Abstract:
The relay-welding detection circuit detects welding of relays (RYP, RYN) provided on a charging path from an external power supply (PW) to a first battery ( 14 ), and is provided with: a second battery ( 15 ) that can supply a welding-detection power supply independently of the external power supply (PW); a transistor switch ( 17 ) that is a circuit in which there is substantially zero current flowing in from the external power supply (PW) side of the relays, and that controls whether or not to supply the welding-detection power supply to the second battery ( 15 ) on the basis of the voltage at the external power supply (PW) side of the relays; and a control unit ( 18 ) that is electrically insulated from the transistor switch ( 17 ), and that to detects welding of the relays (RYP, RYN) on the basis of whether or not the transistor switch ( 17 ) has supplied the welding-detection power supply.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a relay welding detection circuit, and more particularly, to a relay welding detection circuit for detecting the welding of a relay which is used for a charging circuit for charging a battery of, for example, an electric vehicle and a power supply system including the relay welding detection circuit. 
       BACKGROUND ART 
       [0002]    A relay circuit for connecting and disconnecting a quick charger to and from a battery connecting junction circuit during charging has been used in a charging circuit of an electric vehicle. A mechanical relay contact (hereinafter, abbreviated to a relay) is used in the relay circuit, and the relay is turned on and off and is welded when a high voltage is applied and a large amount of current flows. A relay welding detection circuit for detecting the welding of the relay has been known (for example, see Patent Literature 1). 
         [0003]    In the related art, when the input-side impedance of the relay welding detection circuit is not a predetermined value (for example, 1 MΩ or less), for example, the problem that a current flows from a quick charger to the welding detection circuit arises. Therefore, it is necessary to increase the input-side impedance of the relay welding detection circuit. In addition, when a detection voltage is insulated and detected, it is necessary to supply driving power to the secondary side. 
       CITATION LIST 
     Patent Literature 
       [0004]    PTL 1 
         [0005]    Japanese Patent Application Laid-Open No. 2006-310219 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0006]    In the relay welding detection circuit according to the related art, power for an insulating device, such as a photocoupler, is ensured from the quick charger. Therefore, the impedance of the relay welding detection circuit is low, and the quick charger determines that to a current flowing to the impedance is a leakage current and does not start charging. 
         [0007]    An object of the present invention is to provide a relay welding detection circuit which can have high impedance and a power supply system using the relay welding detection circuit. 
       Solution to Problem 
       [0008]    According to an aspect of the present invention, there is provided a relay welding detection circuit that is provided in a charging path from an external power supply to an electric storage apparatus, that includes a power supply-side relay and a ground-side relay whose on or of state is independently controllable, and that detects the welding of the relays. The relay welding detection circuit includes: a power supply section that is capable of supplying welding detection power independently from the external power supply; a voltage detection circuit to which almost no current flows from a side of the power supply-side relay close to the external power supply and which controls Whether to supply the welding detection power to the power supply section on the basis of a voltage on the external power supply side of the power supply-side relay; and a control section that independently controls the on or off state of the power supply-side relay and the ground-side relay, that detects the welding of the relays on the basis of whether the voltage detection circuit has supplied the welding detection power, and that is electrically insulated from the voltage detection circuit. 
         [0009]    According to another aspect of the present invention, there is provided a power supply system for an electric vehicle that supplies/cuts off a current to an electric storage apparatus for supplying power to a vehicle driving motor in a charging path from an external power supply to the electric storage apparatus. The power supply system includes: a relay welding detection circuit that includes a power supply-side relay and a ground-side relay whose on or off state is independently controllable and that detects the welding of the relays; a power supply section that is capable of supplying welding detection power independently from the external power supply; a voltage detection circuit to which almost no current flows from a side of the power supply-side relay close to the external power supply and which controls whether to supply the welding detection power to the power supply section on the basis of a voltage on the external power supply side of the power supply-side relay; and a control section that independently controls the on or off state of the power supply-side relay and the ground-side relay that detects the welding of the relays on the basis of whether the voltage detection circuit has supplied the welding detection power, and that is electrically insulated from the voltage detection circuit. The voltage detection circuit is a switch using a transistor. A collector terminal of the transistor is electrically connected to a positive terminal of the power supply section. An emitter terminal of the transistor is electrically connected to a charging path on the external power supply side of the ground-side relay. A base terminal of the transistor is electrically connected to a charging path on the external power supply side of the power supply-side relay. A negative terminal of the power supply section is connected to a negative terminal of the electric storage apparatus. 
