Patent Publication Number: US-2012038213-A1

Title: Non-charging battery backup unit (bbu)

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims the benefit of U.S. Provisional Patent Application No. 61/372,131 filed Aug. 10, 2010, the entire contents of which are hereby incorporated by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention is directed to a battery backup unit (BBU) having a DC input, a DC output, a compartment for removably receiving a plurality of batteries and a controller for connecting the batteries to the DC output when no current is detected at the DC input and, more specifically, toward a BBU having a DC input, a DC output, a compartment for removably receiving a plurality of batteries and a controller for connecting the batteries to the DC output when no current is detected at the DC input, wherein the BBU is incapable of charging the batteries in the battery compartment. 
     BACKGROUND OF THE INVENTION 
     In conventional telephone systems, power and data are provided over wires that connect a customer&#39;s home to a telephone central office. In newer telephone systems, data may be provided over an optical fiber that terminates at an optical network unit (ONU) or network interface unit (NIU) located at a customer&#39;s home or business. These systems are referred to as fiber-to-the-home (FTTH) systems. Power cannot be transmitted over the optical fiber, and therefore, power for operating the ONU and its internal laser and optical/electric converters is generally provided from the customer premises via a DC converter connected to an AC power source (e.g., a wall outlet) at the customer premises. In the event of a power outage at the customer premises, telephone service in a FTTH system will be lost unless backup power is provided. However, most customer locations do not have a source of backup power. 
     To address this problem, it is known to provide a battery backup unit (BBU) at the subscriber location that provides power to the ONU in the event of a power failure. Traditional backup systems contain an AC/DC converter to power the ONU while power is available, and they also provide power to a charging system that keeps a battery system charged for use when power is interrupted. When main power is lost, the BBU switches to the battery system which then powers the ONU. When the backup battery is depleted, service is lost until the main power returns. 
     To make the BBU easy to use for a customer, the battery is usually packaged in a custom plastic enclosure with an integrated electrical connector. The battery pack is then easily handled and put into or removed from the BBU. In addition, the battery pack recharges while connected to AC power so that a customer does not need to maintain or monitor the charge on the battery. 
     There are several drawbacks to this approach to providing backup power. The first is the complexity of charging and maintaining a charge on a battery. The correct voltages, currents, charge durations, and charge frequencies are highly dependent on the battery technology used (lithium ion, nickel cadmium, etc.), and even within a given technology, these characteristics are dependent on the composition of the battery. As a result, a charger must either be custom tuned in the factory for a particular battery type and composition, or it must be field adaptable to accommodate different batteries. In addition, in either scenario, if new battery technology is developed, even if it has the same voltage and current characteristics, its charging requirements may not be accommodated by the charger. It therefore may be necessary to redesign or field-upgrade the BBU when new battery technology is developed. 
     Custom battery packs are beneficial for ease of customer use, but customization also means that these battery packs may not be readily available at retail outlets. As a result, in the event of an outage that exceeds the battery backup duration, or when the battery system fails during an outage, a customer will not be able to maintain service because there is no way to readily procure another battery. A customer might own a second battery pack, but even that will not help if the charge on that second battery pack is not maintained. 
     Conventional BBU&#39;s also have an integral power supply which takes in an AC voltage and converts it to DC. While needed for the backup system to operate, this function is redundant in many FTTH systems since ONU&#39;s generally have their own power supplies. When battery backup is added to the ONU, the existing power supply is removed and the BBU is inserted. While the removed power supply could be used as a spare for an ONU without a BBU, in general it will be an unnecessary cost addition for the BBU. 
     In addition, the service provider is generally responsible for the safety of the BBU. Some of the custom batteries used in BBU&#39;s are susceptible to fire and/or explosion under certain conditions, and BBU&#39;s with rechargeable batteries make safety assurance more complex. The service provider may also need to store a large number of battery packs for use in new installations and may be required to provide safe disposal facilities for exhausted battery packs. Often this means additional costs for safety elements/features in the system and testing for safety approval from bodies such as Underwriter Laboratories (UL). It would therefore be desirable to provide a BBU for an ONU that does not suffer from the aforementioned shortcomings. 
     SUMMARY OF THE INVENTION 
     These problems and others are addressed by embodiments of the present invention, a first aspect of which comprises a battery backup unit (BBU) that includes a housing and at least one battery compartment in the housing that has an output terminal. The BBU further includes at least one DC input, a DC output, a path from the at least one DC input to the DC output, and circuitry connecting the output terminal to the path which circuitry includes a switch for selectively connecting the output terminal to the path. The circuitry precludes current flow from the at least one DC input to the output terminal, and a controller is provided to detect a condition of the path and to selectively control the switch when the condition is detected. 
