Power distribution device, power supply system, and supply control program

Abstract

A zone ECU (1) as a power distribution device is connected to a power supply system (2), a plurality of loads (4), and a vehicle state sensor (5). The zone ECU (1) includes a primary DC-DC converter (85), a control unit (87), and a communication unit (88). The primary DC-DC converter (85) is a circuit module that steps down a power supply voltage input from the power supply system (2) and generates a voltage to be supplied to the loads (4). The communication unit (88) receives a signal indicating a vehicle state from the vehicle state sensor (5) and provides the signal to the control unit (87). The control unit (87) estimates the vehicle state on the basis of the signal received by the communication unit. The control unit (87) is configured to change a target output voltage of the primary DC-DC converter (85) on the basis of a vehicle state estimation result.

Description

Power distribution device, power supply system, supply control program Cross-reference to related applications

[0001] This application is based on Japanese Patent Application No. 2024-191067 filed in Japan on October 30, 2024, and the contents of the base application are incorporated herein by reference in their entirety.

[0002] The present disclosure relates to a technique for stepping down a DC power supply voltage and supplying it to a load.

[0003] Patent Document 1 discloses an electronic control device that controls power supply to a plurality of loads having different operating voltages. The plurality of loads having different operating voltages include a 48V load and a 12V load. The 48V load is a load that operates at 48V (for example, within the range of 36V to 52V). The 12V load is a load that operates at 12V (for example, within the range of 6V to 18V). The electronic control device includes a DC-DC converter, steps down a DC power supply voltage of 48V or more, and supplies power to the 12V load.

[0004] Japanese Patent Application Laid-Open No. 2023-15871

[0005] Vehicles are equipped with various loads, not limited to 48V loads and 12V loads. The various loads include low-voltage loads such as sensors and ICs that operate at 5V (for example, within the range of 3.6V to 5.5V). In electric vehicles (EVs) and hybrid vehicles (HEVs), reduction of power consumption during parking is important. However, the operating states of each load during parking or when the vehicle is stationary may vary depending on the operation of the occupant.

[0006] In a vehicle state where a 12V load such as a motor can operate, setting the output voltage of the DC-DC converter to a voltage as high as possible within the operating range of the load can contribute to reduction of overall power consumption. This is because the current can be reduced by increasing the voltage, and the power loss can be reduced. On the other hand, in a vehicle state where only low-voltage loads operate, setting the output voltage of the DC-DC converter to a voltage at which the low-voltage load can operate can increase the energy efficiency of the entire vehicle system.

[0007] One of the purposes of this disclosure is to provide a power distribution device that can improve energy efficiency in vehicles.

[0008] The power distribution device disclosed herein is a power distribution device mounted on a vehicle and comprises a DC-DC converter that steps down a power supply voltage input from a power supply system to generate a voltage for supplying power to a load, a control unit that controls the output voltage of the DC-DC converter, and a communication unit that receives a signal indicating the vehicle status or a signal indicating a voltage setting according to the vehicle status from other on-board devices, wherein the control unit is configured to change the target output voltage of the DC-DC converter based on the signal received by the communication unit.

[0009] Furthermore, the power supply system included in this disclosure is a power supply system that includes a power supply system and a power distribution device mounted on a vehicle, wherein the power supply system includes a high-voltage battery with an output voltage of 200V or more and an isolated DC-DC converter that reduces the output voltage of the high-voltage battery to 60V or less, and the power distribution device includes a power input terminal that receives the output voltage of the isolated DC-DC converter as the power supply voltage, a DC-DC converter that steps down the power supply voltage to generate a voltage for supply to a load, a control unit that controls the output voltage of the DC-DC converter, and a communication unit that receives a signal indicating the vehicle status or a signal indicating a voltage setting according to the vehicle status from other on-board devices, wherein the control unit is configured to change the target output voltage of the DC-DC converter based on the signal received by the communication unit.

[0010] The supply control program included in this disclosure is a supply control program executed by a computer connected to a DC-DC converter that steps down a power supply voltage input from a power supply system to generate a voltage for supply to a load, and a communication unit configured to communicate with other in-vehicle devices, and includes instructions to cause the computer to perform the following actions: obtain information indicating the vehicle status or information on voltage settings according to the vehicle status from other in-vehicle devices using the communication unit, and adjust the output voltage of the DC-DC converter based on the information indicating the vehicle status or the voltage setting information obtained using the communication unit.

[0011] According to the technology described above, the output voltage of the DC-DC converter is changed according to the vehicle conditions. The DC-DC converter generates a voltage that is suitable for the vehicle conditions and, consequently, the operating conditions of the on-board load. Therefore, power loss or oversupply of power can be reduced. This makes it possible to reduce power consumption in the vehicle.

[0012] Furthermore, the power distribution device included in this disclosure is a power distribution device mounted on a vehicle, comprising: a DC-DC converter that steps down the power supply voltage input from a power supply system to generate a voltage for supplying power to a load; a low-load power supply unit connected in parallel with the DC-DC converter, which steps down the power supply voltage to generate a voltage for supplying power to a load and has a smaller maximum output current than the DC-DC converter; a communication unit that receives signals indicating the vehicle status or signals indicating voltage settings according to the vehicle status from other on-board devices; and a control unit that selects whether to use the DC-DC converter or the low-load power supply unit for supplying power to the load based on the signals received by the communication unit.

[0013] According to the above technology, the configuration for supplying power is selected from among the DC-DC converter and the low-load power supply unit depending on the vehicle condition. Therefore, the configuration that is suitable for the vehicle condition and, consequently, the operating condition of the onboard load, will supply power. As a result, power loss or excessive power supply can be reduced, and thus the power consumption in the vehicle can be reduced.

[0014] The symbols in parentheses in the claims indicate a correspondence with the specific means described later in the embodiments, and do not limit the technical scope of this disclosure.

[0015] This figure illustrates the configuration of a zone ECU according to the first embodiment of the present disclosure. This is a block diagram of the control unit. This is a state transition diagram of the vehicle or zone ECU. This is a flowchart of the transition process to the first state. This figure shows the state of the power distribution circuit in the first state. This is a flowchart of the transition process to the second state. This figure shows the state of the power distribution circuit in the second state. This is a flowchart of the transition process to the third state. This figure shows the state of the power distribution circuit in the third state. This is a flowchart of the transition process to the fourth state. This figure shows the state of the power distribution circuit in the fourth state. This is a flowchart of the transition process to the fifth state. This figure shows a continuation of the flowchart of the transition process to the fifth state shown in Figure 12. This figure shows the state of the power distribution circuit in the fifth state. This is a flowchart of the transition process to the sixth state. This figure shows the state of the power distribution circuit in the sixth state. This is a flowchart of the transition process to the seventh state. This figure shows a continuation of the flowchart of the transition process to the seventh state shown in Figure 17. This figure shows the state of the power distribution circuit in the seventh state. This figure shows an example of the configuration of the energy storage unit. This figure shows another example of the configuration of the energy storage unit. This figure shows a power distribution circuit with a main power switch introduced. This figure shows a system including a zone ECU and a higher-level ECU. This figure shows a modified example of the power supply system. This is a diagram illustrating the configuration of a zone ECU according to a second embodiment of the present disclosure. This is a diagram illustrating the configuration of a power supply system including a zone ECU according to a third embodiment of the present disclosure. This is a diagram illustrating the details of a communication frame. This is a diagram illustrating the configuration of a zone ECU according to a fourth and fifth embodiment of the present disclosure. This is a diagram illustrating the intermittent operation of a secondary DC-DC converter in a deep sleep state.

[0016] Embodiments of this disclosure will be described below with reference to the drawings. This disclosure is not limited to the embodiments described below. The configurations disclosed below may be implemented with various modifications without departing from the gist of the invention. Various modifications may be combined as appropriate, without causing any technical inconsistencies. This disclosure also includes configurations that are not explicitly stated, which are combinations of multiple modifications. In the following description, components having the same function may be denoted by the same reference numeral and their specific description may be omitted. Also, components having the same function may be denoted by the same or similar names and their specific description may be omitted. If only a part of a configuration is referred to, the description of the other parts may be applied elsewhere.

[0017] (First Embodiment) Figure 1 schematically shows a power supply system according to the first embodiment of this disclosure. The details of the zone ECU 1 of the first embodiment and the power supply system including this zone ECU 1 will be described below.

[0018] <Overall Configuration> The power supply system includes a Zone ECU (Electronic Control Unit) 1 mounted on the vehicle. The Zone ECU 1 is connected to a power supply system 2, a sub-battery 3, multiple loads 4, and a vehicle condition sensor 5. The following description assumes the vehicle is an electric vehicle (EV). The vehicle may also be a hybrid electric vehicle (HEV) or a gasoline-powered vehicle. In the following, a DC-DC converter refers to a circuit / device that converts direct current (DC) to direct current (DC).

[0019] Power supply system 2 is a system that supplies power to zone ECU 1. Power supply system 2 includes a main battery 21, an isolated DC-DC converter 22, and a power manager 23. The main battery 21 is a battery used to run the vehicle. The main battery 21 is configured to output a high voltage of, for example, 800V or more. The output voltage of the main battery 21 may be several hundred volts. The main battery 21 has a larger power capacity than the sub-battery 3. The main battery 21 may also be called a drive battery, EV battery, or high-voltage battery. The main battery 21 may be a lithium-ion battery or an all-solid-state battery.

[0020] The isolated DC-DC converter 22 converts the output voltage of the main battery 21 to 48V and supplies it to the zone ECU 1. The isolated DC-DC converter 22 is a DC-DC converter in which the input and output sides are electrically isolated using a transformer. The isolated DC-DC converter 22 may be a full-bridge converter. The isolated DC-DC converter 22 may be a DC-DC converter having any circuit configuration, such as a flyback converter. The output terminal of the isolated DC-DC converter 22 is electrically connected to the main power input terminal 11 of the zone ECU 1.

[0021] The power manager 23 is a computer that controls the isolated DC-DC converter 22. The power manager 23 drives the isolated DC-DC converter 22 and starts supplying power to the zone ECU 1, etc., in response to, for example, a user's startup operation of the vehicle. The startup operation may be, for example, pressing a power switch located on the instrument panel. The power manager 23 may be configured to enable data communication with the zone ECU 1. The power system 2 and the zone ECU 1 described above may be connected by one or more cables. For example, the power system 2 and the zone ECU 1 may be connected by a power cable for supplying power and a communication cable for data communication. The communication cable may constitute part of the in-vehicle network. The power cable and the communication cable may be bundled together or integrated. The power system 2 is configured to supply power to components other than the zone ECU 1, such as the powertrain system including the drive motor.

[0022] Sub-battery 3 is a DC power source with a smaller power capacity than the main battery 21. Sub-battery 3 is configured to output a DC voltage of 48V. Sub-battery 3 may also be called an auxiliary battery. Sub-battery 3 may also be a lithium-based battery. Sub-battery 3 may also be a lead-acid battery, nickel-metal hydride battery, or nickel-cadmium battery. Sub-battery 3 is electrically connected to the sub-power input terminal 12 of the zone ECU 1 via a power cable. Sub-battery 3 may be incorporated into the power system 2.

[0023] The multiple loads 4 may be other ECUs, actuators, or sensors. The multiple loads 4 include a 48V load 4α and a 12V load 4β. The 48V load 4α is a load that operates at a voltage around 48V. The 48V load 4α may be a load that operates at an input voltage of, for example, 36V to 52V. The 48V load can be rephrased as a high-voltage load.

[0024] The 48V load 4α may be, for example, a radiator fan, a battery cooling fan, an air conditioning fan (so-called blower), or an HPC (High Performance Computer) cooling fan. The battery cooling fan is a fan for cooling the main battery 21. The HPC cooling fan is a fan for cooling the HPC. The HPC is a high-performance ECU that performs complex / large-scale processing, such as an autonomous driving ECU or an ADAS (Advanced Driver-Assistance Systems) ECU. The HPC itself may also be included in the 48V load 4α. The electric power steering and brake system may also be an example of a 48V load 4α. Not all fan motors are 48V load 4α; some fan motors may be 12V load 4β.

[0025] The loads 4A and 4B shown in Figure 1 are 48V loads 4α. Load 4A may be a blower, and load 4B may be a battery cooling fan. The 48V load 4α corresponds to the first type of load. Note that there may be one 48V load 4α connected to Zone ECU 1, or there may be three or more.

[0026] A 12V load 4β is a load that operates at a voltage around 12V. A 12V load 4β may be a load that operates with an input voltage of, for example, 6V to 18V. A 12V load 4β corresponds to the second type of load. A 12V load 4β can be rephrased as a medium-voltage load. A 12V load 4β mainly includes body actuators and infotainment devices. Body actuators include power window motors, lock motors, side mirror motors, wipers, headlights, hazard lights, etc. Infotainment devices include audio systems, navigation systems, or meter displays, etc. A more specific example of a 12V load 4β may be a brushed motor. Loads 4K and 4L shown in Figure 1 are 12V loads 4β. For example, load 4K may be an audio system, and load 4L may be a meter display.

[0027] Although not shown in Figure 1, a 5V load operating at a voltage of around 5V may be connected to the zone ECU 1. The 5V load may be a device operating at 3.6V to 5.5V. The 5V load can also be referred to as a low-voltage load. Examples of 5V loads include sensors, microcomputers, ICs, and PHY chips for communication. The 5V load corresponds to the third type of load. In other embodiments, the zone ECU 1 may also include a 24V load operating at a voltage of around 24V.

[0028] Furthermore, load 4 is not necessarily limited to devices located outside the enclosure of zone ECU 1. Multiple loads 4 may include loads located inside zone ECU 1. The control unit 87 and communication unit 88 built into zone ECU 1 may be included in the 5V load.

[0029] Each of the multiple loads 4 is connected to the zone ECU 1 by a power cable. Each load 4 is also connected to the zone ECU 1 via an in-vehicle network for communication. The in-vehicle network may be a local area network (LAN) conforming to any standard. Some or all of the multiple loads 4 may be individually connected using communication cables. The in-vehicle network may include multiple communication cables.

[0030] The vehicle status sensor 5 is a sensor that detects items related to the vehicle status. Items related to the vehicle status include at least one of the following: shift position, driving speed, brake status, and locked status. The vehicle status sensor 5 may include at least one of the following: shift position sensor, vehicle speed sensor, brake sensor, and lock sensor. The shift position sensor is a sensor that detects the shift position. The vehicle speed sensor is a sensor that detects the driving speed of the vehicle. The vehicle speed sensor may be a wheel speed sensor. The brake sensor may be a sensor that detects the amount (angle) of the brake pedal depression as the amount of brake operation (a so-called brake pedal position sensor). The lock sensor is a sensor that detects whether the vehicle is locked (locked / unlocked).

