Airfield ground lighting system with improved energy efficiency

Abstract

An airfield ground lighting (AGL) system is configured to operate one or more constant current circuits of AGL lights according to a first mode of operation, referred to as conventional operation, and according to at least one second mode of operation, referred to as reduced current level operation. In the first mode of operation, a control unit implements a first dimming curve (20) for the AGL lights, in which a plurality of first constant current levels (A0, Ai, Amax) are associated with a plurality of first light intensity levels (X0, Xi, Xmax) output by the AGL lights. In the second mode of operation, the control unit implements a second dimming curve (30) for the AGL lights, in which a plurality of second constant current levels (B0, Bi, Bmax) are associated with a plurality of second light intensity levels output by the AGL lights. At least one, some or preferably all, of the plurality of second intensity levels is or are equal to at least one, some or preferably all of the plurality of first intensity levels (X0, Xi, Xmax). The second dimming curve implements at least one reduced current level compared to the first dimming curve for one or more same intensity level(s).

Description

AIRFIELD GROUND LIGHTING SYSTEM WITH IMPROVED ENERGY EFFICIENCYTechnical field

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

[0002] Reducing carbon footprint and more 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 still remains an ongoing objective. US2019 / 246469 A1 relates to an apparatus for supplying electric power to an electric device and proposes using an output frequency of a constant current regulator as an additional controlling method in the range <10% Intensity.Summary

[0003] According to a first aspect of the present disclosure, there is therefore provided an airfield ground lighting system as set out in the appended claims. AGL systems according to the present disclosure are configured to operate one or more constant current circuits of AGL lights according to a first mode of operation, referred to as conventional operation, and according to at least one second mode of operation, referred to as reduced current level operation. In the first mode of operation, a control unit implements a first dimming curve for the AGL lights, in which a plurality of first constant current levels are associated with a plurality of first (light) intensity or brightness levels output by the AGL lights. In the second mode of operation, the control unit implements a second dimming curve for the AGL lights, in which a plurality of second constant current levels are associated with a plurality of second (light) intensity or brightness levels output by the AGL lights. At least one, some or preferably all, of the plurality of first intensity levels is or are equal to at least one, some or preferably all of the plurality of second intensity levels. The second dimming curve implements at least one, preferably multiple reduced current level(s) compared to the first dimming curve for one or more same intensity level(s). Hence, for at least one equal first and second intensity level, an associated second constant current level is smaller than an associated first constant current level.

[0004] One advantage of such an AGL system, is that since the second mode of operation defines one or more reduced current levels for equal intensity levels (of a same light colour) compared to the conventional dimming curve, power consumption by the light sources can be reduced. In addition, resistive power losses along the power line can also be reduced as a result of the reduced current levels. Such an advantage is achieved while still enabling the AGL lights to be operated in the first mode of operation when needed, e.g. when higher power is required, possibly due to activation of additional electrical devices such as heating kits that draw power from the same serial circuit. 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.

[0005] Advantageously, the control unit implements a mode selection logic configured to determine an operating mode selected from the first mode of operation and the at least one second mode of operation for the serial circuit. The mode selection logic can be configured to determine the operating mode automatically and / or based on an external input. In an automatic selection mode, the mode selection logic can comprise a decision logic configured to automatically select the operating mode based on an input representative of at least one of: an attribute of the constant current regulator unit, an attribute of the plurality of light units and possibly a sensed characteristic of an environment of the first serial circuit. Specific examples of an attribute of the serial circuit or AGL lights are a requested power and / or number and type of AGL lights, an activation state of activatable devices included in the AGL lights, e.g. peripheral devices such as heating kits, sensors etc. that may be activated depending on circumstances. Specific examples of attributes of the constant current regulator unit are the number of serial circuits that are active and connected to the constant current regulator unit, maximum voltage and / or minimum current. Specific examples of a sensed characteristic of the environment are weather or visibility conditions, temperature and humidity. The mode selection logic can be configured to determine an operating mode for each serial circuit and / or for each constant current regulator unit of the AGL system individually. As a result, a logic is implemented allowing to operate the AGL system in the most energy efficient manner while taking safety measures into account.

