Abstract:
Circuits provide power to network-based devices, such as IP telephones, using spare conductors within existing LAN cables. The circuits, which may comprise diode bridges, are designed to provide power using existing and planned industry guidelines.

Description:
BACKGROUND OF THE INVENTION 
     It used to be that the network which controlled your telephone was different than the network which controlled your computer. In the not-too-distant future, these two networks will become one. For example, so-called “IP telephones” (short for “Internet-Protocol telephones”) will be able to function much like conventional telephones, albeit using unconventional means. That is, IP telephones and other network-based systems will be connected to a network capable of sending and receiving both voice, data and other signals (i.e., video) as Internet-Protocol signals. 
     Separate from the type of information these systems will handle is the issue of how to provide power to them. 
     One way to provide power is to use an electrical outlet. This connects a system to the electric company&#39;s power grid. A second method is to provide power using the same physical conductors (e.g., wires) which handle voice or data information. That is, power supplied by the network itself. This is a more traditional method. 
     Additional methods have also been proposed, all of which use conductors within a network cable which is used to connect a system (e.g., IP telephone,) to the network. 
     For example, a conventional “local area network” (“LAN”) cable which connects an IP telephone to a network contains eight wires. Of the eight wires, four are typically used to transmit and receive voice and data information. These four may also be used to supply power if power is to be supplied over the same wires (i.e., the second method mentioned above) which are providing voice and data information. As is known in the art, this is not always the best way to provide power. Many times it is too complicated to place power on the same wires as data and still preserve the integrity of the data. 
     Alternatively, the remaining four extra or spare wires may be used to supply power only. 
     Specifically, a third method suggests that network-based systems be powered by placing two signals (e.g., voltages) each of opposite polarity (e.g., +V, −V) on two of the remaining four wires. This method is referred to as a “differential mode” or “differential voltage” technique via one pair. 
     The fourth suggested method uses all four of the remaining wires. In this method the same nominal voltage, (i.e., either +V or −V) is placed on two of the remaining wires while a second nominal voltage of opposite polarity is placed on the remaining pair of wires. This method is referred to as a “common mode” or “common voltage” technique via two pairs. 
     Some network-based systems or devices (hereafter collectively referred to as “network-based device”) have been developed which are adapted to be powered using the third method mentioned above. Other network-based devices are being developed which can only be powered using the fourth method just discussed. 
     It is desirable, however, to provide network-based devices which are capable of operating when power is supplied using either method. 
     Other desires will become apparent from the drawings, detailed description of the invention and claims which follow. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, devices (and corresponding methods) which provide power to network-based devices comprise: a first circuit (e.g., a diode bridge made from an integrated circuit or discrete devices) adapted to provide a differential voltage based on input signals of opposite polarity received from a first pair of network pathways (e.g., two of the spare LAN cable wires) or may be used to contribute to the provisioning of a common voltage based on input signals of a first polarity received from the first pair of pathways; and a second circuit adapted to supply the differential voltage based on input signals of opposite polarity received from a second pair of network pathways (e.g., the other pair of spare LAN cable wires) or to contribute to the provisioning of the common voltage based on input signals of a second polarity received from the second pair of pathways. 
     These two circuits may be combined with two additional circuits, one that supplies local power and one that provides both power and communications signals (e.g., voice, data) via other network pathways. Together, such a device provides the ability to power network-based devices (e.g., IP telephones and the like) using existing and planned industry guidelines. 
    
    
     
       BRIEF DESCRIPTION OF THE INVENTION 
         FIG. 1  depicts a technique for providing power to a network-based device, such as an IP telephone, according to one embodiment of the present invention. 
         FIG. 2  depicts a technique for providing power to a network-based device, such as an IP-telephone, according to another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIG. 1 , there is shown a device  10  for providing power to a network-based device  60  according to one embodiment of the present invention. The device  60  may comprise any number of devices which are commonly connected to a network, (e.g., LANs), such as an IP-telephone or a computer. 
     As shown, the device  10  comprises four circuits,  20 , 30 , 40  and  50 . For the sake of clarity, they will be referred to as a first circuit  20 , second circuit  30 , third circuit  40  and fourth circuit  50 , respectively. All four circuits are designed to provide power to the system  60  via pathways  61  and  62 . 
