CN117642958A - Step-down module for emergency power system - Google Patents

Abstract

A buck module (10) for an emergency power system (100) is disclosed. The buck module (10) comprises a buck circuit (11) to which an AC power supply (40) having an input voltage higher than 277VAC may be connected, the buck circuit being arranged to convert the input voltage to an output voltage in the range 120 to 277 VAC. The sensing module 14 is arranged to detect a status of an emergency driver relay (21) from an emergency lighting fixture (20). The normal operation mode is activated when the emergency driver relay (21) is closed, and the emergency operation mode is activated when the emergency driver relay (21) is open. The normal operation mode is when the AC power supply (40) supplies AC power to the step-down circuit (11), and the emergency operation mode is when the AC power supply (40) does not supply AC power. The control relay (13) is arranged to connect or disconnect an AC power source (40) to the emergency lighting fixture (20). The controller (12) is arranged to control the control relay in dependence on the status of the emergency driver relay detected by the sensing module. In the normal operating mode, the control relay connects the AC power source (40) to the emergency lighting fixture (20), and in the emergency operating mode, the control relay disconnects the AC power source (40) from the emergency lighting fixture (20). The emergency lighting fixture (20) may be an LED-based lighting device.

Description

Step-down module for emergency power system

Technical Field

The present invention relates to systems and devices for emergency power and lighting systems, and more particularly to a buck module for an emergency LED lighting device.

Background

When a power failure/outage occurs, there is a need for an emergency backup power system to provide temporary emergency power. Conventional backup power systems may include an uninterruptible power supply (or UPS) to provide emergency power to a load in the event of a failure of an input power source (e.g., mains power).

Emergency lighting refers to lighting that is activated upon a power failure. One purpose of emergency lighting is to allow occupants within a building to safely leave the building in the event of a power failure or in other emergency situations. Within a building, emergency lighting is typically provided by emergency lighting devices (e.g., LEDs or fluorescent lights) that are powered by an emergency backup power system or internal battery. The emergency backup power may be from an emergency battery.

In a conventional emergency light power supply, the emergency light power supply is in a standby state when the commercial power supply is turned on (or activated). When the commercial power source is de-energized (e.g., due to a fault), the relay turns on the emergency battery circuit to power one or more emergency lighting devices. When the commercial power supply is again activated, the relay will shut off the emergency battery power provided to the emergency lighting device and the emergency light power supply returns to a standby (battery charging) state.

As mentioned above, the emergency lighting device may also include an internal battery. For example, a typical emergency LED driver charges an internal battery from an AC mains supply. AC mains is typically in the 120 to 277VAC input voltage range. However, in some applications, the available AC voltage is higher than 277VAC (e.g., 347VAC in canada, and 480VAC in some industrial/warehouse applications). To accommodate such higher AC voltages, relatively expensive and bulky step-down transformers are required to step down these higher AC voltages to a voltage in the 120 to 277VAC input voltage range to be compatible with existing emergency LED drivers or other emergency equipment, such as Uninterruptible Power Supplies (UPS) that may also be used to provide emergency power.

DE 112019003891 relates to a network connection system, a connection control device, and a network connection method, which can prevent cutting off of power supply at the time of power restoration. A grid connection system for a power grid, comprising: a storage battery; a power conversion device that converts power from the storage battery into AC power; and a connection control device that supplies power from the utility power source to the load, and supplies power from the power conversion device to the load when the utility power source fails. When the utility power is restored, the connection control apparatus starts supplying power from the utility power to the load, and after starting supplying power from the utility power to the load, stops supplying power from the power conversion apparatus to the load.

US 8686662 B1 relates to exit and exit lighting, emergency lighting or emergency light fixtures having an internal supercapacitor power supply that is recharged using an interleaving power-up process after power down. For example, once the emergency light fixture detects a power-on transition from power not available on the power source to power available from the power source, the light fixture waits for a predetermined time to recharge the supercapacitor based on the charging time delay value. The predetermined time may be selected to be unique to one or several emergency light fixtures in order to allocate the combined peak power demand of the light fixtures. After the predetermined time has expired, the supercapacitor is electrically coupled to a power source to recharge the supercapacitor.