[0031] The vehicle condition sensor 5 may include sensors that detect driver operations on the vehicle, such as a brake sensor. The vehicle condition sensor 5 may also include a hazard switch, power switch, audio switch, air conditioning switch, etc. The hazard switch is a switch for turning the hazard lights on and off. The power switch is a switch for turning the vehicle power on and off. The audio switch is a switch for turning the audio system on and off. The air conditioning switch is a switch for turning the air conditioning system on and off. These switches may be located on the instrument panel or elsewhere.

[0032] The vehicle status sensor 5 inputs signals indicating the detection results of various sensors to the zone ECU 1. The output signal of the vehicle status sensor 5 indirectly or directly indicates the vehicle status. The output signal of the vehicle status sensor 5 corresponds to a signal indicating the vehicle status, and the vehicle status sensor 5 corresponds to an example of other in-vehicle devices. In this embodiment, the zone ECU 1 determines the vehicle status by integrating the detection results of one or more sensors included in the vehicle status sensor 5. The signal indicating the vehicle status may be understood as a signal for the zone ECU 1 to identify the vehicle status. In other embodiments, the vehicle status sensor 5 may be configured to transmit the detection results to a higher-level ECU. The higher-level ECU may be configured to input a data signal indicating the vehicle status determined based on the detection results of the vehicle status sensor 5 to the zone ECU 1. The vehicle status sensor may also be a device that outputs a signal indicating the determination result of the vehicle status.

[0033] The zone ECU 1 is located in each of the multiple zones pre-configured in the vehicle. The multiple zones may be, for example, a front zone, a rear zone, a right zone, and a left zone. Each of the multiple zone ECUs 1 may be connected to the power supply system 2.

[0034] The Zone ECU 1 has a power distribution circuit 10 formed on a circuit board. The Zone ECU 1 is a circuit that converts the voltage input from the power system 2 or sub-battery 3 (hereinafter also referred to as the power supply voltage) into a voltage suitable for the operation of the load 4 and supplies it to the load 4. The Zone ECU 1 is configured to generate multiple types of voltages depending on the type of load 4 connected to the Zone ECU 1. The Zone ECU 1 distributes power to each of the multiple loads 4. A load relay 89, which will be described later, is provided at the connection part of the Zone ECU 1 to the load 4. The Zone ECU 1 may be configured to change the combination of loads 4 to which power is supplied by turning the load relay 89 on or off. The Zone ECU 1 corresponds to a power distribution device.

[0035] Zone ECU 1 may have functions other than power supply. For example, Zone ECU 1 may have a gateway function and enable communication between networks with different communication methods by performing data conversion and relay. Zone ECU 1 may also have a function to control load 4 based on commands from a higher-level ECU.

[0036] The Zone ECU 1 has two power supply systems, a main battery 21 and a sub-battery 3, providing redundancy in its power supply function. In the power supply system 2, which includes the main battery 21, if a failure occurs such as battery disconnection, wire breakage, or ground fault, power will be supplied from the sub-battery 3 instead of the main battery 21 to critical loads. This prevents the loss of critical safety functions.

[0037] <Zone ECU> Next, the configuration of Zone ECU 1 will be described. Zone ECU 1 is equipped with a main power input terminal 11, a sub power input terminal 12, a plurality of load terminals 13, and a communication terminal 14. The plurality of load terminals 13 include load terminals 13A, 13B, 13K, and 13L corresponding to loads 4A, 4B, 4K, and 4L.

[0038] In addition to the above, the zone ECU 1 also includes a first switch 81, a sub-power switch 82, a second switch 83, a main relay 84, a primary DC-DC converter 85, a secondary DC-DC converter 86, a control unit 87, a communication unit 88, a plurality of load relays 89, and a power storage unit 90. The plurality of load relays 89 include load relays 89A, 89B, 89K, and 89L corresponding to loads 4A, 4B, 4K, and 4L.

[0039] In addition, Zone ECU 1 is equipped with multiple conductive wires as wiring to connect the components that make up the circuit. The conductive wires may be conductive films made of copper provided on a printed circuit board. That is, the conductive wires may be patterned on the surface or internal layers of the printed circuit board. The conductive wires may be microstrips or striplines in one curved surface. The conductive wires may include jumper wires or vias. The term "conductive wire" may be replaced with "signal line" or "conductive path," etc.

[0040] The multiple conductive wires include a main power line 91, a sub-power line 92, a first voltage line 93, a lead line 94, a second voltage line 95, a branch line 96, and a third voltage line 97. The main power line 91 is a conductive wire that electrically connects the main power input terminal 11 and the first switch 81. The sub-power line 92 is a conductive wire that electrically connects the sub-power switch 82 and the second switch 83. The main power line 91 and the sub-power line 92 are connected via a main relay 84.

[0041] The first voltage line 93 is a conductive wire that electrically connects the first switch 81 and the load relay 89 corresponding to the 48V load 4α. The lead wire 94 is a conductive wire that electrically connects the second switch 83 and the primary DC-DC converter 85. The second voltage line 95 is a conductive wire that electrically connects the primary DC-DC converter 85 and the load relay 89 corresponding to the 12V load 4β. The branch wire 96 is a conductive wire with one end connected to the second voltage line 95 and the other end connected to the secondary DC-DC converter 86. The third voltage line 97 is a conductive wire that connects the secondary DC-DC converter 86 and the control unit 87.

[0042] Hereinafter, a circuit including the first switch 81, the sub-power switch 82, the second switch 83, the main relay 84, the primary DC-DC converter 85, the secondary DC-DC converter 86, a plurality of load relays 89, and a plurality of conductive wires is also described as the power distribution circuit 10. The power distribution circuit 10 may include a control unit 87 and a communication unit 88.

[0043] The main power input terminal 11 is electrically connected to the output of the isolation DC-DC converter 22. The main power input terminal 11 may be integrally formed with a connector exposed outside the housing of the zone ECU 1. Power is supplied to the main power input terminal 11 from the isolation DC-DC converter 22 through a power cable or the like connected to the connector. The output voltage of the isolation DC-DC converter 22 is input to the main power input terminal 11.

[0044] Inside the housing of the zone ECU 1, the main power input terminal 11 is connected to the first switch 81 via the main power line 91. The main power input terminal 11 is also connected to the main relay 84. The voltage input to the main power input terminal 11 is input to the first switch 81 and the main relay 84.

[0045] "Vin" in the figure indicates the power supply voltage which is the voltage input to the zone ECU 1. Basically, the power supply voltage is the output voltage of the isolation DC-DC converter 22. However, the power supply voltage in a state where the isolation DC-DC converter 22 is deactivated can be the output voltage of the sub-battery 3. Basically, the power supply voltage is 48V. However, depending on the vehicle state, after the sub-power switch 82 is turned off, the output voltage of the isolation DC-DC converter 22 may be set to 10V at the request of the control unit 87. The power supply voltage can temporarily become 10V according to the vehicle state.

[0046] The sub-power input terminal 12 is electrically connected to the output of the sub-battery 3. The sub-power input terminal 12 may be integrally formed with a connector exposed outside the housing of the zone ECU 1. Power can be supplied to the sub-power input terminal 12 from the sub-battery 3 through a power cable or the like connected to the connector. The output voltage (48V) of the sub-battery 3 is input to the sub-power input terminal 12. Inside the housing of the zone ECU 1, the sub-power input terminal 12 is connected to the sub-power switch 82 via a conductive wire. The voltage input to the sub-power input terminal 12 is input to the sub-power switch 82.

[0047] The load terminal 13 is electrically connected to the corresponding load 4. Inside the housing, the load terminal 13 is electrically connected to the corresponding load relay 89. The load terminal 13 is integrally formed with a connector exposed outside the housing of the control device. The load terminal 13 supplies power to the corresponding load 4 through a power cable or the like connected to the connector.

[0048] As described above, the load terminal 13 includes load terminals 13A, 13B, 13K, and 13L. The load terminal 13A is connected to the load 4A outside the housing and to the load relay 89A inside the housing. The load terminal 13B is connected to the load 4B outside the housing and to the load relay 89B inside the housing. The load terminal 13K is connected to the load 4K outside the housing and to the load relay 89K inside the housing. The load terminal 13L is connected to the load 4L outside the housing and to the load relay 89L inside the housing. The load 4 corresponding to a certain load terminal 13 is the load 4 electrically connected to the load terminal 13. In this embodiment, there is one load 4 connected to one load terminal 13. In other embodiments, a plurality of loads 4 may be connected to one load terminal 13 using a branch terminal or a branch tap or the like.

[0049] The communication terminal 14 is connected to multiple loads 4 and vehicle condition sensors 5 so that they can communicate with each other via an in-vehicle network. The communication terminal 14 may be integrally configured with a connector exposed on the outside of the housing of the zone ECU 1. Inside the housing, the communication terminal 14 is connected to the communication unit 88. The communication terminal 14 may have multiple terminals. The communication terminal 14 may be connected to multiple loads 4 by individual cables without going through the in-vehicle network. The communication terminal 14 may be connected to the vehicle condition sensors 5 by dedicated cables without going through the in-vehicle network.

[0050] The first switch 81 is a switch for switching the electrical connection state (hereinafter also referred to as the conduction state or open / closed state) between the main power line 91 and the first voltage line 93. The conduction state includes a connected state in which the two elements are electrically connected (also referred to as the on state or closed state) and a disconnected state in which they are electrically separated (also referred to as the off state or open state). The first switch 81 may include an input terminal, an output terminal and a control input terminal. The input terminal of the first switch 81 is electrically connected to the main power line 91. The output terminal of the first switch 81 is electrically connected to the first voltage line 93. The control input terminal is electrically connected to the control unit 87.

[0051] The first switch 81 switches between a conductive state (in other words, on / off) based on a control signal input from the control unit 87. When the first switch 81 is on, the power supply voltage (Vin) is supplied to the 48V load 4α via the first voltage line 93 and the load relay 89. When the first switch 81 is set to off, the main power line 91 and the first voltage line 93 are electrically isolated. The first switch 81 is configured to interrupt the power supply to electrical components located downstream of the first voltage line 93 (for example, the 48V load 4α).

[0052] Such a first switch 81 may be mainly composed of semiconductor switches such as FETs (Field Effect Transistors). The semiconductor switch may be an N-channel MOS (Metal-Oxide-Semiconductor) FET, a P-channel MOSFET, a GaNFET, a SiC-MOSFET, a bipolar transistor, an IGBT (Insulated Gate Bipolar Transistor), or other types of switching elements. A GaNFET is a power semiconductor device in which the wide-bandgap semiconductor is gallium nitride (GaN). A SiC-MOSFET is a power semiconductor device in which the wide-bandgap semiconductor is silicon carbide (SiC). The first switch 81 may also be an IPD (Intelligent Power Device). Furthermore, the first switch 81 may also be a mechanical switch (also called a contact relay) using a coil or the like. Not limited to the first switch 81, the various switches / relays described below may also be implemented using mechanical switches.

[0053] When the first switch 81 is an N-channel MOSFET, the drain corresponds to the input terminal, the source to the output terminal, and the gate to the control input terminal. That is, the drain of the N-channel MOSFET as the first switch 81 may be connected to the main power line 91, the source to the first voltage line 93, and the gate to the control unit 87.

[0054] The sub-power switch 82 is a switch for switching the electrical connection state between the sub-power input terminal 12 and the sub-power line 92. The sub-power switch 82 may include an input terminal, an output terminal, and a control input terminal. The input terminal of the sub-power switch 82 is electrically connected to the sub-power input terminal 12 via a conductive wire. The output terminal of the sub-power switch 82 is electrically connected to the sub-power line 92. The control input terminal of the sub-power switch 82 is electrically connected to the control unit 87. The sub-power switch 82, like the first switch 81, may be implemented using any type of semiconductor switch or mechanical switch.

[0055] The sub-power switch 82 switches between a conductive state (on / off) based on a control signal input from the control unit 87. When the sub-power switch 82 is on, the sub-battery 3 and the sub-power line 92 are electrically connected, and power from the sub-battery 3 can be supplied to the primary DC-DC converter 85, etc. When the sub-power switch 82 is set to off, the sub-battery 3 is substantially / electrically disconnected from the zone ECU 1. The sub-power switch 82 is configured to cut off the power supply from the sub-battery 3 to the zone ECU 1 and the load 4.

[0056] The second switch 83 is a switch for switching the electrical connection state between the sub-power line 92 and the lead line 94. The second switch 83 may include an input terminal, an output terminal, and a control input terminal, similar to the first switch 81. The input terminal of the second switch 83 is electrically connected to the sub-power switch 82 via the sub-power line 92. The output terminal of the second switch 83 is electrically connected to the lead line 94. The control input terminal of the second switch 83 is connected to the control unit 87. The second switch 83 may be implemented using any type of semiconductor switch or mechanical switch, similar to the first switch 81.

[0057] The second switch 83 switches between on and off states based on a control signal input from the control unit 87. When the second switch 83 is on, the sub-power line 92 and the lead line 94 are electrically connected, and the power supply voltage (Vin) is input to the primary DC-DC converter 85. When the second switch 83 is set to off, the power supply to the circuits after the primary DC-DC converter 85 is cut off.

[0058] The main relay 84 is a switch for switching the electrical connection state between the main power line 91 and the sub-power line 92. The main relay 84, like the first switch 81, may include an input terminal, an output terminal, and a control input terminal. The input terminal of the main relay 84 is electrically connected to the main power line 91 and, consequently, to the isolated DC-DC converter 22. The output terminal of the main relay 84 is electrically connected to the sub-power line 92. The control input terminal of the main relay 84 is electrically connected to the control unit 87. The main relay 84 may be implemented using any type of semiconductor switch (e.g., an FET or IPD). The main relay 84 may also be any type of mechanical switch.

[0059] The main relay 84 switches between on and off states based on a control signal input from the control unit 87. When the main relay 84 is on, the main power line 91 and the sub power line 92 are electrically connected. When the main relay 84 is on, the output of the isolated DC-DC converter 22 may be input to the primary DC-DC converter 85, etc. Also, when the main relay 84 is on and the sub power switch 82 is on, two power systems, the power system 2 and the sub battery 3, are connected in parallel to the zone ECU 1. When the main relay 84 is set to off, the sub power line 92 is electrically disconnected from the main power line 91. When the main relay 84 is set to off, the output of the isolated DC-DC converter 22 is not input to the primary DC-DC converter 85, etc. When the main relay 84 is off and the sub power switch 82 is on, power from the sub battery 3 may be supplied to the primary DC-DC converter 85.

[0060] The main relay 84 remains in the ON state under normal conditions. The main relay 84 may have a fuse function. Details of the fuse function will be described separately. In one aspect, the main relay 84 corresponds to an isolator and a backbone switch, etc. Note that the main relay 84 is an optional element and may be omitted, and the main power line 91 and the sub power line 92 may be connected by a conductive wire.

