BE1025889B1 - Supply voltage calibration for lighting systems - Google Patents

Abstract

A method for calibrating a power supply voltage for lighting systems comprising a plurality of LED strips includes adjusting (301) the power supply voltage of LED strips (and control units connected to cluster clusters) to a first value for which all LEDs in the A plurality of LED strips are expected to function, measuring (303) a voltage in a connection between each control unit and its connected LED strips, and comparing (304) the measured voltage with a preset voltage for each strip. If the measured voltage is higher than a predefined error voltage over the preset voltage, or lower than the preset voltage, a warning signal is generated (305) in the control unit to inform a main unit that the supply voltage is high or low . The first voltage value is adjusted based on the warning signal (306). At least the settings for obtaining the highest value of the adjusted supply voltage are stored (307, 317).

Description

Supply voltage calibration for lighting systems

FIELD OF THE INVENTION

The present invention relates to the field of driving electronic systems. More specifically, it relates to calibration of supply voltage in electronic car systems such as lighting systems.

BACKGROUND OF THE INVENTION

A common requirement of lighting systems, for example for signaling, is lighting stability. This requirement is particularly valid in LED lighting systems, which are currently included in a number of applications due to their low power consumption. They are often found in vehicle lighting and signaling systems.

LED lighting systems usually include one or more LEDs that are connected in series and form an LED strip. In certain applications, LEDs can also be connected in parallel. Light sources containing LEDs usually exhibit the problem of changing their intensity due to degradation, e.g., due to thermal degradation. Furthermore, the light output of such an LED strip is current dependent. To ensure a specified light output for such an LED strip, a specific current is required. The current can be regulated to ensure a specific light output. Aging effects and thermal degradation can be excluded. The voltage across the LED strip may vary during current regulation. In order to ensure a current control, for example by a current source or a switching element, a minimum voltage across that current source or the switching element is required. Also, the voltage across the LED strip must not fall below a minimum value to ensure a specific light output (brightness). If the voltage across the power source or the switching element is too high, there will be a high power dissipation across the power source or the switching element, which can lead to damage, a reduction in the lifetime due to overheating, degradation effects, etc. These problems, alone or combined, can develop into dangerous situations. It is therefore important to use a power source for the LED strip and its drive elements, such as, for example, a power source or a switching element, which is high enough for current control, but low enough for optimum power dissipation.

In the specific case of automotive applications, different types of lighting systems exist. These can be, for example, forward lighting or lighting systems (headlamps, auxiliary lamps such as fog lamps), signaling

BE2018 / 5514 eye-catching systems (daytime running lights, reversing lights and parking lights, tail or rear lights, direction indicators, etc.), interior lighting, license plate lighting, etc. These systems must be stable and efficient, but they are rarely used almost all at the same time. For example, in automotive applications, direction indicators are only used when needed, regardless of the use of, for example, headlights. Moreover, different lighting systems do not normally match, for example because different types of LEDs and / or a different number of them are required. Despite the fact that systems usually do not match, vehicles usually contain a single power source for all of their electrical devices, including lighting systems (usually a battery). To prevent the lighting conditions of a used system from being affected, individual control of each system is usually provided when a second system is activated. Systems can have stable lighting in this way, at the expense of higher complexity. For example, in order to obtain an optimum supply voltage that covers the needs for all possible LED strips, eg in the rear lights, the power supply management system must be tailor-made for each LED model and / or architecture depending on the type of vehicle, and even from the brand. It may also be necessary to perform a calibration at the end of the line, depending on the model of the rear light, for example in the production line at the supplier of the power management system. This implies the use of different parts and devices for each different model, resulting in higher logistical efforts to process the differently configured main control units. Alternatively, calibration can be performed on the vehicle manufacturer's production line, thereby increasing costs and production time. However, long-term degradation cannot be taken into account in these systems, so there is room for improvement.

Summary of the invention

It is an object of embodiments of the present invention to provide a system for controlling one or more lighting systems with voltage calibration capabilities, in particular for automotive applications.

It is an advantage of embodiments of the present invention that they provide a calibration method for lighting systems, with high flexibility and simplicity, and which provides lighting stability for a wide range of applications, lighting systems and configurations.

BE2018 / 5514

In a first aspect, a method for calibrating a supply voltage for lighting systems comprising a plurality of LED strips of light-emitting diodes (LEDs) is described, the method comprising:

- setting the supply voltage to a first voltage value for which all LEDs in the plurality of LED strips are expected to function,

- providing the first voltage value to the plurality of LED strips and to control units connected to clusters of LED strips, wherein each cluster comprises at least one LED strip,

- measuring a voltage in a pin connection between each control unit and its respective connected LED strips, and comparing the measured voltage with a preset voltage for the respective strip. If the measured voltage is higher than a predefined error voltage over the preset voltage, respectively lower than the preset voltage, a warning signal can be generated in the corresponding control unit to warn a main control unit (MCU) that the supply voltage is high or low, respectively. ,

- on the basis of the warning signal, adjusting the first voltage value to an adjusted supply voltage by means of the main control unit, and

- storing at least the setting for obtaining the adjusted supply voltage for which a minimum supply voltage is obtained, the minimum supply voltage being the smallest supply voltage for which the measured voltage in each strip of a cluster is higher than the preset voltage for all strips of that cluster.

The setting of the supply voltage to a first voltage value further comprises setting the supply voltage to a first voltage value such that the measured voltage is either lower or higher than the required voltage for each strip of a cluster, and generating a warning signal further includes generating in the corresponding control unit of that cluster a warning signal upon detecting that the measured voltage is lower, or higher, respectively, than the required voltage for at least one strip of the cluster, to report to a main control unit that the supply voltage is low, or is high, respectively, and, upon detection that the measured voltage is lower than the required voltage, the supply voltage is increased until the measured voltage is higher than the required voltage.

BE2018 / 5514

It is an advantage of embodiments of the present invention that a control of a complex lighting system or complex lighting systems can be provided with a limited amount of control units and a single main control unit. It is a further advantage that calibration of voltage drop variations over the LED strips, depending on the use of systems, scheme of activation thereof and / or degradation can be obtained. In some embodiments, the settings can be stored in a memory. The settings may include, for example, the settings of a voltage converter for obtaining at least the highest supply voltage from all supply voltages that the clusters may need. Saving the settings may also include storing the (settings of a voltage converter to obtain the) highest adjusted supply voltage and the specific configuration, e.g., the specific clusters in use, which require such highest adjusted supply voltage. Saving the settings may also include saving the settings of a voltage converter to obtain any adjusted voltage required for each cluster. It is an advantage that at least the maximum supply voltage can be used, or a modified supply voltage optimized for a specific configuration, or the highest adjusted voltage from a pool of adjusted voltages per cluster, selected according to the specific cluster being used .

Some embodiments of the present invention may further include providing a signal indicating that calibration is complete when all control units detect a measured voltage that is higher than the preset voltage that deviates less than the predefined error voltage from the preset voltage for that strip.

It is an advantage of embodiments of the present invention that an operator can be sure that the calibration was successful.

Some embodiments of the present invention may further include the step of performing some or all of the steps of the method at predetermined time intervals.

It is an advantage of embodiments of the present invention that variations of illumination of the LED systems due to temperature changes, degradation, etc. can be regularly compensated.

BE2018 / 5514

In some embodiments of the present invention, the preset voltage can be defined per cluster and / or strip.

In further embodiments, the preset voltage can be varied according to the configuration of lighting of clusters and / or application.

It is an advantage of embodiments of the present invention that the preset voltage can be selected in accordance with the type of LED, number of LEDs in a strip and the required lighting, thus taking into account the granularity of the lighting system.

