Real-time power management system for a constant current airfield lighting circuit with dynamically changing load

Abstract

Airfield ground lighting system (10), comprising: a plurality of light units (11) arranged in a serial circuit (13), a power supply (12), said power supply (12) comprising a constant current regulator (121); wherein each light unit (11) comprises at least one light source (114) and optionally at least one activatable device; wherein the airfield ground lighting system or a power supply control unit (14) of said system is configured to determine an expected power demand of the serial circuit (13) based on at least one of an expected light intensity level output to be applied, to at least one, in particular each light unit (11) and / or an expected activation state of the at least one activatable device of said light unit (11).

Description

REAL-TIME POWER MANAGEMENT SYSTEM FOR A CONSTANT CURRENT AIRFIELD LIGHTING CIRCUIT WITH DYNAMICALLY CHANGING LOADTechnical field

[0001] The present invention is related to airfield ground lighting (AGL) systems, particularly AGL systems operating with constant current power delivery.Background art

[0002] Reducing carbon footprint, specifically electrical power consumption, has become an increasingly important target for the airfield lighting industry. Electrical power consumption in AGL systems has already been considerably reduced by replacing incandescent lighting technology with light-emitting diode (LED) technology. Nevertheless reducing electrical power consumption remains an ongoing objective. However, the communication of light output intensity through a pre-defined constant current penalizes the power loss reduction in the cables (which is correlated with the square of the current). JP 2024 101391 A, KR 101 464 916 B1 or CN 108 023 488 B discloses an airfield ground lighting system.Summary

[0003] According to a first aspect of the present disclosure, there is therefore provided an airfield ground lighting system, comprising: a plurality of light units arranged in a serial circuit, a power supply adapted to supply the plurality of light units with power in the form of a constant current circulating in the serial circuit, said power supply comprising or consisting of a constant current regulator; wherein each light unit comprises at least one light source and optionally at least one activatable device; wherein the airfield ground lighting system or a power supply control unit of said system is configured to determine an expected power demand of the serial circuit based on at least one of an expected light intensity level output to be applied, to at least one, in particular each light unit and / or an expected activation state of the at least one activatable device of said light unit, and optionally at least one sensed characteristic of an environment of the serial circuit and optionally an actual power absorbed by the serial circuit or at least one, in particular each one, of the plurality of light units.

[0004] According to specific embodiments of the invention, the airfield ground lighting system comprises one or more of the following feature(s):• the airfield ground lighting system or the power supply control unit of said system is configured to determine at least one parameter of a constant current expected to circulate in the serial circuit and expected to be supplied by the constant current regulator, said parameter being based on the expected power demand of the serial circuit;• the airfield ground lighting system or the power supply control unit of said system is configured to coordinate at least one of:- a modification of a light intensity level output applied to the at least one, in particular each light unit to match the expected light intensity level output to be applied, to at least one, in particular each light unit, preferably said modification being referred as light intensity level output modification and / or- -an activation or deactivation of the at least one activatable device of the at least one, in particular each light unit, preferably said activation or deactivation being referred as activatable device activation or deactivation, in coordination with an adjustment of the constant current circulating in the serial circuit to match the at least one parameter of a constant current expected to circulate in the serial circuit and expected to be supplied by the constant current regulator, preferably said adjustment being referred as constant current adjustment;• either:- at least one of the light intensity level output modification and / or the activatable device activation or deactivation is first performed and then the constant current adjustment is performed, or- the constant current adjustment is performed first and then at least one of the light intensity level output modification and / or the activatable device activation or deactivation is performed, preferably said adjustment corresponding a constant current intensity level increase or decrease and / or said modification corresponding a light intensity level output increase or decrease;• the airfield ground lighting system is configured to determine a first starting and / or ending point for starting and / or ending at least one of the light intensity level output modification and / or the activatable device activation or deactivation, and / or a second starting and / or ending point for starting and / or ending the constant current adjustment;• the at least one activatable device comprises at least one of at least one further light source, one or more sensors, and / or a heating kit;• the at least one sensed characteristic of an environment of the serial circuit is one or more of visibility condition, temperature and / or humidity;• the airfield ground lighting system is configured to transmit a given light intensity level output and / or a given activation or deactivation state of the at least one activatable device to at least one, in particular each one, of the plurality of light units as a control signal, via wireless and / or wired communication, such as wired communication via the serial circuit and wherein the at least one, in particular, each light unit comprises least one light source and said light unit is configured to extract the light intensity level output from the control signal as received and to control with the light intensity level output received the brightness of the least one light source, preferably wherein the airfield ground lighting system is configured such as when the control signal is extracted in the at least one, in particular each light unit, the extraction of data associated to the light intensity level output is performed without measuring a parameter representing an active current or a Root Mean Square current of the constant current circulating in the serial circuit;• the airfield ground lighting system is configured to determine the at least one parameter of a constant current expected to circulate in the serial circuit with an objective to minimize the power losses in the power lines of the serial circuit, while at least one attribute of one or more of the constant current regulator, the plurality of light units or the serial circuit, such as at least one of a minimal voltage, a maximum voltage, a minimal current and / or a maximal power, remain(s) in the predefined operating ranges of one or more of the constant current regulator, the plurality of light units or the serial circuit;• the at least one parameter of a constant current expected to circulate in the serial circuit comprises or consists in a constant current intensity level, in particular an active current or a Root Mean Square current, preferably said active current or Root Mean Square current not exceeding 2.6 A, in particular not exceeding 2 A, in operation;• the at least one parameter of a constant current expected to circulate in the serial circuit further comprises at least one control waveform parameter, in particular, at least one pulse width modulation control parameter;• the airfield ground lighting system is configured so that when the constant current intensity level of the constant current level expected to circulate in the serialcircuit and expected to be supplied by the constant current regulator is below a certain threshold, the airfield ground lighting system or a power supply control unit of said system is configured to modulate a constant current to circulate in the serial circuit, with waveform having a frequency from 3 to 10 Hz, a duty cycle between 40 to 60% and a current amplification factor inversely proportional to the duty cycle, wherein the at least one pulse width modulation control parameter comprises at least one of the frequency, the duty cycle, and / or the current amplification factor;• light intensity level output values comprise continuous levels or are discretized in a series a plurality of light intensity level outputs, in particular with at least 20 discrete levels, preferably at least 50 discrete levels, more preferably at least 100 discrete levels, in particular preferably at least 200 discrete levels;• an expected or the actual power demand of at least one, in particular, each one of the plurality of light units is transmitted by said light or determined by the airfield ground lighting system or the power supply control unit, and wherein the expected or actual power demand of the serial circuit is based on an aggregation of the expected or actual power demand of each one of the plurality of light units or an extrapolation of the expected or actual power demand of at least one of the plurality of light units;• The airfield ground lighting system is configured to determine or detect a desired operating mode selected from:- - a first mode of operation as defined in any one of the preceding features taken alone or in combination, and- - a second mode of operation, wherein when the second mode of operation is selected, the airfield ground lighting system or the power supply control unit is configured to determine the active current or the Root Mean Square current of the constant current to circulate in the serial circuit as a function of the light intensity level output to be applied, wherein the at least one, in particular, each light unit is configured to measure said current circulating in said serial circuit and to determine from said current as measured, the light intensity level output to control the brightness of the at least one, in particular each light unit, using an inverse of the function, wherein the function is defined by predefined graph data, preferably the airfield ground lighting system or the power supply control unit being configured to communicate the predefined graph data to the constant current regulator unit and / or the plurality of light units, preferably wherein thepredefined graph data comprise a plurality of constant current levels associated with a plurality of reference light intensity level outputs of the plurality of light units, and wherein at least some of the reference light intensity level outputs coincide with at least some of the light intensity level outputs.• the airfield ground lighting system is configured to determine or detect a desired operating mode selected from:- a first mode of operation, preferably referred as energy saving and adaptative mode, and- a second mode of operation, preferably referred as traditional mode, wherein the airfield ground lighting system is configured so that:- when the first mode of operation is selected, the at least one parameter of a constant current expected to circulate in the serial circuit and expected to be supplied by the constant current regulator is determined by said system or the power supply control unit of said system in such a manner that said parameter is based on the expected power demand of the serial circuit, wherein the airfield ground lighting system is configured to transmit a given light intensity level output to at least one, in particular each one, of the plurality of light units as a control signal, via wireless and / or wired communication, such as wired communication via the serial circuit and wherein the at least one, in particular, each light unit comprises least one light source and said light unit is configured to extract the light intensity level output from the control signal as received and to control with the light intensity level output received the brightness of the least one light source, preferably wherein the airfield ground lighting system is configured such as when the control signal is extracted in the at least one, in particular each light unit, the extraction of data associated to the light intensity level output is performed without measuring a parameter representing an active current or a Root Mean Square current of the constant current circulating in the serial circuit and- when the second mode of operation is selected, the airfield ground lighting system or the power supply control unit is configured to determine the active current or the Root Mean Square current of the constant current to circulate in the serial circuit as a function of the light intensity level output to be applied, wherein the at least one, in particular, each light unit is configured to measure said current circulating in said serial circuit andto determine from said current as measured, the light intensity level output to control the brightness of the at least one, in particular each light unit, using an inverse of the function, wherein the function is defined by predefined graph data, preferably the airfield ground lighting system or the power supply control unit being configured to communicate the predefined graph data to the constant current regulator unit and / or the plurality of light units, preferably wherein the predefined graph data comprise a plurality of constant current levels associated with a plurality of reference light intensity level outputs of the plurality of light units, and wherein at least some of the reference light intensity level outputs coincide with at least some of the light intensity level outputs.

