of the clock period and / or adjusting the amplitude of the pulse.

[0012] Furthermore, it can be provided that for each light-emitting diode of a group the switch-on time and / or switch-off time of the pulse can be determined as a function of the pulse width and / or the amplitude of the pulse.

[0013] Advantageously, provision is made for the determined switch-on time and / or switch-off time of the pulse to lie within a predefined clock cycle.

[0014] By means of the open-loop control and closed-loop control devices according to the present invention, it is possible to stipulate, determine or be able to determine: which pulses have a pulse width = 100%, wherein the switch-on time and switch-off time for each of these pulses can be determined as the beginning or end of the clock cycle; determine or be able to determine: which pulses have a pulse width <100%, pulses with a pulse width <100% can be merged into a sum pulse as long as the sum of the pulse widths is ≤100%; and the switch-on time and / or switch-off time of the pulse for each light-emitting diode in each group is determined or can be determined so that the sum pulse is centered within a clock cycle.

[0015] A more uniform current demand can be generated by sequentially arranging the pulses, the pulse widths of which should be cumulatively close to 100%. Similarly, the sum pulse is placed in the middle of the clock cycle. As a result, the maximum value of the current demand, which is not always to be avoided, is also moved to the middle of the clock cycle. The waveform of the current formed in this way makes it possible to avoid high peak currents at the beginning of the clock cycle and steep current increases in a short time, which may lead to EMC problems.

[0016] It is possible that the number of groups is 2≤k≤n and the start of the clock cycle for each group can be controlled to be staggered in time by a time interval Δt2 . . . Δt k .

[0017] Advantageously, the time interval Δt can be determined according to the formula Δt=clock period / k.

[0018] In this case, the start of the clock cycle is determined to be staggered by 1 / k clock cycles for all groups. This makes it possible to achieve a more uniform power consumption of the entire LED field. This makes it possible to place lower demands on the power supply of the LED field.

[0019] The invention further relates to a circuit arrangement for open-loop control and / or closed-loop control of a light-emitting diode field. The circuit arrangement according to the invention comprises an open-loop control and / or closed-loop control device according to the invention, a power supply and a light-emitting diode field, wherein the light-emitting diode field comprises at least two series circuits, each of which comprises at least one light-emitting diode and a controllable switching element associated with the light-emitting diode, wherein a control interface of each controllable switching element is connected to an output of the open-loop control and / or closed-loop control device.

[0020] In this case, it can be provided that the power supply can be regulated by means of an open-loop control and / or a closed-loop control device in such a way that the current corresponds to the current requirement of those light-emitting diodes whose associated controllable switching elements are closed.

[0021] Furthermore, it can be provided that the light-emitting diode field is divided into 2≤k≤n groups.

[0022] The division into at least two groups makes it possible to stagger the start of the clock cycles for each group by a time interval Δt and to utilize the advantages already described.

[0023] The method for operating the circuit arrangement according to the invention comprises at least the following steps:

[0024] - The open-loop control and / or closed-loop control device checks: which pulses have a pulse width = 100%;

[0025] - placing the switch-on and switch-off times for each of these pulses at the beginning or end of the clock cycle;

[0026] - The open-loop control and / or closed-loop control device checks: which pulses have a pulse width < 100%;

[0027] - Ability to combine pulses with pulse width < 100% into a sum pulse, as long as the sum of the pulse widths is ≤ 100%;

[0028] - the open-loop control and / or closed-loop control means determines the switch-on and / or switch-off time for the pulse of each light-emitting diode in each group in such a way that the sum pulse lies centrally within the clock cycle;

[0029] The open-loop control and / or closed-loop control device controls the controllable switching element to be closed or open at the determined switch-on time and / or switch-off time of the pulse.

[0030] It may also be provided that a method for operating the circuit arrangement according to the invention, which method is particularly suitable for being carried out before carrying out the above-described method, comprises at least the following steps:

[0031] - an open-loop control and / or closed-loop control device determines a pulse width for each light-emitting diode in a group or provides a pulse width to said open-loop control and / or closed-loop control device;

[0032] - an open-loop control and / or closed-loop control device determines the maximum pulse width;

[0033] - comparing the maximum pulse width with the clock cycle;

[0034] - if the maximum pulse width is shorter than the beat period, then calculate a coefficient to increase the pulse width to 100% of the beat period;

[0035] - increasing all other pulse widths of the pulses for each light-emitting diode in a group by the same factor;

[0036] - Multiply the required current demand per pulse by the inverse of the coefficient.