In some embodiments of the present invention, the predefined error voltage can be varied according to the configuration of lighting of clusters and / or application.

It is an advantage of embodiments of the present invention that the illumination obtained may be more robust against changes, undesired peaks or disturbances of the supply voltage and / or the external supply (e.g., battery).

In some embodiments of the present invention, the preset voltage and / or the predefined error voltage can be programmed.

Some embodiments of the present invention may further include storing the inverter setting to obtain the highest adjusted supply voltage value required by all clusters, and further including adjusting the supply voltage to the highest adjusted supply voltage value upon further activation.

It is an advantage of embodiments of the present invention that drive can be ensured for all LED strips, thereby reducing the chance of an LED strip being under-energized and producing less lighting. It is an advantage of embodiments of the present invention that a single VS can be used, thereby reducing the computing load and memory usage.

Alternative embodiments of the present invention may include storing each of the voltage converter settings to provide adjusted supply voltage values required by each cluster, and further including adjusting the supply voltage to the highest adjusted supply voltage value imposed by at least one of the active control units upon further activation of said control units, in order to achieve the preset voltage for driving at least each LED strip.

BE2018 / 5514

It is an advantage that the highest supply voltage can depend on the active clusters and can change during use, thereby providing optimum drive depending on the specific operation.

In a second aspect, the invention provides a system for driving a plurality of clusters that include at least one LED strip. The system may include a main control unit (MCU) that includes a voltage converter for providing an output power voltage and at least one interface for communication with a plurality of control units, at least one control unit for driving at least each LED cluster (i.e., a or more control units per cluster). Each control unit contains:

- at least one LED drive unit per LED strip in the cluster,

- a voltage reader for reading the voltage at a node between the control unit and each LED strip,

- a voltage comparator for comparing the measured voltage with a preset voltage for that strip,

- a signal generator for generating a first signal in the case that the measured voltage exceeds a predefined error voltage above the preset voltage, or a second signal in the case that the measured voltage does not reach the preset voltage,

- transmission means for transmitting at least all first or second generated signals to the MCU, the MCU further comprising means for adjusting the output supply voltage in accordance with the signals generated in each of the control units, and

- a processing unit for controlling the LED drive units, for obtaining the measured voltages from the voltage reader and comparing them with the preset voltages, and for generating warning signals.

It is an advantage of embodiments of the present invention that an MCU is provided for one or all of the LED strips, which may be external to the power source. It is an additional advantage that fewer control units than LED strips are needed if LED strips are clustered, for example one controller per LED cluster, for example, one controller for each rear light lighting system. It is a further advantage that this implementation can be applied to a wide range of vehicles and brands, for example, the present invention can provide a universal lighting system.

BE2018 / 5514

In some embodiments of the present invention, the control unit can be integrated into a single integrated circuit.

It is an advantage of embodiments of the present invention that a compact, modular controller can be obtained per lighting system.

In some embodiments of the present invention, the MCU further includes a configuration memory for storing a plurality of voltage converter settings for obtaining adjusted supply voltages as well as a cluster lighting configuration for which said value was obtained.

It is an advantage of embodiments of the present invention that the first supply voltage can be optimized in an earlier calibration, which possibly reduces the chances that further calibration is required.

In some embodiments of the present invention, a LIN secondary network is provided between the control units and the MCU, which is separate from a primary network for connecting the main control unit to a higher level system.

It is an advantage of embodiments of the present invention that isolation between the primary network and the secondary network is achieved, thereby reducing interference, for example, reducing cross-talk between the elements of the primary network and the lighting system.

In alternative embodiments, a CAN network is provided between the control units and the MCU, for providing direct connection to a higher level system.

It is an advantage of embodiments of the present invention that the communication network can be made simpler by connecting all elements to a single network, thereby improving, for example, problem diagnosis.

It is an advantage of embodiments of the present invention that a compact controller can be obtained.

Particular and preferred aspects of the invention are set out in the accompanying independent and dependent claims. Features of the dependent claims can be combined with features of the independent claims and with features of other dependent claims and not only as expressly set out in the claims.

BE2018 / 5514

These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment (s) described below.

Brief description of the drawings

FIG. 1 illustrates a first embodiment of a system according to an aspect of the present invention, comprising a secondary network between a main control unit and a plurality of control units.

FIG. 2 illustrates a further embodiment of a system according to an aspect of the present invention, comprising a unique network for communication between a higher level system, the main control unit, and a plurality of control units.

FIG. 3 illustrates a flow chart and method according to embodiments of the present invention, including optional steps.

FIG. 4 is a flow chart of a method for calibrating according to embodiments of the present invention, applicable to single clusters or to many clusters simultaneously, with a first low supply voltage.

FIG. 5 is a flow chart of a method for calibrating according to embodiments of the present invention, applicable to single clusters or to many clusters simultaneously, with a high supply voltage.

The drawings are only schematic and are not limitative. In the drawings, the dimensions of some elements may be exaggerated and not drawn to scale for illustrative purposes.

Any reference characters in the claims should not be considered as limiting the scope.

On the different figures, the same reference numerals refer to the same or analogous elements.

Detailed description of exemplary embodiments

The present invention will be described with reference to particular embodiments and with reference to certain drawings, but is not limited thereby, but only by the claims. The described drawings are only schematic and are not limitative. In the drawings, the dimensions of some elements may be exaggerated and not drawn to scale for illustrative purposes. The

BE2018 / 5514 dimensions and relative dimensions do not correspond to actual reductions for the practice of the invention.

The terms first, second and the like in the description and in the claims are used to distinguish between similar elements and not necessarily for describing a sequence, whether temporary, spatial, in the arrangement or in any other way. It will be understood that the terms so used are interchangeable under suitable conditions and that the embodiments of the invention described in this patent may be executed in a different order than described or illustrated in this patent.

In addition, the terms above, below and the like in the description and claims are used for descriptive purposes and not necessarily for describing relative positions. It will be understood that the terms so used are interchangeable under suitable conditions and that the embodiments of the invention described in this patent may be executed in a different order than described or illustrated in this patent.

It is to be noted that the term "containing" used in the claims should not be interpreted as being limited to the means listed thereafter; this term does not exclude other elements or steps. This should therefore be interpreted as an indication of the presence of the specified elements, integers, steps or components referred to, but does not exclude the presence or addition of one or more other elements, integers, steps or components, or groups thereof. The scope of the expression "means A and B containing devices" should therefore not be limited to devices that consist exclusively of components A and B. This means that with regard to the present invention, A and B are the only relevant components of the device.

Reference in this specification to "a particular embodiment" or "an embodiment" means that a particular element, a specific structure or a specific property described in connection with the embodiment is included in at least one embodiment of the present invention. The presence of the expressions "in a particular embodiment" or "in an embodiment" at various places in this specification thus does not necessarily refer, but possibly to the same embodiment. Furthermore, the relevant elements, structures or

BE2018 / 5514 features can be combined in any suitable manner in one or more embodiments, as will be apparent to a person skilled in the art from this disclosure.

Similarly, it should be borne in mind that in the description of exemplary embodiments of the invention, various features of the invention are sometimes grouped in an embodiment, figure or description thereof for the purpose of streamlining the disclosure and facilitating the understanding of one or more more of the various aspects of the invention. This method of disclosure, however, should not be construed to reflect an intention that the claimed invention requires more elements than those explicitly mentioned in each claim. On the contrary, the following claims reflect that aspects of the invention are present in less than all elements of a single of the embodiments described above. Thus, the claims after the detailed description are hereby expressly incorporated in this detailed description, wherein each claim stands on its own as a separate embodiment of the present invention.