[0005] One advantage of such an AGL system, is that since the Airfield ground lighting system defines a minimized current intensity level for an equal light intensity level (of a same light color) compared to the conventional dimming curve (defined as the traditional dimming curve), resistive losses in the power lines can be minimized. However, most airport authorities do not have yet the infrastructure to cope with a mode of operation defined in the claims, also denoted dynamic mode as it allows frequent changes in the power setting of the serial current circuit so that the current consumption is adapted to match changes in the airfield environment.

[0006] Advantageously, the AGL system according to the invention can be adapted to be capable of being operated in an operational mode adapted for the traditional dimming curve, for backward compatibility purposes. Indeed, the AGL system can operate with a standard dimming (second mode) before switching in the future to a power-efficient system according to a dynamic mode (the first mode), when the infrastructure is adapted. The AGL system can also be configured to operate only in the first mode when deployed on a new airport or a new airport section compatible with the AGL system operating under the first mode. In this case, an operation mode selection logic to switch from the second mode to the first mode, and eventually vice versa, is not needed. This simplifies the design of said AGL system, as the AGL system will advantageously operate permanently in the first mode.

[0007] Preferably, the AGL system is also capable of operating with a modified traditional dimming curve (third mode) characterized in that the current intensity supplied is lower than that required for the standard dimming (second mode) curve while ensuring the same equal light intensity levels.

[0008] The dynamic mode ensures that the load / power demand is met in real-time (e.g., to cope with weather conditions change) and the voltage at the secondaryend of the circuit remains within acceptable boundaries. As a result, energy efficiency can be increased while maintaining all existing functionality and performance of the AGL system. Hence, a more efficient and adaptable AGL system is obtained over a long period, warrantying a return on investment for the users.

[0009] Advantageously, in the dynamic mode, a constant current level to be supplied by the constant current regulator in the serial circuit of the airfield ground lights is determined with the objective of minimizing the power loss in the power lines of the serial circuit. The constant current intensity can be determined by a control logic as a function one or more of the following parameters :- the (expected) light intensity level output and at least attribute of the constant current regulator unit or serial circuit, such as maximum power, a minimum / maximum voltage and / or minimum current;- at least one attribute of the plurality of light units such as an (expected) activation / deactivation state of the active light sources and / or (expected) activation / deactivation of the heating kit, an (expected) power consumption one or more of the at least one light sources being in an active state, and / or an (expected) power consumption of the heating kit; and / or- at least one sensed characteristic of an environment of the serial circuit such as weather or visibility conditions, temperature and humidity.

[0010] Preferably, in the dynamic mode a control unit directly transmits the light intensity level output to the plurality of light units, by transmitting a control signal with embedded data associated with the light intensity level output to the plurality of light units, via wireless and / or wired communication. On the contrary, in the second or third mode, the light intensity level output is indirectly transmitted to the plurality of light units, as the light intensity level output is first transposed into a current intensity level and then the plurality of light units are capable to deduce from the measurement of the current intensity level, the light intensity level to be set in the plurality of lights. Thanks to the measure of the invention according to the dynamic mode, it is possible to decouple the light intensity level control from the constant current intensity control (compared to the traditional dimming curve characterized by an entanglement of the light intensity level and the constant current intensity), thereby permitting a fine (e.g. with a larger number of discrete light intensity discrete levels) and real-time control of the light units, with a lower power consumption.

[0011] Advantageously, a control signal determined by the control until is transmitted to the plurality of light units via cables or wires (e.g., power line), and / or wirelessly. The control signal can take the form of a modulation control signal, afrequency shift keying control signal, an orthogonal frequency division multiplexing control signal, a spread spectrum control signal or a duty cycle control signal such as frequency-based control or a pulse width control. The possibilities to be used are not limited to this list.Brief description of the drawings

[0012] Aspects of the invention will now be described in more detail with reference to the appended drawings, wherein same reference numerals illustrate same features and wherein:

[0013] Figure 1 represents a diagram of an AGL system;

[0014] Figure 2 represents a diagram of an AGL light;

[0015] Figure 3 represents how the constant current level to circulate in the dynamic mode is set as a function of the power demand.

[0016] Figure 4 represents dimming curve boundaries according to theFederal Aviation Administration.

[0017] Figure 5 represents a diagram with both a ’’traditional” dimming curve (with the substantially exponential relation) and a vertical control curve (vertical straight line) defined for a given current level associated with a discrete number of brightness levels.

[0018] Figure 6 represents a diagram with both a ’’traditional” dimming curve (with the substantially exponential relation) and two vertical control curves (vertical straight lines) each defined for a given current level with a discrete number of brightness levels according to the invention.

[0019] Figure 7 represents a diagram with both a ’’traditional” dimming curve (with the substantially exponential relation) and a series of stacked parallel horizontal segments defined for a continuous range of currents and a discrete number of brightness levels according to the invention.

[0020] Figure 8 represents a diagram with both a ’’traditional” dimming curve (with a substantially exponential relation) and a rectangular operating zone defined by a continuous range of currents in combination with a continuous range of brightness according to the invention.

[0021] Figure 9 illustrates a diagram in which a first switching scenario reduces a light intensity command from XMto XN.

[0022] Figure 10 illustrates a diagram in which a second switching scenario increases a light intensity command from XNto XM.

[0023] Figure 11 illustrates a diagram in which a third switching scenario in which the heater of the light units is turned on.

[0024] Figure 12 illustrates a diagram showing a “traditional” current evolution without PWM control.

[0025] Figure 13 illustrates a diagram showing a current evolution withPWM control.Detailed description

[0026] Referring to Figure 1 , an AGL system 10 comprises a plurality ofAGL lights 11 powered by a power supply 12. The AGL lights 1 1 are connected in series in a serial circuit 13 which forms a current loop that includes the power supply 12. The power supply 12 is hence connected to the serial circuit 13 to supply the AGL lights 11 with electric power, in particular AC power. Specifically, the power supply 12 comprises or consists of a constant current regulator (CCR) unit 121 that is configured to supply electric power to the serial circuit 13 in a constant current mode. In addition, the power supply 12 can comprise suitable converter circuitry configured to interface between a mains supply and the constant current regulator unit. The AGL system can comprise multiple power supplies 12, each connected to corresponding circuits of AGL lights 1 1. A single power supply 12 can be connected to a serial circuit 13, which can be extended or reduced by adding or removing serial circuit segments to it (via a circuit selector).

[0027] Referring to Figure 2, the AGL lights 1 1 comprise a light fixture 11 1 which is advantageously connected to the serial circuit 13 via an isolating transformer 112, as known in the art. Each light fixture 11 1 can be connected to the circuit 13 through an associated isolating transformer 1 12. Alternatively, multiple light fixtures may be connected to a single isolating transformer to receive power from the circuit 13. The light fixture 11 1 can be any type of airfield ground lighting, such as an inset light, an elevated light or a light sign. The AGL lights 11 can additionally be installed at any suitable location on the airfield, such as a runway, a taxiway, or the Apron.

[0028] The light fixture 111 can comprise a housing 1 17 accommodating a light source 114, such as a LED light source, and possibly one or more sensors 115 configured to measure attributes of the light source 1 14, such as (light) intensity, current and the like, and / or to measure attributes of the environment, such as vibration intensity, temperature, humidity. In addition, or alternatively, the one or more sensors 115 can be configured to detect (an attribute of) a foreign object in proximity of the light fixture 11 1 , such as presence or absence, position and / or distance, speed, etc. The light fixture 11 1 can further comprise a heating kit 116 configured to heat up parts of the light fixture 11 1 , particularly in proximity of light egression openings of the light fixture, particularly duringwinter conditions. It will be appreciated that the light source 1 14 can be configured to emit in the visible and / or invisible light range, such as infrared.