There is a need to provide a cost-effective and/or improved system to allow charging from a higher input AC voltage.

This document describes systems and methods that aim to address at least some of the above problems and/or other problems described below.

Disclosure of Invention

Aspects and embodiments of the present invention address the above-described shortcomings.

One aspect of the present invention relates to an improved interface for reducing a higher input AC voltage (e.g., above 277 VAC) to 120-277VAC for compatibility with typical emergency lighting devices (e.g., emergency LED drivers).

In some aspects of the invention, this is accomplished by electronically reducing the higher input AC voltage and providing control to coordinate proper functioning of the normal LED driver and the emergency LED driver in both standby and active modes of operation.

Various embodiments and aspects of the present invention may include: a buck circuit to achieve the proper voltage and current for emergency battery charging (i.e., standby mode) and control within the emergency LED driver, a control relay to switch to normal (non-emergency) or emergency LED driver mode, a sensing circuit to monitor the status of the emergency control relay, and a control circuit to coordinate switching between normal and emergency modes.

Other aspects of the invention utilize a multi-tap low frequency transformer and an AC coil relay with high voltage contacts. This configuration allows the AC coil relay to directly control the coils of the emergency control relay. This will reduce the number of components of the buck interface.

One embodiment of the invention relates to a buck module for an emergency power system. The buck module includes a buck circuit to which an AC power source having an input voltage higher than 277VAC may be connected. The step-down circuit is arranged to convert an input voltage to an output voltage in the range of 120 to 277 VAC. The sensing module is for detecting a status of an emergency driver relay from the emergency lighting fixture. The normal operation mode is active when the emergency drive relay is closed and the emergency operation mode is active when the emergency drive relay is open. The normal operation mode is when the AC power supply supplies AC power to the step-down circuit, and the emergency operation mode is when the AC power supply does not supply AC power. The control relay is arranged to connect or disconnect the AC power source to the emergency lighting fixture. The control circuit switches the control relay in dependence on the status of the emergency driver relay detected by the sensing module. In the normal mode of operation, the control relay connects the AC power source to the emergency lighting fixture, and in the emergency mode of operation, the control relay disconnects the AC power source from the emergency lighting fixture. The emergency lighting fixture may be an LED-based lighting device.

Another embodiment of the invention relates to a step-down module for an emergency power system, the step-down module comprising a transformer arranged to receive an input AC voltage higher than an AC voltage required for proper charging of an emergency lighting device and to convert the input AC voltage to the AC voltage required for the emergency lighting device. The AC coil relay is controlled by an emergency relay in the emergency lighting device. The emergency lighting fixture receives battery charging power from the transformer when the emergency driver relay is closed, and uses internal battery power when the emergency driver relay is open, and the AC coil relay disconnects the input AC voltage from the emergency lighting device. The transformer may be a multi-tap low frequency transformer.

The present invention enables an emergency lighting system to be applied to any large scale lighting application without changing the available AC power source and can be used with existing emergency lighting devices that require commercial AC power (e.g., 120 or 277 VAC) for emergency battery charging purposes.

For example, the lighting system may include a luminaire having a high voltage AC driver operating in a high voltage AC range (e.g., 277/347/480 VAC) and an emergency LED driver operating in a commercial AC voltage range (e.g., 120 VAC). According to aspects of the invention, the buck module feeds switched AC mains (277/247/480 VAC) to the high AC driver, and the buck circuit provides charging current fed to the emergency LED driver for charging the internal battery. The buck module then monitors the switched AC mains to determine whether the luminaire is on or off, and can determine power loss based on monitoring the non-switched AC mains. The buck module further monitors the status of the emergency LED driver to determine which mode the emergency LED driver is in, because it can switch from the normal operating mode to the emergency operating mode when there is a loss of AC mains or the user presses the test mode button. In the event of a loss of power from the AC mains or activation of the test mode, the buck module disconnects the high voltage AC driver from the AC mains and feeds directly from the emergency luminaire driver using the battery. In the normal operation mode, the switched AC mains supplies power to the high voltage AC LED driver, and the commercial AC voltage from the step-down circuit charges the battery.

