EP4691183A1

EP4691183A1 - Pixelated light source and method for operating a pixelated light source

Info

Publication number: EP4691183A1
Application number: EP24711989.4A
Authority: EP
Inventors: Florian Wittmann; Martin Moritz; Jannik MORITZER; Manuel Wild
Original assignee: Ams Osram International GmbH
Current assignee: Ams Osram International GmbH
Priority date: 2023-04-06
Filing date: 2024-03-12
Publication date: 2026-02-11
Also published as: WO2024208546A1

Abstract

A pixelated light source (1) is specified herein, comprising: - a plurality of independently controllable light emitters (2), and - an integrated circuit (3) providing a plurality of pulse width modulated electrical currents (I) to the plurality of light emitters (2), wherein - current pulses (P) within different pulse width modulated electrical currents (I) that are provided by the integrated circuit (3) are phase shifted with respect to each other according to a deterministic or pseudo-random pattern. Further, a method for operating a pixelated light source is specified herein.

Description

PIXELATED LIGHT SOURCE AND METHOD FOR OPERATING A PIXELATED LIGHT SOURCE

A pixelated light source and method for operating a pixelated light source are speci fied herein .

At least one obj ect of certain embodiments is to speci fy a pixelated light source with an improved electromagnetic compatibility . At least one further obj ect of certain embodiments is to speci fy a method for operating a pixelated light source that gives rise to an improved electromagnetic compatibility .

According to at least one aspect , the pixelated light source comprises a plurality of independently controllable light emitters . For example , the pixelated light source is part of a headlamp, a spotlight , a display, a video wall , or a proj ection system . For example the pixelated light source is used as an automotive headlight or for a dynamic background illumination of a display . In the following, features of a single light emitter are speci fied . In particular, one or more of these features apply to a maj ority of the plurality of light emitters , or to all of the plurality of light emitters .

For example , the light emitter converts an electrical current into electromagnetic radiation during operation . In particular, the light emitter emits electromagnetic radiation in a spectral range between infrared and ultraviolet light during operation . For example , the light emitter emits electromagnetic radiation in a visible spectral range during operation .

For example , the light emitter emits a maj ority of the electromagnetic radiation within an angular emission cone . Here and in the following, a main axis of the angular emission cone is denoted as an emission direction of the light emitter . For example , the light emitter has a Lambertian directional characteristic . For example , the light emitter comprises one or more optical elements , such as a lens . In particular, the optical element is configured for reducing an opening angle of the angular emission cone of the light emitter, and/or for shaping a directional characteristic of the light emitter .

For example , the pixelated light source further comprises one or more optical elements , such as one or more lenses , for shaping a directional characteristic of the pixelated light source . In particular, the one or more optical elements shape the collective electromagnetic radiation emitted by groups of light emitters , or by all light emitters , for example .

For example , an intensity or luminosity of each of the plurality of light emitters can be adj usted independently . In particular, at least two or all of the plurality of light emitters are provided with an independent or individual electrical current during operation of the pixelated light source . It is also possible that two or more light emitters are driven with the same or an identical electrical current .

For example , the plurality of light emitters are arranged in the form of a one-dimensional array or of a two-dimensional array . For example , each light emitter forms a pixel of the pixelated light source . In particular, at least two or all of the plurality of light emitters have the same emission direction . The emission directions of two or more light emitters can also deviate from each other . For example , the emission directions of two or more light emitters deviate by at most 120 ° .

According to at least one further aspect , the pixelated light source comprises an integrated circuit that provides a plurality of pulse width modulated electrical currents to the plurality of light emitters . For example , the integrated circuit is a field programmable gate array ( short : FPGA) , or an application speci fic integrated circuit ( short : AS IC ) . In particular, the integrated circuit is electrically connected to each of the plurality of light emitters and provides the plurality of pulse width modulated electrical currents for operating each light emitter independently . For example , the integrated circuit provides an individual pulse width modulated electrical current for each light emitter . It is also possible that two or more light emitters are provided with the same pulse width modulated electrical current or with identical pulse width modulated electrical currents .

Here and in the following the term "pulse width modulated electrical current" refers to an electrical current that is modulated periodically as function of time . In particular, during one time period, the pulse width modulated electrical current is switched two or more times between two di f ferent current values . For example , the two current values correspond to a vanishing electrical current and to a maximal electrical operating current of one light emitter . For example , the electrical current is switched on and of f at least once within one time period . In other words , one time period of the pulse width modulated electrical current comprises at least one current pulse . In particular, the pulse width modulated electrical current comprises a periodic sequence of current pulses , where one time period comprises at least one current pulse . For example , the time period is at most 10 milliseconds , preferably at most 5 milliseconds , such that no flickering is perceptible to the human eye .