[0029] The light fixture 11 1 can comprise a control unit 113 configured to operate the light source 1 14 and possibly the one or more sensors 115 and / or heating kit 116. To this end, the control unit 1 13 can be connected to a secondary winding of the isolating transformer 1 12 to receive power which can be converted through suitable converter circuitry (e.g., included in control unit 1 13) and supplied to the light source 1 14 and possibly one or more sensors 1 15 and / or heating kit 116. Control unit 113 can be configured to receive operating commands for operating the various components such as the light source 114, the sensors 1 15 and / or the heating kit 116. Such operating commands may be individual for each light 11 or for a group of lights and can be received via the serial circuit 13 as known in the art, e.g., operating commands (e.g. light intensity level output) are communicated via a message signal via serial circuit 13. In particular, message signals are superimposed on the AC (50 Hz or 60 Hz) voltage or current signal fed via the serial circuit 13. In some examples, the message signal can be superimposed as an orthogonal frequency division multiplexing (OFDM) signal, which can comprise one or more non-overlapping narrowband and possibly parameterized frequency channels, advantageously in a frequency range between 20 and 190 kHz. Alternatively, the message signal can be superimposed by time slot synchronization and using a controlled high impedance at the secondary side of the transformers 112 for communicating pulses contained in pulse signals, as described in WO 95 / 24820. It will be appreciated that yet alternative power line communication techniques as known in the art may be used in the systems described herein, in particular frequency modulation schemes for data communication, such as frequency-shift keying (FSK) signals transmitted via the serial circuit 13, i.e., the power supply line. In addition, or alternatively, the operating commands can be received by the control unit 1 13 wirelessly, e.g., via a wireless receiver integrated in the AGL light.

[0030] One or more sensors 115 can be configured to monitor the light source 114, e.g. the light output, and feed a control signal to the control unit 1 13 which can be configured to control the light source 114 based on the control signal. The operating commands received by the control unit 113 can be individual commands to control light sources individually, or general commands to control multiple or all light sources along the serial circuit 13.

[0031] It will be appreciated that the isolating transformer 1 12 can be accommodated at least in part in the housing 1 17, or alternatively completely outside of the housing 1 17, as shown in Figure 2. The isolating transformer 112 can have atransformer ratio which is typically 1 :1 , or which alternatively may be different from 1 :1 to provide for current transformation between the primary and secondary sides. It will be appreciated that the transformer ratio can be same or different for transformers connected in the serial circuit 13. This allows lights of different kind (e.g., different manufacturer) to be installed in the serial circuit 13.

[0032] Referring again to Figure 1 , the operating commands (e.g., light intensity level output) for the control units of the various AGL lights 11 can be superimposed on the power signal by the power supply 12. Power supply 12 can be connected to a control unit 14 via a data communication line 142 which can be wired or wireless. Control unit 14 can be configured to generate operating commands for the light fixtures, e.g., for the control units 1 13 of the light fixtures and / or to generate operating commands for the power supply 12 and to transmit them to the corresponding power supply 12. In this case, the control unit 14 is also denoted power supply control unit. The control unit 14 can be configured to receive external control commands, e.g., from a control tower 9, via one or more data communication lines 141 , and to generate the operating commands for the power supply 12 and / or the operating commands (e.g., light intensity level output) the AGL lights 11 based on the external control commands.

[0033] Traditionally, in a constant current circuit, the brightness level, i.e., the intensity, of the light emitted by the light source 1 14 is defined by a current level that is fed through the serial circuit 13 (second or third mode). A higher current level indicates a higher brightness level that must be output by the light sources. It will be appreciated that the light source can be configured to emit light in the visible and / or invisible range. As a result, a brightness level in the present context refers to an intensity of electromagnetic radiation output by the light source 114, such as a luminous intensity.

[0034] The AGL system according to the invention can be configured to switch from the dynamic mode of operation (based on the power demand approach with power loss minimization) to the second / third mode of operation, namely the traditional / standard control, where a so-called modified / traditional dimming curves ( traditional dimming curve being illustrated in Figures 5-8) is applied. Thanks to this measure, the AGL system can already be applied in most airports where, the infrastructure is optimized for the standard protocol (second mode of operation) before switching to a more effective protocol, namely the dynamic operating mode when the infrastructure is upgraded. If needed, the third mode of operation being an extension of the second can already be used (especially when weather conditions are fine) in most airports without undue effort, to reduce power loss, while waiting for a switch to the dynamic mode.

[0035] Referring to Figures 5-8, so-called “traditional” dimming curves 20 are defined by aviation authorities, such as the International Civil Aviation Organisation (ICAO) and the Federal Aviation Administration (FAA) for LED and other light sources. All these dimming curves include a maximum current level Amax, typically 6.6 A, corresponding with a maximum brightness level Xmax output by the light source, e.g., Xmax= 100% brightness. In addition, a minimum current level Ao can be defined, e.g., 2.8 A, corresponding with a minimum brightness level Xo(typically between 0% and 1%, e.g., 0.15%) output by the light source 114. Typically, when the current level in the serial circuit 13 is at or below the minimum current level Ao, no light is output by the light source, which may be turned OFF. The dimming curve 20 can define one or more intermediate current levels Ai,i=i n, n < 1 , Ao< A < Amaxcorresponding with intermediate brightness levels Xi,i=i n, Xo < X < Xmax. The number n of intermediate levels can be between 1 and 8, advantageously between 2 and 6, e.g., 3 to reach a 5-step brightness level increase from Xoto Xmax(100%). It will be appreciated that tolerance levels can be associated with the various current levels Ao, Ai;Amax, e.g., to account for hysteresis effects.

[0036] Such a dimming curve is typically defined for brightness levels for incandescent lights, which have a continuous relation (e.g., exponential relation) between the applied current level and brightness output. LED light sources naturally have a more linear relation between the applied current level and brightness output. In AGL systems, the control unit 113 of the LED light source 1 14 is configured to mimic the performance of incandescent light such that the brightness level output is within a minimum / maximum range of the output of an incandescent light for a given current level. As a result, the current level of a conventional dimming curve for LED lights is typically defined in five monotonically increasing steps as indicated in Table 1 . A dimming curve, according to the Federal Aviation Administration, is a continuous function (bijective and monotonic), where a change in intensity corresponds to a change in current, with minimal and maximal light output for a given current. This is illustrated in Figure 4, where the boundaries (minimum and maximum brightness levels, expressed as a percentage) are shown as a function of the current intensity.Table 1 : Approximate dimming curve values for conventional (6.6A) operation according to ICAOAerodrome Design Manual, Document 9157, 2ndEdition, 2017, Part 5, Chapter 12.9

[0037] The control unit 14 can be configured to receive a brightness level set point for the AGL lights 1 1 of the serial circuit 13 as a control command, e.g. by the control tower 9 and to translate the brightness level set point to a current level A based on the dimming curve 20, e.g. based on Table 1 . The current level Ai is communicated to the respective CCR unit 121 which sets the current level on the serial circuit 13 to the communicated current level.

[0038] The control unit 113 of the individual AGL lights 11 can be configured to sense the current level Ai through the serial circuit 13 and to translate the sensed current level to a brightness level Xi. The control unit 1 13 can e.g., be implemented with a logic configured to translate the current level A to a corresponding brightness level Xi based on the dimming curve 20, e.g., via a lookup table that implements the dimming curve 20 (e.g., Table 1 ) and which can be stored in a memory module of control unit 113. The control unit 113 is configured to drive the light source 114 so as to output the brightness level . The lookup table and / or dimming curve 20 can form the predefined graph data.

[0039] Alternatively, under the dynamic mode of operation, the constant current value (e.g. Root Mean Square current or active current) to be supplied by a constant current regulator in the serial circuit 13 is based on the power demand of the plurality of light units 11 and preferably at least one attribute of the constant current regulator unit 121 . A suitable constant current intensity value Itarget is selected to minimize the power loss in the power lines of the serial circuit 13, while the at least one attribute of the constant current regulator unit and / or the serial circuit, such at maximal power (not illustrated in Figure 3), minimum voltage (not illustrated in Figure 3) maximum voltage Vmax and / or minimum current Imin remains in the operating ranges of the constant current regulator 121 and / or serial circuit 13. In other words, the intensity of the current circulating in the power line is reduced up to the point where the tension reaches or is near the maximum voltage allowable Vmax and / or current reaches or is near a minimum current Imin operating threshold as illustrated in Figure 3, which demonstrates that theconstant current set to circulate Itarget as determined by the first mode (dynamic mode) is well below the predefined current Ai (Xi) as determined with the standard (a.k.a. traditional) dimming curve (second mode 2) for a given light intensity level output .

