Abstract:
An apparatus and method for enabling Cisco legacy power to support IEEE 802.3 AF standard power. A network power system capable of delivering data terminal equipment power via a media dependent interface includes power source equipment according to Cisco legacy power and at least one powered device according to IEEE standard power. A power compatibility module is inserted between the power source equipment and the powered device to enable the power source equipment to appear according to IEEE standard power and the powered device to appear according to Cisco legacy power. The module includes switches, a DC/DC converter, an IEEE power source equipment circuit, and an isolator. The module optionally includes a user signaling device for communicating operating conditions of the module to a user. The module may be connected to two ports of the power source equipment to supply adequate power levels to the powered device.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates generally to a network power system including power source equipment, at least one powered device, and transmission media. More specifically, the present invention relates to a network power system including non-IEEE standard power source equipment and at least one IEEE standard powered device.  
         BACKGROUND OF THE INVENTION  
         [0002]    In the field of networks, there are instances when it is desired or required that data terminal equipment (DTE) be able to draw power from the same generic cabling as that used for data transmission. DTE devices may include telephones, Voice over Internet Protocol (VoIP or IP or Ethernet) telephones, network access devices, computers, and the like. Such a power scheme is known as phantom power or power via a media dependent interface (MDI). Various example power via MDI schemes exist. These include a proprietary scheme from Cisco Systems, Inc. (Cisco) and a standard scheme from the Institute of Electrical and Electronics Engineers (IEEE). The proprietary scheme from Cisco will be referred to as Cisco legacy power. The IEEE scheme is known as IEEE 802.3af standard power and will be referred to as IEEE standard power. Although the two schemes have some aspects in common, they are not entirely compatible with one another.  
           [0003]    Turning first to FIG. 1, a schematic diagram of a network power system  10  having power source equipment (PSE)  12 , a plurality of powered devices (PD)  14 A-N, and a plurality of corresponding transmission media  16 A-N is shown. The plurality of transmission media  16 A-N are connected to the corresponding power source equipment  12  and powered devices  14 A-N through a power interface at each end of the transmission media. Each transmission media may contain a plurality of conductors. For example, the current Ethernet standard is a minimum of two twisted-pair cables for a total of four conductors. The length and routing of the transmission media will depend on the circumstances and the applicable communications protocol. The number and location of each of the plurality of powered devices  14 A-N will depend on the circumstances. The power source equipment  12  may also be variously located based on the circumstances. The multiple power interfaces of the power source equipment  12  are often referred to as ports. The number of ports will vary. Typically, one port is connected to one powered device. The multiple transmission media are often referred to as links between the power source equipment and the various powered devices. Each link includes at least two data and power signal paths with one for transmitting and one for receiving. In order for the network power system  10  to operate correctly, the power source equipment  12  and the plurality of powered devices  14 A-N must be compatible with one another.  
         BRIEF DESCRIPTION OF THE INVENTION  
         [0004]    An apparatus and method for enabling Cisco legacy power to support IEEE 802.3af standard power is disclosed. A network power system capable of delivering data terminal equipment power via a media dependent interface includes power source equipment according to Cisco legacy power and at least one powered device according to IEEE standard power. A power compatibility module is inserted between the power source equipment and the powered device to enable the power source equipment to appear according to IEEE standard power and the powered device to appear according to Cisco legacy power. The module includes switches, a DC/DC converter, an IEEE power source equipment circuit, and an isolator. The module optionally includes a user signaling device for communicating operating conditions of the module to a user. The module may be connected to two ports of the power source equipment to supply adequate power levels to the powered device.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0005]    The accompanying drawings, which are incorporated into and constitute a part of this specification, illustrate one or more exemplary embodiments of the present invention and, together with the detailed description, serve to explain the principles and exemplary implementations of the invention.  