[0006] Advantageously, the second constant current levels are adjustable, e.g. by the mode selection or decision logic. The second constant current levels can be adjusted based on attributes of the serial circuit and / or the constant current regulator unit and / or the AGL lights, such as number and type of AGL lights or the number of serial circuits that are active and connected to the constant current regulator unit. Such asolution improves the adaptability and compatibility of the AGL system. According to one aspect, the second current levels are obtained by adjusting, e.g., reducing, the first current levels to obtain the second mode of operation.

[0007] According to a second aspect of the present disclosure, there is provided a method of operating AGL lights, as set out in the appended claims. The AGL system according to the first aspect advantageously implements the method according to the second aspect.Brief description of the drawings

[0008] 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:

[0009] Figure 1 represents a diagram of an AGL system;

[0010] Figure 2 represents a diagram of an AGL light;

[0011] Figure 3 represents a dimming curve of an AGL light;

[0012] Figure 4 represents a diagram with two dimming curves for a sameAGL light, in which one dimming curve implements reduced current levels;

[0013] Figure 5 represents another diagram with two dimming curves for a same AGL light, in which one dimming curve implements reduced current levels;

[0014] Figure 6 represents a third diagram with two dimming curves for a same AGL light, in which one dimming curve implements reduced current levels which are all smaller than the minimum current level of the other dimming curve;

[0015] Figure 7 represents a diagram of a control structure to control an operating mode of a circuit of AGL lights.Detailed description

[0016] Referring to Fig. 1 , an AGL system 10 comprises a plurality of AGL 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 multiple serial circuits 13 which may beoperated to simultaneously receive power from the power supply 12 I constant current regulator unit 121.

[0017] Referring to Fig. 2, the AGL lights 1 1 comprise a light fixture 1 11 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.

[0018] 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 during winter 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.

[0019] 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 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 nonoverlapping 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 1 12 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 113 wirelessly, e.g. via a wireless receiver integrated in the AGL light.

[0020] 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.

[0021] 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 117, as shown in Fig. 2. The isolating transformer 1 12 can have a transformer 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.

[0022] Referring again to Fig. 1 , the operating commands for the control units of the various AGL lights 1 1 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 113 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. 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 AGL lights 1 1 based on the external control commands.

[0023] 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 throughthe serial circuit 13. 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.

[0024] Referring to Fig. 3, so-called 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 1 14. 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 A=i n, n < 1 , Ao < A < Amaxcorresponding with intermediate brightness levels ,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.

[0025] Such a dimming curve is typically defined for brightness levels for incandescent lights, which have an exponential relation between applied current level and brightness output. LED light sources naturally have a more linear relation between applied current level and brightness output. In AGL systems, the control unit 113 of the LED light sources 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.Table 1 : Approximate dimming curve values for conventional (6.6A) operation according to ICAO Aerodrome Design Manual, Document 9157, 2ndEdition, 2017, Part 5, Chapter 12.9

[0026] The control unit 14 can be configured to receive a brightness level set point for the AGL lights 1 1 of one or more serial circuits 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.

[0027] 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 Xi.

[0028] The maximum current level Amax in conventional AGL constant current circuits is typically 6.6 A. It will also be appreciated that power consumption is quadratic proportional to the current level. According to an aspect of the present disclosure, alternative dimming curves are provided for the AGL systems, which define one or more reduced current levels for equal brightness levels compared to the conventional dimming curve 20. As a result, power consumption by the light sources can be reduced while maintaining the desired functionality and performance of the AGL system. In addition, resistive power losses along the power line can also be reduced as a result of the reduced current levels.

[0029] Referring to Fig. 4, the control unit 14 and / or the individual control units 1 13 can be implemented with a second dimming curve 30. This second dimming curve 30 implements one or more reduced current levels Bo, Bi, i=i m, Bmax, m < 1 , Bo < Bi < Bmax associated with one or more of the brightness levels Xo, X, Xmax. Hence, at least one, multiple, or all, of the brightness levels associated with the reduced current levels Bo, B, Bmax advantageously correspond with one or more brightness levels Xo, Xi;Xmax of the dimming curve 20. In this regard, m can be equal to n and the number m of reduced current levels Bi can be equal to the number n of conventional current levels Ai. Alternatively, m < n, and in some examples m > n.

