Patent Publication Number: US-9431855-B1

Title: Timed charge-up and illumination

Description:
RELATED PATENT APPLICATION 
     This application is a continuation application of and claims priority under 35 U.S.C. §120 to U.S. patent application Ser. No. 13/455,955, filed Apr. 25, 2012, and titled “Timed Supercapacitor Charge-Up And Emergency Illumination,” which claims priority under 35 U.S.C. §119 to U.S. Provisional Patent Application Ser. No. 61/485,749, filed May 13, 2011, and titled “Charge Timer for Supercapacitor Backup Powered Emergency Lights and Exit Signs”. The entire contents of both of the foregoing applications are hereby incorporated herein by reference for all purposes. 
    
    
     TECHNICAL FIELD 
     The present disclosure generally relates to emergency lights and exit signs and, more particularly, to controlling a charging start time for multiple emergency illumination apparatuses including emergency egress lights and exit signs, for example. 
     BACKGROUND 
     Backup power for emergency lighting fixtures such as emergency lights and exit signs has conventionally been provided by rechargeable batteries that are “trickle” charged when an alternating current (AC) line voltage is available. Generally, when the AC line voltage is lost during a power outage, for example, the batteries are used to supply power to light sources of emergency lighting fixtures. Typically, batteries are charged slowly to increase their life expectancy and avoid damage. Further, because of material limitations of general purpose rechargeable batteries, the batteries cannot be charged quickly even if desired. Thus, complete charge times for batteries in emergency lights and exit signs may be from about one to seven days. Even when several battery powered emergency lights are installed in a building, it is possible to charge the batteries in each of the emergency lights simultaneously without overloading the electrical distribution system of the building, because each of the emergency lights draws a relatively low amount of power for “trickle” charging. 
     Based on advances in materials science, supercapacitors stand to replace batteries as a power storage means in emergency lighting fixtures. Electric double-layer capacitors (EDLC) or supercapacitors (hereinafter referred to generally as supercapacitors) offer advantages and drawbacks over general purpose rechargeable batteries. For example, supercapacitors can be charged quickly without decreased lifetime expectancy or causing damage. Projected charge times for supercapacitors range from seconds to minutes for a full charge, as compared to hours or days for rechargeable batteries. For a comparable amount of power storage, the relatively quick charge time of a supercapacitor is attributed to a relatively high current draw, as compared to the “trickle” charge current draw for a rechargeable battery. 
     The relatively high current draw of supercapacitors presents a problem in many buildings such as office buildings, stores, shopping malls, theaters, and hospitals, for example, which generally include several backup powered emergency lighting fixtures. That is, if starting from a fully discharged state, the current draw required to charge several supercapacitor-powered emergency lighting fixtures may overload a building&#39;s power distribution system. Thus, to accommodate supercapacitor-powered emergency lighting fixtures, branch, feeder, and possibly even service circuits may need to be redesigned, retrofitted, or replaced to accommodate the large increase in peak current to charge the fixtures. 
     After several supercapacitor-powered emergency lighting fixtures are fully charged, their current demand returns to a normal level. However, a building&#39;s power distribution system would need sufficient capacity to handle the peak current demand required to simultaneously charge several discharged supercapacitors, even if the peak demand were expected to last only a few minutes. Thus, more robust and expensive wiring and distribution panel boards would be required to handle the supercapacitor charging energy spike (KVA peak demand), but would be unnecessary otherwise. 
     SUMMARY 
     According to one exemplary embodiments described herein, several supercapacitor-powered emergency lighting fixtures may be stagger-charged after to power failure. The stagger-charging of supercapacitors among several emergency lighting fixtures may be accomplished by each of the emergency lighting fixtures having a different preprogrammed time for charging its supercapacitor. As such, the charging of the several supercapacitors may be distributed in time, decreasing and distributing the peak energy demand. In certain embodiments, a charging priority can be set among several emergency lighting fixtures, based upon which of the emergency lighting fixtures are installed in critical or occupied locations, for example. 
     In one example embodiment, a method for timed supercapacitor charge-up and emergency illumination is described. The method can include detecting a power-on transition from power being unavailable on a power source to power being available from the power source. After detecting the power-on transition, a predetermined time can be waited according to a charge time delay value. After the predetermined time has expired, power from a power source can be coupled to a supercapacitor. The supercapacitor can then be charged with the power from the power source. 
     In another example embodiment, an apparatus for emergency illumination is described. The apparatus can include housing and at least one light source. A switch can be disposed within the housing and electrically coupled to a power source via a power distribution network. A supercapacitor can be disposed within the housing and electrically coupled to the switch and the light source. A charge time delay register can be disposed with the housing and can include a charge time delay value. A microcontroller can be disposed within the housing and can be configured to control the switch to electrically couple power from the power source to the supercapacitor based on the charge time delay value. 
     In still another embodiment, a system for emergency illumination is described. The system includes a power distribution network coupled to a power source. A plurality of emergency lighting fixtures are coupled to the power distribution network, each including a supercapacitor, a microcontroller, and a charge time delay register that stores a unique charge time delay value for the emergency lighting fixture. In certain embodiments, the microcontroller of each of the plurality of emergency lighting fixtures is configured to detect a power-on transition from power being unavailable on the power source to power being available from the power source. The microcontrollers are further configured to, after detecting the power-on transition, wait a predetermined time according to a unique charge time delay value. The predetermined time may be selected to be unique for one or several of the emergency lighting fixtures so as to distribute a combined peak power demand. After the predetermined time has expired, the microcontrollers are further configured to couple the power from the power source to the supercapacitors of the emergency lighting fixtures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of the present disclosure and the advantages thereof, reference is now made to the following description, in conjunction with the accompanying drawings briefly described as follows: 
         FIG. 1  illustrates an example embodiment of a supercapacitor-powered emergency lighting system; 
         FIG. 2  illustrates an example schematic block diagram of a timed supercapacitor charge-up and emergency illumination apparatus according to one exemplary embodiment; 
         FIG. 3  illustrates an example schematic block diagram of a timed supercapacitor charge-up and emergency illumination apparatus according to another exemplary embodiment; 
         FIG. 4  illustrates an example schematic block diagram of a timed supercapacitor charge-up and emergency illumination apparatus according to still another exemplary embodiment; 
         FIGS. 5A-5E  illustrate respective example embodiments for setting a charge time delay value according to certain exemplary aspects described herein; and 
         FIG. 6  illustrates an example embodiment of a method for timed supercapacitor charge-up and emergency illumination according to one exemplary embodiment. 
