GB2489513A

GB2489513A - Lighting device

Info

Publication number: GB2489513A
Application number: GB1105510.0A
Authority: GB
Inventors: Nicolas Paul Williams
Original assignee: Litonics Ltd
Current assignee: Litonics Ltd
Priority date: 2011-03-31
Filing date: 2011-03-31
Publication date: 2012-10-03
Anticipated expiration: 2031-03-31
Also published as: GB2489513B; WO2012131367A1; GB201105510D0

Abstract

A lighting device 1 comprises a body 3 having first and second fittings 5; one or more light sources 7 are positioned between the fittings 5; each fitting has power terminals 15 for receiving power from a primary power supply; a secondary power supply 17 is also provided via a secondary power terminal; an electronic circuit 19 controls power delivery from the power terminals 15 and secondary power supply 17 to the light sources 7; the power terminals 15-1b, 15-1a at the first fitting 5-1 are isolated from the electronic circuit 19 by an isolator 30. The secondary power supply 17 may be a backup battery which powers the light source if the primary power supply fails; the lighting device is preferably a replacement fluorescent tube type light device and the light sources may be light emitting diodes.

Description

LIGHTING DEVICE

Background

The present invention relates to lighting devices and in particular to lighting devices that have additional components and cIrcuitry to enable the lighting device to emit light using electrical energy from a secondary power supply (such as a battery) if the primary power supply (such as a mains supply) is interruptect In the event of an electrical power supply failure to a conventional lighting device, the absence of any imni ediate or sustained ambient light presents numerous safety, welfare, convenience and security concerns to the occupants of any affected public, commercial, industrial or residential buildings and areas. Existing standby or emergency lighting systems typically take the form of a bespoke unit, primarily designed for industrial and commercial environments, which solely function in the event of a power outage. These existing products typically require dedicated installation, additional wiring and regular maintenance and testing, adding further to purchase and ownership cost. Light is usually only produced in the event of a mains power failure and until either the secondary source is exhausted or primary power is restored, and during that time the user cannot typically control the light readily, such as to conserve the limited electrical storage capacity when light is not required. Further still, these lighting devices are usually functionally termed "non-maintained" and are only intended to give emergency rather than mainstream illumination when the primary mains power supply is available. Therefore, the associated emergency lighting apparatus is operationally redundant whenever mains power is available and primary lighting is used instead.

The above problems can be solved by combining standard and emergency lighting into one unit that may retro-fit any existing nonemergency light fitting or wiring installation and which may replace or augment any conventional lighting devices powered from the mains power supply.

The present inventor has previously proposed (in GB 2447495) an electric lighting device having circuitry that can detect mains failure and which can provide power to the lighting device from a backup battery provided in or close to the lighting device. The described lighting device may have any physical form including a conventional light bulb, or an elongate form to fit conventional strip-light lamp holders. One important function of this earlier lighting device is that it is able to distinguish between a failure in the mains power supply and a user controlled removal of the power supply at a light switch. As described in the inventors earlier GB application, this is achieved by evaluating the impedance across the supply terminals. When there is a mains power failure and the light is switched on, the impedance will be low; whereas when the user has switched off the light at a light switch the impedance will be high.

The present application describes a number of improvements to the lighting device that has a strip-light form that is described in the inventor's earlier GB application discussed above.

Summary of Invention

According to one aspect, the invention provides a lighting device comprising: a body having first and second fittings; one or more light sources mounted within the body between the fittings; one or more primary input power terminals on each fitting for connection to receiving terminals of a lamp holder; a secondary input power terminal for receiving secondary power from a secondary power supply, for powering a light source of the lighting device; and electronic circuitry configured to control power delivery to the one or more light sources using power received at one or more of the input power terminals; wherein the one or more primary input power terminals on the first fitting are isolated from the electronic circuitry and wherein the second fitting comprises first and second primary input power terminals that are connected to the electronic circuitry for providing power to the electronic circuitry. The body may be elongate and the fittings, end fittings.

The body of the lighting device will be light transmissive -for example translucent or transparent.

In the preferred embodiment, the electronic circuitry is configured to distinguish between: i) removal of a primary supply from the primary input terminals by a user opening a switch coupled, in use, to the lighting device; and ii) primary supply failure. Upon detection of primary supply failure, the electronic circuitry may provide power from the secondary power supply to one or more light sources of the lighting device to provide emergency lighting functionality. The electronic circuitry may also comprise sensing circuitry configured to sense an external impedance connected to the primary input power terminals. The sensed external impedance may then be used to determine if there is a primary power failure.

