Abstract:
In relay weld diagnostic device, a threshold value determination unit ( 104 ) determines a threshold value on the basis of a resistance value that is set for each of a P-pole-side resistor ( 24 ) and an N-pole-side resistor ( 23 ) provided to charging equipment. A peak value measuring unit ( 110 ) measures the peak value of a voltage supplied to a voltage line by an alternating-current signal output circuit ( 112 ). A comparison diagnosis unit ( 111 ) assesses the state of a relay ( 14 ) on the P-pole side and a relay ( 15 ) on the N-pole side by comparing the peak value and the threshold value, and makes a diagnosis as to whether the relays ( 14 ), ( 15 ) are welded on the basis of the assessed state of the relays ( 14 ), ( 15 ) and the state in which the relays ( 14 ), ( 15 ) are controlled.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a relay welding diagnostic apparatus for a relay used in a charging circuit for charging a battery of an electric automobile or the like. 
       BACKGROUND ART 
       [0002]    Conventionally, in a charging circuit of electric automobiles such as EVs (Electric Vehicles) and PHEVs (Plug-in Hybrid Electric Vehicles) that can travel by using an electric energy accumulated in a battery as a driving source, a relay circuit for connecting or disconnecting a boost charging facility and a battery connection junction circuit at the time of charging is provided. Such a relay circuit includes a mechanical relay junction (hereinafter referred to as “relay”), and welding of the relay may be caused by the on/off performed with a high voltage and high current. 
         [0003]    PTL 1, for example, discloses a technique for detecting welding of the relay. In the technique disclosed in PTL 1, the voltage across a positive electrode line and a negative electrode line is measured with a voltage detection circuit, and whether relays are welded is determined on the basis of results of the measurement. 
       CITATION LIST 
     Patent Literature 
     PTL 1 
     Japanese Patent Application Laid-Open No. 2011-015567 
     SUMMARY OF INVENTION 
     Technical Problem 
       [0004]    However, in the technique disclosed in PTL 1, whether relays are welded cannot be determined when the voltage detection circuit is broken. 
         [0005]    An object of the present invention is to provide a relay welding diagnostic apparatus that can determine whether relays are welded without using a voltage detection circuit. 
       Solution to Problem 
       [0006]    A relay welding diagnostic apparatus of an embodiment of the present invention is configured to determine whether relays are welded, the relays being respectively provided on a P electrode side and an N electrode side of a voltage line connecting a charging facility and a battery together, the relay welding diagnostic apparatus including: a threshold value determination section that determines a threshold value on the basis of resistance values set to a resistor on a P electrode side and a resistor on an N electrode side, the resistors being provided in the charging facility; a signal output circuit that supplies a predetermined voltage to the voltage line; a peak value measurement section that measures a peak value of the voltage supplied to the voltage line from the signal output circuit; and a comparison diagnosis section that determines a state of the relay by comparing the peak value with the threshold value, and determines whether the relay is welded on the basis of the state of the relay thus determined and a state set to the relay. 
       Advantageous Effects of Invention 
       [0007]    According to the present invention, whether relays are welded can be determined without using a voltage detection circuit. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0008]      FIG. 1  illustrates a configuration of a power system of an electric automobile and a boost charging facility according to an embodiment of the present invention; 
           [0009]      FIG. 2  is a block diagram illustrating a configuration of a relay welding diagnostic apparatus according to the embodiment of the present invention; 
           [0010]      FIG. 3  is a flowchart illustrating an exemplary entire operation performed by the relay welding diagnostic apparatus according to the embodiment of the present invention; 
           [0011]      FIG. 4  is a flowchart illustrating an exemplary operation of the relay welding diagnosis performed by the relay welding diagnostic apparatus according to the embodiment of the present invention; 
           [0012]      FIG. 5  is a flowchart illustrating an exemplary operation of a determination process performed by the relay welding diagnostic apparatus according to the embodiment of the present invention; and 
           [0013]      FIGS. 6A to 6C  illustrate an exemplary relationship between a peak value and a threshold value in a determination process according to the embodiment of the present invention. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0014]    Now, an embodiment of the present invention will be described with reference to the accompanying drawings. 
         [0015]    First, an overall configuration of an electric automobile and a boost charging facility according to an embodiment of the present invention is described with reference to  FIG. 1 .  FIG. 1  illustrates an exemplary configuration of a power system of the electric automobile and the boost charging facility according to the present embodiment. 