[0061] The primary DC-DC converter 85 is a circuit module that converts the voltage input from the lead line 94 into a predetermined target voltage and outputs it to the second voltage line 95. The primary DC-DC converter 85 may be a step-down DC-DC converter, for example, a synchronous rectification switching regulator. The primary DC-DC converter 85 may include a configuration that includes two switching elements connected in series, a so-called high-side switch and a low-side switch. The primary DC-DC converter 85 may also be an asynchronous rectification DC-DC converter using a diode as the low-side element. The primary DC-DC converter 85 corresponds to the first converter. In this disclosure, the semiconductor switch that forms the core of the DC-DC converter is also referred to as the core switch. In a synchronous rectification switching regulator, the core switch is the high-side switch. In an asynchronous rectification DC-DC converter, the core switch is a switching element connected in series upstream of the diode.

[0062] The primary DC-DC converter 85 may include an input terminal, an output terminal, and a control input terminal. The input terminal of the primary DC-DC converter 85 is connected to the lead line 94. The output terminal of the primary DC-DC converter 85 is electrically connected to the second voltage line 95. The control terminal of the primary DC-DC converter 85 is connected to the control unit 87. The primary DC-DC converter 85 operates based on instructions from the control unit 87. For example, the control unit 87 inputs a PWM (Pulse Width Modulation) signal having a duty cycle corresponding to the target output voltage to the control input terminal of the primary DC-DC converter 85. Voltage conversion is achieved by switching the core switch of the primary DC-DC converter 85 on / off at a cycle and frequency according to the input PWM signal.

[0063] The output voltage of the primary DC-DC converter 85 is supplied to multiple 12V loads 4β via the second voltage line 95 and the load relay 89. Hereafter, the output voltage of the primary DC-DC converter 85 may also be referred to as the primary output voltage or the primary voltage to be converted.

[0064] The secondary DC-DC converter 86 is configured to perform further voltage conversion on the output voltage of the primary DC-DC converter 85. The secondary DC-DC converter 86 has an input terminal, an output terminal, and a control input terminal. The input terminal of the secondary DC-DC converter 86 is connected to a branch line 96 that branches off from the second voltage line 95. In other words, the output voltage of the primary DC-DC converter 85 is input to the secondary DC-DC converter 86 via the second voltage line 95 and the branch line 96. The output terminal of the secondary DC-DC converter 86 is connected to a third voltage line 97. The output voltage of the secondary DC-DC converter 86 is input to the control unit 87 via the third voltage line 97. The control terminal of the secondary DC-DC converter 86 is connected to the control unit 87. The secondary DC-DC converter 86 corresponds to the second converter.

[0065] The secondary DC-DC converter 86 is a step-down DC-DC converter, similar to the primary DC-DC converter 85. The secondary DC-DC converter 86 may be a synchronous rectification switching regulator. The secondary DC-DC converter 86 may have a configuration that includes two switching elements connected in series (so-called high-side switch and low-side switch). The secondary DC-DC converter 86 may be an asynchronous rectification DC-DC converter using a diode as the low-side element. The secondary DC-DC converter 86 may also be a series regulator.

[0066] The secondary DC-DC converter 86 operates based on instructions from the control unit 87. For example, the control unit 87 inputs a PWM signal having a duty cycle corresponding to the target output voltage of the secondary DC-DC converter 86 to the control input terminal of the secondary DC-DC converter 86. Voltage conversion is achieved by switching the switching elements included in the secondary DC-DC converter 86 on and off at a cycle and frequency according to the input PWM signal. When the duty cycle is 100%, the secondary DC-DC converter 86 outputs the input voltage as is. In other words, when the duty cycle is 100%, the secondary DC-DC converter 86 transmits the output voltage of the primary DC-DC converter 85 to the third voltage line 97.

[0067] In this disclosure, the state in a DC-DC converter where the duty cycle is set to 100% is also referred to as the continuous-on state, continuous-conducting state, or no-conversion state. A DC-DC converter in the continuous-conducting state may be considered as a single conductive wire, or a conductive wire to which an LC filter is attached. The state in a DC-DC converter where the duty cycle is set to 0% is also referred to as the continuous-off state. A DC-DC converter in the continuous-off state as a whole corresponds to a single switch set to the off state. Here, continuous-on means keeping it set to on for a sufficiently long time compared to the instantaneous on in PWM control. Similarly, continuous-off means keeping it set to off for a sufficiently long time compared to the instantaneous off in PWM control.

[0068] The control unit 87 controls the multiple switches and multiple DDC converters provided in the zone ECU 1. The multiple switches provided in the zone ECU 1 include a first switch 81, a sub-power switch 82, a second switch 83, a main relay 84, and multiple load relays 89. The DDC converters include a primary DDC converter 85 and a secondary DDC converter 86.

[0069] The control unit 87 individually controls the open / closed state (i.e., on / off) of multiple switches. The control unit 87 also adjusts the primary target voltage and the secondary target voltage according to the vehicle state. The primary target voltage is the target output voltage of the primary DC-DC converter 85. The secondary target voltage is the target output voltage of the secondary DC-DC converter 86. Furthermore, the control unit 87 controls the operating state (drive / stop) of multiple loads 4 in cooperation with the communication unit 88. The control unit 87 can send stop commands or drive commands to the loads 4. The control unit 87 may also be configured to output commands to the loads 4 specifying the mode of drive. The control unit 87 can receive detection results related to the vehicle state from the vehicle state sensor 5 via the communication unit 88.

[0070] As shown in Figure 2, the control unit 87 includes a processor 871, a memory 872, an input / output circuit 873, and a bus connecting these components. The processor 871 may be a CPU (Central Processing Unit) or the like. The control unit 87 may also include an IC or FPGA instead of, or in addition to, the processor 871.

[0071] Memory 872 includes a rewritable volatile storage medium coupled to the processor 871. Memory 872 may include, for example, RAM (Random Access Memory). Memory 872 may include multiple types of non-transitional storage media. Memory 872 may include, for example, rewritable non-volatile memory such as flash memory as storage. Memory 872 stores a supply control program, which is a program executed by the processor 871. The execution of the supply control program by the processor 871 is equivalent to the execution of part or all of the supply control method. The control unit 87 may be implemented using one or more computers.

[0072] The input / output circuit 873 is hardware for the processor 871 to communicate with the communication unit 88 and to output control signals to switches. The input / output circuit 873 may also be used to output PWM signals to the primary DC-DC converter 85 and the secondary DC-DC converter 86. The input / output circuit 873 may include a drive circuit for the DC-DC converter. The drive circuit may be separated from the control unit 87 and provided between the control unit 87 and the DC-DC converter.

[0073] The input / output circuit 873 may include a circuit compatible with the communication method with the communication unit 88, etc. The input / output circuit 873 may also be an input / output port. The input / output circuit 873 may support any type of wired or wireless communication. Digital data corresponding to signals received by the input / output circuit 873 may be temporarily stored in the memory 872. The input / output circuit 873 may be understood as a communication unit in one aspect. Various data acquired sequentially by the input / output circuit 873 are stored in a temporary storage medium such as the memory 872 and used by the processor 871. Data acquired after a certain period of time may be discarded. The input / output circuit 873 or the processor 871 may have a function to generate other data based on raw data received from the communication unit 88, etc.

[0074] The memory 872 of the control unit 87 stores setting data that defines the operation of the zone ECU 1 according to the vehicle state. The setting data includes information on the voltage settings of the primary DCDC converter 85 and the secondary DCDC converter 86 for each vehicle state. Details of the setting data and the operation of the control unit 87 will be described separately.

[0075] The control unit 87 includes, as functional blocks, a state monitoring unit F1, a charge monitoring unit F2, and a load control unit F3. The state monitoring unit F1 may be a software module that determines the vehicle state based on signals input from the vehicle state sensor 5. Details of the vehicle state and the method for determining the vehicle state will be described separately.

[0076] The charge monitoring unit F2 monitors the charge state (so-called SOC: State of Charge) of the energy storage unit 90. Hereafter, the charge state will also be referred to as remaining power. The remaining power (or SOC) may be estimated based on the output voltage of the energy storage unit 90. Information such as temperature may also be used in conjunction with the estimation of the remaining power. The remaining power may be expressed as a percentage (%) with a fully charged state being 100%. The charge monitoring unit F2 corresponds to the charge state monitoring unit.

[0077] The charge monitoring unit F2 is configured to determine whether there is sufficient remaining power and whether the remaining power has decreased to a predetermined level. The state of having sufficient remaining power may be when the output voltage is above a predetermined first threshold. The state of having sufficient remaining power may be, for example, when the remaining power is 80% or more. The predetermined level corresponding to a decrease in remaining power may be, for example, when the remaining power is 30% or less. The state of having decreased remaining power may be when the output voltage is below a predetermined second threshold, which is smaller than the first threshold. The first threshold and the second threshold may be designed as appropriate.

[0078] The load control unit F3 controls the operating state (driven / stopped) of the load 4. For example, the load control unit F3 may switch the operating state of each load 4 in response to the vehicle starting, stopping, or parking. The load control unit F3 may also switch the operating state of each load 4 in response to the driver's operation on the vehicle. Driver operations on the vehicle may include at least one of pressing the hazard switch, power switch, audio switch, or air conditioning switch, pressing the brake / accelerator pedal, and changing the shift position. Driver operations on the vehicle may be detected based on the output signal of the corresponding switch / sensor. In addition, the load control unit F3 may be configured to stop the power supply to some of the loads 4 and maintain the power supply only to specific loads 4 if an abnormality occurs in the power distribution circuit 10.

[0079] The communication unit 88 is a circuit module for the control unit 87 to communicate with the load 4 and the vehicle condition sensor 5. The communication unit 88 may include a circuit suitable for the communication method with the load 4, etc. The communication unit 88 may support any type of wired or wireless communication.

[0080] The load relay 89 is a switch for switching the electrical connection state between the zone ECU 1 and the load 4. The load relay 89 may include an input terminal, an output terminal, and a control input terminal. The input terminal of the load relay 89 corresponding to the 48V load 4α is electrically connected to the first voltage line 93. That is, 48V power can be input to the input terminals of load relays 89A and 89B via the first voltage line 93. The input terminal of the load relay 89 corresponding to the 12V load 4β is electrically connected to the second voltage line 95. That is, the output voltage of the primary DC-DC converter 85 can be input to the input terminals of load relays 89K and 89L via the second voltage line 95.

[0081] The output terminal of the load relay 89 is electrically connected to the corresponding load terminal 13. The control input terminal of the load relay 89 is electrically connected to the control unit 87. The load relay 89 may be implemented using any type of semiconductor switch, such as a GaNFET.

[0082] The load relay 89 switches between a conductive state (on / off) based on a control signal input from the control unit 87. When the load relay 89 is on, the input voltage to the load relay 89 is supplied to the load 4 connected to the load relay 89. When the load relay 89 is set to off, the power supply to the load 4 connected to the load relay 89 is cut off. The load relay 89 acts as a switch for switching the power supply state to the load 4. The conductive state of the load relay 89 is controlled by the control unit 87 according to the vehicle state or the operation of the occupant.

[0083] The energy storage unit 90 is an energy storage device built into the zone ECU 1. The energy storage unit 90 may be an electric double-layer capacitor. Its electrolyte may be acetonitrile or propylene carbonate, etc. Of course, the energy storage unit 90 may be other types of capacitors. The energy storage unit 90 may be configured with multiple capacitors connected in series. The energy storage unit 90 may be an all-solid-state battery or a lithium-ion battery, etc.

[0084] The energy storage unit 90 is electrically connected to the lead line 94 and is configured to be rechargeable by the power supply voltage (48V). The energy storage unit 90 may be an energy storage device with a withstand voltage (in other words, a rated voltage) of about 50V. The energy storage unit 90 may also be an energy storage device with a rated voltage of 60V or higher, such as 100V or 200V. In that case, the energy storage unit 90 may be charged using a boost DC-DC converter that boosts the power supply voltage, as will be described separately later. If the rated voltage of the energy storage unit 90 is 60V or higher, the zone ECU 1 may be equipped with a configuration to prevent electric shock. The electrical connection state between the energy storage unit 90 and the lead line 94 may be switched by the control unit 87 using a switch or the like (not shown).

[0085] The power storage unit 90 is responsible for supplying power to maintain the functionality of the control unit 87 in the parked state. The power capacity of the power storage unit 90 may be smaller than the capacity of the sub-battery 3. For example, the capacity of the power storage unit 90 may be 50%, 25%, or 10% of the sub-battery 3. The charge state (in other words, remaining power) of the power storage unit 90 may be monitored by the control unit 87. The remaining power may be estimated, for example, based on the output voltage of the power storage unit 90. The control unit 87 may be connected to the power storage unit 90 so that it can refer to the output voltage of the power storage unit 90.

[0086] Furthermore, if the energy storage unit 90 has a configuration in which multiple capacitors are connected in series as the main body, the energy storage unit 90 may further include a voltage monitoring IC that monitors the voltage variation of each capacitor and adjusts it so as not to exceed the maximum voltage. The aforementioned charge monitoring unit F2 may be a voltage monitoring IC and may be located outside the control unit 87.

[0087] A circuit including a main power line 91, a first switch 81, a first voltage line 93, and load relays 89A and 89B corresponds to a first supply circuit for supplying power to a first type load. Load relays 89A and 89B correspond to a first load switch. A circuit including a main power line 91, a main relay 84, a sub-power line 92, a second switch 83, a lead line 94, a primary DC-DC converter 85, a second voltage line 95, and load relays 89K and 89L corresponds to a second supply circuit for supplying power to a second type load. In particular, the power path including the main power line 91, a main relay 84, a sub-power line 92, a second switch 83, and a lead line 94 corresponds to a power supply voltage line. Load relays 89K and 89L correspond to a second load switch. A circuit including a branch line 96, a secondary DC-DC converter 86, and a third voltage line 97 corresponds to a third supply circuit for supplying power to a third type load.

[0088] <Supplementary information on switches> The first switch 81 may incorporate a fuse function that automatically turns off in response to excessive voltage or current on the input or output side. The circuit providing the fuse function (hereinafter referred to as the fuse circuit) may include at least one of a current detection unit and a voltage detection unit, which are located on the input or output side of the switching element constituting the first switch 81.

[0089] The first switch 81 may be configured to be switched off when the current detection unit detects a current exceeding a predetermined value, or when the voltage detection unit detects a voltage exceeding a predetermined value. Switching off may be achieved, for example, by setting the gate voltage to 0V. The entity that turns off the first switch 81 in response to the detection of excessive voltage or excessive current may be the control unit 87, or it may be a logic circuit or IC provided separately from the control unit 87.

[0090] The fuse function described above may be implemented in at least one of the sub-power switch 82, the second switch 83, and the main relay 84. Alternatively, the fuse function may be implemented in each of the multiple load relays 89. A switch circuit with a fuse function implemented can be referred to as a circuit breaker in one aspect.

[0091] <Vehicle Status> The control unit 87 determines the vehicle status based on the signal input from the vehicle status sensor 5. The determination of the vehicle status may be performed in more detail by the status monitoring unit F1. The description of the control unit 87 as the entity that determines the vehicle status may be appropriately replaced with the status monitoring unit F1.