A duration of one current pulse corresponds to a time interval between subsequent instances where the electrical current is switched on and of f , respectively . For example , a "duty cycle" of the pulse width modulated electrical current refers to a ratio between a time interval during which the electrical current is switched on and the time period of the pulse width modulated electrical current . In other words , the duty cycle corresponds to the sum of the durations of all current pulses within one time period relative to a duration of the time period . For example , a duty cycle of 100% corresponds to an electrical current that is constantly "on" as function of time , whereas a duty cycle of 60% corresponds to an electrical current that is "on" during 60% of the time period and "of f" during the remaining 40% of the time period .

For example , the integrated circuit comprises at least one pulse width modulator or a plurality of pulse width modulators . In particular, the integrated circuit comprises a separate pulse width modulator for each light emitter, respectively . By changing the duty cycle of the pulse width modulated electrical current , a time averaged luminosity of the corresponding light emitter can be adj usted .

According to at least one further aspect of the pixelated light source , current pulses within di f ferent pulse width modulated electrical currents that are provided by the integrated circuit are phase shi fted with respect to each other according to a deterministic or pseudo-random pattern . For example , current pulses of at least two di f ferent pulse width modulated electrical currents are phase shi fted with respect to each other according to a deterministic or pseudorandom pattern . For example , current pulses of all pulse width modulated electrical currents are phase shi fted with respect to each other according to a deterministic or pseudorandom pattern .

Here and in the following, the phase shi ft between two current pulses is proportional to a time di f ference between starting times and/or ending times of the respective current pulses . For example , the starting time corresponds to an instance in time , where the pulse width modulated electrical current is switched on within a given time period . For example , the ending time corresponds to an instance in time , where the pulse width modulated electrical current is switched of f within a given time period . In particular, the starting time and/or the ending time is measured from the beginning of the respective time period . For example , the starting time and the ending time is the same for each of a plurality of subsequent time periods , or for each time period . In particular, the time period is the same for each of the plurality of pulse width modulated electrical currents .

In particular, starting times and/or ending times of current pulses that are applied to di f ferent light emitters di f fer from each other . For example , within the time period, the starting time and/or ending time of at least one current pulse di f fers between at least two or between all of the plurality of pulse width modulated electrical currents .

For example , the starting times and/or the ending times are determined according to a deterministic pattern . For example , for a given number of light emitters operated with corresponding pulse width modulated electrical currents with given duty cycles , the starting times of the current pulses are chosen such that the current pulses overlap in time as little as possible . For example , the starting times of current pulses corresponding to di f ferent pulse width modulated electrical currents are chosen such that these current pulses are strung together in time without gaps between them, modulo the time period . In other words , i f the starting time or the ending time of one of the current pulses that are strung together in time is larger than the time period, the time period or an integer multiple of the time period is subtracted from the starting time , such that the starting time and the ending time lie within the time period of the pulse width modulated electrical current .

For example , the deterministic pattern looks like a random pattern, i f details on the construction of the deterministic pattern are not known . Accordingly, the deterministic pattern may appear like a random or pseudo-random pattern .

For example , the starting times for the current pulses corresponding to the plurality of pulse width modulated electrical currents are drawn from a random distribution . In particular, the starting times are statistically independent . For example , the random distribution has the same or a constant probability for each starting time within the time period . Alternatively or in addition, the starting times of the current pulses corresponding to the plurality of pulse width modulated electrical currents are random, but statistically dependent . For example , the starting times are randomly drawn under an additional condition, whereby a time di f ference between starting times of di f ferent current pulses is larger than a threshold . The starting times can be provided by a random number generator or a pseudo-random number generator, for example .

For example , the integrated circuit can have limited computing resources and/or limited memory resources . Accordingly, the deterministic or pseudo-random pattern can be implemented such that it requires low computational resources and/or low memory resources . For example , the deterministic or random pattern can be generated by or stored on an FPGA or an AS IC .

According to an embodiment , the pixelated light source comprises :

- the plurality of independently controllable light emitters , and

- the integrated circuit that provides the plurality of pulse width modulated electrical currents to the plurality of light emitters , wherein

- current pulses within di f ferent pulse width modulated electrical currents that are provided by the integrated circuit are phase shi fted with respect to each other according to a deterministic or pseudo-random pattern .

The pixelated light source described herein is based on the idea to reduce fluctuations of an electrical operating current of the pixelated light source comprising a plurality of light emitters that are driven with pulse width modulated electrical currents .