     
    
    
     The drawings illustrate only exemplary embodiments and are therefore not to be considered limiting of its scope, as other equally effective embodiments are within the scope and spirit of this disclosure. The elements and features shown in the drawings are not necessarily drawn to scale, emphasis instead being placed upon clearly illustrating the principles of the exemplary embodiments. Additionally, certain dimensions or positionings may be exaggerated to help visually convey such principles. In the drawings, reference numerals designate like or corresponding, but not necessarily identical, elements. 
     DETAILED DESCRIPTION 
     In the following paragraphs, the exemplary embodiments are described in further detail by way of example with reference to the attached drawings. In the description, well-known components, methods, and/or processing techniques are omitted or briefly described so as not to obscure the embodiments. As used herein, the “present invention” refers to any one of the embodiments of the invention described herein and any equivalents. Furthermore, reference to various feature(s) of the “present invention” is not to suggest that all embodiments must include the referenced feature(s). 
     Turning now to the drawings, in which like numerals indicate like, but not necessarily the same or identical, elements throughout, exemplary embodiments of the invention are described in detail. Turning to  FIG. 1 , an example embodiment of a supercapacitor-powered emergency lighting system  10  is described. The emergency lighting system  10  includes a power distribution network  104  and multiple supercapacitor-powered emergency lighting fixtures or apparatuses  110 ,  112 ,  114 ,  116 ,  118 , and  120 . As illustrated, the power distribution network  104  is electrically coupled to a power source, such as a power utility company, for example, via fuse  102 . It is noted that the system  10  is provided by way of example only for discussion of aspects of the exemplary embodiments described herein, and one having ordinary skill in the art would recognize that the various embodiments described herein may be practiced with alternative configurations of the system  10 . 
     In the system  10 , each of the supercapacitor-powered emergency lighting fixtures  110 ,  112 ,  114 ,  116 ,  118 , and  120  includes one or more light sources that illuminate an area or all or a portion of an exit sign, for example, and a supercapacitor that stores power in case of failure of the power source. The power distribution network  104  is electrically coupled to and supplies power to each of the supercapacitor-powered emergency lighting fixtures  110 ,  112 ,  114 ,  116 ,  118 , and  120 . In other words, the power distribution network  104  supplies power to illuminate the lights sources, when desired, and charge the supercapacitors of each of the emergency lighting fixtures  110 ,  112 ,  114 ,  116 ,  118 , and  120 , as necessary. 
     At point “A” on the power distribution network  104 , the current requirements for each of the supercapacitor-powered emergency lighting fixtures  110 ,  112 ,  114 ,  116 ,  118 , and  120  have combined, as would be readily understood by one having ordinary skill in the art. Especially if simultaneously charging each of the supercapacitors in the emergency lighting fixtures  110 ,  112 ,  114 ,  116 ,  118 , and  120 , the combined power draw at point “A” on the power distribution network  104  can be especially high and, in certain cases, may exceed the safe operating capacity or parameters of the power distribution network  104 . The fuse  102  is selected such that, if an amount of current drawn over the power distribution network  104  dangerously exceeds the safe operating parameters of the network  104 , it will “open” the connection between the power source and the network  104 , preventing damage to the network  104 . In the context described above, if simultaneously charging each of the supercapacitors in the emergency lighting fixtures  110 ,  112 ,  114 ,  116 ,  118 , and  120  after a power-on event, the power draw at point “A” on the network  104  is likely to exceed the safe operating parameters of the network  104  and, consequently, the fuse  102  is likely to disconnect the power source from the network  104 . It is noted that the disconnection of the power source from the network  104  by the fuse  102  is only one example of a result of operating the system  10  beyond its safe operating parameters. In various circumstances, operating the system  10  beyond its safe operating parameters may result in system damage or fire, for example. 
     Although resetting the fuse  102  to reconnect the power source to the network  104  may represent a relatively simple maintenance task, a regular or continuous trip (i.e., “opening”) of the fuse  102  is an indication of a dangerous condition. For example, if retrofitting a building&#39;s systems to replace battery-powered emergency lighting fixtures with supercapacitor-powered emergency lighting fixtures, the building&#39;s original power distribution system may be unable to safely handle the peak power draw required to simultaneously charge each of the supercapacitors of the new emergency lighting fixtures. Because it may be too costly (or not cost-effective) to replace and/or upgrade a building&#39;s original power distribution systems when replacing emergency lighting fixtures, what is needed is a means to distribute the peak power draw required to charge multiple supercapacitor-powered emergency lighting fixtures, such as the emergency lighting fixtures  110 ,  112 ,  114 ,  116 ,  118 , and  120 . 
     According to aspects of the embodiments described below, each of the emergency lighting fixtures  110 ,  112 ,  114 ,  116 ,  118 , and  120  distributes its power draw for charging over time, overcoming the need to replace and/or upgrade a building&#39;s original power distribution systems when retrofitting the building with the fixtures. That is, each fixture  110 ,  112 ,  114 ,  116 ,  118 , and  120  is pre-set to or manually or electronically adjustably set to draw power for charging its supercapacitor at a respective different, unique, or staggered time, so the power requirements to charge each of the fixtures do not combine to a total greater than the safe operating parameters of the network  104 . It is noted that, although each fixture  110 ,  112 ,  114 ,  116 ,  118 , and  120  is generally configured to charge its supercapacitor at a respective different charge time, in certain exemplary embodiments, the charge times at least partially overlap in time, although being generally shifted in peak power draw. Further, among exemplary embodiments described herein, it is generally acceptable if two or more emergency lighting fixtures are set to charge their supercapacitors at a substantially same time, so long as the aggregate combination of the peak power demand from all the fixtures is sufficiently distributed over time so as not to overload the network  104 . 