[0037] The brightness distribution that is mostly determined in advance remains unchanged in this approach. Due to the increase in the pulse width and the resulting reduction in the current, the total current requirement of the light-emitting diode field can be made more uniform over the clock cycle. Likewise, the maximum value of the current can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The present invention will be described in more detail below with the aid of the accompanying drawings.

[0039] Figure 1A block diagram showing an arrangement according to the invention;

[0040] Figure 2 A flow chart for explaining the determination of the switch-on time and the switch-off time is shown;

[0041] Figure 3 shows a typical current profile of a light-emitting diode field during a clock cycle;

[0042] Figure 4 Shows the on-time and power-on height Typical current variation of the LED field during one clock cycle in the case of matching;

[0043] Figure 5a , Figure 5b The light-emitting diode field with three groups is shown without displacement at the beginning of the clock cycle ( Figure 5a ) and the case where there is a displacement at the beginning of the beat cycle ( Figure 5b ) for a typical power distribution. DETAILED DESCRIPTION

[0044] exist Figure 1 The circuit arrangement 6 according to the invention shown in FIG. 1 comprises a light emitting diode field 7 formed by two series circuits 1 , 2 . Each series circuit 1 , 2 comprises a light emitting diode 3 , a resistor 4 and a controllable switching element 5 .

[0045] Corresponding to the designations of the components, a first series circuit 1 and a second series circuit 2 will be discussed below.

[0046] The series circuits 1, 2 are connected in parallel. The light-emitting diodes 3 are arranged within the series circuits 1, 2 such that their anodes are located at a common node. The resistor 4 is arranged between the diode 3 and the controllable switching element 5. In addition to the light-emitting diode field 7, the circuit arrangement 6 according to the invention also includes a power source 8. The power source 8 is a controllable power source.

[0047] Furthermore, an open-loop control and / or closed-loop control device 9 according to the invention is provided in the circuit arrangement 6 according to the invention. The open-loop control and / or closed-loop control device 9 has a plurality of outputs 10. Via these outputs 10, the open-loop control and / or closed-loop control device 9 is connected to the controllable power source 8 and the controllable switching elements 5 of the light-emitting diode field 7.

[0048] The first outputs 10 of the open-loop control and / or closed-loop control device 9 are connected to the control interfaces of the controllable switching elements 5 of the series circuits 1 and 2 of the light-emitting diode field 7. Control pulses can be sent to the switching elements 5 via these first outputs 10 in order to close or open them. The second output 10 is connected to the controllable power supply 8. A signal can be sent from the open-loop control and / or closed-loop control device 9 to the controllable power supply 8 via this second output 10 in order to adjust the current to be provided by the power supply 8. The open-loop control and / or closed-loop control device 9 is arranged so that the light-emitting diodes 3 have the desired brightness.

[0049] This is achieved in that the controllable switching element 5 associated with the light-emitting diode 3 is controlled to be closed within a clock cycle until the light-emitting diode 3 has generated the desired brightness.

[0050] The pulses are described with a pulse width in % of a clock cycle and are between 0 and 100%. The switching on and off takes place at such a high frequency that the switching on and off is not perceptible to the human eye.

[0051] Figure 2 A flow chart is shown for explaining the determination of the switch-on and switch-off times. As a preparatory measure, all pulse widths are present in the process.

[0052] At the beginning of the flow chart, a distinction is made as to whether a pulse width PW<100% exists. If this query is to be answered with "yes", the pulse with the largest pulse width is selected.

[0053] The pulse width is increased to 100% of the clock period. The current requirement is then multiplied by the inverse of the gain factor. All other pulse widths are adapted in the same way.

[0054] After this cycle, by definition, pulse width PW=100% exists. If the above query is answered with "No", the flow chart continues at the activated position.

[0055] The pulse widths are sorted according to size. Then, a pulse with a pulse width PW=100% is selected and the switch-on time and switch-off time for this pulse are determined. Usually, the switch-on time is the beginning of the clock cycle, and the switch-off time is the end of the clock cycle.