For example , i f hundred light emitters are driven with the same pulse width modulated electrical current , the corresponding current pulses for the di f ferent light emitters overlap in time , thereby giving rise to large electrical current variations . In particular, the electrical operating current of the pixelated light source j umps from zero to one hundred times the maximal operating current of one light emitter at least once per time period of the pulse width modulated electrical current , for example . Such large and/or fast electrical current variations would set high demands for an electrical power supply of the pixelated light source and would increase a complexity of the power source in order to comply with electromagnetic compatibility ( short : EMC ) regulations .

By providing phase shi fted current pulses to the plurality of light emitters as described above , a peak electrical operating current of the pixelated light source can be advantageously reduced, for example . Moreover, large and/or fast variations of the electrical operating current of the pixelated light source as a function of time can be advantageously reduced . Accordingly, requirements on the power supply for complying with EMC regulations can be lowered, for example .

According to at least one further aspect of the pixelated light source , each light emitter comprises at least one light emitting diode . For example , at least one light emitter or each light emitter comprises one , two , three or a plurality of light emitting diodes . For example , each light emitter comprises a group of light emitting diodes that form a pixel of the pixelated light source .

In particular, the light emitting diode comprises a semiconductor layer stack with an active layer for converting the electrical current into electromagnetic radiation . For example , the active layer comprises a pn-j unction . For example , the light emitting diode emits white light during operation . In particular, the light emitting diode comprises a wavelength conversion material or a phosphor for converting the wavelength of at least a part of the electromagnetic radiation generated in the active layer .

Alternatively or in addition, at least one light emitter comprises one or more laser diodes . For example , the laser diode comprises a semiconductor layer stack as an active laser medium, wherein the semiconductor layer stack is arranged in an optical resonator . In particular, the laser diode emits coherent electromagnetic radiation during operation . For example , compared to electromagnetic radiation generated by a light emitting diode via spontaneous emission, the coherent electromagnetic radiation has a larger coherence length, a smaller spectral bandwidth and/or a higher degree of polari zation .

According to at least one further aspect , the pixelated light source comprises at least 100 light emitters , or at least 1000 light emitters . Each light emitter forms a pixel of the pixelated light source , for example .

According to at least one further aspect of the pixelated light source , the deterministic or pseudo-random pattern is configured to reduce or minimi ze a maximal electrical peak current consumption of the pixelated light source . In particular, the deterministic or pseudo-random pattern is configured to reduce or minimi ze a maximal electrical current consumption of the pixelated light source , i f at least some of the light emitters are operated with a duty cycle of less than 100% . For example , the deterministic or pseudo-random pattern is configured such that not all light emitters are switched on at the same time during the time period of the pulse width modulated electrical current , i f the light emitters are operated at a duty cycle of less than 100% .

Here and in the following, the term " same time" refers to one or more times that are equal within a time resolution of the pulse width modulator . For example , the pulse with modulator has a time resolution of N bits and thus can resolve a minimal time step that is equal to T/N, where T is the time period of the pulse width modulated electrical current . In particular, two times are equal , i f their time di f ference is less than the minimal time step of the pulse width modulator .

According to at least one further aspect of the pixelated light source , the deterministic or pseudo-random pattern is configured to reduce changes of the electrical operating current of the pixelated light source as a function of time . In particular, the deterministic or pseudo-random pattern is configured to reduce abrupt changes of the electrical operating current . In other words , the deterministic or pseudo-random pattern is configured to reduce a time derivative of the electrical operating current . For example , the deterministic or pseudo-random pattern avoids that multiple light emitters are switched on or of f at the same time during a period of the pulse width modulated electrical current . According to at least one further aspect of the pixelated light source , a duty cycle of at least two of the plurality of pulse width modulated electrical currents is di f ferent . In other words , at least two of the plurality of light emitters emit electromagnetic radiation with di f ferent time averaged luminosities . It is also possible that the duty cycle of all pulse width modulated electrical currents is the same .

According to at least one further aspect of the pixelated light source , the current pulses within di f ferent pulse width modulated electrical currents that are provided by the integrated circuit are chopped and distributed over time . In particular, a chopped current pulse comprises two or more sub-pulses with di f ferent starting times , such that subpulses do not overlap . For example , the starting times of the sub-pulses of di f ferent pulse width modulated electrical currents are distributed over time , such that variations of the electrical operating current of the pixelated light source are reduced .

According to at least one further aspect of the pixelated light source , the integrated circuit comprises a memory and a table with predetermined phase shi fts according to the deterministic or pseudo-random pattern is stored in the memory . For example , the table comprises a list of phase shi fts or starting times for the current pulses corresponding to the plurality of pulse width modulated electrical currents . In particular, the phase shi fts or starting times depend on the duty cycles of the plurality of pulse width modulated electrical current . According to at least one further aspect of the pixelated light source , the integrated circuit comprises a random number generator or a pseudo-random number generator for generating phase shi fts and/or chopped pulses according to the pseudo-random pattern .

