WO2013186656A1

WO2013186656A1 - Adaptative safety led lighting system powered by battery plant.

Info

Publication number: WO2013186656A1
Application number: PCT/IB2013/054429
Authority: WO
Inventors: Nicholaos HILLAS; Liang Jia
Original assignee: Koninklijke Philips N.V.
Priority date: 2012-06-14
Filing date: 2013-05-29
Publication date: 2013-12-19

Abstract

A lighting driver includes a detector connected to mains voltage, a power converter connected to a DC power supply, and a controller. The detector detects a voltage level of the mains voltage. The power converter provides a DC drive current for driving a plurality of light emitting diodes (LEDs) responsive to the DC power supply. The controller controls the power converter to supply the DC drive current when the detected voltage level of the mains voltage drops below a threshold.

Description

ADAPTIVE SAFETY LED LIGHTING SYSTEM POWERED BY BATTERY PLANT

Technical Field

[0001] The present invention is directed generally to a lighting driver powered by a battery plant, and a safety lighting system including the lighting driver. More particularly, various inventive apparatuses and methods disclosed herein relate to an adaptive lighting driver powered by a battery plant for driving one or more light-emitting diode (LED) light sources, and a safety lighting system including an adaptive lighting driver for driving one or more LED light sources.

Background

[0002] Conventional safety lighting systems may include LED-based light sources that are powered by internal batteries. The internal batteries are charged when the AC mains voltage is active. Conventional safety lighting systems using internal batteries however typically provide lighting of fixed illumination level, and for a limited amount of time after loss of the AC mains voltage. Since the illumination (brightness) levels of the conventional safety lighting systems are typically fixed regardless of the level of ambient light available, the limited energy stored in the internal batteries may be depleted before the level of ambient light drops to a level at which the safety lighting is actually needed.

[0003] In some conventional applications, instead of internal batteries, battery plants may be used to power safety lighting systems which include LED-based light sources. The battery plants of such conventional applications may generally include a DC-AC inverter that converts the DC voltage provided by the battery plant into AC voltage that is routed to the LED-based light sources. However, such DC-AC inverters are typically lossy and inefficient. Additionally, each LED-based light source of such conventional applications necessarily includes an AC-DC converter and a DC-DC converter to convert the supplied AC voltage to a DC voltage suitable for the particular LED-based light source. Although the cost and size of these conventional applications may be somewhat reduced by eliminating the internal batteries, the systems are inefficient and expensive. [0004] It would be desirable to provide a safety lighting system of reduced size, complexity and cost. It would be further desirable to provide a safety lighting system that includes LED- based light sources powered by a battery plant, whereby the brightness of the LED-based light sources may be adaptively changed to conserve energy and consequently extend battery plant life.

[0005] Thus, it would be desirable to provide a lighting driver, and a lighting system including a lighting driver for use with LED-based light sources, which can satisfy one or more of these needs.

Summary

[0006] The present disclosure is directed to inventive apparatuses and methods for a lighting driver, and a lighting system that is powered by a battery plant and that includes a lighting driver for driving LED-based light sources. For example, in some embodiments the lighting driver includes a controller that can control a DC-DC power converter to adaptively change the brightness of LED-based light sources.

[0007] Generally, in one aspect, the invention focuses on a lighting driver that includes a detector configured to detect a voltage level of mains voltage, a power converter connected to a DC power source and configured to provide a DC drive current for driving a plurality of light emitting diodes (LEDs) responsive to the DC power source, and a controller configured to control the power converter to supply the DC drive current when the detected voltage level of the mains voltage drops below a threshold.

[0008] In one embodiment, the controller is further configured to control the power converter to adjust the DC drive current to change a brightness of the LEDs responsive to a detected level of ambient light. In another embodiment, a photocell is configured to detect the level of the ambient light. The photocell could be configured to be removably connectable to the lighting driver.

