VEHICLE AND VEHICLE TAX PROCEDURES

Abstract

Vehicle (1) which features: a first step-down converter (71, 33) which performs step-down converter operation such that a first target voltage is generated and outputs a reduced electrical energy to a power line (PL2, PL3); a second step-down converter (61, 72) which performs step-down converter operation in such a way that a second target voltage is generated and outputs a reduced electrical energy to the power line (PL2, PL3); an auxiliary battery (5) which is charged with electrical energy transmitted via the power line (PL2, PL3); a control unit (100) that outputs the first target voltage to the first step-down converter (71, 33) and the second target voltage to the second step-down converter (61, 72); a cooling system (93, 91); and Equipment (7, 3) which is cooled by the cooling system (93, 91), wherein the first down converter (71, 33) is arranged inside the equipment (7, 3), the second down converter (61, 72) is arranged outside the equipment (7, 3), and the control unit (100) sets the first target voltage higher than the second target voltage when the control unit (100) initiates the operation of the equipment (7, 3).

Description

Technical area

[0001] The present invention relates to a vehicle and a vehicle control method, and more particularly to a vehicle having an auxiliary battery and a method for controlling the same. State of the art

[0002] Generally, an auxiliary battery is installed on a vehicle. The electrical energy stored in the auxiliary battery gradually decreases. Therefore, it is necessary to charge the auxiliary battery appropriately. A vehicle configuration with multiple buck converters can be used.

[0003] In addition, due to growing environmental awareness in recent years, a fuel cell vehicle (FCV), as disclosed in WO 2011 / 004 493 A1, has been developed.

[0004] US 2018 / 0 229 771 A1, US 2019 / 0 143 822 A1 and CN 1 12 248 826 A each teach a vehicle with at least two step-down converters, an auxiliary battery, a control unit and cooling systems for equipment. CN 1 12 248 826 A discloses a corresponding vehicle with four step-down converters, an auxiliary battery, a control unit, a traction motor including the associated energy converter, a charging unit and a cooling system. DE 10 2013 207 099 A1 shows, among other things, an example of a "typical" converter, as is also the case in Fig. 2 of the present invention. Summary of the invention

[0005] A configuration is assumed in which two buck converters are provided for charging an auxiliary battery. These buck converters are referred to as the first buck converter and the second buck converter. It is also contemplated that the first buck converter and the second buck converter are caused to perform buck converter operation simultaneously to charge an auxiliary battery. However, the inventor focused on the fact that an efficient situation from the point of view of the vehicle's energy consumption can occur in a specific vehicle configuration (described below) by using one buck converter, the first or second buck converter, as the main buck converter and the other as the sub-buck converter, instead of using both converters, the first and second buck converter, to a comparable extent (without distinguishing them as main / sub-converters).

[0006] The present invention has been made to solve the above problem, and an object of the present invention is to improve the energy utilization efficiency of a vehicle in a vehicle configuration capable of charging an auxiliary battery by either the first buck converter or the second buck converter. (1) A vehicle according to a specific aspect of the present invention includes: a first buck converter; a second buck converter; an auxiliary battery charged with electric power transmitted via a power line; a control unit that outputs a first target voltage to the first buck converter and a second target voltage to the second buck converter; a cooling system; and equipment cooled by the cooling system. The first buck converter is disposed inside the equipment, performs a buck-conversion operation to generate the first target voltage, and outputs a stepped-down electric power to the power line. The second buck converter is disposed outside the equipment, performs a buck-conversion operation to generate the second target voltage, and outputs a stepped-down electric power to the power line.The control unit sets the first target voltage higher than the second target voltage when the control unit causes the equipment to operate. (2) The vehicle also has a traction motor. The equipment is an energy converter that drives the traction motor. (3) The vehicle further comprises an energy storage device. The equipment is a charging unit that charges the energy storage device with electrical energy supplied from outside the vehicle. (4) When an output current of the first buck converter is less than a maximum output current of the first buck converter, the control unit prevents the second buck converter from outputting a degraded electric power to the power line, with the first target voltage set higher than the second target voltage. When the output current of the first buck converter is greater than the maximum output current, the control unit causes the first buck converter and the second buck converter to output a degraded electric power to the power line, with the first target voltage set higher than the second target voltage.

[0007] As described in more detail below, when the first target voltage is set higher than the second target voltage, the buck converter operation of the second buck converter can be stopped while an output current of the first buck converter is in a range smaller than the maximum output current of the first buck converter. The first buck converter, which is arranged inside the equipment cooled by the cooling system (a power converter or a charger, etc.), is now used as the main buck converter. Energy loss (heat loss) during the buck converter operation of the first buck converter can be reduced by cooling the first buck converter together with cooling the equipment. Consequently, according to the configurations described in (1) to (4) above, the energy utilization efficiency of the vehicle can be improved. (5) The vehicle further comprises another cooling system that cools the second buck converter. The control unit deactivates the additional cooling system when the output current of the first buck converter is less than the maximum output current of the first buck converter.