[0092] Vehicle states can be broadly classified into three categories: normal state, stopped state, and parked state. The normal state corresponds to the state in which the vehicle is in motion. The stopped state corresponds to the state in which the vehicle is stopped due to waiting at a traffic light, etc. In the stopped state, the shift position may remain in the drive range or neutral range, and the vehicle may be stopped by the driver's brake operation or brake hold function. The parked state is the state in which the vehicle is parked. In the parked state, the shift position may be set to the parking range, the power switch may be off, and the vehicle may be locked. The control unit 87 may determine which of the three states the current vehicle state is based on the signal from the vehicle state sensor 5.

[0093] The vehicle state may be subdivided according to the operating state of the load 4. The control unit 87 of this embodiment determines the vehicle state into seven states, from the first state to the seventh state, based on the operating state of the load 4. The first state is a state in which all or most of the load 4 connected to the zone ECU 1 are operating. The first state corresponds to the normal state. The control unit 87 may determine that the vehicle state is the first state based on the driving speed being above a predetermined value. The control unit 87 may also determine that the vehicle state is the first state based on the fact that multiple loads requiring power above a predetermined value are being driven.

[0094] The second, third, and fourth states may be subdivisions of the paused state according to the operating state of the loads. The second state is a state in which all or most of the 48V loads 4α are stopped and one or more 12V loads 4β are operating. In the second state, one or more 48V loads 4α may be operating.

[0095] The third state may be a state in which all 48V loads 4α are stopped and only low-power 12V loads are operating. Low-power 12V loads mean 12V loads 4β whose power required for operation is less than or equal to a predetermined value. In contrast, 12V loads 4β whose power required for operation is greater than a predetermined value are also referred to as high-power 12V loads in this disclosure. Low-power 12V loads are infotainment-related 12V loads 4β (e.g., audio). High-power 12V loads may be some fan motors / actuators. A state in which all 48V loads 4α are stopped but high-power 12V loads are operating may be treated as the first state. The first state is not limited to a state in which the vehicle is running, but may also include a state in which the vehicle is stopped and high-power 12V loads are being driven.

[0096] Comparing the second and third states, the difference lies in the fact that the third state is a definitive state in which all 48V loads 4α are stopped, while the second state allows some of the 48V loads 4α to operate. Furthermore, as will be described later, the second state is suitable for short-term stops, while the third state is suitable for relatively long-term stops.

[0097] The fourth state may be one in which some of the 48V loads 4α are operating and all of the 12V loads 4β are stopped. Here, "all of the 48V loads 4α" may be interpreted as all of the 48V loads 4α connected to the zone ECU 1, rather than all of the 48V loads installed in the vehicle. Similarly, here, "all of the 12V loads 4β" may be interpreted as all of the 12V loads 4β connected to the zone ECU 1, rather than all of the 12V loads installed in the vehicle.

[0098] The fifth, sixth, and seventh states may be subdivisions of the parking state according to the operating state of the loads. The fifth state is a state in which all 48V loads 4α are stopped and some 12V loads 4β are operating. The sixth state is a state in which all 48V loads 4α and all 12V loads 4β are stopped. The seventh state is also a state in which all 48V loads 4α and all 12V loads 4β are stopped, similar to the sixth state.

[0099] The operating state of the load may be the same for the sixth and seventh states. The sixth and seventh states may be distinguished by the elapsed time since parking. For example, the sixth state may be determined to be the state until a certain amount of time has elapsed since the vehicle was parked and all loads had stopped. Once a certain amount of time has elapsed since the vehicle was parked and all loads had stopped, the control unit 87 may determine that it is the seventh state.

[0100] The operating state of load 4 is determined based on the driver's instructions for driving / stopping load 4. The control unit 87 may determine a more detailed vehicle state based on the driver's operations related to the operation of load 4. Furthermore, the operating state of load 4 may also be controlled by another ECU (hereinafter referred to as an integrated ECU) that comprehensively manages the operation of load 4 installed in the vehicle from the viewpoint of equipment protection, safety, comfort, or energy management. The control unit 87 may also determine the vehicle state by communicating with the integrated ECU.

[0101] In addition, the control unit 87 may determine the vehicle state according to the elapsed time since stopping and the elapsed time since parking. The control unit 87 may determine the vehicle to be in the second state until the first hour has elapsed since the vehicle stopped. The control unit 87 may determine the vehicle to be in the third state if the first hour has elapsed since the vehicle stopped and all 48V loads 4α are stopped. The control unit 87 may determine the vehicle to be in the fourth state if the first hour has elapsed since the vehicle stopped and at least one 48V load 4α is operating.

[0102] In accordance with the determination result of the above vehicle state, the control unit 87 switches the operating state of the zone ECU 1. Therefore, the above seven vehicle states correspond to the operating state of the zone ECU 1, specifically, the setting state of the power distribution circuit 10. That is, the operating state of the zone ECU 1 can also take on seven states, from the first to the seventh state. The operating state of the zone ECU 1 corresponds to the setting of the power distribution circuit 10. In order to distinguish between the vehicle state and the operating state of the zone ECU 1, the first to seventh states relating to the vehicle may be described as the first to seventh vehicle states, and the first to seventh states relating to the operation of the zone ECU 1 may be described as the first to seventh operating states. The description of the first to seventh states relating to the following transition process may be appropriately reinterpreted as the operating state of the zone ECU 1 corresponding to the vehicle state.

[0103] Figure 3 shows an example of a state transition rule for the vehicle (and by extension, the Zone ECU 1). The vehicle / Zone ECU 1 may transition from the first state to the second state. The vehicle / Zone ECU 1 may transition from the second state to the first, third, or fourth state. The vehicle / Zone ECU 1 may transition from the third state to the second, fourth, sixth, or fifth state. The vehicle / Zone ECU 1 may transition from the fourth state to the second, third, or fifth state. The vehicle / Zone ECU 1 may transition from the sixth state to the third or fifth state. The vehicle / Zone ECU 1 may transition from the fifth state to the third, fourth, sixth, or fifth state.

[0104] The control unit 87 may determine the destination state based on the current (pre-transition) state. For example, the zone ECU 1 may be configured to proceed from the second state to the fifth state via the third or fourth state.

[0105] <Operation of the Control Unit> The control unit 87 changes the settings of the switches and DC-DC converter of the zone ECU 1 according to the result of determining the vehicle state. The setting changes may be performed according to the setting data. The vehicle state may be determined based on the input signal from the vehicle state sensor 5, or the elapsed time since the vehicle stopped / parked (hereinafter referred to as sensor information, etc.). Based on the sensor information, etc., the control unit 87 performs the transition process to the first, second, third, fourth, fifth, sixth, or seventh state.

[0106] (1) When the control unit 87 detects that the vehicle state has transitioned from another state (for example, the second state) to the first state based on sensor information, it executes the flow shown in Figure 4. Figure 4 shows the transition process to the first state (more precisely, the first operating state). The transition process to the first state generally includes S101 to S108. The control unit 87 may execute S101 if it determines, based on sensor information, that the vehicle state has transitioned to the first state.

[0107] Step S101 is the step in which the control unit 87 starts receiving 48V power from the isolated DC-DC converter 22. Step S101 may include the control unit 87 using the communication unit 88 to output a 48V output request signal to the power manager 23. The 48V output request signal is a signal requesting that the isolated DC-DC converter 22 output 48V. Based on the power manager 23 receiving the 48V output request signal from the control unit 87, the power manager 23 controls the isolated DC-DC converter 22 so that its output voltage becomes 48V. The adjustment of the DC-DC converter's output voltage may be achieved by PWM control, specifically by adjusting the duty cycle. Thus, the start of receiving 48V power may be achieved through the cooperation of the power manager 23 and the control unit 87.

[0108] The control unit 87 executes S102 after performing the procedure to start receiving 48V power from the isolated DC-DC converter 22. After transmitting the 48V output request signal, the control unit 87 monitors the input voltage from the isolated DC-DC converter 22. The control unit 87 may also execute S102 after receiving confirmation that the input voltage (in other words, the power supply voltage) from the isolated DC-DC converter 22 has reached 48V. If 48V power is already being input from the isolated DC-DC converter 22, S101 may be omitted and S102 may be executed.

[0109] S102 is the step in which the control unit 87 sets the sub-power switch 82 to ON. By setting the sub-power switch 82 to ON, power can be supplied to the power distribution circuit 10 from the sub-battery 3 as well. In other words, the power supply is duplicated. After S102, the control unit 87 executes S103.

[0110] Step S103 corresponds to setting the target output voltage (i.e., primary target voltage) of the primary DC-DC converter 85 to 15V. "Vo1" in the diagram represents the primary target voltage. From S105 onward, the control unit 87 performs PWM control on the primary DC-DC converter 85 so that its output voltage becomes 15V. Upon execution of S103, the primary DC-DC converter 85 begins to output 15V power.

[0111] In S104, following S103, the control unit 87 sets the target output voltage (i.e., secondary target voltage) of the secondary DC-DC converter 86 to 5V. "Vo2" in the diagram represents the secondary target voltage. From S106 onward, the control unit 87 performs PWM control on the secondary DC-DC converter 86 so that its output voltage becomes 5V. Upon execution of S104, the secondary DC-DC converter 86 begins to output 5V power.

[0112] Once S104 is completed, the control unit 87 executes S105. In S105, the control unit 87 turns on the load relays 89 for 48V loads. In S105, the control unit 87 may turn on all load relays 89 for 48V loads, or it may turn on only the load relays 89 connected to the 48V loads that are scheduled to operate. Once S105 is completed, S106 is executed.

[0113] In S106, the control unit 87 uses the communication unit 88 to transmit a drive instruction to the 48V load 4α. The drive instruction is an instruction signal to start operation. The 48V load 4α receives the drive instruction from the zone ECU 1 and starts operating. In S106, the control unit 87 may operate all of the 48V loads 4α, or it may operate only some of the necessary loads.

[0114] The control unit 87 may be configured to perform detailed control of the 48V load 4α. Detailed control refers to controlling specific operating modes. Detailed control may include, for example, specifying operating parameters such as target values, and specifying operating modes, or at least one of the latter.

[0115] When S106 is completed, the control unit 87 executes S107. In S107, the control unit 87 sets the load relays 89 for 12V loads to ON. In S107, the control unit 87 may set all load relays 89 for 12V loads to ON, or it may set only the load relays 89 for 12V loads that are scheduled to operate to ON. When S107 is completed, S108 is executed.

[0116] In S108, the control unit 87 uses the communication unit 88 to transmit a drive command to the 12V load 4β. The 12V load 4β receives the drive command from the zone ECU 1 and starts driving. In S108, the control unit 87 may operate all of the 12V loads 4β, or it may operate only some of the necessary loads. The control unit 87 may also be configured to perform detailed control of the 12V loads 4β. As described above, detailed control may include at least one of the following: specifying operating parameters such as target values, and specifying operating modes. When S108 is completed, the transition process to the first state is finished.

[0117] Figure 5 shows the zone ECU 1 in the first state. As shown in Figure 5, the 48V power supplied from the isolated DC-DC converter 22 is supplied to the 48V load 4α via the first switch 81. The 48V power is also input to the primary DC-DC converter 85 via the second switch 83. The primary DC-DC converter 85 steps down the 48V to 15V and supplies it to the 12V load 4β and the secondary DC-DC converter 86. The secondary DC-DC converter 86 steps down the input 15V to 5V, which is suitable for the operation of the control unit 87, and inputs it to the control unit 87.

[0118] The output of the secondary DC-DC converter 86 may be supplied to a 5V load (sensor or other IC) not shown. For example, if the load relay 89 includes an IC, the output of the secondary DC-DC converter 86 may be supplied to the IC built into the load relay 89. Also, if the zone ECU 1 includes a temperature sensor or a voltage / current monitoring IC, the output of the secondary DC-DC converter 86 may be input to those ICs / sensors as well.

[0119] In the first state, a high-power 12V load such as a fan motor can operate. Since the power loss in a motor is determined by the product of its winding resistance and current, increasing the voltage can reduce the current and, consequently, the power loss. In addition, increasing the voltage in a motor also increases the torque, which can result in higher power efficiency. For these reasons, in the first state, the primary target voltage is set to 15V, which is a relatively high voltage within the voltage range in which the 12V load 4β operates. This can increase the power efficiency of the entire system. Note that turning on the sub-power switch 82 is an optional element. The sub-power switch 82 may be off.

[0120] (2) When the second state transition control unit 87 detects that the vehicle state has transitioned from another state (for example, the first, third, or fourth state) to the second state based on sensor information, it executes the flow shown in Figure 6. Figure 6 shows the process of transitioning to the second state. The process of transitioning to the second state generally includes S201 to S208. The control unit 87 may execute S201 after determining that the vehicle state has transitioned to the second state based on sensor information.

[0121] S201 is the step in which the control unit 87 starts receiving 48V power from the isolated DC-DC converter 22. S201 may be the same as S101. After the control unit 87 has performed the process to start receiving 48V power from the isolated DC-DC converter 22, it executes S202. If 48V power is already being input from the isolated DC-DC converter 22, S201 may be omitted and S202 may be executed. After setting the sub-power switch 82 to ON in S202, the control unit 87 then executes S203. If the sub-power switch 82 is already ON, S202 may be omitted and S203 may be executed.

[0122] In S203, the control unit 87 transmits a stop instruction to the 48V load 4α using the communication unit 88. The stop instruction is an instruction signal to stop operation. In S203, the control unit 87 may stop all 48V loads 4α. In other embodiments, the control unit 87 may allow one or more 48V loads 4α to continue operating without stopping them. The control unit 87 may be configured to allow necessary loads (for example, an automatic driving ECU) to continue operating from a safety standpoint.

[0123] When S203 is completed, the control unit 87 executes S204. In S204, the control unit 87 sets the load relay 89 corresponding to the 48V load 4α that was stopped in S203 to OFF.

[0124] Next, the control unit 87 executes S205 to S206. S205 to S206 may be the same as S107 to S108. After S207, the control unit 87 executes S207 and S208. Note that the execution order of the multiple steps in the flow can be changed as appropriate. S207 to S208 may be executed before S205 to S206.

[0125] Step S207 is the step of setting the primary target voltage (Vo1) to 10V. From S207 onward, the control unit 87 performs PWM control on the primary DC-DC converter 85 so that the output voltage of the primary DC-DC converter 85 becomes 10V. After executing S207, the primary DC-DC converter 85 starts outputting 10V power. Note that if Vo1 = 10V, step S207 may be omitted.

[0126] In S208, the control unit 87 sets the secondary target voltage (Vo2) to 5V. From S208 onward, the control unit 87 PWM controls the secondary DC-DC converter 86 so that its output voltage becomes 5V. Upon execution of S208, the secondary DC-DC converter 86 begins to output 5V power. Note that if Vo2 is already 5V, S208 may be omitted. Once S208 is completed, the transition process to the second state is finished.