       FIG. 2  is a schematic block diagram of a timed supercapacitor charge-up and emergency illumination apparatus  20  according to one exemplary embodiment. Now referring to  FIG. 2 , any of the emergency lighting fixtures  110 ,  112 ,  114 ,  116 ,  118 , and  120  in  FIG. 1  may be constructed in the manner of the exemplary emergency illumination apparatus  20 . The emergency illumination apparatus  20  includes a supercapacitor  202 , a switch mode power supply (SMPS)  204 , a light source  206 , a microcontroller  208 , and a charge time delay register  210 . The apparatus  20  further includes a rectifier  220 , current limiting resistor  222 , a first power switch  222 , and a second power switch  226 . The elements of the emergency illumination apparatus  20  can be disposed within a housing of the apparatus, in various exemplary embodiments. For example, the supercapacitor  202 , switch mode power supply (SMPS)  204 , microcontroller  208 , charge time delay register  210 , rectifier  220 , current limiting resistor  222 , first power switch  222 , and second power switch  226  can be disposed within the housing. In various exemplary embodiments, the light source  206  can be disposed within or outside of the housing, depending upon the design of the emergency illumination apparatus  20 . 
     In various exemplary embodiments, the rectifier  220  includes one or more power rectifiers electrically coupled to one or both of the “AC Hot” and “AC Neutral” lines of an input AC line voltage. In certain exemplary embodiments, the rectifier  220  is configured as a halfwave, fullwave, or bridge rectifier, for example. The rectifier  220  rectifies the input AC line voltage as would be understood by one having ordinary skill in the art. The current limiting resistor  222  is electrically coupled to the rectifier  220  and includes any suitable type of resistor that reduces or limits the current (i.e., charge) flowing into the supercapacitor  202  when the first power switch  224  is closed, especially when the supercapacitor  202  is fully discharged. The current limiting resistor  222  ranges in value from about 1 to 300 Ohms, for example, in various embodiments. It is noted that the particular configuration or electrical connections among the elements of the apparatus  20  may vary among embodiments. For example, the current limiting resistor  222  may be omitted in favor of the current limiting resistor  222 A, which is electrically coupled between the supercapacitor  202  and the rectifier  220  but not between the rectifier  220  and the SMPS  204 . 
     The first power switch  224  electrically couples the output of the rectifier  220  to the supercapacitor  202  and the SMPS  204 . The second power switch  226  electrically couples the output of the SMPS  204  to the light source  206 . The control of the first and second power switches  224  and  226  by the microcontroller  208  is described in further detail below. In various exemplary embodiments, each of the first and second power switches  224  and  226  includes an electrically-actuated switch such as a transistor or relay, for example, without limitation. Similarly, the other switches  322 ,  422 , and  428 , described below with reference to  FIGS. 3 and 4 , can include, but are not limited to, an electrically actuated switch such as a transistor or relay. In general, the switches  224 ,  226 ,  322 ,  422 , and  428  be selected among any known electrically-actuated switches suitable for the application, as understood by those having ordinary skill in the art. 
     The exemplary supercapacitor  202  includes any general purpose supercapacitor such as an electric double-layer capacitor (EDLC) with relatively high energy density or a combination of several general purpose supercapacitors. In various exemplary embodiments, the supercapacitor  202  operates with a working voltage of a few volts or more and capacities of 4,000 to 6,000 farads, for example. However, the use of supercapacitors having other operating characteristics is within the scope and spirit of this disclosure. In certain exemplary embodiments, the supercapacitor  202  is selected such that it is capable of storing enough charge to illuminate the light source  206  for a sufficient amount of time if power is lost. As would be understood by those having ordinary skill in the art, however, the load presented by the light source  206  impacts the amount of time the supercapacitor  202  is capable of supplying sufficient power to illuminate the light source  206 . For example, a light source  206  that provides a higher overall lumen output would be expected to discharge the supercapacitor  202  faster than a light source  206  that provides a lower overall lumen output. 
     In certain exemplary embodiments, the SMPS  204  includes any type of switch mode power supply such as a buck or boost converter. In that context, the SMPS  204  may include bulk and filter capacitors, filter inductors, and combinations of filter networks at its inputs and outputs, as well as isolation transformers, switching transistors, and other elements understood in the art as being components of switching power supplies. In operation, the SMPS  204  converts the rectified power from the power source to power having a potential or voltage suitable for operation of the light source  206 , based on control signals from the microcontroller  208 . For example, the SMPS  204  converts the rectified power from the rectifier  220  to power having a lower voltage than the rectified AC line voltage, which is 1.414 times the root mean square (RMS) value of the AC line voltage provided by the branch circuit (i.e., 120, 208, 240 VAC). In additional aspects, the SMPS  204  also convert the power or charge stored in the supercapacitor  202 , which may be stored at a relatively low voltage, to power having a higher voltage. Examples of the light source  106  include one or more light sources such as light emitting diodes (LEDs), organic light emitting diodes (OLEDs), incandescent lamps, halogen lamps, or fluorescent lights, without limitation. Examples of LED light sources include discrete LEDs, chip on board LED, linear LED modules having multiple LEDs aligned in one or more rows, etc. When powered, the light source  106  provides light to illuminate an area such as an egress area, hallway, or room, for example, or all or a portion of an exit or other directional egress sign. 
     The microcontroller  208  can include any general purpose processor, computer, controller, Application Specific Integrated Circuit (ASIC), or Field Programmable Gate Array, for example. In certain exemplary embodiments, the microcontroller  108  is specially configured by firmware and/or the execution of software. In certain exemplary aspects, the microcontroller  108  detects a power-on transition from power being unavailable on the power source to power being available from the power source. That is, using the sense coupling  221 , the microcontroller  208  detects whether power is available from the power source based on whether a rectified voltage is present at the output of the rectifier  220 . Further, the microcontroller  208  detects when a transition occurs from power being unavailable on the power source to power being available from the power source. It is noted that the transition from power being unavailable on the power source to power being available from the power source may occur, for example, upon reconnection of power to branch circuits or upon power being restored after a power failure. Similarly, the transition from power being available on the power source to power being unavailable from the power source may occur, for example, upon disconnection of power to branch circuits or upon a power failure. 