Further a method for operating a pixelated light source is speci fied herein . In particular, the method can be used to operate the pixelated light source described above . All features of the pixelated light source are also disclosed for the method for operating a pixelated light source , and vice versa .

According to at least one aspect of the method for operating a pixelated light source comprising a plurality of independently controllable light emitters , each light emitter is operated with a corresponding pulse width modulated electrical current .

According to at least one further aspect of the method, current pulses within di f ferent pulse width modulated electrical currents are phase shi fted with respect to each other and/or chopped as a function of time according to a deterministic or pseudo-random pattern .

According to an embodiment of the method for operating a pixelated light source comprising a plurality of independently controllable light emitters , each light emitter is operated with a corresponding pulse width modulated electrical current , and current pulses within di f ferent pulse width modulated electrical currents are phase shi fted with respect to each other and/or chopped as a function of time according to a deterministic or pseudo-random pattern . According to at least one further aspect of the method, the deterministic or pseudo-random pattern is encoded in a sequence of di f ferent starting times of the respective current pulses of the di f ferent pulse width modulated electrical currents . In particular, the phase shi fts are proportional to time di f ferences between the di f ferent starting times . For example , the deterministic or pseudorandom pattern comprises a list starting times that depend on given duty cycles of the plurality of pulse width modulated electrical currents . For example a time averaged luminosity of each of the plurality of light emitters is adj usted by setting the duty cycle of the respective pulse width modulated electrical current to a corresponding value .

In particular, the starting times are determined deterministically, or are drawn from a random or pseud-random distribution . For example , the starting times are determined deterministically, such that fluctuations of the electrical operating current of the pixelated light source due to the plurality of pulse width modulated electrical currents are reduced or minimi zed . In particular, the fluctuations of the total electrical operating current are reduced compared to a case , where the starting times of the current pulses corresponding to the plurality of pulse width modulated electrical currents are equal . For example , the starting times of di f ferent current pulses are chosen such that they do not coincide .

Alternatively or in addition, the starting times can be chosen such that a time spacing between starting times is as large as possible under the condition that each of the starting times is smaller than the time period of the plurality of pulse width modulated electrical currents and/or under the condition that an ending time of each current pulse is smaller than or equal to the time period . Here , the ending time refers to a time that is equal to the sum of the starting time and the duration of the current pulse .

According to at least one further aspect of the method, the time period of at least one pulse width modulated electrical current comprises two or more current pulses . In particular, the duty cycle is proportional to the sum of the two or more current pulses in this case . For example , the time period of at least one pulse width modulated electrical current comprises a burst of current pulses . It is also possible that the at least one pulse width modulated electrical current comprises only one current pulse , in particular at very low or at very high duty cycles , for example i f the duty cycle is below 10% or above 90% .

According to at least one further aspect of the method, the deterministic or pseudo-random pattern is encoded in a sequence of di f ferent time intervals between the two or more current pulses within one time period, such that the time intervals di f fer between di f ferent pulse width modulated electrical currents .

For example , a first pulse width modulated electrical current comprises two or more current pulses with time intervals between the current pulses according to a first sequence , whereas a second pulse width modulated electrical current comprises two or more current pulses with time intervals between the current pulses according to a second sequence . In particular, a first light emitter is driven with the first pulse width modulated electrical current and a second light emitter is driven with the second pulse width modulated electrical current , and the first sequence and the second sequence are di f ferent . For example , the first and second sequences are chosen deterministically depending on the given duty cycles of the first and second pulse width modulated electrical currents , such that current pulses overlap as little as possible between the first and second pulse width modulated electrical currents .

According to at least one further aspect of the method, the time period of at least one pulse width modulated electrical current is split into an integer number of N subsequent time blocks . For example , the time periods of all pulse width modulated electrical currents are split into an integer number of N subsequent time blocks . In particular, the time blocks do not overlap and are adj acent to each other without time gaps between them . For example , N is equal to 4 , 8 , or 16 . In particular N is at most equal to the number of light emitters . Preferably, N is smaller than the number of light emitters . For example , the number of light emitters is larger than N by a factor of at least 10 or 100 .

