BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a power control method in a data communication network. 
     2. Background of the Related Art 
     A data communication network may be described as a communication network which connects at least two computers for allowing a number of people to share data. Data communication networks typically include a local area network which connects adjacent computers at high speed and a wide area network having internal exchanges for connecting computers worldwide. Examples include a telephone network, a broadcasting network, and a computer communication network. 
     Data communication networks can be classified into a local area network (LAN), a wide area network (WAN), a value added network (VAN) and an integrated services digital network (ISDN) according to scale and function. A LAN is a narrow range communication network typically found in a place of business or in a building. The standard LAN includes Ethernet, Token Ring, and FDDI. The WAN is a wide area data transmission communication network which may include a few LANs. The VAN is a communication network added with a variety of information such as accumulation and supply of information, variations of a communication speed and format, and selection of a communication path. The ISDN is an integrated service digital communication network which collectively handles communication-related services such as a telephone, fax, data communication, videotex, etc. 
     Data communication networks often include a hub for connecting a plurality of terminals. The hub transmits downloaded data to a corresponding terminal, and uploaded data from the respective terminals to an external network through an Ethernet switch. Recently, a Powered-HUB has been proposed which can supply power to each terminal as well as transmit/receive data. 
       FIG. 1  is a diagram illustrating a related art Ethernet device. In this device, a Powered-HUB  13  receives data from an Ethernet switch  11 , transmits the data to a user terminal, and supplies power to one of a plurality of user terminals which needs power. Here, the user terminals may include a web camera  19 , an IP phone  21 , and a wireless LAN access point  23 . If desired, a personal computer  25  may be connected to the IP phone. The user terminals may be connected to the Powered-HUB  13  through unshielded twisted pair (UTP) cables  15  to  17  to supply data and power. Both ends of each UTP cables  15  to  17  may include RJ-45 jacks for establishing connection between the Powered-HUB and a respective user terminal. In general, Pins  1 ,  2 ,  3  and  6  of the RJ-45 jacks are used to transmit/receive data, and the other pins, namely pins  4 ,  5 ,  7  and  8 , are used to supply power. 
     The above-described Ethernet device guarantees compatibility between the Powered-HUB and the user terminals. In this case, the Powered-HUB and the user terminals respectively have modules for confirming necessity of power and use a special protocol for mutual communication. 
     When the Powered-HUB and the user terminals are incompatible, external splitters must be positioned between user terminals  19 ,  21  and  23  and the Powered-HUB  13  as shown in  FIG. 2 . The external splitters are data/power splitters  27  to  29  for respectively branching data and power from the Powered-HUB, and transmitting them to each terminal through data only lines and power only lines. 
     The related art Ethernet device has a number of drawbacks. For example, the conventional Ethernet device requires a special module and protocol to supply power from the Powered-HUB to the user terminals. This increases the complexity of the entire system. Furthermore, in the case that the Powered-HUB and the user terminals are not compatible with each other, the data/power splitters must be installed between the Powered-HUB and the respective user terminals. This further complicates the system design and increases costs. 
     SUMMARY OF THE INVENTION 
     An object of the invention is to solve at least the above problems and/or disadvantages and to provide at least the advantages described hereinafter. 
     Accordingly, one object of the present invention is to provide a power control method in a data communication network which can supply power by using vibrators of each terminal. 
     It is another object of the present invention to provide a power control method in a data communication network which can control supply or switching of power according to vibration signals of vibrators. 
     The foregoing and other objects and advantages are realized by providing a power control method for deciding whether to supply power according to a vibration signal from a user terminal during a check period having a first check period for deciding whether to supply power and a second check period for deciding whether to keep supplying power. 
     The vibration signal is generated at predetermined intervals when a Powered-HUB and the user terminal are connected. 
     When the number of the vibration signals is identical to the number of setup signals during the first check period, power is supplied. In addition, when the number of the vibration signals is identical to the number of the setup signals during the second check period, power is continuously supplied. When the number of the vibration signals is not identical to the number of the setup signals during the second check period and the second check period is changed to the first check period at the same time, power is switched. 