       Advantageous Effects of Invention 
       [0010]    According to the present invention, it is possible to provide a relay welding detection circuit which can have high impedance and a power supply system including the relay welding detection circuit. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0011]      FIG. 1  is a diagram illustrating the schematic structure of a power supply system of an electric vehicle according to Embodiment 1 of the present invention. 
           [0012]      FIG. 2  is a flowchart illustrating the process of an operation according to the embodiment. 
           [0013]      FIGS. 3A to 3D  are timing charts of the embodiment. 
           [0014]      FIG. 4  is a diagram illustrating the schematic structure of a power supply system of an electric vehicle according to Embodiment 2 of the present invention. 
           [0015]      FIG. 5  is a flowchart illustrating the process of an operation according to the embodiment. 
           [0016]      FIGS. 6A to 6D  are timing charts of the embodiment. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0017]    Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings. 
       Embodiment 1 
       [0018]      FIG. 1  is a diagram illustrating the schematic structure of a power supply system of an electric vehicle according to Embodiment 1. 
         [0019]    Charging terminal  12  is provided in body  10  of the electric vehicle. Cover  11  is provided in charging terminal  12 . When charging is not performed, cover  11  is closed and charging terminal  12  is shielded from the outside. When charging is performed, cover  11  is opened. During charging, power is supplied from external power supply PW to charging terminal  12  through power supply plug SP. 
         [0020]    A positive (+) terminal of first battery  14  for supplying power to a vehicle driving motor is connected to power supply-side terminal  12 P of charging terminal  12  through power supply-side relay RYP. 
         [0021]    Ground-side terminal  12 N of charging terminal  12  is connected to a negative (−) terminal of the first battery through ground-side relay RYN. 
         [0022]    In addition, a negative terminal of second battery  15  (power supply section) for supplying power to in-vehicle accessories is connected to the negative terminal of first battery  14 . 
         [0023]    A positive terminal of second battery  15  is connected to an anode terminal of photodiode  16 A forming photocoupler  16  and a cathode terminal of photodiode  16 A is connected to a collector terminal of transistor switch  17 . 
         [0024]    An emitter terminal of transistor switch  17  is connected to ground-side terminal I 2 N of charging terminal  12  and a base terminal thereof is connected to power supply-side terminal  12 P (the side of power supply-side relay RYP close to external power supply PW of charging terminal  12  through current-limiting resistor R. A transistor (for example, an FET or a MOS transistor) is used as the switch since the impedance of the terminal for controlling the turning on and off of the switch is very high. That is, the amount of current flowing from the side of power supply-side relay RYP close to external power supply PW to transistor switch  17  (corresponding to a voltage detection circuit) is nearly zero. 
         [0025]    A collector of phototransistor  16 B forming photocoupler  16  is connected to a voltage detection terminal of control section (controller)  18 . An emitter terminal of phototransistor  16 B is connected to the body ground of the vehicle. Control section  18  is electrically insulated from the high voltage side (transistor switch  17 ) by photocoupler  16 . 
         [0026]    Control section  18  forms relay welding determining apparatus  19  that outputs control signal Vryp for controlling the turning an and off of power supply-side relay RYP and control signal Vryn for controlling the turning on and off of ground-side relay RYN. 