[0127] Figure 7 shows the zone ECU 1 in the second state. As shown in Figure 7, even in the second state, 48V power is supplied to the zone ECU 1 from the isolated DC-DC converter 22. A portion of this 48V power may be supplied to a portion of the 48V load 4α via the first switch 81. In Figure 7, the load relay 89B corresponding to load 4B is set to ON, but this is not the only option. If it is not necessary to maintain the operation of load 4B, the load relay 89B may be set to OFF.

[0128] In the second state, the 48V power supplied from the isolated DC-DC converter 22 is also input to the primary DC-DC converter 85 via the second switch 83. The primary DC-DC converter 85 steps down the 48V to 10V and supplies it to the 12V load 4β and the secondary DC-DC converter 86. The secondary DC-DC converter 86 steps down the 10V to 5V and inputs it to the control unit 87.

[0129] As mentioned above, the second state is one in which low-power 12V loads can operate, while high-power 12V loads do not. In the state where high-power 12V loads do not operate, unlike the first state, it is not necessary to set the output voltage of the primary DC-DC converter 85 to a higher level. In the second state, power efficiency can be further improved by setting the primary target voltage to a relatively low level within the range in which low-power 12V loads operate.

[0130] (3) When the transition control unit 87 detects that the vehicle has transitioned from another state (for example, the second, fourth, fifth, or sixth state) to the third state based on sensor information, it executes the flow shown in Figure 8. Figure 8 shows the transition process to the third state. The transition process to the third state generally includes S301 to S308. The control unit 87 may execute S301 after determining that the vehicle state has transitioned to the third state based on sensor information.

[0131] S301 is the step in which the control unit 87 uses the communication unit 88 to send a stop command to the 48V load 4α. In S301, the control unit 87 stops all 48V loads 4α. Once all 48V loads 4α have been stopped, in S302 the control unit 87 turns off all load relays 89 for the 48V loads. In addition to turning off all load relays 89 for the 48V loads in S302, the first switch 81 may be set to OFF.

[0132] Subsequently, in S303, the control unit 87 sets the sub-power switch 82 to OFF. As a result, the 48V power from the sub-battery 3 does not flow downstream of the sub-power switch 82. After turning off the sub-power switch 82, the control unit 87 executes S304.

[0133] Step S304 is the step of setting the output of the isolated DC-DC converter 22 to 10V. Step S304 corresponds to the step of starting to receive 10V power from the isolated DC-DC converter 22. Step S304 may include outputting a 10V output request signal to the power manager 23. The 10V output request signal is a signal requesting that the isolated DC-DC converter 22 output 10V. Based on the power manager 23 receiving the 10V output request signal from the control unit 87, the power manager 23 controls the isolated DC-DC converter 22 so that the output voltage of the isolated DC-DC converter 22 becomes 10V. Thus, the start of receiving 10V power may be achieved through the cooperation of the power manager 23 and the control unit 87. If the control unit 87 can directly control the output of the isolated DC-DC converter 22, the control unit 87 may input a PWM signal as a 10V output request signal to the isolated DC-DC converter 22.

[0134] S305 is the step in which the control unit 87 sets the primary target voltage (Vo1) to 10V. Since the input voltage of the primary DC-DC converter 85 is 10V as determined in S304, setting the primary target voltage (Vo1) to 10V is equivalent to setting the primary DC-DC converter 85 to a continuous conduction state. S305 may be the step in which the duty cycle is set to 100% and control is started to keep the high-side switch in the ON position. Upon execution of S307, the primary DC-DC converter 85 begins to output 10V as the input voltage.

[0135] In S306, following S305, the control unit 87 sets the secondary target voltage (Vo2) to 4.8V. From S306 onward, the control unit 87 PWM controls the secondary DC-DC converter 86 so that the output voltage of the secondary DC-DC converter 86 becomes 4.8V. Upon execution of S306, 4.8V power begins to be output from the secondary DC-DC converter 86. Note that if Vo2 is already 4.8V, S306 may be omitted.

[0136] Once the DC-DC converter settings have been changed, the control unit 87 executes S307 to S308. S307 to S308 is a sequence for operating the 12V load 4β that is to be operated. S307 to S308 may be the same as S107 to S108. Once S308 is completed, the transition process to the second state is finished.

[0137] Figure 9 shows the zone ECU 1 in the third state. In the third state, since it is not necessary to operate the 48V load 4α, the control unit 87, in cooperation with the power manager 23, sets the output of the isolated DC-DC converter 22 to a relatively low voltage (e.g., 10V) within the range in which the 12V load operates. The control unit 87 then sets the primary DC-DC converter 85 to a continuously conducting state. This reduces the power consumption (including switching losses, etc.) related to driving the primary DC-DC converter 85.

[0138] Furthermore, in the third state, the output voltage of the secondary DC-DC converter 86 is set to a value (4.8V) close to the minimum voltage within the operating range of the control unit 87. Here, the minimum voltage for a particular device is the lower limit of the voltage at which the control unit 87 can operate, and can also be called the lowest voltage. Power loss in a low-voltage load such as the control unit 87 (in other words, a third-type load) can be determined by the product of the IC's leakage current and voltage. By lowering the output voltage of the secondary DC-DC converter 86 to near the lowest voltage, power consumption in a third-type load can be further reduced.

[0139] (4) When the fourth state transition control unit 87 detects that the vehicle has transitioned from another state (for example, the second, third, or fifth) to the fourth state based on sensor information, it executes the flow shown in Figure 10. Figure 10 shows the transition process to the fourth state. The transition process to the fourth state generally includes S401 to S408. The control unit 87 may execute S401 after determining that the vehicle state has transitioned to the fourth state based on sensor information.

[0140] Steps S401 to S402 may be the same as steps S101 to S102. In step S401, the control unit 87 sends a 48V output request signal to the power supply system 2 and starts receiving 48V power from the isolated DC-DC converter 22. Also, in step S402, the control unit 87 sets the sub-power switch 82 to ON. Step S401 may be omitted if 48V power has already been input from the isolated DC-DC converter 22. Also, step S402 may be omitted if the sub-power switch 82 is already ON. Step S402 may include setting the first switch 81 to ON.

[0141] As a result of the above steps, when 48V is applied to the power supply voltage line, the control unit 87 executes the processes from S403 onward. Note that between S402 and S403, there may be a step to turn on the first switch 81.

[0142] Steps S403 to S404 may be the same as steps S105 to S106. In step S403, the control unit 87 sets some or all of the load relays 89 for the 48V loads to ON. In step S404, the control unit 87 uses the communication unit 88 to send a drive command to some or all of the 48V loads 4α. The 48V loads 4α start driving after receiving the drive command from the zone ECU 1.

[0143] S405 is the step of stopping the 12V load 4β. In S405, the control unit 87 sends a stop command to all 12V loads 4β via the communication unit 88 and stops them. Once the stopping control of all 12V loads 4β is complete, the control unit 87 turns off all load relays 89 for the 12V loads in S406.

[0144] Then, in S407, the control unit 87 sets the primary target voltage (Vo1) to 4.8V. From S407 onward, the control unit 87 PWM controls the primary DCDC converter 85 so that the output voltage of the primary DCDC converter 85 becomes 4.8V. Upon execution of S407, 4.8V power begins to be output from the primary DCDC converter 85. When S407 is completed, the control unit 87 executes S408.

[0145] S408 is a step in which the control unit 87 sets the secondary target voltage (Vo2) to 4.8V. Since the voltage input to the secondary DC-DC converter 86 by S407 is 4.8V, by setting the secondary DC-DC converter 86 to a continuous conduction state, the output voltage of the secondary DC-DC converter 86 can become the secondary target voltage (Vo2) of 4.8V. Therefore, S408 may be a step in which the duty cycle in the PWM control of the secondary DC-DC converter 86 is set to 100%, and the secondary DC-DC converter 86 is set to a continuous conduction state. Upon execution of S408, the secondary DC-DC converter 86 begins to output the 4.8V input from the primary DC-DC converter 85 as is. When S408 is completed, the transition process to the second state is finished.

[0146] Figure 11 shows the zone ECU 1 in the fourth state. As shown in Figure 11, in the fourth state, the zone ECU 1 receives 48V power from the isolated DC-DC converter 22 and supplies a portion of that power to the 48V load 4α. Also, since it is not necessary to operate the 12V load 4β in the fourth state, the control unit 87 lowers the output of the primary DC-DC converter 85 to 4.8V and sets the secondary DC-DC converter 86 to a continuously conducting state. This reduces the power consumption related to driving the secondary DC-DC converter 86. Furthermore, in the fourth state, the input voltage to the control unit 87 is set to a voltage (4.8V) lower than the input voltage (5V) in the first state and other states. This further reduces power consumption.

[0147] (5) When the fifth state transition control unit 87 detects that the vehicle has transitioned from another state (for example, the third, fourth, or sixth state) to the fifth state based on sensor information, it executes the flow shown in Figures 12 to 13. Figures 12 to 13 show the process of transitioning to the fifth state. The process of transitioning to the fifth state generally includes S501 to S507, S510 to S512, and S521 to S526. The control unit 87 may execute S501 after determining that the vehicle state has transitioned to the fifth state based on sensor information.

[0148] S501 is the step in which the control unit 87 starts receiving 48V power from the isolated DC-DC converter 22. S501 may be the same as S101. After the control unit 87 has performed the process to start receiving 48V power from the isolated DC-DC converter 22, it executes S502. If 48V power has already been input from the isolated DC-DC converter 22, S501 may be omitted and S502 may be executed.

[0149] Note that S501 may include setting the sub-power switch 82 to ON. In this embodiment, as an example, in the fifth state, the control unit 87 continues to set the sub-power switch 82 to OFF. In other embodiments, the control unit 87 may turn on the sub-power switch 82 in S501 or S526.

[0150] S502 is the step in which the control unit 87 uses the communication unit 88 to send a stop command to the 48V load 4α. In S502, the control unit 87 stops all 48V loads 4α. Once all 48V loads 4α have been stopped, the control unit 87 turns off all load relays 89 for the 48V loads in S503. After that, the control unit 87 sets the first switch 81 to OFF in S504. After turning off the first switch 81, the control unit 87 executes S505.

[0151] Step S505 is to set the primary target voltage (Vo1) to 10V and the secondary target voltage (Vo2) to 5V. Step S505 may be the same as, for example, steps S207 to S208. Once the operation settings for the DC-DC converter are complete, the control unit 87 executes steps S506 to S507.

[0152] S506 to S507 is a sequence for operating the 12V load 4β that should operate in the fifth state. S506 to S507 may be the same as S107 to S108. In S506, the control unit 87 turns on the load relays 89 corresponding to some or all of the 12V load 4β. Then, in S507, the control unit 87 sends a drive command to some or all of the 12V load 4β to operate them.

[0153] Once the processing up to S507 is complete, the control unit 87 starts monitoring the charge state of the energy storage unit 90 from S510. When 48V power is received from the isolated DC-DC converter 22, a portion of that power is used to charge the energy storage unit 90. The charge state of the energy storage unit 90 may be determined based on the output voltage of the energy storage unit 90. The charge state of the energy storage unit 90 may also be estimated based on the elapsed time since the start of receiving 48V power.

[0154] From S510 onward, the control unit 87 periodically executes S511. S511 is a step to determine whether the energy storage unit 90 is sufficiently charged. Whether the energy storage unit 90 is sufficiently charged can be determined based on the output voltage of the energy storage unit 90, as described above. For example, the control unit 87 may determine that the energy storage unit 90 is sufficiently charged if the output voltage of the energy storage unit 90 is 40V or higher. The threshold for determining whether the energy storage unit 90 is sufficiently charged may be 80% or 90% of the withstand voltage of the energy storage unit 90. The control unit 87 may also determine whether the energy storage unit 90 is sufficiently charged based on the elapsed time since the start of charging. The timing when S501 or 526 (described later) is executed may be considered as the start of charging. S511 is a step to determine whether a predetermined time or more has elapsed since the start of charging.

[0155] If the control unit 87 determines that the energy storage unit 90 is sufficiently charged (S511 YES), it executes the processes from S521 onwards as shown in Figure 13. On the other hand, if the control unit 87 determines that the energy storage unit 90 is not yet sufficiently charged (S511 NO), it executes S512.

[0156] Step S512 is a step in which the control unit 87 determines whether or not there has been a change in the vehicle state (including the operating state of the load). Specifically, in S512, the control unit 87 determines whether the vehicle state has transitioned to a state other than the fifth state. If a state change that leads to a transition to another state (for example, unlocking or pressing the power switch) is detected, the control unit 87 determines S512 to be positive and terminates this flow. In that case, the control unit 87 executes a transition process to another state corresponding to the detected state change. On the other hand, if no state change that leads to a transition to another state is detected in S512, the control unit 87 determines S512 to be negative and periodically executes the processes of S510 to S511.

[0157] In S521, the control unit 87 stops receiving 48V power from the isolated DC-DC converter 22. For example, the control unit 87 uses the communication unit 88 to send a stop request signal to the power manager 23 in S521. The stop request signal is a signal to stop the isolated DC-DC converter 22. Upon receiving the stop request signal, the power manager 23 stops the isolated DC-DC converter 22. The stopped state of the isolated DC-DC converter 22 may be, for example, a state where the output of the isolated DC-DC converter 22 is 0V. The stopped state of the isolated DC-DC converter 22 may also be a state where the electrical connection between the main power input terminal 11 and the isolated DC-DC converter 22 is disconnected.

[0158] In S522, following S521, the control unit 87 turns off the sub-power switch 82. If the sub-power switch 82 is already off, S522 may be omitted. With the sub-power switch 82 off and the isolated DC-DC converter 22 stopped, from S523 onward, the zone ECU 1 and one or more 12V loads 4β operate using the power stored in the energy storage unit 90. Note that S522 may include the control unit 87 turning off the main relay 84.

[0159] When the control unit 87 is operating using the power stored in the energy storage unit 90, it periodically determines in S524 whether or not there has been a change in the vehicle state. S524 may be the same process as S512. If there is no change in the vehicle state (S524 NO), the control unit 87 executes S525. On the other hand, if a change in the vehicle state is detected, this flow is terminated and a process to transition to another state is executed.

[0160] S525 is a step to determine whether the remaining power of the energy storage unit 90 has decreased. A state in which the remaining power of the energy storage unit 90 has decreased is a state in which the remaining power of the energy storage unit 90 is less than a predetermined value (for example, 8.5V). The control unit 87 may determine that the remaining power has decreased to a predetermined level when the output voltage of the energy storage unit 90 falls below a predetermined threshold. If the control unit 87 determines that the remaining power of the energy storage unit 90 has decreased (S525 YES), it executes S526. On the other hand, if it does not determine that the remaining power of the energy storage unit 90 has decreased (S525 NO), the control unit 87 periodically executes S524 to S525.

[0161] S526 is a step in which the control unit 87 starts charging the energy storage unit 90 using the isolated DC-DC converter 22. For example, in S526, the control unit 87 starts charging the energy storage unit 90 using the isolated DC-DC converter 22. Specifically, similar to S501, it starts receiving 48V power from the isolated DC-DC converter 22 by sending a 48V output request signal to the power manager 23. S526 may include the control unit 87 setting the main relay 84 to ON. While the energy storage unit 90 is charging, the sub-power switch 82 may be ON or OFF.

