Abstract:
A charging device includes: a plurality of main relays forming a connection between an electric vehicle (EV)-side connector and an outlet-side connector; a relay welding sensing unit connected to the plurality of relays to sense the presence or absence of welding of the plurality of relays; a welding monitoring relay opening and closing between the relay welding sensing unit side node and a main relay side node; and a control unit controlling the open and close of the welding monitoring relay.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Pursuant to 35 U.S.C. §119(a), this application claims the benefit of earlier filing date and right of priority to Korean Patent Application No. 10-2014-0121998, filed on Sep. 15, 2014, the contents of which are hereby incorporated by reference herein in its entirety. 
     BACKGROUND 
     The present disclosure relates to the charge of an electric vehicle. 
     Electric vehicles mean vehicles operating by using electricity and may be roughly divided into a battery-powered electric vehicle (EV) and a hybrid electric vehicle (HEV). The battery-powered EV is a vehicle running by using only electricity without using fossil fuel and is generally named as an EV. In addition, the HEV means a vehicle running by using electricity and fossil fuel. In addition, the EV includes a battery supplying electricity for running. In particular, the battery-powered EV and a plug-in type HEV uses power supplied from an external power supply to charge a battery and uses power charged in the battery to operate an electric motor. 
     In general, a relay is being used in order to control power supply from a high-voltage battery pack to a motor. 
     For example, the EV or the hybrid vehicle includes the relay installed between the battery pack and a high-voltage circuit part in order to control power supply from the high-voltage battery pack to the high-voltage circuit part. In addition, the connection or disconnection between the high-voltage circuit part and the battery pack is performed by the relay according to a vehicle control state. 
     In this example, the reason why the relay is used is to ensure electric complete insulation between an energy storage medium and other systems, in which case electric stability is ensured because the relay is shorted and power is supplied when a vehicle is in operation, and the relay is open in a key off, maintenance or emergency state. Also, when a first accident occurs, an electric shock resulting from a high voltage or a second accident that is serious, such as fire is prevented, and dark current from the battery pack is blocked. 
     Therefore, when the relay has welding due to an over-current, an abnormal current flows in a battery system and thus a dangerous situation occurs. 
     As an example, in the case of the hybrid vehicle, the back electromotive force of a motor is generated according to engine RPM when a motor controller goes wrong, so a situation in which a battery is over-charged occurs. In this case, when the battery is over-charged, a battery control unit opens the relay in order to protect the battery but when the relay is welded for other reasons despite an open command by the control unit, there is a possibility that fires occurs or a vehicle explodes due to continuous over-charge. 
     Thus, it is important for safety to detect whether there is welding on relays connected to the battery pack in battery systems for various electric vehicles HEV, PHEV, and EV or an energy storage system (ESS). 
     SUMMARY 
     Embodiments provide an apparatus and method for preventing power from being unnecessarily consumed, differently for a charge state in which there is no need to determine welding and a non-charge state in which there is a need to determine the presence or absence of welding, in determining whether a main relay connected in parallel on the same path among relays in a battery pack has been welded. 
     In one embodiment, a charging device includes: a plurality of main relays forming a connection between an electric vehicle (EV)-side connector and an outlet-side connector; a relay welding sensing unit connected to the plurality of relays to sense the presence or absence of welding of the plurality of relays; a welding monitoring relay opening and closing between the relay welding sensing unit side node and a main relay side node; and a control unit controlling the open and close of the welding monitoring relay. 
     The control unit may control the open and close of the welding monitoring relay according to whether the charge of the EV is completed. 
     The control unit may open the welding monitoring relay during the charge of the EV, and close the welding monitoring relay when the charging is ended. 
     The control unit may determine that the main relay has welding, if it is sensed that the charge of the EV is ended but the main relay is still closed. 
     The relay welding sensing unit may determine whether the main relay has welding, based on the amount of current passing through the relay welding sensing unit. 
     The relay welding sensing unit may determine whether the main relay has welding, based on the amount of current passing through the relay welding sensing unit in a normal state. 
     The relay welding sensing unit may include a photo coupler. 
     The photo coupler may include a light emission unit emitting light when current flows, and a light reception unit receiving light from the light emission unit to change the received light to an electrical signal. 
     The relay welding sensing unit may cross a main path connected to the front and rear ends of the main relay to be connected thereto. 
     An end of the welding monitoring relay may be connected to the front end of the main relay, and another end of the welding monitoring relay may be connected to the relay welding sensing unit. 
     The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features will be apparent from the description and drawings, and from the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a conceptual view of a charging system for an electric vehicle (EV} according to an embodiment. 
         FIG. 2  is a block diagram of an electric device according to an embodiment. 
         FIG. 3  is a block diagram of an EV charge cable assembly according to an embodiment. 
         FIG. 4  is a block diagram of a sensing unit according to an embodiment. 
         FIG. 5  is a block diagram of a terminal device according to an embodiment. 
         FIG. 6  is a ladder diagram showing an operating method of an EV charging system according to an embodiment. 
         FIG. 7  is a conceptual view of a charging system for an EV according to another embodiment. 
         FIG. 8  is a block diagram of an EV charge cable assembly according to another embodiment. 
         FIG. 9  is a block diagram of an add-on communication device according to an embodiment. 
         FIG. 10  is a ladder diagram showing an operating method of an EV charging system according to another embodiment. 
         FIG. 11  is a ladder diagram showing an operating method of an EV charging system  10  according to another embodiment. 
         FIGS. 12 and 13  are block diagrams of a welding sensing unit in a charge cable assembly  20  for a typical EV. 
         FIG. 14  is a block diagram of a welding sensing device in the charge cable assembly  20  for an EV according to the present disclosure. 
         FIG. 15  is a flowchart of a process of sensing the presence or absence of welding through a welding monitoring relay  280  in the charge cable assembly  20  for an EV. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Some embodiments are described below in more detail with reference to the accompanying drawings. Since the suffixes “module” and “unit” for components used in the following description are given and interchanged for easiness in making the present disclosure, they do not have distinct meanings or functions. 
     Mobile terminals described in the present disclosure may include cellular phones, smart phones, laptop computers, digital broadcasting terminals, personal digital assistants (PDAs), portable multimedia players (PMPs), and navigation devices. However, a person skilled in the art may easily appreciate that a configuration according to an embodiment described herein may be applied not only to the mobile terminal but also to a fixed terminal, such as a digital TV, desktop computer, and so on. 
     In the following, a first embodiment of a charging system for an electric vehicle (EV) according to the present disclosure is described in more detail with reference to the accompanying drawings. 
       FIG. 1  is a conceptual view of a charging system for an EV according to an embodiment. 
     Referring to  FIG. 1 , an EV charging system  10  according to an embodiment includes an EV  100 , an EV charge cable assembly  20 , a socket  30 , and a terminal device  300 . 
     The socket  30  supplies alternating current (AC) power supplied from a grid. 
     The EV  100  is connected to the socket  30  through the EV charge cable assembly  20  to receive the AC power from the socket  30 . 
     The EV charge cable assembly  20  transmits the AC power from the socket  30  to the EV  100 . 
     The for the EV charge cable assembly  20  includes a cable-use charge control device  200 , an EV connector  51 , an EV-side power cable  53 , a plug  65 , and a grid-side power cable  63 . 
     The EV-side power cable  53  and the grid-side power cable  63  transmit power. 
     The EV connector  51  may be inserted into an EV inlet  120  to be coupled to thereto and conform to the SAE J1772 standard. 
     The plug  65  is inserted into the socket to be coupled thereto. 
     The cable-use charge control device  200  monitors the charge of the EV  100 , provides charge related information obtained from the monitoring, to the terminal device  300  and controls the charge of the EV  100 . 
     In an embodiment, the cable-use charge control device  200  is integrally attached to the power cable  53  so that it is not easily decoupled from the EV-side power cable  53  by a user, and has characteristics resistant to external temperature, external humidity, vibration and shock. 
     In an embodiment, the cable-use charge control device  200  may include a connector to be capable of being coupled to and decoupled from the EV-side power cable  53  by a user. In this case, the connector needs to have characteristics resistant to external temperature, external humidity, vibration and shock. 
     In an embodiment, the cable-use charge control device  200  is integrally attached to the power cable  63  so that it is not easily decoupled from the EV-side power cable  63  by a user, and has characteristics resistant to external temperature, external humidity, vibration and shock. 
     In an embodiment, the cable-use charge control device  200  may include a connector to be capable of being coupled to and decoupled from the EV-side power cable  63  by a user. In this case, the connector needs to have characteristics resistant to external temperature, external humidity, vibration and shock. 
     When the cable-use charge control device  200  includes a connector for wired communication, it may be vulnerable to external conditions because the connector includes a metal terminal. In order to solve such a limitation, the cable-use charge control device  200  may transmit charge related information to the terminal device  300  wirelessly. 
     The terminal device  300  performs contactless, wireless communication with the EV charge cable assembly  20  and displays information on the EV charge cable assembly  20 . 
       FIG. 2  is a block diagram of an electronic device according to an embodiment. 
     An EV  100  includes a battery  110 , a battery charging device  115 , an EV inlet  120 , a communication unit  130 , and a control unit  140 . 
     The battery  110  supplies power for the operation of the EV  100  to the EV  100 . 
     The EV inlet  120  is a connector for externally receiving power for the charge of the battery  110 . The EV inlet  120  may conform on the SAE J1772 standard. 
     The battery charging device  115  uses power supplied through the EV inlet  120  to charge the battery  110 . 
     The communication unit  130  may communicate with the EV charge cable assembly  20  or the terminal device  300 . 
     The control unit  140  controls the overall operations of the EV  100 . 
       FIG. 3  is a block diagram of an EV charge cable assembly according to an embodiment. 
     The EV charge cable assembly  20  includes a cable-use charge control device  200 , an EV-side power cable assembly  50 , and a grid-side power cable assembly  60 . 
     In the following, the EV-side power cable assembly  50  and the grid-side power cable assembly  60  is also referred to as a sub cable assembly. 
     The EV-side power cable assembly  50  includes an EV connector  51 , an EV-side power cable  53 , and an EV-side data communication cable  55 . 
     The grid-side power cable assembly  60  includes a connector  61 , a grid-side power cable  63 , and a plug  65 . 
     The cable-use charge control device  200  includes a connector  205 , at least one relay  220 , a sensing unit  230 , an EV communication unit  240 , a terminal device communication unit  250 , a storage unit  260  and a control unit  270 . 
     The connector  205  is coupled to the connector  61 . The connector  205  supports coupling to and decoupling from the connector  61 . That is, the connector  205  may be coupled to and decoupled from the connector  61 . 
     The at least one relay  220  controls the connection between the EV-side power cable  53  and the grid-side power cable  63 . In particular, when the at least one relay  220  is turned off, it breaks the connection between the EV-side power cable  53  and the grid-side power cable  63 . When the at least one relay  220  is turned on, it electrically connects the EV-side power cable  53  and the grid-side power cable  63 . 
     The sensing unit  230  senses EV charge related information as will be described below. In particular, the sensing unit  230  may also sense both information on the EV  100  and information on the EV charge cable assembly  20 . The sensing unit  230  may also sense information on the EV charge cable assembly  20 , and not information on the EV  100 . 
     The EV communication unit  240  performs communication with the EV  100 . In particular, the EV communication unit  240  performs communication with the communication unit  130  in the EV  100 . The EV communication unit  240  and the communication unit  130  may use a power cable communication method to perform communication through the power cable  53 . Also, the EV communication unit  240  and the communication unit  130  may also use an Infrared Data Association (IrDA) communication technology, a Radio Frequency communication technology, Bluetooth, Ultra Wideband (UWB), ZigBee, Digital Living Network Alliance (DLNA), and so on to perform communication. 
     The terminal device communication unit  250  performs communication with the terminal device  300 . In particular, the terminal device communication unit  250  performs communication with a communication unit  310  in the terminal device  300 . In particular, the terminal device communication unit  250  and the communication unit  310  may also use an Infrared Data Association (IrDA) communication technology, a Radio Frequency communication technology, Bluetooth, Ultra Wideband (UWB), ZigBee, Digital Living Network Alliance (DLNA), and so on to perform communication. 
     The storage unit  260  stores pieces of information to be described below. In particular, the storage unit  260  may store EV charge related information. The storage unit  260  may store information on the usage history of the cable-use charge control device  210 . For example, the storage unit  260  may store information on the last usage time and time length and accumulated usage time length of the cable-use charge control device  210 . 
     The control unit  270  controls the overall operations of the cable-use charge control device  200 , including operations to be described below. 
       FIG. 4  is a block diagram of a sensing unit according to an embodiment. 
     As shown in  FIG. 4 , the sensing unit  230  may include a relay welding sensing unit  231 , a current sensing unit  232 , an internal temperature sensing unit  233 , an internal humidity sensing unit  234 , an external temperature sensing unit  235 , an external humidity sensing unit  236 , a short sensing unit  237 , a disconnection sensing unit  238 , and an allowable current sensing unit  239 . 
     The relay welding sensing unit  231  may sense the presence or absence of the welding of at least one relay  220 . 
     The current sensing unit  232  may sense the size of a current flowing through the power cable  53 . 
     The internal temperature sensing unit  233  may sense the internal temperature of the EV charge cable assembly  20 . 
     The internal humidity sensing unit  234  may sense the internal humidity of the EV charge cable assembly  20 . 
     The external temperature sensing unit  235  senses the ambient temperature of the cable-use charge control device  200 . 
     The external humidity sensing unit  236  senses the ambient humidity of the cable-use charge control device  200 . 
     The short sensing unit  237  may sense the presence or absence of a short of the EV charge cable assembly  20 . 
     The disconnection sensing unit  238  may sense the presence or absence of the disconnection of the EV charge cable assembly  20 . 
     The allowable current sensing unit  239  may include a first allowable current sensing unit and a second allowable current sensing unit. 
     The first allowable current sensing unit senses the allowable current of the EV-side power cable assembly  50 . In particular, the first allowable current sensing unit senses the allowable current of the EV-side power cable  53 . 
     The second allowable current sensing unit senses the allowable current of the grid-side power cable assembly  60 . In particular, the second allowable current sensing unit senses the allowable current of the grid-side power cable. 
       FIG. 5  is a block diagram of a terminal device according to an embodiment. 
     A terminal device  300  includes a communication unit  310 , an input device  320 , a control unit  330 , and a display unit  340 . 
     The communication unit  310  communicates with the terminal device communication unit  250 . 
     The input device  320  obtains a user input. The input device  320  may include one or more of a touch screen, a physical button, a microphone for obtaining a user input having a voice form, an acceleration sensor for obtaining the motion gesture of the terminal device  30  as a user input, a keyboard, a mouth, and a keypad. 
     The control unit  330  controls the overall operations of the terminal device  300  including operations to be described below. 
     The display unit  340  displays information on the charge operation and state of the cable-use charge control device  200 . Also, the display unit  340  may display information on the fault of the cable-use charge control device  200  and on user actions corresponding thereto. For example, the display unit  340  may display the information on the charge operation and state of the cable-use charge control device  200 , by using a visual display method including at least one of a character, figure and light and/or by using an audio output method including sound. 
       FIG. 6  is a ladder diagram showing an operating method of an EV charging system  10  according to an embodiment. 
     A control unit  330  of a terminal device  300  obtains a user input for commanding an EV charge cable assembly  20  through an input device  320  in step S 101 . In this case, the user input for the control of the EV charge cable assembly  20  may include one or more of the charge start of the EV  100 , the charge stop of the EV  100  and a request for EV charge related information. 
     The control unit  330  of the terminal device  300  transmits a command corresponding to the obtained user input to a cable-use charge control device  200  through a communication unit  310  in step S 103 . A control unit  270  of the cable-use charge control device  200  receives the command through a terminal device communication unit  250 . 
     The control unit  270  of the cable-use charge control device  200  performs the received command in step S 105 . 
     In particular, if the command corresponding to the user input is the charge start of the EV  100 , the control unit  270  of the cable-use charge control device  200  turns on at least one of relays  220  turned off so that the EV charge cable assembly  20  may supply the AC power from a socket  30  to the EV  100 . 
     More particularly, if the command corresponding to the user input is the charge start of the EV  100 , the control unit  270  of the cable-use charge control device  200  provides at least one of information on the allowable current of the EV-side power cable assembly  50  and information on the allowable current of the grid-side power cable assembly  60  to a battery charging device  115  of the EV  100  through an EV-side data communication cable  55 . In addition, the control unit  270  of the cable-use charge control device  200  turns on at least one of relays  220  turned off. Then, the battery charging device  115  of the EV  100  may determine a charge current based on the provided information and then take the determined charge current through the EV charge cable assembly  20  to charge a battery  110 . 
     If the control unit  270  provides information on the allowable current of the EV-side power cable assembly  50 , the battery charging device  115  of the EV  100  may use a current smaller than or equal to the allowable current to charge the battery  110 . 
     If the control unit  270  provides information on the allowable current of the grid-side power cable assembly  60 , the battery charging device  115  of the EV  100  may use a current smaller than or equal to the allowable current to charge the battery  110 . 
     If the control unit  270  provides information on the allowable current of the EV-side power cable assembly  50  and information on the allowable current of the grid-side power cable assembly  60 , the battery charging device  115  of the EV  100  may use a current smaller than or equal to a smaller one of the two allowable currents to charge the battery  110 . 
     If the command corresponding to the user input is the charge stop of the EV  100 , the control unit  270  of the cable-use charge control device  200  turns off at least one of relays  220  turned on so that the EV charge cable assembly  20  may no longer charge the EV  100 . 
     If the command corresponding to the user input is the request for the EV charge related information, the control unit  270  of the cable-use charge control device  200  collects EV charge related information. 
     The control unit  270  of the cable-use charge control device  200  transmits a response corresponding to the received command to the terminal device  300  through the terminal device communication unit  250  in step S 107 . 
     If the command corresponding to the user input is the charge start of the EV  100 , the response may include information notifying that the state of at least one relay  220  is in a turn-on state. 
     If the command corresponding to the user input is the charge stop of the EV  100 , the response may include information notifying that the state of at least one relay  220  is in a turn-off state. 
     If the command corresponding to the user input is the request for the EV charge related information, the response may include collected EV charge related information. 
     The EV charge related information may include at least one of information on the EV  100  and information on the EV charge cable assembly  20 . 
     The information on the EV  100  may include at least one of an initial charge state, the current charge state, a charge start time, a predicted charge end time, an actual charge end time, EV charge status information, EV charge error information, information on an amount of power supplied to the EV  100 , and information on the size of a current applied to the EV  100 . The initial charge state and the current charge state may be represented by a ratio of the current charge amount to gross capacity. The EV charge status information may represent whether the EV  100  is being charged, waits for charge or has been completely charged. 
     The information on the EV charge cable assembly  20  may include at least one of information on the charge operation of the EV charge cable assembly  20 , information on the usage history of the EV charge cable assembly  20 , state information on the EV charge cable assembly  20 , information on the fault of the EV charge cable assembly  20 , information on the allowable current of the EV-side power cable assembly  50 , and information on the allowable current of the grid-side power cable assembly  60 . The information on the charge operation of the EV charge cable assembly  20  may represent whether the EV charge cable assembly  20  supplies power from the socket  30  to the EV  100 . The state information on the EV charge cable assembly  20  may include at least one of information on the state of at least one relay  220 , information on the presence or absence of the welding of at least one relay  220 , information on the temperature of the EV charge cable assembly  20 , information on the disconnection of the EV charge cable assembly  20 , information on the disconnection of the EV charge cable assembly  20 , and ambient environmental information on the EV charge cable assembly  20 . The information on the state of the at least one relay  220  may represent whether the at least one relay  220  has been turned on or off. The ambient environmental information on the EV charge cable assembly  20  may include at least one of information on ambient temperature and information on ambient humidity. 
     The control unit  330  of the terminal device  300  displays a received response on a display unit  340  in step S 109 . 
     If the command corresponding to the user input is the charge start of the EV  100 , a control unit  330  of a terminal device  300  may display, on the display unit  340  information notifying that the state of at least one relay  220  is in a turn-on state. 
     If the command corresponding to the user input is the charge stop of the EV  100 , the control unit  330  of the terminal device  300  may display, on the display unit  340  information notifying that the state of at least one relay  220  is in a turn-off state. 
     If the command corresponding to the user input is the request for the EV charge related information, the control unit  330  of the terminal device  300  may display EV charge related information on the display unit  340 . A user may input an additional user input for the control of the EV charge cable assembly  20  to the terminal device  300  through an input device  320  with reference to the displayed EV charge related information. 
     As such, information on the charge operation and state of the EV charge cable assembly  20  is displayed through the terminal device  300 . Thus, a user may more conveniently and easily recognize the information on the charge operation and state of the EV charge cable assembly  20 . Also, the user may more easily determine the presence or absence of a fault of the EV charge cable assembly  20  and a fault part through the information on the state of the EV charge cable assembly  20  to be capable of taking actions rapidly. For example, when the grounding cable between the EV charge cable assembly  20  and a commercial power supply is shorted, it was typically difficult to sense it. However, since in the present embodiment, a sensing unit  230  senses and displays the presence or absence of disconnection, the user may stop the charge operation of the EV charge cable assembly  20  and repair a disconnected part or request for a repair. In particular, when information on the fault and corresponding action of the EV charge cable assembly  20  is transmitted from the cable-use charge control device  200  to the terminal device  300 , the user may recognize the presence or absence of a fault and take an action more conveniently and easily. Thus, the user may previously recognize that the EV  100  is not charged due to the fault of the EV charge cable assembly  20 . Also, when e.g., the usage history of the EV charge cable assembly  20  is transmitted to the terminal device, the user may predict the life of the EV charge cable assembly and provide an extra EV charge cable assembly. Since the EV charge cable assembly  20  is used in a bad environment in many cases, it may cause frequent repair and replacement. However, when the EV charge cable assembly  20  has a cable-use charge control device  200  including a terminal device communication unit  250  which is relatively expensive, repair may be more difficult due to the characteristics of the cable-use charge control device  200  manufactured to have characteristics resistant to external temperature, external humidity, vibration, and shock, and it is cause an increase in cost-bearing when replacement is performed. 
     In order to solve such a limitation, it is possible to consider providing the terminal device communication unit of the cable use charge control device  200  as a separate device. Such an embodiment is described with reference to  FIGS. 7 to 10 . 
       FIG. 7  is a conceptual view of an EV charging system according to another embodiment. 
     Referring to  FIG. 7 , an EV charging system  10  according to an embodiment includes an EV  100 , an EV charge cable assembly  20 , a socket  30 , a terminal device  300 , and an add-on communication device  400 . 
     In particular, since a system in  FIG. 7  is obtained by adding the add-on communication device  400  to the system in  FIG. 1  and thus other parts excluding the add-on communication device  400  are the same, their detailed descriptions are omitted. 
     The cable-use charge control device  200  monitors the charge of the EV  100 , provides charge related information obtained from the monitoring, to the add-on communication device  400  and controls the charge of the EV  100 . 
     When the cable-use charge control device  200  includes a connector for wired communication, it may be vulnerable to external conditions because the connector includes a metal terminal. In order to solve such a limitation, the cable-use charge control device  200  may communicate with the add-on communication device  400  wirelessly. 
     The terminal device  300  performs contactless, wireless communication with the add-on communication device  400  and displays information on the EV charge cable assembly  20 . 
     The add-on communication device  400  is attached to the cable-use charge control device  200 . In this case, the add-on communication device  400  may also be mechanically coupled to the cable-use charge control device  200 . Also, the add-on communication device  400  may also be attached to the cable-use charge control device  200  by magnetism. 
       FIG. 8  is a block diagram of an EV charge cable assembly according to another embodiment. 
     When compared to the embodiment in  FIG. 3 , the cable-use charge control device  200  in  FIG. 8  further includes an add-on communication unit  210 . Also, the cable-use charge control device  200  in  FIG. 8  may not have a terminal device communication unit  250  in order to lower cost and repair cost but it is also possible to include the terminal device communication unit  250  in various applications. 
     The operations of at least one relay  220 , a sensing unit  230 , an EV communication unit  240 , a storage unit  260  and a control unit  270  are the same or similar as those in the embodiment in  FIG. 3  or are described below. 
     The add-on communication unit  210  performs communication with the add-on communication device  400 . The add-on communication unit  210  and the add-on communication device  400  may also use an Infrared Data Association (IrDA) communication technology, a Radio Frequency communication technology, Bluetooth, Ultra Wideband (UWB), ZigBee, Digital Living Network Alliance (DLNA), and so on to perform communication. 
     In particular, in order to lower the costs of the EV charge cable assembly  20  and the add-on communication device  400 , the add-on device communication unit  210  may use an IrDA communication technology. In this case, the add-on communication unit  210  may include an infrared light-emitting diode and an infrared light-receiving diode. 
       FIG. 9  is a block diagram of an add-on communication device according to an embodiment. 
     The add-on communication device  400  includes a charge control device communication unit  440 , a terminal device communication unit  450 , a storage unit  460 , and a control unit  470 . 
     The charge control device communication unit  440  performs communication with a cable-use charge control device  200 . In particular, the charge control device communication unit  440  communicates with the add-on device communication unit  210  of the cable-use charge control device  200 . The charge control device communication unit  440  and the add-on device communication unit  210  may also use an Infrared Data Association (IrDA) communication technology, a Radio Frequency communication technology, Bluetooth, Ultra Wideband (UWB), ZigBee, Digital Living Network Alliance (DLNA), and so on to perform communication. 
     In order to lower the costs of the EV charge cable assembly  20  and the add-on communication device  400 , the charge control device communication unit  440  may use an IrDA communication technology. In this case, the charge control device communication unit  440  may include an infrared light-emitting diode  441  and an infrared light-receiving diode  442 . 
     When the add-on communication device  400  is normally attached to the cable-use charge control device  200 , the positions of the infrared light-emitting diode  441  and the infrared-light receiving diode  442  of the charge control device communication unit  440  match the infrared light-receiving diode and the infrared light-emitting diode of the add-on device communication unit  210  of the cable-use charge control device  200 , respectively. 
     The terminal device communication unit  450  performs communication with a terminal device  300 . In particular, the terminal device communication unit  450  performs communication with a communication unit  310  in the terminal device  300 . In particular, the terminal device communication unit  450  and the communication unit  310  may also use an Infrared Data Association (IrDA) communication technology, a Radio Frequency communication technology, Bluetooth, Ultra Wideband (UWB), ZigBee, Digital Living Network Alliance (DLNA), and so on to perform communication. In particular, the terminal device communication unit  450  may use at least one of a wireless local area network (WLAN), such as WiFi defined in IEEE 802.11, and a wireless wide area network (WWAN) defined in IEEE 802.16 or long term evolution (LTE) standard to perform communication with the terminal device  300 . 
     The storage unit  460  stores pieces of information to be described below. In particular, the storage unit  460  may store EV charge related information. The storage unit  460  may store information on the usage history of the cable-use charge control device  210 . For example, the storage unit  460  may store information on the last usage time and time length and accumulated usage time length of the cable-use charge control device  200 . 
     The control unit  470  controls the overall operations of the add-on communication device  400 , including operations to be described below. 
     Since the add-on communication device  400  is not in direct contact electrically with the cable-use charge control device  200 , it has no need to separately receive power. However, when a user does not use the add-on communication device  400 , the user may not cut off the supply of power to the add-on communication device  400 . Since it unnecessarily increases power consumption, there is a need for a solution that may minimize power consumption when the add-on communication device  400  is not used. 
       FIG. 10  is a ladder diagram showing an operating method of an EV charging system  10  according to another embodiment. 
     A control unit  330  of a terminal device  300  obtains a user input for the setting of an add-on charging device  400  through an input device  320  in step S 301 . The user input for the setting of the add-on communication device  400  may include at least one of a charge limit and a charge mode. The charge limit may include at least one of a charge limit in a public area and a charge limit in a home area. The charge mode may include at least one of a charge mode in the public area and a charge mode in the home area. The charge amount may be an absolute value expressed in units of Wh or a relative value expressed in units of %. A set of values that the charge mode may represent may include a fast charge mode and a slow charge mode. 
     The control unit  330  of the terminal device  300  controls the communication unit  310  so that setting information corresponding to a user input obtained by the communication unit  310  is transmitted to the add-on communication device  400  through an EV-side data communication line  55  in step S 303 . In this case, the setting information may include at least one of setting information on the charge limit and setting information on the charge mode. The setting information on the charge limit may include at least one of setting information on the charge limit in the public area and setting information on the charge limit in the home area. The setting information on the charge mode may include at least one of setting information on the charge mode in the public area and setting information on the charge mode in the home area. Accordingly, the control unit  470  of the add-on communication device  400  receives setting information from the terminal device  300  through the terminal device communication unit  450 . 
     The add-on communication device  400  stores the received setting information in the storage unit  460  and sets the add-on communication device  400  based on the received setting information in step S 305 . 
     A control unit  330  of a terminal device  300  obtains a user input for commanding an EV charge cable assembly  20  through an input device  320  in step S 315 . In this case, the user input for the control of the EV charge cable assembly  20  may include one or more of the charge start of an EV  100 , the charge stop of the EV  100  and a request for EV charge related information. The user input may include at least one of a fast charge start and a slow charge start. 
     The control unit  330  of the terminal device  300  transmits a command corresponding to the obtained user input to the add-on communication device  400  through the communication unit  310  in step S 317 . The control unit  470  of the add-on communication device  400  may receive a command from the terminal device  300  through the terminal device communication unit  450 . In this case, a set of values that the command may represent may include the charge start of the EV  100 , the charge stop of the EV  100 , and a request for EV charge related information. A set of values that the charge start of the EV  100  may represent may include the fast charge start and slow charge start of the EV  100 . 
     The control unit  470  of the add-on communication device  400  generates a control command for the control of the cable-use charge control device  200  in step S 318 . The control unit  470  of the add-on communication device  400  may generate a control command based on at least one of a command received from the terminal device  300 , the current position, setting information, the charge stage of the EV  100  being a result of monitoring to be described below. In this case, a set of values that the control command may represent may include a charge start, a chart stop, and a request for EV charge related information. A set of values that the charge start may represent may include a fast charge start and a slow charge start. 
     In an embodiment, when the command received from the terminal device  300  is the charge start, the control unit  470  of the add-on communication device  400  may generate a control command representing the charge start. 
     In an embodiment, when the command received from the terminal device  300  is the fast charge start, the control unit  470  of the add-on communication device  400  may generate a control command representing the fast charge start. 
     In an embodiment, when the command received from the terminal device  300  is the slow charge start, the control unit  470  of the add-on communication device  400  may generate a control command representing the slow charge start. 
     In an embodiment, when the command received from the terminal device  300  is the charge start and the set charge mode is the fast charge mode, the control unit  470  of the add-on communication device  400  may generate a control command representing the fast charge start. 
     In an embodiment, when the command received from the terminal device  300  is the charge start and the set charge mode is the slow charge mode, the control unit  470  of the add-on communication device  400  may generate a control command representing the slow charge start. 
     In an embodiment, when the command received from the terminal device  300  is the charge stop, the control unit  470  of the add-on communication device  400  may generate a control command representing the charge stop. 
     In an embodiment, when the command received from the terminal device  300  is the request for the EV charge related information, the control unit  470  of the add-on communication device  400  may generate a control command representing the request for the EV charge related information. 
     In an embodiment, when the command received from the terminal device  300  is the charge start and the current position is the home area, the control unit  470  of the add-on communication device  400  may generate a control command representing the charge start according to the set charge mode in the home area. In particular, when the set charge mode in the home area is the fast charge mode, the control unit  470  of the add-on communication device  400  may generate a control command representing the fast charge start. When the set charge mode in the home area is the slow charge mode, the control unit  470  of the add-on communication device  400  may generate a control command representing the slow charge start. 
     In an embodiment, when the command received from the terminal device  300  is the charge start and the current position is the public area, the control unit  470  of the add-on communication device  400  may generate a control command representing the charge start according to the set charge mode in the public area. In particular, when the set charge mode in the public area is the fast charge mode, the control unit  470  of the add-on communication device  400  may generate a control command representing the fast charge start. When the set charge mode in the public area is the slow charge mode, the control unit  470  of the add-on communication device  400  may generate a control command representing the slow charge start. 
     In an embodiment, when the command received from the terminal device  300  is the charge start and the current position is the home area, the control unit  470  of the add-on communication device  400  may generate a control command representing the slow charge start. 
     In an embodiment, when the command received from the terminal device  300  is the charge start and the current position is the public area, the control unit  470  of the add-on communication device  400  may generate a control command representing the fast charge start. 
     In an embodiment, when the command received from the terminal device  300  is the charge start and as a result of monitoring, the amount of power supplied to the EV  100  reaches the set charge limit, the control unit  470  of the add-on communication device  400  may generate a control command representing the charge stop. 
     In an embodiment, when the command received from the terminal device  300  is the charge start, the current position is the home area, and as a result of monitoring, the amount of power supplied to the EV  100  reaches the set charge limit in the home area, the control unit  470  of the add-on communication device  400  may generate a control command representing the charge stop. 
     In an embodiment, when the command received from the terminal device  300  is the charge start, the current position is the public area, and as a result of monitoring, the amount of power supplied to the EV  100  reaches the set charge limit in the public area, the control unit  470  of the add-on communication device  400  may generate a control command representing the charge stop. 
     To this end, the control unit  470  of the add-on communication device  400  may obtain the current position of the EV  100 . The control unit  470  of the add-on communication device  400  may use one or more of global positioning system GPS information, base station information on a WLAN, base station information on a WWAN to obtain the current position of the EV  100 . 
     A set of values that the current location may represent may be the home area and the public area. 
     The control unit  470  of the add-on communication device  400  transmits a generated control command to the cable-use charge control device  200  through the charge control device communication unit  440  in step S 319 . An infrared light-emitting diode  441  of the charge control device communication unit  440  may radiate an infrared ray having a digital pattern corresponding to the generated control command. 
     The control unit  270  of the cable-use charge control device  200  performs the received command in step S 321 . 
     In particular, if the command corresponding to the user input is the charge start of the EV  100 , the control unit  270  of the cable-use charge control device  200  turns on at least one of relays  220  turned off so that the EV charge cable assembly  20  may supply AC power from a socket  30  to the EV  100 . 
     If the command corresponding to the user input is the fast charge start of the EV  100 , the control unit  270  of the cable-use charge control device  200  turns on at least one of relays  220  turned off so that the EV charge cable assembly  20  may fast supply AC power from the socket  30  to the EV  100 . 
     If the command corresponding to the user input is the slow charge start of the EV  100 , the control unit  270  of the cable-use charge control device  200  turns on at least one of relays  220  turned off so that the EV charge cable assembly  20  may slowly supply AC power from the socket  30  to the EV  100 . 
     If the command corresponding to the user input is the charge stop of the EV  100 , the control unit  270  of the cable-use charge control device  200  turns off at least one of relays  220  turned on so that the EV charge cable assembly  20  may no longer charge the EV  100 . 
     If the command corresponding to the user input is the request for the EV charge related information, the control unit  270  of the cable-use charge control device  200  collects EV charge related information. 
     The control unit  270  of the cable-use charge control device  200  transmits a response corresponding to the received command to the add-on communication device  400  through the add-on communication unit  250  in step S 323 . The infrared light-emitting diode of the add-on communication unit  210  of the cable-use charge control device  200  may irradiate an infrared ray having a digital pattern corresponding to a response corresponding to the received command. The control unit  470  of the add-on communication device  400  may receive a response from the cable-use charge control device  200  through the charge control device communication unit  440 . 
     If the command corresponding to the user input is the charge start of the EV  100 , the response may include information notifying that the state of at least one relay  220  is in a turn-on state. 
     If the command corresponding to the user input is the fast charge start of the EV  100 , the response may include information notifying that the state of at least one relay  220  is in a turn-on state for fast charge. If the command corresponding to the user input is the slow charge start of the EV  100 , the response may include information notifying that the state of at least one relay  220  is in a turn-on state for slow charge. 
     If the command corresponding to the user input is the charge stop of the EV  100 , the response may include information notifying that the state of at least one relay  220  is in a turn-off state. 
     If the command corresponding to the user input is the request for the EV charge related information, the response may include collected EV charge related information. As described earlier, the EV charge related information may include at least one of information on the EV  100  and information on the EV charge cable assembly  20 . 
     The control unit  470  of the add-on communication device  400  transmits a received response to the terminal device  300  through the terminal device communication unit  450  in step S 325 . 
     The control unit  330  of the terminal device  300  displays a received response on a display unit  340  in step S 327 . Since the operation described in step S 109  may be applied to the operation in step S 327 , detailed descriptions for the operation in step S 327  are omitted. 
     The control unit  470  of the add-on communication device  400  checks whether a generated control command has been completed in step S 331 . 
     When the generated control command is a charge start, a charge limit has been set, and charge is not yet completed, the control unit  470  of the add-on communication device  400  may determine that the generated control command has not been completed. 
     When the generated control command is a charge stop or a request for EV charge related information or the control command is the charge start while the charge limit has not been set, the control unit  470  of the add-on communication device  400  may determine that the generated control command has been completed. 
     When the received control command has been completed, the control unit  470  of the add-on communication device  400  may wait for the reception of new setting information or a new command. 
     When the generated control command has not been completed, the control unit  470  of the add-on communication device  400  monitors the charge state of the EV  100  in step S 333 . In particular, the control unit  470  of the add-on communication device  400  may monitor the amount of power supplied to the EV  100 . 
     The control unit  470  of the add-on communication device  400  checks based on at least one of the charge state the EV  100  and setting information thereon whether the cable-use charge control device  200  needs an additional control command in step S 335 . In particular, the control unit  470  of the add-on communication device  400  may compare the amount of power supplied to the EV  100  with a set charge limit to check whether the cable-use charge control device  200  needs an additional control command. If the amount of power supplied to the EV  100  reaches the set charge limit, the control unit  470  of the add-on communication device  400  may determine that the cable-use charge control device  200  needs an additional control command. If the amount of power supplied to the EV  100  does not reach the set charge limit, the control unit  470  of the add-on communication device  400  may determine that the cable-use charge control device  200  does not need an additional control command. 
     When the additional control command is not needed, the control unit  470  of the add-on communication device  400  may continue to monitor the charge state of the EV  100 . 
     When the additional control command is needed, the control unit  470  of the add-on communication device  400  generates the additional control command in step S 318 . Since the generation of the control command has been described earlier, its description is omitted in this section. 
       FIG. 11  is a ladder diagram showing an operating method of an EV charging system  10  according to another embodiment. 
     A terminal device  300  transmits a charge command to a cable-use charge control device  200  in step S 501 . 
     When the cable-use charge control device  200  receives the charge command, a control unit  270  of the cable-use charge control device  200  measures the allowable current of an EV charge cable assembly  20  through an allowable current sensing unit  239  in step S 503 . 
     In this case, the allowable current of the EV charge cable assembly  20  may also be the allowable current of an EV-side power cable assembly  50  or the allowable current of a grid-side power cable assembly  60 . Also, the allowable current of the EV charge cable assembly  20  may also be an allowable current satisfying both the allowable current of the EV-side power cable assembly  50  and the allowable current of the grid-side power cable assembly  60 . More particularly, the allowable current of the EV charge cable assembly  20  may also be a smaller one of the allowable current of the EV-side power cable assembly  50  and the allowable current of the grid-side power cable assembly  60 . 
     In an embodiment, when the EV-side power cable assembly  50  is integrally attached to the cable-use charge control device  200  not to be separated therefrom and is manufactured so that the allowable current of the EV-side power cable assembly  50  is relatively high, the cable-use charge control device  200  may measure the allowable current of the grid-side power cable assembly  60  without measuring the allowable current of the EV-side power cable assembly  50 . 
     The cable-use charge control device  200  transmits information on the measured allowable current to the EV  100  in step S 505 . 
     In this case, the cable-use charge control device  200  may transmit at least one of information on the allowable current of the EV-side power cable assembly  50 , information on the allowable current of the grid-side power cable assembly  60 , and information on an allowable current satisfying the two allowable currents. 
     The cable-use charge control device  200  transmits information on the measured allowable current to a terminal device  300  in step S 505 . 
     In this case, the cable-use charge control device  200  may transmit at least one of information on the allowable current of the EV-side power cable assembly  50 , information on the allowable current of the grid-side power cable assembly  60 , and information on an allowable current satisfying the two allowable currents. 
     The EV  100  and the cable-use charge control device  200  starts charging a battery  110  of the EV  100  in step S 509 . In this case, the control unit  270  of the cable-use charge control device  200  may turn on a relay  220  turned off so that the EV charge cable assembly  20  may provide AC power from a socket  30  to the EV  100 . 
     A battery charging device  115  of the EV  100  may determine a charge current based on the provided information and then take the determined charge current through the EV charge cable assembly  20  to charge the battery  110 . That is, the battery charging device  115  of the EV  100  may use a charge current satisfying the allowable current of the EV charge cable assembly  20  to charge the battery  110 . 
     The cable-use charge control device  200  notifies the terminal device  300  of a charge start in step S 511 . 
     The control unit  270  of the cable-use charge control device  200  measures the charge current through a current sensing unit  232  in step S 513 . 
     The control unit  270  of the cable-use charge control device  200  senses whether the charge current exceeds the allowable current, in step S 513 . 
     If the charge current does not exceed the allowable current, the control unit  270  of the cable-use charge control device  200  checks whether charge has been completed, in step S 517 . 
     If the charge has been completed, the EV  100  and the cable-use charge control device  200  continue to charge the battery  110  of the EV  100 . 
     If the charge has been completed, the cable-use charge control device  200  notifies the terminal device of a charge stop in step S 519  and stops charging the battery  110  in step S 521 . In this case, the control unit  270  of the cable-use charge control device  200  turns off a relay  220  turned on. 
     On the other hand, if the charge current exceeds the allowable current, the cable-use charge control device  200  transmits, in step S 523 , to the terminal device  300  an abnormal charge stop notification message notifying that the charge current has exceeded the allowable current and stops charging the battery  110  in step S 521 . In this case, the control unit  270  of the cable-use charge control device  200  turns off the relay  220  turned on. 
     In  FIG. 11 , information exchange between the cable-use charge control device  200  and the terminal device may also be performed without or with the add-on communication device  400 . 
     The communication between the EV  100  and the cable-use charge control device  200 , the communication between the cable-use charge control device  200  and the add-on communication device  400 , the communication between the cable-use charge control device  200  and the terminal device  300  and the communication between the add-on communication device  400  and the terminal device  300  may conform on the above-described technology. 
     In  FIG. 11 , when the terminal device  300  receives information, the terminal device  300  may also display corresponding information. As an example, when the terminal device  300  receives the abnormal charge stop notification message notifying that the charge current has exceeded the allowable current, the terminal device  300  may display the fact that the charge current has exceeded the allowable current. 
     In the following, a typical welding sensing method by an EV charge cable assembly  20  is described with reference to  FIGS. 12 to 13 . 
       FIGS. 12 and 13  are block diagrams of a typical welding sensing unit in the EV charge cable assembly  20 . 
     Referring to  FIG. 12 , a main relay and the welding sensing unit have typically crossed each other and thus have been directly connected each other. In particular, a main path  1   210   a  connected to the rear end of a main relay  1   220   a  and a main path  2   210   b  connected to the front end of a main relay  2   220   b  are connected to a welding sensing unit  1   231   a . Also, the main path  1   210   a  connected to the front end of the main relay  1   220   a  and the main path  2   210   b  connected to the rear end of the main relay  2   220   b  are connected to a welding sensing unit  2   231   b.    
     A limitation in the typical welding sensing method is particularly discussed with reference to  FIG. 13 . 
     Typically, a relay welding sensing unit  231  always maintains a state in which it is connected to each main relay  220 . Thus, as shown in  FIG. 13 , power is consumed in a state in which main relays  220  are all closed, i.e., in which charge is being performed. However, since the relays need to be closed during charge, there is no need to determine the presence or absence of the welding of the main relay in this state. As a result, it may be seen that the relay welding sensing unit  231  unnecessarily consumes power. It is a limitation resulting from the fact that there is no relay to control the relay welding sensing unit according to the open and close of the main relay  220 . 
     Also, as shown in  FIG. 13 , if the relay welding sensing unit  231  is directly connected to the main path  210 , there is a possibility that a device is damaged because high current flowing in the main path  210  is directly received. In particular, since the relay welding sensing unit  231  is directly connected to the main path  210 , there is a risk that a voltage exceeding the withstanding voltage of the relay welding sensing unit  231  is applied to a device during charge. 
     In this case, the withstanding voltage indicates the limit of an applied voltage capable of withstanding without destruction or the size limit of the applied voltage capable of being used without destruction of the insulation part of a machine or component when an AC voltage defined for an insulation material to be tested is applied for one minute. An evaluation method is determined by a test method or condition according to a defined applied voltage obtained by multiplying potential gradient (indicated in kV/mm) defined in a quality standard by the thickness (mm) of a test piece, a molding material, a laminated bar, and a laminated plate. 
     Thus, since there may typically be the above-described limitation. the present disclosure solving it is described below. 
       FIG. 14  is a block diagram of a welding sensing device in an EV charge cable assembly  20  according to the present disclosure. 
     The EV charge cable assembly  20  may include a main path  210 , a main relay  220 , a relay welding sensing unit  231 , a control unit  270 , and a welding monitoring relay  280 . 
     The main path  210  is a path through which a charge current moves from a plug to an EV. Since the charge current of the EV is mostly high current, the main path  210  may be designed so that it is possible to transmit the high current. The main path  210  includes two main paths  210   a  and  210   b  because it uses an AC current. 
     The main relay  220  is a kind of a switch coupled to the intermediate portion of the main path  210 . When the main relay  220  opens or closes, it is possible to control the charge of the EV  100 . In particular, if the main relay  220  opens, the main path  210  is in a disconnected state and thus the charge of the EV is not performed. Likewise, if the main relay  220  closes, the main path  210  is in a connected state and thus the plug  30  is connected to the EV  100  so that the charge is performed. 
     The main relays  220  may be coupled to the main paths  210 , respectively. The main relay  220  may be one of an electrical switch and a physical switch. 
     The relay welding sensing unit  231  senses the presence or absence of the welding of the main relay  220 . It crosses the main path  210  connected to the front and rear ends of the main relay to be connected thereto to sense the presence or absence of the welding of the main relay  220 . 
     In particular, when the charge is ended, the main relay  220  opens. However, welding indicating that the main relay does not open but still has a close state may occur due to magnetic field by high current or high temperature. In this case, since current continues to be supplied to the EV  100  despite the completion of the charge, there may be a problem due to over-charge. 
     In an embodiment, it is assumed that the main relay  1   220   a  has been welded. If the main relay  1   220   a  has been welded, the main relay  1   220   a  has a close state and the main relay  2   220   b  has an open state. In this case, the main path  2  is disconnected and thus current does not flow therethrough, but the main path  1  still has a connected state and thus current continues to flow therethrough. 
     Thus, in a normal state, the main relay  1   220   a  opens and thus current flows only through the relay welding sensing unit  231   a  and not through the main path  1   210   a , but when the main relay  1   220   a  closes due to welding, the current mostly flows through the main path  1   210   a  having low resistance. Based on the above-described normal operation and other operations, the relay welding sensing unit  231  senses the welding of the main relay  220 . 
     The relay welding sensing unit  231  may include a photo coupler in an embodiment. The photo coupler indicates an electrical element which has both light emission and reception units electrically insulated and in which a signal is transmitted by light. In principle, when a signal is input to a light-emitting diode in the photo coupler, light is emitted and, when the light enters a photo transistor receiving the light, there is a conductive state. The photo coupler has one direction. The photo coupler may include the light emission unit that emits light when current flows, and the light reception unit that receives the light from the light emission unit and changes the received light to an electrical signal. 
     Thus, when the main relay  220  opens, current flows to the photo coupler and the light emission unit emits light, and on the contrary, when the main relay  220  closes, the current mostly flows to the main path and not to the photo coupler and thus does not flow to the photo coupler, so the light emission unit does not emit light. The light reception unit in the photo coupler receives a change in the light emission unit as a signal and transmits the signal to the control unit  270 . In particular, the light reception unit receives light from the light emission unit, changes the light received from the light emission unit to an electrical signal and transmits the electrical signal to the control unit  270 . 