[0008] When the output current of the first buck converter is less than the maximum output current of the first buck converter, the second buck converter stops its operation. Therefore, according to the configuration described in (5) above, the energy consumption of the additional cooling system that cools the second buck converter can be saved by stopping the additional cooling system, thereby further improving the energy efficiency of the vehicle. (6) A vehicle according to another aspect of the present invention includes: a traction motor; a power converter that drives the traction motor; an energy storage device; a charging unit that charges the energy storage device with electric power supplied from outside the vehicle; a first cooling system that cools the power converter; a second cooling system that cools the charging unit; a first buck converter; a second buck converter; a third buck converter; a fourth buck converter; an auxiliary battery charged by a buck-converting operation of a buck converter, first to fourth buck converters; and a control unit that outputs the first to fourth target voltages to the first to fourth buck converters, respectively. The first buck converter performs the buck-converting operation so as to generate the first target voltage and outputs a stepped-down electric power to the first power line.The second buck converter performs the buck conversion operation to generate the second target voltage and outputs a stepped-down electrical power to the first power line. The third buck converter performs the buck conversion operation to generate the third target voltage and outputs a stepped-down electrical power to the second power line. The fourth buck converter performs the buck conversion operation to generate the fourth target voltage and outputs a stepped-down electrical power to the second power line. The first buck converter is arranged inside the power converter. The second buck converter is arranged outside the power converter and the charging unit. The third buck converter is arranged inside the charging unit. The fourth buck converter is arranged inside the power converter.The control unit sets the first target voltage higher than the second target voltage when the control unit causes the energy converter to operate, and sets the third target voltage higher than the fourth target voltage when the control unit causes the charging unit to operate.

[0009] The first buck converter and the second buck converter are distinguished as the main buck converter and the sub-buck converter, and the third buck converter and the fourth buck converter are distinguished as the main buck converter and the sub-buck converter. According to the configuration described in (6) above and the configuration described in (1), the energy utilization efficiency of the vehicle can be appropriately improved in response to the vehicle's usage, for example, in a situation where the power converter is operating or the charging unit is operating. (7) In a method for controlling a vehicle according to another aspect of the present invention, the vehicle includes a first buck converter, a second buck converter, an auxiliary battery charged with electric power transmitted through a power line, and equipment cooled by a cooling system. The first buck converter performs a buck conversion operation to generate a first target voltage and outputs a stepped-down electric power to the power line. The second buck converter performs a buck conversion operation to generate the second target voltage and outputs a stepped-down electric power to the power line. The first buck converter is disposed inside the equipment. The second buck converter is disposed outside the equipment.The vehicle control method includes determining whether to operate the equipment; and setting the first target voltage higher than the second target voltage.

[0010] According to the method described in (7) above, as well as with the configuration described in (1), the energy efficiency of the vehicle can be improved. The above and other objects, features, aspects, and advantages of the present invention will become more apparent from the following detailed description of the present invention, which is given with reference to the accompanying drawings. Short description of the characters Fig. 1 is a circuit block diagram schematically showing an overall configuration of a vehicle according to Embodiment 1. Fig. Figure 2 is a diagram showing an example of a circuit structure of a buck converter. Fig. Figure 3 is a diagram illustrating charging control via an auxiliary battery when the vehicle is in the ReadyON state. Fig. Figure 4 is a diagram showing the effects of set voltages in Embodiment 1. Fig. 5 is a flowchart showing the charge control for the auxiliary battery in Embodiment 1. Fig. Figure 6 is a diagram showing a charging control for the auxiliary battery when the vehicle is performing plug-in charging. Fig. 7 is a diagram showing the effects of target voltages in Embodiment 2. Fig. 8 is a flowchart showing charging control for an auxiliary battery in Embodiment 2. Fig. 9 is a flowchart showing a charge control for an auxiliary battery according to a variation. Description of the preferred embodiments

[0011] Embodiments are described below with reference to the accompanying figures. It should be noted that like reference numerals refer to like or corresponding parts, and the description will not be repeated. [Embodiment 1]<Gesamtkonfiguration des Fahrzeugs>

[0012] Fig. Fig. 1 is a circuit block diagram schematically showing an overall configuration of a vehicle according to Embodiment 1. In the present embodiment, Fig. 1, a vehicle 1 is a fuel cell vehicle. Vehicle 1 is also capable of external charging with electrical energy supplied from outside the vehicle 1 (so-called plug-in charging). In other words, vehicle 1 is a plug-in fuel cell vehicle (PFCV). However, it is not absolutely necessary for vehicle 1 to be an FCV. Vehicle 1 can be a typical plug-in hybrid vehicle (PHV), which has an engine instead of a fuel cell.

[0013] The vehicle 1 includes a hydrogen tank 11, a fuel cell (FC) stack 12, a relay 13, a boost converter 14, a direct current (DC) input 21, an alternating current (AC) input 22, charging relays 23, 24, a charging unit 3, a main battery 41, a system main relay (SMR) 42, an auxiliary battery 5, buck converters 61, 62, a power control unit (PCU) 7, a motor generator 81, drive wheels 82, an FC cooling system 91, a charger cooling system 92, a PCU cooling system 93, an air conditioning system 94, an electronic control unit (ECU) 100, and the power lines PL1, PL2, and PL3. The charging unit 3 has an inverter 31, a boost converter 32, and a buck converter 33. PCU 7 has buck converters 71, 72, and an inverter 73.

[0014] The power lines PL1 to PL3 each transmit electrical energy at a specified voltage level (a voltage within a specified voltage range). The voltage levels V1 to V3 of the power lines PL1 to PL3 correspond to the listed order (V1 > V2 > V3). For example, the power line PL1 has a voltage level of V1 = 650 V, the power line PL2 has a voltage level of V2 = 350 V, and the power line PL3 has a voltage level of V3 = 12 V.

[0015] The hydrogen tank 11 stores hydrogen. Although not shown, the vehicle 1 further includes a supply inlet that receives hydrogen from a hydrogen station.