     After detecting a power-on transition, the microcontroller  208  waits a predetermined or pre-set time according to a charge time delay value stored in the charge time delay register  210 . The charge time delay register  210  stores a charge time delay value unique for the emergency illumination apparatus  20 . After the predetermined time has expired, the microcontroller  208  controls the first power switch  224  to couple the rectified power from the rectifier  550  to the supercapacitor  202  for storage. In this context and with reference again to  FIG. 1 , it is noted that, when each of the emergency lighting fixtures  110 ,  112 ,  114 ,  116 ,  118 , and  120 , is manufactured similar to the emergency illumination apparatus  20 , the fixtures each wait a unique or respective amount of time before charging. As such, the current requirements to charge each of the fixtures do not combine to a total greater than the safe operating parameters of the network  104  in the system  10 . 
     When controlling the first power switch  224 , the microcontroller  108  also couples the rectified power from the rectifier  220  to the SMPS  204 . Using the rectified power, the microcontroller  208  controls the SMPS  204  to convert the rectified power from the rectifier  550  (or the power stored in the supercapacitor  202 ) to power having a potential suitable for operation of the light source  206 . In turn, using the second power switch  226 , the microcontroller  208  couples the power having the potential suitable for operation of the light source  206  from the SMPS  204  to the light source  206 . For operation of the microcontroller  208  even when power is not available from the power source, the microcontroller  208  can be powered by a separate battery or power source, for example. 
     As described above, the exemplary SMPS  204  is controlled by the microcontroller  208 . Particularly, by control of the SMPS  204 , the microcontroller  208  is able to control a voltage and/or current supplied to the light source  206  for illumination. Depending upon the type of light source  206  (i.e., LED, incandescent, etc.), the SMPS  204  is configured to provide sufficient power to the light source  206  to illuminate it. Further, even as the charge on the supercapacitor  202  is withdrawn to illuminate the light source  206  during a power source failure, the SMPS  204  provides a substantially constant voltage to the light source  206 . Additionally, the SMPS  204  regulates the power to the light source  206  by supplying an operating-adjusted amount of power to the light source  206  as its electrical properties may change from time to time, such as changing with temperature, for example. In other words, the SMPS  204  provides an operating-adjusted amount of power to the light source  206  so that the source does not become too hot or unstable. In certain exemplary embodiments, the SMPS  204  controls the power provided to the light source  206  according to variations in pulse width, slew rate, and/or on-off timings. 
     It is noted that the microcontroller  208  may control the various elements of the emergency illumination apparatus  20  based in-part upon the application of the emergency illumination apparatus  20 . For example, for exit sign applications, the microcontroller  208 , in certain exemplary embodiments, controls the SMPS  204  and the second power switch  226  to supply power to the light source  206  both when power is unavailable from the power source and when power is available from the power source. In other exemplary embodiments, for emergency lighting, such as egress or pathway lighting, and/or occupancy sensing applications, the microcontroller  208  controls the SMPS  204  and the second power switch  226  to supply power to the light source  206  only if a utility power failure occurs (i.e., power is unavailable from the power source) or movement is detected by a sensor or another controller electrically and/or communicably coupled to the microcontroller  208 . 
     The charge time delay register  210  stores a “Unique” delay time before the supercapacitor  202  is charged after a power-on transition occurs. As noted above, in an exemplary embodiment, each emergency illumination apparatus  20  stores a unique delay time in its charge time delay register  210 . In certain exemplary embodiments, the delay times are generally spaced so that only one emergency illumination apparatus  20  will draw a maximum current at any given time. In other words, the delay times are generally spaced to ensure that a first supercapacitor  202  (of a first emergency illumination apparatus  20 ) reaches a substantially full charge before any other supercapacitor  202  (of any other emergency illumination apparatus  20 ) starts charging. For example, the delay times of different emergency illumination apparatuses  20  are spaced in certain embodiments such that the charging of different supercapacitors  202  partially overlaps in time, although being generally shifted in peak power draw. As such, the current requirements do not combine to a total greater than the safe operating parameters of the network  104  in the system  10 . 
     The charge time delay register  210  can be programmed in a number of different ways, as further described with reference to  FIGS. 5A-5E  below. In certain exemplary embodiments, the charge time delay register  210  is a register in the microcontroller  208 , so no additional hardware is needed. 
       FIG. 3 , is a schematic block diagram of a timed supercapacitor charge-up and emergency illumination apparatus  30  according to another exemplary embodiment. Now referring to  FIG. 3 , the emergency illumination apparatus  30  includes a supercapacitor  302 , an SMPS  304 , a light source  306 , a microcontroller  308 , and a charge time delay register  310 . The apparatus  30  further includes a rectifier  320 , and a power switch  322 . It is noted that, while the circuit configuration of the emergency illumination apparatus  30  differs from that of the emergency illumination apparatus  20 , the rectifier  320 , the supercapacitor  302 , the SMPS  304 , the light source  306 , and the charge time delay register  310  are similar to the rectifier  220 , the supercapacitor  202 , the SMPS  204 , the light source  206 , and the charge time delay register  210  described above with reference to  FIG. 2 . Taking into account the differences in circuit configuration of the apparatus  30  of  FIG. 3  as compared to the apparatus  20  of  FIG. 2 , the exemplary microcontroller  308  controls the power switch  322  and the SMPS  304  accordingly. 
     The elements of the emergency illumination apparatus  30  can be disposed within a housing of the apparatus, in various exemplary embodiments. For example, the supercapacitor  302 , switch mode power supply (SMPS)  304 , microcontroller  308 , charge time delay register  310 , rectifier  320 , and power switch  322  can be disposed within the housing. In various exemplary embodiments, the light source  306  can be disposed within or outside of the housing, depending upon the design of the emergency illumination apparatus  30 . In the emergency illumination apparatus  30 , the rectified power from the power source is coupled directly to the SMPS  304  without any intermediary current limiting resistor or switch, as compared to the emergency illumination apparatus  20 . Further, the supercapacitor  302  is coupled to a node at the output of the SMPS  304  rather than at its input, as compared to the connections between the supercapacitor  202  and the SMPS  204  illustrated in  FIG. 2 . 