     The welding monitoring relay  280  is connected to the relay welding sensing unit  1  and relay welding sensing unit  2   231   a  and  231   b . In particular, the welding monitoring relay  280  is connected to the front end of each main relay  220 , and the welding monitoring relay  280  is connected to the relay welding sensing unit  231  connected to the rear end of each main relay  220 . The welding monitoring relay  280  may include a separate relay for each relay welding sensing unit. 
     The welding monitoring relay  280  controls a relay by the control of the control unit  270 . Also, the welding monitoring relay  280  may supplement an insufficient withstanding voltage of the relay welding sensing unit  231 . 
     The control unit  270  controls the overall operations related to welding sensing. In particular, it is possible to control the open and close of the welding monitoring relay  280  based on determination on whether to charge. Also, it is possible to receive a report on the presence or absence of welding from the relay welding sensing unit  231  to perform further control. Moreover, the control unit  270  may control the open or close of a main relay based on a signal related to charge. 
     In the following, the welding sensing process of the EV charge cable assembly  20  is described in detail with reference to  FIG. 15 . 
       FIG. 15  is a flowchart of a process of sensing the presence or absence of welding through a welding monitoring relay  280  in an EV charge cable assembly  20 . 
     A control unit  270  determines whether to charge an EV  100  through the EV charge cable assembly  20  in step S 601 . Since algorithms related to a charge start and a charge end have been already described in  FIG. 11 , their detailed descriptions are omitted. 
     If it is determined that the EV  100  is being currently charged, the control unit  270  continues to perform charge in step S 603 . The charge process has been already described in  FIG. 11  as well. 
     The control unit  270  commands the open of the welding monitoring relay  280  while the charge is being performed. In an embodiment, when the control unit  270  receives a signal related to the charge start, it is possible to transmit a signal opening a relay to the welding monitoring relay  280 . A charge start state indicates a state in which a main relay  220  closes for the charge of the EV  100 , in which case there is no need to sense the presence or absence of welding. In particular, if the main relay  200  closes for charge, there is no need to sense the presence or absence of welding because the relay has not abnormally closed. 
     By the command of the control unit  270 , the welding monitoring relay  280  opens in step S 607 . In an embodiment, the welding monitoring relay  280  may include a separate relay for each relay welding sensing unit  231 . The control unit  270  opens all relays of the welding monitoring relay  280 . 
     With the open of the welding monitoring relay  280 , the operation of the relay welding sensing unit  231  stops in step S 609 . In particular, since power supply is cut off with the disconnection of a path connected to the relay welding sensing unit  231 , the operation of the relay welding sensing unit  231  stops. As a result, it is possible to minimize unnecessary power consumption for the relay welding sensing unit  231 . Also, it is possible to extend the life of a related device by minimizing a time for which the relay welding sensing unit  231  is exposed to high current for the charge of an EV. 
     On the contrary, a case where the EV  100  is not being charged is described below. 
     The control unit  270  receives a charge completion signal in step S 611 . Since a charge completion algorithm has also been described in  FIG. 11 , its description is omitted in this section. 
     The control unit  270  receives the charge completion signal, opens the main relay  220  and closes the welding monitoring relay  280  in step S 613 . When the main relay  220  opens, the main path  210  is disconnected and thus power supply to the EV  100  is cut off. If the main relay still closes despite charge completion, the battery pack of the EV is over-charged and thus it is possible to decrease the efficiency of the battery pack and cause a fault due to overheating. 
     The control unit  270  opens the main relay  220  and simultaneously closes the welding monitoring relay  280 . In an embodiment, it is possible to first open the main relay  220  and then the welding monitoring relay  280 . The reason is that there is a need to determine the presence or absence of the welding of the main relay  220 , when charge has been completed and thus the main relay  220  needs to open. In particular, there may be a case where the main relay  220  needs to open but continues to maintain a close state. 
     When the control unit  270  closes the welding monitoring relay  280 , power is supplied to a relay welding sensing unit  231  connected to the welding monitoring relay  280 . Thus, the welding monitoring sensing unit  231  may sense the presence or absence of the welding of the main relay  220 . 
     The relay welding sensing unit  231  senses the presence or absence of the welding of the main relay  220  in step S 615 . Although the control unit  270  has commanded the main relay to open due to charge completion, the main relay  220  may still close, not open. This situation may occur because a portion of a relay melts by heat generated by high current passing through the relay and thus relays adhere to each other. Also, magnetic field is generated by the pass of the high current, so welding may occur by the attractive force of electromagnetic field. 
     In particular, when the main relay  220  has to open due to charge completion but closes, a current may mostly flow to the main relay  220  having a relatively smaller resistance than the relay welding sensing unit. In this case, less current may flow than the amount of current that should flow when the main relay  220  normally opens. The relay welding sensing unit  231  senses a change in the amount of current as described above and senses the presence or absence of welding. 
     In an embodiment, the relay welding sensing unit  231  may sense the presence or absence of welding through a photo coupler. The photo coupler may include a light emission unit receiving an electrical signal and emitting light, and a light reception unit generating an optical signal from the light emission unit and transmitting the generated optical signal. Thus, it is possible to convert current passing through the relay welding sensing unit  231  into an optical signal and transmit a corresponding optical signal to the control unit  270  through the light reception unit. 
     The control unit  270  determines the presence or absence of the welding of the main relay  220  based on the signal received from the relay welding sensing unit  231 . The presence or absence of the welding may be determined according to a change in signal transmitted from the relay welding sensing unit  231 . For example, if the intensity of a signal transmitted from the relay welding sensing unit when the main relay  220  normally opens is  10  but the intensity of a signal actually transmitted is  5 , it is possible to determine that the wedding of the main relay  220  has occurred. 
     When it is determined that the main relay  220  has welding, the control unit  270  transmits a command corresponding to the welding to each component in step S 619 . For example, it is possible to transmit a command opening the main relay  220  through other processes. As another example, there may be a method of urgently disconnecting a circuit in a charging apparatus. If welding occurs, an appropriate action is needed because current continues to be supplied to the EV and thus it is possible to break the EV. 
     The present disclosure differently operates the welding sensing unit determining the presence or absence of welding in the EV charge cable assembly when charge is and not performed, thereby blocking power from becoming unnecessarily consumed. 
     Also, the present disclosure supplements a withstanding voltage insufficient only with the welding sensing unit in the charge cable using high current, thereby further ensuring electrical stability. 
     According to an embodiment, the above-described method may also be embodied as processor readable codes on a program-recorded medium. Examples of the processor readable medium are a ROM, a RAM, a CD-ROM, a magnetic tape, a floppy disk, and an optical data storage device, and the method is also implemented in the form of a carrier wave (such as data transmission through the Internet). 
     The above-described charger is not limited to the configuration and method of described embodiments, and some or all of the embodiments may also be selectively combined so that various variations may be implemented. 
     Although embodiments have been described with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure. More particularly, various variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the disclosure, the drawings and the appended claims. In addition to variations and modifications in the component parts and/or arrangements, alternative uses will also be apparent to those skilled in the art.