     According to another aspect of the invention, a power control method in a data communication network includes: deciding whether to supply power by using a vibration signal from a user terminal during a first check period in a check period having a first check period of a low level and a second check period of a high level; deciding whether to keep supplying power by using the vibration signal from the user terminal during the second check period when the first check period is changed to the second check period; and switching power when the second check period is changed to the first check period in a state where whether to keep supplying power has not been decided during the second check period. 
     The step for deciding whether to supply power during the first check period includes the steps of: increasing a value of a clock counter according to detection of a rising event from the vibration signal; comparing a value of the clock counter with a setup value of the clock counter; and supplying power when the value of the clock counter is identical to the setup value of the clock counter. 
     The step for deciding whether to keep supplying power during the second check step includes the steps of: increasing a value of a connection counter according to detection of a rising event from the vibration signal; comparing a value of the connection counter with a setup value of the connection counter; and keeping supplying power when the value of the connection counter is identical to the setup value of the connection counter. 
     According to further another aspect of the invention, a power control method in a data communication network includes: receiving at least one vibration signal from a user terminal through an UTP cable; increasing a value of a clock counter and deciding whether the value of the clock counter is identical to a setup value of the clock counter, whenever a rising event of the vibration signal is detected from at least one vibration signal during a first check period for deciding whether to supply power; switching on a relay according to a power supply signal generated when the value of the clock counter is identical to the setup value of the clock counter; supplying power to the user terminal through the UTP cable when the relay is switched on; increasing a value of a connection counter and deciding whether the value of the connection counter is identical to a setup value of the connection counter, whenever a rising event of the vibration signal is detected from at least one vibration signal during a second check period for deciding whether to keep supplying power; maintaining the on state of the relay according to a power maintenance signal generated when the value of the connection counter is identical to the setup value of the connection counter; and continuously supplying power to the user terminal through the UTP cable when the relay is maintained on. 
     The power control method in a data communication network, further includes the steps of: switching off the relay according to a power switching signal generated when the number of the vibration signals is not identical to the number of the setup signals and the second check period is changed to the first check period; and stopping supplying power supplied to the user terminal when the relay is switched off. 
     According to still another aspect of the invention, a power control apparatus in a data communication network includes: a user terminal for transmitting at least one vibration signal generated when a UTP cable is connected thereto; a power control means for comparing the number of the vibration signals with the number of setup signals and outputting a control signal according to the comparison result during a check period having a first check period for deciding whether to supply power and a second check period for deciding whether to keep supplying power; a switching means for switching on/off a relay according to the control signal; and a power generating means for generating power supplied to the user terminal according to the on/off operation of the switching means. 
     The power control means includes: a clock counter for calculating the number of the vibration signals during the first check period; and a connection counter for calculating the number of the vibration signals during the second check period. 
     Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objects and advantages of the invention may be realized and attained as particularly pointed out in the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be described in detail with reference to the following drawings in which like reference numerals refer to like elements wherein: 
         FIG. 1  is a view illustrating a related art Ethernet device; 
         FIG. 2  is a view illustrating the related art Ethernet device in a state where a Powered-HUB and user terminals are not compatible; 
         FIG. 3  is a structure view illustrating a power control apparatus in accordance with a preferred embodiment of the present invention; 
         FIG. 4  is a structure view illustrating RJ-45 jack pins in accordance with the preferred embodiment of the present invention; 
         FIG. 5  is a view illustrating a check period for deciding whether to supply or keep supplying power in accordance with the preferred embodiment of the present invention; 
         FIG. 6  is a flowchart showing a method for supplying power by the power control apparatus in accordance with the preferred embodiment of the present invention; and 
         FIG. 7  is a flowchart showing a method for controlling power according to a vibration signal by a power control means of the power control apparatus in accordance with the preferred embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     The following detailed description will present a preferred embodiment of the invention in reference to the accompanying drawings. 