[0056] It is then checked whether there are further pulses with PW=100%.

[0057] If this query is to be answered with “yes”, the cycle begins again at the selection pulse.

[0058] If the question should be answered with "No", select the next smaller The pulse width of this pulse is defined as the first sum pulse. Subsequently, the remaining area is calculated, which means the area that still exists after the sum pulse is subtracted from the beat period.

[0059] A further query is started as to whether a pulse is present such that the pulse width PW is smaller than the remaining range.

[0060] If the query is answered with "No", the switch-on and switch-off times of the individual pulses of the sum pulse can be determined. Here, according to the invention, this is done so that the entire sum pulse is located centrally within the clock cycle.

[0061] If the query is answered with "yes", the pulse is selected and a new sum pulse is calculated as the sum of the old sum pulse plus the pulse width of the selected pulse.

[0062] The calculation of the remaining area begins again with this new sum pulse and the cycle is executed again.

[0063] If no pulses are found that are adapted to the remaining range that exists, a check is performed to determine whether all pulses have been selected.

[0064] If this is the case, the process ends. If the query is answered with "No", the next smaller pulse that has not yet been selected is selected and the cycle is executed again from this point.

[0065] Figure 3 The typical current profile of a light-emitting diode field controlled according to the invention during a clock cycle is shown.

[0066] For certain applications of LED fields, such as in headlights, light distributions with different brightness levels are desired. For this reason, each LED is driven individually. By switching the individual LEDs on and off in a targeted manner, the desired average brightness of the LEDs can be adjusted.

[0067] In this case, the light-emitting diodes are energized with 100% of the desired brightness during the entire clock cycle.

[0068] After reaching the desired average brightness, the light-emitting diodes having a different desired brightness are switched off again before the end of the clock cycle.

[0069] For light-emitting diodes having a desired brightness of less than 100%, this results in the possibility of shifting the switch-on and switch-off times within the clock cycle.

[0070] According to the present invention, Figure 3The current profile is shown, wherein the pulses of the individual light-emitting diodes are arranged in time such that the individual switch-on and switch-off times overlap as little as possible.

[0071] Here, Figure 3 The current distribution during one clock cycle is shown for eight light-emitting diodes selected by way of example, which have the pulse widths indicated below.

[0072] led 8 7 6 5 4 3 2 1 PW(%) 84.00 100.00 92.62 89.03 75.00 67.74 38.62 17.75

[0073] The light emitting diodes are operated temporally in such a way that a maximum value occurs in the middle of the clock cycle in order to minimize undesired current peaks at the beginning of the clock cycle.

[0074] Figure 3 The following temporal distribution is based on the light emitting diodes.

[0075] In this case, 1 represents a closed controllable switching element, so that the selected light-emitting diode is energized, and 0 represents an open controllable switching element.

[0076] Time t[ms] 8 7 6 5 4 3 2 1 0 0 1 0 0 0 0 0 0 0.18 0 1 1 0 0 0 0 0 0.27 0 1 1 1 0 0 0 0 0.40 1 1 1 1 0 0 0 0 0.62 1 1 1 1 1 0 0 0 0.81 1 1 1 1 1 1 0 0 1.98 1 1 1 1 1 1 1 0 2.94 1 1 1 1 1 1 0 1 3.39 1 1 1 1 1 1 1 0 4.19 1 1 1 1 1 1 0 0 4.38 1 1 1 1 1 0 0 0 4.60 1 1 1 1 0 0 0 0 4.73 0 1 1 1 0 0 0 0 4.82 0 1 1 0 0 0 0 0 5.00 0 1 0 0 0 0 0 0

[0077] Figure 4 The typical current profile of a light-emitting diode field controlled according to the invention during a clock cycle is shown with an adaptation of the switch-on period to the current level.

[0078] For the situation that occurs, that no light-emitting diode in the light-emitting diode field is to achieve 100% brightness, it is entirely conceivable to use a pulse for each light-emitting diode such as Figure 3 As shown in FIG. 8 , the scalars are assigned to a clock cycle.