Furthermore, while some embodiments described in this patent include certain but not other elements included in other embodiments, combinations of elements of different embodiments are within the scope of the invention, and form different embodiments, as will be understood by experts in the field. For example, in the following claims, any of the claimed embodiments can be used in any combination.

Numerous details have been set forth in the description of this patent. It is to be understood, however, that embodiments of the invention may be practiced without these details. In other cases, well-known methods, structures and techniques have not been shown in detail in order not to complicate the understanding of this description.

In general, with lighting systems, it is desirable to have stable lighting intensity. When a plurality of lighting systems, which may be of a different nature and design, are driven by a single power source, compensation is required to ensure that all systems receive a voltage sufficiently high to activate the light sources. On the other hand, it is also desirable to reduce power dissipation, which usually happens when

BE2018 / 5514 light sources or their drive elements are overcharged with a voltage higher than that required to provide sufficient lighting.

These requirements are especially important in automotive applications where there is usually a constant power source in the vehicle (for example a battery). For safety reasons, sufficient intensity must be provided in all lighting systems. In an extreme example, the headlights should not reduce their illumination when the direction indicators are used. The separate power source must be able to support all electronic systems, including different types of lighting systems, and to stably drive them all. However, the electronic network should not be too complex. Lower complexity facilitates installation, problem diagnosis, replacement of parts, leads to lower system costs, etc.

LED-based lighting systems in vehicles are usually divided into different LEDs, including a number of LEDs connected in series. LEDs have a low power consumption, but they tend to suffer degradation (aging) over time, as well as thermal degradation.

When in embodiments of the present invention reference is made to an "LED strip", reference is made to a plurality of LEDs connected in series. Different LED strips from one or all lighting systems can be powered by a power source. Where in embodiments of the present invention reference is made to "supply voltage (VS)", reference is made to the supply voltage for the various LED strips and their drive elements of a particular system or for all lighting systems.

A particular lighting system according to the embodiments may comprise one or more LED strips, which form an 'LED cluster'. A certain lighting system can comprise at least one LED cluster.

In a first aspect of the present invention, a system is described that provides control and compensation of variations in the voltage drop of electronic systems, including lighting systems. In particular, voltage calibration is provided for one or more LED lighting systems comprising LED clusters, using a main control unit (MCU) and at least one control unit per LED cluster.

The MCU includes at least one connection to a power source (e.g., a battery, e.g., a 12 V or a 48 V battery) and at least connections to the plurality of

BE2018 / 5514 LED clusters, for example parallel connections with the LED clusters, to provide a supply voltage VS to the lighting systems. For example, the MCU may include at least one inverter for adjusting a voltage from a power supply (e.g., a battery) to an output power supply VS for the lighting system. In this way, the MCU provides a general supply voltage for all LED strips via the inverter.

All LED strips are therefore connected to only one common supply voltage, which is emitted by the MCU. Because the LED strips can be different in the number and type of LEDs in order to optimize the supply voltage VS, the present invention provides an MCU adapted to adjust its output supply voltage in accordance with the power needs of the LED clusters. For example, the MCU may include a controller, such as a voltage controller or calibrator. Control can alternatively or additionally be provided by controlling the inverter using a micro controller. Control can be done by, for example, any suitable adjustable linear voltage regulator. For example, a controller may include an adjustable power source with switched mode. The specific implementation of the switched mode power supply may include a buck inverter, a boost inverter, a buck-bust inverter, or another switched mode power supply inverter, for controlling the voltage level of the car battery at a supply voltage level that is adapted to drive LED strip (s) and their drive elements.

The MCU may optionally include fail-safe and diagnostic mechanisms and functions, for example, by incorporating a voltage measuring unit for measuring the output power supply VS. The MCU may be able to detect the actual voltage at the output. The MCU can compare the requests of the connected control units to raise or lower the voltage, according to the calibration values required by the control units to ensure correct drive of each strip. In some embodiments, the MCU has an expectation of which voltage, or which voltage within an expected range, must be provided for a particular control unit. For example, the expectation may be based on a calibration value stored from a previous calibration. If a control unit requests a voltage outside the expected voltage range, the MCU can diagnose that there is a malfunction in the system. Examples of voltage measurement units include analog13

BE2018 / 5514 to digital converters (ADCs), comparators, optionally with an adjustable reference voltage, etc.

The MCU may also be programmed, or may contain electronic devices, to build a gateway function to a higher level network of the vehicle, e.g., a primary network, such as a Local Interconnect Network (LIN) or a Controller Area Network (CAN) can be, including associated protocols.

In some embodiments, the MCU may include a memory unit for storing different calibration values, which is coupled, for example, to different lighting system configurations. The memory unit can be of any suitable type. It can be a programmable memory, such as a random access memory (RAM), etc. It can be a non-volatile memory (NVM), such as an EEPROM, a flash memory, etc., which can be accessible at certain times (e.g. can reuse the values stored therein after each activation of the lighting system (s), thereby obtaining a robust and reliable system that can save time when the system must provide the specified function in operating mode. In any case, the memory unit should preferably be able to store new or updated values at any time, in the case of, for example, recalibration during operation, during diagnosis or during garage maintenance. Thus, a single one-time programmable memory is less preferred.

The present invention can provide control of LED driving by providing at least one control unit per cluster. The MCU can exchange information with the control units of the clusters. This can be done through electrical connections. The MCU may, for example, be connected via a BUS interface (e.g., a LIN bus or CAN bus) to one or more control units. This network can be seen as a secondary network, for example a network that controls a multitude of or all lighting systems in, for example, a vehicle (however, any other suitable data transfer can also be used).

The control units of the present invention include a connection to each LED strip of the same cluster. In embodiments of the present invention, the connection may receive the generic name "node" or "pen."

Furthermore, the control units include a voltage measuring unit that is used to obtain the voltage drop in the LED strip. The voltage can, for example, be measured at a node between the LED strip and the control unit, e.g., between

BE2018 / 5514 the LED strip and a corresponding drive element in the control unit. Said voltage will receive the name "Vpin" in the present invention. This notation can be extended to any type of connection.

The control unit further comprises access to a memory for storing values of the voltage Vr, wherein said Vr is the minimum voltage on the aforementioned pin required to drive an LED strip. The control unit may, for example, comprise a connection or interface to retrieve the information from an external memory (e.g., a connection to a primary or secondary network, etc.). In preferred embodiments, the information can be stored in a memory implemented in the control unit itself.

Each control unit further comprises an LED driver (including, for example, variable current sources, switching elements controlled by a PPE unit, a combination of each of these, etc.) per LED strip in each cluster. Two or three LED strips in a cluster can, for example, each be connected to a corresponding driver of the control unit. In that case, the control unit must contain at least two or three drivers. If a control unit is an integrated drive circuit, the number of drivers can be limited. If a cluster, in that case, contains more LED strips than there are drivers in the available control unit, the cluster can be connected to two or more control units. If the number of LED strips is, for example, very high, the cluster can be connected to a plurality of control units, each LED strip having a drive channel, e.g. a connection through the pin, to a drive unit of a control unit of the plurality thereof. The control units of the same cluster can, in turn, store values of the minimum required voltage Vr for the same requirements of, for example, brightness corresponding to the function of that specific cluster.

The control units may further comprise a unit for comparing a measured voltage with the required voltage Vr. For example, a comparator can be implemented. For example, a processing unit may be included to process the signals from the voltage measuring unit. The processing unit can be, for example, a micro controller, a CPU or any other suitable hardware unit. The processing unit can provide a signal to the MCU, including information regarding the voltage on the aforementioned pin or a voltage drop across the LED strip, in particular whether it is higher or lower than a predetermined range of values. The

BE2018 / 5514 control unit can share this information with the MCU via communication interfaces in a network.