         [0016]    Vehicle  1  is an electric automobile. Vehicle  1  includes control apparatus  10 , leakage detection circuit  11 , notification apparatus  12 , battery  13 , relay  14 , relay  15 , voltage detection circuit  16 , capacitor  17 , communication line  18 , and signal line  19 . 
         [0017]    Boost charging facility  2  is a facility (including a device or a system) for charging vehicle  1 . Boost charging facility  2  includes AC/DC converting apparatus  20 , facility controlling apparatus  21 , ammeter  22 , resistor  23 , and resistor  24 . 
         [0018]    At the time of charging battery  13 , vehicle  1  and boost charging facility  2  are connected through a connector. In the example illustrated in  FIG. 1 , vehicle  1  and boost charging facility  2  are connected through five connectors  3   a,    3   b,    3   c,    3   d  and  3   e.    
         [0019]    Connector  3   a  connects a high pressure line (positive electrode line) on the positive side between vehicle  1  and boost charging facility  2 . Thus, AC/DC converting apparatus  20  and resistor  24  are connected to relay  14 . That is, resistor  24  is a resistor on the P electrode side, and relay  14  is a relay on the P electrode side. 
         [0020]    Connector  3   b  connects a high pressure line (negative electrode line) on the negative side between vehicle  1  and boost charging facility  2 . Thus, AC/DC converting apparatus  20  and resistor  23  are connected to relay  15 . That is, resistor  23  is a resistor on the N electrode side, and relay  15  is a relay on the N electrode side. 
         [0021]    Connector  3   c  connects communication line  18  between vehicle  1  and boost charging facility  2 . Thus, facility controlling apparatus  21  and control apparatus  10  are connected together. 
         [0022]    Connector  3   d  connects signal line  19  between vehicle  1  and boost charging facility  2 . Thus, the ground of boost charging facility  2  and control apparatus  10  are connected together. 
         [0023]    Connector  3   e  connects the ground of boost charging facility  2  and the vehicle body of vehicle  1  between vehicle  1  and boost charging facility  2 . 
         [0024]    It is to be noted that, the above-mentioned five connectors  3   a,    3   b,    3   c,    3   d  and  3   e  are collectively connected. 
         [0025]    When the connectors are connected in the above-mentioned manner, control apparatus  10  receives a signal generated in response to the connection of connector  3   d  through signal line  19 , thereby detecting a connection with boost charging facility  2 . It is to be noted that control apparatus  10  is, for example, an ECU (Electronic Control Unit). 
         [0026]    In addition, control apparatus  10  sends a relay control signal to relay  14  and relay  15 , to turn on or off (close or open) relay  14  and relay  15 . When relay  14  and relay  15  are turned on, AC/DC converting apparatus  20  and battery  13  are connected together through the positive electrode line and the negative electrode line. In the example illustrated in  FIG. 1 , relay  14  and relay  15  are both in the off state. 
         [0027]    In addition, when starting the charging of battery  13 , control apparatus  10  sends a charging start control signal for starting the charging to facility controlling apparatus  21  through communication line  18 . When receiving this signal, facility controlling apparatus  21  requests AC/DC converting apparatus  20  to start power supply. Thus, power is supplied from AC/DC converting apparatus  20  to battery  13 , and charging of battery  13  is started. 
         [0028]    When charging of battery  13  is started, facility controlling apparatus  21  performs a leakage detection on boost charging facility  2  side on the basis of current values measured by ammeter  22 . The current values measured by ammeter  22  are values of current flowing through resistor  23  and resistor  24  that are used to the leakage detection. 
         [0029]    It is to be noted that the technique disclosed in Japanese Patent Application Laid-Open No. 2010-239827, for example, may be adopted as the leakage detection on boost charging facility  2  side in this example. 
         [0030]    Likewise, when charging of battery  13  is started, leakage detection circuit  11  performs a leakage detection on vehicle  1  side on the basis of a voltage at junction P between capacitor  17  and resistor  113 . It is to be noted that the technique disclosed in Japanese Patent Application Laid-Open No. 08-70503, for example, may be adopted as the leakage detection of vehicle  1  side in this example. In addition, leakage detection circuit  11  includes peak value measurement section  110 , comparison diagnosis section  111 , and AC signal output circuit  112 , and details of these components will be described later with reference to  FIG. 2 . 
         [0031]    In the present embodiment, leakage detection circuit  11  allows for a relay diagnosis mode in which welding of relays  14  and  15  is determined, in addition to the leakage detection mode in which the leakage detection on vehicle  1  side is performed. Details of the relay diagnosis mode will be described later. 
