Patent Publication Number: US-2016238649-A1

Title: Small form-factor pluggable module with ground fault detection circuitry

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is related to, and claims the priority benefit of, U.S. Provisional Patent Application Ser. No. 62/117,318 filed Feb. 17, 2015, the contents of which are hereby incorporated in their entirety into the present disclosure. 
    
    
     TECHNICAL FIELD OF THE DISCLOSED EMBODIMENTS 
     The presently disclosed embodiments generally relate to network communication modules, and more particularly, to a small form factor pluggable module with ground fault detection circuitry. 
     BACKGROUND OF THE DISCLOSED EMBODIMENTS 
     Generally, commercial fire alarm systems include fire alarm control panels networked together or networked with other fire alarm equipment including terminals or workstations. The network utilized by the fire alarm control panel may be an Ethernet network as governed by the IEEE 802.3 standard. The 802.3 standard governs the physical layer (layer 1) and media access control (MAC) of the data link layer (layer 2) in Ethernet. Devices such as data switches, hubs, and routers, provide the nodes and infrastructure of the Ethernet. The 802.3 standard requires isolation between ground and the Ethernet cabling for safety and also isolation from port to port. Intentional direct current paths to ground from the Ethernet cabling are not permitted under the 802.3 standard. 
     The Standard for Control Units and Accessories for Fire Alarm Systems (UL 864, 9th Edition) presently governs all fire alarm control panels and connected equipment. To comply with UL 864, devices used with a fire alarm control panel for control applications should be capable of reporting earth ground connections that have the potential to affect system performance. There is therefore need in the art for a fire alarm control panel utilizing an Ethernet connection that may detect such earth ground connections. 
     SUMMARY OF THE DISCLOSED EMBODIMENTS 
     In one aspect, a fire alarm control panel is provided. The fire alarm control panel includes an Ethernet network interface card and a small form-factor pluggable (SFP) module in communication with the Ethernet network interface card. 
     The network interface card includes a card ground fault detection circuit. The card ground fault detection circuit includes a first resistive component and a second resistive component. One side of the first resistive component is in electrical communication with a system power source, and the other side of the first resistive component is in electrical communication with one side of the second resistive component to form a card reference point. The other side of the second resistive component is in electrical communication with a card circuit common connection. In one embodiment, the first resistive component and the second resistive component include a resistive value greater than or equal to approximately 100 kilo ohms. The card ground fault detection circuit further includes a card switching device. One side of the card switching device is in electrical communication with the card reference point, and the other side of card switching device is in electrical communication with a chassis ground connection. The card ground fault detection circuit further includes a comparator circuit and a card microcontroller unit. The input of the comparator circuit is in electrical communication with the card reference point, and the output of the comparator circuit is in electrical communication with the card microcontroller unit. 
     The SFP module includes a module ground fault detection circuit. In one embodiment, the module ground fault detection circuit includes at least one switching device. One side of the at least one switching device is in electrical communication with a center tap of at least one Ethernet transformer, and the other side of the at least one switching device is in electrical communication with one side of a module resistive component. In one embodiment, the at least one Ethernet transformer is selected from the group consisting of a transmitter transformer and a receiver transformer. The other side of the module resistive component is in electrical communication with a module circuit common connection. 
     In the same embodiment, the module ground fault detection circuit further includes a module microcontroller unit in operable communication with the at least one switching device. The module microcontroller is in further communication with the card microcontroller unit via a data connection. 
