Relay circuit and vehicle provided with same

Abstract

The invention relates to a relay circuit and a vehicle having the same. The relay circuit includes a contact relay and a voltage generation circuit. The contact relay includes an electrical contact and a coil. The coil drives the electrical contact. The voltage generation circuit generates an applied voltage to the coil. When the applied voltage exceeds the operating voltage of the contact relay, the electric contact is closed, and when the applied voltage becomes lower than the reset voltage of the contact relay, which is lower than the operating voltage, the electric contact is opened. The voltage generation circuit closes the electrical contact by generating the applied voltage such that the applied voltage exceeds the operating voltage, and then generates the applied voltage such that the applied voltage drops and is held at a step-down voltage that is lower than the operating voltage and higher than the reset voltage.

Description

Technical Field

[0001] The present disclosure relates to a relay circuit and a vehicle having the same. Background Art

[0002] Japanese Patent Application Laid-Open No. 2007-244034 discloses a power supply device for a vehicle. The power supply device includes a battery and a contact relay. The electric contacts of the contact relay are driven using the power of the battery. Summary of the invention

[0003] The electric contact is generally driven by a coil. For example, the electric contact is opened or closed according to the voltage applied to the coil. Japanese Patent Application Laid-Open No. 2007-244034 does not discuss a technique for effectively reducing power consumption when driving the electric contact.

[0004] The present disclosure has been made to solve the above-mentioned problems, and an object of the present disclosure is to provide a relay circuit and a vehicle that can effectively reduce power consumption when driving an electric contact.

[0005] A relay circuit of the present disclosure includes a contact relay and a voltage generating circuit.

[0006] A contact relay includes an electrical contact and a coil for driving the electrical contact.

[0007] The voltage generating circuit is connected to the coil and generates a voltage to be applied to the coil.

[0008] If the applied voltage exceeds the first voltage, the electrical contact is closed.

[0009] When the applied voltage becomes lower than a second voltage that is lower than the first voltage, the electrical contact is disconnected.

[0010] The voltage generating circuit generates the applied voltage so that the applied voltage exceeds the first voltage to close the electrical contact, and then generates the applied voltage so that the applied voltage is reduced and maintained at a third voltage that is lower than the first voltage and higher than the second voltage.

[0011] According to the present disclosure, it is possible to effectively reduce power consumption when driving the electric contacts. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Features, advantages and technical and industrial significance of exemplary embodiments of the present invention will be described below with reference to the accompanying drawings, in which like numerals represent like elements, and in which:

[0013] Figure 1 A diagram schematically showing the structure of a vehicle equipped with a relay circuit;

[0014] Figure 2 is a diagram showing a detailed structure of a relay circuit;

[0015] Figure 3 is a time chart for specifically explaining the transition of the voltage applied to the coil;

[0016] Figure 4 is a flowchart illustrating a process performed by a control unit;

[0017] Figure 5 is a diagram showing a detailed structure of a relay circuit;

[0018] Figure 6 It is a time chart for specifically explaining the transition of the voltage applied to the coil. DETAILED DESCRIPTION

[0019] Hereinafter, with reference to the attached drawings, the embodiments of the present disclosure will be described. Figure 1 The same or corresponding parts in the drawings are denoted by the same reference numerals, and their description will not be repeated. The embodiments and their modifications may be appropriately combined with each other.

[0020] Figure 1 FIG. 2 is a diagram schematically showing a structure of a vehicle equipped with a relay circuit according to an embodiment. Figure 1 The vehicle 10 is a battery electric vehicle (BEV). The vehicle 10 is configured to be able to transmit power between an electric device 20 (described later) provided outside the vehicle 10 and the vehicle 10. The vehicle 10 may be replaced by another type of electric vehicle such as a PHEV (Plug-in Hybrid Electric Vehicle).

[0021] The vehicle 10 includes a battery 102 , power lines PL1 to PL3 and NL1 to NL3 , an inlet 104 , a drive device 105 , relay circuits 110 and 115 , voltage sensors 150 and 160 , a capacitor 155 , and an ECU (Electronic Control Unit) 180 .

[0022] The battery 102 is a secondary battery such as a lithium ion battery, and is an example of a “power storage device” in the present disclosure. The battery 102 stores electric power for driving the vehicle 10 .