According to at least one further aspect of the method, the pulse width modulated electrical current is switched on or of f within the N time blocks according to an N-bit sequence . In particular, the N-bit sequence is a sequence of N bits , wherein each bit takes either a value " 1" or " 0" . For example , the pulse width modulated electrical current is switched on during a time block, i f the corresponding bit in the N-bit sequence takes the value " 1" , whereas the pulse width modulated electrical current is switched of f during a time block, i f the corresponding bit in the N-bit sequence takes the value " 0" , respectively . For example , each of the plurality of pulse width modulated electrical currents has an associated N-bit sequence . In particular, the N-bit sequences are chosen according to the deterministic or pseudo-random pattern . In other words , an N- bit sequence is assigned to the respective pulse width modulated electrical current deterministically or in a random or pseudo-random manner . For example , the N-bit sequences are stored in a memory of the integrated circuit . For example , the N-bit sequence is generated by a random or pseudo-random number generator . Preferably, the N-bit sequence di f fers between at least some of the pulse width modulated electrical currents , such that at least some of the current pulses are phase shi fted with respect to each other .

According to at least one further aspect of the method, a duty cycle of the pulse width modulated electrical current is proportional to a sum of digits of the corresponding N-bit sequence . In other words , the duty cycle is proportional to the number of bits of the N-bit sequence that take the value " 1" . In particular, the N-bit sequence depends on the duty cycle that is set for the corresponding light emitter . For example , the N-bit sequences for the plurality of pulse width modulated electrical currents are determined deterministically or in a random or pseudo-random manner, depending on the desired duty cycle .

According to at least one further aspect of the method, the deterministic or pseudo-random pattern is encoded as a set of N-bit sequences , such that one N-bit sequence is associated to each of the plurality of pulse width modulated electrical currents . In particular, one N-bit sequence is associated to each light emitter . For example , the set of N-bit sequences is deterministic or pseudo-random . In particular, di f ferent N-bit sequences correspond to di f ferent sequences of current pulses within one time period, such that at least some of the current pulses are phase shi fted between di f ferent pulse width modulated electrical currents . At least one given N-bit sequence out of the set of N-bit sequences can also be associated to a group of light emitters that are driven with identical pulse width modulated electrical currents .

Further advantageous embodiments and further embodiments of the pixelated light source and the method for operating a pixelated light source become apparent from the following exemplary embodiments described in connection with the figures .

Figure 1 shows a schematic cross section of a pixelated light source according to an exemplary embodiment .

Figure 2 shows schematic pulse width modulated electrical currents according an exemplary embodiment of the method for operating a pixelated light source .

Figures 3 and 4 show schematic pulse width modulated electrical currents according further exemplary embodiments of the method for operating a pixelated light source .

Figures 5 and 6 show electric operating currents of a pixelated light source according to di f ferent examples .

Figures 7 and 8 show electric operating currents of a pixelated light source according to di f ferent exemplary embodiments of a method for operating a pixelated light source . Elements that are identical , similar, or have the same ef fect , are denoted by the same reference signs in the figures . The figures and the proportions of the elements shown in the figures are not to be regarded as true to scale . Rather, individual elements , may be shown exaggeratedly large for better representability and/or better understanding .

The pixelated light source 1 according to the exemplary embodiment in Figure 1 comprises a plurality of light emitters 2 and an integrated circuit 3 that are arranged on a common carrier 4 . Alternatively, the integrated circuit 3 can be arranged separately from the carrier 4 . The pixelated light source 1 comprises at least one hundred light emitters 2 .

The light emitters 2 are arranged in the form of a regular one- or two dimensional array, such that each light emitter 2 forms an individually controllable pixel of the pixelated light source 1 . Each of the plurality of light emitters 2 is a light emitting diode that emits white light during operation . The integrated circuit 3 provides a plurality of individual pulse width modulated electrical currents I for driving the plurality of light emitters 2 . In particular, each light emitter 2 is driven by an associated, individual pulse width modulated electrical current I during operation of the pixelated light source 1 . It is also possible that at least one of the pulse width modulated electrical currents I is provided to a group of light emitters 2 .

In particular, a time averaged luminosity of each light emitter 2 can be adj usted by setting the duty cycle of the corresponding pulse width modulated electrical current I that are provided by the integrated circuit 3 to a speci fic value . The integrated circuit 3 is an FPGA or an AS IC . Moreover, the integrated circuit 3 comprises current ampli fiers for driving the light emitters 2 . In particular, each light emitter 2 has an associated current ampli fier . The current ampli fiers can also be formed and/or arranged separately from the integrated circuit 3 .

The pulse width modulated electrical currents I provided by the integrated circuit 3 comprise current pulses P that are phase shi fted between di f ferent pulse width modulated electrical currents I . In other words , starting times ts of current pulses P within each time period TO di f fer between di f ferent pulse width modulated electrical currents I ( c . f . Figure 2 ) . The phase shi fts between the current pulses follow a deterministic or pseudo-random pattern . Speci fically, the starting times ts of the current pulses P are chosen deterministically such that an overlap between current pulses P as a function of time t is as small as possible . Accordingly, a maximal electrical operating current of the pixelated light source 1 is minimi zed and/or fluctuations of the electrical operating current of the pixelated light source 1 are reduced compared to a case where all current pulses P have the same starting time ts .

