Patent Publication Number: US-2011077793-A1

Title: Long-distance poe system, power sourcing equipment and power sourcing method

Description:
FIELD OF THE INVENTION 
     The present invention is related generally to a Power over Ethernet (PoE) system and, more particularly, to long-distance PoE power sourcing equipment and method. 
     BACKGROUND OF THE INVENTION 
     Power over Ethernet (PoE) refers to a technology for power transmission over an Ethernet cable, by which electric power can be directly supplied to an Ethernet equipment, for example, Voice-over-IP (VoIP) phone, wireless access point, IP camera, hub, and the like, through an Ethernet cable without using an additional power cord or modifying the structure of the Ethernet cable. In addition to PoE, there have been many other terms referring to the technology for power transmission over an Ethernet cable, for example, Power over LAN (PoL Power on LAN (PoL), and Inline Power, etc. IEEE 802.3-2005 (usually referred to as IEEE 802.3af) is a PoE standard approved by IEEE that is established based on a Category 5 cable (Cat-5), typically referred to as Ethernet cable, with its first, second, third and sixth pairs of twisted wires for data transmission, and its fourth, fifth, seventh and eighth pairs of twisted wires for power transmission. The current PoE technology can only provide direct-current (DC) power sourcing of maximum voltage 48V, maximum current 400 mA, and maximum power 14.4 W. As a PoE power sourcing switch wastes approximately 10%-20% of the supplied power, only about 12.95 W of power is available for use by the PoE network equipments linked to the PoE switch, considering the transmission loss. 
     In further detail, as shown in  FIG. 1 , a PoE system  10  includes a PoE switch  14  as the PoE power sourcing equipment (PSE) and one or more PoE power devices (PDs)  18 , for example, IP camera with PoE function. The Power and data transmission between the PoE switch  14  and the PoE power device  18  is accomplished by an Ethernet cable  16 , and the data transmission between a control console  12 , for example, computer or NB, and the PoE power device  18  must be assisted by the PoE switch  14  therebetween. 
     Since the current PoE technology can only provide available power of less than 13 W for the PoE power devices  18 , it is impossible to support any network equipment having demanded power of more than 13 W, for example, IP camera with pan-tilt-zoom (PTZ) function or spherical type IP camera. The update IEEE 802.3 at standard for PoE, which was approved in 2009, enables its power sourcing specification to be higher, up to 30 W, and thereby reduces the barrier caused by insufficient PoE power sourcing capability; however, the limitation on PoE power transmission distance remains. Referring to  FIG. 1 , due to the limitation of Ethernet, the distance between the PoE switch  14  and the PoE power devices  18  is limited to less than 100 m. If a distance over 100 m is desired, it requires several cascade PoE switches to relay the power and network signals being transmitted. However, as the supplied power attenuates over the transmission distance, the extension of distance actually achieved is still very limited. Moreover, the large number of nodes formed in the cascade architecture makes subsequent maintenance very inconvenient and requires considerable manpower and time for inspection. 
     Therefore, it is desired a long-distance PoE power sourcing equipment and method to overcome the above drawbacks. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a long-distance PoE power sourcing equipment. 
     Another object of the present invention is to provide a long-distance PoE power sourcing method. 
     A further object of the present invention is to provide a long-distance PoE system. 
     According to the present invention, a long-distance PoE system includes a PoE local power supply to receives an AC or DC power source and communicates with a control console outside the PoE system by a network signal, a PoE remote switch, a link cable linked between the PoE local power supply and the PoE remote switch for communication between the PoE local power supply and the PoE remote switch by a first transmission signal, a PoE power device, and an Ethernet cable linked between the PoE remote switch and the PoE power device for communication between the PoE remote switch and the PoE power device by a second transmission signal. The PoE local power supply sources a first DC power to the PoE remote switch through the link cable, the PoE remote switch converts the first DC power into a second DC power supplied to the PoE power device through the same Ethernet cable, and the first DC power has a higher voltage than the second DC power. 
     According to the present invention, a long-distance PoE power sourcing equipment includes a PoE local power supply to serve as a conversion medium between a network signal and a first transmission signal and to provide a first DC power, a link cable connected to the PoE local power supply to provide a transmission path for the first transmission signal and the first DC power, and a PoE remote switch connected to the link cable to serve as a conversion medium between the first transmission signal and a second transmission signal and to convert the first DC power into a second DC power having a voltage lower than that of the first DC power. 