         [0027]    Next, an operation according to Embodiment 1 will be described.  FIG. 2  is a flowchart illustrating the process of a welding detection operation according to Embodiment 1. In the welding detection operation, control section  18  controls power supply-side relay RYP and ground-side relay RYN and determines whether the voltage output from first battery  14  is transmitted to the side of power supply-side relay RYP close to the external power supply PW to detect welding during the control operation. When electric energy is supplied from external power supply PW to first battery  14 , the voltage on the side of power supply-side relay RYP close to external power supply PW is fixed to the voltage supplied from external power supply PW. Therefore, the welding detection operation s performed when no electric energy is supplied from external power supply PW to first battery  14 . 
         [0028]    First, control section  18  performs a control operation of outputting control signal Vryp to power supply-side relay RYP to turn off power supply-side relay RYP (Step S 11 ). 
         [0029]    The expression ‘control operation of turning off power supply-side relay RYP’ is used since it is difficult to turn off power supply-side relay RYP when power supply-side relay RYP is in a welded state. 
         [0030]      FIGS. 3A to 3D  are timing charts according to Embodiment 1. 
         [0031]    Control section  18  performs a control operation of outputting control signal Vryn to ground-side relay RYN to turn off ground-side relay RYN (Step S 12 ). 
         [0032]    The expression ‘control operation of turning off ground-side relay RYN’ is used since it is difficult to turn off ground-side relay RYN when ground-side relay RYN is in a welded state. 
         [0033]    Then, control section  18  determines whether a voltage is detected from voltage detection terminal Vde, that is whether a voltage from quick charger QC is detected (Step S 13 ; time t A ). 
         [0034]    When it is determined in Step S 13  that an abnormal voltage is detected from voltage detection terminal Vde (Yes in Step S 13 ), it is determined that power supply-side relay RYP and ground-side relay RYN are welded (Step S 21 ). 
         [0035]    Specifically, it is determined that the relays are welded when the voltage of voltage detection terminal Vde is changed from an “H” level to an “L” level at time t A , as illustrated in the timing chart of  FIG. 3B . 
         [0036]    Control section  18  performs a control operation of outputting control signal Vryp to power supply-side relay RYP to turn off power supply-side relay RYP and a control operation of outputting control signal Vryn to ground-side relay RYN to turn off ground-side relay RYN and ends the process (Step S 24 ). 
         [0037]    When it is determined in Step S 13  that an abnormal voltage is not detected from voltage detection terminal Vde (No in Step S 13 ), control section  18  outputs control signal Vryp to power supply-side relay RYP to turn on power supply-side relay RYP since at least one of power supply-side relay RYP and ground-side relay RYN is in an off state at that time (Step S 14 ). 
         [0038]    Then, control section  18  determines whether a voltage is detected from voltage detection terminal Vde, that is whether a voltage from quick charger QC is detected (Step S 15 ; time t B ). 
         [0039]    When it is determined in Step S 15  that an abnormal voltage is detected from voltage detection terminal Vde (Yes in Step S 15 ), it is determined that ground-side relay RYN is welded (Step S 22 ). 
         [0040]    Specifically, it is determined that the relay is welded when the voltage of voltage detection terminal Vde is at the “H” level at time t A , but is changed from the “H” level to the “L” level at time t B , as illustrated in the timing chart of  FIG. 3C . 
         [0041]    Then, control section  18  performs a control operation of outputting control signal Vryp to power supply-side relay RYP to turn off power supply-side relay RYP and a control operation of outputting control signal Vryn to ground-side relay RYN to turn off ground-side relay RYN (Step S 24 ) and ends the process (end). In  FIGS. 3B to 3D , “end” is the same meaning as “end” illustrated in  FIG. 2 . 
         [0042]    When it is determined in Step S 15  that a voltage is not detected from voltage detection terminal Vde (No in Step S 15 ), the control section  18  performs a control operation of outputting control signal Vryp to power supply-side relay RYP to turn off power supply-side relay RYP since ground-side relay RYN is not welded and is in an off state at that time (Step S 16 ). 
         [0043]    Then, control section  18  outputs control signal Vryn to ground-side relay RYN to turn on ground-side relay RYN (Step S 17 ). 