Alternatively, the current pulses P follow a random or pseudo-random pattern, wherein the starting times ts of the current pulses P are drawn from a random or pseudo-random probability distribution under the condition that the ending time te of each current pulse P is smaller than or equal to the time period TO . For example , the probability distribution has a constant probability for all starting times ts within the time period TO . In particular, a random or pseudo-random sampling of starting times ts may be advantageous for a pixelated light source comprising a large number of light emitters 2 , as the computational ef fort in determining starting times ts is reduced .

Figure 2 schematically shows two out of a plurality of pulse width modulated electrical currents I that are phase shi fted with respect to each other according to an exemplary embodiment of the method for operating a pixelated light source . The first pulse width modulated electrical current I is drawn as a solid line , whereas the second pulse width modulated electrical current I is drawn as a dashed line in Figure 2 .

The pulse width modulated electrical currents I are periodic in time t with a time period TO . In other words , a time profile of the electrical current I is equal or approximately equal in each successive time period TO during operation of the pixelated light source 1 , as long as the duty cycle is not changed during operation of the pixelated light source 1 .

Each of the pulse width modulated electrical currents I comprises one current pulse P per time period TO . It is also possible that at least one of the pulse width modulated electrical currents I comprises two or more current pulses per time period TO . At the starting time ts of a current pulse , the electrical current I is switched from zero to a maximal operating current of the corresponding light emitter 2 . Subsequently, the electrical current I is maintained during a given time duration of the current pulse P, before the electrical current I is switched of f again . A ratio between the duration of the current pulse P and the time period TO determines the duty cycle of the pulse with modulated electrical current I .

The current pulses P of the two pulse width modulated electrical currents I are phase shi fted with respect to each other . In other words , starting times ts of the respective current pulses P are di f ferent from each other . The starting times ts are chosen such that the current pulses P do not overlap in time t . Accordingly, a maximal electrical operating current of the pixelated light source 1 is minimi zed . Moreover, the starting times ts are chosen such that the current pulses P end before the time period TO .

Figure 3 shows a schematic pulse width modulated electrical current I according to a further exemplary embodiment of the method for operating a pixelated light source 1 . In particular, Figure 3 shows one of a plurality of pulse width modulated electrical currents I that are provided by the integrated circuit 3 . Compared to the exemplary embodiment described in connection with Figure 2 , the pulse width modulated electrical current I in Figure 3 comprises three current pulses P per time period TO , although other numbers of current pulses are possible as well .

In the example shown in Figure 3 each of the three current pulses P has the same duration . It is also possible that the current pulses P have di f ferent durations , however . Moreover, time intervals tint between subsequent current pulses P of the pulse width modulated electrical current I are chosen such that current pulses P between di f ferent pulse width modulated electrical currents I overlap as little as possible and/or such that an electrical operating current of the pixelated light source has small variations as a function of time . In particular, the time interval tint is not constant and can vary between di f ferent current pulses P of the same pulse width modulated electrical current I .

Phase shi fts between current pulses P of di f ferent pulse width modulated electrical currents I (not shown in Figure 3 ) are chosen according to a deterministic or pseudo-random pattern . In this example , this deterministic or pseudo-random pattern is encoded in a sequence of di f ferent time intervals tint between the three current pulses within the time period TO , such that the time intervals tint di f fer between pairs of di f ferent pulse width modulated electrical currents I . For example , durations of current pulses P and the time intervals tint are set deterministically, depending on the number of light emitters 2 and the given duty cycle of each light emitter 2 . It is also possible that the time intervals tint are drawn form a random or pseudo-random probability distribution .

Figure 4 shows a schematic pulse width modulated electrical current I according to a further exemplary embodiment of the method for operating a pixelated light source 1 . In particular, Figure 4 shows one of a plurality of pulse width modulated electrical currents I that are provided by the integrated circuit 3 . The time period TO is split into a number of N=8 subsequent time blocks tb, such that the time blocks tb do not overlap and such that there are not time gaps between subsequent time blocks tb . It is also possible that the number of time blocks N is a di f ferent integer number N . Preferably, N is smaller than the number of light emitters 2 . For example , the number of light emitters 2 is larger than the number of time blocks tb by at least a factor of 10 , or at least a factor of 100 . Each of the plurality of pulse width modulated electrical currents I has an N-bit sequence S associated to it , such that each bit of the N-bit sequence S corresponds to a time block tb, respectively . In particular, the N-bit sequence S is a sequence of digits that are either " 0" or " 1" . The pulse width modulated electrical current I is switched on in a given time block tb, i f the corresponding bit in the N-bit sequence is " 1" , and the pulse width modulated electrical current I is switched of f in a given time block tb, i f the corresponding bit in the N-bit sequence is " 0" . In other words , the N-bit sequence determines the sequence of current pulses within a time period TO . In particular, the pulse width modulated electrical current I comprises a current pulse P in the time block tb, i f the corresponding bit of the N-bit sequence S is " 1" .