[0023] The power line PL1 is a high potential side power line connected to the positive electrode of the battery 102. The power line NL1 is a low potential side power line connected to the negative electrode of the battery 102.

[0024] The socket 104 is configured to be connectable to the power equipment 20. The power equipment 20 includes a power supply device 205 and a connector 210. The power supply device 205 supplies power to the vehicle 10 using power from the power grid PG. The connector 210 is connected (plugged) to the socket 104.

[0025] The drive device 105 includes a converter 106 and a motor 108. The converter 106 is connected to power lines PL2 and NL2, and converts the DC power supplied from the battery 102 through a relay circuit 115 (described later) into AC power. The motor 108 receives the AC power and generates a driving force for the vehicle 10. The power lines PL2 and NL2 are respectively a high potential side power line and a low potential side power line connected to the drive device 105.

[0026] Relay circuit 110 is connected to a power line pair (power lines PL3 and NL3) connected to socket 104. Relay circuit 110 includes terminals P1, P2, N1, and N2. Terminals P1 and N1 are connected to power lines PL3 and NL3, respectively. Terminals P2 and N2 are connected to power lines PL2 and NL2, respectively.

[0027] Relay circuit 115 is provided between battery 102 and drive device 105. Relay circuit 115 includes terminals P3, P4, N3, and N4. Terminals P3 and N3 are connected to power lines PL2 and NL2, respectively. Terminals P4 and N4 are connected to power lines PL1 and NL1, respectively.

[0028] Relay circuits 110 and 115 each include a plurality of contact relays (described later). Relay circuit 110 is turned on when power is transmitted between vehicle 10 and power equipment 20. Relay circuit 115 is turned on when vehicle 10 is driven, and is also turned on when power is transmitted. Power transmission may be either external charging in which battery 102 is charged using power supplied from power equipment 20, or external discharge in which the discharged power of battery 102 is released to the outside of vehicle 10. In this example, since the power supplied is direct current power, external charging is also referred to as "DC charging". In the following description, DC charging is used as an example of power transmission.

[0029] Voltage sensor 150 detects voltage V1 between power lines PL3 and NL3. Capacitor 155 is connected between the power line pair formed by power lines PL2 and NL2. Capacitor 155 is pre-charged with power from battery 102 before DC charging starts in order to prevent surge current at the start of DC charging. Voltage sensor 160 detects voltage VH across capacitor 155. Voltage VH corresponds to the voltage between power lines PL2 and NL2.

[0030] ECU 180 includes a processor and a memory (neither of which is shown in the figure). The processor is, for example, a CPU (Central Processing Unit), which performs various calculations. The memory includes a ROM (Read Only Memory) and a RAM (Random Access Memory). The ROM stores a program executed by the processor.

[0031] ECU 180 controls various devices of vehicle 10 according to the detected values ​​of various physical quantities such as voltages VI and VH. The devices include drive device 105 and relay circuits 110 and 115.

[0032] When the connector 210 is connected to the socket 104, the ECU 180 establishes a communication connection with the power device 20, for example, through CAN (Controller Area Network) communication, and sends and receives various signals. In one example, the ECU 180 uses the signal to start or stop DC charging. When DC charging is started or stopped, the ECU 180 notifies the control unit 126, 136 (described later) of the intention. The ECU 180 exchanges various information (prior information) with the power device 20 before starting DC charging. After completing the exchange of the prior information, the ECU 180 performs a prescribed insulation diagnostic process.

[0033] Figure 2 1 is a diagram showing a detailed configuration of the relay circuit 110. Figure 2 The relay circuit 110 includes contact relays 120 -B, 120 -G and a voltage generating circuit 122 .

[0034] Contact relays 120-B and 120-G are DC charging relays connected to power lines PL3 and NL3, respectively. Contact relay 120-B includes an electric contact RY11 and a coil DCR-B1. Electric contact RY11 is connected between power lines PL2 and PL3, and is driven by coil DCR-B1 using power from an auxiliary battery 128 (described later). For example, if the applied voltage V11 to coil DCR-B1 exceeds the operating voltage of contact relay 120-B, electric contact RY11 is closed. If the applied voltage V11 becomes lower than the reset voltage of contact relay 120-B, electric contact RY11 is opened. The reset voltage is higher than zero voltage (0V) and lower than the operating voltage.