     In certain exemplary aspects, the microcontroller  308  detects power-on and power-off transitions from power being unavailable or available on the power source to power being available or unavailable, respectively, from the power source. That is, using the sense coupling  321 , the microcontroller  308  detects whether power is available from the power source based on whether a rectified voltage is present at the output of the rectifier  320 . Similarly, using the sense coupling  321 , the microcontroller  308  detects whether power is unavailable from the power source based on whether no rectified voltage is present at the output of the rectifier  320 . Further, the microcontroller  308  detects when a transition occurs from power being unavailable or available on the power source to power being available or unavailable, respectively, from the power source. It is noted that the transition from power being unavailable on the power source to power being available from the power source may occur, for example, upon reconnection of power to branch circuits or upon power being restored after a power failure. Similarly, the transition from power being available on the power source to power being unavailable from the power source may occur, for example, upon disconnection of power to branch circuits or upon a power failure. 
     In general, when power is available from the power source, the microcontroller  308  controls the SMPS  304  to supply power to charge or maintain the charge stored in the supercapacitor  302 . Further, based on the control of the switch  322 , the microcontroller  308  also controls the SMPS  304  to supply power to the light source  306 . Because the microcontroller  308  is able to control the amount of power supplied at the output of the SMPS  302 , based on pulse width modulation control of the SMPS  302 , for example, the microcontroller  308  can control the amount and rate of power being supplied to the supercapacitor  302 . 
     In certain exemplary embodiments, after detecting a power-on transition, the microcontroller  308  waits a predetermined or pre-set amount of time according to a charge time delay value stored in the charge time delay register  310 . In certain exemplary embodiments, the charge time delay register  310  stores a charge time delay value unique for the emergency illumination apparatus  30 . After the predetermined or pre-set time has expired, the microcontroller  308  is configured to control the SMPS  304  to convert the rectified power from the rectifier  320  into power to charge the supercapacitor  302 . In this context and with reference again to  FIG. 1 , it is noted that, when each of the emergency lighting fixtures  110 ,  112 ,  114 ,  116 ,  118 , and  120 , is the same or substantially similar to the emergency illumination apparatus  30 , the fixtures each wait a unique or respective amount of time before charging. As such, the current requirements to charge each of the fixtures do not combine to a total greater than the safe operating parameters of the network  104  in the system  10 . 
     Further, using the rectified power from the rectifier  320 , the microcontroller  308  controls the SMPS  204  to convert the rectified power to power having a potential suitable for operation of the light source  306 . In turn, using the power switch  322 , the microcontroller  308  is also configured to couple the power having the potential suitable for operation of the light source  306  from the SMPS  304  to the light source  306 . For operation of the microcontroller  308  even when power is not available from the power source, the microcontroller  308  is capable of being powered by a separate battery or power source, for example. 
     It is noted that the microcontroller  308  may control the various elements of the emergency illumination apparatus  30  based in part upon the application of the emergency illumination apparatus  30 . For example, for exit sign applications, the microcontroller  308 , in certain exemplary embodiments, controls the SMPS  304  and the power switch  322  to supply power to the light source  306  both when power is unavailable from the power source and when power is available from the power source. Particularly, even when power is unavailable from the power source and cannot be provided by the SMPS  304 , the microcontroller  308  can control the switch  322  to maintain a closed position, electrically coupling stored power from the supercapacitor  302  to the light source  306 . In other exemplary embodiments, for emergency lighting, such as egress lighting, pathway lighting, or occupancy sensing applications, the microcontroller  308  controls the SMPS  304  and the power switch  322  to supply power to the light source  306  only if a utility power failure occurs (i.e., power is unavailable from the power source) or movement is detected by a sensor or another controller electrically and/or communicably coupled to the microcontroller  308 . 
     Similar to the charge time delay register  210  of  FIG. 2 , the charge time delay register  310  of  FIG. 3  stores a “unique” delay time before the supercapacitor  302  is charged after a power-on transition occurs. As noted above, in an exemplary embodiment, each emergency illumination apparatus  30  stores a unique delay time in its charge time delay register  310 . The delay times are generally spaced so that only one emergency illumination apparatus  30  will draw a maximum current at any given time. In other words, the delay times are generally spaced to ensure that a first supercapacitor  302  (of a first emergency illumination apparatus  30 ) reaches a substantially full charge before any other supercapacitor  302  (of any other emergency illumination apparatus  30 ) starts charging. For example, the delay times of different emergency illumination apparatuses  30  are spaced in certain embodiments such that the charging of different supercapacitors  302  partially overlaps in time, although being generally shifted in peak power draw. As such, the current requirements do not combine to a total greater than the safe operating parameters of the network  104  in the system  10 . 
       FIG. 4  is a schematic block diagram of a timed supercapacitor charge-up and emergency illumination apparatus  40  according to still another exemplary embodiment.  FIG. 4 , the emergency illumination apparatus  40  includes a supercapacitor  402 , a light source  406 , a microcontroller  408 , a programmable time delay  430 , and an occupancy sensor  432 . In various exemplary embodiments, the occupancy sensor  432  operates as a motion or similar sensor to determine whether a space such as a hallway, stairwell, or room, or any portion thereof is occupied. The apparatus  40  further includes a transformer  420 , a first power switch  422 , a rectifier  424 , a current limiting resistor  426 , and a second power switch  428 . It is noted that, while the circuit configuration of the emergency illumination apparatus  40  differs from the emergency illumination apparatuses  20  and  30 , certain elements of the emergency illumination apparatus  40  are similar to the corresponding elements in the emergency illumination apparatuses  20  and  30  described above with reference to  FIGS. 2 and 3 . Taking into account the differences in circuit configuration of the apparatus  40  of  FIG. 4  as compared to the apparatuses  20  and  30  of  FIGS. 2 and 3 , the exemplary microcontroller  408  controls the second power switch  428  and the programmable time delay  430  accordingly. 