     Another aspect of the invention comprises a BBU that has a housing and at least one battery compartment in the housing which has an output terminal. The BBU also includes a DC input, a DC output, a path from the DC input to the DC output and circuitry for selectively connecting the output terminal to the path, which circuitry includes a switch. A controller is configured to detect a condition of the path and to selectively control the switch to connect the output terminal to the path when the condition is detected, and the BBU is incapable of charging batteries in the at least one battery compartment. 
     A further aspect of the invention comprises a BBU having a housing and at least one battery compartment in the housing that includes a battery terminal. The BBU also includes a DC input, a DC output, a DC path from the DC input to the DC output and a control mechanism for controlling current flow at the battery terminal and a circuitry arrangement for selectively connecting the battery terminal to the path. The control mechanism includes a controller for detecting a condition of the path and controlling the circuitry arrangement to selectively connect the battery terminal to the path when the condition is detected. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other aspects and features of embodiments of the invention will be better understood after a reading of the following detailed description together with the attached drawings wherein: 
         FIG. 1  is a schematic illustration of a battery backup unit according to the present invention connected to a network interface unit. 
         FIG. 2  is perspective view of the battery backup unit of  FIG. 1 . 
         FIG. 3  is a circuit diagram showing exemplary circuitry for use in a battery backup unit according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention now is described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. 
     Like numbers refer to like elements throughout. In the figures, the thickness of certain lines, layers, components, elements or features may be exaggerated for clarity. Broken lines illustrate optional features or operations unless specified otherwise. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the specification and relevant art and should not be interpreted in an idealized or overly formal sense unless expressly so defined herein. Well-known functions or constructions may not be described in detail for brevity and/or clarity. 
     As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. As used herein, phrases such as “between X and Y” and “between about X and Y” should be interpreted to include X and Y. As used herein, phrases such as “between about X and Y” mean “between about X and about Y.” As used herein, phrases such as “from about X to Y” mean “from about X to about Y.” 
     It will be understood that when an element is referred to as being “on”, “attached” to, “connected” to, “coupled” with, “contacting”, etc., another element, it can be directly on, attached to, connected to, coupled with or contacting the other element or intervening elements may also be present. In contrast, when an element is referred to as being, for example, “directly on”, “directly attached” to, “directly connected” to, “directly coupled” with or “directly contacting” another element, there are no intervening elements present. It will also be appreciated by those of skill in the art that references to a structure or feature that is disposed “adjacent” another feature may have portions that overlap or underlie the adjacent feature. 
     Spatially relative terms, such as “under”, “below”, “lower”, “over”, “upper”, “lateral”, “left”, “right” and the like, may be used herein for ease of description to describe one element or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is inverted, elements described as “under” or “beneath” other elements or features would then be oriented “over” the other elements or features. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the descriptors of relative spatial relationships used herein interpreted accordingly. 
       FIGS. 1 and 2  illustrate a battery backup unit (BBU)  10  according to an embodiment of the present invention that includes a first DC input  12  and a second DC input  13 , either one of which is connectable to a power supply  14 , and a first DC output  16  and a second DC output  17 , either one of which is connectable to a network interface unit (NIU)  18  mounted on the wall  20  of a building. The first DC input  12  and first DC output  16  may comprise, for example F connectors while the second DC input  13  and the second DC output  17  may comprise barrel connectors. The first and second DC inputs  12 ,  13  connect to the same input node and the first and second DC outputs  13 ,  17  connect to the same output node and allow for different types of connectors to be used with the BBU  10 . As shown in  FIG. 2 , the BBU  10  also comprises a housing  24  having a hinged lid  26  for selectively covering and allowing access to a first battery compartment  28  and a second battery compartment  30 . Each of the first and second battery compartments  28 ,  30  includes a plurality of locations  32  for receiving a battery  33 , in this case a standard AA battery, connected to circuitry, illustrated in  FIG. 3 , and enclosed within housing  24 . A plurality of visual indicators  34   a ,  34   b  and  34   c , which may comprise, for example, LED&#39;s, and a data port  36  are provided on the housing  24  and connected to the circuitry inside housing  24  as described hereafter. 