         [0044]    Then, control section  18  determines whether a voltage is detected from voltage detection terminal Vde, that is, whether a voltage from quick charger QC is detected (Step S 18 ; time t C ). 
         [0045]    When it is determined in Step S 18  that an abnormal voltage is detected from voltage detection terminal Vde (Yes in Step S 18 ), it is determined that power supply-side relay RYP is welded (Step S 23 ). 
         [0046]    Specifically, it is determined that the relay is welded when the voltage of voltage detection terminal Vde is at the “H” level at time t A  and time t B  and is changed to the “L” level at time t C , as illustrated in the timing chart of  FIG. 3D . 
         [0047]    Then, control section  18  performs a control operation of outputting control signal Vryp to power supply-side relay RYP to turn of power supply-side relay RYP and a control operation of outputting control signal Vryn to ground-side relay RYN to turn off ground-side relay RYN (Step S 24 ) and ends the process (end). 
         [0048]    When it is determined in Step S 18  that an abnormal voltage is not detected from voltage detection terminal Vde (No in Step S 18 ), it is determined that power supply-side relay RYP and ground-side relay RYN are not welded, that is, power supply-side relay RYP and ground-side relay RYN are normal (Step S 19 ). 
         [0049]    In this state, specifically, it is determined that the voltage detection terminal Vde is maintained at the “H” level at any of times t A , t B , and t C , as illustrated in the timing chart of  FIG. 3A . 
         [0050]    Then, the control section outputs control signal Vryp to power supply-side relay RYP to turn off power supply-side relay RYP and ground-side relay RYN (Step S 20 ) and ends the process (end). 
         [0051]    As described above, according to Embodiment 1, it is possible to form a high-impedance relay welding detection circuit capable of reliably detecting the welding state of the relay, without using power from the external power supply and to perform an appropriate process such as a warning process. 
       Embodiment 2 
       [0052]      FIG. 4  is a diagram illustrating the schematic structure of a power supply system of an electric vehicle according to Embodiment 2. In  FIG. 4 , the same components as those in  FIG. 1  are denoted by the same reference numerals. 
         [0053]    A positive terminal of battery  14  for supplying power to a vehicle driving motor is connected to power supply-side terminal  12 P of charging terminal  12  of electric vehicle  10  through power supply-side relay RYP. Ground-side terminal  12 N of charging terminal  12  is connected to a negative terminal of battery  14  through ground-side relay RYN. 
         [0054]    In addition, one terminal of capacitor (power supply section) C for supplying power to in-vehicle accessories is connected to power supply-side terminal  12 P of charging terminal  12  through current-limiting resistor R. Ground-side terminal  12 N of charging terminal  12  is connected to the other terminal of capacitor C. 
         [0055]    A collector of phototransistor  20 B forming second photocoupler  20  is connected to a connection point between capacitor C and current-limiting resistor R. 
         [0056]    An anode terminal of photodiode  20 A forming second photocoupler  20  is connected to control terminal Vc 2  of control section  18 , and a cathode terminal thereof is connected to the body ground of vehicle body  10 . 
         [0057]    An emitter terminal of phototransistor  20 B is connected to an anode terminal of photodiode  16 A forming first photocoupler  16  and a cathode terminal of photodiode  16 A is connected to a collector of transistor switch  17 . 
         [0058]    An emitter terminal of transistor switch  17  is connected to ground-side terminal  12 N of charging terminal  12 , and a base thereof is connected to power supply-side terminal  12 P of charging terminal  12  through current-limiting resistor R. 
         [0059]    A collector of phototransistor  16 B forming first photocoupler  16  is connected to voltage detection terminal Vde of control section (controller)  18 . An emitter of phototransistor  16 B is connected to the body ground of vehicle body  10 . 
         [0060]    Control section  18  farms relay welding determining apparatus  21  that outputs control signal Vryp for controlling the turning on and off of power supply-side relay RYP and control signal Vryn for controlling the turning on and off of ground-side relay RYN. Control section  18  outputs an “H” level control signal from control terminal Vc 2  when it is determined whether the relay is welded. 