According to another aspect, the invention provides a lighting device comprising: a body having first and second fittings; one or more light sources mounted within the body between the fittings; one or more primary input power terminals on each filling for connection to receiving terminals of a lamp holder; a secondary input power terminal for receiving secondary power from a secondary power supply, for powering a light source of the lighting device; an isolation device mounted within the body and connectable between the one or more primary input power terminals on one fitting and the one or more primary input power terminals on the other fitting; electronic circuitry configured to control power delivery to the one or more light sources using power received at one or more of the input power terminals; and a control device for causing said isolation device to isoiate one or more of said primary input power terminals from said electronic circuitry. The control device may comprise a manually operable switch. Alternatively or in addition, the control device forms part of the electronic circuitry and is operable to determine if primary power is not present at the primary input power terminals and to determine an external impedance between the primary input power terminals and to connect the isolation device between the primary input power terminals on the first fitting and the electronic circuitry in dependence upon the determined absence of primary power and the determined external impedance. The isolation device may be or comprise a switch, relay or latch arrangement.

The electronic circuitry may determine if the primary power is absent in dependence upon a control signal received from an external device; or by determining if the primary power is absent by sensing a voltage level or frequency of a signal received via the primary input power terminals.

These and other aspects of the invention will become apparent from the following description of exemplary embodiments which are described below with reference to the accompanying Figures in which: Figure 1 is a schematic view of one embodiment of a strip lighting device for connection to a conventional strip-light lamp holder and wiring installation, and which can provide a backup light function in the event of mains power failure; Figure 2 is a schematic diagram illustrating one way in which the strip-light shown in Figure 1 is connected to a conventional strip-light connector; Figure 3 is a schematic view of the strip lighting device illustrated in Figure 1 modified to include an isolation device that can be connected between input power terminals of the lighting device; Figure 4 is a schematic diagram illustrating a preferred way in which the strip-light shown in Figure 1 is connected to a conventional strip-light connector; and Figure 5 is a schematic block diagram illustrating the main components of electronic circuitry forming part of the lighting device shown in the above Figures.

Overview Figure 1 illustrates an emergency lighting device 1 that is in the form of a traditional strip-light having an elongate optically transparent (or translucent) tube 3 that is mechanically coupled to end fillings 5-1 and 5-2. The end fittings 5 are for connecting the lighting device 1 to a conventional strip-light lamp holder (not shown), or similar light fitting or luminaire.

One or more light sources 7 are provided within the transparent tube 3. In this embodiment, two light sources 7-1 and 7-2 are provided, each including a plurality of light emitting diodes 9. In this example, the multiple light emitting diodes 9 of each light source 7 are arranged in one or more arrays 11-1 and 11-2 so that the lighting device 1 has a wide angle of illumination. To achieve optimum efficacy, efficiency and life span, the LED arrays 11 are mechanically fixed and thermally connected to a heatsink (not shown). The structure and function of the heatsink is described in the applicant's earlier GB application GB 1014428.5, the content of which is incorporated herein by reference.

As shown in Figure 1, the transparent tube 3 also includes a battery 17 for powering the light source(s) 7 in the event of mains power failure; electronic circuitry 19; a diagnostic indicator 23; and communication transducer 25. The electronic circuitry 19 includes circuitry for sensing when there is a power failure and circuitry for coupling the battery 17 to the light sources 7 to provide light during such a power failure. In most installations the lighting circuit (in which the lighting device 1 will be installed) will include one or more manually operable switches for allowing the user to switch on and off the lighting device 1. Therefore, the electronic circuitry 19 is able to sense when such switches are open and when they are closed. One way in which this sensing can be performed is described the inventor's earlier GB patent GB 2447495 and improved ways of performing the sensing are disclosed in the applicant's GB application number GB 1105485.5.

One or more of the system components inside the tube 3 may be interconnected by electrical connections 14, such as wires, bus bars, tracks or the like. A Printed Circuit Board (PCB) or simiiar may be used to provide such electrical interconnection between the system components. Mounting the system components on the PCB also provides the advantage of mechanically locating the components relative to the PCB and hence at known positions within the tube 3 once the PCB is mounted therein.