[0030] At least one of Bo, Bi and Bmax is smaller than a current level Ao, A,Amax of the conventional dimming curve 20 corresponding with a same brightness levelXi. Advantageously, at least Bmax is smaller than Amax. It will be appreciated that dimming curve 30 can implement a reduced number of current levels Bi compared to the number of current levels Ai of conventional dimming curve 20, and correspondingly a reduced number of brightness levels. By way of example, dimming curve 20 implements current levels Ao, Ai, A3and Amaxcorresponding with brightness levels Xo, Xi, X3and Xmaxrespectively. For all these brightness levels, dimming curve 30 implements reduced current levels Bo, Bi, B2and Bmaxcorresponding with the brightness levels Xo, Xi, X3and Xmaxrespectively. However, dimming curve 20 can implement one or more additional current level A2and associated additional brightness level X2which may not be implemented in dimming curve 30.

[0031] In some examples, each of Bo, Bi and Bmaxis smaller than a corresponding current level Ao, Ai;Amaxof the conventional dimming curve 20, e.g. as shown in Fig. 4. Referring to Fig. 5, dimming curve 40 implements a minimum current level Bo equal to Aoof conventional dimming curve 20, whereas at least some of the other current levels Bi and Bmaxare each smaller than a corresponding current level Ai;Amaxof the conventional dimming curve 20. One advantage of such a dimming curve 40 is that the minimum current level at which the light sources can be turned OFF remains equal for different dimming curves. In addition, or alternatively, the current levels Bo, B, Bmaxof dimming curve 30, 40 can be selected to obtain a substantially linear relationship between current level and brightness level Xi. As a result, dimming curve 30, 40 can be linear. Yet alternatively, dimming curves 30, 40 can implement current levels Bi, Bmax, and possibly Bo, which are reduced in proportion compared to the current levels Ai;Amaxand possibly Aoof the conventional dimming curve 20, e.g. by a same factor: Bi = x.Ai, i = 1 , , n = max or i = 0, , n = max and 0 < x < 1 . Referring to Fig. 6, in some exemplary second dimming curves, Bmaxcan be smaller than the minimum current level Ao of the conventional dimming curve.

[0032] It will be appreciated that one or more of the brightness levels Xo,X, Xmaxand associated current levels Ao, A, Amaxand / or reduced current levels Bo, Bi, Bmaxcan be used for non-illuminating purposes, e.g. for a stand-by function of the lights to enable faster light-on or for accessories functionality, allowing one or more of the peripheral devices, e.g. sensors 115 and heating kit 116 to be operational but not the light source 114.

[0033] The second dimming curves 30, 40 can be predefined and fixed.Alternatively, one or more of the second dimming curves can be adjustable, e.g. for optimally adapting to a specific serial circuit. One or more parameters of the second dimming curve, e.g., one or more current levels Bo, Bi, Bmax, can be adjusted based onone or more attributes of the serial circuit and / or of the AGL lights, such as the loop length of the serial circuit, the number and / or type of AGL lights installed on the circuit, their (instant) power consumption and the minimum or maximum acceptable current of the AGL lights and / or of the CCR unit.

[0034] For at least some of the serial circuits 13 and associated CCR units121 , the control unit 14 and the individual control units 113 are advantageously implemented with one or more of the second dimming curves 30, 40, in addition to the conventional dimming curve 20, for a same light colour output. For these serial circuits 13 and associated CCR units 121 , both control units 14 and 113 are configured to operate in a plurality of operating modes, each one associated with a corresponding dimming curve. Hence, in a conventional operating mode, the control unit 14 and the individual control units 113 implement the conventional dimming curve 20, and a brightness level setpoint input to control unit 14 for serial circuit 13 is translated to a current level Ao, Ai;Amax according to the conventional dimming curve 20 by control unit 14, which current level is fed as control command to the respective CCR unit 121 , which adjusts the current on the serial circuit 13 to the current level received by the control unit 14. The individual control units 1 13 are configured to translate the sensed current level back to a brightness level according to the conventional dimming curve 20.