     The elements of the emergency illumination apparatus  40  can be disposed within a housing of the apparatus, in various exemplary embodiments. For example, the transformer  420 , supercapacitor  402 , microcontroller  408 , programmable time delay register  430 , rectifier  424 , current limiting resistor  426 , and power switch  428  can be disposed within the housing. In various exemplary embodiments, the light source  406  can be disposed within or outside of the housing, depending upon the design of the emergency illumination apparatus. The exemplary transformer  420  electrically isolates the remaining elements of the apparatus  40  from the power source while stepping down the AC line voltage provided by the power source to a stepped-down AC voltage. In certain embodiments, the transformer  420  is selected to provide a stepped-down AC voltage that is a certain ratio of the AC line voltage, such as one-tenth the AC line voltage, for example, without limitation. In the emergency illumination apparatus  40 , the secondary side of the transformer  420  is electrically coupled to the first power switch  422 , which is controlled by the programmable time delay  430 , and the first power switch  422  is electrically coupled to the rectifier  424 . 
     When the first power switch  422  is closed and power is available from the power source, rectified power output by the rectifier  424  is electrically coupled to the supercapacitor  402  via the current limiting resistor  426 . The supercapacitor  402  is electrically coupled to the light source  406  via the second power switch  428 . In certain exemplary aspects, the microcontroller  408  and the programmable delay  430  detect power-on and power-off transitions from power being unavailable or available on the power source to power being available or unavailable, respectively, from the power source. That is, using the sense coupling  421 , the microcontroller  408  and the programmable delay  430  detect whether power is available from the power source based on whether a voltage is present at the secondary side of the transformer  420 . Similarly, using the sense coupling  421 , the microcontroller  408  and the programmable delay  430  detect whether power is unavailable from the power source based on whether no voltage is present at the secondary side of the transformer  420 . Further, the microcontroller  408  and the programmable delay  430  detect when a transition occurs from power being unavailable or available on the power source to power being available or unavailable, respectively, from the power source. It is noted that the transition from power being unavailable on the power source to power being available from the power source may occur, for example, upon reconnection of power to branch circuits or upon power being restored after a power failure. Similarly, the transition from power being available on the power source to power being unavailable from the power source may occur, for example, upon disconnection of power to branch circuits or upon a power failure. 
     In certain exemplary embodiments, after detecting a power-on transition, the programmable time delay  430  waits a predetermined or pre-set time according to a predetermined or pre-set charge time delay value before closing the first power switch  422  and coupling power to the rectifier  424  and the supercapacitor  402 . After detecting a power-off transition, the programmable time delay  430  opens the first power switch  422 . In this manner, the supercapacitor  402  is not electrically coupled to the power source immediately upon a subsequent power-on transition. The programmable time delay  430  provides control to electrically couple and decouple the supercapacitor  402  from the power supply via the switch  422  in a manner similar to the control provided by the microcontrollers  208  and  308  of  FIGS. 2 and 3 . In the emergency illumination apparatus  40  of  FIG. 4 , however, the programmable time delay  430  is provided as an example of a circuit configuration where a circuit component or element other than a microcontroller controls the electrical coupling of power to a supercapacitor. In certain exemplary embodiments, the microcontroller  408  sets the predetermined charge time delay value of the programmable time delay  430 . Alternatively, the predetermined charge time delay value of the programmable time delay  430  is set exclusively from the microcontroller  408 . 
     In certain exemplary embodiments, the programmable time delay  430  waits a predetermined time after a power-on transition is detected. After the predetermined time has expired, the programmable time delay  430  closes the first power switch  422  to couple power to charge the supercapacitor  402 . In this context and with reference again to  FIG. 1 , it is noted that, when each of the emergency lighting fixtures  110 ,  112 ,  114 ,  116 ,  118 , and  120 , is substantially similar to the emergency illumination apparatus  40 , the fixtures each wait a unique or respective amount of time before charging. In other words, the delay times are generally spaced to ensure that a first supercapacitor  402  (of a first emergency illumination apparatus  40 ) reaches a substantially full charge before any other supercapacitor  402  (of any other emergency illumination apparatus  40 ) starts charging. For example, the delay times of different emergency illumination apparatuses  40  are spaced in certain embodiments such that the charging of different supercapacitors  402  partially overlaps in time, although being generally shifted in peak power draw. As such, the current requirements do not combine to a total greater than the safe operating parameters of the network  104  in the system  10 . 
     In certain exemplary embodiments, the microcontroller  408  electrically couples the rectified power from the rectifier  424  and/or the power stored in the supercapacitor  402  to the light source  406  via control of the second power switch  428 . It is noted that the microcontroller  408  may control certain elements of the emergency illumination apparatus  40  based in part upon the application of the emergency illumination apparatus  40 . For example, for exit sign applications, the microcontroller  408  controls the second power switch  428  to supply power to the light source  406  both when power is unavailable from the power source and when power is available from the power source. In other exemplary embodiments, for emergency lighting and/or occupancy sensing applications, the microcontroller  408  controls the second power switch  428  to supply power to the light source  206  only if a utility power failure occurs (i.e., power is unavailable from the power source) or movement is detected by a sensor. Additionally, in certain exemplary embodiments, the microcontroller  408  controls the second power switch  428  based on motion detected by the occupancy sensor  432  regardless of whether power is available or unavailable from the power source. 
     The programmable time delay  430  operates the first power switch  422  with a “unique” delay time before electrically coupling the supercapacitor  302  to power from the power source after a power-on transition occurs. In an exemplary embodiment, each emergency illumination apparatus  40  operates with a unique delay time according to its programmable time delay  430 . The delay times are generally spaced so that only one emergency illumination apparatus  40  will draw a maximum current at any given time. In other words, the delay times are generally spaced to ensure that a first supercapacitor  402  (of a first emergency illumination apparatus  40 ) reaches a substantially full charge before any other supercapacitor  402  (of any other emergency illumination apparatus  40 ) starts charging. In certain other exemplary embodiments, the delay times of different emergency illumination apparatuses  40  are spaced to at least partially overlap the charge of the supercapacitors  402  of the different emergency illumination apparatuses  40  in time, although being generally shifted in peak power draw. As such, the current requirements do not combine to a total greater than the safe operating parameters of the network  104  in the system  10 . In certain exemplary embodiments, the programmable time delay  430  can be programmed in a number of different ways, as further described with reference to  FIGS. 5A-5E  below. 