       FIG. 3  is a diagram showing a power control apparatus in accordance with one embodiment of the present invention. This apparatus includes a plurality of user terminals which request power supply when they need power, and Powered-HUB  71  which supplies power in response to the power supply request from the plurality of user terminals. Here, the plurality of user terminals are exemplified as a first terminal  31 , a second terminal  41 , and a third terminal  51 . The first terminal  31  includes a vibrator  33  for generating a vibration signal used as a power supply request signal. Vibrator  33  generates the vibration signal when a UTP cable is connected thereto. That is, when the UTP cable is connected to the first terminal  31 , the first terminal  31  drives vibrator  33  to generate the vibration signal. The second terminal  41  does not have a vibrator. Such a terminal uses a self-power source and thus does not need to receive power from the Powered-HUB  71 . The third terminal  51  does not have a vibrator either. The third terminal  51  does not have a vibrator because it is not compatible with the Powered-HUB  71 . In order to use a user terminal like terminal  51  which is not compatible with the Powered-HUB  71 , an RJ-45 extension module  55  having a vibrator  57  for generating the vibration signal must be installed between the third terminal  51  and the Powered-HUB  71 . When the RJ-45 extension module  55  is connected to the third terminal  51  or the Powered-HUB  71  through the UTP cable, the RJ-45 extension module  55  recognizes cable connection to the third terminal, and drives vibrator  57  to generate the vibration signal. 
     The UTP cable is a connection cable for requesting/supplying power as well as transmitting/receiving data. Preferably, it is positioned between the user terminal and the Powered-HUB  71 . Both ends of the UTP cables have RJ-45 jacks  61  to  66  connected to the user terminals and the Powered-HUB. That is, one side RJ-45 jacks  61  to  63  of the UTP cables are connected to respective communication ports of the user terminals, and the other side RJ-45 jacks  64  to  66  are connected to respective communication ports of the Powered-HUB. Accordingly, each of the user terminals includes one communication port, but the Powered-HUB  71  includes as many communication ports as the plurality of user terminals to connect the user terminals. 
     Referring to  FIG. 4 , the RJ-45 jacks  61  to  66  may include eight pins. Pins  1 ,  2 ,  3  and  6  may be used but the other pins  4 ,  5 ,  7  and  8  pins may not be used. In accordance with an example of the present invention, the unused pins (namely pins  4 ,  5 ,  7  and  8 ) can be employed to supply power. That is, pins  1  and  2  of the RJ-45 jacks  61  to  66  are used to transmit data, and pins  3  and  6  are used to receive data. In addition, pin  4  may be used for the vibration signal, pin  5  may be used for DC power, and pins  7  and  8  pins may be used for grounding. It is emphasized that the aforementioned pin numbers are merely illustrative and thus are not intended to be limiting of the present invention. If desired, the number of pins and/or pin assignments may be varied. 
     Referring to  FIG. 3 , the Powered-HUB includes a power control unit  73  for outputting a control signal for controlling power by using the vibration signal from the user terminal, a switching unit  75  for switching on/off a relay according to the control signal, and a power generating unit  79  for generating power to be supplied to the user terminal according to the on/off operation of the switching unit  75 . 
     The power control unit  73  is preferably a programmable logic device (PLD). A check period for deciding whether to supply or keep supplying power in each period may be implemented in the power control unit  73 . As shown in  FIG. 5 , the check period may be divided into a first check period and a second check period. The first check period is a period for deciding whether to supply power, and the second check period is a period for deciding whether to keep supplying power. The first check period may have a check state of a low level and the second check period may have a check state of a high level. 
     The power control unit  73  may include a clock counter  74   a , a connection counter  74   b , and a power supply register  74   c . Here, the clock counter counts a rising event detected from the vibration signal from the user terminal during the first check period, and the connection counter counts a rising event detected from the vibration signal from the user terminal during the second check period. 
     When the power control unit  73  checks the vibration signal from the user terminal during the first check period and decides to supply power, the power supply register is set up as ‘0’. Here, ‘0’ indicates a power supply signal. When the power supply register is set up as ‘0’, the power control unit  73  supplies the power supply signal, namely ‘0’ to the switching unit  75 . When a value of the clock counter counted by detecting the rising event from the vibration signal is identical to a setup value of the clock counter, power is supplied. 
     When the power control unit  73  checks the vibration signal from the user terminal during the second check period and decides to keep supplying power, the power supply register is not set up but maintained as it is. The power control unit  73  then supplies a power maintenance signal to the switching unit  75 . When a value of the connection counter counted by detecting the rising event from the vibration signal is identical to a setup value of the connection counter, power is continuously supplied. 
     When the value of the connection counter is different from the setup value of the connection counter and the second check period is changed to the first check period, the power supply register is set up as ‘1’. Here, ‘1’ indicates a power switching signal. When the power supply register is set up as ‘1’, the power control unit supplies the power switching signal, namely ‘1’ to the switching unit  75 . 