[0040] In an embodiment, a dedicated control unit 14 of the AGL system or the control unit embedded in the constant current regulator unit 121 can determine the optimized characteristics of the current to circulate in the serial circuit 13. The dedicated control unit of the AGL system 14, the control unit of the constant current regulator unit 121 , or alternative thereof, are also designated as the power supply control unit. The power supply control unit is configured to centralize the feedback of the power demand of all connected light units 11 and eventually other elements belonging to the circuit. Based on this demand, the power supply control unit can predict a current to be supplied by the constant current regulator unit 121 in a way that energy consumption is optimized while ensuring that operational boundaries are not breached (e.g. the tension to be provided by the constant current regulator unit 121 does not violate safety requirement, e.g. Safety Extra-Low Voltage (SELV)). Indeed, with a lower current and the same power demand the voltage is increased, reducing the Ohm losses. However, SELV requirements limit the maximal allowed voltage on a light. Therefore the cumulative voltage of the lights disposed in series, at the ports of the constant current regulator unit 121 is limited.

[0041] Preferably, a computed target value of the current determined by the power supply control unit is used as an input to control the constant current regulator unit 121 . The target value of the current can also be defined in the form of an equivalent light intensity level output or step according to the standard dimming curve as defined in Table 1 or Figure 4.

[0042] With the measures of the present invention, the power supply control unit (e.g. control unit 14) can also ensure a discrete control or seamless control of the brightness based on commands sent from a control tower 9, via one or more data communication lines 141. Traditionally, 5 steps are used for the control (see Table 1 ).

[0043] To ensure a finer control, the number of brightness steps can be increased. Equally, as the number of brightness levels is not coupled to the number of current intensity levels with the dynamic mode, the number of current intensity levels can be increased independently from the number of brightness levels, and vice versa. With a larger number of current intensity levels, the serial circuit 13 can be operated in such a manner to reach an operating region suitable to reduce Ohm losses.

[0044] However, an increase in the number of brightness levels can be restricted by the communication bandwidth in case the control signal is transmitted viathe power line. With a power line communication, a selection of around 20 steps appears to be a compromise between bandwidth limitation and power consumption optimization.

[0045] Figure 5 shows a diagram comprising a “traditional” dimming curve and a “vertical” control curve with a straight line defined for a given current level with a discrete number of brightness intensity level outputs. The number of brightness intensity level outputs is increased compared to the standard curve. The current level is selected to operate in a low current zone.

[0046] Figure 6 differs from Figure 5 in that two “vertical” control curves can be selected depending on the power demand need. In particular, when the power demand is high because of a need for the activation of the heaters, the “vertical” curve defined for the higher current is selected.

[0047] Figure 7 differs from Figure 6 in that the current level can be selected in a continuous range of current values instead of a discrete range, allowing better control and reaching low consumption region. By "continuous" we mean that the number of levels is so high that it is almost continuous.

[0048] Figure 8 differs from Figure 7 in that the brightness level can be selected in an (almost) continuous range instead of a discrete range. This approach allows finer control but requires sufficient bandwidth. Typically, wireless communication is preferred for such an approach. Moreover, the outer contour of the operating range can be non-rectangular to avoid certain zones where the efficiency or stability of the circuit is suboptimal.

[0049] The power supply control unit can also be configured to determine the optimal timing for a power adjustment of the constant current regulator and a command to the lights to switch brightness intensity, to prevent an unsatisfactory functioning with underpowered light units.

[0050] Figure 9 illustrates a first switching scenario in which a light intensity command is reduced, for instance after receiving a command from the control tower. The power supply control unit sends a light intensity command to the light units first, and once the circuit is stable the power supply control unit reduces the current supplied by the constant current regulator.

[0051] Figure 10 illustrates a second switching scenario in which the light intensity command is increased, for instance after receiving a command from the control tower. The power supply control unit first sends a command to increase the current, before sending out a command to increase the light intensity level output.

[0052] Figure 11 illustrates a third switching scenario in which a request to turn on the heater of the light units is present, for instance after the detection of freezingweather conditions. The power supply control unit first sends a command to increase the current, before sending a command enabling the activation of the heaters.

[0053] Other switching scenarios can be adopted keeping in mind that they remain stable during the switching and the tension remains for instance in the Safety Extra-Low Voltage regulations. Thanks to the measure of the invention, in particular, a coordinate control of the light intensity and the current commands allows to optimise a transition from one operating point to another.

[0054] The power supply control unit can also include learning and prediction measures. The power supply control unit learns from the power demand in the field (reported back from the lights) and optimizes the current switching of the regulator in real-time. For instance, Al algorithms can also be adapted to: cold start conditions, environmental requirements and / or defects of lights, which change the circuit characteristics. For this purpose, the power demand of the plurality of light units 1 1 as measured or estimated can compensated by a metric evaluated with light intensity level output and optionally sensed characteristics of an environment of the serial circuit, such as weather or visibility conditions, temperature and humidity. This approach allows for countering individual defects. This metric can be constantly upgraded using a learning method. Indeed, at least one parameter of the metric can be modified using a learning algorithm, wherein the predicted power demand with the metric is compared to the power demand consumed, in relation to the at least one sensed characteristic of an environment.

[0055] The expected or actual power demand of the plurality of light units11 can also be based on the consumption of at least one primary light source and one or more activatable devices 1 14, 1 16, 115 preferably selected from the group comprising : at least one secondary light source in case of a light engine (e.g. Approach lighting system or Precision Approach Path Indicator), one or more sensors 115 and a heating kit 116. The actual power consumption can be measured directly in each one of the light units 11. Alternatively, or complementary to, the expected power consumption can be estimated, for instance for each one of the light source(s) 114, using the expected light intensity output value as an input for a light source power consumption model. Besides the expected light intensity, the expected number of activated activatable devices 1 14, 116, 115 is used to determine the expected power consumption. The power estimation model can be constantly upgraded using a learning method. The power consumption model can be fine-tuned by comparing the actual consumption with the estimated consumption, using a learning algorithm, in particular a Al algorithm. The actual power duty cycle in the light unit can also be used to determine the actual consumption of thelight source. By counting the power consumed by all activable devices within a given light unit 11 , and then by aggregating the corresponding consumption of a group of light units 1 1 , it is possible to determine the actual or expected power consumption of said group of light units 11 of interest. A precise knowledge of the powder needs allows to adjust precisely the current to be supplied to these light units 11 , to minimize Ohm’s losses, while warranting regular operations, for instance, within the constant current regulator specifications and SELV regulations.

[0056] Moreover, an expected power demand of the serial circuit 13 can also be based on an operating parameter from at least one, in particular each one, of the plurality of light units 1 1. Such an operating parameter can be selected from a group comprising a buffer voltage, a light source driver duty cycle or a temperature of the light unit. The operating parameter(s) can be determined in the light units using a sensor or estimated using a model. The data associated with these operating parameters can be transmitted by the light units 1 1 to the power supply control unit, preferably via wireless and / or wired communication, such as wired communication via the serial circuit 13. The knowledge of the operating parameters of the light units allows to define the powder needs better and consequently the current to be supplied to these light units.

[0057] The actual power demand of the plurality of light units can serve to monitor the current supply and take measures if necessary. For instance, in case the actual power consumption of a given light unit is close to its nominal value, the control unit is adapted to increase the power supply, in particular the current to ensure the proper functioning of the light units.

[0058] Alternatively, the power demand of the plurality of light units 11 can be based on a simplified metric evaluated with the light intensity level output and the sensed characteristic of an environment of the serial circuit, such as weather or visibility conditions, temperature and humidity. This approach relies on a model with a limited number of parameters to estimate the global power demand of the system, in contrast to the approach described in the previous paragraphs, where the expected power demands of each light or reference lights are summed or extrapolated to precisely determine the aggregated expected power consumption. This simplified model / metric can be constantly upgraded using learning methods. Indeed, at least one parameter of the metric can be modified using a learning algorithm, wherein the predicted power demand with the metric is compared to the power demand consumed, based on the at least one sensed characteristic of the environment of the serial circuit.