[0035] The contact relay 120-G includes an electric contact RY12 and a coil DCR-G1. The electric contact RY12 is connected between the power lines NL2 and NL3, and is driven by the coil DCR-G1 using the power of the auxiliary battery 128. For example, if the applied voltage V12 to the coil DCR-G1 exceeds the operating voltage of the contact relay 120-G, the electric contact RY12 is closed. If the applied voltage V12 becomes lower than the reset voltage of the contact relay 120-G, the electric contact RY12 is opened. The operating voltage and reset voltage of the contact relay 120-G are respectively equal to the operating voltage and reset voltage of the contact relay 120-B.

[0036] The voltage generating circuit 122 includes a voltage generating unit 124 and a control unit 126. The voltage generating unit 124 is connected to the coils DCR-B1 and DCR-G1, respectively, and generates applied voltages V11 and V12. The voltage generating unit 124 includes an auxiliary battery 128, a step-down converter 129, a diode D1, resistors R10 to R12, and switching elements Q10 to Q12 and M10 to M12.

[0037] Auxiliary battery 128 functions as a power supply node of a low voltage system such as voltage generation circuit 122, and generates power supply voltage VBB. Power supply voltage VBB is higher than the operating voltage of contact relays 120-B and 120-G.

[0038] The step-down converter 129 is a DC / DC converter that converts the power supply voltage VBB into a stepped-down voltage VCC and outputs the stepped-down voltage VCC. The stepped-down voltage VCC is lower than the operating voltage of the contact relays 120-B and 120-G and higher than the reset voltage of these contact relays.

[0039] The buck converter 129 includes an input terminal Te1, an output terminal Te2, a switching element 129Q, a diode 129D, and an inductor 129L. The input terminal Te1 is connected to the auxiliary battery 128. The output terminal Te2 is connected to the anode of the diode D1. In the diode D1, current flows only when the potential on its anode side (step-down voltage VCC) is higher than the potential on its cathode side. The voltage drop of the diode D1 is so small that it can be ignored. The main electrode of one side of the switching element 129Q is connected to the positive electrode of the auxiliary battery 128 through the input terminal Te1. The main electrode of the other side of the switching element 129Q is connected to the cathode of the inductor 129L and the diode 129D. The switching element 129Q is driven (turned on and off) by the control unit 126.

[0040] The switch elements Q10 to Q12 are bipolar transistors, respectively. The switch elements M10 to M12 are MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors).

[0041] The control unit 126 controls the on / off state of the switching elements Q10~Q12 according to the instructions from the ECU180. If the control unit 126 turns on the switching element Q10, the power supply voltage VBB is applied to the resistor R10. In this case, the switching element M10 is turned on. Then, if the control unit 126 turns on the switching element Q11, the power supply voltage VBB is applied to the resistor R11. In this case, the switching element M11 is turned on, and the coil DCR-B1 is electrically connected to the auxiliary battery 128. As a result, the applied voltage V11 rises to the power supply voltage VBB higher than the aforementioned operating voltage. As a result, the electrical contact RY11 is closed. Thereafter, if the control unit 126 disconnects both the switching elements Q10 and Q11, the coil DCR-B1 is electrically disconnected from the auxiliary battery 128. As a result, the applied voltage V11 becomes lower than the reset voltage and drops to zero voltage, and the electrical contact RY11 is disconnected.

[0042] Similarly, when the control unit 126 turns on the switch element Q12 while the switch element M10 is turned on, the power supply voltage VBB is applied to the resistor R12. In this case, the switch element M12 is turned on, and the coil DCR-G1 is electrically connected to the auxiliary battery 128. As a result, the applied voltage V12 rises to the power supply voltage VBB. As a result, the electric contact RY12 is closed. Thereafter, when the control unit 126 turns off both the switch elements Q10 and Q12, the applied voltage V12 drops to zero voltage, and the electric contact RY12 is opened.

[0043] It is important to effectively reduce the power consumption of the auxiliary battery 128 when driving the electric contacts RY11 and RY12. The lower the applied voltages V11 and V12, the smaller the power consumption of the coils DCR-B1 and DCR-G1. On the other hand, if the applied voltages V11 and V12 are too low, the electric contacts RY11 and RY12 cannot be controlled to a closed state. The following describes the structure of the relay circuit 110 for coping with such a problem.

[0044] When the electric contact RY11 is driven, the control unit 126 of the relay circuit 110 controls the voltage generating unit 124 to generate the applied voltage V11 in such a manner that the applied voltage V11 exceeds the operating voltage, thereby closing the electric contact RY11. Thereafter, the control unit 126 controls the voltage generating unit 124 to generate the applied voltage V11 in such a manner that the applied voltage V11 is reduced and maintained at an intermediate voltage (in this example, the step-down voltage VCC) within a voltage range that is lower than the aforementioned operating voltage and higher than the reset voltage. Similarly, when the electric contact RY12 is driven, the control unit 126 controls the voltage generating unit 124 to generate the applied voltage V12 in such a manner that the applied voltage V12 exceeds the operating voltage, thereby closing the electric contact RY12. Thereafter, the control unit 126 controls the voltage generating unit 124 to generate the applied voltage V12 in such a manner that the applied voltage V12 is reduced and maintained at the step-down voltage VCC.

[0045] By forming such a structure, after the electric contacts RY11 and RY12 are closed, the applied voltages V11 and V12 drop and are maintained at the step-down voltage VCC. Since the step-down voltage VCC is higher than the reset voltage, the closed state of these electric contacts is maintained. When the applied voltages V11 and V12 are the step-down voltage VCC, the power consumption in the coils DCR-B1 and DCR-G1 is smaller than when the applied voltages V11 and V12 are the power supply voltage VBB. Therefore, according to the above-mentioned structure, the power consumption in the coils DCR-B1 and DCR-G1 can be reduced while maintaining the closed state of the electric contacts RY11 and RY12. As a result, the power consumption of the auxiliary battery 128 when driving these electric contacts during DC charging can be effectively reduced (power efficiency can be improved).

[0046] The following is a more specific description of a method for causing the applied voltages V11 and V12 to rise to the power supply voltage VBB and then fall to the step-down voltage VCC. For example, with respect to the applied voltage V11, the control unit 126 electrically connects the auxiliary battery 128 to the coil DCR-B1 by turning on the switch element Q11 (making the switch elements M10 and M11 conductive) after the switch element Q10 is turned on. As a result, the applied voltage V11 rises to the power supply voltage VBB and the electrical contact RY11 is closed. Thereafter, the control unit 126 electrically connects the output terminal Te2 of the step-down converter 129 to the coil DCR-B1 via the diode D1 instead of the auxiliary battery 128 by turning off the switch element Q10. As a result, the applied voltage V11 falls to the step-down voltage VCC.

[0047] Similarly, regarding the applied voltage V12, the control unit 126 turns on the switch element Q12 after the switch element Q10 is turned on (turns on the switch elements M10 and M12) to electrically connect the auxiliary battery 128 to the coil DCR-G1. As a result, the applied voltage V12 rises to the power supply voltage VBB and the electrical contact RY12 is closed. Thereafter, the control unit 126 turns off the switch element Q10 to electrically connect the output terminal Te2 of the step-down converter 129 to the coil DCR-G1 via the diode D1 instead of the auxiliary battery 128. As a result, the applied voltage V12 drops to the step-down voltage VCC.

[0048] When the auxiliary battery 128 is electrically connected to the coils DCR-B and DCR-G, the applied voltages V11 and V12 are the power supply voltage VBB. When the connection destinations of the coils DCR-B and DCR-G are switched from the auxiliary battery 128 to the output terminal Te2 of the step-down converter 129, the applied voltages V11 and V12 are respectively reduced from the power supply voltage VBB to the step-down voltage VCC. Thus, by switching the connection destinations of each coil as described above, the applied voltages V11 and V12 can be easily maintained within a voltage range lower than the operating voltage and higher than the reset voltage.

[0049] Figure 3 This is a timing chart for specifically describing the transition of applied voltages V11 and V12 in the embodiment. The figure shows, from the top, the on / off states of switching elements Q10 to Q12, the applied voltages V11 and V12, and the open / close states of electric contacts RY11 and RY12.

[0050] Reference Figure 3 During the period from time t0 to time t1, the connector 210 is connected to the socket 104, and the aforementioned prior information is exchanged between the ECU 180 and the power device 20. In addition, the user operation of locking the connector 210 is performed, and the insulation diagnosis process starts. During the period from time t0 to time t1, the switching elements Q10 to Q12 are in the off state, and the applied voltages V11 and V12 are zero voltage. As a result, the electrical contacts RY11 and RY12 are in the open state.

[0051] At time t1, control unit 126 turns on switching elements Q10 to Q12. As a result, coils DCR-B1 and DCR-G1 are electrically connected to auxiliary battery 128, and applied voltages V11 and V12 rise from zero voltage to power supply voltage VBB. As a result, electrical contacts RY11 and RY12 are closed.

[0052] At time t2, DC charging starts, and the control unit 126 turns off the switch element Q10. As a result, the connection destination of each coil is switched from the auxiliary battery 128 to the output terminal Te2 of the step-down converter 129, and the applied voltages V11 and V12 are reduced from the power supply voltage VBB to the step-down voltage VCC. During the period from time t2 to time t4 (period TP1), these applied voltages are respectively maintained at the step-down voltage VCC, so the electrical contacts RY11 and RY12 are still in the closed state. At time t4p, which is a predetermined time before time t4, DC charging stops.

[0053] At time t4, the control unit 126 turns off the switch elements Q11 and Q12. As a result, the switch elements M11 and M12 are no longer conducting. As a result, each coil is electrically disconnected from the step-down converter 129, and the applied voltages V11 and V12 become lower than the reset voltage and drop to zero voltage. As a result, the electrical contacts RY11 and RY12 are disconnected.

[0054] During a period from time t5 to time t7 , ECU 180 executes a welding diagnosis process for diagnosing the presence or absence of welding of electric contacts RY11 , RY12 according to voltage VH.

[0055] After time t7, ECU 180 checks voltage V1 and terminates communication with electric device 20. After the user operates to unlock connector 210, connector 210 is unplugged from inlet 104.

[0056] Figure 4 1 is a flowchart illustrating the processing executed by the control unit 126. This flowchart is executed after the information is exchanged in advance ( Figure 3 The time t1) starts.

[0057] Reference Figure 4 , the control unit 126 turns on the switch elements Q11 and Q12 (S105). As a result, the applied voltages V11 and V12 exceed the operating voltage and rise to the power supply voltage VBB, and the electric contacts RY11 and RY12 are closed.

[0058] The control unit 126 determines whether DC charging has started according to the notification from the ECU 180 (S115). If DC charging has not started (No in S115), the process returns to S105, and the applied voltages V11 and V12 are maintained at the power supply voltage VBB. If DC charging has started (Yes in S115), the process proceeds to S120.

[0059] When DC charging starts, the control unit 126 turns off the switching element Q10 while maintaining the switching elements Q11 and Q12 in the on state (S120). As a result, the applied voltages V11 and V12 drop to the step-down voltage VCC, but the closed state of the electrical contacts RY11 and RY12 is maintained.

[0060] The control unit 126 determines whether the DC charging has stopped according to the notification from the ECU 180 (S125). If the DC charging has not stopped (No in S125), the process returns to S120, and the applied voltages V11 and V12 are maintained at the step-down voltage VCC. If the DC charging has stopped (Yes in S125), the control unit 126 waits for a predetermined period, and then, at time t4, disconnects the switching elements Q11 and Q12 (S130). As a result, the applied voltages V11 and V12 drop to zero voltage, and the electrical contacts RY11 and RY12 are disconnected. After that, the process ends.

[0061] The vehicle 10 can perform DC charging by establishing an electrical connection between the vehicle 10 and the power device 20. In order to establish this electrical connection, the electrical contacts RY11 and RY12 of the relay circuit 110 need to be in a closed state. According to the embodiment, the power consumption of the auxiliary battery 128 when these electrical contacts are controlled to be in a closed state (for example, during the period TP1) can be effectively reduced. In addition, after the completion of DC charging, it is possible to avoid the situation where the power of the auxiliary battery 128 is exhausted due to the power consumption in the low-voltage system of the vehicle 10.

[0062] [Modifications]

[0063] In this modification, a method for reducing the relay circuit 115 ( Figure 1 ) when driving the electric contact. As described below, the aforementioned voltage control for the contact relays 120-B and 120-G can also be applied to each contact relay of the relay circuit 115.

[0064] Figure 5 1 is a diagram showing a detailed configuration of the relay circuit 115. Figure 5 The relay circuit 115 is different from the relay circuit 110 ( Figure 2 The relay circuit 115 is further different from the relay circuit 110 in that it includes a contact relay 130-P and a resistance element RP.

[0065] Contact relays 130-B, 130-G, and 130-P are system main relays provided in the circuit between battery 102 and drive device 105. Contact relay 130-B includes electric contact RY21 and coil DCR-B2. Contact relay 130-G includes electric contact RY22 and coil DCR-G2. Contact relay 130-P includes electric contact RY23 and coil DCR-P2. The voltages applied to coils DCR-B2, DCR-G2, and DCR-P2 are also represented as applied voltages V21, V22, and V23, respectively.

[0066] The electric contact RY21 is connected between the power lines PL1 and PL2. The electric contact RY22 is connected between the power lines NL1 and NL2. The electric contact RY23 is provided in parallel with the electric contact RY22 and is connected to the power line NL1 through the resistor RP. The resistor RP is connected to the electric contact RY23 as a capacitor 155 ( Figure 1 ) is set as a discharge resistor for pre-charging.

[0067] The electric contact RY21 is driven by the coil DCR-B2 according to the applied voltage V21. The electric contact RY22 is driven by the coil DCR-G2 according to the applied voltage V22. The electric contact RY23 is driven by the coil DCR-P2 according to the applied voltage V23.

[0068] For example, if the applied voltage V21 exceeds the operating voltage of the contact relay 130-B, the electric contact RY21 is closed. If the applied voltage V21 becomes lower than the reset voltage of the contact relay 130-B, the electric contact RY21 is opened. Similarly, if the applied voltages V22 and V23 exceed the operating voltage of the contact relay 130-G and the operating voltage of the contact relay 130-P, respectively, the electric contacts RY22 and RY23 are closed. If the applied voltages V22 and V23 become lower than the reset voltage of the contact relay 130-G and the reset voltage of the contact relay 130-P, respectively, the electric contacts RY22 and RY23 are opened.

[0069] The operating voltages of the contact relays 130-B, 130-G, and 130-P are equal to each other and are the same as the contact relays 120-B and 120-G ( Figure 2 Similarly, the reset voltages of the contact relays 130-B, 130-G, and 130-P are equal to each other and are the same as the reset voltages of the contact relays 120-B and 120-G.

[0070] The voltage generating circuit 132 includes a voltage generating unit 134 and a control unit 136. The voltage generating unit 134 is connected to the coils DCR-B2, DCR-G2, and DCR-P2, respectively, and is configured to generate applied voltages V21, V22, and V23. The voltage generating unit 124 includes an auxiliary battery 138, a step-down converter 139, a diode D11, resistors R20 to R23, and switching elements Q20 to Q23, and M20 to M23.

[0071] The auxiliary battery 138, the buck converter 139 and the diode D11 are connected to the auxiliary battery 128, the buck converter 129 and the diode D1 (all refer to Figure 2 ). The switch elements Q20 to Q23 are bipolar transistors. The switch elements M20 to M23 are MOSFETs.

[0072] The control unit 136 controls the on / off state of the switching elements Q20~Q23 according to the instructions from the ECU180. If the control unit 136 turns on the switching element Q10, the power supply voltage VBB is applied to the resistor R20. In this case, the switching element M20 is turned on. Then, if the control unit 136 turns on the switching element Q21, the power supply voltage VBB is applied to the resistor R21. In this case, the switching element M21 is turned on, and the coil DCR-B2 is electrically connected to the auxiliary battery 138. As a result, the applied voltage V21 rises to the power supply voltage VBB higher than the operating voltage. As a result, the electrical contact RY21 is closed. Thereafter, if the control unit 136 disconnects both the switching elements Q20 and Q21, the coil DCR-B2 is electrically disconnected from the auxiliary battery 138. As a result, the applied voltage V21 becomes lower than the reset voltage and drops to zero voltage, and the electrical contact RY21 is disconnected.

[0073] Similarly, when the control unit 136 turns on the switch element Q22 while the switch element M20 is turned on, the power supply voltage VBB is applied to the resistor R22. In this case, the switch element M22 is turned on, and the coil DCR-G2 is electrically connected to the auxiliary battery 138. As a result, the applied voltage V22 rises to the power supply voltage VBB. As a result, the electrical contact RY22 is closed. Thereafter, when the control unit 136 turns off both the switch elements Q20 and Q22, the applied voltage V22 drops to zero voltage, and the electrical contact RY22 is opened.

[0074] Similarly, if the control unit 136 turns on the switch element Q23 while the switch element M20 is turned on, the power supply voltage VBB is applied to the resistor R23. In this case, the switch element M23 is turned on, and the coil DCR-P2 is electrically connected to the auxiliary battery 138. As a result, the applied voltage V23 rises to the power supply voltage VBB. As a result, the electric contact RY23 is closed. Thereafter, if the control unit 136 turns off both the switch elements Q20 and Q23, the applied voltage V23 drops to zero voltage, and the electric contact RY23 is disconnected. If the electric contacts RY21 and RY23 are closed before the start of DC charging, the capacitor 155 is pre-charged. After the pre-charging of the capacitor 155 is completed, if the electric contact RY22 is closed and the electric contact RY23 is disconnected, the DC charging starts.

[0075] The control unit 136 performs the same voltage control as the control unit 126 in the embodiment on each of the electric contacts RY21 and RY22. This point will be described in detail below.

[0076] Figure 6 This is a timing chart for specifically explaining the transition of applied voltages V21, V22, and V23 in this modification. The figure shows, from the top, the on / off state of switching elements Q20 to Q23, the applied voltages V21 to V23, and the open / closed state of electrical contacts RY21 to RY23.

[0077] Reference Figure 6 At time t11 after time t10, the exchange of the aforementioned advance information begins, and the control unit 136 turns on the switch elements Q20, Q21, and Q23. As a result, the switch elements M20, M21, and M23 are turned on. As a result, the coils DCR-B2 and DCR-P2 are electrically connected to the auxiliary battery 138, and the applied voltages V21 and V23 rise from zero voltage to the power supply voltage VBB. As a result, the electrical contacts RY21 and RY23 are closed. During the period TPP (time t11 to time t12), these contacts are still in a closed state, and the capacitor 155 is precharged.

[0078] At time t12, voltage VH reaches a predetermined threshold voltage, and precharging of capacitor 155 is completed. Control unit 136 turns on switch element Q22 and turns off switch element Q23. As a result, switch element M22 is turned on, while switch element M23 is no longer turned on. As a result, coil DCR-G2 is connected to auxiliary battery 138, and coil DCR-P2 is electrically disconnected from auxiliary battery 138. As a result, applied voltage V22 rises from zero voltage to power supply voltage VBB, and applied voltage V23 drops from power supply voltage VBB to zero voltage. As a result, electrical contact RY22 is closed, and electrical contact RY23 is opened.

[0079] At time t13, when DC charging starts, the control unit 136 controls the voltage generating unit 134 to generate the applied voltages V21 and V22 in such a manner that the applied voltages V21 and V22 are respectively reduced and maintained at the step-down voltage VCC. In a specific example, the control unit 136 turns off the switching element Q20. As a result, the connection destinations of the coils DCR-B2 and DCR-G2 are respectively switched from the auxiliary battery 138 to the output terminal Te12 of the step-down converter 139. As a result, the applied voltages V11 and V12 are reduced from the power supply voltage VBB to the step-down voltage VCC. During the period TP2 (time t13 to time t18), these applied voltages are respectively maintained at the step-down voltage VCC, so the electrical contacts RY21 and RY22 are still in a closed state. As a result, during the period TP2, the power consumption in the coils DCR-B2 and DCR-G2 (the power consumption of the auxiliary battery 138) can be reduced while these electrical contacts are maintained in a closed state.

[0080] At time t18, the control unit 136 turns off the switching elements Q21 and Q22. As a result, the coils DCR-B2 and DCR-G2 are electrically disconnected from the step-down converter 139, and the applied voltages V21 and V22 drop from the step-down voltage VCC to zero voltage. As a result, the electrical contacts RY21 and RY22 are disconnected.

[0081] As described below, the control unit 136 may control the voltage generating unit 134 in a manner that the applied voltages V21 and V23 are respectively reduced from the power supply voltage VBB to the step-down voltage VCC and maintained at the step-down voltage VCC during the period TPP (applied voltage control during the pre-charging period). Specifically, the control unit 136 may also turn off the switching element Q20 in the state where the switching element M10 is turned on during the period TPP. As a result, the connection destinations of the coils DCR-B2 and DCR-P2 are respectively switched from the auxiliary battery 138 to the output terminal Te12 of the step-down converter 139, and the applied voltages V21 and V23 are respectively reduced to the step-down voltage VCC.

[0082] After that, the control unit 136 turns on the switch element M10 again by turning on the switch element Q20 immediately before the time t12 (before the reference time). As a result, the connection destinations of the coils DCR-B2 and DCR-P2 are switched from the output terminal Te12 to the auxiliary battery 138 again, and the applied voltages V21 and V23 are increased from the step-down voltage VCC to the power supply voltage VBB again. After the time t12 arrives, the control unit 136 performs the control of the switch elements Q20 to Q23 after the time t12 described above.

[0083] By forming such a structure, the power consumption of the coils DCR-B2 and DCR-P2 can be reduced while the electric contacts RY21 and RY23 are maintained in the closed state during the period TPP. The longer the length of the period TPP is (or the longer the period during which the applied voltages V21 and V23 are maintained at the step-down voltage VCC), the more effective the above-mentioned applied voltage control is. Therefore, the control unit 136 may also perform the above-mentioned applied voltage control when the length of the period TPP is longer than the predetermined threshold time.

[0084] As described above, according to this modification, it is possible to reduce the power consumption of auxiliary battery 138 when driving electric contacts RY21 , RY22 , RY23 of relay circuit 115 for DC charging or the like.

[0085] The embodiments disclosed this time should be considered as illustrative in all aspects and not restrictive. The scope of the present invention is indicated by the claims rather than the above description, and is intended to include all modifications within the meaning and scope equivalent to the claims.

Claims

1. A relay circuit comprising: A contact relay comprising an electrical contact and a coil driving the electrical contact; and A voltage generating circuit is connected to the coil and generates a voltage to be applied to the coil. If the applied voltage exceeds the first voltage, the electrical contact is closed. If the applied voltage becomes lower than a second voltage lower than the first voltage, the electrical contact is disconnected. The voltage generating circuit generates the applied voltage so as to exceed the first voltage to close the electrical contact, and then generates the applied voltage so as to decrease and maintain the applied voltage at a third voltage that is lower than the first voltage and higher than the second voltage.

2. The relay circuit according to claim 1, The voltage generating circuit comprises: A power supply node generating a power supply voltage higher than the first voltage; and a converter having an input terminal connected to the power supply node, converting the power supply voltage into the third voltage and outputting the third voltage, The voltage generating circuit is configured such that after the power supply node is connected to the coil, the output terminal of the converter is connected to the coil instead of the power supply node.

3. A vehicle having: The relay circuit according to claim 1 or 2; and A socket capable of being connected to an electric device disposed outside the vehicle, The contact relay is connected to a power line connected to the socket.

4. A vehicle having: The relay circuit according to claim 1 or 2; a power storage device for storing electric power for traveling of the vehicle; and A driving device generates a driving force for the vehicle. The contact relay is provided on a circuit between the power storage device and the drive device.

5. The vehicle according to claim 4, The vehicle is configured to be capable of transmitting electric power between an electric device external to the vehicle and the vehicle, The vehicle further includes a capacitor connected between a first high potential side power line and a first low potential side power line respectively connected to the drive device. The contact relay includes a first contact relay, a second contact relay and a third contact relay. The first contact relay includes a first contact as the electric contact point connected between a second high potential side power line connected to the positive electrode of the power storage device and the first high potential side power line, and a first coil driving the first contact. The second contact relay includes a second contact as the electric contact point connected between a second low potential side power line connected to the negative electrode of the power storage device and the first low potential side power line, and a second coil driving the second contact. The third contact relay includes a third contact connected to the electric contact of the second low potential side power line as a resistance element for precharging the capacitor and a third coil for driving the third contact. The voltage generating circuit generates a first applied voltage as the applied voltage to the first coil, a second applied voltage as the applied voltage to the second coil, and a third applied voltage as the applied voltage to the third coil. If the first contact and the third contact are closed before the start of the power transmission, the capacitor is pre-charged. If the second contact is closed and the third contact is opened after the pre-charging of the capacitor is completed, the power transmission starts. In precharging the capacitor, the voltage generating circuit generates the first applied voltage and the third applied voltage in such a manner that the first applied voltage and the third applied voltage are respectively decreased and maintained at the third voltage. When the power transmission starts, the voltage generation circuit generates the first applied voltage and the second applied voltage so that the first applied voltage and the second applied voltage are respectively decreased and maintained at the third voltage.

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