[0016] The FC stack 12 is a structure in which several (e.g., several tens to several hundred) FC cells are stacked in series. The hydrogen stored in the hydrogen tank 11 is pumped to the anode side of the FC stack 12 by a hydrogen pump (not shown). Air is pumped to the cathode side of the FC stack 12 by an air pump (not shown). In this way, the FC stack 12 causes hydrogen and oxygen in the air to undergo an electrochemical reaction, thereby generating electrical energy.

[0017] Relay 13 is electrically connected between FC stack 12 and boost converter 14. Relay 13 is opened / closed according to a control command from ECU 100.

[0018] According to a control command from the ECU 100, the boost converter 14 increases or boosts the voltage of the electrical energy generated by the FC stack 12 to the voltage level V1.

[0019] The DC input 21 and the AC input 22 are each capable of receiving a plug (not shown) of a charging cable extending from a charging device, such as a charging station. The DC input 21 is a charging input for so-called rapid charging, which supplies high-voltage DC power from a charging station. The DC input 21 is electrically connected to the power line PL1 via the charging relay 23. The AC input 22 is a charging input for so-called normal charging, which receives AC power supplied from a charging station. The AC input 22 is electrically connected to the charging unit 3 via the charging relay 24. The charging relays 23, 24 are opened / closed according to a control command from the ECU 100.

[0020] The inverter 31 is electrically connected between the AC input 22 and the boost converter 32, and between the AC input 22 and the buck converter 33. According to a control command from the ECU 100, the inverter 31 converts the AC power supplied from the charging controller via the AC input 22 into DC power and outputs the DC power to the boost converter 32 or buck converter 33.

[0021] The boost converter 32 is electrically connected between the inverter 31 and the power line PL1. According to a control command from the ECU 100, the converter 32 boosts the voltage of the DC power from the inverter 31 and outputs the boosted DC power to the power line PL1.

[0022] The step-down converter 33 is electrically connected between the inverter 31 and the power line PL3. According to a control command from the ECU 100, the step-down converter 33 steps down the voltage of the DC power from the inverter 31 and outputs the stepped-down DC power to the power line PL3.

[0023] The main battery 41 is electrically connected to the power line PL1 via the SMR 42. The main battery 41 includes a battery pack composed of multiple cells (e.g., 200 cells are appropriate). Each cell in the battery pack is a secondary battery, such as a lithium-ion battery or a nickel-hydrogen battery. For example, the main battery 41 supplies electric power to the PCU 7 to generate driving power for the vehicle 1, or stores energy regenerated by the PCU 7. Note that a capacitor, such as an electric double-layer capacitor, may be used instead of the main battery 41. The output size of the main battery 41 is smaller than, for example, one-tenth of the output of the FC stack 12. The main battery 41 is an example of an "energy storage device" according to the present invention.

[0024] SMR 42 is electrically connected between power line PL1 and main battery 41. According to a control command from ECU 100, SMR 42 electrically connects main battery 41 to power line PL1 or electrically disconnects main battery 41 from power line PL1.

[0025] The auxiliary battery 5 is electrically connected to the power line PL3. The auxiliary battery 5 is a secondary battery, for example, a lead-acid storage battery. The auxiliary battery 5 supplies electrical energy to drive the operation of various auxiliary machines (not shown) provided in the vehicle 1.

[0026] The step-down converter 61 is arranged outside the PCU 7 and is electrically connected between the power line PL1 and the power line PL2. According to a control command from the ECU 100, the step-down converter 61 steps down the electrical power transmitted via the power line PL1 from voltage level V1 to voltage level V2 and outputs the stepped-down electrical power to the power line PL2.

[0027] The step-down converter 62 is arranged outside the PCU 7 and is electrically connected between the power line PL2 and the power line PL3. According to a control command from the ECU 100, the step-down converter 62 steps down the electrical power transmitted via the power line PL2 from voltage level V2 to voltage level V3 and outputs the stepped-down electrical power to the power line PL3.

[0028] The step-down converter 71 is arranged inside the PCU 7 and is electrically connected between the power line PL1 and the power line PL2. According to a control command from the ECU 100, the step-down converter 71 steps down the electrical power transmitted via the power line PL1 from voltage level V1 to voltage level V2 and outputs the stepped-down electrical power to the power line PL2.

[0029] The step-down converter 72 is arranged inside the PCU 7 and is electrically connected between the power line PL2 and the power line PL3. According to a control command from the ECU 100, the step-down converter 72 steps down the electrical power transmitted via the power line PL2 from voltage level V2 to voltage level V3 and outputs the stepped-down electrical power to the power line PL3.

[0030] The inverter 73 is electrically connected between the power line PL1 and the motor generator 81. According to a control command from the ECU 100, the inverter 73 converts the DC power transmitted via the power line PL1 into AC power and outputs the AC power to the motor generator 81. Note that a bidirectional DC / DC converter may be arranged between the power line PL1 and the inverter 73.

[0031] Motor generator 81 is a rotating AC electric machine, for example, a three-phase AC synchronous motor, having a rotor with a permanent magnet embedded therein. Motor generator 81 operates with the AC power supplied from inverter 73 and drives drive wheels 82. Note that motor generator 81 is an example of a "traction motor" according to the present invention.

[0032] The FC cooling system 91, the charging unit cooling system 92, and the PCU cooling system 93 are electrically connected to the power line PL2. The FC cooling system 91 cools the FC stack 12 according to a control command from the ECU 100. The charging unit cooling system 92 cools the charging unit 3 according to a control command from the ECU 100. The PCU cooling system 93 cools the PCU 7 according to a control command from the ECU 100.