     According to the present invention, a long-distance PoE power sourcing method includes generating a first DC power, transmitting a first transmission signal and the first DC power to a remote end, converting the first transmission signal into a second transmission signal and converting the first DC power into a second DC power at the remote end, and transmitting the second transmission signal and the second DC power to a PoE power device. The first DC power has a higher voltage than the second DC power. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other objects, features and advantages of the present invention will become apparent to those skilled in the art upon consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a block diagram of a conventional PoE system; 
         FIG. 2  a block diagram showing a long-distance PoE architecture according to the present invention; 
         FIG. 3  a block diagram of a PoE local power supply according to the present invention; and 
         FIG. 4  a block diagram of a PoE remote switch according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As shown in  FIG. 2 , in a long-distance PoE system  20  according to the present invention, a PoE local power supply  26 , a PoE remote switch  28 , and a link cable  30  linked therebetween establish a long-distance PoE power sourcing equipment  24 , and each PoE power device  18  is linked to the PoE remote switch  28  by a Ethernet cable  16 . The link cable  30  may be a twisted-pair line, a telephone line, an Ethernet cable, or a coaxial cable. A control console  12  for the PoE system  20  is linked to the PoE local power supply  26  by an Ethernet cable  22  or via a network environment, and the communication between the control console  12  and the PoE local power supply  26  is accomplished by a network signal S 0  over the Ethernet cable  22  or a network environment. Between the PoE local power supply  26  and the PoE remote switch  28  is transmitted a first transmission signal S 1  over the link cable  30 , and between the PoE remote switch  28  and the PoE power device  18  is transmitted a second transmission signal S 2  over the Ethernet cable  16 . The PoE local power supply  26  serves as a conversion medium between the network signal S 0  and the first transmission signal S 1 , to convert the network signal S 0  into the first transmission signal S 1  or to convert the first transmission signal S 1  into the network signal S 0 . The PoE remote switch  28  serves as a conversion medium between the first transmission signal S 1  and the second transmission signal S 2 , to convert the first transmission signal S 1  into the second transmission signal S 2  or to convert the second transmission signal S 2  into the first transmission signal S 1 . The PoE local power supply  26  also sources a first DC power DC 1  to the PoE remote switch  28  over the link cable  30 , and the PoE remote switch  28  converts the first DC power DC 1  into a second DC power DC 2  according to the PoE specification. The second DC power DC 2  is supplied to the PoE power device  18  over the Ethernet cable  16 . The first DC power DC 1  has a higher voltage than that of the second DC power DC 2 . Although the Ethernet cable  16  is still shorter than 100 m due to the distance limitation of the Ethernet specification, the power transmission implemented by the PoE local power supply  26  and the link cable  30  allows the power transmission distance of the PoE local power supply  26  to extend beyond 100 m without need of any other cascade PoE switch. In an embodiment, a Cat-5 cable is used as the Ethernet cable  16 , in which the first, second, third and sixth pairs of twisted wires are used for transmitting the second transmission signal S 2 , and the fourth, fifth, seventh and eighth pairs of twisted wires are used for transmitting the second DC power DC 2 . Hence, the PoE power device  18  can operate normally as long as it is connected to the Ethernet cable  16 . 
       FIG. 3  shows an embodiment for the PoE local power supply  26 , which includes a RJ45 jack  32  to communicate with the control console  12  over the Ethernet cable  22  or connect with a network environment, a link cable interface  34  to connect to the PoE remote switch  28  through the link cable  30 , a signal converter  36  connected to the RJ45 jack  32  to convert the network signal S 0  into the first transmission signal S 1  or vice versa, a power input  40  to be connected with an AC or DC power source, for example a commercial power source of ±90˜240V, a power converter module  38  connected to the power input  40  to convert the AC or DC source power to an internal DC power  42  supplied to the signal converter  36  and a first DC power  44  to be combined with the first transmission signal S 1  at a joint  52  to be transmitted from the link cable interface  34  to the PoE remote switch  28 . The first transmission signal S 1  from the PoE remote switch  28  is fed into the signal converter  36  via the link cable interface  34  and the joint  52 . The signal converter  36  includes an Ethernet PHY chip  46  connected to the RJ45 jack  32 , an xDSL chip  48  connected to the Ethernet PHY chip  46 , and an analog front end  50  connected the xDSL chip  48  and the joint  52 . The network signal S 0  from the control console  12  is received by the Ethernet PHY chip  46  from the RJ45 jack  32  and modulated by the xDSL chip  48  into an xDSL signal, which is then sent from the analog front end  50  to the joint  52  as the first transmission signal S 1  to be transmitted to the PoE remote switch  28 . Conversely, the first transmission signal S 1  from the PoE remote switch  28  is received by the analog front end  50  via the joint  52 , demodulated by the xDSL chip  48 , and then sent from the Ethernet PHY chip  46  to the RJ45 jack  32 . 
       FIG. 4  shows an embodiment for the PoE remote switch  28 , in which a link cable interface  54  is to connect to the PoE local power supply  26  through the link cable  30 , the first DC power DC 1  received from the PoE local power supply  26  is provided to a power converter  58  via a joint  56 , where the first DC power DC 1  is converted into an internal DC power  62  supplied to a signal converter  60  and a second DC power  64  supplied to a set of PoE jacks  72 , and the first transmission signal S 1  received from the PoE local power supply  26  is fed via the joint  56  into the signal converter  60  to be converted into the second transmission signal S 2  to transmit to the PoE jacks  72 . The signal converter  60  includes an analog front end  66  connected to the joint  56 , an xDSL chip  68  connected to the analog front end  66 , and an Ethernet PHY chip  70  connected to the xDSL chip  68  and the PoE jacks  72 . The first transmission signal S 1  from the PoE local power supply  26  is received by the analog front end  66  via the junction  56 , demodulated by the xDSL chip  68 , and then sent from the Ethernet PHY chip  70  to the PoE jacks  72  as the second transmission signal S 2 . Conversely, the second transmission signal S 2  from the power device  18  is received by the Ethernet PHY chip  70  via the PoE jacks  72 , modulated by the xDSL chip  68  into an xDSL signal, and then sent from the analog front end  66  to the joint  56  as the first transmission signal S 1  to be transmitted to the PoE local power supply  26 . In this embodiment, the second DC power DC 2  is converted from the first DC power DC 1  according to the PoE specification, and the second transmission signal S 2  also conforms to the PoE specification. 
     As shown in  FIGS. 3 and 4 , the first transmission signal S 1  between the PoE local power supply  26  and the PoE remote switch  28  is an xDSL modulated signal, whose transmission distance follows the xDSL specification. Taking VDSL for example, the transmission distance can be as long as several hundred meters, which is longer than the 100 m limitation of the Ethernet specification. 
     While the present invention has been described in conjunction with preferred embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and scope thereof as set forth in the appended claims.