[0035] In a second operating mode, the control unit 14 and the individual control units 1 13 implement a reduced current level dimming curve 30, 40, and a brightness level setpoint input to control unit 14 for serial circuit 13 is translated to a current level Bo, Bi, Bmax according to the associated dimming curve 30, 40 by control unit 14, and this current level fed as control command to the respective CCR unit 121 , which adjusts the current on the serial circuit 13 to the current level received by the control unit 14. The reduced current level on the serial circuit is translated back to a brightness level by the individual control units 113 according to the same dimming curve 30, 40 that is utilized by control unit 14 for setting the current level on the serial circuit. It will be appreciated that the control unit 14 and the individual control units 1 13 can be implemented with multiple of these second operating modes for a particular serial circuit, each with a specific dimming curve.

[0036] By implementing such plurality of operating modes and dimming curves, the present disclosure allows for a more efficient and tailored reduction of power consumption in AGL systems, while maintaining sufficient operational flexibility. In addition, the second dimming curves can be customized for each specific circuit, taking into account various factors such as current length, number of AGL lights, and device capabilities, ultimately leading to a more energy-efficient solution.

[0037] Referring to Fig. 7, to know in which mode the system is operating, an operating mode indicator 147 can be associated with a particular serial circuit 13. The operating mode indicator is indicative of the mode of operation, i.e. the specific dimming curve, that is selected for a particular serial circuit and / or CCR unit. The operating mode indicator 147 can be determined by a mode selection logic 143, e.g. implemented in control unit 14 and / or CCR unit 121. The mode selection logic 143 is configured to select the operating mode for one or more of the serial circuits 13 of the AGL system 10, e.g. from conventional dimming curve operation and one or more reduced current dimming curves, and advantageously to set the operating mode indicator for the particular serial circuit accordingly. The mode selection logic 143 can be configured to determine the operating mode based on an external input 145, e.g. a control command from the control tower 9 setting the operating mode for one or more serial circuits. In addition, or alternatively, the mode selection logic 143 can be configured to determine the operating mode automatically, e.g. based on a decision logic 144 implemented in the mode selection logic 143.

[0038] The decision logic 144 can be configured to determine the operating mode automatically based on an input 146 from the CCR unit 121 and / or the serial circuit 13 and possibly from one or more individual AGL lights 11 of the serial circuit 13. Input 146 can comprise possibly measured values of one or more attributes of the respective serial circuit and / or AGL lights, such as power (or voltage) drawn by the serial circuit, number of AGL lights connected to the serial circuit, loop length of the serial circuit, etc. In addition, or alternatively, input 146 can comprise possibly measured values of attributes relating to an environment of the serial circuit, such as environmental conditions (e.g. visibility conditions, temperature, etc.). To this end, the CCR unit 121 and / or one or more AGL lights 11 can be configured to transmit (measurement) data relating to (attributes of) the serial circuit 13, such as power or voltage of the serial circuit and / or relating to an environment of the serial circuit (e.g. measured by the sensors 1 15), to the mode selection logic 143 and / or decision logic 144. Alternatively, the mode selection logic 143 can be configured to determine the operating mode both based on an external input 145 and based on an automatic decision logic 144, e.g. in a cascaded control logic. The decision logic 144 can override any external control command 145 setting an operating mode, or vice versa.

[0039] Advantageously, the decision logic 144 can implement a metric configured to adjust a value of an attribute of one or more dimming curves 20, 30, 40 associated with a CCR unit and / or serial circuit. The metric can be configured to adjust one or more current levels Ao, A, Amax and / or Bo, Bi, Bmax, based on an attribute of therespective serial circuit, the CCR unit, and / or of the AGL lights of the serial circuit, such as number of serial circuits connected to the CCR unit, number and / or type of AGL lights connected to the serial circuit, minimum and / or maximum acceptable current of any one of the AGL lights. The metric can be configured to adjust the current level based on other inputs as desired.