         [0061]    Next, an operation according to Embodiment 2 will be described.  FIG. 5  is a flowchart illustrating a welding detection operation according to Embodiment 2. 
         [0062]    First, control section  18  performs a control operation of outputting control signal Vryp to power supply-side relay RYP to turn off power supply-side relay RYP (Step S 31 ). 
         [0063]    Here, similarly to Embodiment 1, the expression ‘control operation of turning off power supply-side relay RYP’ is used since it is difficult to turn off power supply-side relay RYP when power supply-side relay RYP is in a welded state. 
         [0064]    Then, control section  18  performs a control operation of outputting control signal Vryn to ground-side relay RYN to turn off ground-side relay RYN (Step S 32 ). 
         [0065]    The expression ‘control operation of turning off ground-side relay RYN’ used since it is difficult to turn off ground-side relay RYN when ground-side relay RYN is in a welded state. 
         [0066]    Control section  18  outputs an “H” level control signal from control terminal Vc 2  to turn on second photocoupler  20  (Step S 33 ). 
         [0067]    As a result, power can be supplied to photodiode  16 A of first photocoupler  16 . 
         [0068]    Then, control section  18  determines whether an abnormal voltage is detected from voltage detection terminal Vde, that is, whether a voltage from quick charger QC is detected (Step S 34 ; time t D ). 
         [0069]    When it is determined in Step S 34  that an abnormal voltage is detected from voltage detection terminal Vde (Yes in Step S 34 ), it is determined that power supply-side relay RYP and ground-side relay RYN are welded (Step S 43 ). 
         [0070]    Specifically, it is determined that the relays are welded when the voltage of voltage detection terminal Vde is changed to an “L” level at time t D , as illustrated in the timing chart of  FIG. 6B . 
         [0071]    Then, control section  18  performs a control operation of outputting control signal Vryp to power supply-side relay RYP to turn of power supply-side relay RYP and a control operation of outputting control signal Vryn to ground-side relay RYN to turn off ground-side relay RYN (Step S 46 ), outputs an “L” level control signal from control terminal Vc 2  to turn off second photocoupler  20  (Step S 47 ), and ends the process (end). 
         [0072]    When it is determined in Step S 34  that an abnormal voltage is not detected from voltage detection terminal Vde (No in Step S 34 ), control section  18  outputs control signal Vryp to power supply-side relay RYP to turn on power supply-side relay RYP since at least one of power supply-side relay RYP and ground-side relay RYN is in an off state at that time (Step S 35 ). 
         [0073]    Then, control section  18  determines whether an abnormal voltage is detected from the voltage detection terminal Vde, that is, whether a voltage from quick charger QC is detected (Step S 36 ; time t E ). 
         [0074]    When it is determined in Step S 36  that an abnormal voltage is detected from voltage detection terminal Vde (Yes in Step S 36 ), it is deter that ground-side relay RYN is welded (Step S 44 ). 
         [0075]    Specifically, it is determined that the relay is welded when the voltage of voltage detection terminal Vde is at an “H” level at time t D  and is changed to an “L” level at time t E , as illustrated in the timing chart of  FIG. 6C . 
         [0076]    Then, control section  18  performs a control operation of outputting control signal Vryp to power supply-side relay RYP to turn off power supply-side relay RYP and a control operation of outputting control signal Vryn to ground-side relay RYN to turn off ground-side relay RYN (Step S 46 ), outputs an “L” level control signal from control terminal Vc 2  to turn off second photocoupler  20  (Step S 47 ), and ends the process (end). 
         [0077]    When it is determined in Step S 36  that an abnormal voltage is not detected from voltage detection terminal Vde (No in Step S 36 ), the control section performs a control operation of outputting control signal Vryp to power supply-side relay RYP to turn off power supply-side relay RYP since pound-side relay RYN is not welded and is in an off state at that time (Step S 37 ). 