The strip-light 1 has a pair of terminals 15-la and 15-lb on end fitting 5-1 and a pair of terminals 15-2a and 15-2b on end fitting 5-2. As shown, the terminals 15 on each end fitting 5 are connected together and connected to the electronic circuitry 19 by connecting conductors 17-1 and 17-2 respectively and provide primary power to the electronic circuitry 19 for energy supply and allow for impedance sensing of the external lighting circuit.

Lighting Circuit When such a strip-light 1 is to be mounted in a conventional strip-light lamp holder to replace a luminaire of a different technology (such as a fluorescent tube or a mercury vapour gas discharge lamp), problems can occur since the strip tight holder has been designed for specific use with such lamps. One such problem is due to the external circuit components required to excite or stimulate such fluorescent tubes into an illuminating condition. In particular, these external circuit components typically include ballast circuitry (or similar current control circuitry) in close proximity to the lamp holder, usually connected between the incoming power supply and the terminals 15 of the fluorescent tube. Such external circuitry also usually includes a "starte( or similar time-delay switch that is replaceable by the user and that provides the required short voltage boost to initiate gas discharge of the lamp.

Figure 2 schematically illustrates an electrical circuit diagram detailing the way in which the lighting device 1 shown in Figure 1 is electrically connected via the lamp holder (not shown) and ballast circuitry 20 to a mains power supply 21. To simplify the drawing, Figure 2 represents all the internal components of the lighting device 1 within a single box 28. As illustrated in Figure 2, the primary (mains) supply terminal 21-a is connected to lamp holder socket terminal 23-la and primary supply terminal 21-b is connected to lamp holder socket terminal 23-2a. Lamp holder socket terminal 23-la is for receiving and for making an electrical connection with terminal 15-la of the lighting device 1 and lamp holder socket terminal 23-2a is for receiving and for making an electrical connection with terminal 1 5-2a of the lighting device 1. As shown in Figure 2, lamp holder socket terminal 23-1 b and lamp holder socket terminal 23-2b are connected to respective input terminals (27-1 and 27-2) for a conventional starter switch which has been shown as having been removed, and so the connection between terminals 27-1 and 27-2 is open circuit.

The removal of the starter is frequently required when replacing (retrofitting) fluorescent tubes with luminaries of other technologies (such as LED luminaries). Typically users may be instructed to perform the conversion by removing the starter or replacing it with an inactive insulator and perhaps also by requiring the bypassing of the ballast circuitry 20. This ensures that the electrical supply presented to the lamp holder socket terminals is the same primary power supply presented at terminals 21. Figure 2 also shows that the terminals 15-1 a and 15-1 b are electrically connected together internally of the lighting device 1 and are connected to the internal electronic circuitry 19 by connecting conductor 17-1; and similarly, that the terminals 15-2a and 15-2b are electrically connected together internally of the lighting device 1 and are connected to the internal electronic circuitry 19 by connecting conductor 17-2. This arrangement allows the terminals 15 of the lighting device 1 to be inserted into any of the terminals 23 of the lamp holder in any of the four possible connective permutations The lighting device illustrated by Figure 2 therefore can be used in existing fluorescent tube lamp holders. Additionally, it is in most deployments not necessary to bypass the ballast circuitry 20, as the circuitry 19 can still discern a difference in the external impedance of the lighting circuit between when the user operable switches are open circuit and when they are closed circuit, even if the ballast circuitry 20 is present. The way in which the electronic circuitry can self tune its internal thresholds to cater for differing installations is described in the applicant's co-pending GB application GB 1105485.5, the content of which is incorporated herein by reference.

However there exists a safely problem for any person removing or installing the lighting device 1 shown in Figure 2 in the lamp holder. In particular, when one end of the lighting device 1 is inserted into the lamp holder and the terminals 15 at that end are electrically connected to the lamp holder terminals 23, the installer may get an electric shock if they touch the exposed terminals 15 at the other end of the lighting device 1 (because there is an internal electrical path of low enough impedance between the terminals 15 at the two ends of the lighting device that could yield a potential difference with reference to ground).

This problem will not be apparent when the lamp holder is utilised for its original purpose since a fluorescent lamp with gaseous content has a high impedance between the terminals on its opposing end cap fittings. While the issue is recognised for other retrofit lamp solutions within the industry, it appears to be neglected by manufacturers who rely on the instruction or warning to the user performing the installation to adequately isolate the power supply (from terminals 21) prior to undertaking the installation.