Furthermore, the control unit may optionally include a diagnostic function, in a manner similar to the MCU. The control unit can read the voltage at the output of the MCU. If the voltage on the connected LED is too low, it can send messages to the MCU, for example during normal operating mode (not just during calibration). This can, as before, be activated by incorporating a voltage measuring unit, such as ADCs, comparators, optionally with an adjustable reference voltage, etc., adapted to read the voltage VS at the output of the MCU, or by the control units to give access to a voltage measuring unit in the MCU for measuring VS.

The control units can be provided in a separate integrated circuit, for example in monolithic circuits. The control units may also be arranged as a plurality of circuits, the multiple components of which are implemented as separate circuits, e.g., an ADC, a communication transceiver (e.g., LIN transceiver or CAN transceiver), a CPU or a state machine, a PBM unit, which are formed as separate circuits.

Regarding the lighting system or lighting systems, the clusters can be part of the same type of lighting system, or each cluster can be part of a different type of system. For example, a cluster that contains two LED strips can be part of the rear light lighting, while another cluster that contains a single LED strip can be part of the turn signal system. In any case, in accordance with embodiments of the present invention, all clusters are connected to the same MCU, but each cluster is connected to at least one associated control unit.

In embodiments of the present invention, a lighting system comprises at least one cluster, which comprises at least one LED strip. Because the control units are connected to clusters, accurate drive and voltage readings and compensations can be obtained for each strip in a cluster using a single control unit, thus reducing the complexity of the system. In some embodiments, a cluster may contain a single strip that contains one or more LEDs. In some embodiments, a cluster may contain a strip with four LEDs, or three LEDs. In some embodiments, combinations of different clusters of

BE2018 / 5514 different types, number of strips and / or number of LEDs per strip are included. The system is suitable for driving any of these combinations of clusters that form lighting systems, which can be different from each other, and to ensure correct control and lighting of all systems.

In an exemplary embodiment of the present invention, shown in FIG. 1, a car lighting system includes at least two clusters (two are illustrated in FIG. 1), one of the clusters comprising a plurality of strips. The MCU 10 may include a voltage converter, e.g., a DC / DC converter 16, for adjusting the supply voltage (e.g., vehicle battery supply) VBAT to a supply voltage VS for, for example, the rear light system of a vehicle. The supply voltage VS may be higher or lower than the supply of the car battery.

The lighting system may contain several LED clusters 29, 30, and each LED cluster may contain one or more LED strips 27, 31, which LED strips each comprise at least one LED, possibly a plurality of LEDs 26 connected in series. The present invention can be used on strips containing a single LED, it is advantageous to have several LEDs in series, because the correct driving of all LEDs in the strip is ensured, whereby a system with much better lighting and eye-catching possibilities than a single LED LED becomes possible.

The MCU 10 may further comprise a voltage measuring unit 14, for example an ADC or a comparator with an adjustable reference voltage, for measuring the output supply voltage VS of the voltage converter, e.g. DC / DC converter, which is supplied to the different LED strips.

The MCU 10 may further comprise a memory unit 11 for storing a value of the supply voltage VS to be used at the start of a calibration procedure. It can save the voltage converter settings for adjusting the voltage of VBAT to the power supply voltage for the lighting systems. The memory unit 11 can optionally store other values such as minimum required voltages for LED strips and information regarding previous calibrations.

While the output power supply voltage VS to be supplied to the LED strips can be controlled and measured by the MCU 10, the voltage drop or the current through the LED strips can also be controlled and measured by a control unit, e.g., a control unit 20 which is linked to each associated LED cluster 29.30. The control unit 20 in embodiments of the present invention cannot only handle it

BE2018 / 5514 drive the associated LED cluster (for example, by controlling the current through each strip), but can also measure drive parameters, such as the voltage on each aforementioned pin, optionally also on the supply voltage VS, and from this he can also derive the voltage drop in each strip of the cluster. With reference to FIG. 1 comprises a control unit 20, for example, a rear light control IC, a LED drive unit, for driving the LED strips 27, 31 and for, for example, controlling the driving thereof and their light intensity. The LED drive unit may, for example, comprise a controllable current source 23, a switching element 22 (e.g., a transistor) that is controlled by a PBM drive unit 21, or a combination of both.

The control units 20 shown in FIG. 1 each comprises two LED drive units; however, this is not limitative of the present invention. In the embodiment illustrated in FIG. 1, both LED drive units of the control unit 20 connected to the cluster 29 containing two LED strips are used. However, only one LED drive unit of the control unit connected to the cluster 30 containing a single LED strip is used. As can be seen, the same architecture can be used for a wide range of applications, configurations and vehicle models, without the need for special controls. The control units 20 comprise a voltage measuring unit 24, e.g., an ADC, for reading the voltage at the connection between the control unit 20 and the LED strip. In particular, each LED drive unit of the control unit can be connected to a strip of the associated cluster. In some embodiments of the present invention, a drive pin may be included in the connection between the control unit and the LED strip in a cluster. A drive pin can, for example, connect a microchip comprising the control unit and the LED strip. In embodiments of the present invention, there may possibly be different voltages Vpin at the drive pins for different LED strips. An LED strip 31 can, for example, be connected to the pin DRV1 and thus to an LED drive unit. Another LED strip 27 can be connected to another pin DRV2 and thus to another LED drive unit of the same cluster 29.

The voltage measuring unit 24 could be connected via, for example, a multiplexer (not shown here) to each pin including the supply voltage VS pin. A multiplexer has the advantage that it can read voltages on a plurality of pins with a single device, thereby improving compactness. Such a voltage measuring unit 24 may, for example, comprise an ADC and / or a comparator with a configurable reference voltage. The

BE2018 / 5514 control unit 20 may further comprise a processing unit, for example a micro-controller 25, which can read and process the measurements of the voltage measuring unit 24. The micro controller 25 can also control the drive of the LED strips by providing control over the drivers, e.g., over the controllable power source 23, and / or the PBM drive unit 21. The control unit 20 can have access to a memory unit (e.g., a unit included in the control unit 20, or access to the memory unit 11 implemented in the MCU) which stores various required voltages Vr to perform the comparison. The memory may contain programmable options so that the Vr can be varied and adjusted according to each specific application.

The processing unit 25 can further be connected to a communication interface 28 of the control unit 20, to communicate with the MCU 10 whether the measurement falls within the accepted parameters or not. The control unit 20 includes a signal generator to generate a signal and send it to the MCU 10 if the measurement is higher or lower than expected, for example outside of a predetermined margin of error. The MCU 10 would then decrease or respectively increase the supply voltage VS.

It should be noted that one or all parts of the control unit 20 may be included in a single integrated circuit, such as a semiconductor chip, thereby further improving compactness.

The main control unit 10 may include a secondary communication interface 15 for exchanging data with the communication interface 28 of each control unit 20 of the system. The MCU 10 and the control units 20 thus communicate with each other via this secondary network, e.g. via the lines 17 of the secondary network. This is advantageous in many vehicles that contain a specific network architecture for some or all of the lighting systems, which is separate from the rest of the network architecture and which reduces the risk of interference with other systems of the vehicle, eg, security systems, engine and cruise control, remote and collision sensors, air conditioning, communication systems, etc. Advantageously, this secondary network does not have to show high performance, so that the costs of implementation can be reduced, for example, with the help of a LIN. Implementing multiple control units in a secondary network is usually less expensive than implementing them on the CAN wired by a complete vehicle, and providing a single connection to the CAN via the MCU. In that case the MCU is one

BE2018 / 5514

CAN - LIN gateway. However, other implementations are allowed. A CAN can be used for MCU and control units, for example, if the system is viewed as a safety critical system, as shown in FIG. 2. In other embodiments, the MCU can be connected to a LIN for a very inexpensive network. In such a case, the MCU is a slave with regard to a higher level network but a master with regard to all control units. In that case the MCU is a LIN - LIN gateway.