[0009] In various embodiments, the DC power source comprises a battery plant, e.g. a battery plant supplying -48V DC. Also, the power converter may include a DC-DC buck boost LED driver. [0010] The controller may be further configured to adjust the DC drive current to change a brightness of the LEDs when a voltage level of the DC power source drops below a second threshold.

[0011] According to some embodiments, the lighting driver further includes a regulator configured to convert an output of the power converter, and to provide the converted output to power the controller when the detected voltage level of the mains voltage drops below the threshold.

[0012] Generally, in another aspect, the invention relates to a lighting system that includes a plurality of light emitting diodes (LEDs), a first network connected to mains voltage and configured to provide a first DC drive current for driving the plurality of LEDs responsive to the mains voltage, and a second network. The second network comprises a detector configured to detect a voltage level of the mains voltage, a power converter connected to a DC power source and configured to provide a second DC drive current for driving the plurality of LEDs responsive to the DC power source, and a controller configured to control the power converter to supply the second DC drive current when the detected voltage level of the mains voltage drops below a threshold.

[0013] In one embodiment, the controller is further configured to control the power converter to adjust the second DC drive current to change a brightness of the LEDs responsive to a detected level of ambient light. According to one optional feature of this embodiment, the second network further comprises a photocell configured to detect the level of the ambient light. According to another optional feature of this embodiment, the photocell is configured to be removably connectable to the second network.

[0014] According to a further embodiment, the DC power source comprises a battery plant, e.g. battery plant supplying -48V DC.

[0015] According to a still further embodiment, the power converter includes a DC-DC buck boost LED driver.

[0016] According to another embodiment, the controller is further configured to adjust the second DC drive current to change a brightness of the LEDs when a voltage level of the DC power source drops below a second threshold.

[0017] According to yet another embodiment, the second network further comprises a regulator configured to convert an output of the power converter, and to provide the converted output to power the controller when the detected voltage level of the mains voltage drops below the threshold.

[0018] Generally, in yet another aspect, the invention relates to a method of providing lighting that includes: providing a first DC drive current for driving a plurality of light emitting diodes (LEDs) responsive to mains voltage, and providing a second DC drive current for driving the plurality of LEDs responsive to a DC power source when a detected level of the mains voltage drops below a threshold.

[0019] According to one embodiment, the method further includes adjusting the second DC drive current to change a brightness of the LEDs responsive to a detected level of ambient light.

[0020] According to another embodiment, the DC power source includes a battery plant that supplies -48V DC.

[0021] According to a further embodiment, the method further includes adjusting the second DC drive current to change a brightness of the LEDs when a voltage level of the DC power source drops below a second threshold.

[0022] As used herein for purposes of the present disclosure, the term "LED" should be understood to include any electroluminescent diode or other type of carrier injection/junction- based system that is capable of generating radiation in response to an electric signal. Thus, the term LED includes, but is not limited to, various semiconductor-based structures that emit light in response to current, light emitting polymers, organic light emitting diodes (OLEDs), electroluminescent strips, and the like. In particular, the term LED refers to light emitting diodes of all types (including semi-conductor and organic light emitting diodes) that may be configured to generate radiation in one or more of the infrared spectrum, ultraviolet spectrum, and various portions of the visible spectrum (generally including radiation wavelengths from approximately 400 nanometers to approximately 700 nanometers). [0023] It should also be understood that the term LED does not limit the physical and/or electrical package type of an LED. For example, as discussed above, an LED may refer to a single light emitting device having multiple dies that are configured to respectively emit different spectra of radiation (e.g., that may or may not be individually controllable). Also, an LED may be associated with a phosphor that is considered as an integral part of the LED (e.g., some types of white LEDs).

[0024] The term "light source" should be understood to refer to any one or more of a variety of radiation sources, including, but not limited to, LED-based sources (including one or more LEDs as defined above), incandescent sources (e.g., filament lamps, halogen lamps), fluorescent sources, phosphorescent sources, high-intensity discharge sources (e.g., sodium vapor, mercury vapor, and metal halide lamps), lasers, other types of electroluminescent sources, pyro-luminescent sources (e.g., flames), candle-luminescent sources (e.g., gas mantles, carbon arc radiation sources), photo-luminescent sources (e.g., gaseous discharge sources), cathode luminescent sources using electronic satiation, galvano-luminescent sources, crystallo- luminescent sources, kine-luminescent sources, thermo-luminescent sources, triboluminescent sources, sonoluminescent sources, radioluminescent sources, and luminescent polymers.