         [0032]    When leakage in vehicle  1  is detected, leakage detection circuit  11  notifies control apparatus  10  of the fact that leakage is detected. In response to the notification, control apparatus  10  controls notification apparatus  12  to notify the user of the fact that leakage is detected in vehicle  1 . Examples of notification apparatus  12  include, for example, a display and a speaker. 
         [0033]    Voltage detection circuit  16  measures a voltage across the positive electrode line and the negative electrode line, and sends a voltage value thus obtained to control apparatus  10 . On the basis of a voltage value notified from voltage detection circuit  16 , control apparatus  10  performs a normal relay welding diagnosis. The technique disclosed in PTL 1 may be adopted as the normal relay welding diagnosis is, for example. 
         [0034]    In addition, in the present embodiment, control apparatus  10  performs a voltage detection circuit diagnosis on the basis of voltage value measured by voltage detection circuit  16 . This will be described later. 
         [0035]    Next, a configuration of a relay welding diagnostic apparatus according to the present embodiment will be described with reference to  FIG. 2 .  FIG. 2  is a block diagram illustrating an exemplary configuration of the relay welding diagnostic apparatus of the present embodiment. 
         [0036]    The relay welding diagnostic apparatus of the present embodiment includes control apparatus  10  and leakage detection circuit  11 . 
         [0037]    Control apparatus  10  includes connection detection section  100 , communication control section  101 , circuit diagnosis section  102 , relay control section  103 , and threshold value determination section  104 . 
         [0038]    Connection detection section  100  detects a connection between vehicle  1  and boost charging facility  2 . 
         [0039]    In the present embodiment, when a signal generated in response to the connection of connector  3   d  is received from signal line  19 , detection section  100  detects a connection between vehicle  1  and boost charging facility  2  as described above. Then, connection detection section  100  notifies communication control section  101  of the fact that a connection between vehicle  1  and boost charging facility  2  is detected. 
         [0040]    Communication control section  101  transmits and receives information and signals to and from facility controlling apparatus  21  of boost charging facility  2 , through communication line  18 . 
         [0041]    For example, when receiving a notification of a fact that a connection between vehicle  1  and boost charging facility  2  from connection detection section  100  is detected, communication control section  101  starts a communication with facility controlling apparatus  21 , and maintains the communication. Thus, communication control section  101  and facility controlling apparatus  21  share the fact that vehicle  1  and boost charging facility  2  are connected together. 
         [0042]    In addition, for example, at the time of starting the charging of battery  13 , communication control section  101  sends the above-described charging start control signal to facility controlling apparatus  21 . At this time, communication control section  101  notifies leakage detection circuit  11  of the fact that charging will be started. 
         [0043]    In addition, for example, when receiving a notification of diagnosis results obtained by the normal relay welding diagnosis from circuit diagnosis section  102 , or when receiving a notification of diagnosis results obtained by the relay diagnosis mode from leakage detection circuit  11 , communication control section  101  terminates the communication with facility controlling apparatus  21 . It is to be noted that, when receiving a notification of any of the above-mentioned diagnosis results, communication control section  101  outputs the notification to notification apparatus  12 . Notification apparatus  12  notifies the user of the diagnosis result. 
         [0044]    On the basis of the voltage value notified from voltage detection circuit  16 , circuit diagnosis section  102  performs a voltage detection circuit diagnosis. This diagnosis is a determination whether voltage detection circuit  16  is broken. 
         [0045]    First, when receiving from communication control section  101  a notification of a fact that communication with facility controlling apparatus  21  is started, circuit diagnosis section  102  performs a voltage detection circuit diagnosis. This diagnosis is referred to as “voltage detection circuit diagnosis 1,” which is performed before relays  14  and  15  are turned on, that is, when relays  14  and  15  are in an off state. In voltage detection circuit diagnosis  1 , when no voltage value is notified from voltage detection circuit  16 , circuit diagnosis section  102  determines that voltage detection circuit  16  is not broken. In other words, in voltage detection circuit diagnosis 1, when there is a voltage value notified from voltage detection circuit  16 , circuit diagnosis section  102  determines that voltage detection circuit  16  is broken. Then, circuit diagnosis section  102  notifies relay control section  103  of the fact that voltage detection circuit diagnosis 1 is terminated. 
         [0046]    Thereafter, when the charging of battery  13  is terminated, circuit diagnosis section  102  again performs a voltage detection circuit diagnosis. This diagnosis is referred to as “voltage detection circuit diagnosis 2,”which is performed when relays  14  and  15  are in an on state. In voltage detection circuit diagnosis 2, when there is a voltage value notified from voltage detection circuit  16 , circuit diagnosis section  102  determines that voltage detection circuit  16  is not broken. In other words, in voltage detection circuit diagnosis 2, when no voltage value is notified from voltage detection circuit  16 , circuit diagnosis section  102  determines that voltage detection circuit  16  is broken. 