The exchanged data can at least include data about whether the voltage drop measurement has been performed and the result thereof (from the control unit 20 to the MCU 10), but it can also include other signals, for example signals to activate calibration.

The voltage converter 16, e.g., DC / DC converter, of the MCU 10 provides an adjustable output supply voltage VS. If a first group of clusters is used, an adjusted supply voltage value VS can be obtained, which can differ from the adjusted value if a second, different group of clusters is used. The multitude of adjusted US supply voltages can form a list of calibration values. These calibration values can be stored, for example in a central memory of the vehicle, or in a memory unit 11 which is included in the MCU 10.

The status of the system or systems can be communicated to a higher level processing unit (e.g., the Body Control Module (BCM) or a comparable controller of a vehicle), for example, for receiving orders for said central processing unit.

The higher level processing unit also provides control of which of the lighting systems is to be activated. The communication can be provided by a special primary communication interface 13 included in the MCU 10, which provides connection to the primary network, e.g., via network lines 18. However, the present invention is not limited to the aforementioned architecture. In some embodiments of the present invention, the primary and secondary networks are included in a single, shared network, as previously introduced.

Such an embodiment is illustrated in FIG. 2, which shows a specific vehicle architecture with a common network. A common network can easily be obtained with a CAN implementation of the primary and secondary networks. In that case, only one communication interface 113 in the MCU 10 is needed. Two communication paths, CAN high line 101 (CANH) and CAN low line 102 (CANL),

BE2018 / 5514 can be included together with an earthing line. In this case, a signal can be sent via the CAN to the MCU 10 to start a calibration. Communication between control units 120 and MCU 10 takes place via the CAN via general interfaces 128 in the control units 120. The activation schemes using these lines are known to those skilled in the art.

In a second aspect, a method for voltage calibration for LED-based lighting system is presented. The method allows calibration of a power supply voltage for lighting systems comprising a plurality of LED strips of light emitting diodes (LEDs), thereby compensating for the effects of differences in the LED strips, such as, for example, the number or type of LEDs in the strips and thus the voltage drop across the LED strips.

The method, schematically outlined in the flow chart of FIG. 3, includes the steps of adjusting the supply voltage 301 to a first voltage VS for which all LEDs in the plurality of LED strips are expected to function. This first voltage can be a calibration value, for example a calibration value obtained during a previous calibration method and stored in a memory. In embodiments of the present invention, a voltage converter (e.g., the DC / DC converter 16, 116) sets the supply voltage VS from an external power supply (e.g., the battery of a vehicle) by converting said voltage to the output supply voltage VS. The method further includes the step of providing 302 the first voltage value to the plurality of LED strips 27, 31 and to control units 20, 120. The LED strips 27, 31 are grouped into clusters 29, 30, wherein each cluster 29, 30 comprises at least one LED strip. The method can advantageously be used for a plurality of clusters 29, 30, thus applying the same voltage to a plurality of clusters and obtaining centralized control. In embodiments of the present invention, the method is used to power a plurality of clusters, wherein at least one cluster contains a plurality of LED strips. Different clusters can, but do not have to, contain a different number of LED strips. High design and installation flexibility can be obtained by grouping different LED strips and connecting them to the same control unit 20, 120, while simultaneously providing an adjustable common supply voltage VS to all LED strips of one or more clusters. Another

BE2018 / 5514 advantage is to improve the compactness and costs of the system. A drive unit requires a certain area of package and / or IC. A compact micro controller must be able to control at least two or three strips of a cluster.

The method further includes measuring 303 at least one parameter related to driving the LED strip. The method may, for example, include measuring a voltage Vpin at a node between each control unit 20, 120 and its respective one or more strips. The node may be, for example, the connection of an LED strip opposite the connection to the MCU 10, or, analogously, the connection of the LED strip to the corresponding LED drive unit in the control unit 20, 120. The voltage drop (VS - Vpin) over each strip, between the supply voltage and the voltage at the node between each strip and the control unit, can moreover be obtained, which can differ from cluster to cluster, or even between strips of the same cluster.

The resulting voltage Vpin at the node between a strip and the control unit is then compared 304 to a preset voltage Vr required for the respective strip. The preset voltage can be the minimum analog voltage required to provide a required light information from a particular LED strip connected to the control unit. The preset voltage Vr can advantageously be as low as possible in order to have minimal power dissipation in the control unit, but as high as is necessary to enable correct current or voltage regulation of the connected LED strip.

In embodiments of the present invention, the preset minimum voltage Vr may be different for each cluster, and have been selected according to the application (e.g., lights for lighting have different requirements than lights for striking, so the Vr will be different in clusters of these systems ). A different Vr can also be assigned to each strip, advantageously taking into account different numbers of LEDs in each strip for the same cluster. In some embodiments, the preset minimum levels of the voltage Vr may be programmable.

The measurement and comparison can be performed in any suitable voltage measurement circuit, e.g., an ADC 24,124, and processing unit of the control unit 20,120 (e.g., in the microcontroller 25, 125). A signal can be generated 305 according to the result of the comparison. If the voltage measured at the node between the LED strip and the control unit is lower than one

BE2018 / 5514 predefined error voltage lower than the preset voltage Vr, the MCU 10 is warned 308 that the supply voltage VS is too low. In typical vehicle applications, the preset voltage Vr can be, for example, between 0.5 V and 3.0 V, for example 0.5 V or IV or 2 V or 3 V. The predefined error voltage can, for example, be between 5 and 20% of Vr. In general, the error voltage must not be too small to provide a robust drive. In some embodiments of the present invention, a "LOW" warning signal may be generated in the corresponding processing unit, for example in the micro controller, to inform the MCU 10 that the supply voltage VS is too low. The generated signal may contain information regarding the value of the measurement (how low the measurement is) and / or how much it differs from the preset voltage Vr. The communication can be performed via any suitable communication network, such as, for example, a wireless network (although this is less preferred because the costs are higher). Preferably, the MCU 10 exchanges (receives and / or transmits) data with the control units via a wired communication network. The control units receive information to control the lighting system and send the diagnosis information back to the main unit 10. The information may, for example, relate to the current through the LED strip, the voltage drop across an LED strip, the voltage on the connection point of the LED strip to the control elements, the supply voltage VS, etc. In some embodiments, the MCU 10 can send the information to a primary network in a gateway function. In some embodiments, all control units 20, 120 and the MCU 10 are in the same network hierarchy and are controlled by the primary network. In other embodiments, some or all of the control units 20, 120 are connected to the MCU 10 via a secondary network, and data exchange with the primary network is performed via the MCU 10. Any other suitable communication means may be used, resulting in a highly flexible method.

In addition, the method may include generating a warning signal different from the "LOW" signal when the measured voltage is higher than a predefined error voltage that is higher than the preset voltage Vr. Said signal, identified as "HIGH" signal, 309 reports that the supply voltage VS is too high, and it may include information regarding the value of the measurement, and / or how much it differs from the preset voltage Vr.

BE2018 / 5514

In embodiments of the present invention, the predefined error voltage over and below the preset voltage Vr may be application dependent, and may be different for each cluster. This depends on the resolution setting of the measurement and it may be different, but usually it will be the same for the strips of a cluster. The predefined error voltage over the preset voltage Vr may differ from the predefined error voltage below the preset voltage Vr. Furthermore, a plurality of the aforementioned predefined error voltages can be stored and used in accordance with the specific configuration and / or application, thereby ensuring a hysteresis in the control circuit between increasing or decreasing the supply voltage VS, as explained below. In some embodiments, the predefined error voltage levels may also be programmable.