     In another embodiment, the module ground fault detection circuit includes at least one Ethernet transformer, a first module resistive component, including a first module resistive component value, in communication with a second module resistive component, including a second module resistive component value, to form a module reference point, the first module resistive component in further communication with an isolated voltage to form an isolated voltage reference point, and the second module resistive component in further communication with an earth ground connection, a module switching device in communication with the module reference point, the module switching device in further communication with a ground connection, a module operational amplifier circuit in communication with the module reference point a module microcontroller unit in communication with the operational amplifier circuit and the card microcontroller unit, an isolator circuit in communication with the module microcontroller unit, a converter circuit in communication with the isolated voltage reference point in further communication with the module microcontroller unit, a third module resistive component, including a third module resistive component value, in communication with a center tap of the at least one Ethernet transformer and the isolated voltage reference point, and a fourth module resistive component, including a fourth module resistive component value, in communication with a center tap of the at least one Ethernet transformer and an earth ground connection. In one embodiment, the first resistive component, the second resistive component, the third resistive component, and the fourth resistive component include a resistive value greater than or equal to approximately 100 kilo 
     In one aspect, a method of detecting a ground fault within a network of devices including an Ethernet interface card including a card ground fault detection circuit and a SFP module in communication with the Ethernet interface card, the SFP module including a card ground detection circuit is provided. The method includes the step of operating the card ground fault detection circuit to enter a detection mode. In one embodiment, operating the card ground fault detection circuit to enter a detection mode includes operating a card switching device to be placed in a closed position. 
     The method further includes the step of operating the module ground fault detection circuit to enter a detection mode. In one embodiment, operating the module ground fault detection circuit to enter a detection mode includes operating at least one module switching device to be placed in a closed position. 
     In one embodiment, the method includes the step of operating the module ground fault detection circuit to communicate a ground fault to the Ethernet network interface card if a ground fault is detected. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The embodiments and other features, advantages and disclosures contained herein, and the manner of attaining them, will become apparent and the present disclosure will be better understood by reference to the following description of various exemplary embodiments of the present disclosure taken in conjunction with the accompanying drawings, wherein: 
         FIG. 1  illustrates a schematic diagram of a network including a small form-factor pluggable module ground detection circuit according to one embodiment of the present disclosure; 
         FIG. 2  illustrates a schematic diagram of a network including a small form-factor pluggable module ground detection circuit according to another embodiment of the present disclosure; 
         FIG. 3  illustrates a schematic flow diagram of a method for detecting a ground fault within a network according to one embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE DISCLOSED EMBODIMENTS 
     For the purposes of promoting an understanding of the principles of the present disclosure, reference will now be made to the embodiments illustrated in the drawings, and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of this disclosure is thereby intended. 
       FIG. 1  illustrates an embodiment of a network, generally indicated at  10 . The network includes a first fire alarm control panel  12  in communication with a second fire alarm control panel  12  via an Ethernet connection  14 . It will be appreciated that the first fire alarm control panel  12  may also be in communication with a workstation (not shown), for example a computer configured to monitor the fire alarm system of a building, to name one non-limiting example. 
     The fire alarm control panel  12  is configured to monitor one or more detectors. The detectors may include fire detectors, smoke detectors, radiation detectors, heat detectors, carbon monoxide detectors, ozone detectors and/or other gas detectors, to name a few non-limiting examples, and may provide an indication of an alarm condition. The fire alarm control panel  12  is also configured to monitor manual alarm triggers, such as a pull device, push button triggers, and glass break triggers to name a few non-limiting examples. The fire alarm control panel  12  may include a user interface, memory, and microprocessor (not shown). The fire alarm control panel  12  may be implemented as software on a personal computer or as a standalone piece of hardware. 