         [0047]    It is to be noted that examples of the method for detecting a completion of charging of battery  13  by circuit diagnosis section  102  at the time of starting voltage detection circuit diagnosis 2 are as follows. For example, when receiving information representing “completion of charging” from boost charging facility  2 , circuit diagnosis section  102  detects the completion of the charging. The information representing the “completion of charging” is sent from boost charging facility  2  to control apparatus  10  through communication line  18  when the user pushes a charging stop button (not illustrated) of boost charging facility  2 . Alternatively, for example, when information representing “full charge” is received from an ECU (not illustrated) which can detect a state of battery  13 , circuit diagnosis section  102  detects the completion of charging. The information representing “full charge” is sent from the ECU to control apparatus  10  through a signal line (not illustrated) when the ECU detects the fact that charging of battery  13  is completed. 
         [0048]    When results of voltage detection circuit diagnoses 1 and 2 are both that “voltage detection circuit  16  is not broken”(hereinafter referred to as “not broken”), circuit diagnosis section  102  performs the normal relay welding diagnosis. As described above, the normal relay welding diagnosis is a relay welding diagnosis which is performed on the basis of a voltage notified from voltage detection circuit  16 , and an example of the normal relay welding diagnosis is the diagnosis disclosed in PTL 1. Then, when the normal relay welding diagnosis is terminated, circuit diagnosis section  102  notifies communication control section  101  of the results of the diagnosis. 
         [0049]    On the other hand, when at least one of results of voltage detection circuit diagnoses 1 and 2 is that “voltage detection circuit  16  is broken”(hereinafter referred to as “broken”), circuit diagnosis section  102  notifies threshold value determination section  104  of “broken.” 
         [0050]    Relay control section  103  outputs the above-mentioned relay control signal to relays  14  and  15 , and sets relays  14  and  15  to an on or off state. 
         [0051]    For example, when a notification of a fact that voltage detection circuit diagnosis 1 is terminated is received from circuit diagnosis section  102 , relay control section  103  outputs to both relays  14  and  15  relay control signals for turning on relays  14  and  15 . 
         [0052]    In addition, for example, when receiving a request to output a relay control signal from leakage detection circuit  11 , relay control section  103  outputs to at least one of relays  14  and  15  a relay control signal for turning on or off relay  14  or  15 . Thereafter, relay control section  103  notifies leakage detection circuit  11  of the fact that the relay control signal is output. 
         [0053]    Threshold value determination section  104  determines a threshold value which is used by leakage detection circuit  11  in the relay diagnosis mode, and notifies leakage detection circuit  11  of the threshold value thus determined. 
         [0054]    As described above, while the leakage detection mode and the relay diagnosis mode can be switched during the operation of leakage detection circuit  11 , the threshold values used in the modes are different from each other. In the following description, the threshold value used in the leakage detection mode is V0. In addition, the threshold value used in relay diagnosis mode is V1 (an example of first threshold value) and V2 (an example of second threshold value). The level relationship between the threshold values is that V2 is the maximum value and V0 is the minimum value. It is to be noted that V0 is set in advance in leakage detection circuit  11 . 
         [0055]    When receiving from circuit diagnosis section  102  a notification of “broken,” threshold value determination section  104  determines threshold values V1 and V2 by a predetermined determination method. Then, threshold value determination section  104  notifies leakage detection circuit  11  of threshold values V1 and V2 thus determined. When receiving this notification, leakage detection circuit  11  switches the operation from the leakage detection mode to the relay diagnosis mode. It is to be noted that the operation in the relay diagnosis mode may be referred to as “relay welding diagnosis of the present embodiment” in contrast to the above-mentioned normal relay welding diagnosis. 
         [0056]    Here, the method for determining threshold values V1 and V2 performed by threshold value determination section  104  will be described. Examples of the method include the following methods (1) to (3). 
         [0057]    (1) When a resistance value is specified in the standard of boost charging facility  2 , threshold value determination section  104  determines threshold values V1 and V2 on the basis of the resistance value and the constant set in leakage detection circuit  11 . The resistance value herein is the values of resistors  23  and  24  (the same shall apply hereinafter). 
         [0058]    (2) When the resistance value can be acquired through the communication with boost charging facility  2 , threshold value determination section  104  acquires the resistance value from facility controlling apparatus  21 . Then, threshold value determination section  104  determines threshold values V1 and V2 on the basis of the resistance value and the constant set in leakage detection circuit  11 . 