[0059] Advantageously, the power supply control unit can also calculate, in addition to a current intensity (e.g. Root Mean Square (RMS) current, in particular theactive current), a waveform control parameter such as a pulse width modulation parameter (PWM). The waveform control acts as an envelope over the alternating current circulating in the circuit with a frequency typically in the range of 50 and 60 Hz. Thanks to waveform control, the amplitude of the current can be increased as illustrated in Figure 13 which illustrates a current evolution with PWM control compared to Figure 12 which illustrates a current evolution without PWM control. This measure allows to further diminish the average current circulating in the circuit, when necessary, for instance when the power demand is low, while ensuring during the “on” state of PWM control that a higher current is present, so as to cope with a minimal charging current requirement of the transformer(s) of the constant current regulator CCR 121. Likewise, the frequency can also be modified as a function of the power demand.

[0060] Specific examples of suitable power line communication methods for communicating the light intensity level output are: a specific ON / OFF sequence of the input power of the AGL lights, which is recognized by the control units 113 as a control signal associated to light intensity level output ; a (temporary) change in the amplitude of the current level of serial circuit 13, e.g. via amplitude shift keying (ASK) or by maintaining a current in the serial circuit for a predetermined period at a predetermined current level representative of a specific operating mode; a (temporary) change in the frequency of the current level of serial circuit 13, e.g. frequency shift keying (FSK); a change in the shape of the current of the serial circuit 13, e.g., through addition of one or more harmonics.

[0061] The communication can be performed through a bidirectional communication method with the AGL lights 11 , or through a unidirectional communication method, or a broadcast method. In

[0062] Alternatively, the communication data be transmitted to the AGL lights through a data communication cable, such as an optical fibre, or wirelessly, e.g., cellular communication technology (such as 5G) or Ultra-Wide Band (UWB).

[0063] Advantageously, the mode selection between the dynamic mode and the second mode (with the traditional dimming curve) and optionally the third mode (with the modified traditional dimming curve) can be performed in the control tower via manual input. The mode selection can be first sent to the power supply control unit and then to the lights. Alternatively, the AGL lights 11 can be provided with a configurabledevice, e.g., a switch, configured to pre-set the mode of operation at the time of installation.