[0162] The power storage unit 90 may also be charged using the power from the sub-battery 3. In that case, instead of sending a 48V output request signal to the power manager 23 in S526, the sub-power switch 82 may be set to ON.

[0163] Figure 14 shows the zone ECU 1 in the fifth state. In the fifth state, since there is no need to operate the 48V load 4α, the control unit 87 turns off the first switch 81. In the fifth state, which corresponds to the parking state, basically most of the 12V load 4β does not operate. In the parking state, it is expected that ECUs / devices related to remote monitoring, software updates, or security will operate temporarily, but their power consumption is not that large. Therefore, in the fifth state, the zone ECU 1 is basically driven by the power of the energy storage unit 90, and intermittently receives 48V power from the isolated DC-DC converter 22 when the remaining power of the energy storage unit 90 decreases. Thus, in the fifth state, there is a period in which the isolated DC-DC converter 22 is stopped. By introducing a period in which the isolated DC-DC converter 22 is stopped, standby power consumption can be further reduced.

[0164] (6) When the transition control unit 87 to the sixth state detects that the vehicle has transitioned from another state (for example, the third, fifth, or seventh state) to the sixth state based on sensor information, it executes the flow shown in Figure 15. Figure 15 shows the transition process to the sixth state. The transition process to the sixth state includes S601 to S610. The control unit 87 may execute S601 after determining that the vehicle state has transitioned to the sixth state based on sensor information.

[0165] S601 is the step in which the control unit 87 uses the communication unit 88 to send a stop command to the 48V load 4α. In S601, the control unit 87 stops all 48V loads 4α. Once all 48V loads 4α have been stopped, in S602 the control unit 87 turns off all load relays 89 for the 48V loads.

[0166] Subsequently, in S603, the control unit 87 sets the sub-power switch 82 to OFF. As a result, the 48V power from the sub-battery 3 no longer flows into the power distribution circuit 10. After turning off the sub-power switch 82, the control unit 87 executes S604.

[0167] S604 is the step of stopping the 12V load 4β. In S604, the control unit 87 sends a stop command to all 12V loads 4β via the communication unit 88 and stops them. Once all 12V loads 4β have been stopped, the control unit 87 turns off all load relays 89 for the 12V loads in S605. After that, the control unit 87 turns off the first switch in S606.

[0168] In S607, following S606, the control unit 87 sets the output of the isolated DC-DC converter 22 to 10V. S607 may be the same process as S304. S607 corresponds to the step of starting to receive 10V power from the isolated DC-DC converter 22. S607 may include the control unit 87 outputting a 10V output request signal to the power manager 23. In S607, the power manager 23 controls the isolated DC-DC converter 22 so that its output voltage becomes 10V based on the 10V output request signal received from the control unit 87. Once the output adjustment of the isolated DC-DC converter 22 is complete, the control unit 87 executes S608.

[0169] S608 is a step in which the control unit 87 sets the primary target voltage (Vo1) to 4.8V. Upon execution of S608, the primary DC-DC converter 85 begins outputting 4.8V power. Once the output of the primary DC-DC converter 85 stabilizes at around 4.8V, the control unit 87 sets the secondary DC-DC converter 86 to a continuous conduction state in S609. That is, S608 sets the duty cycle in the PWM control of the secondary DC-DC converter 86 to 100%. Following S609, in S610, the control unit 87 stops the communication unit 88. This further reduces the standby dark current. With these processes, the transition to the sixth state is completed.

[0170] Figure 16 shows the zone ECU 1 in the sixth state. In the sixth state, since there is no need to operate the 48V load 4α, the control unit 87, in cooperation with the power manager 23, sets the output of the isolated DC-DC converter 22 to 10V. Although there is no need to operate the 12V load 4β, and the output of the isolated DC-DC converter 22 could be 4.8V, if the voltage conversion rate (also called voltage gain) is too small, power loss may increase. For this reason, the output of the isolated DC-DC converter 22 in the sixth state may be 10V or higher. The voltage conversion rate here refers to the ratio of the output voltage to the input voltage. A smaller voltage change rate means a larger step down. The input voltage for the isolated DC-DC converter 22 is the output voltage of the main battery 21, which can be several hundred volts or more (for example, 800V).

[0171] In the sixth state, the control unit 87 sets the secondary DC-DC converter 86 to a continuous conduction state. This reduces the power consumption related to driving the secondary DC-DC converter 86. In addition, the output voltage of the primary DC-DC converter 85 is set to 4.8V, the lower limit of the voltage at which the control unit 87 can operate, and the secondary DC-DC converter 86 is set to a continuous conduction state. By lowering the voltage level applied from the primary DC-DC converter 85 onward, the dark current in the parked state can be further reduced.

[0172] (7) When the transition control unit 87 to the seventh state detects that the vehicle has transitioned from another state (for example, the fifth or sixth state) to the seventh state based on sensor information, it executes the flow shown in Figures 17 to 18. Figures 17 and 18 show the transition process to the seventh state. The transition process to the seventh state generally includes S501 to S708, S710 to S712, and S721 to S726. The control unit 87 may execute S701 after determining that the vehicle state has transitioned to the seventh state based on sensor information.

[0173] S701 is the step in which the control unit 87 starts receiving 48V power from the isolated DC-DC converter 22. S701 may be the same as S101. After the control unit 87 has performed the process to start receiving 48V power from the isolated DC-DC converter 22, it executes S702. If 48V power is already being input from the isolated DC-DC converter 22, S701 may be omitted and S702 may be executed.

[0174] Note that S701 may include setting the sub-power switch 82 to ON. In this embodiment, the control unit 87 keeps the sub-power switch 82 OFF during the seventh state. In other embodiments, the control unit 87 may turn on the sub-power switch 82 in S701 or S726.

[0175] S702 is the step in which the control unit 87 transmits a stop command to the 48V load 4α via the communication unit 88. In S702, the control unit 87 stops all 48V loads 4α. Once all 48V loads 4α have been stopped, the control unit 87 turns off all load relays 89 for the 48V loads in S703. Then, in S704, the control unit 87 sets the first switch 81 to OFF. After turning off the first switch 81, the control unit 87 executes S705.

[0176] S705 is the step of stopping the 12V load 4β. In S705, the control unit 87 sends a stop command to all 12V loads 4β via the communication unit 88 and stops them. Once all 12V loads 4β have been stopped, the control unit 87 turns off all load relays 89 for the 12V loads in S706. Note that S705 to S706 may be executed before S702 to S704. After setting all load relays 89 to off, the control unit 87 executes S707.

[0177] S705 is a step in which the primary target voltage (Vo1) is set to 4.8V. After executing S707, 4.8V power begins to be output from the primary DC-DC converter 85. When the output of the primary DC-DC converter 85 stabilizes at around 4.8V, the control unit 87 sets the secondary DC-DC converter 86 to a continuous conduction state in S708. That is, S708 sets the duty cycle in the PWM control of the secondary DC-DC converter 86 to 100%. Once the operation settings of the DC-DC converters are complete, the control unit 87 executes S710 to S712.

[0178] In S710, the control unit 87 monitors the charge state of the energy storage unit 90. S710 may be the same as S510. After S710, the control unit 87 periodically executes S711. S711 is a step to determine whether the energy storage unit 90 is sufficiently charged. Whether the energy storage unit 90 is sufficiently charged may be determined based on the output voltage of the energy storage unit 90, as described above, or by the elapsed time since the start of charging. S711 may also be a step to determine whether a predetermined time has elapsed since the start of charging.

[0179] If the control unit 87 determines that the energy storage unit 90 is sufficiently charged (S711 YES), it executes the processes from S721 onwards as shown in Figure 18. On the other hand, if the control unit 87 determines that the energy storage unit 90 is not yet sufficiently charged (S711 NO), it executes S712.

[0180] Step S712 is a step in which it is determined whether or not there has been a change in the vehicle state. Step S712 may be the same process as in step S512. If the control unit 87 detects a change in the vehicle state, it affirms S712 and terminates this flow. The control unit 87 then executes a process to transition to another state according to the detected change in state. On the other hand, if the control unit 87 has not detected a change in state necessary to transition to another state in step S712, it negates S712 and periodically executes the processes in steps S710 to S711.

[0181] In S721, the control unit 87 stops receiving 48V power from the isolated DC-DC converter 22. For example, in S721, the control unit 87 outputs a stop request signal to the power manager 23. Then, in S722, the control unit 87 turns off the sub-power switch 82. By stopping the power supply from the two power sources, from S723 onward, the zone ECU 1 and one or more 12V loads 4β operate using the power stored in the energy storage unit 90. Note that S722 may also include setting the main relay 84 to off.

[0182] When the control unit 87 is operating using the power stored in the energy storage unit 90, it periodically determines in S724 whether or not there has been a change in the vehicle state. S724 may be the same process as S712. If there is no change in the vehicle state (S724 NO), the control unit 87 executes S725. On the other hand, if a change in the vehicle state is detected, this flow is terminated and a process to transition to another state is executed.

[0183] S725 is a step in which the control unit 87 determines whether the remaining power of the energy storage unit 90 has decreased. S725 may be the same process as S525. If the control unit 87 determines that the remaining power of the energy storage unit 90 has decreased (S725 YES), it executes S726. On the other hand, if it does not determine that the remaining power of the energy storage unit 90 has decreased (S725 NO), the control unit 87 periodically executes S724 to S725.

[0184] S726 is a step in which charging of the energy storage unit 90 is started using the isolated DC-DC converter 22. S726 may be the same process as S526. S726 may also include the control unit 87 setting the main relay 84 to ON. In other embodiments, the energy storage unit 90 may be charged using the power of the sub-battery 3. In S726, instead of sending a 48V output request signal to the power manager 23, the sub-power switch 82 may be set to ON.

[0185] Figure 19 shows the Zone ECU 1 in the seventh state. In the seventh state, which corresponds to the parking state, all 48V loads 4α and all 12V loads 4β are stopped, similar to the sixth state, so the first switch 81 is off, and the output of the primary DC-DC converter 85 may be around 5V. The output of the primary DC-DC converter 85 may be a predetermined value greater than the minimum voltage of the control unit 87 (4.8V in this example). Since the output of the primary DC-DC converter 85 is sufficiently reduced, the control unit 87 can set the secondary DC-DC converter 86 to a continuously conducting state in the seventh state. This reduces the power consumption related to driving the secondary DC-DC converter 86. Since the output voltage of the primary DC-DC converter 85 is set to a necessary and sufficiently small value, the dark current in the parking state can be further reduced.

[0186] Furthermore, the control unit 87 may shut down the communication unit 88 while it is powered by the energy storage unit 90. By shutting down the communication unit 88, the standby dark current can be further reduced. The control unit 87 may start up the communication unit 88 as the remaining power of the energy storage unit 90 decreases, enabling communication with the power manager 23.

[0187] <Setting Data> The setting data indicates the settings of the power distribution circuit 10 according to the state. The settings of the power distribution circuit 10 include the target output voltage of the DC-DC converters and the on / off status of the switches. The setting data includes setting data for the first state, setting data for the second state, setting data for the third state, setting data for the fourth state, setting data for the fifth state, setting data for the sixth state, and setting data for the seventh state. For example, the setting data for the first state indicates that Vo1 = 15V, Vo2 = 5V, the first switch 81 is on, the sub-power switch 82 is on, the second switch 83 is on, all load relays 89 are on, and the target output voltage of the isolated DC-DC converter 22 is 48V. The setting data for the second state indicates that Vo1 = 10V, Vo2 = 5V, the first switch 81 is on, the sub-power switch 82 is on, the second switch 83 is on, some load relays 89 are on, and the target output voltage of the isolated DC-DC converter 22 is 48V. The setting data for the third state indicates that Vo1 = 10V, Vo2 = 4.8V, the first switch 81 is on (or off), the sub-power switch 82 is off, the second switch 83 is on, some load relays 89 are on, and the target output voltage of the isolated DC-DC converter 22 is 10V. The setting data for other states may also be the data shown in Figures 9, 1, 14, 16, 19, etc., and their specific explanation is omitted.

[0188] <Configuration of the Energy Storage Unit> The energy storage unit 90 may include a boost DC-DC converter 902 positioned between the main unit 901, which is a capacitor / battery, and the lead wire 94, as shown in Figure 20. The voltage output terminal of the boost DC-DC converter 902 is electrically connected to the positive terminal of the main unit 901. The voltage input terminal of the boost DC-DC converter 902 is electrically connected to the lead wire 94. The boost DC-DC converter 902 charges the main unit 901 by boosting the voltage input from the lead wire 94.

[0189] The boost DC-DC converter 902 may be controlled by the control unit 87. The output voltage of the boost DC-DC converter 902 may be set to a value that is the same as or a predetermined amount smaller than the withstand voltage (also called the rated voltage) of the main unit 901. If the main unit 901 is a capacitor with a withstand voltage of 150V, the output voltage of the boost DC-DC converter 902 may be set to any value of 150V or less.

[0190] The control unit 87 may drive the boost DC-DC converter 902 and charge the main unit 901 while the isolated DC-DC converter 22 is outputting 48V. Lines S101, S201, S401, S501, and S701 may include starting to drive the boost DC-DC converter 902. In one embodiment, the control unit 87 may set the boost DC-DC converter 902 to a continuously off state (i.e., stopped state) except in the charging mode. The charging mode is a mode for charging the main unit 901 (energy storage unit 90), and specifically refers to a state in which the isolated DC-DC converter 22 is operating in the fifth state, the seventh state, etc.

[0191] Furthermore, the energy storage unit 90 may include a step-down DC-DC converter 903 positioned between the main unit 901 and the lead wire 94. The step-down DC-DC converter 903 steps down the output voltage of the main unit 901 to 10V and outputs it. The output terminal of the step-down DC-DC converter 903 may be electrically connected to the lead wire 94 via a diode 904. The anode of the diode 904 is electrically connected to the output terminal of the step-down DC-DC converter 903, and the cathode is electrically connected to the lead wire 94. The output of the step-down DC-DC converter 903 may also be controlled by the control unit 87.

[0192] The control unit 87 may keep the step-down DC-DC converter 903 running regardless of the vehicle status. As long as the voltage applied to the lead line 94 is higher than 10V, the step-down DC-DC converter 903 does not supply power to the lead line 94. Therefore, the step-down DC-DC converter 903 operates intermittently at very long intervals, and power loss can be kept within an acceptable range. Furthermore, with the configuration that keeps the step-down DC-DC converter 903 running, even if noise / malfunctions or user operations occur that cause the power supply voltage (Vin) to suddenly drop below 10V, the 10V voltage continues to be supplied from the energy storage unit 90. Thus, the stability of the voltage downstream of the lead line 94 can be improved. When the control unit 87 operates the step-down DC-DC converter 903, it may also set the step-up DC-DC converter 902 to a continuously off state.