         [0059]    (3) In the cases other than the above-mentioned (1) and (2), threshold value determination section  104  calculates the following expression to determine threshold values V1 and V2. It is to be noted that “A” in the following expression represents a peak level which is obtained when vehicle  1  is in a travel mode when vehicle  1  a stopped state (when vehicle  1  is not boost charged, and inverter and the like are not operated). In addition, “B” in the following expression represents a peak level which is obtained when the relays on the both electrode sides are both in the on state during the relay welding diagnosis. 
         [0000]        V 1= B+ ( A−B )×0.2
 
         [0000]        V 2= B +( A−B )×0.7
 
         [0060]    In the case of the above-mentioned (3), resistors  23  and  24  of boost charging facility  2  have the same constant set in advance. In addition, the resistance value of ammeter  22  is a substantially negligible value. It is to be noted that, the peak level in the case where the relay on one electrode side is in an on state is a substantially intermediate value between A and B. In the case of (3), when there is no significant difference between peak levels A and B, leakage detection circuit  11  determines that the diagnosis cannot be performed (step S 460  of  FIG. 4  described later). 
         [0061]    Leakage detection circuit  11  includes peak value measurement section  110 , comparison diagnosis section  111 , and AC signal output circuit  112  (an example of the signal output circuit). 
         [0062]    AC signal output circuit  112  has a built-in oscillation circuit not illustrated. For example, when performing a leakage detection (leakage detection mode), or when performing a relay welding diagnosis (relay diagnosis mode), AC signal output circuit  112  supplies a predetermined AC voltage to a high pressure line. An output terminal of AC signal output circuit  112  is connected with a high pressure line through resistor  113  and capacitor  17 , in this order, as illustrated in  FIG. 1 . 
         [0063]    Peak value measurement section  110  measures a peak value of a voltage at junction P which is a junction of capacitor  17  and resistor  113 . A voltage at junction P is a voltage supplied by AC signal output circuit  112  to the high pressure line. 
         [0064]    To be more specific, when receiving a notification of threshold values V1 and V2 from threshold value determination section  104 , peak value measurement section  110  is shifted to the relay diagnosis mode, and the operation of peak value measurement section  110  is started. Thus, as described above, AC signal output circuit  112  supplies a predetermined alternating current to the high pressure line. Then, first, peak value measurement section  110  stands by until the peak value of the voltage of junction P is stabilized (for example, for about three seconds). Then, peak value measurement section  110  smoothens the peak value of junction P to perform an analog/digital conversion. In this manner, peak value measurement section  110  measures a peak value. 
         [0065]    It is to be noted that, after receiving the notification of threshold values V1 and V2, peak value measurement section  110  occasionally repeats the measurement of the peak value. In that case, when receiving a notification of a fact that a relay control signal is output from relay control section  103 , peak value measurement section  110  again measures the peak value. 
         [0066]    Then peak value measurement section  110  notifies comparison diagnosis section  111  of peak value 2 measured in the above-mentioned manner. It is to be noted that, at the time of the first measurement of the peak value, peak value measurement section  110  also notifies comparison diagnosis section  111  of the measured threshold values V1 and V2. 
         [0067]    Comparison diagnosis section  111  compares the measurement peak value with the notified threshold value, and determines whether relay  14  and relay  15  are in the on state or off state (hereinafter referred to as “relay state”). 
         [0068]    To be more specific, when receiving a notification of a measured peak value and threshold values V1 and V2 from peak value measurement section  110 , comparison diagnosis section  111  compares the peak value with V1 and V2. On the basis of the results of the comparison, comparison diagnosis section  111  determines the relay state. The details of the determination of the relay state will be described later with reference to  FIGS. 6A to 6C . 
         [0069]    On the basis of the results of the determination of the relay state, comparison diagnosis section  111  determines whether relays  14  and  15  are welded. Comparison determination section  111  notifies the results of the diagnosis (result of the diagnosis by the relay diagnosis mode) of communication control section  101  of control apparatus  10 . 
         [0070]    On the other hand, when the diagnosis result cannot be obtained, comparison diagnosis section  111  requests the output of the relay control signal to relay control section  103  of control apparatus  10 . 
         [0071]    It is to be noted that, comparison diagnosis section  111  may perform both of the notification of diagnosis result by the relay diagnosis mode, and the request of the output of the relay control signal. 