To address this safety issue, control circuitry forming part of the circuitry 19 may be utilised to ensure that there is suitable electrical isolation between the supply terminals 15 when there is an absence of primary power supply and a high impedance is measured across the supply terminals 15 (both of which are measured by the electronic circuitry 19). This being indicative of: i) the lighting device 1 having been removed from its lamp holder; or ii) the primary power supply having been switched off at one or more external user operable switches interrupting the primary supply; or, of course, iii) thai the lighting device 1 has not been fully installed within its lamp holder. The absence of the primary power supply can be determined, for example, by sensing a voltage level or a frequency of a signal obtained at the supply terminals 15. The external impedance can be measured in numerous ways and some of these are discussed in the applicant's co.

pending GB appUcation GB 1105485.5. Figure 3 illustrates the lighting device 1 shown in Figure 1 modified to include such an isolating device, here in the form of a switch 29 that is controlled by a relay device 30 which is activated by the electronic circuitry 19. This may be a once-only activation where the switch 29 can be latched in the closed position permanently by relay device 30, or until unlatched by relay device 30 when the relay device 30 is a bi-stable latching relay or the like, or for a certain amount of time when the relay device 30 is a timer relay. As those skilled in the art will appreciate, in this embodiment the electronic circuitry 19 will be powered by the battery 17 during this pre-connection stage and if the battery 17 becomes too discharged the lighting device 1 will fail to operate as the switch 29 will never be activated without battery 17 being replaced.

This provides an additional safety feature, to prevent usage of the lighting device 1 in the event that the battery 17 has been depleted of charge, optionally requiring intervention of an external power supply or mechanical override to re-instate any device functionality.

This embodiment does not completely solve the safety problem as there is still the possibility that a user touching the terminals 15 on the unconnected end will be interpreted by the electronic circuitry 19 as the lamp being properly connected to the two ends of the lamp holder. ThIs problem can be solved by, for example, including a mechanical switch (not shown) on the lamp 3, which can be pressed by the user once the lamp 3 has been fully installed in the lamp holder. Activation of the switch may be detected by the electronic circuitry 19 which responds by activating the relay device 30 which closes the switch 29, thereby connecting the terminals 15-1 and 15-2 on both ends of the lighting device to the electronic circuitry 19. Alternatively, the user activated switch may directly control the switch 29 so that no electrical control is needed. A further alternative is if a mechanical switch is provided at each end of the lighting device 1, such that the physical insertion of the lighting device into the lamp holder activates the switch, thereby connecting the terminal at that end to the electronic circuitry 19. In this way, the terminals 15 at both ends are only connected to the electronic circuitry 19 once the switches at both ends have been activated.

This live terminal safety issue could also be overcome by employing a sensor arrangement between the lighting device and lamp holder(s) to detect the presence of the lighting device and only allow mains voltage to be applied to the holder terminals 23 when the lighting device 1 is correctly in place, Such an arrangement could be achieved using a variety of sensing methods, such as magnets and reed switches, mechanical switches, Hall Effect switches, or other physical sensors. Alternatively, an electronic system may be utilised, that requires some form of handshaking communication to be performed between the lamp holder and the lighting device 1 before the isolation device (e.g. switch 29) is removed from the circuit. In this case, of course, the isolation device may form part of the lamp holder instead of the lighting device 1.

An alternative and potentially more reliable solution to this safety issue can be achieved by employing a different arrangement of the electricaJ connection between the terminals 15, as shown in Figure 4. The lamp holder and its electrical terminals 23 remain the same as in Figure 2 and as per the original manufacture, except the open circuit starter' between terminals 27 has now been substituted with a closed circuit link 32 that electrically connects the two terminals 27-1 and 27-2 together, which in turn electrically connects the lamp holder terminals 23-2b and 23-lb together.

Inside the lighting device 1, terminals 1 5-2a and 1 5-2b are electrically connected together and isolated from other components within the lighting device 1; and the two primary input power terminals for the electronic circuitry 19 are formed by terminals 15-Ia and 15-lb which are provided on one end fitting 5-1. This arrangement thus interfaces the primary power supply at terminals 21 via all the four terminals 15 of the lighting device 1 and the corresponding mating lamp holder socket terminals 23.

However, advantageously, each pair of terminals 15 on opposite ends of the lighting device 1 is electrically isolated from the other pair of terminals 15. This arrangement ensures that during the installation or removal of the lighting device 1, there is no possibility of an exposed terminal 15 becoming live due to a low impedance connection through the lighting device 1 to the power supply terminals 21 via the terminals on the other end filling 5. This therefore solves the safety issue at little additional cost (for provision of a unit to provide closed circuit link 32) and a simple re-arrangement of internal lamp connections, terminals 15-2 now being connected together via connection 26.

A new problem is, however, created with the arrangement shown in Figure 4. In particular, if the lighting device shown in Figure 2 or 3 (or indeed any conventional or retrof it tube in which the terminals 15 at each end cap are connected together) is connected into the lamp holder circuitry shown in Figure 4, then the power terminals 21 will be connected together (short circuited). To overcome this problem, the closed circuit link 32 replacement for the starter is preferably a current limiting device such as a fuse, a temperature dependant semi-conductor device or some other suitable safety device, so that if the wrong type of lighting device is inserted into the lamp holder, the current limiting device will activate and prevent excessive current flow across the power term inals 21.

In one embodiment, the internal connections between the terminals 15 and the internal components of the lighting device 1 (such as the connections 17 to the electronic control circuitry 19) may be programmable so that the lighting device 1 can be connected to a variety of external lamp holders, including, but not limited to, those illustrated in Figures 2 and 4. Programming may be achieved via appropriate user operable switches, fusible links, software logic controlled relays etc. Electronic Circuitry Figure 5 is a block diagram illustrating the main components of the electronic circuitry 19 that can be used in the lighting devices 1. As shown, the circuitry 19 includes a power supply unit 31 that has terminals 33 that are connected to the power supply terminals 15 on the end filling(s) 5 (via the connectors 17-1 and 17-2 respectively); and secondary supply terminals 34 for connection to the positive and negative terminals of the battery 17. The power supply unit 31 is configured to transform the primary supply voltage, for example by step-down transformer, switch mode power supply or other voltage reducing and rectifying subsystem; and to provide power derived from the primary supply (or if it senses that there is no primary supply at the supply terminals 33, to supply power from the battery 17 via terminals 34) to a processor 35 that controls the operation of the lighting device 1. The power supply unit 31 also provides the power required for illuminating the light source 7.

The electronic circuitry 19 also includes sensing circuitry 37 which is configured to sense the impedance across the terminals 33; a charging circuit 39 for charging the battery 17 via the terminals 34; a diagnostic module 41 for performing the various diagnostic testing discussed above and for controlling the diagnostic indicator 23 via terminal 43; and a communications module 45 for communicating with remote devices via the communication transducer 25 connected via terminal 47.

As shown in Figure 5, in this embodiment, the electronic circuitry 19 also includes two output drivers 50-1 and 50-2 that are controlled by the processor 35 and that provide the desired drive currents for driving the light sources 7 via output terminals 49 and 51. In this embodiment, the light sources 7 are arranged in two groups, with the light sources 7 in each group being driven by a respective one of the output drivers 50. Thus, in this embodiment, the processor 35 can switch on the light sources 7 in both groups at the same time or the light sources 7 in either one of the groups by controlling the respective output driver circuits 50. The processor 35 can also vary the brightness of the light sources 7 in each group by setting a desired drive power for each output driver circuit 50.

In the block diagram illustrated in Figure 5, the different modules are shown as being separate modules from the processor 35. In practice, the functionality of many of the modules shown in Figure 5 will be software modules run by the processor 35 or a mix of software and hardware. The modules have been illustrated in the form shown in Figure 5 for ease of understanding the functions and operation of the different modules. A more detailed description of the various modules will now be given.

Processor In this embodiment, the processor 35 is at the heart of the electronic circuitry 19 and controls the operation of all of the modules shown in Figure 5. The processor 35 may be based on an ASIC device but is preferably a programmable processor (such as a PlC microcontroller) having memory and software that defines its operation. Such software controlled processors are easier to update with improved software or additional -12-functionality after installation. In the embodiment shown in Figure 3, the processor 35 is responsible for controlling the position of the switch 29 via relay device 30.

Charging Circuit The charging circuit 39 is provided to monitor the charge status of the battery 17 (via the power supply unit 31) and to charge (or recharge) the battery 17 when needed. By monitoring the charge status of the battery 17, the charging circuit 39 can ensure that the battery 17 is not overcharged or charged too rapidly. The charging circuit 29 can also signal the present battery charge status to the diagnostic module 41 for historical recording and analysis (such as to adjust brightness levels for a given minimum duration e.g. 3 hours) and/or for output to the user either via the diagnostic indicator 23 or via the communication transducer 25.