[0033] The air conditioning system 94 is electrically connected to the power line PL2. The air conditioning system 94 performs air conditioning in the vehicle interior according to a control command from the ECU 100.

[0034] The ECU 100 includes a processor such as a central processing unit (CPU), a memory such as a read-only memory (ROM) and a random access memory (RAM), and input / output ports (none of which are shown). In response to signals from sensors, the ECU 100 outputs various control commands to control the devices so as to bring the vehicle 1 into a desired state. The ECU 100 may be divided into several units depending on functions. In the present embodiment, examples of the main control performed by the ECU 100 include charging control via the auxiliary battery 5. In the vehicle 1, three electric power transmission paths for charging the auxiliary battery 5 are provided.

[0035] A first power transfer path runs via power line PL1, buck converter 61, power line PL2, buck converter 62, and power line PL3. The first power transfer path is used primarily for plug-in charging using DC input 21. A configuration without buck converters 61, 62 is also contemplated. In this case, however, to charge auxiliary battery 5 through plug-in charging via DC input 21, PCU 7 must be turned on to initiate operation of buck converters 71, 72. If buck converters 61, 62 are provided, plug-in charging can be performed via DC input 21 without needing to turn on PCU 7.

[0036] A second power transfer path runs via power line PL1, buck converter 71, power line PL2, buck converter 72, and power line PL3. The second power transfer path is primarily used when vehicle 1 is in a ReadyON state (described later).

[0037] A third energy transfer path runs via AC input 22, converter 31, and step-down converter 33 to power line PL3. The third energy transfer path, using AC input 22, is primarily used for plug-in charging.

[0038] The vehicle 1 further includes a power switch 101. The power switch 101 receives the user's system start operation and the system shutdown operation for the vehicle 1. When the user performs the system start operation while depressing the brake pedal, a power-on signal is output from the power switch 101 to the ECU 100. Upon receiving the power-on signal, the ECU 100 causes the vehicle 1 to transition from a system shutdown state (ReadyOFF state) to a system start state (ReadyON state). Specifically, in response to the power-on signal, the ECU 100 switches the SMR 42 from an open state to a closed state to allow the exchange of electrical energy between the main battery 41 and the PCU 7. Furthermore, the ECU 100 performs a system initialization process (such as a self-test) of the vehicle 1 to ensure that the system is ready to start.This causes the transition from the vehicle 1 to the driving state using the driving force of the motor generator 81. <Konfiguration des Abwärtswandlers>

[0039] Vehicle 1 has five buck converters 33, 61, 62, 71, 72. The buck converters 33, 61, 62, 71, 72 essentially have a common or the same circuit structure. Therefore, the circuit structure of the buck converter 61 is described representatively below.

[0040] Fig. 2 is a diagram showing an example of a circuit structure of the buck converter 61. In Fig. 2, the buck converter 61 has input nodes IN1, IN2, a DC / AC converter unit 611, a transformer T, a rectifier unit 612 and output nodes OUT1, OUT2.

[0041] The DC / AC converter unit 611 is, for example, a typical inverter and includes four switching elements Q1 to Q4. The switching elements Q1 to Q4 are, for example, each an insulated gate bipolar transistor (IGBT) or a power MOSFET (metal oxide semiconductor field-effect transistor). The switching element Q1 and the switching element Q2 are connected in series between the input node IN1 and the input node IN2. Similarly, the switching element Q3 and the switching element Q4 are connected in series between the input node IN1 and the input node IN2.

[0042] For example, the rectifier unit 612 is a diode bridge comprising four diodes D1 to D4. Diode D1 and diode D2 are connected in series between the output node OUT1 and the output node OUT2 in the forward direction from the output node OUT2 to the output node OUT1. Similarly, diode D3 and diode D4 are connected in series between the output node OUT1 and the output node OUT2 in the forward direction from the output node OUT2 to the output node OUT1.

[0043] The transformer T has an input electrically connected to a midpoint between the switching element Q1 and the switching element Q2, and to a midpoint between the switching element Q3 and the switching element Q4. The transformer T has an output electrically connected to the junction point of the anode of the diode D1 and the cathode of the diode D2, and to the junction point of the anode of the diode D3 and the cathode of the diode D4.

[0044] In the DC / AC converter unit 611, the switching element Q1 and the switching element Q4 perform a switching operation in a pair, and the switching element Q2 and the switching element Q3 perform a switching operation in a pair. The DC power input to the DC / AC converter unit 611 is then converted into a rectangular AC power, the positive and negative inversion of which occurs with each switching operation, and the rectangular AC power is output to the transformer T. The transformer T transforms (steps down) the voltage of the AC power from the DC / AC converter unit 611 and outputs an AC power with the transformed voltage to the rectifier unit 612. The rectifier unit 612 rectifies the AC power from the transformer T and converts it into DC power.

[0045] In the buck converter 61 having such a circuit configuration, the commutations of the diodes D1 to D4 present in the rectifier unit 612 limit the direction of energy conversion to the single direction indicated by the arrow in the figure. Electrical energy cannot be supplied from the output nodes OUT1, OUT2 to the input nodes IN1, IN2. <hilfsbatterie-ladesteuerung>

[0046] In the present embodiment, charging control is performed on the auxiliary battery 5 according to an operating state of the vehicle 1. Specifically, charging control for the auxiliary battery 5 differs when the vehicle 1 is in a ReadyON state and when the vehicle 1 is not ready to drive (e.g., the vehicle 1 is not ready to drive because the vehicle 1 is performing plug-in charging). In Embodiment 1, charging control of the auxiliary battery 5 when the vehicle 1 is in a ReadyON state will now be described.