         [0078]    Then, control section  18  outputs control signal Vryn to ground-side relay RYN to turn on ground-side relay RYN (Step S 38 ). 
         [0079]    Then, control section  18  determines whether an abnormal voltage is detected from voltage detection terminal Vde, that is, whether a voltage from the quick charger is detected (Step S 39 ; time t F ). 
         [0080]    When it is determined in Step S 39  that an abnormal voltage is detected from voltage detection terminal Vde (Yes in Step S 39 ), it is determined that power supply-side relay RYP is welded (Step S 45 ). 
         [0081]    Specifically, it is determined that the relay is welded when the voltage of voltage detection terminal Vde is maintained at an “H” level at any of times t D  and t E , but is changed to an “L” level at time t F , as illustrated in the timing chart of  FIG. 6D . 
         [0082]    Then, control section  18  performs a control operation of outputting control signal Vryp to power supply-side relay RYP to turn off power supply-side relay RYP and a control operation of outputting control signal Vryn to ground-side relay RYN to turn off ground-side relay RYN (Step S 46 ), outputs an “L” level control signal from control terminal Vc 2  to turn off second photocoupler  20  (Step S 47 ), and ends the process (end). 
         [0083]    When it is determined in Step S 39  that an abnormal voltage is not detected from voltage detection terminal Vde (No in Step S 39 ), it is determined that power supply-side relay RYP and ground-side relay RYN are not welded, that is, whether power supply-side relay RYP and ground-side relay RYN are normal (Step S 40 ). 
         [0084]    Specifically, this state is obtained when the voltage of voltage detection terminal Vde is maintained at an “H” level at any of times t D , t E , and t F , as illustrated in the timing chart of  FIG. 6A . 
         [0085]    Then, the control section outputs control signal Vryp to power supply-side relay RYP to turn off power supply-side relay RYP and ground-side relay RYN (Step S 41 ). 
         [0086]    Then, control section  18  outputs an “L” level control signal from control terminal Vc 2  to turn off second photocoupler  20  (Step S 42 ) and ends the process (end). 
         [0087]    As described above, according to Embodiment 2, it is possible to form a high-impedance relay welding detection circuit capable of reliably detecting the welding state of the relay, without using power from the external power supply, and perform an appropriate process such as a warning process. 
         [0088]    The disclosure of Japanese Patent Application No. 2011-074689, filed on Mar. 30, 2011, including the specification, drawings and abstract, is incorporated herein by reference in its entirety. 
       INDUSTRIAL APPLICABILITY 
       [0089]    The relay welding detection circuit and the power supply system using the relay welding detection circuit according to the present invention can he applied to a so-called hybrid vehicle or plug-in hybrid vehicle, in addition to the electric vehicle driven by the battery. 
       REFERENCE SIGNS LIST 
       [0090]      10  Vehicle 
         [0091]      11  Cover 
         [0092]      12  Charging terminal 
         [0093]      12 N Ground-side terminal 
         [0094]      12 P Power supply-side terminal 
         [0095]      14  First battery 
         [0096]      15  Second battery (Power supply section, Electric storage section) 
         [0097]      16  Photocoupler 
         [0098]      16 A Photodiode 
         [0099]      16 B Phototransistor 
         [0100]      17  Transistor switch 
         [0101]      18  Control section 
         [0102]      19  Relay welding determining apparatus 
         [0103]      20  Second photocoupler 
         [0104]      20 A Photodiode 
         [0105]      20 B Phototransistor 
         [0106]      21  Relay welding determining apparatus 
         [0107]    C Capacitor (Power supply section, Electric storage section) 
         [0108]    PW External power supply 
         [0109]    QC Quick charger 
         [0110]    R Current-limiting resistor 
         [0111]    RYN Ground-side relay 
         [0112]    RYP Power supply-side relay 
         [0113]    SP Power supply plug 
         [0114]    Vc 2  Control terminal 
         [0115]    Vde Voltage detection terminal 
         [0116]    Vryn Control signal 
         [0117]    Vryp Control signal