Diagnostic Module The diagnostic module 41 performs various diagnostic tests and presents the diagnostic results to the user via the diagnostic indicator 23. The diagnostic results can also be stored within a memory (not shown) of the processor 35 to maintain an historical record of the operation of the lighting device 1. The diagnostic module 41 may interact with the charging circuit 39 in order to obtain battery charge status information and with the sensing circuitry 37, the communication module 45 and the output drivers 50 to confirm correct operation thereof. The operation of the diagnostic module 41 can be controlled by the user either via signals received using the communication transducer 25 or other signals communicated, for example, over the primary supply via terminals 15.

Communications Module The communications module 45 is operable to control communication between the lighting device 1 and an external device or devices via the communication transducer 25.

The communications module 45 is responsible for performing any required modulation and demodulation of the data to be transmitted to and received from the remote device.

For example, the communications module 45 may transmit diagnostic data obtained from the diagnostic module 41 to a remote device for remote monitoring of the operation of the lighting device 1. Alternatively, user configuration data may be received from the remote device and programmed into the processor 35.

Output Driver The output drivers 50 are controlled by the processor 35 and generate the driving currents (or voltages) required to drive the light sources 7. The output driver 50 used will depend on the technology and configuration of the tight source(s) 7 being driven. In this embodiment, the light sources 7 are LEDs and the output drivers 50 can be commercially available integrated circuit LED drivers having features such as efficient Pulse Width Modulation (PWM) current feedback driving of the LEDs, whether individually or in one or more "strings". Each output driver 50 is controlled (independently or as a single entity) by the processor 35 and can generate a respective different drive current (or voltage) at its output terminals 49151. The output drivers 50 obtain their power for generating the drive signals from supply voltages generated by the power supply unit Si.

Sensing Circuitry and Power Supply Unit As shown in Figure 5, the sensing circuitry 37 is configured to sense the impedance across the primary supply terminals 33 via the power supply unit 31. The sensing circuitry 37 senses whether primary power is absent from the terminals 33 and senses the external impedance connected across the terminals 33 and then signals the processor 35 accordingly. The way in which this connection is made and the way in which the sensing circuitry 37 can perform the measurements are described in the applicant's co-pending GB application number GB 1105485.5.

Modifications and Alternative Embodiments A detailed description was given above of lighting devices embodying the present invention. As those skilled in the art will appreciate, a number of modifications and alternatives can be made to these embodiments and some of these will now be described.

In the above embodiments, the lighting device included a battery 17 for providing a backup or secondary power supply in the event of primary power supply failure. The battery can be of any technology, replaceable or non-replaceable and multiple batteries may be provided connected in series and/or in parallel. Each battery itself may comprise a single cell or multiple cells as appropriate to the battery technology. Alternatively, instead of using one or more batteries 17, other charge storage devices may be used to -14-provide a secondary power supply, such as a capacitor. However, batteries are preferred since they can provide secondary power over a longer period of time. The secondary storage device is preferably mounted internal to the lighting device, but it can be mounted externally if desired. In one embodiment, the battery can be isolated from the electronic circuitry 19 so that the lighting device can only operate in its primary mode of operation. This may be done in response to a received user input or in response to detecting a battery fault or a fault in another system component.

In the above embodiments, the light sources that were used in the lighting device 1 were LEDs. As those skilled in the art will appreciate, the use of LEDs is preferred given the ease with which they can be controlled (e.g. output intensity), their long expected operating life, rough handling ability and of particular advantage (given the battery-operation mode potential of the device) their low power consumption. However, the light sources can be formed from any lighting technology, such as compact fluorescent tubes, incandescent lighting (such as halogen lighting) etc. In the embodiment described above, the lighting device included diagnostic and communication circuitry. As those skilled in the art will appreciate, this circuitry is not essential and could be omitted if desired. Additionally, one or more user switches or inputs may be mounted on the lighting device. This user input can be used to cause the lighting device to enter a given mode of operation or to enter user configurations or to initiate a diagnostic or self-test.