[0047] Fig. Figure 3 is a diagram illustrating a charging control for the auxiliary battery 5 when vehicle 1 is in the ReadyON state. It should be noted that, for the sake of simplicity, some components (various relays and cooling systems) of vehicle 1 are Fig. 3 and Fig. 6, which are described below, are omitted.

[0048] In Fig. 3, a situation is assumed in which a charging cable is not plugged into the DC input 21 and the AC input 22 of vehicle 1, and vehicle 1 has entered the ReadyON state while a power-on operation is being performed by a user.

[0049] When vehicle 1 is in a ReadyON state, at least one of the electrical energy generated by the FC stack 12 and the electrical energy stored in the main battery 41 is transmitted to the power line PL1. When the auxiliary battery 5 is charged, this electrical energy can reach the power line PL3 through two power transmission paths (the first and second power transmission paths). As mentioned above, the first power transmission path passes through the buck converters 61, 62 arranged outside the PCU 7. The second power transmission path passes through the buck converters 71, 72 arranged inside the PCU 7.

[0050] When a load (FC cooling system 91, PCU cooling system 93, or air conditioning system 94) connected to the system power line PL2 is operating and consumes large amounts of electrical power, and only one power transmission path, the first and second power transmission paths, is used, this may result in a lack of electrical power supply to the power line PL2. Therefore, both the first and second power transmission paths are used.

[0051] In this case, it may also be considered that the first power transmission path (down converter 61) and the second power transmission path (down converter 71) are used without any particular distinction between them. However, as a result of these considerations, the inventor determined that it is desirable for the down converter 61 and the down converter 71 to be distinguished as the main down converter and the sub-down converter from the viewpoint of energy conservation of the vehicle 1 and / or the controllability of the vehicle 1.

[0052] When vehicle 1 is in a ReadyON state, the PCU 7 (in particular, inverter 73) is in operation because the vehicle 1 is traveling, or even when the vehicle 1 is not traveling, the PCU 7 is activated in preparation for traveling the vehicle 1. The PCU 7 can also be cooled by the PCU cooling system 93 if necessary. Consequently, the step-down converter 71 arranged inside the PCU 7 is ready for operation similarly to the inverter 73 and can be cooled accordingly. In contrast, the step-down converter 61 arranged outside the PCU 7 is originally provided so that the auxiliary battery 5, as described with reference to Fig. 1, can be charged even when the PCU 7 is deactivated. As such, the buck converter 61 and the buck converter 71 have different installation purposes, and the originally expected application scenarios of the two are correspondingly different.

[0053] Thus, in the present embodiment, when the vehicle 1 is in a ReadyON state and the PCU 7 is operating, the buck converter 71 in the PCU 7 takes priority over the buck converter 61 outside the PCU 7. In other words, when the vehicle 1 is in a ReadyON state, the buck converter 71 is used as the main buck converter and the buck converter 61 is used as the sub-buck converter. Specifically, the buck converter 71 and the buck converter 61 can be distinguished as the main buck converter and the sub-buck converter by setting the target voltage of the buck converter 71 to a higher value than the target voltage of the buck converter 61. Hereinafter, the target voltage of the buck converter 61 will be referred to as Vtag61. The target voltage of the buck converter 71 will be referred to as Vtag71.

[0054] Fig. 4 is a diagram showing effects of the target voltages in Embodiment 1. In Fig. In Figure 4, the horizontal axis shows a load current flow from buck converters 61, 71 to the power line PL2. The vertical axis shows an output voltage from buck converters 61, 71 to the power line PL2.

[0055] In general, a current that can be output by a buck converter has a maximum value (e.g., a rated current value) that depends on the specifications of the buck converter. This current is referred to as the "maximum output current." When the target voltage Vtag61 of the buck converter 61 and the target voltage Vtag71 of the buck converter 71 are different, and the target voltage Vtag71 is higher than the target voltage Vtag61 (Vtag71 > Vtag61), the load current to the power line PL2 is within a range as shown in Fig. 4, is less than or equal to the maximum output current of the buck converter 71, and an electrical energy reduced to the target voltage Vtag71 is output only by the buck converter 71 whose target voltage Vtag71 is higher than the target voltage Vtag61 of the buck converter 61. During this time, while the switching operation of the switching elements Q1 to Q4 present in the buck converter 61 (see Fig. 2) whose target voltage Vtag61 is lower than the target voltage Vtag71 of the buck converter 71 continues, no down-regulated electric power (an electric power with the voltage Vtag61) is output from the buck converter 61.

[0056] The electrical power output of the buck converter 61 is stopped for the following reason. When the buck converter 71 outputs electrical power stepped down to the target voltage Vtag71, the output side of the buck converter 71 and the output side of the buck converter 61 are at an equipotential, and thus the voltage on the output side of the buck converter 61 is also Vtag71. However, due to the rectification of the diodes D1 to D4, the buck converter 61 is only allowed to perform a unidirectional power conversion operation (buck conversion operation) and cannot output electrical power with an output voltage Vtag61 lower than the voltage Vtag71. Therefore, the buck converter 61 does not output electrical power as long as the output current of the buck converter 71 is sufficient.

[0057] However, if the output current of the buck converter 71 exceeds the maximum output current of the buck converter 71, a current exceeding the maximum output current cannot be output by the buck converter 71. Electrical energy is output from the buck converter 61 in addition to the buck converter 61. An output voltage of the buck converter 71, which is already operating at its limit, follows the output voltage of the buck converter 61. The buck converters 61, 71 then perform the buck conversion operation at a target voltage Vtag61 lower than Vtag71.