[0040] It will be appreciated that the control unit 14 can comprise a mode selection logic 143 in respect of some or all CCR units 121 and / or in respect of some or all serial circuits 13. While Fig. 7 illustrates the mode selection logic 143 as part of the control unit 14, it will be appreciated that the mode selection logic 143 can be provided as part of a control unit of the CCR unit 121 .

[0041] The operating mode for serial circuit 13 determined by the mode selection logic 143 or otherwise, e.g. the operating mode indicator 147, can be communicated to the control units 113 of the AGL lights 11 in the serial circuit in various ways. The communication of the (change of) operating mode can be performed through a bidirectional communication method with the AGL lights 11 , or alternatively through a unidirectional communication method, or through a broadcast method. In a first option, the operating mode indicator can be communicated to the control units 113 via a power line communication technique, e.g. via the CCR unit and / or the serial circuit 13. Specific examples of suitable power line communication methods for communicating the operating mode are: a specific ON / OFF sequence of the input power of the AGL lights, which is recognized by the control units 1 13 as an operating mode indicator; 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.

[0042] Alternatively, the operating mode indicator can be transmitted to theAGL 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).

[0043] A change of operating mode can be commanded by the mode selection logic 143 at start-up of the serial circuit 13 and / or of the CCR unit 121 , so that any possible impact on the performance or the behavior of the AGL lights is minimal. Inaddition, or alternatively, the change of operating mode can be commanded by the mode selection logic 143 dynamically while the serial circuit 13 and the AGL lights 11 are operating, allowing to cope with unforeseen circumstances, e.g. sudden change of weather conditions.

[0044] Upon detection or receipt of the operating mode indicator by the individual control units 113, the dimming curve associated with the selected operating mode can be fetched, e.g. from a (local) memory, and utilized by the control units 1 13 to translate the current levels on the serial circuit 13 to a brightness level for the light source 114.

[0045] Advantageously, the operating mode indicator can include dimming curve information. As a result, at least part of the dimming curve information is communicated to the control units 113 along with selection of the respective operating mode. This is advantageous when the control units do not include sufficient memory to store information relative to multiple dimming curves, or when dynamical dimming curves are utilized, which may change in time, e.g. when one or more of the current levels Bo, Bi, Bmax (or Ao, A, Amax) of a specific dimming curve is changed.

[0046] In some examples, the power that a CCR unit 121 can supply to a serial circuit is limited by a maximal voltage in the circuit. When a reduced current level (second) dimming curve 30, 40 is utilized for a particular serial circuit 13, the voltage in the circuit may be higher for a same power level compared to the conventional dimming curve 20. As a result, sometimes the maximal power that can be supplied in a reduced current level operating mode is reduced compared to conventional operating mode. Hence, if a higher power is demanded or requested for the serial circuit, the mode selection logic 143 (e.g. the decision logic 144) can be configured to switch from a second operating mode back to conventional operating mode.

[0047] Referring again to Fig. 2, the activation of some or all peripheral devices of an AGL light 11 , such as sensors 115 and / or heating kit 116, may lead to more power being drawn from the serial circuit 13. The mode selection logic 143 can be configured to switch from a second operating mode back to conventional operating mode, or at least to an operating mode including an increased current level dimming curve, based on one or more of the sensors 115 and / or heating kit 116 being activated.

[0048] In some examples, a single CCR unit 121 can be connected to a plurality of serial circuits 13. The CCR unit can be configured to selectively activate one or multiple of the serial circuits 13 connected to it. Based on the number and / or type of serial circuits that are active at a specific instant of time, and possibly the power requested to the CCR unit, the mode selection logic 143 can be configured to select anappropriate operating mode (dimming curve) that optimizes energy consumption. In some examples, the AGL lights of some of the serial circuits connected to a CCR unit, may be configured to work in a second operating mode, whereas other serial circuits connected to the same CCR unit may only be configured to work in a conventional operating mode. Based on which serial circuits are active, the mode selection logic can determine which operating mode to select for a particular CCR unit. This allows an AGL system to be updated gradually to implement the second operating modes. In addition, it allows the AGL system to work seamlessly when AGL components from different suppliers are installed, ensuring compatibility and ease of implementation.