         [0072]    Next, the entire operation of the above-mentioned relay welding diagnostic apparatus according to the present embodiment will be described.  FIG. 3  is a flowchart illustrating an exemplary entire operation of the relay welding diagnostic apparatus according to the present embodiment. 
         [0073]    The user connects the five connectors so as to connect vehicle  1  and boost charging facility  2  together. 
         [0074]    When connection between vehicle  1  and boost charging facility  2  is detected (step S 310 ), control apparatus  10  starts a communication with facility controlling apparatus  21  of boost charging facility  2  (step S 320 ). It is to be noted that, when the above-mentioned (2) is employed as the method for determining a threshold value, control apparatus  10  acquires a resistance value from facility controlling apparatus  21  at this step. 
         [0075]    Next, control apparatus  10  performs voltage detection circuit diagnosis 1, and holds the result of the diagnosis (“broken” or “not broken”) (step S 330 ). 
         [0076]    Next, control apparatus  10  turns on relay  14  and relay  15  in the off state (step S 340 ). 
         [0077]    Next, control apparatus  10  sends a charging start control signal to facility controlling apparatus  21 . When receiving the charging start control signal, facility controlling apparatus  21  controls AC/DC converting apparatus  20  to start power supply. In this manner, control apparatus  10  performs charging of battery  13  (step S 350 ). 
         [0078]    When the charging of battery  13  is terminated, control apparatus  10  performs voltage detection circuit diagnosis 2, and holds the results of the diagnosis (“broken” or “not broken”) (step S 360 ). 
         [0079]    Next, control apparatus  10  performs the relay welding diagnosis (step S 370 ). Here, in accordance with the results of the diagnosis voltage detection circuit diagnoses 1 and 2 held therein, control apparatus  10  selects and performs one of the normal relay welding diagnosis and the relay welding diagnosis (relay diagnosis mode) of the present embodiment. The details of this step will be described later with reference to  FIG. 4 . 
         [0080]    When the relay welding diagnosis is terminated, control apparatus  10  terminates the communication with facility controlling apparatus  21  (step S 380 ). 
         [0081]    The user removes the five connectors, so as to terminate the connection between vehicle  1  and boost charging facility  2 . 
         [0082]    Next, the operation (at step S 370  of  FIG. 3 ) of the relay welding diagnosis of the relay welding diagnostic apparatus according to the present embodiment will be described.  FIG. 4  is a flowchart illustrating an exemplary operation of the relay welding diagnosis performed by the relay welding diagnostic apparatus according to the present embodiment. 
         [0083]    Control apparatus  10  determines whether results of the diagnosis of voltage detection circuit diagnosis 1 and 2 are both “not broken” (step S 410 ). 
         [0084]    When the results of voltage detection circuit diagnoses 1 and 2 are both “not broken” (step S 410 : YES), control apparatus  10  performs the normal relay welding diagnosis (step S 420 ), and terminates the series of processing steps. 
         [0085]    On the other hand, when the results of the diagnosis of voltage detection circuit diagnosis 1 and 2 are both not “not broken” (step S 410 : NO), control apparatus  10  proceeds to step S 430 . 
         [0086]    Control apparatus  10  determines threshold values V1 and V2 for the relay diagnosis mode, and notifies leakage detection circuit  11  of threshold values V1 and V2. Thus, control apparatus  10  controls leakage detection circuit  11  to operate in the relay diagnosis mode (step S 430 ). 
         [0087]    Leakage detection circuit  11  executes the relay state determination process (step S 440 ). As described above, the relay state determination process is a process for determining the relay state which represents whether relays  14  and  15  are in the on state or off state. 
         [0088]    Here, the determination process performed by leakage detection circuit  11  will be described with reference to  FIG. 5  and  FIGS. 6A to 6C .  FIG. 5  is a flowchart illustrating an exemplary operation of the relay state determination process.  FIGS. 6A to 6C  illustrate an exemplary relationship between a peak value and a threshold value in the relay state determination process. 
         [0089]    First, leakage detection circuit  11  stands by until a peak value of a voltage at junction P is stabilized (step S 710 ). 
         [0090]    Next, leakage detection circuit  11  performs an analog/digital conversion to thereby measure the peak value of the voltage at junction P (step S 720 ). 
         [0091]    Next, leakage detection circuit  11  compares the measured peak value with threshold values V1 and V2 (step S 730 ). 
         [0092]    After the comparison, when the peak value is greater than threshold value V2 as illustrated in  FIG. 6A , leakage detection circuit  11  determines that the relays on the both electrode sides, that is, both of relay  14  and  15  are in the off state. 