[0058] Therefore, in the present embodiment, the target voltage Vtag71 of the buck converter 71 is set higher than the target voltage Vtag61 of the buck converter 61. This may result in only the buck converter 71 outputting electrical power, and the output of electrical power from the buck converter 61 being stopped when the buck converter 71 alone is capable of supplying the current consumed or required by the load connected to the power line PL2. When the buck converter 71 can no longer supply the required current, the buck converter 61 compensates for the current deficit and thus meets the power demand. <ladesteuerverarbeitung>

[0059] Fig. 5 is a flowchart showing a charge control of the auxiliary battery 5 in Embodiment 1. The Fig. 5 and the following Fig. 8 and Fig. The flowcharts shown in Figure 9 are executed, for example, each time predetermined conditions are met or when a control cycle is executed. Each of the steps shown in this flowchart is generally implemented by software processing by the ECU 100, but can also be implemented by dedicated hardware (an electrical circuit) formed inside the ECU 100. Hereinafter, the steps are abbreviated as "S."

[0060] In Fig. 5, in S11, the ECU 100 determines whether to charge the auxiliary battery 5. For example, if the voltage of the auxiliary battery 5 is below a predetermined voltage, indicating that the state of charge (SOC) of the auxiliary battery 5 is reduced, the ECU 100 determines to charge the auxiliary battery 5. Alternatively, the ECU 100 may determine to charge the auxiliary battery 5 every time a certain time elapses (i.e., periodically). If the auxiliary battery 5 is not to be charged (NO in S11), the processing returns to the main routine.

[0061] If the auxiliary battery 5 is to be charged (YES in S11), the ECU 100 proceeds to S12 and determines whether the vehicle 1 is in a ReadyON state. If the vehicle 1 is in a ReadyON state (YES in S12), the ECU 100 sets the target voltage Vtag71 of the buck converter 71 higher than the target voltage Vtag61 of the buck converter 61 (Vtag71 > Vtag61) (S13). The ECU 100 then controls the buck converters 61, 62, 71, 72 to start charging the auxiliary battery 5 (S14).

[0062] Note that in Embodiment 1, when the vehicle 1 is not in a ReadyON state (NO in S12), that is, when the vehicle 1 is in a ReadyOFF state, processing returns to the main routine. In this case, the ECU 100 may set the target voltage Vtag61 and the target voltage Vtag71 equal and charge the auxiliary battery 5 according to a flowchart not shown (Vtag61 = Vtag71).

[0063] As described above, in Embodiment 1, when the vehicle 1 is in a ReadyON state, the ECU 100 sets the target voltage of the buck converter 71 disposed inside the PCU 7 to a higher value than the target voltage of the buck converter 61 disposed outside the PCU 7. This may cause only the buck converter 71 to output electric power, and the output of electric power from the buck converter 61 to be stopped as long as the buck converter 71 does not exceed the power supply capacity of the buck converter 71.

[0064] When vehicle 1 is in a ReadyON state, the PCU 7 is already activated, so a situation in which the PCU 7 is activated to charge the auxiliary battery 5 would not occur. This can prevent a reduction in the controllability of vehicle 1. Furthermore, in the state in which vehicle 1 is in the ReadyON state, the PCU 7 is also cooled as needed, so that energy loss (heat loss) caused at the buck converter 71 can also be reduced. Accordingly, energy efficiency in vehicle 1 can be improved.

[0065] It should be noted that in Embodiment 1, the PCU 7 according to the present invention corresponds to the "equipment," and the PCU cooling system 93 according to the present invention corresponds to the "cooling system." Furthermore, the buck converter 71 and the buck converter 61 according to the present invention correspond to the "first buck converter" and the "second buck converter," respectively. The power line PL2 corresponds to the "power line" according to the present invention. While the auxiliary battery 5 is charged with electric power transmitted from the power line PL2 to the power line PL3 via the buck converters 62, 72, it should be noted that even in such a charging mode, it can be said that "the auxiliary battery 5 is charged with electric power transmitted via the power line PL2." [Embodiment 2]

[0066] Embodiment 1 has been described with reference to the charge control of the auxiliary battery 5 when the vehicle 1 is in a ReadyON state. Embodiment 2 will be described with reference to a charge control for an auxiliary battery 5 when the vehicle 1 performs plug-in charging. It should be noted that the vehicle 1 according to Embodiment 2 has the same configuration (see Fig. 1) as vehicle 1 according to embodiment 1.

[0067] Fig. 6 is a diagram illustrating a charging control of the auxiliary battery 5 when the vehicle 1 performs a plug-in charging. In Fig. 6, a situation is assumed in which a charging cable (not shown) is plugged into an AC input 22 and AC energy can be supplied from a charging device via the AC input 22.

[0068] As mentioned above, two electric power supply paths, specifically the second power transmission path and the third power transmission path, are prepared even when the vehicle 1 performs plug-in charging. The second power transmission path passes through the buck converters 71, 72 arranged inside the PCU 7. The third power transmission path passes through the inverter 31 and the buck converter 33 arranged inside the charging unit 3. In Embodiment 2, a target voltage Vtag33 of the buck converter 33 is set higher than a target voltage Vtag72 of the buck converter 72 (Vtag33>Vtag72), so that the third power transmission path (buck converter 33) is a main path and the second power transmission path (buck converter 72) is a sub-path.