[0049] Advantageously, the AGL lights 11 can be provided with a configurable device, e.g. a switch, configured to pre-set the mode of operation at the time of installation. When the AGL light is installed, the control unit 1 13 will automatically start operating in the configured mode of operation. This avoids the control unit 14 and / or CCR unit 121 to have to broadcast or re-set the current mode of operation.

[0050] It will be appreciated that aspects of the present disclosure can be implemented in the software of various components of the AGL system. Advantageously, implementation of aspects of the present disclosure does not typically require additional hardware installation and implementation costs can be limited while achieving major energy savings. In addition, the current levels corresponding to the different brightness levels of the circuit in the second dimming curves need not be fixed or predefined but can be adapted and configured to fit each circuit optimally, leading to a greater adaptability of the AGL system.

[0051] Airfield lighting systems must adhere to strict safety regulations and standards set by organizations like the FAA and ICAO. Aspects of the present disclosure are capable of maintaining compliance with these standards while reducing power consumption. In addition, the performance and longevity of the lighting system components can be maintained while reducing power consumption.

[0052] Various aspects and embodiments of the present invention are defined by the following clauses :1. Airfield ground lighting (AGL) system (10), comprising: a plurality of light units (11 ) arranged in a first serial circuit (13), a power supply (12) comprising a constant current regulator unit (121 ) configured to supply the plurality of light units with power, wherein the AGL system is configured to operate the first serial circuit in a first mode of operation in which the constant current regulator unit implementsa plurality of first constant current levels (Ao, A, Amax) associated with a plurality of first light intensity level outputs (Xo, Xi;Xmax) of the plurality of light units, wherein the AGL system is configured to operate the first serial circuit in at least one second mode of operation in which the constant current regulator unit implements a plurality of second constant current levels (Bo, Bi, Bmax) associated with a plurality of second light intensity level outputs of the plurality of light units, wherein at least one of the plurality of second light intensity level outputs is equal to at least one of the plurality of first light intensity level outputs, and wherein for at least one equal first and second light intensity level output, an associated second constant current level (Bo, Bi, Bmax) is smaller than an associated first constant current level (Ao, A, Amax).2. AGL system of clause 1 , wherein the AGL system further comprises a control unit (14) implementing a mode selection logic (143) configured to determine an operating mode selected from the first mode of operation and the at least one second mode of operation for the first serial circuit (13),3. AGL system of the preceding clause, wherein the mode selection logic is configured to communicate an indicator (146) representative of the selected operating mode to the constant current regulator unit (121 ) and / or the plurality of light units (1 1 ).4. AGL system of the preceding clause, wherein the plurality of light units (11 ) comprise individual control units (113) configured to receive the indicator and to drive a light source (114) of the respective light unit based on the selected operating mode.5. AGL system of any one of the clauses 2 to 4, wherein the mode selection logic (143) is configured to select the operating mode automatically based on a decision logic (144) implemented in the control unit and / or configured to select the operating mode based on a mode selection signal (145) received at an input (9) of the control unit (14).6. AGL system of the preceding clause, wherein the decision logic (144) is configured to automatically select the operating mode based on an input (147) representative of at least one of: an attribute of the constant current regulator unit (121 ), an attribute of the plurality of light units (11 ) and a sensed characteristic of an environment of the first serial circuit.7. AGL system of any one of the clauses 2 to 6, wherein the plurality of light units (11 ) comprise activatable devices (1 14, 116, 1 15), wherein the mode selection logic (143) is configured to determine the operating mode based on anactivation state of the activatable devices, preferably the activatable devices comprising a heating kit (116) and the mode selection logic (143) configured to determine the operating mode based on an activation state of the heating kit.8. AGL system of any one of the clauses 2 to 7, further comprising a second plurality of light units arranged in one or more second serial circuits connected to the constant current regulator unit (121 ), wherein the mode selection logic (143) is configured to determine the operating mode based on an activation state of the first serial circuit and of the one or more second serial circuits.9. AGL system of any one of the preceding clauses, wherein multiple ones of the plurality of first light intensity level outputs (Xo, Xi;Xmax) are equal to associated ones of the plurality of second light intensity level outputs and wherein for the multiple equal first and second light intensity level outputs, associated second constant current levels are smaller than associated first constant current levels.10. AGL system of any one of the preceding clauses, wherein at least one of the plurality of first constant current levels (Ao, Ai;Amax) and / or second constant current levels (Bo, Bi, Bmax) is adjustable.11. AGL system of the preceding clause, wherein at least one of the plurality of second constant current levels is adjustable based on a metric, preferably wherein the metric is evaluated based on an input (147) representative of at least one of: an attribute of the constant current regulator unit (121 ), an attribute of the plurality of light units (1 1 ), and a sensed characteristic of an environment of the first serial circuit.12. Method of operating a serial circuit (13) of airfield ground lighting (AGL) lights (11 ), the method comprising: operating the AGL lights according to a first mode of operation in which the AGL lights are supplied with a plurality of first constant current levels (Ao, A, Amax) respective of first light intensity levels (Xo, X, Xmax) output by the AGL lights, operating the AGL lights according to at least one second mode of operation in which the AGL lights are supplied with a plurality of second constant current levels (Bo, Bi, Bmax) respective of second light intensity levels output by the AGL lights, wherein at least one of the plurality of second light intensity levels is equal to at least one of the plurality of first light intensity levels and wherein for at least one equal first and second light intensity level, an associated second constant current level (Bo, Bi, Bmax) is smaller than an associated first constant current level (Ao, A, Amax).13. Method of the preceding clause, wherein multiple ones of the plurality of first light intensity levels are equal to associated ones of the plurality of second light intensity levels and wherein for the multiple ones of the equal first and second lightintensity levels, associated second constant current levels are smaller than associated first constant current levels.14. Method of clause 12 or 13, comprising adjusting at least one of the plurality of second constant current levels (Bo, Bi, Bmax) based on a metric, preferably wherein the metric is evaluated based on an input (147) representative of at least one of: an attribute of the constant current regulator unit (121 ), an attribute of the plurality of light units (1 1 ), and a sensed characteristic of an environment of the serial circuit.15. Method of any one of clauses 12 to 14, comprising selecting an operating mode from the first mode of operation and the second mode of operation based on a logic and / or based on an external mode selection command and operating the AGL lights according to the selected operating mode, preferably the logic comprising automatically selecting the operating mode based on one or more attributes of the constant current regulator unit (121 ) and / or of the plurality of AGL lights (11 ), preferably the one or more attributes being a measured parameter and / or an activation state of one or more devices (114, 115, 116) of the plurality of AGL lights.