         [0093]    After the comparison, when the peak value is greater than threshold value V1 and smaller than V2 as illustrated in  FIG. 6B , leakage detection circuit  11  determines that the relay on one electrode side, that is, one of relay  14  and  15  is in the off state. 
         [0094]    After the comparison, when the peak value is smaller than threshold value V1 as illustrated in  FIG. 6C , leakage detection circuit  11  determines that the relays on the both electrode sides, that is, both of relay  14  and  15  are in the on state. 
         [0095]    Here, leakage detection circuit  11  determines whether the result of relay state determination process obtained by the above-mentioned comparison is that the relays on the both electrode sides are both in the on state (step S 450 ). It is to be noted that, at this step, when the above-mentioned (3) is employed as the method for determining the threshold value, leakage detection circuit  11  confirms whether there is a significant difference between peak level A and B. When there is no significant difference, leakage detection circuit  11  proceeds to step S 460 , and when there is a significant difference, leakage detection circuit  11  proceeds to step S 480 . 
         [0096]    When it is determined that the relays on the both electrode sides are not in the on state (step S 450 : NO), leakage detection circuit  11  determines that the diagnosis cannot be performed, and notifies control apparatus  10  of the fact that the diagnosis cannot be performed, as the result of the diagnosis by the relay diagnosis mode (step S 460 ). In turn, control apparatus  10  controls notification apparatus  12  to notify the user of the fact that the relay welding diagnosis cannot be performed. 
         [0097]    Next, leakage detection circuit  11  requests control apparatus  10  to output a relay control signal for turning off the relays on the both electrode sides, that is, both of relay  14  and  15  (step S 470 ). In turn, control apparatus  10  controls relay  14  and  15  to the off state. In this manner, the series of the processing steps are terminated. 
         [0098]    On the other hand, when it is determined that the relays on the both electrode sides are in the on state (step S 450 : YES), leakage detection circuit  11  requests control apparatus  10  to output a relay control signal for turning off the relays on the both electrode sides (step S 480 ). In turn, control apparatus  10  turns off relay  14  and  15 . Then, control apparatus  10  notifies leakage detection circuit  11  of the fact that the relay control signal is output. 
         [0099]    Next, leakage detection circuit  11  again performs the above-mentioned relay state determination process (step S 490 ). 
         [0100]    Then, leakage detection circuit  11  determines whether the result of the relay state determination process obtained by the above-mentioned comparison is that the relays on the both electrode sides are in the off state (step S 500 ). 
         [0101]    When it is determined that, the relays on the both electrode sides are in the off state (step S 500 : YES), leakage detection circuit  11  determines that the relays on the both electrode sides are in the normal state, and notifies control apparatus  10  of the fact that the relays on the both electrode sides are in the normal state as the result of the diagnosis by the relay diagnosis mode (step S 510 ). In turn, control apparatus  10  controls notification apparatus  12  to notify the user of the fact that the relays on the both electrode sides are in the normal state. In this manner, the series of the processing steps are terminated. 
         [0102]    On the other hand, when it is determined that the relays on the both electrode sides are not in the off state (step S 500 : NO), leakage detection circuit  11  determines whether the relay on one electrode side is in the off state (step S 520 ). 
         [0103]    When it is determined that the relay on one electrode side is not in the off state (step S 520 : NO), leakage detection circuit  11  determines that the relay on one electrode side is welded, and notifies control apparatus  10  of the fact that the relay on one electrode side is welded, as the result of the diagnosis by the relay diagnosis mode (step S 530 ). In turn, control apparatus  10  controls notification apparatus  12  to notify the user of the fact that the relay on one electrode side is welded. In this manner, the series of the processing steps are terminated. 
         [0104]    On the other hand, when it is determined that the relay on one electrode side is in the off state (step S 520 : YES), leakage detection circuit  11  requests control apparatus  10  to output a relay control signal for turning on relay  14  on the P electrode side (step S 540 ). In turn, control apparatus  10  turns on relay  14 . Then, control apparatus  10  notifies leakage detection circuit  11  of the fact that the relay control signal is output. 
         [0105]    Next, leakage detection circuit  11  again performs the above-mentioned relay state determination process (step S 550 ). 
         [0106]    Then, leakage detection circuit  11  determines whether the result of the relay state determination process obtained by the above-mentioned comparison is that the relays on the both electrode sides are in the on state (step S 560 ). 