[0079] To optimize the current consumption and the dynamics in the total current, the Figure 4 In the case of the current change shown in , the driving of each light emitting diode is carried out as follows.

[0080] The light-emitting diode with the longest switched-on period is set to 100% of the switched-on time within a clock cycle and at the same time the current level for this light-emitting diode is reduced by this factor.

[0081] The effective brightness of the light-emitting diodes remains unchanged in this process.

[0082] Correspondingly, the other light-emitting diodes are energized longer by the same factor. The required current is multiplied by the inverse of this factor and the required current is reduced thereby.

[0083] Only after this process has been carried out, the switch-on and switch-off times are determined for the light-emitting diodes in the light-emitting diode field. Figure 3 The same method as already described was used.

[0084] Here, Figure 4 The current distribution during one clock cycle is shown after the pulse width and the current requirement have been adapted for eight light-emitting diodes selected by way of example, which have the pulse widths indicated below.

[0085] led 8 7 6 5 4 3 2 1 PW in % 90.70 96.13 100.00 96.13 80.98 75.58 41.70 19.17

[0086] The individual light-emitting diodes are again arranged as sequentially as possible, so that the individual switch-on and switch-off times overlap as little as possible.

[0087] Figure 4 This results from the following temporal distribution of the individual light emitting diodes within a clock cycle.

[0088] Time t[ms] 8 7 6 5 4 3 2 1 0 0 1 1 0 0 0 0 0 0.13 0 1 1 0 0 0 0 1 0.19 0 1 1 1 0 0 0 1 0.23 1 1 1 1 0 0 0 1 0.48 1 1 1 1 1 0 0 1 1.09 1 1 1 1 1 1 0 0 1.46 1 1 1 1 1 1 1 0 3.54 1 1 1 1 1 1 0 0 4.52 1 1 1 1 0 1 0 0 4.77 0 1 1 1 0 1 0 0 4.81 0 0 1 1 0 1 0 0 4.87 0 0 1 1 0 0 0 0 5.00 0 1 1 0 0 0 0 0

[0089] In this case, 1 represents a closed controllable switching element, so that the selected light-emitting diode is energized, and 0 represents an open controllable switching element.

[0090] The advantages of this procedure are the reduction in the dynamics of the total current and of the peak current.

[0091] exist Figure 5a , Figure 5b Another optimization scheme is shown in FIG. These figures show the power distribution of a light-emitting diode field having three groups. Here, each group within the light-emitting diode field shows a similar Figure 3 The current changes described in .

[0092] Here, Figure 5a The following situation is shown: All groups use the same time as the start of their respective clock cycle. The power consumption of each group within the light-emitting diode field is added to each other. Figure 5a In the example of FIG. 1 , a power of up to 270 W appears at the input of this circuit in peak value.

[0093] exist Figure 5b : The situation is shown in which the start of the clock cycle for each group is offset in time by a time interval Δt. In this case, the groups are each activated with an offset of one third of the clock cycle.

[0094] From this we get Figure 5b The power distribution is shown in .

[0095] Due to the overlap of the three groups offset in time, in this example only a maximum input power of 190 W still occurs. Likewise, the power distribution changes more evenly.

[0096] The inventive activation of a plurality of groups within a light-emitting diode field has a positive effect on the power consumption.