[0069] Fig. 7 is a diagram showing effects of the target voltages in Embodiment 2. In Fig. In Figure 7, the horizontal axis represents a load current flowing from the step-down converters 33, 72 to the power line PL3. The output voltages of the step-down converters 33, 72 (a charging voltage of the auxiliary battery 5) are represented on the vertical axis.

[0070] If, as in Fig. 7, when the target voltage Vtag33 is higher than the target voltage Vtag72, only the buck converter 33 whose target voltage Vtag33 is higher than Vtag72 performs buck conversion operation at the target voltage Vtag33 and outputs electric power until the load current reaches a maximum output current of the buck converter 33. During this time, the buck converter 72 whose target voltage Vtag72 is lower than Vtag33 stops outputting electric power while the switching operation continues. After the output current of the buck converter 33 reaches the maximum output current of the buck converter 33, both buck converters 33, 72 output electric power whose target voltage Vtag72 is lower than Vtag33.

[0071] Fig. Fig. 8 is a flowchart showing a charge control of the auxiliary battery 5 in Embodiment 2. In S21, the ECU 100 determines, as in Fig. 8 shows whether the auxiliary battery 5 should be charged. If the auxiliary battery 5 should be charged (YES in S21), the ECU 100 goes to S22.

[0072] In S22, the ECU 100 determines whether the vehicle 1 is performing plug-in charging. The ECU 100 can determine that the vehicle 1 is performing plug-in charging when a charging cable is plugged into the AC input 22 and a voltage sensor or a current sensor (not shown) provided in the charging unit 3 detects that the vehicle 1 is supplying power from outside the vehicle 1. Alternatively, before the vehicle 1 is actually supplied with power, it can be determined that the vehicle 1 is performing plug-in charging by communicating with the charging device via the charging cable once the vehicle 1 is ready to receive the power supply. Note that, in the present embodiment, the plug-in charging in S22 does not include rapid charging via a DC input 21.

[0073] When vehicle 1 performs plug-in charging (YES in S12), ECU 100 sets the target voltage Vtag33 of buck converter 33 higher than the target voltage Vtag72 of buck converter 72 (Vtag33 > Vtag72) (S23). The ECU 100 then controls boost converter 32 and buck converters 33, 71, 72 to start charging auxiliary battery 5 (S24).

[0074] As described above, in Embodiment 2, when the vehicle 1 is performing plug-in charging (where the vehicle 1 is ready for plug-in charging), the ECU 100 sets the target voltage of the buck converter 33 disposed inside the charging unit 3 to a value higher than the target voltage of the buck converter 72 disposed outside the charging unit 3 (in this example, inside the PCU 7). This may result in only the buck converter 33 outputting electric power, and the output of electric power from the buck converter 72 (and the buck converter 71) being stopped as long as the buck converter 33 does not exceed the power supply capacity of the buck converter 33.

[0075] When vehicle 1 performs plug-in charging, charging unit 3 is cooled by charging unit cooling system 92. This can reduce energy loss (heat loss) caused by buck converter 33. Furthermore, since PCU cooling system 93 only needs to be activated once buck converters 71, 72 are activated, the energy consumption of PCU cooling system 93 can be reduced. Accordingly, energy efficiency in vehicle 1 can be improved.

[0076] It should be noted that in Embodiment 2, the charging unit 3 according to the present invention corresponds to the "equipment," and the cooling system of the charging unit 92 according to the present invention corresponds to the "cooling system." Furthermore, the buck converters 33 and 72 correspond to the "first buck converter" and the "second buck converter" according to the present invention, respectively, provided that the "second buck converter" according to the present invention may be the buck converter 62. The power line PL3 according to the present invention corresponds to the "power line." [Variation]

[0077] The charging control for the auxiliary battery 5 described in Embodiment 1 and the charging control for the auxiliary battery 5 described in Embodiment 2 may be combined.

[0078] Fig. 9 is a flowchart showing a charge control of the auxiliary battery 5 according to the variation. In Fig. 9 in S31, the ECU 100 determines whether the auxiliary battery 5 should be charged.

[0079] When the auxiliary battery 5 is to be charged (YES in S31), the ECU 100 determines whether the vehicle 1 is in a ReadyON state (S32). If the vehicle 1 is in a ReadyON state (YES in S32), the ECU 100 sets the target voltage Vtag71 of the buck converter 71 higher than the target voltage Vtag61 of the buck converter 61 (Vtag71 > Vtag61) (S33). Furthermore, the ECU 100 controls the buck converters 61, 62, 71, 72 to start the charge control of the auxiliary battery 5 (S34).

[0080] If the vehicle 1 is not in a ReadyON state (NO in S32), the ECU 100 determines whether the vehicle 1 is performing plug-in charging (S35). If the vehicle 1 is performing plug-in charging (YES in S35), the ECU 100 sets the target voltage Vtag33 of the buck converter 33 higher than the target voltage Vtag72 of the buck converter 72 (Vtag33 > Vtag72) (S36). The ECU 100 then controls the boost converter 32 and the buck converters 33, 71, 72 to start charging the auxiliary battery 5 (S37).

[0081] Similar to Embodiments 1 and 2, in this variation, the buck converters used to charge the auxiliary battery 5 are differentiated as main buck converters and sub-buck converters depending on the use of the vehicle 1. This limits the cooling system to be operated, thereby improving energy efficiency in the vehicle 1.