The number N of time blocks tb can be chosen according to a desired resolution of the duty cycle . In particular, for a number of N time blocks tb, the duty cycle can be set in steps of 1 /N between 0 and 1 .

At least two pulse width modulated electrical currents I have di f ferent N-bit sequences S associated to them, such that at least two current pulses P are phase shi fted between the two pulse width modulated electrical currents I . I f possible , each of the plurality of pulse width modulated electrical currents I has an individual N-bit sequence associated to it . The N-bit sequences S can be associated to the plurality of pulse width modulated electrical currents I deterministically, depending on the number of light emitters 2 and the given duty cycle for each light emitter 2 . For example , the N-bit sequences are chosen such that the current pulses P of the plurality of pulse width modulated electrical currents I overlap as little as possible . It is also possible to assign the N-bit sequences randomly or pseudo-randomly to the plurality of pulse width modulated electrical currents I , under the condition that the N-bit sequences S correspond to the given duty cycles .

For example , the pixelated light source comprises 70 light emitters 2 , each driven with a corresponding pulse width modulated electrical current I at a duty cycle of 50% . Moreover, the time period TO of the pulse width modulated electrical currents I is split into N=8 time blocks tb . Accordingly, by choosing 4 out of 8 time blocks there are 70 combinatorial possibilities of choosing di f ferent 8-bit sequences S giving rise to a duty cycle of 50% . Therefore , a di f ferent 8-bit sequence S can be assigned to each of the 70 pulse width modulated electrical currents I .

By modulating each of the 70 pulse width modulated electrical currents I according to a di f ferent 8-bit sequence out of the set of 70 di f ferent 8-bit sequences within each time period TO , the current pulses P overlap as little as possible between di f ferent pulse width modulated electrical currents I . Accordingly, the maximum electrical operating current of the pixelated light source 1 as well as current fluctuations of the electrical operating current are minimi zed .

For other duty cycles that are di f ferent from 50% , the number of combinatorial possibilities of 8-bit sequences S is smaller than 70 . Accordingly, some of the plurality of pulse width modulated electrical currents I have the same 8-bit sequence associated to them . Nevertheless , by associating all possible 8-bit sequences for a given duty cycle to the plurality of pulse width modulated electrical currents I , the maximum electrical operating current of the pixelated light source 1 as well as its current fluctuations can be reduced .

Figure 5 shows a ratio between an electrical operating current I and a maximal electrical operating current Imax of a pixelated light source 1 according to an example . In particular, the plurality of light emitters 2 are operated with corresponding pulse width modulate electrical currents I , whereby the duty cycles of at least some of the plurality of pulse width modulate electrical currents I are di f ferent . Even though starting times ts of current pulses P corresponding to di f ferent duty cycles are di f ferent , the ending times te of all current pulses is equal and coincides with the end of the time period TO . In other words , all current pulses are switched of f at the end of the time period TO . Consequently the maximum electrical operating current I of the pixelated light source 1 is particularly large at the end of the time period TO , where all current pulses P overlap . Moreover, the current fluctuations of the electrical operating current I are large , as all current pulses P are switched of f at the same time t at the end of the time period TO .

Figure 6 shows an electrical operating current I of a pixelated light source 1 according to a further example . In contrast to the electrical operating current I described in connection with Figure 5 , ending times te of current pulses P with di f ferent durations do not coincide . However, all current pulses P are centered at the middle of the time period TO . In other words , all current pulses P overlap at least at a time t corresponding to hal f of the time period TO . Accordingly, the maximum electrical operating current I is the same as in the example of Figure 5 , but the current fluctuations are smaller, because not all current pulses P are switched on and/or of f at the same time t .

Figure 7 shows an electrical operating current I of a pixelated light source 1 according to an exemplary embodiment , whereby the plurality of light emitters 2 are arranged in 10 groups and each group is driven with a corresponding pulse width modulated electrical current I . Each of the 10 di f ferent pulse width modulated electrical current I comprises a single current pulse P that has a constant phase shi ft with respect to the current pulses of the other pulse width modulated electrical currents I . Accordingly, starting times ts and/or ending times te of the current pulses P are di f ferent from each other, and not all current pulses P overlap . Compared to the examples described in connection with Figures 5 and 6 , the maximum electrical operating current I is therefore reduced .