[0025] A "lighting driver" is used herein to refer to an apparatus that supplies electrical power to one or more light sources in a format to cause the light sources to emit light. In particular, a lighting driver may receive electrical power in a first format (e.g., AC Mains power; a fixed DC voltage; etc.) and supply power in a second format that is tailored to the

requirements of the light source(s) (e.g., LED light source(s)) that it drives.

[0026] The term "lighting module" is used herein to refer to a module, which may include a circuit board (e.g., a printed circuit board) having one or more light sources mounted thereon, as well as one or more associated electronic components, such as sensors, current sources, etc., and which is configured to be connected to a lighting driver. Such lighting modules may be plugged into slots in a lighting fixture, or a motherboard, on which the lighting driver may be provided. The term "LED module" is used herein to refer to a module, which may include a circuit board (e.g., a printed circuit board) having one or more LEDs mounted thereon, as well as one or more associated electronic components, such as sensors, current sources, etc., and which is configured to be connected to a lighting driver. Such lighting modules may be plugged into slots in a lighting fixture, or a motherboard, on which the lighting driver may be provided.

[0027] The term "lighting unit" is used herein to refer to an apparatus including one or more light sources of same or different types. A given lighting unit may have any one of a variety of mounting arrangements for the light source(s), enclosure/housing arrangements and shapes, and/or electrical and mechanical connection configurations. Additionally, a given lighting unit optionally may be associated with (e.g., include, be coupled to and/or packaged together with) various other components (e.g., control circuitry; a lighting driver) relating to the operation of the light source(s). An "LED-based lighting unit" refers to a lighting unit that includes one or more LED-based light sources as discussed above, alone or in combination with other non LED- based light sources.

[0028] The terms "lighting fixture" and "luminaire" are used herein interchangeably to refer to an implementation or arrangement of one or more lighting units in a particular form factor, assembly, or package, and may be associated with (e.g., include, be coupled to and/or packaged together with) other components.

[0029] The term "controller" is used herein generally to describe various apparatus relating to the operation of one or more light sources. A controller can be implemented in numerous ways (e.g., such as with dedicated hardware) to perform various functions discussed herein. A "processor" is one example of a controller which employs one or more microprocessors that may be programmed using software (e.g., microcode) to perform various functions discussed herein. A controller may be implemented with or without employing a processor, and also may be implemented as a combination of dedicated hardware to perform some functions and a processor (e.g., one or more programmed microprocessors and associated circuitry) to perform other functions. Examples of controller components that may be employed in various embodiments of the present disclosure include, but are not limited to, conventional microprocessors, application specific integrated circuits (ASICs), and field-programmable gate arrays (FPGAs). [0030] It will be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element or intervening elements may be present. In contrast, when an element is referred to as being "directly connected" or "directly coupled" to another element, there are no intervening elements present.

[0031] It should be appreciated that all combinations of the foregoing concepts and additional concepts discussed in greater detail below (provided such concepts are not mutually inconsistent) are contemplated as being part of the inventive subject matter disclosed herein. In particular, all combinations of claimed subject matter appearing at the end of this disclosure are contemplated as being part of the inventive subject matter disclosed herein. It should also be appreciated that terminology explicitly employed herein that also may appear in any disclosure incorporated by reference should be accorded a meaning most consistent with the particular concepts disclosed herein.

Brief Description of the Drawings

[0032] In the drawings, like reference characters generally refer to the same parts throughout the different views. Also, the drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention.

[0033] FIG. 1 illustrates an example embodiment of an LED-based lighting system.

[0034] FIG. 2 illustrates a DC-DC buck boost LED driver as an example embodiment of a DC- DC power converter.