       FIGS. 5A-5E , are examples for setting a charge time delay value according to certain exemplary embodiments. It is noted that the embodiments provided in  FIGS. 5A-5E  present alternative means to set and/or store a charge time delay value. However, the embodiments in  FIGS. 5A-5E  are provided by way of example only and other equivalent means are within the scope and spirit of this disclosure. 
     Referring now generally to  FIGS. 5A-E  and particularly to  FIG. 5A , a switch  506 A is electrically and/or communicatively coupled with the microcontroller  502 A to program a desired charge time delay value to the charge time delay register  504 A. For example, the switch  506 A may include a bank of Dual Inline Position (DIP) switches or a potentiometer. Based on the settings of the switch  506 A, which may be determined and manually adjusted by a person during installation, the microcontroller  502 A sets a value of the charge time delay value stored in the charge time delay register  504 A. In certain exemplary embodiments, the microcontroller  502 A executes an algorithm to set the charge time delay value randomly based on the settings of the switch  506 A. In other exemplary embodiments, the microcontroller  502 A refers to a lookup table to set the charge time delay value based on the settings of the switch  506 A. In still other exemplary embodiments, the microcontroller  502 A calculates the value of the charge time delay value by using the settings of the switch  506 A as a parameter of the calculation, or directly sets the value of the charge time delay value based on the settings of the switch  506 A. 
     In  FIG. 5B , a pseudorandom number generator  506 B is electrically and/or communicatively coupled with the microcontroller  502 B to program a desired charge time delay value to the charge time delay register  504 B. Use of the pseudorandom number generator  506 B in each of a plurality of supercapacitor-powered emergency lighting fixtures would provide automatic programming of substantially different charge time delay values in each of the fixtures. Again, the microcontroller  502 B can use any pseudorandom number generated by the pseudorandom number generator  506 B as a seed in an algorithm, as a pointer to a lookup table, or as an input parameter in a calculation for determining a value of the charge time delay value. 
     In  FIG. 5C , an occupancy sensor  506 C is electrically and/or communicably coupled to the microcontroller  502 C and provides a control signal based on detected motion, for example, which is illustrative of occupancy. Based on the control signal provided by the occupancy sensor  506 C, the microcontroller  502 C sets or modifies the value of the charge time delay value in the charge time delay register  504 C. In one exemplary embodiment, if the charge time delay value was predetermined to a first value and the occupancy sensor  506 C provides an indication that a room or egress area is occupied, the microcontroller  502 C reduces the charge time delay value to a value less than the first value. In another exemplary embodiment, if the occupancy sensor  506 C provides an indication that a room or egress area is occupied, the microcontroller  502 C “zeroes out” the charge time delay value, resulting in immediate supercapacitor charging. 
     In  FIG. 5D , the microcontroller  502 D is electrically and/or communicably coupled to a programming port  506 D for programming the charge time delay value stored in the charge time delay register  504 D. For example, a person with an external programmer such as a special application programmer, smart phone, portable personal computer, or tablet computer, for example, may interface with the programming port  506 D to set the charge time delay value. In various exemplary embodiments, the programming port  506 D may be an R-232/422 serial port, a Universal Serial Bus (USB) port, or an Infra-Red (IR) port, for example, without limitation. 
     The microcontroller  502 E is electrically and/or communicably coupled to a wireless transceiver  506 E for programming the charge time delay value stored in the charge time delay register  504 E. Using the wireless transceiver  506 E, the microcontroller  502 E receives commands to update the value of the charge time delay value, and the commands can be coordinated among a plurality of emergency lighting fixtures in certain exemplary embodiments. For example, using the wireless transceiver  506 E, the microcontroller  502 E communicates with a control center that sends commands to multiple emergency lighting fixtures. Using special algorithms, the control center coordinates the multiple emergency lighting fixtures wirelessly so as to not overload power distribution, networks or to prioritize certain emergency lighting fixtures. The wireless transceiver  506 E may operate using one or a combination of wireless networks such as WiFi, Zigbee, or Bluetooth, for example, without limitation. 
     Further, intercommunications between emergency illumination apparatuses supported by the wireless transceiver  506 E can provide a means for cooperative sequential charging, with or without central control. Also, with building wide communications, charging of individual supercapacitors can be delayed until other loads have started and the metered electric service peak demand has returned to relatively normal levels. Thus, specific peak demand, current, and/or charge times could be specified for supercapacitor-powered emergency light fixtures wirelessly and individually. 
     Before turning to the process flow diagrams of  FIG. 6 , it is noted that the embodiments described here may be practiced using an alternative order of the steps illustrated in  FIG. 6 . That is, the process flows illustrated in  FIG. 6  are provided as an example only and may be practiced using process flows that differ from those illustrated. Additionally, it is noted that not all steps may be required. In other words, one or more of the steps may be omitted or replaced, without departing from the spirit and scope of this disclosure. In alternative embodiments, steps may be performed in different orders, in parallel with one another, or omitted entirely, and/or certain additional steps may be performed without departing from the scope and spirit of this disclosure. 
       FIG. 6  is an example embodiment of a method  600  for timed supercapacitor charge-up and emergency illumination. Now referring to  FIGS. 1-4 and 6 , at the outset, it is noted that, although the method  600  is described with reference to certain ones of the example emergency illumination apparatuses  20 ,  30 , and  40  of  FIGS. 2-4 , the method  600  can be performed by other equivalent emergency illumination apparatuses as would be understood by those having ordinary skill in the art. 