Claims

CLAIMS1. Airfield ground lighting - hereafter abbreviated AGL - system (10), comprising: a plurality of light units (11 ) arranged in a first serial circuit (13), a power supply (12) comprising a constant current regulator unit (121 ) configured to supply the plurality of light units with power, wherein the AGL system is configured to operate the first serial circuit in a first mode of operation in which the constant current regulator unit implements a plurality of first constant current levels (Ao, A, Amax) associated with a plurality of first light intensity level outputs (Xo, Xi;Xmax) of the plurality of light units, characterized in that the AGL system is configured to operate the first serial circuit in at least one second mode of operation in which the constant current regulator unit implements a plurality of second constant current levels (Bo, Bi, Bmax) associated with a plurality of second light intensity level outputs of the plurality of light units, wherein at least one of the plurality of second light intensity level outputs is equal to at least one of the plurality of first light intensity level outputs, wherein for at least one equal first and second light intensity level output, an associated second constant current level (Bo, Bi, Bmax) is smaller than an associated first constant current level (Ao, A, Amax), and wherein the AGL system further comprises a control unit (14) implementing a mode selection logic (143) configured to determine an operating mode selected from the first mode of operation and the at least one second mode of operation for the first serial circuit (13).

2. AGL system of the preceding claim, wherein the mode selection logic is configured to communicate an indicator (146) representative of the selected operating mode to the constant current regulator unit (121 ) and / or the plurality of light units (1 1 ).