         [0107]    When it is determined that the relays on the both electrode sides are in the on state (step S 560 : YES), leakage detection circuit  11  determines that relay  15  on the N electrode side is welded, and notifies control apparatus  10  of the fact that relay  15  on the N electrode side is welded as the result of the diagnosis by the relay diagnosis mode (step S 570 ). In turn, control apparatus  10  controls notification apparatus  12  to notify the user of the fact that relay  15  on the N electrode side is welded. 
         [0108]    Next, leakage detection circuit  11  requests control apparatus  10  to output a relay control signal for turning on relay  14  on the P electrode side off (step S 580 ). In turn, control apparatus  10  turns off relay  14  on the P electrode side. In this manner, the series of the processing steps are terminated. 
         [0109]    On the other hand, when it is determined that the relays on the both electrode sides are not in the on state (step S 560 : NO), leakage detection circuit  11  determines that relay  14  on the P electrode side is welded, and notifies control apparatus  10  of the fact that relay  14  on the P electrode side is welded, as the result of the diagnosis by the relay diagnosis mode (step S 590 ). In turn, control apparatus  10  controls notification apparatus  12  to notify the user of the fact that relay  14  on the P electrode side is welded. 
         [0110]    Next, leakage detection circuit  11  requests control apparatus  10  to output a relay control signal for turning on relay  14  on the P electrode side off (step S 600 ). In turn, control apparatus  10  turns off relay  14  on the P electrode side. In this manner, the series of the processing steps are terminated. 
         [0111]    It is to be noted that, while an exemplary case where relay  14  on the P electrode side is turned on at step S 540  in the above description, relay  15  on the N electrode side may be turned on. In that case, relay  14  on the P electrode side is determined to be welded at step S 570 , and relay  14  on the P electrode side is turned off at step S 580 . Likewise, relay  15  on the N electrode side is determined to be welded at step S 590 , and the relay on the N electrode side is turned off at step S 600 . 
         [0112]    As has been described, according to the present embodiment, a relay welding diagnosis is performed using a threshold value determined on the basis of a resistance value in a boost charging facility connected with a vehicle, without using a voltage detection circuit. That is, in the present embodiment, even when the voltage detection circuit is broken, a relay welding diagnosis can be executed. 
         [0113]    It is to be noted that the expression “boost” of the term “boost charging” in the above-mentioned embodiment is used for convenience of expression. Therefore, it suffices that the term “charging” in the above-mentioned embodiment is charging which uses an electric energy of direct current. In addition, the expression “high pressure” of the term “high pressure line” the above-mentioned embodiment is used for convenience of expression. Therefore, it suffices that the term “voltage” in the above-mentioned embodiment is a voltage which can charge a battery. 
         [0114]    While the invention made by the present inventor has been specifically described based on the preferred embodiments, it is not intended to limit the present invention to the above-mentioned preferred embodiments but the present invention may be further modified within the scope and spirit of the invention defined by the appended claims. 
         [0115]    For example, in the above-mentioned embodiment, as illustrated in  FIG. 2 , the relay welding diagnostic apparatus of the present embodiment is composed of control apparatus  10  and leakage detection circuit  11 , but the present invention is not limited to this. For example, by additionally providing control apparatus  10  with peak value measurement section  110  and comparison diagnosis section  111 , the relay welding diagnostic apparatus of the present embodiment may be composed only of control apparatus  10 . 
         [0116]    This application is entitled to and claims the benefit of Japanese Patent Application No. 2012-076075 dated Mar. 29, 2012, the disclosure of which including the specification, drawings and abstract is incorporated herein by reference in its entirety. 
       INDUSTRIAL APPLICABILITY 
       [0117]    The relay welding diagnostic apparatus according to the present invention is applicable not only to simple battery-driven electric automobiles, but also to so-called plug-in hybrid vehicles. 
       REFERENCE SIGNS LIST 
       [0000]    
       
           1  Vehicle 
           2  Boost charging facility 
           3   a,    3   b,    3   c,    3   d,    3   e  Connector 
           10  Control apparatus 
           11  Leakage detection circuit 
           12  Notification apparatus 
           13  Battery 
           14  Relay (P electrode side) 
           15  Relay (N electrode side) 
           16  Voltage detection circuit 
           17  Capacitor 
           18  Communication line 
           19  Signal line 
           20  AC/DC converting apparatus 
           21  Facility controlling apparatus 
           22  Ammeter 
           23  Resistor (N electrode side) 
           24  Resistor (P electrode side) 
           100  Connection detection section 
           101  Communication control section 
           102  Circuit diagnosis section 
           103  Relay control section 
           104  Threshold value determination section 
           110  Peak value measurement section 
           111  Comparison diagnosis section 
           112  AC signal output circuit