     According to one embodiment of the present invention, the third circuit  40  is adapted to provide “local power” to the network device  60  (e.g., from a wall unit connected to an electrical outlet or the like). The letters “A” and “B” indicate inputs into the third circuit  40 . These inputs may take the form of terminals and/or pathways (e.g., an electrical cord). The fourth circuit  50  is the type of circuit which is adapted to provide both power and communication signals to the device  60 . Both power and communication signals (e.g., voice and data signals) may be input into, and output from, network pathways labeled  1 , 2 , 3  and  6 . As with the third circuit  40 , these pathways may comprise terminals or wires. For example, pathways  1 , 2 , 3  and  6  may be directly connected onto the surface of a printed circuit board within circuit  50  or, alternatively, may comprise a terminal strip where the network pathways  1 , 2 , 3  and  6  “terminate” (i.e., are fastened to . . . ) on one side of the strip. In this instance, other pathways (e.g., wires, conductors) connect the other side of the strip to the circuit  50 . Unlike the third circuit  40 , however, the pathways  1 , 2 , 3  and  6  are network pathways. That is, these pathways are connected to a communications network (not shown) while pathways A and B are local power pathways. They are connected to the local power grid, not to the communications network. Though uncommon, one company may provide both the communications network and power grid to a user of device  10 . 
     It should be noted that the direction that the communication signals are moving is relative. That is, instead of receiving signals via pathways  3 , 6  and transmitting signals via pathways  1 , 2  each direction may easily be reversed. Similarly, when these pathways are used to provide power the polarities of pathways  1 , 2  and  3 , 6  may also be reversed. 
     We turn our attention now to the first and second circuits  20 , 30 . Before doing so, it should be understood that the functions described below with respect to the first circuit  20  may, alternatively, be carried out by the second circuit  30  and vice-versa. That is, the functions carried out by the first and second circuits  20 , 30  are interchangeable. 
     A user of device  10  may designate pathways  7 , 8  as the first circuit and pathways  4 , 5  as the second circuit or vice versa. Pathways  4 , 5  and  7 , 8  are sometimes referred to as “spare” pathways because they typically go unused. For example, in a conventional network cable, which contains eight wires, wires  4 , 5 , 7 , and  8  will not be used. Realizing this, some network-based devices are designed to receive power via pathways  7 , 8 . The term “auxiliary power” is sometimes used to describe the provisioning of power in this manner. In one example of the present invention, pathway  7  comprises a signal whose polarity is different than (i.e., opposite of) the polarity of a signal received via pathway  8 . For example, the signal received along pathway  7  may be of a negative polarity while the signal received via pathway  8  may be of a positive polarity, or vice versa. In another embodiment, the signals typically input into pathways  7 , 8  may be input into pathways  4 , 5  leading to the second circuit  30 . As indicated once before, this technique is known as a differential method via one pair of providing power to the network-based device  60 . Typically, the presence of two signals of opposite polarity at pathways  7 , 8  will result in a voltage (sometimes referred to as a “potential”) being generated by the first circuit  20 . For clarity sake, we will refer to this voltage as a “differential voltage”. 
     It can be said that either the first or second circuits  20 , 30  can be adapted to supply a differential voltage to the network device  60  based on input signals of different polarities received via a pair of network pathways (either  7 , 8  or  4 , 5 ). To distinguish pathways  7 , 8  from  4 , 5  we will refer to pathways  7 , 8  as a “first” pair of pathways and pathways  4 , 5  as a “second” pair of pathways. 
     Recently, various industry associations have recommended another technique for providing power to network-based devices. For example, the “IEEE802.3af DTE Power MDI” task force is working on an amendment to a standard known as “IEEE802.3”. The amendment will specify power over Ethernet networks. This technique requires two pairs of pathways where each pair is adapted to transmit a signal of the same polarity. That is, this technique requires that the signal input into the first circuit  20  via pathways  7 , 8  be of the same polarity (either a positive + or a negative − polarity). The same for pathways  4 , 5 . For example, a signal having a negative polarity is input into device  60  via pathways  7 , 8  while a signal having a positive polarity is input into device  60  via pathways  4 , 5 . 
     Existing network-based devices are not adapted to operate using both techniques. Some are adapted to operate when the signals provided to a single pair of pathways are of opposite polarity while others are adapted to operate when the signals applied to two pairs of terminals are of the same polarity (e.g., −V on pathway  4 , 5  and +V on pathway  7 , 8 ). None are adapted to operate using both techniques. Devices, such as device  10 , envisioned by the present invention are adapted to provide this capability to network-based devices. 
     In one embodiment of the present invention, the first circuit  20  may be adapted to receive input signals via pathways  7 , 8  which are of the same “first” polarity (e.g., positive) while the second circuit  30  is adapted to receive signals via pathways  4 , 5  which are also of a same “second” polarity (e.g., negative). In this manner, both the first and second circuits  20 , 30  are used to generate a voltage which is used to power device  60 . The voltage generated by both the first and second circuits  20 , 30  is referred to as a “common voltage” to distinguish it from the differential voltage mentioned above. 
     Because both circuits  20 , 30  are used in generating the common voltage, it can be said that first and second circuits  20 , 30  are both adapted to contribute to the generation and provisioning (collectively “provisioning”) of the common voltage to the device  60 . 
     For ease of clarification later, as indicated above the polarity of the signals received by the first pair of pathways  7 , 8  will be referred to as a first polarity while the polarity of the signals received by the second pair of pathways  4 , 5  will be referred to as a second polarity. The polarity of the pairs of pathways may be reversed. That is, either pathways  7 , 8  or  4 , 5  may be positive or negative provided each pair of pathways are of opposite polarity. 
     Referring now to  FIG. 2 , there is shown first through fourth circuits  200 - 500  comprising bridge circuits, or more specifically, diode bridges. It should be understood that although  FIG. 2  might illustrate the most common way of representing the first through fourth circuits, it is not the only way. The first through fourth circuits may comprise any number of combinations of discrete, integrated or solid state circuits which are adapted to carry out the functions and features of the first through fourth circuits described above and below. 
     In greater detail, each diode bridge  200 - 500  has two input nodes (e.g.,  401  and  402  in bridge  400 ) and two output nodes (e.g.,  403  and  404 ). Each input-output-node combination is connected through a diode (e.g.,  413 ,  423 ,  442  and  441  in bridge  400 ). Each diode conducts electricity (i.e., sends a signal) in only one direction. One end of each diode is referred to as “P” (for “positive”), while the other is referred to as “N” (for “negative”). The P end of each diode is the “tail” of the arrow which symbolizes a diode and “N” is the point of the arrow. Each diode conducts a signal when the node connected to P is positive with respect to the node connected to N. Conversely, no signal is conducted when the node connected to P is negative with respect to the node connected to N. In the embodiment shown in  FIG. 2 , each diode conducts an electrical current in the direction indicated by the arrow. 
     We will discuss the use of a differential voltage first, followed by a discussion of the use of a common voltage. In an illustrative embodiment of the invention, when a differential voltage is applied to the input nodes  301 , 302  of bridge  300 , signals are conducted as follows. When node  301  is positive with respect to node  302  and a network device  60  is connected to nodes  303 , 304 , diodes  313  and  342  conduct while diodes  341  and  323  do not. This results in a positive signal being brought to an input of device  60 . 
     If, however, node  302  is positive with respect to node  301 , diodes  323  and  341  conduct, while diodes  342  and  313  do not. This scenario again results in a positive signal being brought to an input of device  60 . 
     On the other hand, when a common voltage is applied to input nodes  201 ,  202  of bridge  200  and a common voltage of an opposite polarity is applied to input nodes  301 ,  302  where nodes  203 , 204  are connected to nodes  303 , 304 , signals are conducted as follows. When nodes  201 , 202  are positive with respect to nodes  301 , 302 , diodes  213 ,  223 , 341 , and  342  conduct while diodes  241 , 242 , 313  and  323  do not. The end result being that a positive signal is again brought to an input of device  60 . 
     Finally, if nodes  301 , 302  are positive with respect to nodes  201 , 202 , diodes  313 ,  323 ,  241  and  242  conduct while the remaining diodes do not, once again resulting in a positive signal being brought to an input of device  60 . From  FIG. 2  it can also be seen that the fourth circuit  500 , in addition to comprising a diode bridge  560 , may also comprise transformers  570  and  580  which pass communication signals to outputs “Tx” and “Rx”. As shown, it is the centertaps of the primaries of transformers  570  and  580  which pass to the power bridge  560 . 
     In sum, because both the first and second circuits  200 , 300  are adapted to provide power by generating either a differential voltage or a common voltage, it can be said that devices which make use of first and second circuits envisioned by the present invention are capable of being supplied with power using either a differential or common mode technique. 
     The above discussion is intended to provide some examples of the features and functions of the present invention. It should be understood however, that variations may be made to the examples above without departing from the spirit and scope of the present invention. For example, though device  10  is shown comprising all four circuits this may not be the case. Alternative devices may only comprise first and second circuits or some combination of all four circuits. The true scope of the present invention is defined by the claims which follow.