Figure 8 shows an electrical operating current I of a pixelated light source 1 according to an exemplary embodiment , whereby the light emitters 2 of the pixelated light source 1 are driven according to the method described in connection with Figure 4 . Compared to the exemplary embodiment described in connection with Figure 7 , the electrical operating current I is almost constant . Moreover, both, the amplitude of the electrical operating current I of the pixelated light source 1 as well as fluctuations of the electrical operating current I are strongly reduced or minimi zed . This patent application claims the priority of German patent application DE 102023108841 . 6 , the disclosure content of which is hereby incorporated by reference . The invention is not restricted to the exemplary embodiments by the description on the basis of said exemplary embodiments . Rather, the invention encompasses any new feature and also any combination of features , which in particular comprises any combination of features in the patent claims and any combination of features in the exemplary embodiments , even i f this feature or this combination itsel f is not explicitly speci fied in the patent claims or exemplary embodiments .

References

1 pixelated light source

2 light emitter 3 integrated circuit

4 carrier

I electrical current

P current pulse t time ts starting time te ending time tint time interval tb time block

TO time period S N-bit sequence

Claims

1. A pixelated light source (1) , comprising:

- a plurality of independently controllable light emitters ( 2 ) , and

- an integrated circuit (3) providing a plurality of pulse width modulated electrical currents (I) to the plurality of light emitters (2) , wherein

- current pulses (P) within different pulse width modulated electrical currents (I) that are provided by the integrated circuit (3) are phase shifted with respect to each other according to a deterministic or pseudo-random pattern, and

- a time period (TO) of at least one pulse width modulated electrical current (I) comprises two or more current pulses (P) •

2. The pixelated light source (1) according to the previous claim, wherein each light emitter (2) comprises at least one light emitting diode .

3. The pixelated light source (1) according to any of the previous claims, wherein the pixelated light source comprises at least 100 light emitters ( 2 ) .

4. The pixelated light source (1) according to any of the previous claims, wherein the deterministic or pseudo-random pattern is configured to reduce changes of an electrical operating current of the pixelated light source (1) as a function of time (t) .

5. The pixelated light source (1) according to any of the previous claims, wherein the deterministic or pseudo-random pattern is configured to reduce or minimize a maximal electrical peak current consumption of the pixelated light source (1) .

6. The pixelated light source according to any of the previous claims, wherein the current pulses (P) within different pulse width modulated electrical currents (I) that are provided by the integrated circuit (3) are chopped and distributed over time.

7. The pixelated light source (1) according to any of the previous claims, wherein

- the integrated circuit (3) comprises a memory, and

- a table with predetermined phase shifts according to the deterministic or pseudo-random pattern is stored in the memory .

8. The pixelated light source (1) according to any of the previous claims, wherein the integrated circuit (3) comprises a pseudo-random number generator for generating phase shifts and/or chopped current pulses according to the pseudo-random pattern.

9. A method for operating a pixelated light source (1) comprising a plurality of independently controllable light emitters (2) , wherein

- each light emitter (2) is operated with a corresponding pulse width modulated electrical current (I) , and

- current pulses (P) within different pulse width modulated electrical currents (I) are phase shifted with respect to each other and/or chopped as a function of time according to a deterministic or pseudo-random pattern, and

10. The method according to claim 9, wherein the deterministic or pseudo-random pattern is encoded in a sequence of different starting times (ts) of the respective current pulses (P) of the different pulse width modulated electrical currents (I) .

11. The method according to claim 9 or 10, wherein the deterministic or pseudo-random pattern is encoded in a sequence of different time intervals (tint) between the two or more current pulses (P) within one time period (TO) , such that the time intervals (tint) differ between different pulse width modulated electrical currents (I) .

12. The method according to any of claims 9 to 11, wherein

- a time period (TO) of at least one pulse width modulated electrical current (I) is split into an integer number of N subsequent time blocks (tb) , and

- the pulse width modulated electrical current (I) is switched on or off within the N time blocks (tb) according to an N-bit sequence (S) .

13. The method according to claim 12, wherein a duty cycle of the pulse width modulated electrical current (I) is proportional to a sum of digits of the corresponding N-bit sequence (S) .

14. The method according to claim 13, wherein the deterministic or pseudo-random pattern is encoded as set of N-bit sequences (S) , such that one N-bit sequence is associated to each of the plurality of pulse width modulated electrical currents (I) .