It should be appreciated that all combinations of the foregoing concepts and additional concepts discussed in more detail below (where 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 will also be appreciated that terms explicitly used herein, which may also appear in any disclosure incorporated by reference, should be given the meanings most consistent with the specific concepts disclosed herein.

Drawings

Further details, aspects and embodiments of the invention will be described, by way of example only, with reference to the accompanying drawings. Elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. In the drawings, elements corresponding to elements already described may have the same reference numerals. In the drawings of which there are shown,

FIG. 1 schematically illustrates elements of an emergency lighting system according to one embodiment of the invention, an

Fig. 2 schematically illustrates elements of an emergency lighting system according to another embodiment of the invention.

Detailed Description

While this invention is susceptible of embodiment in many different forms, there is shown in the drawings and will herein be described in detail one or more specific embodiments, with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the specific embodiments illustrated and described.

Hereinafter, elements of the embodiments are described in operation for the sake of understanding. However, it will be clear that the various elements are arranged to perform the functions described as being performed by them.

The term "LED" is understood to include any electroluminescent diode or other type of carrier injection/junction based system capable of generating radiation in response to an electrical signal. Thus, the term LED includes, but is not limited to, various semiconductor-based structures that emit light in response to an electrical current, light emitting polymers, organic Light Emitting Diodes (OLEDs), electroluminescent strips, and the like. In particular, the term LED refers to all types of light emitting diodes (including semiconductor light emitting diodes and organic light emitting diodes) that may be configured to generate radiation in one or more of the various portions of the infrared spectrum, the ultraviolet spectrum, and the visible spectrum (typically including radiation wavelengths from about 400 nanometers to about 700 nanometers). Some examples of LEDs include, but are not limited to, various types of infrared LEDs, ultraviolet LEDs, red LEDs, blue LEDs, green LEDs, yellow LEDs, amber LEDs, orange LEDs, and white LEDs (discussed further below). It should also be appreciated that LEDs may be configured and/or controlled to generate radiation having various bandwidths (e.g., full width half maximum or FWHM) for a given spectrum (e.g., narrow bandwidth, wide bandwidth), as well as various dominant wavelengths within a given general color classification.

It should also be understood that the term LED does not limit the physical and/or electrical packaging type of the LED. For example, as discussed above, an LED may refer to a single light emitting device having multiple dies configured to emit radiation of different spectrums, respectively (e.g., which may or may not be individually controllable). Further, LEDs may be associated with phosphors that are considered to be part of the LED (e.g., some types of white LEDs). In general, the term LED may refer to packaged LEDs, non-packaged LEDs, surface mount LEDs, chip-on-board LEDs, T-package mounted LEDs, radial package LEDs, power package LEDs, LEDs that include some type of encapsulation and/or optical element (e.g., a diffusing lens), and the like.

The term "light source" is 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., incandescent lamps, halogen lamps), fluorescent sources, phosphor sources, high intensity discharge sources (e.g., sodium vapor, mercury vapor, and metal halide lamps), lasers, other types of electroluminescent sources, high temperature light sources (e.g., flames), candle light sources (e.g., gas masks, carbon arc radiation sources), photoluminescent sources (e.g., gas discharge sources), cathode light sources using electronic saturation, electric current light sources, crystal light sources, sports light sources, thermal light sources, triboluminescent sources, acoustic light sources, radiant light sources, and luminescent polymers.