[0193] In one embodiment, the control unit 87 may set the step-down DC-DC converter 903 to a continuously off state (i.e., a stopped state) when in non-discharge mode. Discharge mode is a state in which the control unit 87 and the like operate using the power of the energy storage unit 90, and can be understood as the state in which S523 to S525 and S723 to S725 are executed. Non-discharge mode is a state other than discharge mode and includes the charging mode described above. The control unit 87 may set the step-down DC-DC converter 903 to a continuously off state when in non-discharge mode, but only if the step-down DC-DC converter 903 is configured to quickly return from a stopped state to a 10V output state in response to a voltage drop in the lead line 94.

[0194] In addition, the main unit 901 and the lead wire 94 may be connected via a charge / discharge switch 905. The charge / discharge switch 905 may be a semiconductor switch, and its open / closed state is controlled by the control unit 87. The control unit 87 sets the charge / discharge switch 905 to OFF except in the fifth and seventh states. In the charging mode of the fifth and seventh states, the control unit 87 charges the main unit 901 by turning on the charge / discharge switch 905 while keeping the second switch 83 ON. Also, in the discharging mode of the fifth and seventh states, the control unit 87 turns off the second switch 83 and turns on the charge / discharge switch 905. The same effect as described above can be obtained with this type of control as well.

[0195] The configurations shown in Figure 21 and Figure 20 may be combined as appropriate. For example, the step-down DC-DC converter 903 and diode 904 shown in Figure 20 may be replaced with a charge / discharge switch 905. In other words, the main body 901 shown in Figure 21 may be connected to the lead line 94 via a step-up DC-DC converter 902 provided in parallel with the charge / discharge switch 905.

[0196] <Effects> The Zone ECU 1 generates multiple types of voltages according to the type of load and supplies power to each load. For example, the Zone ECU 1 generates three types of voltages: a voltage for the first type load, a voltage for the second type load, and a voltage for the third type load including the control unit 87. Since the Zone ECU 1 can manage the supply of power to multiple types of loads with different operating voltage ranges, the power network in the vehicle can be simplified.

[0197] The control unit 87 included in the Zone ECU 1 changes the target output voltage of the primary DDC converter 85 according to the vehicle state. For example, in situations (also called scenes or scenarios) where a high-power 12V load such as a fan motor is operating, the control unit 87 sets the output voltage of the primary DDC converter 85 to 15V. On the other hand, in situations where only a low-power 12V load is operating, the control unit 87 sets the output voltage of the primary DDC converter 85 to 10V or less. In this way, the control unit 87 sets the output voltage of the primary DDC converter 85 to a voltage that matches the vehicle state and, consequently, the operating state of the on-board load. This can reduce power loss or excessive power supply, and consequently increase the energy efficiency of the vehicle.

[0198] Furthermore, the control unit 87 also changes the target output voltage of the secondary DC-DC converter 86 according to the vehicle state. For example, in a vehicle state where only low-voltage loads such as the control unit 87 are operating, the output voltage of the secondary DC-DC converter 86 is set to a voltage at which the low-voltage load can operate. As mentioned above, the power loss in low-voltage loads such as the control unit 87 can be determined by the product of the IC's leakage current and voltage. By adjusting the output of the secondary DC-DC converter 86 as described above, the power consumption in the vehicle can be further reduced.

[0199] Furthermore, the Zone ECU 1 described above is equipped with two DC-DC converters connected in series, and is configured to step down the power supply voltage in two stages. With this configuration, the voltage conversion rate of a single DC-DC converter can be reduced, and consequently, energy efficiency can be increased. In addition, by providing multiple DC-DC converters, it is possible to generate separate voltages for the second type of load and the third type of load. Since it becomes possible to generate voltages precisely according to the voltage requirements of the load, overall energy efficiency can be improved.

[0200] Furthermore, the control unit 87 sets some of the DC-DC converters to a continuously conductive state under certain vehicle conditions. This configuration can reduce power loss associated with switching and potentially improve energy efficiency.

[0201] Furthermore, generally speaking, when a load is connected to a power source, a dark current can flow through the load even when it is not operating. To address this issue, the control unit 87 sets the load relay 89, which is connected to a stopped load determined according to the vehicle state, to an interrupted state. With this configuration, the dark current in vehicle states where multiple loads are stopped (e.g., parked state) can be reduced. Here, a stopped load refers to a load that has stopped operating and does not require power supply. In contrast, a load that is operating or needs to operate is also referred to as an operating load or required load in this disclosure.

[0202] When the vehicle is in a specific low-load state, the control unit 87 transmits a voltage reduction request signal to the power supply system 2 using the communication unit 88. The voltage reduction request signal is a signal requesting that the output voltage of the isolated DC-DC converter 22 be reduced. The voltage reduction request signal is, for example, a 10V output request signal. The voltage reduction request signal may include a signal requesting that the output voltage be set to 0V in one phase. In other words, the voltage reduction request signal may include a stop request signal. By reducing the power supply voltage itself in this low-load state, the amount of voltage reduction in the primary DC-DC converter 85 or the secondary DC-DC converter 86 can be reduced, further reducing energy loss.

[0203] In this context, a low-load state refers to a state in which the power required is less than that of a normal state (for example, less than a quarter). A low-load state means a vehicle state in which the operating load is low in a given phase. A low-load state may be a state in which at least all 48V loads 4α are stopped, and the high-power 12V loads are also stopped. A specific low-load state may include, for example, at least one of the third, fifth, sixth, and seventh states.

[0204] Furthermore, the control unit 87, in cooperation with the power supply system 2, stops the isolated DC-DC converter 22 in certain parking conditions. When the zone ECU 1 is not receiving power from the isolated DC-DC converter 22, it is driven using the power stored in the energy storage unit 90. The control unit 87 monitors the remaining power in the energy storage unit 90 and resumes power supply from the isolated DC-DC converter 22 as the remaining power decreases.

[0205] In this configuration, where the zone ECU 1 includes a power storage unit 90, the isolated DC-DC converter 22 can be intermittently stopped and started. By introducing a period during which the isolated DC-DC converter 22 is stopped, power consumption in the parked state can be further reduced. The specific parking state may include the fifth and seventh states.

[0206] <Supplementary information on circuit configuration> A main power switch 8A may be placed between the main power input terminal 11 and the first switch 81, as shown in Figure 22. If the main power switch 8A is placed, the first switch 81 may be omitted. The sub power switch 82 is not mandatory and may be omitted. The second switch 83 is also an optional element and may be omitted. The main relay 84 is also not mandatory and may be omitted.

[0207] The number of DC-DC converters in Zone ECU 1 is not limited to two. Zone ECU 1 may have only one DC-DC converter, or it may have three or more. The DC-DC converters in Zone ECU 1 will also be referred to as built-in DC-DC converters below.

[0208] The zone ECU 1 may include load control means instead of, or in addition to, the load relay 89. The load control means may be a control circuit for controlling the power supply to the load. There may be one or more loads connected to a single load control means. The load control means may be configured to supply power to the load when an enable signal is input from the control unit 87, and to stop supplying power to the load when a disable signal is input from the control unit 87. The load control means may also have a function for detailed control of the load. The load control means may partially perform the role of the communication unit 88.

[0209] <48V Power Reception Control> In the above, the reception / cutoff of 48V power was switched by communication with the power manager 23, but the reception / cutoff of 48V power may also be switched using a switch provided on the zone ECU 1. For example, if 48V power from the isolated DC-DC converter 22 is not needed, the main relay 84 and the first switch 81 may be set to OFF. Furthermore, if the zone ECU 1 is equipped with a main power switch 8A, the control unit 87 may switch the reception / cutoff of power from the isolated DC-DC converter 22 by turning the main power switch 8A on and off.

[0210] In these cases, the zone ECU 1 does not need to stop the isolated DC-DC converter 22. Also, the control unit 87 does not need to communicate with the power manager 23 to stop / restart the 48V power supply. The zone ECU 1 may be able to control the stopping / restarting of the 48V power supply on its own. However, as in the above configuration, if 48V power is not needed, stopping the isolated DC-DC converter 22 can be expected to provide further power saving effects.

[0211] <Supplement to Vehicle Status> The control unit 87 may determine the appropriate operating state of Zone ECU 1 according to the operating state of the load 4 under the management of Zone ECU 1, regardless of the state of the vehicle's drive system, such as when it is driving, stopped, or parked. The above vehicle status may be replaced with load status. The control unit 87 may, for example, determine the state to transition to according to the combination of loads that are in operation or require operation.

[0212] If Zone ECU 1 corresponds to the sixth state, the seventh state is not mandatory and may be omitted. Also, if Zone ECU 1 corresponds to the seventh state, the sixth state is not mandatory and may be omitted. The second, third, fourth, and part of the fifth state may be omitted. The number of states that Zone ECU 1 corresponds to may be less than five or eight or more.

[0213] <Vehicle Status Determination Body> The control unit 87 may be configured to execute transition processing to the first, second, third, fourth, fifth, sixth, or seventh state based on instructions from the higher-level ECU 6. The control unit 87 may be connected to the higher-level ECU 6 in place of / in addition to the vehicle status sensor 5, as shown in Figure 23.

[0214] In Figure 23, the circuit including the first switch 81, sub-power switch 82, second switch 83, main relay 84, primary DC-DC converter 85, secondary DC-DC converter 86, and multiple load relays 89 is shown as a simplified power distribution circuit 10. Also, the sub-battery 3 is not shown in Figure 23. The sub-battery 3 is not a required element but may be considered an optional element. Accordingly, the configuration of the zone ECU 1 related to the sub-battery 3, such as the sub-power switch 82, may also be considered an optional element.

[0215] The higher-level ECU 6 shown in Figure 23 is a higher-level ECU than the zone ECU 1. The higher-level ECU 6 is responsible for power management throughout the entire vehicle. The higher-level ECU 6 may be an ECU (also called a central ECU) that integrally controls multiple zone ECUs 1 installed in the vehicle. The higher-level ECU 6 may also be a mobility controller, HPC, battery management ECU, autonomous driving ECU, ADAS-ECU, etc. The higher-level ECU 6 corresponds to the power management device.

[0216] In one embodiment, the higher-level ECU 6 may determine the vehicle state based on sensor information, etc. In other words, the higher-level ECU 6 may have a function equivalent to the state monitoring unit F1. When the higher-level ECU 6 detects a change in the vehicle state, it transmits a state transition instruction signal to the zone ECU 1. The state transition instruction signal is a signal that instructs the zone ECU 1 to transition to a specified state. The state transition instruction signal may include transition destination state information, which is information indicating the state to which the transition will occur.

[0217] The zone ECU 1, as in the previous embodiment, holds setting data including a target output voltage according to the vehicle state and on / off settings for each load. Based on receiving a state transition instruction signal from the higher-level ECU 6, the zone ECU 1 executes a transition process to the instructed state. That is, steps S101 and S201 described above may be executed based on receiving a state transition instruction signal from the higher-level ECU 6. This configuration also produces the same effects as the embodiment described above. The vehicle state sensor 5 or the higher-level ECU 6 corresponds to other in-vehicle devices.

[0218] In other embodiments, the zone ECU 1 does not necessarily need to hold setting data. The higher-level ECU 6 may communicate with the control unit 87, and the control unit 87 may change the settings of the power distribution circuit 10 based on instructions from the higher-level ECU 6. The changes to the settings of the power distribution circuit 10 may include changing the output voltage of the built-in DC-DC converter, switching switches on and off, and controlling load relays.

[0219] In yet another embodiment, when the zone ECU 1 detects a change in state through its own state monitoring function, it may, based on its own judgment, provisionally change the settings of the power distribution circuit 10 to settings that match the latest vehicle state. In other words, it may provisionally perform a state transition process similar to that of the above embodiment. After that, the zone ECU 1 may report the state, such as power balance and temperature, to the higher-level ECU 6.

[0220] For example, when the zone ECU 1 changes the settings of the power distribution circuit 10, it may report the power balance, etc., to the higher-level ECU 6 after a certain period of time has elapsed since the change. The power balance may be data showing the power received from the power supply system 2 and the power output to the load 4. The power received from the power supply system 2 may be estimated based on the input voltage and input current. The power output to the load 4 may be estimated based on the output voltage and output current to each load 4. The output current may be measured using a current detection circuit provided in the load relay 89.

[0221] The higher-level ECU 6 may output a setting change command to the zone ECU 1 based on the report from the zone ECU 1, and optimize the settings of the power distribution circuit 10. The higher-level ECU 6 may also be configured to adjust the output voltage of the power supply system 2 through communication with the power manager 23.

[0222] <Supplementary information on the power supply system> As shown in Figure 24, the power supply system 2 may include a first isolated DC-DC converter 22A and a second isolated DC-DC converter 22B as the isolated DC-DC converter 22. The power supply system 2 may also include an output switching unit 24 for switching between the isolated DC-DC converters 22 that are electrically connected to the main power input terminal 11.

[0223] The first isolated DC-DC converter 22A is an isolated DC-DC converter 22 that outputs 48V. The second isolated DC-DC converter 22B is an isolated DC-DC converter 22 that outputs a lower voltage (for example, 10V) than the first isolated DC-DC converter 22A. Both the first isolated DC-DC converter 22A and the second isolated DC-DC converter 22B are electrically connected to the output of the main battery 21, and the high-voltage power of the main battery 21 is input to them. The output terminals of the first isolated DC-DC converter 22A and the output terminals of the second isolated DC-DC converter 22B are connected to the output switching unit 24.

[0224] The output switching unit 24 may be implemented using switching elements such as IGBTs or MOSFETs, or other types of switching elements. The output switching unit 24 is connected to the power manager 23, and its connection state is switched based on control signals input from the power manager 23.

[0225] The power manager 23 shown in Figure 24 determines whether to drive the first isolated DC-DC converter 22A or the second isolated DC-DC converter 22B depending on the vehicle status. The power manager 23 may also select the isolated DC-DC converter 22 to drive based on a request from the control unit 87 or the higher-level ECU 6. The power manager 23 controls the output switching unit 24 so that the output of the selected isolated DC-DC converter 22 is electrically connected to the main power input terminal 11. For example, when the power manager 23 operates the first isolated DC-DC converter 22A, it switches the connection state of the output switching unit 24 so that the output of the first isolated DC-DC converter 22A is connected to the main power input terminal 11.

[0226] In this configuration, where the power supply system 2 is equipped with an isolated DC-DC converter 22 for 48V and an isolated DC-DC converter 22 for 12V, the power manager 23 may use them interchangeably depending on the situation. With this configuration, the output voltage range that one isolated DC-DC converter 22 must support is reduced, allowing for miniaturization or simplification of each isolated DC-DC converter 22. Furthermore, if one of the isolated DC-DC converters 22 malfunctions, the other can be used to maintain power supply to some of the loads 4. In other words, the robustness against converter failures within the power supply system 2 can also be increased.