3. AGL system of the preceding claim, wherein the plurality of light units (11 ) comprise individual control units (113) configured to receive the indicator and to drive a light source (114) of the respective light unit based on the selected operating mode.

4. AGL system of any one of the claims 1 to 3, wherein the mode selection logic (143) is configured to select the operating mode automatically based on a decision logic (144) implemented in the control unit and / or configured to select theoperating mode based on a mode selection signal (145) received at an input (9) of the control unit (14).

5. AGL system of the preceding claim, wherein the decision logic (144) is configured to automatically select the operating mode based on an input (147) representative of at least one of: an attribute of the constant current regulator unit (121 ), an attribute of the plurality of light units (1 1 ) and a sensed characteristic of an environment of the first serial circuit.

6. AGL system of any one of the claims 1 to 5, wherein the plurality of light units (11 ) comprise activatable devices (1 14, 116, 1 15), wherein the mode selection logic (143) is configured to determine the operating mode based on an activation state of the activatable devices, preferably the activatable devices comprising a heating kit (116) and the mode selection logic (143) configured to determine the operating mode based on an activation state of the heating kit.

7. AGL system of any one of the claims 1 to 6, further comprising a second plurality of light units arranged in one or more second serial circuits connected to the constant current regulator unit (121 ), wherein the mode selection logic (143) is configured to determine the operating mode based on an activation state of the first serial circuit and of the one or more second serial circuits.

8. AGL system of any one of the preceding claims, wherein multiple ones of the plurality of first light intensity level outputs (Xo, Xi;Xmax) are equal to associated ones of the plurality of second light intensity level outputs and wherein for the multiple equal first and second light intensity level outputs, associated second constant current levels are smaller than associated first constant current levels.

9. AGL system of any one of the preceding claims, wherein at least one of the plurality of first constant current levels (Ao, Ai;Amax) and / or second constant current levels (Bo, Bi, Bmax) is adjustable.

10. AGL system of the preceding claim, wherein at least one of the plurality of second constant current levels is adjustable based on a metric, preferably wherein the metric is evaluated based on an input (147) representative of at least one of: an attribute of the constant current regulator unit (121 ), an attribute of the plurality of light units (1 1 ), and a sensed characteristic of an environment of the first serial circuit.

11. Method of operating a serial circuit (13) of airfield ground lighting - hereafter abbreviated AGL - lights (1 1 ), the method comprising: operating the AGL lights according to a first mode of operation in which the AGL lights are supplied with a plurality of first constant current levels (Ao, A, Amax) respective of first light intensity levels (Xo, X, Xmax) output by the AGL lights,operating the AGL lights according to at least one second mode of operation in which the AGL lights are supplied with a plurality of second constant current levels (Bo, Bi, Bmax) respective of second light intensity levels output by the AGL lights, selecting an operating mode from the first mode of operation and the second mode of operation based on a logic and / or based on an external mode selection command and operating the AGL lights according to the selected operating mode, wherein at least one of the plurality of second light intensity levels is equal to at least one of the plurality of first light intensity levels and wherein for at least one equal first and second light intensity level, an associated second constant current level (Bo, Bi, Bmax) is smaller than an associated first constant current level (Ao, A, Amax).

12. Method of the preceding claim, wherein multiple ones of the plurality of first light intensity levels are equal to associated ones of the plurality of second light intensity levels and wherein for the multiple ones of the equal first and second light intensity levels, associated second constant current levels are smaller than associated first constant current levels.

13. Method of claim 11 or 12, comprising adjusting at least one of the plurality of second constant current levels (Bo, Bi, Bmax) based on a metric, preferably wherein the metric is evaluated based on an input (147) representative of at least one of: an attribute of the constant current regulator unit (121 ), an attribute of the plurality of light units (1 1 ), and a sensed characteristic of an environment of the serial circuit.

14. Method of any one of claims 11 to 13, wherein the logic comprises automatically selecting the operating mode based on one or more attributes of the constant current regulator unit (121 ) and / or of the plurality of AGL lights (11 ).

15. Method of the preceding claim, wherein the one or more attributes are a measured parameter and / or an activation state of one or more devices (1 14, 1 15, 116) of the plurality of AGL lights.

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