The term "lighting fixture or lighting device" is used herein to refer to an implementation or arrangement of one or more lighting units in a particular form factor, component, or package. The term "lighting unit" as used herein refers to a device comprising one or more light sources of the same or different types. A given lighting unit may have any of a variety of mounting arrangements for the light source(s), housing/case arrangements and shapes, and/or electrical and mechanical connection configurations. Additionally, a given lighting unit may optionally be associated with (e.g., include, be coupled to, and/or be packaged together with) various other components (e.g., control circuitry) related to the operation of the light source(s). "LED-based lighting unit" refers to a lighting unit comprising one or more LED-based light sources as discussed above, alone or in combination with other non-LED-based light sources.

For purposes of this disclosure, the term "load" as used herein refers to an electronic device that draws current from a power source. Examples of loads may include an internal battery of an emergency lighting device, a UPS, a lighting device such as a resistive incandescent lamp, a halogen lamp, a compact fluorescent Light Emitting Diode (LED), and a lamp driver or other device that requires AC power as an input.

Furthermore, the invention is not limited to the embodiments, and the invention lies in each and every novel feature or combination of features described herein or in mutually different dependent claims.

FIG. 1 illustrates an example of an Emergency Lighting System (ELS) 100 according to one embodiment. The ELS100 includes a buck module 10, one or more emergency lighting fixtures 20 including an emergency driver relay 21. In this configuration, the emergency lighting device 20 is a load. For example, one or more of the emergency lighting fixtures 20 may be LED-based lighting units. A typical LED-based lighting unit for emergency lighting applications includes an emergency LED driver that requires an AC voltage input in the range of 120 to 277VAC (via an emergency LED driver charger input (typically via black and white contact connections)). The buck module 10 is connected to an input AC power source 40 (not shown). In this configuration, the AC power source is a switchless AC main input to the buck module 10. The input AC power source 40 may provide an AC voltage above 120VAC, and in particular in the range 277 to 480VAC.

The step-down module 10 includes a step-down circuit 11, a controller 12, a control relay 13, and a sensing module 14. The terms "controller," "circuit," or "module" are generally used herein to describe a structure or circuit that may be implemented in a variety of ways (e.g., such as with dedicated hardware and/or software) to perform the various functions discussed herein. The structure or circuit may include, for example, transistors, diodes, resistors, capacitors, integrated Circuits (ICs), and processors. A "processor" is one example of a controller (or central component of a controller) that employs one or more microprocessors that may be programmed using software (e.g., microcode) to perform the various functions discussed herein. A controller may be implemented with or without a processor, and may also 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).

The step-down circuit 11 is configured to implement the appropriate voltage and current for supplying power to the emergency lighting fixture 20. This power may be used to charge an internal battery (not shown) that forms part of the emergency lighting fixture 20. The emergency lighting fixture 20 may be powered by an AC mains system (normal mode of operation) or an integrated battery (emergency mode of operation). The buck module converts the AC voltage (i.e., above 277 VAC) input from the AC power source 40 to a usable voltage (e.g., in the range of 120 to 277 VAC) for charging the internal battery of the emergency lighting fixture 20.

In this regard, the step-down circuit 11 is an AC-to-AC converter. The step-down circuit 11 converts an input AC waveform of a specific amplitude and a specific frequency into an AC waveform having a different amplitude. Various types of AC-to-AC converters may be used to implement the buck circuit 11, such as buck cycloconverters, single-phase-to-single-phase cycloconverters, three-phase-to-three-phase cycloconverters, envelope cycloconverters, phase-controlled cycloconverters, CSI converters, transformers, VSI converters, sparse matrix converters, very sparse matrix converters, ultra-sparse matrix converters, and hybrid matrix converters. The step-down circuit 11 may also be implemented using a Switched Mode Power Supply (SMPS). SMPS circuits provide an efficient way to reduce AC from the mains supply to a desired AC voltage level. SMPS circuits use conventional components such as control ICs, switching transistors, capacitors, and inductors. SMPS circuits do not require the use of transformers.

The controller 12 is used to control and coordinate switching between the normal operating mode and the emergency operating mode. The normal operating mode is when the AC power source 40 is supplying AC power (i.e., AC mains is active). The emergency operation mode is when the AC power source 40 is not supplying AC power (i.e., AC mains failure). Controller 12 may include an algorithm/firmware that determines and switches between a normal operation mode and an emergency operation mode based on a status (e.g., activated or failed) of AC power source 40 and information from sensing module 14 related to a status (e.g., open or closed) of emergency drive relay 21.