The method further includes adjusting 306 the supply voltage VS to an adjusted supply voltage VS based on the received warning signal. In some embodiments of the present invention (e.g., the embodiment of FIG. 1), variation of the voltage converter output, e.g., DC / DC output, supply voltage VS may be output by a control unit, e.g., micro controller 12, 112 in the MCU 10 .

If the MCU 10 receives a "LOW" signal, the MCU 10 then increases the supply voltage VS (e.g., by increasing the voltage conversion, for example by changing the configuration or setting of a DC / DC converter by means of a micro controller) to to ensure correct lighting and control of each LED strip of each cluster. The MCU 10 increases the supply voltage VS until the voltage Vpin at the node between the LED strip and the control unit reaches or exceeds the preset voltage Vr. When this condition is met for all LED strips of all control units of a particular cluster, the calibration is complete for this particular cluster and a particular VS setting for this particular cluster is stored, at least temporarily stored, by the MCU 10. The entire calibration is complete when all control units of all clusters are applied. The MCU 10 then derived individual US settings per cluster during calibration.

On the other hand, if the MCU 10 receives a "HIGH" signal, the MCU 10 lowers the supply voltage VS until the voltage Vpin on the node between the LED strip and the control unit reaches the preset voltage Vr, which leads to a decrease in power dissipation and heating in the drive elements of the control unit, what

BE2018 / 5514 leads to a reduction in the risk of damage or a reduction in the service life of the drive elements of the control units. Calibration for a particular cluster is complete when the first controller reaches this condition for the first connected strip. The MCU 10 can then only increase the voltage VS in a small step, so that Vpin is again higher than Vr. The calibration is generally complete when all control units of all clusters are exercised. The MCU 10 then also derived individual US settings per cluster during calibration.

In embodiments of the present invention, the voltage Vpin at the node between the LED strip and the control unit need not exactly correspond to the preset voltage Vr, and it is sufficient that the voltage Vpin at the node between the LED strip and the control unit is within a predefined error of, but higher than, Vr. This ensures that the minimum required voltage is supplied to all LED strips of a certain cluster.

In embodiments of the present invention, the MCU 10 uses the setting leading to the highest US, the value from the derived individual US settings for each cluster, and stores this setting for further use. The MCU 10 can be programmed to select the highest of the various required supply voltages 310 as the adjusted output supply voltage VS. Therefore, no LED strip will be under-energized, and correct lighting can be obtained.

In other embodiments, the setting of the inverter that leads to the highest US and the configuration of clusters that resulted in that highest US are stored 307. When the same clusters are activated, the MCU uses the highest VS stored for that configuration.

In other embodiments of the present invention, the MCU 10 uses all derived individual US settings per cluster and stores these settings 317 for further use. Because the MCU 10 could control all clusters of the lighting system via the bus interface of FIG. 1, the MCU 10 always has the information regarding which cluster works. The individual VS setting for a particular cluster can be chosen for supplying VS to the lighting system. If multiple clusters work simultaneously, the US setting of the cluster leading to the highest US can be chosen for all lighting systems (e.g., all clusters).

The stored setting includes the setting or configuration of the voltage converter for converting the voltage from a main source to the

BE2018 / 5514 required adjusted output power voltage, and this may include information regarding the number of strips being driven, the illumination intensity, the value of VS needed to reach Vr for all the strips in that cluster.

Saving a setting can include saving data values. During the calibration, for example, different data values for the supply voltage VS (depending on the clusters) are collected. These data values can be stored in a memory. The data value for the supply voltage VS, data for setting the inverter and providing such a data value of the supply voltage VS and the cluster corresponding to those values can be stored. The voltage converter can contain a control register. For an 8-bit register, data values can be stored in a range between OOhex and FF hex. Each stored data value can correspond to a different analog output value of the supply voltage VS. The MCU can select a data value from the memory (depending on which cluster is used) and can record this value in the drive control register. If more clusters are used in a further drive of lighting systems, the MCU can select the setting that offers the highest value of all activated clusters.

Optionally, a third type of warning signal 311 can be provided when the signal is within the prescribed parameters (e.g., within the predefined error voltage), which serves as a control point signal to indicate that the LED cluster is working and that the communication channels are active.

In some embodiments in which a single Vr is defined per function (e.g., to obtain the VS required for all LED strips from a single cluster in which all Vr are the same for all strips), the method may use "HIGH "and" LOW "signals. In such a case, the MCU stores the US setting for that specific cluster according to the minimum required to operate, but that will lead to low power dissipation. However, when many Vr are used, only "LOW" signals can be used. In a practical example, in normal operating mode, an output voltage for rear fog light systems VS (fog) can deviate from the output voltage for rear lights VS (rear). Both values can be derived during calibration and, for example, stored in memory 11 of the MCU. If fog lamps and rear lights are on, the setting of the inverter with the highest US is chosen by the MCU (either fog lights or rear lights), because if the lowest US would be

BE2018 / 5514 selected, a lighting system may not work according to the specified light output. Thus, the MCU will not adjust VS according to a lower VS requirement ("LOW" signal) if the Vpin exceeds Vr, for this specific case of clusters with different Vr.

In another embodiment, different predefined error voltages can be specified to ensure a certain hysteresis between increasing / decreasing the supply voltage VS, to have sufficient room against disturbances on the supply voltage VS.

The method further includes storing 307 the adjusted supply voltage settings as previously described. The adjusted supply voltage can be stored in an external memory unit, or it can be stored in an internal memory unit, for example a memory unit in the MCU 10.

In some embodiments of the present invention, a signal can be generated 312 by the MCU 10, which can be sent to an output via the primary network, indicating that the calibration has been completed (e.g., activating a "configuration-executed mark") .

In an embodiment of the present invention, this marking can also be stored in one of the memories described, so that a calibration step may no longer be necessary during a subsequent system activation.

In embodiments of the present invention, the method includes starting from a first supply voltage VS, which can be very low (low enough to ensure that no cluster will have the required voltage Vr in one of its strips) or very high (high enough to ensure that all strips of all clusters will have a voltage that is at least higher than Vr). All Vpin voltages are measured on all controllers and all clusters. During calibration, there may be two options, depending on the first used supply voltage VS.

a) FIG. 4 illustrates a first possibility, setting 313 to a low supply voltage VS: The condition Vpin> Vr is not achieved for any Vpin. The microcontrollers send 308 a LOW signal and the MCU 306 increases the supply voltage. The Vpin> Vr condition can be met for a first Vpin in a certain cluster. The rest of the strips from that cluster (and from other clusters) require higher supply voltage VS, so the supply voltage VS is increased. If the condition Vpin> Vr is met for all Vpin (all strips) of a first specific cluster, the setting S that results in that supply voltage VS is stored 307 for

BE2018 / 5514 that specific cluster, and the calibration of that cluster has been completed 316. The setting can be stored, for example, as a data matrix, eg 'S (cluster 1)'. In the case of a single cluster, calibration would be complete, but in the case of multiple clusters, the rest of clusters still do not necessarily meet the condition in each of its strips. Hence, LOW signals are generated and supply voltage VS continues to increase. If the Vpin> Vr condition is reached for all Vpin of a following cluster, the new setting for that cluster is saved, eg S (cluster 2) and so on. When all clusters are complete and Vpin> Vr all Vpin for all clusters, the calibration is complete 312.