[0035] FIG. 3 is a schematic diagram of an embodiment of a mains detector of lighting system shown in FIG. 1.

[0036] FIG. 4 illustrates another example embodiment of an LED-based lighting system.

Detailed Description

[0037] As discussed above, it is desirable to provide a lighting driver, and a lighting system using the lighting driver, having reduced size, complexity and cost. It is further desirable to provide a lighting driver, and a lighting system using the lighting driver, that can adaptively change brightness of LED-based light sources.

[0038] FIG. 1 illustrates an example embodiment of lighting system 10, which includes battery plant (DC power source) 110, lighting driver 120 and a plurality of light emitting diode (LED) strings 140-1 ~ 140-n, each of the LED strings 140-1 ~ 140-n including a plurality of LEDs 142. In some cases, each LED string 140-1 ~ 140-n may include a single LED 142, or any number of LEDs 142. Battery plant 110 supplies -48V DC to lighting driver 120. Lighting driver 120 is also connected to the AC mains voltage for detection of the AC mains voltage. In some embodiments, battery plant 110 and lighting driver 120 may be centrally located in a building or on a specific floor of the building, and LED strings 140-1 ~ 140-n may be located in the building or on the specific floor of the building remotely from the central location.

[0039] Lighting driver 120 as shown in FIG. 1 includes DC-DC power converter 122, controller 124 and mains detector 126. DC-DC power converter 122 is connected to receive the -48V DC output from battery plant 110, and is configured to convert the -48V DC to a maximum +24V DC which is supplied to LED strings 140-1 ~ 140-n. Mains detector 126 detects a voltage level of the AC mains voltage, and provides a signal indicative of the voltage level of the AC mains voltage to controller 124. In an embodiment, DC-DC power converter 122 may be a DC-DC buck boost LED driver.

[0040] In general, in an embodiment, controller 124 controls DC-DC power converter 122 to provide a DC drive current to drive LED strings 140-1 ~ 140-n, responsive to the detected voltage level of the AC mains voltage as provided by mains detector 126. In some

embodiments, controller 124 controls DC-DC power converter 122 responsive to the detected voltage level of the AC mains voltage, to provide a DC drive current to drive LED strings 140-1 ~ 140-n when the AC mains voltage is interrupted or lost and/or when the AC mains voltage drops below a threshold. As also shown in FIG. 1, a feedback loop may be included to provide a feedback signal from LED strings 140-1 ~ 140-n to DC-DC power converter 122. Controller 124 may use the feedback signal to adjust DC drive current to obtain a desired luminance from LEDs 142. As also shown in FIG. 1, the cathodes of the last LEDs 142 in LED strings 140-1 ~ 140-n are connected to ground through resistor 132. [0041] In an embodiment, photocell 130 may be connected to lighting driver 120, and lighting driver 120 may further include brightness controller 128. Photocell 130 may be a pluggable unit removably connectable directly to lighting driver 120. In some embodiments, photocell 130 may be located remotely from lighting driver 120 and connected to lighting driver 120 by wiring for example. Photocell 130 is configured to detect a level of ambient light.

Brightness controller 128 may include a fixed value resistor (not shown) connected in series with photocell 130 and connected to the power supply that feeds controller 124. Photocell 130 and the fixed value resistor as thus connected may be configured as a voltage divider that provides a divided voltage responsive to the detected ambient light. Controller 124 may include an internal analog-to-digital converter (ADC) (not shown) configured to sample the divided voltage provided by brightness controller 128. Controller 124 may control DC-DC power converter 122 to adjust the DC drive current provided to LED strings 140-1 ~ 140-n, to change a brightness of LED strings 140-1 ~ 140-n responsive to the detected level of ambient light. When the detected level of ambient light is above a predetermined level, controller 124 may control DC-DC power converter 122 to adjust the DC drive current to conserve battery plant 110. For example, controller 124 may control DC-DC power converter 122 to turn off LED strings 140-1 ~ 140-n when the detected level of ambient light is high enough that lighting is unnecessary. In a further embodiment, controller 124 may control DC-DC power converter 122 to dim LED strings 140-1 ~ 140-n when the detected level of ambient light is at a level such that less than full lighting is needed.