[0064] In particular, embodiments as discussed above are defined by the following numbered clauses:Clause A1 . Airfield ground lighting system (10), comprising: a plurality of light units (11 ) arranged in a serial circuit (13), a power supply (12) adapted to supply the plurality of light units (1 1 ) with power in the form of a constant current circulating in the serial circuit (13), said power supply (12) comprising or consisting of a constant current regulator (121 ); wherein each light unit (11 ) comprises at least one light source (114) and optionally at least one activatable device (114, 116, 115); wherein the airfield ground lighting system (10) or a power supply control unit (14) of said system (10) is configured to determine an expected power demand of the serial circuit (13) based on at least one of an expected light intensity level output to be applied, to at least one, in particular each light unit (11 ) and / or an expected activation state of the at least one activatable device of said light unit (1 1 ), and optionally at least one sensed characteristic of an environment of the serial circuit (13) and optionally an actual power absorbed by the serial circuit (13) or at least one, in particular each one, of the plurality of light units (1 1 ).Clause A2. Airfield ground lighting system (10) according to clause A1 , wherein the airfield ground lighting system (10) or the power supply control unit (14) of said system (10) is configured to determine at least one parameter of a constant current expected to circulate in the serial circuit (13) and expected to be supplied by the constant current regulator (121 ), said parameter being based on the expected power demand of the serial circuit (13).Clause A3. Airfield ground lighting system (10) according to clause A2, wherein the airfield ground lighting system (10) or the power supply control unit of said system is configured to coordinate at least one of:- a modification of a light intensity level output applied to the at least one, in particular each light unit (1 1 ) to match the expected light intensity level output to be applied, to at least one, in particular each light unit (11 ), preferably said modification being referred as light intensity level output modification and / or -an activation or deactivation of the at least one activatable device (1 14, 1 16, 115) of the at least one, in particular each light unit (11 ), preferably said activation or deactivation being referred as activatable device activation or deactivation,in coordination with an adjustment of the constant current circulating in the serial circuit (13) to match the at least one parameter of a constant current expected to circulate in the serial circuit (13) and expected to be supplied by the constant current regulator (121 ), preferably said adjustment being referred as constant current adjustment.Clause A4. Airfield ground lighting system (10) according to clause A3, wherein either:- at least one of the light intensity level output modification and / or the activatable device activation or deactivation is first performed and then the constant current adjustment is performed, or- the constant current adjustment is performed first and then at least one of the light intensity level output modification and / or the activatable device activation or deactivation is performed, preferably said adjustment corresponding a constant current intensity level increase or decrease and / or said modification corresponding a light intensity level output increase or decrease.Clause A5. Airfield ground lighting system (10) according to any one of Clauses A3 to A4, wherein the airfield ground lighting system (10) is configured to determine a first starting and / or ending point for starting and / or ending at least one of the light intensity level output modification and / or the activatable device activation or deactivation, and / or a second starting and / or ending point for starting and / or ending the constant current adjustment.Clause A6. Airfield ground lighting system (10) according to any one of clauses A1 to A5, wherein the at least one activatable device (114, 116, 115) comprises at least one of at least one further light source (1 14), one or more sensors (1 15), and / or a heating kit (116).Clause A7. Airfield ground lighting system (10) according to any of clauses A1 to A6, wherein the at least one sensed characteristic of an environment of the serial circuit is one or more of visibility condition, temperature and / or humidity.Clause A8. Airfield ground lighting system (10) according to any of clauses A1 to A7, wherein the airfield ground lighting system (10) is configured to transmit a given light intensity level output and / or a given activation or deactivation state of the at least one activatable device to at least one, in particular each one, of the plurality of light units (1 1 ) as a control signal, via wireless and / or wired communication, such as wired communication via the serial circuit and wherein the at least one, in particular, each light unit (1 1 ) comprises least one light source (114) and said light unit (11 ) is configured to extract the light intensity level output from the control signal as received and to controlwith the light intensity level output received the brightness of the least one light source (1 14), preferably wherein the AGL system (10) is configured such as when the control signal is extracted in the at least one, in particular each light unit (11 ), the extraction of data associated to the light intensity level output is performed without measuring a parameter representing an active current or a Root Mean Square current of the constant current circulating in the serial circuit (13).Clause A9. Airfield ground lighting system (10) according to clause A2 or any one of clauses A3 to A8 in combination with clause A2, wherein the airfield ground lighting system (10) is configured to determine the at least one parameter of a constant current expected to circulate in the serial circuit (13) with an objective to minimize the power losses in the power lines of the serial circuit (13), while at least one attribute of one or more of the constant current regulator (121 ), the plurality of light units (1 1 ) or the serial circuit (13), such as at least one of a minimal voltage, a maximum voltage, a minimal current and / or a maximal power, remain(s) in the predefined operating ranges of one or more of the constant current regulator (121 ), the plurality of light units or the serial circuit (13).Clause A10. Airfield ground lighting system (10) according to clause A2 or any one of clauses A3 to A9 in combination with clause A2, wherein the at least one parameter of a constant current expected to circulate in the serial circuit (13) comprises or consists in a constant current intensity level, in particular an active current or a Root Mean Square current, preferably said active current or Root Mean Square current not exceeding 2.6 A, in particular not exceeding 2 A, in operation.Clause A11. Airfield ground lighting system (10) according to clause A2 or any one of clauses A3 to A10 in combination with clause 2, wherein the at least one parameter of a constant current expected to circulate in the serial circuit (13) further comprises at least one control waveform parameter, in particular, at least one pulse width modulation control parameter.Clause A12. Airfield ground lighting system (10) according to clause A10 in combination with clause A11 , wherein the airfield ground lighting system (10) is configured so that when the constant current intensity level of the constant current level expected to circulate in the serial circuit (13) and expected to be supplied by the constant current regulator (121 ) is below a certain threshold, the airfield ground lighting system (10) or a power supply control unit (14) of said system (10) is configured to modulate a constant current to circulate in the serial circuit (13), with waveform having a frequency from 3 to 10 Hz, a duty cycle between 40 to 60% and a current amplification factor inversely proportional to the duty cycle, wherein the at least one pulse widthmodulation control parameter comprises at least one of the frequency, the duty cycle, and / or the current amplification factor.Clause A13. Airfield ground lighting system (10) according to any one of clauses A1 to A12, wherein light intensity level output values comprise continuous levels or are discretized in a series a plurality of light intensity level outputs (Xi,0, Xu, X2,max), in particular with at least 20 discrete levels, preferably at least 50 discrete levels, more preferably at least 100 discrete levels, in particular preferably at least 200 discrete levels.Clause A14. Airfield ground lighting system (10) according to any one of clauses A1 to A13, wherein an expected or the actual power demand of at least one, in particular, each one of the plurality of light units (11 ) is transmitted by said light (1 1 ) or determined by the airfield ground lighting system (10) or the power supply control unit (14), and wherein the expected or actual power demand of the serial circuit (13) is based on an aggregation of the expected or actual power demand of each one of the plurality of light units (11 ) or an extrapolation of the expected or actual power demand of at least one of the plurality of light units (11 ).Clause A15. Airfield ground lighting system (10) according to any one of clauses A3 to A7 or A9 to A14, wherein said system (10) is configured to determine or detect a desired operating mode selected from:- a first mode of operation, preferably referred as energy saving and adaptative mode,- a second mode of operation, preferably referred as traditional mode and wherein the airfield ground lighting system (10) is configured so that:- when the first mode of operation is selected, the at least one parameter of a constant current expected to circulate in the serial circuit (13) and expected to be supplied by the constant current regulator (121 ) is determined by said system (10) or the power supply control unit (14) of said system (10) in such a manner that said parameter is based on the expected power demand of the serial circuit (13), wherein the airfield ground lighting system (10) is configured to transmit a given light intensity level output to at least one, in particular each one, of the plurality of light units (1 1 ) as a control signal, via wireless and / or wired communication, such as wired communication via the serial circuit (13) and wherein the at least one, in particular, each light unit (1 1 ) comprises least one light source (1 14) and said light unit (11 ) is configured to extract the light intensity level output from the control signal as received and to control with the light intensity level output received the brightness of the least one light source (114), preferably wherein the airfield ground lighting system (10) is configured such as when the control signal is extracted in the at least one, in particular each light unit (1 1 ), the extraction of data associated to the lightintensity level output is performed without measuring a parameter representing an active current or a Root Mean Square current of the constant current circulating in the serial circuit (13), and-when the second mode of operation is selected, the airfield ground lighting system (10) or the power supply control unit (14) is configured to determine the active current or the Root Mean Square current of the constant current to circulate in the serial circuit (13) as a function (20) of the light intensity level output to be applied, wherein the at least one, in particular, each light unit (1 1 ) is configured to measure said current circulating in said serial circuit (13) and to determine from said current as measured, the light intensity level output to control the brightness of the at least one, in particular each light unit (1 1 ), using an inverse of the function, wherein the function (20) is defined by predefined graph data, preferably the airfield ground lighting system or the power supply control unit (14) being configured to communicate the predefined graph data to the constant current regulator unit (121 ) and / or the plurality of light units (1 1 ), preferably wherein the predefined graph data comprise a plurality of constant current levels (Ao, A, Amax) associated with a plurality of reference light intensity level outputs (X2,o, X2 i, X2,max) of the plurality of light units (11 ), and wherein at least some of the reference light intensity level outputs (X2,0, X2, X2,max) coincide with at least some of the light intensity level outputs (Xi,0, Xi , Xi,max).Clause A16. Airfield ground lighting system (10) according to any one of clauses A1 to A14, wherein said system (10) is configured to determine or detect a desired operating mode selected from:- a first mode of operation as defined in any one of clauses A2 to A14, and- a second mode of operation, wherein when the second mode of operation is selected, the airfield ground lighting system (10) or the power supply control unit (14) is configured to determine the active current or the Root Mean Square current of the constant current to circulate in the serial circuit (13) as a function (20) of the light intensity level output to be applied, wherein the at least one, in particular, each light unit (11 ) is configured to measure said current circulating in said serial circuit (13) and to determine from said current as measured, the light intensity level output to control the brightness of the at least one, in particular each light unit (11 ), using an inverse of the function, wherein the function (20) is defined by predefined graph data, preferably the airfield ground lighting system or the power supply control unit (14) being configured to communicate the predefined graph data to the constant current regulator unit (121 ) and / or the plurality of light units (11 ), preferably wherein the predefined graph data comprise a plurality of constant current levels (Ao, A,Amax) associated with a plurality of reference light intensity level outputs (X2,0, X2 i, X2,max) of the plurality of light units (1 1 ), and wherein at least some of the reference light intensity level outputs (X2,0, X2 i, X2,max) coincide with at least some of the light intensity level OUtputS (Xi ,0, Xi ,|, Xi .max).Clause B1. Airfield ground lighting system (10), comprising: a plurality of light units (11 ) arranged in a serial circuit (13), a power supply (12) adapted to supply the plurality of light units (1 1 ) with power in the form of a constant current circulating in the serial circuit (13), said power supply (12) comprising or consisting of a constant current regulator (121 ); wherein each light unit (11 ) comprises at least one light source (114) and optionally at least one activatable device (114, 116, 115); wherein the airfield ground lighting system (10) or a power supply control unit (14) of said system (10) is configured to determine an expected power demand of the serial circuit (13) based on at least one of an expected light intensity level output to be applied, to at least one, in particular each light unit (11 ) and / or an expected activation state of the at least one activatable device of said light unit (1 1 ), and optionally at least one sensed characteristic of an environment of the serial circuit (13) and optionally an actual power absorbed by the serial circuit (13) or at least one, in particular each one, of the plurality of light units (1 1 ).Clause B2. Airfield ground lighting system (10) according to clause B1 , wherein the airfield ground lighting system (10) or the power supply control unit (14) of said system (10) is configured to determine at least one parameter, in particular a first parameter and optionally at least one second parameter of a or the constant current expected to circulate in the serial circuit (13) and optionally expected to be supplied by the constant current regulator (121 ), said parameter being based on the expected power demand of the serial circuit (13).Clause B3. Airfield ground lighting system (10) according to clause B2, wherein the airfield ground lighting system (10) or the power supply control unit of said system is configured to coordinate at least one of:- a modification of a light intensity level output applied to the at least one, in particular each light unit (1 1 ) to match the expected light intensity level output to be applied, to at least one, in particular each light unit (11 ), said modification being referred as light intensity level output modification and / or-an activation or deactivation of the at least one activatable device (1 14, 1 16, 115) of the at least one, in particular each light unit (1 1 ), said activation or deactivation being referred as activatable device activation or deactivation,in coordination with an adjustment of the constant current circulating in the serial circuit (13) to match the at least one parameter of a constant current expected to circulate in the serial circuit (13) and expected to be supplied by the constant current regulator (121 ), said adjustment being referred as constant current adjustment.Clause B4. Airfield ground lighting system (10) according to clause B3, wherein either:- at least one of the light intensity level output modification and / or the activatable device activation or deactivation is first performed and then the constant current adjustment is performed, or- the constant current adjustment is performed first and then at least one of the light intensity level output modification and / or the activatable device activation or deactivation is performed, preferably wherein the light intensity level output modification is performed with a delay relative to the constant current adjustment, the delay being greater than 0.1 ms, preferably greater than 1 ms, but less than 500 ms, preferably said delay being selected to allow a stabilisation of the serial circuit (13) after the constant current adjustment, preferably said adjustment corresponding a constant current intensity level increase or decrease and / or said modification corresponding a light intensity level output increase or decrease.Clause B5. Airfield ground lighting system (10) according to any one of Clauses B3 to B4, wherein the airfield ground lighting system (10) is configured to determine a first starting and / or ending point for starting and / or ending at least one of the light intensity level output modification and / or the activatable device activation or deactivation, and / or a second starting and / or ending point for starting and / or ending the constant current adjustment, preferably wherein the first starting and / or ending point for starting and / or ending at least one of the light intensity level output modification and / or the activatable device activation or deactivation, and / or the second starting and / or ending point for starting and / or ending the constant current adjustment are temporally offset from one another, in particular said offset being greater than 0.1 ms, preferably greater than 1 ms, but less than 500 ms.Clause B6. Airfield ground lighting system (10) according to any one of clauses B1 to B5, wherein the at least one activatable device (114, 116, 115) comprises at least one of at least one further light source (1 14), one or more sensors (1 15), and / or a heating kit (116).Clause B7. Airfield ground lighting system (10) according to any of clauses B1 to B6, wherein the at least one sensed characteristic of an environment of the serial circuit is one or more of visibility condition, temperature and / or humidity.Clause B8. Airfield ground lighting system (10) according to any of clauses B1 to B7, wherein the airfield ground lighting system (10) is configured to transmit a given light intensity level output and / or a given activation or deactivation state of the at least one activatable device to at least one, in particular each one, of the plurality of light units (1 1 ) as a control signal, via wireless and / or wired communication, such as wired communication via the serial circuit and wherein the at least one, in particular, each light unit (1 1 ) comprises least one light source (114) and said light unit (11 ) is configured to extract the light intensity level output from the control signal as received and to control with the light intensity level output received the brightness of the least one light source (1 14).Clause B9. Airfield ground lighting system (10) according to clause B2 or any one of clauses B3 to B8 in combination with clause B2, wherein the airfield ground lighting system (10) is configured to determine the at least one parameter of a or the constant current expected to circulate in the serial circuit (13) and optionally expected to be supplied by the constant current regulator (121 ) with an objective to minimize the power losses in the power lines of the serial circuit (13), while at least one attribute of one or more of the constant current regulator (121 ), the plurality of light units (1 1 ) or the serial circuit (13), such as at least one of a minimal voltage, a maximum voltage, a minimal current and / or a maximal power, remain(s) in the predefined operating ranges of one or more of the constant current regulator (121 ), the plurality of light units (1 1 ) or the serial circuit (13).Clause B10. Airfield ground lighting system (10) according to clause B2 or any one of clauses B3 to B9 in combination with clause B2, wherein the at least one parameter, in particular the first parameter of a or the constant current expected to circulate in the serial circuit (13) and optionally expected to be supplied by the constant current regulator (121 ) comprises or consists in a constant current intensity level, in particular an active current or a Root Mean Square current, preferably said active current or Root Mean Square current not exceeding 2.6 A, in particular not exceeding 2 A, in operation.Clause B11. Airfield ground lighting system (10) according to clause B2 or any one of clauses B3 to B10 in combination with clause B2, wherein the at least one parameter of a or the constant current expected to circulate in the serial circuit (13) and optionally expected to be supplied by the constant current regulator (121 )further comprises at least one control waveform parameter, in particular, at least one pulse width modulation control parameter or wherein the at least second parameter of a or the constant current expected to circulate in the serial circuit (13) and optionally expected to be supplied by the constant current regulator (121 ) comprises or consists of at least one control waveform parameter, in particular at least one pulse width modulation control parameter.Clause B12. Airfield ground lighting system (10) according to clause B10 in combination with clause B11 , wherein the airfield ground lighting system(10) is configured so that when the constant current intensity level of the constant current level expected to circulate in the serial circuit (13) and optionally expected to be supplied by the constant current regulator (121 ) is below a certain threshold, the airfield ground lighting system (10) or a power supply control unit (14) of said system (10) is configured to modulate a constant current to circulate in the serial circuit (13), with waveform having a frequency from 3 to 10 Hz, a duty cycle between 40 to 60% and a current amplification factor inversely proportional to the duty cycle, wherein the at least one pulse width modulation control parameter comprises at least one of the frequency, the duty cycle, and / or the current amplification factor.Clause B13. Airfield ground lighting system (10) according to any one of clauses B1 to B12, wherein light intensity level output values comprise continuous levels or are discretized in a series a plurality of light intensity level outputs (Xi,0, Xu, X2,max), in particular with at least 20 discrete levels, preferably at least 50 discrete levels, more preferably at least 100 discrete levels, in particular preferably at least 200 discrete levels.Clause B14. Airfield ground lighting system (10) according to any one of clauses B1 to B13, wherein an expected or the actual power demand of at least one, in particular, each one of the plurality of light units (11 ) is transmitted by said light(1 1 ) or determined by the airfield ground lighting system (10) or the power supply control unit (14), and wherein the expected or actual power demand of the serial circuit (13) is based on an aggregation of the expected or actual power demand of each one of the plurality of light units (11 ) or an extrapolation of the expected or actual power demand of at least one of the plurality of light units (11 ).Clause B15. Airfield ground lighting system (10) according to any one of clauses B1 to B14, wherein said system (10) is configured to determine or detect a desired operating mode selected from:- a first mode of operation as defined in any one of clauses B2 to B14, and- a second mode of operation,wherein when the second mode of operation is selected, the airfield ground lighting system (10) or the power supply control unit (14) is configured to determine the active current or the Root Mean Square current of the constant current to circulate in the serial circuit (13) as a function (20) of the light intensity level output to be applied, wherein the at least one, in particular, each light unit (11 ) is configured to measure said current circulating in said serial circuit (13) and to determine from said current as measured, the light intensity level output to control the brightness of the at least one, in particular each light unit (11 ), using an inverse of the function, wherein the function (20) is defined by predefined graph data.Clause B16. Airfield ground lighting system (10), wherein the airfield ground lighting system (10) comprises: a plurality of light units (11 ) arranged in a serial circuit (13), a power supply (12) adapted to supply the plurality of light units (1 1 ) with power in the form of a constant current circulating in the serial circuit (13), said power supply (12) comprising or consisting of a constant current regulator (121 ); wherein each light unit (11 ) comprises at least one light source (114) and optionally at least one activatable device (114, 116, 115); wherein said system (10) is configured to determine or detect a desired operating mode selected from:- a first mode of operation and- a second mode of operation,-wherein when the first mode is determined or selected, the airfield ground lighting system (10) is further configured to determine an expected power demand of the serial circuit (13) based on at least one of an expected light intensity level output to be applied, to at least one, in particular each light unit (11 ) and / or an expected activation state of the at least one activatable device of said light unit (1 1 ), and optionally at least one sensed characteristic of an environment of the serial circuit (13) and optionally an actual power absorbed by the serial plurality of light units (11 ); preferably wherein the airfield ground lighting system (10) or the power supply control unit (14) of said system (10) is configured to determine at least one parameter of the constant current expected to circulate in the serial circuit (13), said parameter being based on the expected power demand of the serial circuit (13);-wherein when the second mode is determined or selected, the airfield ground lighting system (10) is further configured to be operated such that the airfield ground lighting system (10) or the power supply control unit (14) is configured to determine the active current or the Root Mean Square current of the constant current tocirculate in the serial circuit (13) as a function (20) of the light intensity level output to be applied, wherein the at least one, in particular, each light unit (11) is configured to measure said current circulating in said serial circuit (13) and to determine from said current as measured, the light intensity level output to control the brightness of the at least one, in particular each light unit (11), using an inverse of the function, wherein the function (20) is defined by predefined graph data.