This process can be performed simultaneously for all clusters, or cluster for cluster, or simultaneously for a subset of the clusters, and then for at least one other subset of the clusters. If the process is not performed for all clusters at the same time, the clusters must be calibrated in a specific order, or else the VS supply voltage must restart at the lowest first value for each cluster. The specific order can be based on an estimate of the lowest Vr required by each cluster, so the clusters are calibrated in a sequence of increasing minimum Vr. Alternatively, if the MCU detects that a cluster has been calibrated and the calibration settings have been saved, any further signal from microcontrollers from that cluster can be ignored.

b) FIG. 5 illustrates a second possibility, setting 314 to a high supply voltage VS: The condition Vpin> Vs for all Vpin is satisfied. The microcontrollers send a HIGH signal and the MCU lowers the supply voltage VS until the condition Vpin <Vr is reached for a first Vpin for a first cluster. The value of the supply voltage VS is increased again 315, with a small margin (for example, by increasing it with a predefined error voltage), to ensure that the condition Vpin> Vr occurs again. Alternatively, the MCU may decrease the supply voltage VS until Vpin is strictly above Vr, within a predetermined error margin. In any case, the new value of Vpin is closer to Vr than the first high value of supply voltage VS, thereby reducing power dissipation. The settings are saved or recorded as before, eg 'S (cluster 1)'. The calibration for that cluster would have been completed 316. In the case of a single cluster, calibration of the entire system 312 would have been completed, but in the case of multiple clusters, the supply voltage VS is further reduced until the first Vpin for another cluster is sufficient

BE2018 / 5514 with the condition Vpin <Vr. The value of the supply voltage VS is again increased as a minimum until, for this first Vpin of the following cluster, the condition Vpin> Vr occurs. The setting is stored in a memory such as S (cluster 2). The process is repeated for the remaining clusters. For each cluster calibration, the already calibrated cluster gives LOW signals, which are ignored by the MCU because the setting corresponding to the calibrated clusters has already been saved.

In this case, the minimum supply voltage setting VS for each cluster is stored 317, so that the condition Vpin> Vr for all Vpin of all controllers for a given cluster is met.

Both calibrations can be combined in some cases. If, for example, calibration is performed cluster by cluster, some clusters can be calibrated from a supply voltage VS higher than required to obtain Vr in all their strips, and other clusters can be calibrated from a supply voltage VS lower than required to Available in all their comics. For a cluster with many strips, for example, from a high supply voltage VS, the calibration can end quickly, with values for the voltage at the node within a predefined error above Vr. On the other hand, for a cluster with one or only a few strips (e.g., two), starting from a very low supply voltage VS can lead to a supply voltage VS that gives a Vpin very close to Vr, thereby reducing power dissipation. In some embodiments, only a single supply voltage VS is stored, the minimum value for which all the strips of each cluster will operate with minimal power dissipation and obtain a Vpin that is slightly higher than the required voltage.

At a subsequent activation of lighting systems (e.g., at a subsequent activation of one or more lighting systems) the MCU will either:

i) select the setting that leads to the highest supply voltage VS of all stored settings. This can be applied to the cases where all clusters are used together.

ii) select the setting that leads to the highest supply voltage VS of the clusters currently being used. The MCU has information about which clusters are used, and the selected settings will give the highest supply voltage VS of all used clusters. If only one cluster is used, the supply voltage VS setting of this single cluster is used.

BE2018 / 5514

An exemplary implementation of the method can be applied with embodiments of the first aspect of the present invention, for example the embodiment shown in FIG. 2. An inverter 116 in the MCU 10 sets the supply voltage VS. This can be done by converting the voltage from an external source or battery, outputting a first supply voltage VS to the clusters 29, 30. The control units 120 receive the supply voltage VS, which in turn becomes active, as well as each LED strip 27.31, in the clusters 29.30. The control units 120 may include elements for controlling the driving of the LED strips of their associated cluster. This driving can be done, for example, by current control, e.g., with an LED strip driver 123, in accordance with the required light intensity. The voltage Vpin is measured at each node 103, 104 between each LED strip 27, 31 of each cluster 29, 30 and their corresponding control unit 120, and compared to a preset required voltage Vr (which can be stored in a memory unit, in the controller 120 or in the MCU 10). If the result is lower than Vr, or higher than an error margin above the preset required voltage Vr, a signal is generated including information regarding whether the voltage Vpin on the node 103, 104 is too high or too low. Each control unit 120 performs this action. Voltage reading, comparison and signal generation can be done with one or more readers and optionally integrated comparators in any combination. The reading can be done, for example, with a reader 124 and comparison and signal generation can be done with a processing unit 125 or by all other means. However, this configuration is not limiting, and the reader and comparator may be integrated in the same unit.

If at least one warning signal is generated, the signal is reported to the MCU 10, for example between a general communication interface 128 in the controller and the communication interface 113 in the MCU 10, by the CAN network. The MCU 10, upon receipt of the notification, regulates the first supply voltage VS into an adjusted supply voltage VS. If multiple warning signals are received, the MCU 10 can be programmed to select a supply voltage VS that drives all LED strips, thereby ensuring that the optimum voltage drop for at least one LED strip is provided, which simultaneously higher voltage drop for the remaining LED strips.

The MCU 10 can then store the adjusted supply voltage value VS and the configuration of the lighting system (e.g., settings of the inverter that such a

BE2018 / 5514 obtain voltage value, which systems are driven, and their required light intensity) in a memory 11 ('configuration memory'). The control, control of the voltage measurement of the supply voltage VS and other actions such as reading the supply voltage VS at the output (e.g., via a voltage measuring unit 14) can be controlled by a single processing unit 112 inside the MCU 10. The next time that When a certain configuration is activated, the MCU 10 can supply the previously stored adjusted supply voltage VS obtained for that configuration as the first output supply voltage VS.

It is noted that in the case of FIG. 2, the interface 113 for communication with the control units is also used to communicate with a higher level processing unit, but as can be seen in FIG. 1, alternatively two interfaces 15, 13 can be used in the MCU 10, one for communication via a secondary network with the control units, the other for communication via a primary network with a central unit. In addition, some or all of the elements can be applied to and combined with any implementation of the present invention, not only in vehicles, but also in industrial machines, household appliances, etc.

The present invention can be used with different strips with different numbers and types of LEDs 26. The granularity of the lighting system (e.g., how many LEDs per LED strip, how many LEDs per cluster) is mainly determined by design, optical controls, requested light output, thermal management, color of light, and other parameters.

Therefore, a preset voltage Vr (e.g., the minimum voltage required to operate a particular LED strip, as previously defined) can be defined per cluster, or even per strip, taking into account the granularity of the system. As previously seen, different preset voltages Vr can be used depending on the specific light sources (LEDs, strips, clusters, groups thereof) that are switched on. These values can be stored in a memory of the control units 120, for example a memory included in the processing unit 125 of the control units, or in the memory 11 of the MCU 10, or in a higher level control unit. One or all of these values can be programmable.

BE2018 / 5514

Different calibration values for the voltage converter can also be stored, e.g., in the MCU 10 configuration memory 11, or in an external memory. If multiple clusters are enabled, the highest value of supply voltage VS can be used.

Information about the control and status of a lighting system can be sent to the MCU 10, for example via the primary network. Calibration values for the supply voltage VS can, for example, be programmed externally for a number of lighting system configurations. This information can be sent to the MCU 10, which accordingly will provide the required supply voltage VS for a particular configuration (via the inverter) when switching on the lighting systems that correspond to the programmed configuration. The output supply voltage VS can be obtained, for example, by calculation, because the particular light source and its configuration are known. In other embodiments, the first supply voltage VS can be obtained by using the calibration method in an earlier calibration, thus taking into account the history (degradation, etc.) of the light sources. For example, if multiple light sources are turned on at the same time, the calibration value that matches the highest value of supply voltage VS for the light sources is used. This ensures an application-dependent improved, preferably optimum current management, such that the supply voltage is as low as possible on the one hand, but still high enough so that a separate current or voltage control of each LED strip is possible.