     The switching unit may have as many relays  76 ,  77 ,  78  as the plurality of RJ-45 jacks connected to the plurality of communication ports of the Powered-HUB  71 . Each of the relays of the switching unit is switched on/off according to the control signals from the power control unit, namely the power supply signal, power maintenance signal, and power switching signal. 
     On the other hand, a power generating unit  79  for generating power to be supplied through the relays can be formed at the front terminal of the switching unit  75 . The power generating unit may generate a predetermined DC voltage (e.g., 48V). 
     As previously described, when the Powered-HUB receives the vibration signal from the user terminal, it confirms the check period, counts the number of the vibration signals by using the rising events of the vibration signals, compares the value of the counter with the setup value of the counter, decides whether to supply power, keeps supplying power or switches power, switches on/off the switching unit  75  according to the resultant control signal, and supplies power. 
       FIG. 6  is a flowchart showing steps included in a method for supplying power by the power control apparatus in accordance with the present invention. The method includes as an initial step confirming in the user terminal whether the UTP cable is connected thereto (step  81 ). Here, the user terminal has the vibrator for generating a vibration signal. As explained above, both ends of the UTP cable have RJ-45 jacks. One side jack of the UTP cable is connected to the user terminal, and the other side jack is connected to the Powered-HUB  71  or RJ-45 extension module  55 . The UTP cable is also connected between the RJ-45 extension module  55  and the Powered-HUB  71 . When the user terminal is not compatible with the Powered-HUB, the RJ-45 extension module transmits the vibration signal to the Powered-HUB through an internal vibrator, e.g., vibrator  57 . 
     When it is determined that the UTP cable is connected to the user terminal, the user terminal recognizes the cable connection, drives the internal vibrator to generate the vibration signal, and transmits the vibration signal to the Powered-HUB through the UTP cable (step  82 ). 
     The Powered-HUB receives the vibration signal from the user terminal and performs a power control operation (step  83 ), which will now be explained in detail. 
       FIG. 7  is a flowchart showing steps included in a method for controlling power according to the vibration signal by the power control unit of the power control apparatus in accordance with the present invention. As previously described, the check period for deciding whether to supply power or keep supplying power in each period exists in the Powered-HUB. That is, the check period is divided into the first check period and the second check period. Whether to supply power is decided during the first check period, and whether to keep supplying power is decided during the second check period. Referring to  FIG. 7 , the Powered-HUB  71  confirms whether the check period is the first check period or the second check period (step  84 ). 
     When the check period is the first check period, whether to supply power is decided. The power control unit  73  detects the rising event from the vibration signal from the user terminal (step  85 ). Here, the rising event indicates a jump portion from the low to high level in one vibration signal. 
     When the rising event is detected from the vibration signal, the value of the clock counter is increased (step  86 ). Preferably, the value of the clock counter is increased by ‘1’ whenever the rising event is detected from the vibration signal. When the rising event is not detected, it implies that the vibration signal is not received. The power control unit  73  confirms reception of the vibration signal by confirming the check period. 
     The Powered-HUB  71  compares the increased value of the clock counter with the setup value of the clock counter (step  87 ). When the value of the clock counter is not identical to the setup value of the clock counter, the routine goes to step  84 . 
     When the value of the clock counter is identical to the setup value of the clock counter, power supply is decided. The power control unit  73  sets up the power supply register as ‘0’ (step  88 ). Here, ‘0’ indicates the power supply signal. 
     The power supply unit  73  outputs the power supply signal to the switching unit  75  of  FIG. 3  (step  89 ). 
     When the check period is not the first check period but the second check period, the power control unit detects the rising event from the vibration signal from the user terminal (step  90 ). When the rising event is detected from the vibration signal, the value of the connection counter is increased (step  91 ). Preferably, the value of the connection counter is increased by ‘1’. 
     The powered control unit  73  compares the value of the connection counter with the setup value of the connection counter (step  92 ). When the value of the connection counter is identical to the setup value of the connection counter, power is continuously supplied. The power control unit  73  does not set up the power supply register but maintains it as it is (step  93 ). Therefore, the power control unit  73  outputs the power maintenance signal to the switching unit  75  (step  94 ). 