     The fire alarm control panel  12  includes an Ethernet network interface card  16  and a small form-factor pluggable (SFP) module  18  in communication with the Ethernet network interface card  16 . For example the SFP module  18  may be inserted into a port on the Ethernet network interface card  16  to provide the Ethernet connection  14  within the network  10   
     The network interface card  16  includes a card ground fault detection circuit  20 . The card ground fault detection circuit  20  includes a first resistive component  22  and a second resistive component  24 . One side of the first resistive component  22  is in electrical communication with a system power source, for example 24 VDC to name one non-limiting example. The other side of the first resistive component  22  is in electrical communication with one side of the second resistive component  24  to form a card reference point  26 . The other side of the second resistive component  24  is in electrical communication with a card circuit common connection  28 . In one embodiment, the first resistive component  22  and the second resistive component  24  include a resistive value greater than or equal to approximately 100 kilo ohms. It will be appreciated that the first resistive component  22  and the second resistive component  24  may have a resistive value less than approximately 100 kilo ohms. The card ground fault detection circuit  20  further includes a card switching device  30 . One side of the card switching device  30  is in electrical communication with the card reference point  26 , and the other side of card switching device  30  is in electrical communication with a chassis ground connection  32 . The card ground fault detection circuit  20  further includes an operational amplifier circuit  34  and a card microcontroller unit  36 . The input of the comparator circuit  34  is in electrical communication with the card reference point  26 , and the output of the comparator circuit  34  is in electrical communication with the card microcontroller unit  36 . It will be appreciated that the card microcontroller unit  36  may include an integrated analog-to-digital converter. 
     During operation of the card ground fault detection circuit  20 , the first card resistive component  22  and the second card resistive component  24  create a voltage reference from the system power at card reference point  26 . The reference voltage at reference point  26  is monitored by the microcontroller unit  36 . When the card switching device  30  is placed in a closed position, any resistance from any field wiring to the network interface card  16  will appear in parallel with either the first card resistive component  22  or the second card resistive component  24 ; thus, causing a detectable shift in the reference voltage. A shift of adequate size will indicate the presence of a ground fault. 
     In the embodiment shown in  FIG. 1 , the SFP module  18  includes a module ground fault detection circuit  40 . The module ground fault detection circuit  40  includes at least one switching device  42 . It will be appreciated that the at least one switching device  48  may include a relay to name one non-limiting example. One side of the at least one switching device  42  is in electrical communication with a center tap of at least one Ethernet transformer  44 , and the other side of the at least one switching device  42  is in electrical communication with one side of a module resistive component  46 . In one embodiment, the at least one Ethernet transformer  44  is selected from the group consisting of a transmitter transformer and a receiver transformer. The transmitter transformer is configured to transmit signals to the Ethernet network interface card  16 . The receiver transformer is configured to receive signals from the Ethernet network interface card  16 . The other side of the module resistive component  46  is in electrical communication with a module circuit common connection  48 . 
     In the embodiment shown, the module ground fault detection circuit  40  further includes a module microcontroller unit  50  in operable communication with the at least one switching device  42 . The module microcontroller unit  50  is configured to operate the at least one switching device  42  between an open position and closed position. For example, the module microcontroller unit  50  is configured to open and close the at least one switching device  42  to close the connection from the center tap of the at least one Ethernet transformer  44  to the module circuit common connection  48 . The module microcontroller  50  is in further communication with the card microcontroller unit  36  via a data connection  52 . The card microcontroller unit  36  and the module microcontroller unit  50  are configured to send and receive control signals via the data connection  52 . 
     In another embodiment, as shown in  FIG. 2 , the module ground fault detection circuit  40 ′ includes a first module resistive component  54  and a second module resistive component  56 . One side of the first module resistive component  54  is in electrical communication with an isolated voltage, designated as V ISO , for example 24 VDC to name one non-limiting example, to form an isolation reference point  55 . The other side of the first module resistive component  54  is in electrical communication with one side of the second module resistive component  56  to form a module reference point  58 . The other side of the second module resistive component  56  is in electrical communication with an earth ground  60 . It will be appreciated that the first module resistive component  54  and the second module resistive component  56  may have a resistive value greater than or equal to approximately 100 kilo ohms. 