As an example of the importance of power management, the following calculation takes into account a single LED, with a current of ILED = 1A

- Output voltage is VS = 12 V.

- The voltage drop across this LED = 3 V.

- The voltage on the pin is Vpin = 12 V-3 V = 9 V

- Power dissipation at the in the IC would then be P = 9 W

Now, taking into account the same voltage drop and current, but with a lower supply voltage VS:

- Output voltage is VS = 4 V

- The voltage on the pin is Vpin = 4 V-3 V = 1 V

- Power dissipation on the in the IC: P = 1W.

BE2018 / 5514

Thus, the present invention provides adaptation of VS that is advantageous for thermal management and energy savings.

In embodiments of the present invention, the method can be applied at system start-up. The calibration can, for example, be active just after 'switching on' the system. In other embodiments, this may alternatively or additionally be activated in a diagnostic mode, during a garage maintenance, etc. In that case, if a stored signal is present in the MCU 10 indicating that the calibration has been performed ("configuration-executed marking") , said signal can be reset by the processor of the MCU. This recalibration instruction can be received via the primary network connected to the MCU.

The initialization of a calibration step may be initiated by the system at a higher level, as the illumination for example, is used ^th time for the L, or for example, for the l ^th time is switched on or, for example, if there is a garage mode (garage maintenance) . The higher level system can activate the MCU 10, and the MCU 10 can activate the control units 20,120 to start a calibration.

If the primary network and the secondary network are the same, the initialization can be sent in parallel to the MCU 10 and the control units 20,120 by the higher level system.

The initialization can also be started locally by the MCU 10 if during a diagnostic cycle either a failure of the power supply VS is detected by either the MCU 10 or by the control units 20,120, e.g. the voltage on a particular pin is diagnosed as being too low .

Claims (13)

A method of calibrating a power supply voltage (VS) for lighting systems comprising a plurality of LED strips (27, 31) of light-emitting diodes (LEDs) (26), the method comprising: - setting (301,313,314) the supply voltage (VS) to a first voltage value, - providing (302) the first voltage value to the plurality of LED strips (27, 31) and to control units (20, 120) connected to clusters (29, 30) of LED strips (27, 31), each cluster ( 29, 30) comprises at least one LED strip (27, 31), - measuring (303) a voltage (Vpin) in a pin connection between each control unit (20,120) and its respective connected LED strips (27, 31), and comparing (304) the measured voltage (Vpin) with a predetermined set voltage (Vr) for the respective strip, and - if the measured voltage (Vpin) is higher than a predefined error voltage above the preset voltage (Vr) or lower than the preset voltage (Vr), generating (305) in the associated control unit a warning signal around a main control unit (10) to warn that the supply voltage (VS) is high or low, - on the basis of the warning signal, adjusting (306) the first voltage value into an adjusted supply voltage by means of the main control unit (10), and - storing (307, 317) at least the setting for obtaining the adjusted supply voltage for which a minimum supply voltage (VS) is obtained, wherein the minimum supply voltage (VS) is the smallest supply voltage (VS) for which the measured voltage (Vpin) ) in each strip of a cluster is higher than the preset voltage (Vr) for all strips of that cluster (29, 30), wherein setting (301, 313, 314) the supply voltage (VS) to a first voltage value further including (313) the supply voltage to a first voltage value such that the measured voltage is either lower or higher than the required voltage (Vr) for each strip of a cluster, and wherein generating (305) a warning signal further generating (305) contained in the corresponding BE2018 / 5514 control unit of that cluster of a warning signal when detecting that the measured voltage is lower or higher than the required voltage (Vr) for at least one strip of the cluster, for reporting to a main control unit (10) that the supply voltage (VS) is low, or high, respectively, and, upon detection that the measured voltage (Vpin) is lower than the required voltage, the supply voltage (VS) is increased (315) until the measured voltage (Vpin) is higher is then the required voltage (Vr). The method of claim 1, further comprising providing (312) a signal indicating that calibration is complete when a minimum supply voltage (VS) is stored for each cluster (29, 30), or when all control units (20, 120) have a detect measured voltage (Vpin) that is higher than the preset voltage (Vr) for each strip of each cluster, and that deviates less than the predefined error voltage from the preset voltage (Vr) for at least one strip (27, 31) ). The method of any one of the preceding claims, further comprising performing the method at predetermined time intervals. The method according to any of the preceding claims, wherein the preset voltage (Vr) can be defined per cluster and / or strip (29, 30 and / or 27, 31), and / or can be varied according to the configuration of lighting of clusters and / or application. The method according to any of the preceding claims, wherein the predefined error voltage can be varied according to the configuration of lighting of clusters, and / or application. The method according to any of the preceding claims, wherein the preset voltage (Vr) and / or the predefined error voltage can be programmed. The method of any one of the preceding claims, further comprising storing (307) the setting of the inverter for obtaining the highest adjusted supply voltage value required by all clusters, and further comprising adjusting the first supply voltage (VS) ) to the highest adjusted supply voltage value at a subsequent switch-on for controlling the LEDs of the lighting systems. The method of any one of claims 1 to 6, further comprising storing (317) each of the voltage converter settings to provide adjusted supply voltage values required by each cluster, and further comprising adjusting the supply voltage ( VS) according to the highest adjusted supply voltage value that is required by all clusters for further activation BE2018 / 5514 of that cluster, to achieve the preset voltage (Vr) for driving at least each LED strip of each of the clusters. A system for driving a plurality of clusters (29, 30) including at least one LED strip (27, 31), the system including a main control unit (10) including a voltage converter (16, 116) for providing an output supply voltage (VS) and at least one interface (13, 15; 113) for communication with a plurality of control units (20,120), the system further comprising at least one control unit (20,120) for driving at least each LED cluster (29) , 30), wherein each control unit (20, 120) includes: - at least one LED drive unit (20, 21, 23) per LED strip (27, 31) in the cluster (29), - a voltage reader (24,124) for reading the voltage (Vpin) at a node between the control unit (20,120) and each LED strip (27, 31), - a voltage comparator for comparing the measured voltage (Vpin) with a preset voltage (Vr) for that strip, - a signal generator for generating a first signal in the case that the measured voltage (Vpin) exceeds a predefined error voltage above the preset voltage (Vr), or a second signal in the case that the measured voltage (Vpin) set voltage (Vr) not reached, - transmission means (28,128) for transmitting at least a first or second generated signals to the main control unit (10), the main control unit (10) further comprising means for adjusting the output supply voltage (VS) in accordance with the signals generated in each of the control units (20,120) - a processing unit (25, 125) for controlling the LED drive units (20, 21, 23), for obtaining the measured voltages (Vpin) from the voltage reader (24, 124) and comparing it with the preset voltages (Vr), and for generating warning signals. The system of claim 9, wherein each control unit (20, 120) is integrated in a single integrated circuit. The system according to any of claims 9 or 10, wherein the main control unit (10) further comprises a configuration memory (11) for storing a plurality of settings of at least the voltage converter for obtaining BE2018 / 5514 of adjusted supply voltages (VS) as well as a cluster lighting configuration for which the aforementioned value was obtained. The system of any one of claims 9 to 11, wherein a LIN secondary network is provided between the control units (20, 120) and the 5 main control unit (10), which is separated from a primary network for connecting the main control unit (10) to a higher level system. The system of any one of claims 9 to 11, wherein a CAN network is provided between the control units (20, 120) and the main control unit (10), for providing direct connection to a higher level system.