[0042] In a further embodiment, controller 124 may be configured to sense when the voltage level of the DC power supplied from battery plant 110 to DC-DC power converter 122 is reduced from -48V DC to within a range of about -47V DC to -39V DC, for example. Upon determination of a drop in the voltage level of battery plant 110 below the -48V DC threshold (second threshold), controller 124 may control DC-DC power converter 122 to adjust the DC drive current provided to LED strings 140-1 ~ 140-n, to change a brightness of LED strings 140-1 ~ 140-n. Controller 124 may apply a dimming curve to control DC-DC power converter 122. The dimming curve may be stored internally within controller 124, or may be stored in a separate memory (not shown) within lighting driver 120 external of controller 124. In an embodiment, the dimming curve may be applied such that when the sensed voltage level of battery plant 110 is -48V DC, controller 124 may control DC-DC power converter 122 to provide a DC drive current that drives LEDs 142 to 100% brightness. The dimming curve may be further applied such that when the sensed voltage level of battery plant 110 drops below -48V DC, controller 124 may control DC-DC power converter 122 to provide a DC drive current that linearly dim LEDs 142 down to 30% brightness at -39V DC. Controller 124 may thereafter control DC-DC power converter 122 to maintain LEDs 142 in the thus dimmed state. Upon subsequent detection of normal AC mains voltage by mains detector 126, controller 124 may control DC-DC power converter 122 to disable the DC drive current to turn off LED strings 140-1 ~ 140-n. Adaptive control of the brightness of LEDs 142 in this manner optimizes energy efficiency of lighting system 10, and prolongs the life of battery plant 110.

[0043] FIG. 2 illustrates a DC-DC buck boost LED driver 222 as an example embodiment of DC-DC power converter 122. DC-DC buck boost LED driver 222 converts the -48V DC output from battery plant 110 shown in FIG. 1, to a maximum +24V DC that is supplied to LED strings 140-1 ~ 140-n. The resultant voltage applied to LED strings 140-l~140-n is determined by the V- I (voltage verses current) characteristics of LEDs 142. During normal operation, controller 124 will regulate the string current. When LED strings 140-1 ~ 140-n are disconnected, the output voltage of DC-DC buck boost LED driver 222 will be limited by controller 124 to +24V DC to protect the user and the system. DC-DC buck boost LED driver 222 includes filtering capacitors CI and C2, transistor (MOSFET) Ql, inductor LI, and diode Dl. Filtering capacitor CI prevents injection of noise from battery plant 110 into DC-DC buck boost LED driver 222. Transistor Ql is turned on/off responsive to an output of controller 124 that is applied to a gate of transistor Ql. In an embodiment, controller 124 adjusts the DC drive current output from DC-DC buck boost LED driver 222 by controlling the on/off duty cycle of transistor Ql. Inductor LI is configured to store the energy provided from battery plant 110 when transistor Ql is turned on, and to subsequently output the current through diode Dl and filtering capacitor C2 as the DC drive current when transistor Ql is turned off. Diode Dl connects inductor LI to the output of DC-DC buck boost LED driver 222. Filtering capacitor C2 prevents injection of switching frequency ripple and/or other noise into the output of DC-DC buck boost LED driver 222. [0044] Of note, the output of DC-DC buck boost LED driver 222 will not always be +24V. In general, an LED driver is usually specified to a maximum voltage. In this embodiment, DC-DC buck boost LED driver 222 is specified to +24V. During normal operation, DC-DC buck boost LED driver 222 will be in a current control mode, meaning that DC-DC buck boost LED driver 222 will regulate the LED string current. In this case, LEDs 142 determine the output voltage of DC-DC buck boost LED driver 222. For example, in the case that LED string current is controlled by DC- DC buck boost LED driver 222 to be 700mA, the voltage per LED 142 would be about 3.1V. In the case that the LED string current is dimmed by DC-DC buck boost LED driver 222 to 350mA for example, the voltage per LED 142 would be about 2.7V. On the other hand, when the LED string current cannot be controlled such as during an open load condition when LED strings 140-1 ~ 140-n are disconnected, DC-DC buck boost LED driver 222 will operate in a voltage control mode to limit the voltage to +24V.