       FIG. 3  illustrates circuitry contained within housing  24  which may comprise, for example elements on a circuit board interconnected by traces or otherwise electrically coupled. The circuitry include a first path  38  that electrically connects input  12  to output  16  and allows for a substantially unregulated DC power flow from power supply  14  to NIU  18  via BBU  10  under normal operating conditions when DC power is provided to input  12  by power supply  14 . First battery compartment  28  is connected in series with second battery compartment  30  by a second path  40 , and second battery compartment  30  includes an output terminal  42  connected to first path  38  by a third path  44  which third path  44  includes a diode  46  for preventing current flow into the second battery compartment  30 , a battery path enable switch  48  for selectively interrupting third path  44 , a DC/DC voltage regulator  50  for regulating the voltage supplied to first path  38  by the batteries  33 , an EMI filter  52 , a PTC element  54  and a second diode  56 . 
       FIG. 3  also illustrates a controller  58  for determining whether power is being provided from input  12  to output  16  via first path  38  and closing battery path enable switch  48  when sufficient power is not being provided. Controller  58  may be a microcontroller unit (MCU) such as a Silicon Labs C8051F332 MCU, with various input/output pins connected to various circuit elements as described below. The pins of controller  58  are labeled  1 - 20  in  FIG. 3 , and these pins numbers will be referred to hereinafter. 
     Pin  3  of controller  58  is connected to first path  38  by a fourth path  60  which fourth path  60  includes a voltage regulator  62 , such as a National Semiconductor ADJ LDO LP 2951CM, for regulating the voltage supplied to controller  58 . Second path  40  between first battery compartment  28  and second battery compartment  30  includes a node  64  connected to fourth path  60  for providing 6V DC power from the batteries in first battery compartment  28  to voltage regulator  62  and thus to controller  58  when adequate power is not provided from input  12 . Unregulated voltage from first path  38  is also supplied to pin  13  of controller  58  by a mains in line  65 . 
     Battery path enable line  66  connects battery path enable switch  48  to controller pin  16 , and controller  58  controls the state of battery path enable switch  48  by providing appropriate outputs on this line  66 . A battery 6V monitor switch  68  is connected to second path  40  and to controller pin  15  by a battery 6V monitor enable line  70 , and battery 6V monitor switch  68  is controlled by an appropriate output of controller pin  15 . The output of battery 6V monitor switch  68  is connected to controller pin  12  of controller  58  by battery 6V monitor output line  72  allowing controller  58  to receive as an input an indication of the voltage being output from the batteries  33  in first battery compartment  28  and thus an indication of the charge condition of the batteries  33  in the first battery compartment  28 . A battery 12V monitor switch  74  is connected to third path  44  and to controller pin  14  by a battery 12V monitor enable line  76 , and battery 12V monitor switch  74  is controlled by an appropriate output of controller pin  14 . The output of battery 12V monitor switch  74  is connected to controller pin  11  of controller  58  by a battery 12V output line  78  allowing controller  58  to receive as an input an indication of the voltage being output from the batteries  33  in first and second battery compartments  28 ,  30  and thus an indication of the charge condition of the batteries in the first and second compartments  28 ,  30 . When the output of the batteries  33  reaches a level greater than zero but too low to provide adequate power to NIU  18 , controller  58  opens battery path enable switch  48  and shuts off power to the output terminal  16 . 
     A boost reg out line  80  connects a node  82  in third path  44  between DC/DC voltage regulator  50  and EMI filter  52  to controller pin  10 , and a post PTC out line  84  connects a node  86  between PTC element  54  and second diode  56  to controller pin  14  to provide controller  58  with additional information about voltage levels in the system. Controller pins  4  and  5  are connected to data port  36  by lines  88  and  90 , respectively, for allowing communication between data port  36  and controller  58 . First visual indicator  34   a  is connected to controller pin  20 , second visual indicator  34   b  is connected to controller pin  19  and third visual indicator  34   c  is connected to controller pin  18 , and a buzzer  92  is connected to controller port  17  by a switch  94  so that controller  58  can control the first, second and third visual indicators  34   a ,  34   b ,  34   c  and buzzer  92  to provide information about the power source being used by the BBU  10  and the condition of the batteries  33 . 
     Under normal operating conditions, DC power is supplied to BBU input  12  and output from BBU output  16  with power also being supplied to voltage regulator  62  via fourth path  60  and to pin  13  of controller  58  via mains in line  65 . The controller  58  monitors the voltage on first path  38  via mains in line  65  and, if this voltage drops below a predetermined level, a level consistent with the lowest expected normal voltage from power supply  14 , controller  58  closes battery path enable switch  48  within milliseconds of the detected drop to connect output terminal  42  of second battery compartment  30  to BBU output  16  over third path  44  thereby providing a substantially uninterrupted power supply from BBU output  16  even when power ceases to be supplied to first path  38  via BBU input  12 . DC/DC regulator  50 , which may comprise a boost regulator, helps maintain a constant voltage level at BBU output  16  even as the batteries  33  discharge, and the charge level of batteries  33  is detected by controller  58  by periodically closing battery 6V monitor switch  68  and battery 12V monitor switch  74  to obtain voltage readings for the batteries in the first and second battery compartments  28 ,  30  to determine their state of charge and estimated remaining life. 
     While power is being supplied to BBU output  16  by batteries  33 , controller  58  continues to monitor the signal on mains in line  65  to determine when the voltage on first path  38  returns to a high level indicating that power is again being supplied from BBU input  12 . A predetermined time after the voltage on first path  38  returns to an operating level, controller  58  opens battery path enable switch  48  to disconnect the batteries  33  in the first and second battery compartments  28 ,  30  from first path  38 . Generally, battery path enable switch  48  is only opened after a delay, such as 30 seconds, to help avoid repeated switching of the BBU  10  in the event of transient power events, so that battery path enable switch  48  is not opened until it reasonably certain that power supply  14  is again able to reliably supply DC power to the NIU  18  via the BBU  10 . This may also help prevent an oscillating condition that might occur if the mains in voltage level at the mains in pin  13  is approximately equal to the switchover voltage. 
     The first, second and third visual indicators  34   a ,  34   b ,  34   c  may be illuminated in various combinations to provide information such as whether DC power is being provided by power supply  14  or batteries  33  and information on the charge state of the batteries  33 , such as “fully charged”, “partially discharged”, and “end of life” or “fully discharged.” For example, the visual indicators may be illuminated by controller  58  as follows, where first visual indicator  34   a  corresponds to the below “green” LED, second visual indicator  34   b  corresponds to the below “yellow” LED and third visual indicator  34   c  corresponds to the below “red” LED: 
     1. Green—OK (Operating on Main power); 
     2. Green Blinking (1 second every 30 seconds)—Battery backup mode, battery fresh; 
     3. Yellow—Main power, batteries have between 3 hours and 6 hours of back-up time left; 
     4. Yellow Blinking (1 second every 30 seconds)—Battery backup mode, battery has between 3 and 6 hours of back-up time left; 
     5. Red—Main power, battery needs to be replaced. BBU will sound a “chirp” once every 30 seconds (similar to a reminder beep of a smoke detector when battery is exhausted); 
     6. Red Blinking (1 second every 30 seconds)—Battery backup mode, battery has less than 3 hours of time left. BBU will sound a “chirp” once every 30 seconds (similar to a reminder beep of a smoke detector when battery is exhausted; and 
     7. Red Blinking (1 second “on” 1 second “off”)—Battery missing or incorrectly installed (and sufficient power is present to allow the LED&#39;s to be illuminated). 
     If the batteries  33  are depleted to the point where loss of back-up power is imminent, the controller  58  will indicate this condition on the Light Emitting Diode status display, and will also provide an audible alarm via buzzer  92  to alert nearby users of this critical condition. This status information continues to be provided until the batteries  33  are exhausted or replaced by a user. 
     The BBU also has a battery “Test” mode which evaluates the amount of power left in the battery by displaying a “Red-Yellow-Green” power survey. This is activated by the user through a button (not illustrated) on the face plate of the BBU body. When powered from an AC source, no battery power will actually be used to make this evaluation. The batteries are “sensed” and a status of battery health is displayed for a 15 second interval, after which the BBU returns to “normal” mode. This gives the user a more detailed evaluation of the battery condition. 
     By not requiring the BBU  10  to charge batteries, as is commonly done with other backup power supplies, the circuitry required for charging and the associated complexities are eliminated and costs are reduced. As a consequence, no specialized battery charging circuitry or thermal management circuitry is necessary in BBU  10 . As new primary cell technology becomes available, new types of batteries can be substituted directly into the first and second battery compartments  28 ,  30  without modifying the BBU  10 . In addition, by designing around standard cells, there is no need for a custom battery pack or connector. An end user can simply procure standard batteries from any local retail shop and use them in the BBU  10 . A customer is also likely to have spare batteries available. Another benefit of this approach is that as battery technologies change, the technology can be used in the BBU as long as the batteries are within the BBU&#39;s operating voltage. In addition, a customer can still use physically compatible rechargeable batteries in the BBU, but the customer will be responsible for charging those batteries with a conventional battery charger. 
     The present invention has been described herein in terms of a presently preferred embodiment. However, additions and changes to this embodiment will become apparent to those of ordinary skill in the relevant arts upon a reading of the foregoing description. It is intended that all such changes and additions comprise a part of the present invention to the extent they fall within the scope of the several claims appended hereto.