[0082] It should be noted that in the variation, the PCU cooling system 93 corresponds to the "first cooling system" according to the present invention, and the charging unit cooling system 92 corresponds to the "second cooling system" according to the present invention. In addition, the buck converter 71, the buck converter 61, the buck converter 33, and the buck converter 72 each correspond to a "first buck converter," a "second buck converter," a "third buck converter," and a "fourth buck converter" according to the present invention. The power line PL2 corresponds to the "first power line" according to the present invention, and the power line PL3 corresponds to the "second power line" according to the present invention.

[0083] Embodiments 1 and 2 and the variation have been described with reference to the vehicle 1 capable of plug-in charging (contact charging). However, the vehicle 1 may be capable of contactless charging, in which electrical power is contactlessly transmitted from a power transmission apparatus provided outside the vehicle 1 to a power reception apparatus mounted in the vehicle 1.

[0084] Although the present invention has been described and illustrated in detail, it is to be understood that this is by way of illustration and example only and is not to be considered limiting. The scope of the present invention is to be interpreted in accordance with the terms of the appended claims.< / ladesteuerverarbeitung>

Claims

[1] Vehicle (1) which has: a first step-down converter (71, 33) that performs a step-down operation to generate a first target voltage and outputs a stepped-down electric power to a power line (PL2, PL3); a second step-down converter (61, 72) that performs a step-down operation to generate a second target voltage and outputs a reduced electric power to the power line (PL2, PL3); an auxiliary battery (5) charged with electrical energy transmitted via the power line (PL2, PL3); a control unit (100) that outputs the first target voltage to the first buck converter (71, 33) and the second target voltage to the second buck converter (61, 72); a cooling system (93, 91); and Equipment (7, 3) cooled by the cooling system (93, 91), wherein the first down converter (71, 33) is arranged inside the equipment (7, 3), the second down converter (61, 72) is arranged outside the equipment (7, 3), and the control unit (100) sets the first target voltage higher than the second target voltage when the control unit (100) causes the equipment (7, 3) to operate. [2] Vehicle (1) according to claim 1, further comprising a traction motor (81), wherein the equipment is an energy converter (7) that drives the traction motor (81). [3] The vehicle (1) according to claim 1, further comprising an energy storage device (41), wherein the equipment is a charging unit (3) that charges the energy storage device (41) with energy supplied from outside the vehicle (1). [4] Vehicle (1) according to one of claims 1 to 3, wherein the control unit (100) sets the first target voltage higher than the second target voltage, so that while the first down-converter (71, 33) outputs a reduced electrical energy to the power line (PL2, PL3), the second down-converter (61, 72) is prevented from outputting a reduced electrical energy to the power line (PL2, PL3) when an output current from the first down-converter (71, 33) is smaller than a maximum output current of the first down-converter (71, 33), and the second buck converter (61, 72) outputs a reduced electrical power to the power line (PL2, PL3) in addition to the first buck converter (71, 33) when the output current from the first buck converter (71, 33) is greater than the maximum output current. [5] The vehicle (1) according to claim 4, further comprising another cooling system (93) that cools the second buck converter (72), wherein the control unit (100) deactivates the other cooling system (93) when the output current of the first buck converter (33) is less than the maximum output current. [6] Vehicle (1) which has: a first step-down converter (71) that performs a step-down operation to generate a first target voltage and outputs a reduced electric power to a first power line (PL2); a second step-down converter (61) that performs a step-down operation to generate a second target voltage and outputs a reduced electric power to the first power line (PL2); a third step-down converter (33) that performs a step-down operation to generate a third target voltage and outputs a reduced electric power to a second power line (PL3); a fourth buck converter (72) that performs a buck converter operation to generate a fourth target voltage and outputs a reduced electric power to the second power line (PL3); an auxiliary battery (5) charged by the buck converter operation of the first to fourth buck converters (71, 61, 33, 72); a control unit (100) which outputs the first to fourth target voltages to the first to fourth step-down converters (71, 61, 33, 72), respectively; a traction motor (81); an energy converter (7) which drives the traction motor (81); an energy storage device (41); a charging unit (3) that charges the energy storage device (41) with electrical energy supplied from outside the vehicle (1); a first cooling system (93) which cools the energy converter (7); and a second cooling system (92) which cools the charging unit (3), wherein the first step-down converter (71) is arranged inside the energy converter (7), the second step-down converter (61) is arranged outside the energy converter (7) and the charging unit (3), the third step-down converter (33) is arranged inside the charging unit (3), and the fourth down converter (72) is arranged inside the energy converter (7), wherein the control unit (100): sets the first target voltage higher than the second target voltage when the control unit (100) causes the energy converter (7) to operate; and sets the third target voltage higher than the fourth target voltage when the control unit (100) causes the charging unit (3) to operate. [7] Method for controlling a vehicle (1), where the vehicle has a first step-down converter (71, 33) that performs a step-down operation to generate a first target voltage and outputs a stepped-down electric power to a power line (PL2, PL3); a second step-down converter (61, 72) that performs a step-down operation to generate a second target voltage and outputs a reduced electric power to the power line (PL2, PL3); an auxiliary battery (5) charged with electrical energy transmitted via the power line (PL2, PL3); a cooling system (93, 91); and Equipment (7, 3) cooled by the cooling system (93, 91), wherein the first down converter (71, 33) is arranged inside the equipment (7, 3), and the second down converter (61, 72) is arranged outside the equipment (7, 3), the method comprising: Determining whether operation of the equipment (7, 3) should be initiated; and Setting the first target voltage to a higher value than the second target voltage when operation of the equipment (7, 3) is initiated.

Images