For example, in one embodiment, the sensing module 14 monitors and detects the status of the emergency driver relay 21 (e.g., typically via white/red and white/black contact connections), which emergency driver relay 21 is used to control the 120-277VAC normal LED driver (part of the emergency lighting fixture 20) via the control relay 13. The normal operating mode is activated whenever the emergency driver relay 21 is closed. This also means that the emergency lighting fixture 20 is in a charging mode (using the power provided by the step-down circuit 11). The emergency operation mode is activated each time the emergency driver relay 21 is opened. This also means that the emergency lighting fixture 20 is in a discharge mode (i.e., the light source of the emergency lighting fixture 20 is being powered from the internal battery). In this regard, whenever there is a loss of power on the AC power source 40, the control relay 13 disconnects the AC power source 40 (i.e., AC mains) from the normal LED driver (typically via a black contact connection).

Fig. 2 shows another embodiment of the present invention. In this embodiment, the step-down module 50 includes a transformer 51 and an AC coil relay 52 having high voltage contacts. The transformer 51 may be, for example, a multi-tap low frequency transformer or a single tap low frequency transformer. As shown in fig. 2, as inputs, the transformer 51 may have one or more AC power inputs ("AC mains"). As shown in fig. 2, these AC power inputs may be 240VAC, 347VAC, and/or 480VAC. The buck module 50 is connected to the emergency lighting fixture 20. The output AC voltage level of the transformer 51 is configured to the AC voltage level (e.g., 120 VAC) required to properly charge the emergency lighting fixture 20. In this arrangement, the emergency relay 21 directly controls the AC coil relay 52. This embodiment reduces the number of components and elements required for the controller 12 and sensing module 14 of the embodiment of fig. 1.

Similar to the embodiment of fig. 1, the normal operation mode is activated whenever the emergency driver relay 21 is closed. This also means that the emergency lighting fixture 20 is in a charging mode (using power provided by the multi-tap low frequency transformer 51). The emergency operation mode is activated each time the emergency driver relay 21 is opened. This also means that the emergency lighting fixture 20 is in a discharge mode (i.e., the light source of the emergency lighting fixture 20 is being powered from the internal battery). When there is a loss of power from the AC mains, the AC coil relay 52 disconnects the AC mains from the normal LED driver.

It should be understood that the various elements/blocks shown in fig. 1 and 2 may be combined or modified to provide the above-described functions and structures. Furthermore, it may be implemented using a combination of hardware and software.

Although several inventive embodiments have been described and illustrated herein, one of ordinary skill in the art will readily envision a variety of other means and/or structures for performing the functions 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 teachings of the present invention 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 relate to each individual feature, system, article, material, kit, and/or method described herein. Furthermore, if two or more such features, systems, articles, materials, kits, and/or methods are not mutually inconsistent, any combination of two or more such features, systems, articles, materials, kits, and/or methods is included within the scope of the present disclosure.

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 defined terms.

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

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 combined, i.e., elements that in some cases are combined and in other cases are separated. The various elements listed with "and/or" should be interpreted in the same manner, i.e. "one or more" of such incorporated elements. In addition to the elements specifically identified by the "and/or" clause, other elements may optionally be present, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, a reference to "a and/or B" when used in conjunction with an open language such as "comprising" may refer in one embodiment to a only (optionally including elements other than B); in another embodiment only B (optionally including elements other than a); in yet another embodiment both a and B are referred to (optionally including other elements); etc.

As used herein in the specification and in the claims, "or" should be understood to have the same meaning as "and/or" defined above. For example, when items in a list are separated, "or" and/or "should be construed as inclusive, i.e., including at least one of the plurality of elements or lists of elements, but also including more than one of the plurality of elements or lists of elements, and optionally, additional unlisted items. Only terms explicitly indicated to the contrary, such as "only one of … …" or exactly one of … … ", or when used in a claim," consisting of … … "will refer to exactly one element of a list comprising a plurality of elements or elements. In general, the term "or" as used herein when preceded by an exclusive term such as "either," "one of … …," "only one of … …," or "exactly one of … …" should be interpreted as indicating an exclusive alternative (i.e., "one or the other, but not both"). "consisting essentially of … …" when used in the claims shall have their ordinary meaning as used in the patent statutes.

As used herein in the specification and in the claims, the phrase "at least one" referring to a list of one or more elements should be understood to mean at least one element selected from any one or more elements in the list of elements, but not necessarily including at least one of each element specifically listed within the list of elements and not excluding any combination of elements in the list of elements. This definition also allows that elements other than those specifically identified within the list of elements to which the phrase "at least one" refers may optionally be present, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, "at least one of a and B" (or equivalently, "at least one of a or B," or equivalently "at least one of a and/or B") may refer to at least one, optionally including more than one, a, and the absence of B (and optionally including elements other than B) in one embodiment; in another embodiment, at least one, optionally including more than one, B is referred to, without a being present (and optionally including elements other than a); in yet another embodiment, at least one, optionally including more than one, a and at least one, optionally including more than one, B (and optionally including other elements) are referred to; etc.

It should also be understood that, in any method claimed herein that includes 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, unless explicitly indicated to the contrary.

In the claims, and in the description above, all transitional phrases such as "comprising," "including," "carrying," "having," "containing," "involving," "containing," and the like are to be construed as open-ended, i.e., to mean including, but not limited to. Only the transitional phrases "consisting of … …" and "consisting essentially of … …" should be closed or semi-closed transitional phrases, respectively, as set forth in section 2111.03 of the patent office patent inspection program manual.

In the claims, any reference signs placed between parentheses refer to any reference signs in the drawings of the exemplary embodiments or formulas of the embodiments, thus increasing the intelligibility of the claims. These reference signs should not be construed as limiting the claims.

Claims (8)

1. A buck module (10) for an emergency power system (100), comprising:

a step-down circuit (11) to which an AC power supply (40) having an input voltage higher than 277VAC is connected, the step-down circuit being configured to convert the input voltage into an output voltage in the range of 120 to 277 VAC;

a sensing module (14) arranged to detect a status of an emergency driver relay (21) from an emergency lighting fixture (20), wherein a normal operation mode is activated when the emergency driver relay (21) is closed and an emergency operation mode is activated when the emergency driver relay (21) is open, and wherein the normal operation mode is when the AC power source (40) supplies AC power to the step-down circuit (11) and the emergency operation mode is when the AC power source (40) does not supply AC power;

-a control relay (13) configured to connect or disconnect the AC power source (40) with the emergency lighting fixture (20); and

a controller (12) configured to control the control relay in dependence on the status of an emergency driver relay detected by the sensing module, wherein in the normal operation mode the control relay connects the AC power source (40) to the emergency lighting fixture (20) and in the emergency operation mode the control relay disconnects the AC power source (40) from the emergency lighting fixture (20).

2. The buck module (10) of claim 1, wherein the emergency lighting fixture (20) is configured to be an LED-based lighting device.

3. The buck module (10) of claim 1 wherein the AC power source (40) is configured to have an input voltage of approximately 347 VAC.

4. The buck module (10) of claim 1 wherein the AC power source (40) is configured to have an input voltage of approximately 480VAC.

5. The buck module (10) of claim 1, wherein the buck circuit is a cycloconverter.

6. The buck module (10) of claim 1 wherein the buck circuit is an SMPS circuit.

7. The buck module (10) of claim 1, wherein the emergency lighting fixture (20) includes a battery, and the output voltage from the buck circuit (11) is used to charge the battery in the normal operating mode.

8. The buck module (10) of claim 7, wherein the battery is configured to power the emergency lighting fixture (20) in the emergency mode of operation.