         [0006]    In the drawings:  
         [0007]    [0007]FIG. 1 is a schematic diagram of a network power system having power source equipment, a plurality of powered devices, and a plurality of corresponding transmission media;  
         [0008]    [0008]FIG. 2 is a schematic diagram according to Cisco legacy power of the power source equipment as in FIG. 1;  
         [0009]    [0009]FIG. 3 is a schematic diagram according to IEEE standard power of the powered device as in FIG. 1; and  
         [0010]    [0010]FIG. 4 is a schematic diagram of an embodiment of a power compatibility module according to the present invention.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0011]    Various exemplary embodiments of the present invention are described herein in the context of an apparatus and method for enabling Cisco legacy power to support IEEE standard power. Those of ordinary skill in the art will realize that the following detailed description of the present invention is illustrative only and is not intended to be in any way limiting. Other embodiments of the present invention will readily suggest themselves to such skilled persons having the benefit of this disclosure. Reference will now be made in detail to exemplary implementations of the present invention as illustrated in the accompanying drawings. The same reference indicators will be used throughout the drawings and the following detailed descriptions to refer to the same or like parts.  
         [0012]    In the interest of clarity, not all of the routine features of the exemplary implementations described herein are shown and described. It will of course, be appreciated that in the development of any such actual implementation, numerous implementation-specific decisions must be made in order to achieve the specific goals of the developer, such as compliance with application- and business-related constraints, and that these specific goals will vary from one implementation to another and from one developer to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking of engineering for those of ordinary skill in the art having the benefit of this disclosure.  
         [0013]    In the context of the present invention, the term “network” includes local area networks (LANs), wide area networks (WANs), the Internet, cable television systems, telephone systems, wireless telecommunications systems, fiber optic networks, ATM networks, frame relay % networks, satellite communications systems, and the like. Such networks are well known in the art and consequently are not further described herein.  
         [0014]    Turning now to FIG. 2, a schematic diagram according to Cisco legacy power of the power source equipment  12  as in FIG. 1 is shown. In the interest of clarity, only the pertinent portions of one power interface are shown. The remaining power interfaces are similar. The power source equipment  12  includes a power source equipment (PSE) physical layer  20 , a network power controller (NPC)  22 , an output power voltage (VPWR)  24 , a switch  26 , a PSE transmit (TX) magnetic  28 , and a PSE receive (RX) magnetic  30 . The NPC  22  monitors the output power voltage  24  and regulates the voltage level through the switch  26 . The NPC regulated power is applied to the PSE transmit and receive magnetics  28  and  30 . During data communication, a series of output data signals are generated and a series of input data signals are received. The signals may be simultaneous or alternating. An output data signal is generated by the PSE physical layer  20  and applied to the PSE transmit magnetic  28  for transmission to a powered device connected to the port. For example, the powered device might be the first powered device  14 A of FIG. 1 that is connected to the power source equipment  12  by the first transmission media  16 A of FIG. 1. An input data signal that is generated by the powered device connected to the port is received by the PSE receive magnetic  30  and passed to the PSE physical layer  20 . The power source equipment  12  performs many functions which may include searching the link for a PD, supplying power to the link only if a PD is detected, monitoring the power on the link, and removing power from the link when the PD is disconnected. How these functions are performed differs from Cisco legacy power to IEEE standard power and accounts for some of the incompatibility between the two power schemes.  
         [0015]    Turning now to FIG. 3, a schematic diagram according to IEEE standard power of the powered device  14  as in FIG. 1 is shown. Similar to above, only the pertinent portions of the power interface are shown. The powered device  14  includes a powered device (PD) physical layer  32 , an IEEE PD integrated circuit (IC)  34 , a power converter  36 , a first capacitor C 1 , a second capacitor C 2 , a PD RX magnetic  38 , and a PD TX magnetic  40 . The IEEE PD IC  34  is a chip that performs the PD functions of the power scheme according to IEEE standard power. During data communication, a series of input data signals are received and a series of output data signals are generated. The signals may be simultaneous or alternating. An input data signal that is generated by the power source equipment is received by the PD receive magnetic  38  and passed to the PD physical layer  32 . An output data signal is generated by the PD physical layer  32  and applied to the PD transmit magnetic  40  for transmission to the power source equipment. The IEEE PD IC  34  receives the input phantom power over the link and passes it to the power converter  36  which generates one or more power levels. The power level may depend in part on which classification of device the powered device  14  is according to IEEE standard power. IEEE standard power has a number of power classes and Cisco legacy power does not. This represents potentially one more of the incompatibilities. However, PD classification is not strictly necessary at this time. Nevertheless, the power demands of some of IEEE power classes may be beyond the power supply capabilities of the power source equipment according to Cisco legacy power which does represent an incompatibility between the two power schemes. The various incompatibilities of the power source equipment according to Cisco legacy power and the powered devices according to IEEE standard power can substantially be addressed.  