     The module ground fault detection circuit  40 ′ further includes a module switching device  62 . One side of the module switching device  62  is in electrical communication with the module reference point  58 , and the other side of module switching device  62  is in electrical communication with a chassis ground connection  64 . The module ground fault detection circuit  40 ′ further includes a module operational amplifier circuit  66  and the module microcontroller unit  50 . The module microcontroller unit  50  is configured to operate the module switching device  62  between an open position and closed position. The input of the module operational amplifier circuit  66  is in electrical communication with the module reference point  58 , and the output of the module comparator circuit  66  is in electrical communication with the module microcontroller unit  50 . The module microcontroller  50  is also in communication with an output of an isolator circuit  68 . The input of the isolator circuit is in communication with the card microcontroller unit  36  via a data connection  52 . The module microcontroller  50  is in further electrical communication with the isolation reference point  55 . The isolation reference point  55  is in electrical communication with an output of a converter circuit  70 , for example a DC/DC converter to name one non-limiting example. Another output of the converter circuit is in electrical communication with earth ground  72 . One input of the converter circuit  70  is in communication with the system power, and another input is in electrical communication with a circuit common connection  74 . The card microcontroller unit  36  and the module microcontroller unit  50  are configured to send and receive control signals via the data connection  52 . 
     One side of a third module resistive component  76  is in electrical communication with a center tap of at least one Ethernet transformer  44 , and the other side of a third module resistive component  76  is in electrical communication with the isolation reference point  55 . One side of a fourth module resistive component  78  is in electrical communication with a center tap of at least one Ethernet transformer  44 , and the other side of a fourth module resistive component  78  is in electrical communication with an earth ground  80 . 
       FIG. 3  illustrates a method of detecting a ground fault within the network  10 , generally indicated at  100 . The method  100  includes the step  102  of operating the card ground fault detection circuit  20  to enter a detection mode. In one embodiment, operating the card ground fault detection circuit  20  to enter a detection mode includes operating the card switching device  30  to be placed in a closed position. For example the microprocessor (not shown) of the fire alarm control panel  12  sends a signal commanding the card switching device  30  to be placed in a closed position. It will be appreciated that the processor may send the signal commanding the card switching device  30  to be placed in a closed position at pre-determined intervals or randomly. 
     The method further includes the step  104  of operating the module ground fault detection circuit  40  or  40 ′ to enter a detection mode. It will be appreciated that the module ground fault detection circuit  40  or  40 ′, within each SFP module  18  of the system  10 , may enter a detection mode simultaneously or each ground fault detection circuit  40  or  40 ′ within each SFP module  18  may be selectively isolated for individual testing. In one embodiment, operating the module ground fault detection circuit  40  or  40 ′ to enter a detection mode includes operating the at least one module switching device  42  or  62  to be placed in a closed position. It will be appreciated that the module ground fault detection circuit  40  or  40 ′ may enter a detection mode at pre-determined intervals or randomly. For example, in the embodiment shown in  FIG. 1 , the processor sends a signal to the module microcontroller unit  50  to place either or both of the at least one module switching devices  42  in a closed position. In the embodiment shown in  FIG. 2 , the module microcontroller unit  50  commands the module switching device  62  to be placed in a closed position. Once the at least one switching device  42  or  62  is placed in a closed position, any resistance to earth ground will appear in parallel with the first card resistive component  22  and the second card resistive component  24 ; thus, indicating that a ground fault has occurred. 
     In one embodiment, the method includes the step  106  of operating the module ground fault detection circuit  40  or  40 ′ to communicate a ground fault to the Ethernet network interface card  16  if a ground fault is detected. For example, if it is determine that a field wiring connection indicates a ground fault, the module microcontroller unit  50  communicates a signal to the card microcontroller unit  36  via the data connection  52 . Once a ground fault is communicated, a signal (either an audio or visual signal to name a couple of non-limiting examples) may be communicated to alert the appropriate personnel that a fault has occurred. 
     It will therefore be appreciated that the present embodiments include a ground fault detection circuit  40  or  40 ′ within a SFP module  18  to reduce the overall cost and conserve space within a fire alarm control panel  12 , and simplifies the communication of ground fault detections that may occur within the system  10 . 
     While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only certain embodiments have been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected.