Patent Publication Number: US-2023150366-A1

Title: Power Supply Control Method and Power Supply Control Device

Description:
TECHNICAL FIELD 
     The present invention relates to a power supply control method and a power supply control device. 
     BACKGROUND 
     An invention for controlling a power supply mode of an electric vehicle is conventionally known (Japanese Unexamined Patent Application Publication No. 2018-98844). In the invention disclosed in Japanese Unexamined Patent Application Publication No. 2018-98844, when an electrical component mounted in the electric vehicle is in operation, the power supply mode is kept on even after charging to a driving battery is stopped. 
     SUMMARY 
     There is a method for changing a state in which a high-power battery and a low-power battery are not connected to a state in which the high-power battery and the low-power battery are connected (what is referred to as a high-power state) by using an event (for example, signal reception) other than a switch operation as a trigger. According to such a method, the state can be changed to the high-power state relatively easily. 
     However, if such a method is adopted, it is assumed that even if the high-power state is released, the state easily changes to the high-power state again. Therefore, it is necessary to prevent the state from changing to the high-power state again after the high-power state is released. However, the invention disclosed in Japanese Unexamined Patent Application Publication No. 2018-98844 does not disclose anything in relation to this point. 
     The present invention has been devised in view of the above described problems, and an object of the present invention is to provide a power supply control method and a power supply control device capable of preventing a state from changing to a high-power state again after the high-power state is released. 
     A power supply control method according to one aspect of the present invention includes: when a power supply state is a state in which power is supplied from a high-power battery to a low-power battery with the relay therebetween, if the controller receives a first signal, switching the relay from an on state to an off state and then inhibiting the relay from switching from the off state to the on state by means of the controller. 
     According to the present invention, it is possible to prevent a state from changing to a high-power state again after the high-power state is released. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a block diagram of a power supply control device  100  according to an embodiment of the present invention; 
         FIG.  2    is a diagram for explaining a power supply position according to an embodiment of the present invention; 
         FIG.  3    is a diagram for explaining an on/off state of a relay  13  according to an embodiment of the present invention; 
         FIG.  4    is a diagram for explaining energization states in an electric vehicle in each power supply position state; 
         FIG.  5    is a timing chart for explaining an operation example of a power supply control device  100  according to an embodiment of the present invention; 
         FIG.  6    is a timing chart for explaining another operation example of a power supply control device  100  according to an embodiment of the present invention; 
         FIG.  7    is a timing chart for explaining another operation example of a power supply control device  100  according to an embodiment of the present invention; and 
         FIG.  8    is a flowchart for explaining an operation example of a power supply control device  100  according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     An embodiment of the present invention will be described below with reference to the drawings. In the drawings, the same parts are denoted by the same reference numerals and the description thereof is omitted. 
     With reference to  FIG.  1   , a configuration example of a power supply control device  100  mounted in a vehicle will be described. The power supply control device  100  includes a controller  10 , a power supply switch  11 , a high-power battery  12 , a relay  13 , a DCDC converter  14 , a low-power battery  15 , and electrical components  16  as shown in  FIG.  1   . A vehicle in the present embodiment refers to an electric vehicle which uses electricity as an energy source. 
     The controller  10  is an electronic control unit (ECU) having a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), a controller area network (CAN) communication circuit, and the like. The controller  10  controls each function of the electric vehicle. As an example, the controller  10  controls the on/off state of the relay  13  based on received signals (a first signal to a third signal). 
     The power supply switch  11  is a pressing-type switch installed in a vehicle. Although the installation position of the power supply switch  11  is not particularly limited, the power supply switch  11  is usually installed at a position where a user sitting on the driver&#39;s seat can easily operate the power supply switch  11 . As an example, the power supply switch  11  is positioned near the steering wheel. Each time the user presses the power supply switch  11 , the state of the power supply is switched. This kind of power supply state is referred to as a “power supply position” in the present embodiment. Details of the power supply position will be described later. The power supply switch  11  has an on/off indicator. 
     The high-power battery  12  is a driving battery used mainly as a power supply of a motor (not shown). The high-power battery  12  is a large-capacity secondary battery composed of a plurality of battery modules. An external power supply  30  is used for charging the high-power battery  12 . The user charges the high-power battery  12  by connecting the external power supply  30  and the electric vehicle by using a dedicated charging cable. 
     The low-power battery  15  is used as a power supply of the electrical components  16  mounted in a vehicle. As an example, the low-power battery  15  is a lead-acid battery that stores power at a voltage in the range from 12 V to 15 V. Examples of the electrical components  16  to which the low-power battery  15  supplies power include a navigation device, an audio device, and the like. 
     The relay  13  and the DCDC converter  14  are connected between the high-power battery  12  and the low-power battery  15 . The low-power battery  15  is electrically connected to the high-power battery  12  by means of the relay  13 . The on/off state of the relay  13  is controlled by means of the controller  10 . If the power supply switch  11  is not turned off, the relay  13  is usually turned on. The DCDC converter  14  drops the power of the high-power battery  12  and supplies the power to the low-power battery  15 . Although  FIG.  1    shows the electrical components  16  and the DCDC converter  14  separately, the DCDC converter  14  is also a type of the electrical components  16 . 
     An intelligent key  20  is used for remotely controlling unlocking and locking of the door. If a user presses an unlocking switch of the intelligent key  20 , all doors of the electric vehicle are unlocked. However, the function of the intelligent key  20  is not limited to this. The door is unlocked even if the user presses a switch attached to a door handle or a trunk. Briefly explaining the system, both of the electric vehicle and the intelligent key  20  have an antenna for transmitting radio waves and a receiver for receiving radio waves. If the user presses a switch attached to the door handle or the trunk, a radio wave is transmitted from the antenna of the electric vehicle. The intelligent key  20  that has received the radio wave automatically returns the radio wave. When the receiver of the electric vehicle receives this radio wave, the door is unlocked. The intelligent key  20  may be referred to as a smart key. 
     The first signal shown in  FIG.  1    is transmitted from the power supply switch  11  to the controller  10 . The second signal is transmitted to the controller  10  if the external power supply  30  and the electric vehicle are connected by using a dedicated charging cable. The third signal is transmitted from the intelligent key  20  to the controller  10 . After receiving the first to third signals, the controller  10  controls the on/off state of the relay  13  in accordance with the received signals. 
     Next, the power supply position will be described with reference to  FIG.  2   . 
     In the present embodiment, as shown in  FIG.  2   , the power supply position includes four states of power off (a first state), a second state, a third state, and a fourth state. Although the power supply position additionally includes a fifth state, the first to fourth states will be described here, and the fifth state will be described later. 
     Power off means a state in which the power supply switch  11  is turned off. When the power supply position is power off, all devices other than some devices do not operate. Some functions are door locks (including unlocks), communication devices, and security devices. In addition, even if the power supply position is power off, a minute current (what is referred to as a dark current) flows through the electrical components  16  to back up the functions. This dark current is supplied from the low-power battery  15 . When the power supply position is power off, the indicator of the power supply switch  11  is turned off. 
     The second state is a state in which the power supply switch  11  is turned on and the indicator of the power supply switch  11  is turned on. When the power supply position is in the second state, the relay  13  is turned on, and power is supplied from the high-power battery  12  to the low-power battery  15  with the relay  13  therebetween. More specifically, by the relay  13  being turned on when the power supply position is in the second state, power is supplied from the high-power battery  12  to the low-power battery  15  with the DCDC converter  14  therebetween. In the second state, the user can use many electrical components  16  except for some electrical components. Specifically, in the second state, the user can set a route by operating the navigation device and listen to the radio by operating the audio device. 
     In the second state, a meter and a blower motor do not operate. This is because, if a predetermined time (for example, about 1 to 10 minutes) elapses during which no operation is performed by the user in the second state, the power supply position automatically changes from the second state to power off. The blower motor is used to send air from an air conditioner into the vehicle interior, and a fan is attached to the blower motor. In this arrangement, if a predetermined time elapses during which no operation is performed by the user, the blower motor stops and the air blowing stops, that is, the air conditioner is turned off. If the air conditioner is automatically turned off, the user may feel dissatisfied. Therefore, the blower motor does not operate in the second state. The meter is an electrical component for providing various pieces of information to the user. Therefore, the user may feel an inconvenience if the meter is automatically turned off. Therefore, the meter does not operate in the second state. The absence of user operation means the absence of an input from the user to the electrical components  16 . The second state may be referred to as AUTOACC. 
     In the third state, as in the second state, the power supply switch  11  is turned on and the indicator of the power supply switch  11  is turned on. When the power supply position is in the third state, as in the second state, the relay  13  is turned on and power is supplied from the high-power battery  12  to the low-power battery  15  with the relay  13  therebetween. The third state differs from the second state in that, while in the second state, the meter and the blower motor do not operate, in the third state, all electrical components including the meter and the blower motor operate. The third state may be referred to as IGN-ON. 
     Next, the change of the power supply position will be described. As shown in  FIG.  2   , each time the user presses the power supply switch  11 , the power supply position changes to power off (the first state), the second state, and the third state in this order. Suppose that the user presses the power supply switch  11  when the power supply position is in the third state. In the above case, the power supply position changes to the second state. Suppose that a predetermined time elapses during which no operation is performed by the user as described above when the power supply position is in the second state. In the above case, the power supply position automatically changes to power off. Here, means for changing power off to the second state is not limited to the operation of the power supply switch  11 . Even when the user presses the unlocking switch of the intelligent key  20 , the power supply position changes from power off to the second state. More specifically, suppose that the user presses the unlocking switch of the intelligent key  20  possessed by the user before the user gets on the electric vehicle. In the above case, the third signal is transmitted from the intelligent key  20  to the controller  10  (see  FIG.  1   ). The controller  10  that has received the third signal changes the power supply position from power off to the second state. This enables the user to use the navigation device, the audio device, and the like immediately after getting on the vehicle. Meanwhile, in the second state of the present embodiment, the time required for supplying power from the low-power battery  15  to the electrical components  16  becomes long, and state of charge (SOC) of the battery may decrease. Therefore, as described above, in the second state, the controller  10  turns on the relay  13  and causes power to be suppled from the high-power battery  12  to the low-power battery  15  with the relay  13  therebetween. This prevents reduction in the SOC of the low-power battery  15  even if the time required for supplying power from the low-power battery  15  to the electrical components  16  is increased. 
     In this way, supplying power from the high-power battery  12  to the low-power battery  15  with the relay  13  therebetween in the second state (also in the third state) of the present embodiment can be rephrased as a requirement from the power system side. The requirement from the power system side will be simply referred to as a “system request” below. 
     As shown in  FIG.  2   , when the power supply position is power off, in the second state, or in the third state, travelling of the electric vehicle is not possible. To enable travelling of the electric vehicle, the user needs to perform a predetermined operation. The predetermined operation means, as an example, an operation of pressing the power supply switch  11  while depressing a brake pedal. This operation can be performed even if the power supply position is in any one of power off, the second state, and the third state. 
     Suppose that the user presses the power supply switch  11  while depressing the brake pedal. In the above case, the power supply position changes to a fourth state from power off, the second state, or the third state as shown in  FIG.  2   . The electric vehicle can travel in the fourth state. Further, in the fourth state, the power supply switch  11  is turned on, and the indicator of the power supply switch  11  is turned on. In the fourth state, the relay  13  is turned on, and power is supplied from the high-power battery  12  to the low-power battery  15  with the relay  13  therebetween. In the fourth state, as in the third state, all electrical components including the meter and the blower motor are operated. In the fourth state, the meter displays an icon showing that the vehicle can travel. If the user presses the power supply switch  11  after travelling of the vehicle is completed, the power supply position changes from the fourth state to the second state as shown in  FIG.  2   . This is because there is a need for the user to use the audio device and the like even after the travelling of the vehicle is completed. The fourth state may be referred to as READY-ON. 
     Hereinafter, a state in which power is supplied from the high-power battery  12  to the low-power battery  15  with the relay  13  therebetween may be referred to as a “high-power state”. The second, third, and fourth states shown in  FIG.  2    are high-power states. 
     Next, the on/off state of the relay  13  will be described with reference to  FIG.  3   . 
     The table shown in  FIG.  3    shows how the on/off state of the relay  13  is controlled depending on the power supply position. 
     As shown in  FIG.  3   , when the power supply position is power off, the relay  13  is normally turned off. When the power supply position is in the second state, the relay  13  is normally turned on. When the power supply position is in the third state, the relay  13  is normally turned on. When the power supply position is in the fourth state, the relay  13  is normally turned on. 
     Suppose that the power supply position is in the second state and the power supply switch  11  is pressed for a predetermined time (for example, 2 seconds) or longer. In the above case, the controller  10  switches the relay  13  from the on state to the off state as shown in  FIG.  3   . More specifically, when the power supply switch  11  is pressed for a predetermined time or longer, the first signal (see  FIG.  1   ) is transmitted from the power supply switch  11  to the controller  10 . The controller  10  that has received the first signal switches the relay  13  from the on state to the off state. As a result, the low-power battery  15  is disconnected from the high-power battery  12 , and power supply from the high-power battery  12  is stopped. This releases the high-power state. 
     One of the reasons why the high-power state is released when the power supply switch  11  is pressed for a predetermined time or longer in this way is to cope with an unexpected event. When an unexpected event occurs and rescue is required, a prompt release of the high-power state is required. Therefore, the controller  10  of the present embodiment switches the relay  13  from the on state to the off state upon receiving the first signal. The first signal is transmitted by means of pressing and holding (for example, 2 seconds or longer) of the power supply switch  11 . Therefore, according to the present embodiment, the high-power state can be easily and promptly released. The above described predetermined time is not limited to 2 seconds and can be changed appropriately. 
     Even when the power supply position is in the third state, as in the second state, the controller  10  switches the relay  13  from the on state to the off state when the user presses and holds the power supply switch  11  for a predetermined time or longer. 
     The first signal is transmitted from the power supply switch  11  only when the power supply position is in the second state or the third state. In other words, when the power supply position is power off or in the fourth state, even if the power supply switch  11  is pressed for a predetermined time or longer, the first signal is not transmitted from the power supply switch  11 . Therefore, the state of the relay  13  does not change as shown in  FIG.  3    when the power supply position is power off or in the fourth state, even if the power supply switch  11  is pressed for a predetermined time or longer. 
     In addition to the rescue described above, the release of the high-power state is required for work in a factory, software update work of the controller mainly related to high power, and the like. In such work also, the prompt release of the high-power state is required as in the rescue. According to the present embodiment, the high-power state can be released only by pressing and holding the power supply switch  11 . This realizes the easy and prompt release of the high-power state, and the smooth performance of the work in the factory, the software update work of the controller mainly related to high power, and the like. In the present embodiment, even in a state in which the high-power state is released (the second state and the third state), power is supplied from the low-power battery  15  to the electrical components  16 . 
     Next, with reference to  FIG.  4   , the energization states in the electric vehicle in each power supply position state will be described. 
     The table in  FIG.  4    shows the energization states of the door locks, the communication device, the security device, the dark current, the electrical components  16 , and an EV system as energization states in the electric vehicle. The electrical components  16  are classified into the navigation device, the audio device, the meter, the blower motor, a power window, and the DCDC converter  14 . Further, the EV system is also classified into a heater, a compressor, and an inverter. The heater is used to heat the high-power battery  12 . 
     From the low-power battery  15 , power is supplied to the navigation device, the audio device, the meter, the blower motor, the power window, and the DCDC converter  14 . From the high-power battery  12 , power is supplied to the heater, the compressor, and the inverter. 
     As shown in  FIG.  4   , the power supply position is classified into power off (the first state), the second state, the third state, the fourth state, and a fifth state. Power off, the second state, the third state, and the fourth state have already been described above. Suppose that the power supply switch  11  is pressed and held for a predetermined time or longer when the power supply position is in the second or third state. In the above case, this kind of power supply position changes to the fifth state. 
     As shown in  FIG.  4   , when the power supply position is power off, power is supplied from the low-power battery  15  to the door locks (including unlocking), the communication device, and the security device. Meanwhile, power is not supplied to the electrical components  16  from the low-power battery  15 . Similarly, power is not supplied to the EV system from the high-power battery  12 . However, a minute current (what is referred to as a dark current) flows through the electrical components  16  to back up the functions. In the first to fifth states, the energization states of the door locks, the communication device, the security device, and the dark current are the same, and therefore the description thereof is omitted. 
     When the power supply position is in the second state, from the low-power battery  15 , power is supplied to the navigation device, the audio device, the power window, and the DCDC converter  14  as shown in  FIG.  4   . Further, when the power supply position is in the second state, since the second state is the high-power state as described above, from the high-power battery  12 , power is supplied to the heater, the compressor, and the inverter. When the power supply position is in the second state, power is not supplied to the meter and the blower motor from the low-power battery  15 . This is because, as described above, in the second state, a mechanism (what is referred to as a time limit) is set in which under a predetermined condition, the second state automatically changes to power off. As described above, if the air conditioner is automatically turned off, the user may feel dissatisfied. Since the meter is an electrical component for providing various pieces of information to the user, the user may feel an inconvenience if the meter is automatically turned off. Therefore, power is not supplied to the meter and the blower motor from the low-power battery  15  in the second state. 
     When the power supply position is in the third state, power is supplied to all the devices shown in  FIG.  4   . Unlike the second state, the third state has no time limit. In other words, even if a predetermined time elapses during which no operation is performed by the user in the third state, the power supply position does not automatically change from the third state to power off. 
     When the power supply position is in the fourth state, power is supplied to all the devices shown in  FIG.  4   . 
     When the power supply position is in the fifth state, the high-power state is released as described above, and therefore no power is supplied from the high-power battery  12  to the heater, the compressor, and the inverter as shown in  FIG.  4   . 
     Here, the change from the third state to the fifth state is supplemented. As described above, suppose that the power supply position is in the third state and the power supply switch  11  is pressed and held for a predetermined time or longer. In the above case, the power supply position changes to the fifth state. At this time, when the power supply switch  11  is pressed, the power supply position first changes to the second state. When the power supply switch  11  is continuously pressed and held for a predetermined time or longer, the power supply position changes to the fifth state. As described above, the high-power state can be released by means of the same operation (pressing and holding the power supply switch  11 ) even if the power supply position is in either the second state or the third state. Therefore, it is possible to prevent the operation from becoming complicated as compared with the case where the operation is differentiated depending on the state of the power supply position. 
     Next, an operation example of the power supply control device  100  will be described with reference to the timing chart of  FIG.  5   . 
     The initial state (time: 0) in  FIG.  5    indicates the second state. That is, the timing chart shown in  FIG.  5    starts from a scene in which the controller  10  receives the third signal (see  FIG.  1   ) and changes the power supply position from power off to the second state. 
     Since the power supply position is in the second state in the initial state of  FIG.  5   , the system request is on. The system request being on means a request for the high-power state. Since the system request is on, the controller  10  turns on the relay  13  and supplies power from the high-power battery  12  to the low-power battery  15  with the relay  13  therebetween. 
     Here, it is assumed that the power supply switch  11  is pressed and held at time T 1  in  FIG.  5   . Examples of persons who may press and hold the power supply switch  11  are assumed to include the user of the electric vehicle, a rescue member, a worker in a factory, a dealer, and the like. When the power supply switch  11  is pressed and held, a timer (one of the functions of the controller  10 ) is activated, and the time during which the power supply switch  11  is pressed and held is measured. 
     When the time during which the power supply switch  11  is pressed and held is a threshold value or longer (time T 2 ), the controller  10  switches the relay  13  from the on state to the off state. As a result, the low-power battery  15  is disconnected from the high-power battery  12 , and power supply from the high-power battery  12  is stopped. This releases the high-power state. At time T 2 , the power supply position changes from the second state to the fifth state. Note that the threshold value used here has the same meaning as the predetermined time described above. 
     At time T 2 , the controller  10  switches the relay  13  from the on state to the off state and switches an inhibition flag from 0 to 1. The inhibition flag is a flag used to inhibit the controller  10  switching the relay  13  from the off state to the on state. When the inhibition flag is set to 0, the controller  10  can switch the relay  13  from the off state to the on state. Meanwhile, when the inhibition flag is set to 1, the controller  10  may not switch the relay  13  from the off state to the on state. 
     Here, the purpose of setting the inhibition flag will be described. As described above, in the present embodiment, in order to promptly release the high-power state, when the power supply switch  11  is pressed and held for a predetermined time or longer, the controller  10  switches the relay  13  from the on state to the off state. After the the relay  13  is switched from the on state to the off state, if the user presses the unlocking switch of the intelligent key  20  again, for example, the controller  10  switches the relay  13  from the off state to the on state again. This changes the state again to the high-power state. Therefore, it is necessary to prevent the state from changing to the high-power state again after the high-power state is released. 
     Therefore, in the present embodiment, when the power supply switch  11  is pressed and held for a predetermined time or longer, the inhibition flag is switched from 0 to 1. This prevents the state from changing to the high-power state again even if the user presses the unlocking switch of the intelligent key  20  again after the high-power state is released. 
     As shown in  FIG.  6   , if the time during which the power supply switch  11  is pressed and held (1.5 seconds) is shorter than the threshold value, the controller  10  does not switch the relay  13  from the on state to the off state. Further, the controller  10  does not switch the inhibition flag from 0 to 1. 
     Next, another operation example of the power supply control device  100  will be described with reference to the timing chart of  FIG.  7   . 
     The initial state (time: 0) in  FIG.  7    shows a state after the inhibition flag is switched from 0 to 1. That is, the timing chart shown in  FIG.  7    starts from a state after the time T 2  in  FIG.  5   . 
     In the initial state of  FIG.  7   , the high-power state is released and the power supply position is in the fifth state. The electrical components  16  operate even when the power supply position is in the fifth state. Therefore, the system request remains on. When another request is on at time T 3  in  FIG.  7   , the controller  10  switches the inhibition flag from 1 to 0 and switches the relay  13  from the off state to the on state. In the above description, it has been explained that when the power supply switch  11  is pressed and held for a predetermined time or longer, the controller  10  releases the high-power state and prevents the state from changing to the high-power state again. Here, suppose that the cause of releasing the high-power state (rescue, work in a factory, software update work, or the like) is solved. In the above case, it is necessary to return the state to the high-power state again depending on the situation. Examples of the above case include the case of charging the high-power battery  12 , the case of making the electric vehicle travel, and the like, for example. When the high-power battery  12  is charged, in order to charge the low-power battery  15  at the same time, it is necessary to return to the state to the high-power state. When the electric vehicle is made to travel, it is necessary to return the state to the high-power state in order to prevent the reduction in the SOC of the low-power battery. 
     Examples of another request at time T 3  in  FIG.  7    include a request for charging the high-power battery  12 , a request for making the electric vehicle travel, and the like. Another request being on means the case where the second signal (see  FIG.  1   ) indicating the start of charging of the high-power battery  12  is transmitted to the controller  10 , or means the case where a signal is transmitted to the controller  10 , the signal indicating that the user has pressed the power supply switch  11  while depressing the brake pedal. This other request is different from the system request. 
     Further, this other request may be a request for controlling an air conditioning device mounted in the electric vehicle. In this case, information that another request is on means the case where a signal for controlling the air conditioning device is transmitted to the controller  10 . The signal for controlling the air conditioning device may be a signal for controlling the air conditioner (remote control or timer control) by the user operating the smartphone, or a signal for heating or cooling the high-power battery  12 . 
     When another request different from the system request is on in this way, the controller  10  switches the inhibition flag from 1 to 0 and switches the relay  13  from the off state to the on state. Accordingly, even after the high-power state is released and the change from the state to the high-power state again is prevented, the state can be returned to the high-power state again. 
     In the examples shown in  FIGS.  5  to  7   , the case where the power supply position is in the second state has been described, but the same applies to the case where the power supply position is in the third state. 
     Next, an operation example of the power supply control device  100  will be described with reference to the flowchart of  FIG.  8   . 
     In step S 101 , when the user presses the unlocking switch of the intelligent key  20 , the third signal is transmitted from the intelligent key  20  to the controller  10  (see  FIG.  1   ). The process proceeds to step S 103 , and in step S 103 , the controller  10  that has received the third signal changes the power supply position from power off (the first state) to the second state (see  FIG.  2   ). This enables the user to use the navigation device and the like immediately after getting on the vehicle. In the second state, the relay  13  is turned on, and power is supplied from the high-power battery  12  to the low-power battery  15  with the relay  13  therebetween. 
     If the power supply switch  11  is pressed and held for a predetermined time or longer (YES in step S 105 ), the process proceeds to step S 107 , and in step S 107 , the controller  10  switches the relay  13  from the on state to the off state. This disconnects the low-power battery  15  from the high-power battery  12  and stops power supply from the high-power battery  12 . Accordingly, the high-power state is released. Further, the controller  10  switches the inhibition flag from 0 to 1 (step S 109 ). This prevents switching the relay  13  from the off state to the on state, and prevents the state from changing to the high-power state again. If the answer is NO in step S 105 , the process is in a standby state. 
     After the process of step S 109 , suppose that the user connects the external power supply  30  and the electric vehicle by using the dedicated charging cable to start charging the high-power battery  12 . In the above case, the second signal indicating the start of charging the high-power battery  12  is transmitted to the controller  10 . If the controller  10  receives the second signal (YES in step S 111 ), the process proceeds to step S 113 , and the controller  10  switches the inhibition flag from 1 to 0. This enables the controller  10  to switch the relay  13  from the off state to the on state. In step S 115 , the controller  10  switches the relay  13  from the off state to the on state. As described above, according to the present embodiment, it is possible to promptly release the high-power state or to restore the state to the high-power state again depending on the situation. 
     In the example shown in  FIG.  8   , the case where the power supply position changes to the second state in step S 103  has been described. However, the same applies to the case where the power supply position changes to the third state. 
     Functions and Effects 
     As described above, in accordance with the power supply control device  100  according to the present embodiment, it is possible to obtain the following functions and effects. 
     Suppose that the controller  10  receives the first signal (see  FIG.  1   ) when the power supply position is in the second or third state. In the above case, the controller  10  switches the relay  13  from the on state to the off state and then inhibits the relay  13  from switching from the off state to the on state. This prevents the state from changing to the high-power state again even if the user presses the unlocking switch of the intelligent key  20  again after the high-power state is released, for example. 
     Suppose that the controller  10  receives the second signal (see  FIG.  1   ) after inhibiting the relay  13  from switching from the off state to the on state. In the above case, the controller  10  switches the relay  13  from the off state to the on state. This enables returning of the state to the high-power state again even after the high-power state is released and the change from the state to the high-power state again is prevented. 
     The second signal includes at least one of a signal for enabling the electric vehicle to travel, a signal indicating the start of charging of the high-power battery  12 , the signal for controlling the air conditioning device mounted in the electric vehicle, and a signal for preventing the remaining capacity of the low-power battery  15  from decreasing. 
     If the controller  10  receives the third signal from the intelligent key  20 , the controller  10  changes the power supply position from power off to the second state. In other words, if the controller  10  receives the third signal from the intelligent key  20 , the controller  10  changes a state in which a power supply is turned off (a non-high-power state) to a state in which power is supplied from the high-power battery  12  to the low-power battery  15  with the relay  13  therebetween (the high-power state). That is, in the present embodiment, the non-high-power state is easily changed to the high-power state. Therefore, suppose that the controller  10  switches the relay  13  from the on state to the off state due to the user pressing and holding the power supply switch  11 . In the above case, the controller  10  sets an inhibition flag such that the relay  13  is not switched from the off state to the on state again even if the controller  10  receives the third signal after performing the switching. This prevents the state from changing to the high-power state again even if the user presses the unlocking switch of the intelligent key  20  again after the high-power state is released, for example. 
     Each function described in the above embodiment may be implemented by means of one or more processing circuits. The processing circuit includes a programmed processing device such as a processing device including an electrical circuit. The processing circuitry also includes devices such as application specific integrated circuits (ASICs) and circuit components that are arranged to perform the described functions. 
     As described above, although an embodiment of the present invention has been described, it should not be understood that the arguments and drawings forming part of this disclosure are intended to limit the present invention. Various alternative embodiments, examples, and operational techniques will be apparent to those skilled in the art from this disclosure. 
     REFERENCE SIGNS LIST 
     
         
           100  Power supply control device 
           10  Controller 
           11  Power supply switch 
           12  High-power battery 
           13  Relay 
           14  DCDC converter 
           15  Low-power battery 
           16  Electrical component 
           20  Intelligent key 
           30  External power supply