     When the value of the connection counter is different from the setup value of the connection counter in step  92 , the power control unit  73  confirms whether the check period is changed (step  95 ). That is, the power control unit  73  confirms whether the second check period is changed to the first check period. 
     When the check period is not changed, the routine goes to step  90  to detect the rising event from the succeeding vibration signal. 
     However, when the second check period is changed to the first check period, it implies that it does not exist in the period for deciding whether to keep supplying power. The power control unit  73  sets up the power supply register as ‘1’ (step  96 ). Here, ‘1’ indicates the power switching signal. 
     The power control unit  73  outputs the power switching signal set up in the power supply register to the switching unit  75  (step  97 ). 
     Still referring to  FIG. 6 , when the power control unit  73  controls power in step  83 , whether to supply power and whether to keep supplying power are decided in each check period according to the rising event of the vibration signal, and the resultant signals, namely the power supply signal, power maintenance signal and power switching signal are outputted. 
     The control signal is inputted to the switching unit  75 , and the switching unit  75  switches on/off the corresponding relay according to the control signal (step  98 ). That is, when the control signal from the control unit is the power supply signal, the switching unit  75  switches the relay on, when the control signal is the power maintenance signal, the relay is maintained on, and when the control signal is the power switching signal, the switching unit  75  switches the relay off. 
     Here, the relay corresponds to the UTP cable connected to the user terminal generating the vibration signal. That is, the UTP cable and the relay correspond to each other as explained above. Therefore, when the power supply signal is outputted in response to the vibration signal inputted to the Powered-HUB through a specific UTP cable among the plurality of UTP cables, the switching unit switches on the relay corresponding to the specific UTP cable, and power inputted through the relay is supplied to the user terminal connected to the UTP cable. 
     The power control unit sets up power generated in the power generating unit  79  according to the on/off state of the relay (step  99 ). That is, when the relay is switched on or maintained on, the power control unit  73  supplies power to the user terminal through the relay, and when the relay is switched off, power generated in the power generating unit  79  is not passed through the relay due to the off state of the relay, and thus not supplied to the user terminal. 
     On the other hand, when the UTP cable is connected to the user terminal which does not have the vibrator for generating the vibration signal like the second terminal  41  of  FIG. 3 , the Powered-HUB  71  does not receive the vibration signal, and thus the rising event of the vibration signal is not detected in step  85  or  90  of  FIG. 7 . Accordingly, whether to supply power or keep supplying power is not decided, and thus power is not supplied to the second terminal  41 . In this case, the user terminal can receive power by using a self-power source or adapter. 
     As discussed earlier, in accordance with the present invention, the power control apparatus includes a vibrator for generating a vibration signal for reflecting the connection state of the UTP cable, thereby forming a simplified structure which does not require a special module. As a result, the structure of the network is simplified. 
     Moreover, the power control apparatus supplies power after deciding whether to supply or keep supplying power by using the vibration signal, and thus reduces power consumption as compared with when power is uniformly supplied to power/data splitters through the Powered-HUB. In addition, the RJ-45 extension module having the vibrator for generating the vibration signal is installed between the Powered-HUB and a user terminal which is not compatible with the Powered-HUB. Through this module, the application range of the power control apparatus may be substantially extended. As a result, the power control apparatus and the method of the present invention may be applied to any kind of network or system which needs to supply power to user terminals. 
     The foregoing embodiments and advantages are merely exemplary and are not to be construed as imitating the present invention. The present teaching can be readily applied to other types of apparatuses. The description of the present invention is intended to be illustrative, and not to limit the scope of the claims. Many alternatives, modifications, and variations will be apparent to those skilled in the art.
An apparatus and method controls power supplied from a powered HUB to a user terminal includes based on a vibration signal transmitted from the terminal. Initially, a connection between the HUB and terminal is determined to exist if at least one vibration signal is received from the terminal. Then, a determination is made as to when the signal is received. If received during a first check period, power is supplied from the HUB to the terminal. If received during a second check period, power continues to be supplied to the terminal. Power is cut-off when a number of vibration signals or vibration-signal events does not equal a predetermined number and the second check period transitions into the first check period. By taking these steps, the need to use specialized modules and communications protocols is eliminated, thereby reducing costs and system complexity.