Claims

CLAIMS1. Airfield ground lighting system (10), comprising: a plurality of light units (11 ) arranged in a serial circuit (13), a power supply (12) adapted to supply the plurality of light units (1 1 ) with power in the form of a constant current circulating in the serial circuit (13), said power supply (12) comprising or consisting of a constant current regulator (121 ); wherein each light unit (11 ) comprises at least one light source (114) and optionally at least one activatable device (114, 116, 115); wherein the airfield ground lighting system (10) or a power supply control unit (14) of said system (10) is configured to determine an expected power demand of the serial circuit (13) based on at least one of an expected light intensity level output to be applied, to at least one, in particular each light unit (11 ) and / or an expected activation state of the at least one activatable device of said light unit (1 1 ), and optionally at least one sensed characteristic of an environment of the serial circuit (13) and optionally an actual power absorbed by the serial circuit (13) or at least one, in particular each one, of the plurality of light units (1 1 ); characterised in that the airfield ground lighting system (10) or the power supply control unit (14) of said system (10) is configured to determine at least one parameter of a constant current expected to circulate in the serial circuit (13) and expected to be supplied by the constant current regulator (121 ), said parameter being based on the expected power demand of the serial circuit (13).

2. Airfield ground lighting system (10), wherein the airfield ground lighting system (10) comprises: a plurality of light units (11 ) arranged in a serial circuit (13), a power supply (12) adapted to supply the plurality of light units (1 1 ) with power in the form of a constant current circulating in the serial circuit (13), said power supply (12) comprising or consisting of a constant current regulator (121 ); wherein each light unit (11 ) comprises at least one light source (114) and optionally at least one activatable device (114, 116, 115); wherein said system (10) or a power supply control unit (14) of said system (10) is configured to determine or detect a desired operating mode selected from:- a first mode of operation and- a second mode of operation,-wherein when the first mode is determined or selected, the airfield ground lighting system (10) or the power supply control unit (14) of said system (10) is further configured to determine an expected power demand of the serial circuit (13)based on at least one of an expected light intensity level output to be applied, to at least one, in particular each light unit (11 ) and / or an expected activation state of the at least one activatable device of said light unit (11 ), and optionally at least one sensed characteristic of an environment of the serial circuit (13) and optionally an actual power absorbed by the serial plurality of light units (1 1 ); preferably wherein the airfield ground lighting system (10) or the power supply control unit (14) of said system (10) is configured to determine at least one parameter of a constant current expected to circulate in the serial circuit (13) and expected to be supplied by the constant current regulator (121 ), said parameter being based on the expected power demand of the serial circuit (13);-wherein when the second mode is determined or selected, the airfield ground lighting system (10) or the power supply control unit (14) of said system(10) is further configured to determine the active current or the Root Mean Square current of the constant current expected to circulate in the serial circuit (13) and expected to be supplied by the constant current regulator (121 ) as a function (20) of the expected light intensity level output to be applied, wherein the at least one, in particular, each light unit(1 1 ) is configured to measure the active current or the Root Mean Square current circulating in said serial circuit (13) and to determine from said current as measured, the light intensity level output to control the brightness of the at least one, in particular each light unit (11 ), using an inverse of the function, wherein the function (20) is defined by predefined graph data.

3. Airfield ground lighting system (10) according to claim 1 or 2, wherein the airfield ground lighting system (10) or the power supply control unit of said system is configured to coordinate at least one of:- a modification of a light intensity level output applied to the at least one, in particular each light unit (1 1 ) to match the expected light intensity level output to be applied, to at least one, in particular each light unit (11 ), said modification being referred as light intensity level output modification and / or-an activation or deactivation of the at least one activatable device (1 14, 1 16, 115) of the at least one, in particular each light unit (1 1 ), said activation or deactivation being referred as activatable device activation or deactivation, in coordination with an adjustment of the constant current circulating in the serial circuit (13) to match the at least one parameter of the constant current expected to circulate in the serial circuit (13) and expected to be supplied by the constant current regulator (121 ), said adjustment being referred as constant current adjustment.

4. Airfield ground lighting system (10) according to the preceding claim, wherein at least one of the light intensity level output modification and / or theactivatable device activation or deactivation is first performed and then the constant current adjustment is performed, preferably said adjustment corresponding a constant current intensity level increase or decrease and / or said modification corresponding a light intensity level output increase or decrease.

5. Airfield ground lighting system (10) according to Claim 3, wherein the constant current adjustment is performed first and then the light intensity level output modification is performed, preferably said adjustment corresponding a constant current intensity level increase or decrease and / or said modification corresponding a light intensity level output increase or decrease.

6. Airfield ground lighting system (10) according to Claim 5, wherein the light intensity level output modification is performed with a delay relative to the constant current adjustment, the delay being greater than 0.1 ms, preferably greater than 1 ms, but less than 500 ms, preferably said delay being selected to allow a stabilisation of the serial circuit (13) after the constant current adjustment.

7. Airfield ground lighting system (10) according to Claim 3, wherein the constant current adjustment is performed first and then the activatable device activation or deactivation is performed, preferably said adjustment corresponding a constant current intensity level increase or decrease.

8. Airfield ground lighting system (10) according to any of Claims 3 to 7 , wherein the airfield ground lighting system (10) is configured to determine a first starting and / or ending point for starting and / or ending at least one of the light intensity level output modification and / or the activatable device activation or deactivation, and / or a second starting and / or ending point for starting and / or ending the constant current adjustment.

9. Airfield ground lighting system (10) according to any one of the preceding claims, wherein each light unit (11 ) further comprises the at least one activatable device (1 14, 116, 1 15) and wherein the at least one activatable device (114, 116, 115) comprises at least one of at least one further light source (1 14), one or more sensors (1 15), and / or a heating kit (1 16).

10. Airfield ground lighting system (10) according to any of the preceding claims, wherein the at least one sensed characteristic of an environment of the serial circuit is one or more of visibility condition, temperature and / or humidity.

11. Airfield ground lighting system (10) according to any of the preceding claims, wherein the airfield ground lighting system (10) is configured to transmit a given light intensity level output and / or a given activation or deactivation state of the at least one activatable device to at least one, in particular each one, of the pluralityof light units (11 ) as a control signal, via wireless communication and wherein the at least one, in particular, each light unit (1 1 ) comprises least one light source (114) and said light unit (1 1 ) is configured to extract the light intensity level output from the control signal as received and to control with the light intensity level output received the brightness of the least one light source (1 14).

12. Airfield ground lighting system (10) according to any of Claims 1 to 11 , wherein the airfield ground lighting system (10) is configured to transmit a given light intensity level output and / or a given activation or deactivation state of the at least one activatable device to at least one, in particular each one, of the plurality of light units (1 1 ) as a control signal, via wired communication, such as wired communication via the serial circuit and wherein the at least one, in particular, each light unit (1 1 ) comprises least one light source (1 14) and said light unit (1 1 ) is configured to extract the light intensity level output from the control signal as received and to control with the light intensity level output received the brightness of the least one light source (1 14), wherein:- the control signal is selected from a group comprising a modulation control signal, a frequency shift keying control signal, an orthogonal frequency division multiplexing control signal, a spread spectrum control signal or a duty cycle control signal such as frequency-based control or a pulse width control, and / or-the airfield ground lighting system is configured such as when the control signal is extracted in the at least one, in particular each light unit, the extraction of data associated to the light intensity level output is performed without measuring a parameter representing an active current or a Root Mean Square current of the constant current circulating in the serial circuit.

13. Airfield ground lighting system (10) according to any one of the preceding claims, wherein the airfield ground lighting system (10) is configured to determine the at least one parameter of a constant current expected to circulate in the serial circuit (13) and expected to be supplied by the constant current regulator (121 ) with an objective to minimize the power losses in the power lines of the serial circuit (13), while at least one attribute of one or more of the constant current regulator (121 ), the plurality of light units (11 ) or the serial circuit (13), such as at least one of a minimal voltage, a maximum voltage, a minimal current and / or a maximal power, remain(s) in the predefined operating ranges of one or more of the constant current regulator (121 ), the plurality of light units (1 1 ) or the serial circuit (13).

14. Airfield ground lighting system (10) according to any one of the preceding claims, wherein the at least one parameter of a constant current expected to circulate in the serial circuit (13) and expected to be supplied by the constant currentregulator (121 ) comprises or consists in a constant current intensity level, in particular an active current or a Root Mean Square current, preferably said active current or Root Mean Square current not exceeding 2.6 A, in particular not exceeding 2 A, in operation.

15. Airfield ground lighting system (10) according to any one of the preceding claims, wherein the at least one parameter of a constant current expected to circulate in the serial circuit (13) and expected to be supplied by the constant current regulator (121 ) further comprises at least one control waveform parameter, in particular, at least one pulse width modulation control parameter.

16. Airfield ground lighting system (10) according to claim 14 in combination with claim 15, wherein the airfield ground lighting system (10) is configured so that when the constant current intensity level of the constant current level expected to circulate in the serial circuit (13) and expected to be supplied by the constant current regulator (121 ) is below a certain threshold, the airfield ground lighting system (10) or a power supply control unit (14) of said system (10) is configured to modulate a constant current to circulate in the serial circuit (13), with waveform having a frequency from 3 to 10 Hz, a duty cycle between 40 to 60% and a current amplification factor inversely proportional to the duty cycle, wherein the at least one pulse width modulation control parameter comprises at least one of the frequency, the duty cycle, and / or the current amplification factor.

17. Airfield ground lighting system (10) according to any one of the preceding claims, wherein light intensity level output values comprise continuous levels or are discretized in a series a plurality of light intensity level outputs (Xi,0, Xu, X2,max), in particular with at least 20 discrete levels, preferably at least 50 discrete levels, more preferably at least 100 discrete levels, in particular preferably at least 200 discrete levels.

18. Airfield ground lighting system (10) according to any one of the preceding claims, wherein an expected or the actual power demand of at least one, in particular, each one of the plurality of light units (11 ) is transmitted by said light (1 1 ) or determined by the airfield ground lighting system (10) or the power supply control unit (14), and wherein the expected or actual power demand of the serial circuit (13) is based on an aggregation of the expected or actual power demand of each one of the plurality of light units (1 1 ) or an extrapolation of the expected or actual power demand of at least one of the plurality of light units (11 ).

19. Airfield ground lighting system (10) according to any one of the preceding claims, wherein the airfield ground lighting system (10) or the power supply control unit (14) of said system (10) is further configured to determine the expected powerdemand of the serial circuit (13) also based on an operating parameter from at least one, in particular each one, of the plurality of light units (11 ), preferably said operating parameter being selected from one or more of a buffer voltage, a light source driver duty cycle and / or a temperature of said light unit (11 ), preferably wherein said operating parameter of at least one, in particular, each one of the plurality of light units (11 ) is transmitted by said light unit (11 ), preferably via wireless and / or wired communication, such as wired communication via the serial circuit (13).

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