         [0016]    Turning now to FIG. 4, a schematic diagram of an embodiment of a power compatibility module  50  according to the present invention is shown. The module  50  is inserted into the link between the power source equipment and the powered device. One convenient location would be closely before the powered device. It would also be possible to incorporate the module  50  into the powered device making the powered device both Cisco legacy power and IEEE standard power compatible. Rather than one module  50  for each powered device, it would also be possible to combine several modules  50  together. The module  50  includes switches  52 , an optional filter  54 , a DC/DC converter  56 , an IEEE power source equipment integrated circuit (PSE IC)  58 , an isolator  60 , six capacitors C 4 -C 9 , eight inductors L 1 -L 8 , and an optional LED  1 . The switches  52  and optional filter  54  play roles in how the power source equipment according to Cisco legacy power detects a compatible phantom powered device using differential mode signaling. The switches  52  are controlled by the IEEE PSE IC  58  which is a chip that performs the PSE functions of the power scheme according to IEEE standard power. The switches  52  and the IEEE PSE IC  58  work together to enable the power source equipment and the powered device to work together. The switches  52  help to make the powered device according to IEEE standard power to appear as a powered device according to Cisco legacy power. Likewise, the IEEE PSE IC  58  helps to make the power source equipment according to Cisco legacy power to appear as a power source equipment according to IEEE standard power. The isolator  60  works with the IEEE PSE IC  58  in accordance with IEEE standard power. The DC/DC converter  56  performs functions such as boosting the input phantom power voltage and isolating the input from the output. Depending on the circumstances, it may be the case that the voltage level supplied by the power source equipment according to Cisco legacy power is too low for the power class of the powered device according to IEEE Standard power. The DC/DC converter  56  will correct for the under voltage condition. The optional LED  1  could be employed as a user signaling device to signal various operating conditions of the module  50  to the user. The LED states of on, off, or flashing could be used to indicate proper or improper functioning. For example, the off state might indicate no power flow, the on state might indicate power flow, and the flashing state might indicate insufficient or intermediate power flow. More than one LED might also be provided to further indicate various link conditions such as short or open.  
         [0017]    As mentioned above, the power demands of some of the IEEE power classes may be beyond the power supply capabilities of the power source equipment according to Cisco legacy power. One solution is to decline to support such power classes. In this case, the optional LED  1  might be used to signal the user that the module  50  is unable to power the connected powered device. Another solution is to combine the power of two ports from the power source equipment. This can be accomplished by connecting two ports to the input of the module  50  and one powered device to the output of the module  50 . In this case, the optional LED  1  might be used to signal the user that the power demand at the output of the module  50  is actually greater or is classed to be greater than the power supplied at the input of the module  50 . This would indicate to the user that if only one input is connected, then a second input might be necessary. The power supplied by two ports should be sufficient for any of the power classes that are compliant with IEEE standard power.  
         [0018]    As an alternative to the embodiment of FIG. 4, it would be possible to change control of the switches  52  from the IEEE PSE IC  58  to the user. In such a case, the control line to the IEEE PSE IC  58  could be deleted and an on demand user control such as a button would be added. To establish power, the user would press and hold the button that closed the switches  52  until the LED  1  indicated that proper power was flowing to the PD. After proper power flow had been established, then the user would release the button and thereby the switches  52  would return to a normally open position. As above, the filter  54  is optional.  
         [0019]    As a further alternative to the embodiment of FIG. 4, it would be possible to locate the DC/DC converter  56  inside of the powered device rather than inside of the module  50  as shown. In such a case, the DC/DC converter  56  and the capacitor C 5  would be deleted from the module  50  and the input of the IEEE PSE IC  58  would be connected across the capacitor C 4 .  
         [0020]    While embodiments and applications of this invention have been shown and described, it would be apparent to those skilled in the art having the benefit of this disclosure that many more modifications than mentioned above are possible without departing from the inventive concepts herein. The invention, therefore, is not to be restricted except in the spirit of the appended claims.