[0045] FIG. 3 is a schematic diagram of mains detector 126 which may be used in lighting system 10 shown in FIG. 1. Mains detector 126 may be used to power controller 124 according to an example embodiment. Mains detector 126 as shown in FIG. 2 includes mains detection unit 340, isolated DC-DC power supply 350, auxiliary supply 360, and linear regulator 370.

Isolated DC-DC power supply 350 is connected to receive rectified DC mains voltage at an input thereof. Isolated DC-DC power supply 350 is configured to provide a DC voltage from diode D12 to linear regulator 370 via diode D14 and resistor R13, when the AC mains voltage is active. The AC mains voltage may be rectified by a diode bridge (not shown) to provide the rectified DC mains voltage to isolated DC-DC power supply 350. Integrated circuit (IC) chip 352 controls operation of isolated DC-DC power supply 350 so as to convert the rectified DC mains voltage into a DC voltage suitable for powering controller 124. Mains detection unit 340 is configured to detect a voltage level of the AC mains voltage responsive to an output of isolated DC-DC power supply 350. Mains detection unit 340 provides a signal indicative of the voltage level of the AC mains voltage to controller 124 from resistor Rll. Auxiliary supply 360 is connected to receive and correspondingly provide the power from DC-DC power converter 122 to linear regulator 370 via resistor R13, when the AC mains voltage is inactive. Linear regulator 370 is configured to clamp the DC voltage from isolated DC-DC power supply 350 and/or the DC LED string voltage from DC-DC power converter 122 to 3.3V DC, and to provide the clamped 3.3V DC as an output to power controller 124.

[0046] FIG. 4 illustrates another example embodiment of a lighting system. Lighting system 40 shown in FIG. 4 includes battery plant 410 (DC power source), lighting driver 420, and a plurality of LED modules 440-1 ~ 440-n. Lighting driver 420 is connected to the AC mains voltage. Battery plant 410 and lighting driver 420 may be centrally located in a building or on a specific floor of the building, and LED modules 440-1 ~ 440-n may be located in the building or on the specific floor of the building remotely from the central location. Lighting driver 420 includes DC-DC power converter 422, controller 424 and mains detector 426. DC-DC power converter 422 is connected to receive the -48V DC output from battery plant 410, and is configured to convert the -48V DC to a constant DC voltage which is supplied to LED modules 440-1 ~ 440-n. Mains detector 426 detects a voltage level of the AC mains voltage, and provides a signal indicative of the voltage level of the AC mains voltage to controller 424. In an embodiment, DC-DC power converter 422 may be a DC-DC buck boost LED driver. In an embodiment, photocell 430 may be connected to lighting driver 420, and lighting driver 420 may further include brightness controller 428. Photocell 430 may be a pluggable unit removably connectable directly to lighting driver 420. In some embodiments photocell 430 may be located remotely from lighting driver 420, and may be connected to lighting driver 420 by wiring, for example. Resistor 432 is connected between LED modules 440-1 ~ 440-n and ground. Battery plant 410, lighting driver 420 and photocell 430 of lighting system 40 are configured and operate similarly as battery plant 110, lighting driver 120 and photocell 130 of lighting system 10 shown in FIG. 1, and further detailed description of such similar configuration and function is omitted.

[0047] LED modules 440-1 ~ 440-n of lighting system 40 may each include one or more strings of LEDs such as shown in lighting system 10 of FIG. 1. LED modules 440-1 ~ 440-n are connected to receive power responsive to the AC mains voltage. In an embodiment, switches (not shown) may be included between the AC mains and LED modules 440-1 ~ 440-n to turn LED modules 440-1 ~ 440-n on/off. LED modules 440-1 ~ 440-n may further include AC-DC converters and DC-DC converters to power the LED strings responsive to the AC mains. The corresponding switches, the AC-DC converters and the DC-DC converters may collectively be characterized as a first network connected to the AC mains , the first network being configured to provide the power (first DC drive current) for driving the LEDs of LED modules 440-1 ~ 440-n, when the AC mains are active. LED modules 440-1 ~ 440-n are also connected to receive a second DC drive current from DC-DC power converter 422 responsive to battery plant 410 (DC power source). The second DC drive current from DC-DC power converter 422 may be directly connected to the LEDs of LED modules 440-1 ~ 440-n. Battery plant 410, lighting driver 420 including DC-DC power converter 422, and photocell 430 may collectively be characterized as a second network configured to provide a second DC drive current for driving the LEDs of LED modules 440-1 ~ 440-n, when the AC mains are inactive.

[0048] In an embodiment, lighting system 40 of FIG. 4 may be constructed by modifying an existing general lighting system including LED modules 440-1 ~ 440-n and AC mains voltage as a first network, to further include battery plant 410, lighting driver 420 and photocell 430 as a second network to provide safety lighting. The second DC drive current provided by DC-DC power converter 422 may be directly connected to the LEDs of LED modules 440-1 ~ 440-n. A safety lighting system of reduced size, complexity and cost may thus be configured to provide uninterrupted light by modifying an existing general lighting system.

[0049] As described, battery plant 110 of lighting system 10 shown in FIG. 1 is configured to provide -48V DC, which would be suitable for a battery plant used to power a telecom facility for example. In other embodiments, battery plant 110 may be configured to provide -36V DC or some other DC voltage, which would in turn be converted by DC-DC power converter 122 to a constant DC voltage for supply to LED strings 140-1 ~ 140-n.

[0050] It should be understood that although, to provide a concrete illustration, example embodiments have been described above in the context of LED modules that include LED light sources, the concepts described above need not be so limited, and can be applied to lighting drivers supplying power to lighting modules that include other types of light sources and which supply an identification current back to the lighting module to facilitate adjustment by the lighting driver of the level of power which it supplies in response, for example, to the number of lighting modules to which it is connected. [0051] While several inventive embodiments have been described and illustrated herein, those of ordinary skill in the art will readily envision a variety of other means and/or structures for performing the function and/or obtaining the results and/or one or more of the advantages described herein, and each of such variations and/or modifications is deemed to be within the scope of the inventive embodiments described herein. More generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary and that the actual parameters, dimensions, materials, and/or configurations will depend upon the specific application or applications for which the inventive teachings is/are used. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific inventive embodiments described herein. It is, therefore, to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended claims and equivalents thereto, inventive embodiments may be practiced otherwise than as specifically described and claimed. Inventive embodiments of the present disclosure are directed to each individual feature, system, article, material, kit, and/or method described herein. In addition, any combination of two or more such features, systems, articles, materials, kits, and/or methods, if such features, systems, articles, materials, kits, and/or methods are not mutually inconsistent, is included within the inventive scope of the present disclosure.

[0052] All definitions, as defined and used herein, should be understood to control over dictionary definitions, definitions in documents incorporated by reference, and/or ordinary meanings of the defined terms.

[0053] The indefinite articles "a" and "an," as used herein in the specification and in the claims, unless clearly indicated to the contrary, should be understood to mean "at least one."

[0054] The phrase "and/or," as used herein in the specification and in the claims, should be understood to mean "either or both" of the elements so conjoined, i.e., elements that are conjunctively present in some cases and disjunctively present in other cases. Multiple elements listed with "and/or" should be construed in the same fashion, i.e., "one or more" of the elements so conjoined. Other elements may optionally be present other than the elements specifically identified by the "and/or" clause, whether related or unrelated to those elements specifically identified.

[0055] As used herein in the specification and in the claims, the phrase "at least one," in reference to a list of one or more elements, should be understood to mean at least one element selected from any one or more of the elements in the list of elements, but not necessarily including at least one of each and every element specifically listed within the list of elements and not excluding any combinations of elements in the list of elements. This definition also allows that elements may optionally be present other than the elements specifically identified within the list of elements to which the phrase "at least one" refers, whether related or unrelated to those elements specifically identified. It should also be understood that, unless clearly indicated to the contrary, in any methods claimed herein that include more than one step or act, the order of the steps or acts of the method is not necessarily limited to the order in which the steps or acts of the method are recited. Also, reference numerals appearing in the claims in parentheses, if any, are provided merely for convenience and should not be construed as limiting the claims in any way.

Claims

CLAIMS:

1. A lighting driver, comprising:

a detector configured to detect a voltage level of mains voltage;

a power converter connected to a DC power source and configured to provide a DC drive current for driving a plurality of light emitting diodes (LEDs) responsive to the DC power source; and

a controller configured to control the power converter to supply the DC drive current when the detected voltage level of the mains voltage drops below a threshold.

2. The lighting driver of claim \, wherein the controller is further configured to control the power converter to adjust the DC drive current to change a brightness of the LEDs responsive to a detected level of ambient light.

3. The lighting driver of claim 2, further comprising a photocell configured to detect the level of the ambient light.

4. The lighting driver of claim 3, wherein the photocell is configured to be removably connectable to the lighting driver.

5. The lighting driver of claim 1, wherein the DC power source comprises a battery plant.

6. The lighting driver of claim 5, wherein the battery plant supplies -48V DC.

7. The lighting driver of claim \, wherein the power converter comprises a DC-DC buck boost LED driver.

8. The lighting driver of claim 1, wherein the controller is further configured to adjust the DC drive current to change a brightness of the LEDs when a voltage level of the DC power source drops below a second threshold.

9. The lighting driver of claim 1, further comprising a regulator configured to convert an output of the power converter, and to provide the converted output to power the controller when the detected voltage level of the mains voltage drops below the threshold.

10. A lighting system, comprising:

a plurality of light emitting diodes (LEDs);

a first network connected to mains voltage and configured to provide a first DC drive current for driving the plurality of LEDs responsive to the mains voltage; and

a second network comprising

a detector configured to detect a voltage level of the mains voltage, a power converter connected to a DC power source and configured to provide a

DC drive current for driving the plurality of LEDs responsive to the DC power source, and a controller configured to control the power converter to supply the second DC drive current when the detected voltage level of the mains voltage drops below a threshold.

11. The lighting system of claim 10, wherein the controller is further configured to control the power converter to adjust the second DC drive current to change a brightness of the LEDs responsive to a detected level of ambient light.

12. The lighting system of claim 11, wherein the second network further comprises a photocell configured to detect the level of the ambient light.

13. The lighting system of claim 12, wherein the photocell is configured to be removably connectable to the second network.

14. The lighting system of claim 10, wherein the DC power source comprises a battery plant.

15. The lighting system of claim 10, wherein the power converter comprises a DC-DC buck boost LED driver.

16. The lighting system of claim 10, wherein the controller is further configured to adjust the second DC drive current to change a brightness of the LEDs when a voltage level of the DC power source drops below a second threshold.

17. The lighting system of claim 10, wherein the second network further comprises a regulator configured to convert an output of the power converter, and to provide the converted output to power the controller when the detected voltage level of the mains voltage drops below the threshold.

18. A method of providing lighting, the method comprising:

providing a first DC drive current for driving a plurality of light emitting diodes (LEDs) responsive to mains voltage; and

providing a second DC drive current for driving the plurality of LEDs responsive to a DC power source when a detected level of the mains voltage drops below a threshold.

19. The method of claim 18, further comprising adjusting the second DC drive current to change a brightness of the LEDs responsive to a detected level of ambient light

20. The method of claim 18, further comprising adjusting the second DC drive current to change a brightness of the LEDs when a voltage level of the DC power source drops below a second threshold.