In the above embodiment, the lighting device included a communications module 45 that was able to communicate with external devices using a communication transducer 25. In an alternative embodiment, the communications module 45 may be arranged to communicate with the external devices by receiving and/or transmitting signals over the mains lighting circuit in which the lighting device 1 is installed. Such communication signals would be transmitted at a different frequency to the mains signal in order that the communication signals can be separated from the mains signal. Instead of or in addition to using the communication transducer 25, the electronic circuitry 19 could communicate with one or more remote devices by varying the light produced by the light sources 7, for example switching them on and off in dependence upon the data to be transmitted. A receiver in the remote device would recover the data by detecting the variation in the light produced by the light source(s) 7. Regardless of the communication technique employed, various different standard communication protocols could be used for the communications between the lighting device and the remote device(s).

In the above embodiment, the lighting device 1 had a number of light sources of the same type (in this case LEDs) arranged into two groups that were independently driveable by the electronic circuitry 19. This is not essential -the light sources may not be independently driveable and/or the light sources may be of different types. For example, one type of light source may be provided for use when primary power is available via terminals 15 and a second type of light source may be provided for use when power is being supplied by the battery 17. Such an arrangement offers a number of improvements including reduction in power consumplion verses quality and quantity of light output, manufacturing cost, and built-in redundancy for an increased margin ol safety or component lifespan.

In the above embodiment, the lighting device had an elongate tubular body 3. The body 3 does not need to be elongate and may have any shape. The body can also be translucent as well as transparent.

In the above embodiments, each end fitting 5 included a pair of power supply terminals 15. As those skilled in the art will appreciate, in some embodiments one or more of the end fittings may only include a single power supply terminal 15 that connect with the corresponding lamp holder terminals 23 at that end of the lamp holder.

Claims

CLAIMS1. A lighting device comprising: a body having first and second fittings; one or more light sources mounted within the body between the fiftings; one or more primary input power terminals on each fitting for connection to receiving terminals of a lamp holder; a secondary input power terminal for receiving secondary power from a secondary power supply, for powering a light source of the Fighting device; and electronic circuitry configured to control power delivery to the one or more light sources using power received at one or more of the input power terminals; wherein the one or more primary input power terminals on the first fitting are electrically connected together and isolated from the electronic circuitry and wherein the second fitting comprises first and second primary input power terminals that are connected to the electronic circuitry for providing power to the electronic circuitry.
A lighting device according to claim 1, wherein the body is elongate and the fittings are end fittings.
3. A lighting device according to claim 1 or 2, wherein the electronic circuitry is configured to distinguish between: i) removal of a primary supply from the primary input terminals by a user opening a switch coupled, in use, to the lighting device; and ii) primary supply failure; and, upon detection of primary supply failure, is configured to provide power from said secondary power supply to one or more light sources of the lighting device to provide emergency lighting functionality.
4. A lighting device according to any of claims 1 to 3, wherein the electronic circuitry comprises sensing circuitry configured to sense an external impedance connected to the primary input power terminals.
5. A lighting device according to claim 4, wherein the sensed external impedance is used to determine if there is a primary power failure.
6. A lighting device comprising: a body having first and second fittings; one or more light sources mounted within the body between the fittings; one or more primary input power terminals on each fitting for connection to receiving terminals of a lamp holder; a secondary input power terminal for receiving secondary power from a secondary power supply, for powering a light source of the Lighting device; an isolation device mounted within the body and connectable between the one or more primary input power terminals on one filling and the one or more primary input power terminals on the other fitting; electronic circuitry configured to control power delivery to the one or more light sources using power received at one or more of the input power terminals; and a control device for causing said isolation device to isolate one or more of said primary input power terminals from said electronic circuitry.
7. A lighting device according to claim 6, wherein said control device comprises a manually operable switch.
8. A lighting device according to claim 6 or 7, wherein said control device forms part of the electronic circuitry and is operable to determine if primary power is not present at the primary input power terminals and to determine an external impedance between the primary input power terminals and to connect said isolation device between the primary input power terminals on the first fifing and the electronic circuitry in dependence upon the determined absence of primary power and the determined external impedance.
9. A lighting device according to claim 8, wherein the isolation device comprises a switch.
10. A lighting device according to any of claims 6 to 9, wherein the electronic circuitry is operable to determine if the primary power is absent in dependence upon a control signal received from an external device.
11. A lighting device according to any of claims 6 to 9, wherein the electronic circuitry is operable to determine if the primary power is absent by sensing a voltage level or frequency of a signal received via the primary input power terminals.
12. A lighting device according to any preceding claim, wherein the body is light transm issive.
13. A lighting device substantially as herein described with reference to or as shown in the drawings.