[0097] Reference numerals list

[0098] 1.2 Series Circuit

[0099] 3 Diode

[0100] 4. Resistors

[0101] 5 Controllable switching elements

[0102] 6 Circuit Layout

[0103] 7 LED Field

[0104] 8 Power supply

[0105] 9 Open-loop control and / or closed-loop control devices

[0106] 10 Output

Claims

1. An open-loop control or closed-loop control device (9) for open-loop control or closed-loop control of a light-emitting diode field (7) having n light-emitting diodes (3), the open-loop control or closed-loop control device having an output (10) at which an open-loop control signal or a closed-loop control signal for open-loop control or closed-loop control of a controllable switching element (5) can be tapped, in, Using the open-loop control or closed-loop control device (9): - The on-time and / or off-time of the pulse can be defined by an open-loop control signal or a closed-loop control signal; - one or more controllable switching elements (5) can be controlled to close or open during a determined pulse period; It is characterized in that - can determine multiple, i.e. k, groups; Each light emitting diode (3) 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 - the brightness of each light emitting diode (3) in one of the k groups can be controlled by adjusting the pulse width of the pulse to 0 to 100% of the clock cycle, and Using the open-loop control or closed-loop control device (9): - it is possible to determine which pulses have a pulse width=100%, wherein the switch-on time and switch-off time for each of these pulses can be determined as the beginning or end of the clock cycle; - Ability to determine: which pulses have a pulse width < 100%; - can combine pulses with pulse width < 100% into a sum pulse, as long as the sum of the pulse widths is ≤ 100%; The switch-on and / or switch-off time of the pulse for each light-emitting diode (3) in each group can be determined in such a way that the sum pulse lies centrally within a clock cycle.

2. The open-loop control or closed-loop control device (9) according to claim 1, characterized in that: The brightness of each light emitting diode (3) in one of the k groups can be controlled by adjusting the amplitude of the pulse.

3. The open-loop control or closed-loop control device (9) according to claim 1 or 2, characterized in that: For each light-emitting diode (3) of a group, the switch-on time and / or switch-off time of the pulse can be determined based on the pulse width and / or the amplitude of the pulse.

4. The open-loop control or closed-loop control device (9) according to claim 1 or 2, characterized in that: The determined switch-on time and / or switch-off time of the pulse lies within a predefined clock cycle.

5. The open-loop control or closed-loop control device (9) according to claim 1 or 2, characterized in that: The number of groups is 2≤k≤n, and the start of the clock cycle for each group can be controlled to be staggered in time by a time interval Δt2 . . . Δt k .

6. The open-loop control or closed-loop control device (9) according to claim 5, characterized in that: The time interval Δt can be determined according to the formula Δt=clock period / k.

7. A circuit arrangement (6) for open-loop or closed-loop control of a light-emitting diode field (7), the circuit arrangement comprising: - an open-loop control or closed-loop control device (9) according to any one of claims 1 to 6, - a power supply (8), - a field of light emitting diodes (7), in, The light emitting diode field (7) comprises at least two series circuits (1, 2), each of which comprises at least one light emitting diode (3) and a controllable switching element (5) associated with the light emitting diode (3), wherein a control interface of each controllable switching element (5) is connected to an output (10) of an open-loop control or closed-loop control device (9).

8. The circuit arrangement (6) according to claim 7, characterized in that The power supply (8) can be adjusted by an open-loop control or closed-loop control device (9) so that the current meets the current requirement of the following light-emitting diode (3), and the controllable switch element (5) equipped with the light-emitting diode is closed.

9. Method for operating a circuit arrangement (6) according to claim 7 or 8, wherein: The method comprises at least the following steps: - the open-loop control or closed-loop control device (9) checks: which pulses have a pulse width = 100%; - placing the switch-on and switch-off times for each of these pulses at the beginning or end of the clock cycle; - an open-loop control or closed-loop control device (9) checks: which pulses have a pulse width <100%; - Ability to combine pulses with pulse width < 100% into a sum pulse, as long as the sum of the pulse widths is ≤ 100%; - an open-loop control or closed-loop control device (9) determines the switch-on and / or switch-off time of the pulse for each light-emitting diode (3) in each group so that the total pulse lies centrally within a clock cycle; - an open-loop control or closed-loop control device (9) controls the controllable switching element (5) to be closed or opened for a determined switch-on time and / or switch-off time of the pulse.

10. Method for operating a circuit arrangement (6) according to claim 7 or 8, wherein: The method comprises at least the following steps: - an open-loop control or closed-loop control device (9) determines the pulse width for each light-emitting diode (3) in a group, or provides the pulse width to the open-loop control or closed-loop control device (9); - an open-loop control or closed-loop control device (9) determines the maximum pulse width; - comparing the maximum pulse width with the clock cycle; - if the maximum pulse width is shorter than the beat period, then calculate a coefficient to increase the pulse width to 100% of the beat period; - increasing all other pulse widths of the pulses for each light-emitting diode (3) in a group by the same factor; - Multiply the current demand required for each pulse by the inverse of the coefficient.

11. The method according to claim 10, characterized in that The method is intended to be carried out before carrying out the method according to claim 9.

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