     Beginning at step  610 , a determination is made as to whether a power-on or power-off transition has occurred. In certain exemplary embodiments, the microcontroller  208  detects whether a power-on or power-off transition has occurred on the power source using the sense coupling  221 . If a power-on transition is detected, the detect power-on branch is followed to step  620 , where the emergency lighting fixture waits a (unique) predetermined time according to the charge time delay value stored in the charge time delay register  210 . For example, with reference to  FIG. 2 , the emergency illumination apparatus  20  waits a predetermined time after detecting a power-on transition according to a charge time delay value stored in the charged time delay register  210 , as described above. 
     After the predetermined time has expired, the process continues to step  630 , where the emergency illumination apparatus electrically couples power from a power source to a supercapacitor. In certain exemplary embodiments, with reference to the emergency illumination apparatus  20  of  FIG. 2 , after the predetermined time has expired, the microcontroller  208  controls the switch  224  to electrically couple the power from the power source (as rectified by the rectifier  220  and limited by the current limiting resistor  222 ) to the super capacitor  202 . As another example, with reference to the emergency illumination apparatus  30  of  FIG. 3 , after the predetermined time has expired, the micro controller  308  controls the SMPS  304  to convert power from the power source and to provide the converted power to charge the super capacitor  302 . 
     In step  640 , the supercapacitor is charged by the electrically coupled power. As described above, because the amount of time waited at step  620  is unique for the emergency illumination apparatus from several other emergency illumination apparatuses, the power distribution network that supplies power to the apparatuses is not overloaded from its safe operating parameters. In certain embodiments, power is converted into power having a potential suitable for operating a light source in step  650 . Additionally, at step  660 , the power having the potential suitable for operation of the light source is electrically coupled to the light source at step  660 . Referring to the emergency illumination apparatus  20  of  FIG. 2 , for example, at step  650 , the microcontroller  208  controls the SMPS  204  to convert the power from the power source (and/or the super capacitor  202 ) to power having a potential suitable for operation of the light source  206 . Further, at step  660 , the microcontroller  208  electrically couples the power having the potential suitable for operation of the light source  206 , as output from the SMPS  204 , to the light source  206  by closing the second power switch  226 . Alternatively, in another exemplary embodiment and with reference to the emergency illumination apparatus  30  of  FIG. 3 , at step  650 , the microcontroller  308  controls the SMPS  304  to convert the power from the power source to power having a potential suitable for operation of the light source  306 . Additionally, at step  660 , the microcontroller  308  electrically couples the power having the potential suitable for operation of the light source  306 , as output by the SMPS  304 , to the light source  306  closing the power switch  322 . 
     It is noted that, among certain exemplary embodiments, steps  650  and  660  are optional and may be omitted. Particularly, depending upon the use or application of the emergency illumination apparatus, the steps of converting power at step  650  and electrically coupling the power to a light source at step  660  are omitted if, after detecting a power-on transition, the emergency lighting apparatus does not illuminate any light source. For example, for certain applications such as emergency egress lighting, when power is provided by the power source, the emergency illumination apparatus does not illuminate the light source. 
     The process returns to step  610  to determine another power-on or power-off transition occurs. If a determination is made that a power-off transition has occurred, the detect power-off branch is followed to step  670 , where the emergency illumination apparatus electrically decouples the supercapacitor from the power source. Referring to the emergency illumination apparatus  20  of  FIG. 2  as an example, upon detection of a power-off transition at step  670 , the micro controller  208  electrically decouples the supercapacitor  202  from the power source by opening the first power switch  224 . As a different example, with reference to the emergency illumination apparatus  40  of  FIG. 4 , the programmable time delay  430  electrically decouples the supercapacitor  402  from the power source by opening the first power switch  422 . As noted above, the decoupling of the supercapacitor from the power source insures that the supercapacitor is (at least initially) disconnected from the power source when the next power-on transition occurs and the power source is reconnected to power. 
     In step  680 , power is converted from the supercapacitor to provide power for a light source. For example, with reference to the emergency illumination apparatus  20  of  FIG. 2 , the microcontroller  208  controls the SMPS  208  to convert power from the supercapacitor  202  to power having a potential suitable for operation of the light source  206 . In other exemplary embodiments of emergency illumination apparatuses, the step of power conversion at  680  may be omitted. For example, with reference to the emergency illumination apparatus  40  of  FIG. 4 , power from the supercapacitor  402  is electrically coupled directly to the light source  406  without any conversion being necessary at step  680 . It is noted that, in some embodiments, the light source  406  may include a separate LED driver, as discussed above, and the power stored in the supercapacitor  402  may be suitable for direct input to the LED driver. 
     Power is coupled to a light source to illuminate the light source at step  690 . With reference to the emergency illumination apparatus  20  of  FIG. 2 , for example, the microcontroller  208  electrically couples the power output by the SMPS  204  to the light source  206  by closing the second power switch  226 . As another example, with reference to the emergency illumination apparatus  30  of  FIG. 3 , the microcontroller  308  electrically couples the power stored in the supercapacitor  302  to the light source  306  by closing the power switch  322 . As still another example, with reference to the emergency illumination apparatus  40  of  FIG. 4 , the microcontroller electrically couple the power stored in the supercapacitor  402  to the light source  406  by closing the second power switch  428  at step  690 . After step  690 , the process again proceeds back to step  610  to determine whether a power-on or power-off transition occurs. 
     In the exemplary method  600 , the step of setting the charged time delay value  692  may occur at any time during the process flow. Particularly, changing or setting the charge time delay value at step  692  may be performed by any of the means illustrated and described with reference to  FIG. 5A-5E . In other words, the charge time delay value stored in any one of the charge time delay register  210 , the charge time delay register  310 , or the programmable time delay  430 , for example, may be set at step  692 . In turn, the predetermined amount of time waited at step  620  is affected. 
     Although embodiments of the present invention have been described herein in detail, the descriptions are by way of example. The features of the invention described herein are representative and, in alternative embodiments, certain features and elements may be added or omitted. Additionally, modifications to aspects of the embodiments described herein may be made by those skilled in the art without departing from the spirit and scope of the present invention defined in the following claims, the scope of which are to be accorded the broadest interpretation so as to encompass modifications and equivalent structures.