[0227] (Second Embodiment) In the zone ECU 1 of the second embodiment of the present disclosure shown in Figure 25, some of the multiple load relays 89 (see also Figure 1) that were provided on the first voltage line 93 and the second voltage line 95 in the first embodiment are omitted.

[0228] More specifically, a load relay 89A is provided in the section of the first voltage line 93 connecting the first switch 81 and the load terminal 13A. On the other hand, a load relay 89 is not provided in the section of the first voltage line 93 connecting the first switch 81 and the load terminal 13B.

[0229] Similarly, a load relay 89K is provided in the section of the second voltage line 95 connecting the primary DC-DC converter 85 and the load terminal 13K. On the other hand, a load relay 89 is not provided in the section of the second voltage line 95 connecting the primary DC-DC converter 85 and the load terminal 13L.

[0230] When the control unit 87 lowers the target output voltage of the primary DC-DC converter 85 according to the vehicle status in the second to seventh states, etc., it cooperates with the communication unit 88 and sends a stop command to the 48V load 4α and the 12V load 4β. In addition, the control unit 87 sets the load relays 89A and 89K to OFF.

[0231] Here, the loads 4 connected to the load terminals 13 (13A, 13K) whose power supply is switched on and off by the load relay 89 may be configured without communication functions with the communication unit 88 and on / off switching functions. These loads 4 (48V load 4A, 12V load 4K) are started when the load relay 89 is switched on and stopped when the load relay 89 is switched off.

[0232] On the other hand, the 48V load 4B and the 12V load 4L are loads 4 connected to the omitted load terminals 13 (13B, 13L) of the mechanical load relay 89. The control unit 87, for example in the fourth state, lowers the target output voltage of the primary DC-DC converter 85, and in cooperation with the communication unit 88, changes the operating state of the 48V load 4B to a low power consumption state. Similarly, the control unit 87, for example in the second, third, fifth states, etc., lowers the target output voltage of the primary DC-DC converter 85, and in cooperation with the communication unit 88, changes the operating state of the 12V load 4L to a low power consumption state.

[0233] The control unit 87 outputs instructions to the 48V load 4B and 12V load 4L, such as an instruction to restrict startup or an instruction to set the enable signal to "FALSE" (stop instruction), in order to transition to a low power consumption state. Based on the stop instruction from the control unit 87, the 48V load 4B and 12V load 4L, which have transitioned to a low power consumption state, continue to operate at a voltage close to the lower limit of the range in which operation is guaranteed.

[0234] The control unit 87 transitions the load 4, which is in a low-power state, to a normal state by sending a start signal or setting the enable signal to "TRUE". When transitioning from a low-power state to a normal state, the startup time of the load 4 can be shortened compared to starting the load 4 by switching the load relay 89 ON.

[0235] The low-power state is an operating state of the load 4 in which power consumption is lower compared to the normal state before the target output voltage of the primary DC-DC converter 85 is lowered. In the low-power state, the dark current and current consumption of the connected circuit may be reduced compared to the normal state used in the first state, etc. The low-power state includes multiple modes such as standby state, sleep state, and deep sleep state. The low-power state may also include a stopped state (start-off state) of the load 4.

[0236] Specifically, in the case of load 4, which has internal arithmetic processing circuits such as a microcontroller and FPGA (Field-Programmable Gate Array), low-power states include clock down mode, stop mode, and clock gating. Clock down mode is an operating mode that reduces the power consumption of the arithmetic processing circuit by lowering the clock frequency. Clock down is also called downclocking or underclocking. Stop mode is a temporary stop state of load 4. In stop mode, it is possible to further reduce power consumption by completely stopping the clock supply to the arithmetic processing circuit and peripheral devices.

[0237] Clock gating is a dynamic control mechanism that stops the clock supply to a specific circuit block in load 4 when that block is idle. With clock gating, the clock continues to be supplied only to necessary parts, such as FPGAs, while the clock supply to unnecessary parts, and consequently their switching operations, are stopped. Unlike stop mode, clock gating allows necessary functions to continue operating without shutting down the entire system.

[0238] Furthermore, in the case of load 4, which incorporates an Intelligent Power Device (IPD) equipped with a charge pump, a state in which the boost voltage for turning on the high-side FET (hereinafter referred to as the charge pump voltage) is reduced may be considered a low-power state. In pre-drivers and bridge drivers equipped with charge pumps, a low-power state with a reduced charge pump voltage may also be implemented.

[0239] In detail, a high-side FET (mainly an N-channel FET) can conduct current when a higher voltage is applied to the gate than to the source. As the voltage difference between the gate and source increases, the on-resistance between the drain and source (Drain-Source ON-resistance, hereafter referred to as RDS) decreases. Therefore, when a large current flows through a high-side FET, setting a high charge pump voltage and low RDS can reduce heat generation and voltage drop associated with losses. On the other hand, when a small current flows, the loss reduction achieved by lowering the charge pump voltage within an acceptable range may be greater than the loss reduction achieved by increasing the charge pump voltage and reducing RDS. Therefore, a state where the charge pump voltage is lower than the normal state is considered a low-power state.

[0240] (Summary of the second embodiment) In the second embodiment described above, the output voltage of the primary DC-DC converter 85 is set to match the operating state of the vehicle load. As a result, the same effects as in the first embodiment can be achieved, and the energy efficiency in the vehicle can be improved.

[0241] In addition, the control unit of the second embodiment changes the operating state of the load 4 to a low-power consumption state when the target output voltage of the primary DC-DC converter 85 is lowered. With this configuration, even a load 4 that is not connected to the load relay 89, in other words, a load 4 that cannot be shut off by the load relay 89, can have its power consumption reduced in accordance with the change to lower the target output voltage.

[0242] Furthermore, the control unit 87 can start up the load 4, which has transitioned to a low power consumption state, in a shorter startup time than the load 4, which has had its power cut off by the load relay 89. However, unlike the load 4, which has its power cut off by the mechanical load relay 89, the power supply to the load 4, which is not connected to the load relay 89, cannot be reduced to zero. Dark current and leakage current flow through the load 4, which has been stopped by a stop command alone. In the operating section of the load 4, power consumption increases in proportion to the voltage. Also, in the resistive components such as pull-up resistors and pull-down resistors in the operating section, power consumption increases in proportion to the square of the voltage.

[0243] However, in the second embodiment, the supply voltage to the load 4, which has transitioned to a low-power state, is reduced to a voltage close to the lower limit within the operating range. Therefore, even in a circuit configuration in which the load relay 89 is omitted, the power consumption during standby, which is considered a low-power state, can be reduced.

[0244] Furthermore, in the second embodiment, the low-power consumption state of load 4 includes states corresponding to the level of standby power, such as sleep state and deep sleep state. By providing a deep sleep state and further limiting the functions that operate, the power consumption of load 4 can be reduced even further. In addition, the lower the power consumption, the smaller the line drop (voltage drop) of the power supply voltage. As a result, the target output voltage can be lowered to match a lower voltage within the operating range of load 4, thus achieving even greater energy savings.

[0245] (Third Embodiment) In the power supply system according to the third embodiment of the present disclosure shown in Figure 26, a plurality of zone ECUs 1, 201, 301 and a higher-level ECU 6 are connected to a CAN® bus 7. In the power supply system, instructions for controlling the zone ECUs 1, 201, 301 and load 4, etc., according to the vehicle status are transmitted and received via CAN communication.

[0246] Multiple zone ECUs 1, 201, and 301 have substantially the same configuration. In the third embodiment, for convenience, each zone ECU 1, 201, and 301 will be referred to as the first zone ECU 1, the second zone ECU 201, and the third zone ECU 301, respectively. Power is supplied to the second zone ECU 201 from the main battery 21. Power is supplied to the third zone ECU 301 from the sub-battery 3. Note that the second zone ECU 201 may be connected to the sub-battery 3 in place of or together with the main battery 21, and receive power from the sub-battery 3. Similarly, the third zone ECU 301 may be connected to the main battery 21 in place of or together with the sub-battery 3, and receive power from the main battery 21. In addition, the multiple zone ECUs 1, 201, and 301 do not necessarily have to be connected in parallel to the main battery 21 and the sub-battery 3. For example, multiple zone ECUs 1, 201, and 301 may be connected in series to a power line to which an isolated DC-DC converter 22 is connected at one end and a sub-battery 3 is connected at the other end.

[0247] As described above, the higher-level ECU 6 is the central ECU and mobility controller, etc. The higher-level ECU 6 is connected to both the main battery 21 and the sub-battery 3 so as to be able to supply power. The higher-level ECU 6 has the function of detecting changes in the vehicle state and transmitting state transition instruction signals to each zone ECU 1, 201, and 301. Based on the receipt of the state transition instruction signal from the higher-level ECU 6, each zone ECU 1, 201, and 301 executes the transition process to the instructed state.

[0248] The CAN bus 7 is composed of two twisted-pair wires. By connecting numerous nodes to the CAN bus 7, a distributed serial communication network within the vehicle is constructed. In addition to zone ECUs 1, 201, 301 and the higher-level ECU 6, the CAN bus 7 is connected as nodes to the power manager 23, vehicle condition sensor 5, and 48V load system or 12V load system ECUs (hereinafter referred to as load ECU 104). The power manager 23 has the function of a BMS (Battery Management System) that manages the main battery 21.

[0249] The vehicle condition sensor 5 includes a vehicle condition sensor 5a linked to the first zone ECU 1, a vehicle condition sensor 5b linked to the second zone ECU 201, and a vehicle condition sensor 5c linked to the third zone ECU 301. Furthermore, a vehicle condition sensor 5d linked to the higher-level ECU 6 may also be included in the vehicle condition sensor 5.

[0250] The load ECU 104 corresponds to either a 48V load 4α or a 12V load 4β. The load ECU 104 includes load ECU 104b, which is linked to the second zone ECU 301, load ECU 104c, which is linked to the third zone ECU 203, and load ECU 104d.

[0251] The CAN bus 7 enables communication between nodes via communication frames. A communication frame is the smallest unit of information used when sending and receiving data using a communication protocol. A communication frame consists of multiple fields, such as an identifier, data length, and data body. Communication frames are generated by zone ECUs 1, 201, 301, the higher-level ECU 6, and the load ECU 104, and provided to other ECUs in the vehicle network via the CAN bus 7. The communication frames flowing through the CAN bus 7 are CAN frames based on the CAN communication protocol.

[0252] The communication frame contains an NM (Network Management) frame (see Figure 27) used for startup management and power management of the upper-level ECU 6, zone ECUs 1, 201, 301, and load ECU 104. The NM frame records information such as the conduction and disconnection of each load relay 89, the startup and shutdown of each load 4 (load ECU 104), and the output voltage of each DC-DC converter. As an example, the NM frame includes a switch register 71 and a level register 72 as signals indicating voltage settings according to the vehicle status.

[0253] The switch register 71 is a bit sequence that indicates the on and off states of the power switches, such as the primary DDC converter 85 and the secondary DDC converter 86. In the switch register 71, the on and off states of all power switches included in the zone ECU 1 are individually defined. In the data field of the switch register 71, "0" indicates that the power switch (power supply) is off, and "1" indicates that the power switch (power supply) is on. The length of the data field may be changed according to the number of power conversion units (power switches) provided in the zone ECU 1.

[0254] As an example, "12V1" shown in Figure 27 is a bit indicating the on and off state of the primary DC-DC converter 85. "12V2" is a bit indicating the on and off state of a power conversion unit separate from the primary DC-DC converter 85, for example, a power conversion unit connected to the first voltage line 93 that converts an input voltage of 48V to an output voltage of 12V. "5V1" is a bit indicating the on and off state of the secondary DC-DC converter 86. "5V2" is a bit indicating the on and off state of a power conversion unit separate from the secondary DC-DC converter 86, a power conversion unit that converts an input voltage such as 48V or 12V to an output voltage of 5V.

[0255] The level register 72 defines the target output voltage of each power conversion unit (power switch) in more detail. The level register 72 is a bit sequence subordinate to the switch register 71 and is set for each power switch whose on and off states are defined in the switch register 71. In the data field of the level register 72, the voltage value to be used as the target output voltage for the power switch is indicated by a bit sequence. In the data field of the level register 72, the target output voltage may be indicated in a format that shows a positive voltage from a specified reference or lower limit voltage. In addition, the data field of the level register 72 associated with power switches (12V2 and 5V1, etc.) defined as off in the switch register 71 may record a bit sequence indicating the target output voltage for past on settings or for the next on switch.

[0256] In the first zone ECU 1 shown in Figure 26, the communication unit 88 is configured to send and receive NM frames with other in-vehicle devices such as the second zone ECU 201, the third zone ECU 301, and the higher-level ECU 6. The control unit 87 determines the target output voltages of the primary DCDC converter 85 and the secondary DCDC converter 86 based on signals such as the switch register 71 and the level register 72 included in the NM frame. The control unit 87 outputs instruction signals to the DCDC converters 85, 86, the load relay 89, and the load 4 to correspond to the target output voltages determined based on the information in the NM frame. The control unit 87 may also be capable of power management based on information from the vehicle condition sensor 5 associated with the first zone ECU 1, in addition to power management based on the information in the NM frame.

[0257] The first zone ECU 1 generates an NM frame to be transmitted to the power manager 23, the higher-level ECU 6, and other in-vehicle devices such as other zone ECUs 201 and 301. By transmitting the NM frame to other in-vehicle devices, the first zone ECU 1 can instruct the power system 2, the higher-level ECU 6, and the other zone ECUs 201 and 301 to switch between on and off states and change voltages, similar to the load 4 (see Figure 25) that is not connected to the load relay 89. In addition, by transmitting the NM frame, the first zone ECU 1 can instruct the load ECU 104 associated with the other zone ECUs 201 and 301, in other words, the load ECU 104 belonging to other zones, to switch between on and off states and change operating voltage (operating state).

[0258] The upper-level ECU 6 and the other zone ECUs 201 and 301 generate and transmit NM messages to other in-vehicle devices, similar to the first zone ECU 1. This makes it possible for the power supply system to selectively start and stop only the loads and load ECUs 104 belonging to a predetermined specific cluster from among the loads 4 and load ECUs 104 distributed across multiple zones. In addition, it becomes possible to operate multiple loads 4 and load ECUs 104 belonging to a specific cluster in the same low-power state.

[0259] Here, instead of the CAN bus 7, a communication line (communication cable) that supports a communication protocol different from CAN may be used to construct the in-vehicle network. For example, each ECU may be connected to a communication line that supports communication protocols such as in-vehicle Ethernet, FlexRay®, MOST, and LIN. Furthermore, an in-vehicle network may be constructed by interconnecting multiple communication lines that support different communication protocols using a gateway or the like. In these embodiments as well, integrated power management of the entire power supply system can be realized by using communication frames.

[0260] Furthermore, the information stored in the communication frame is not limited to information indicating voltage settings such as the switch register 71 and the level register 72. For example, information indicating the vehicle status may be stored in the communication frame. Each zone ECU 1, 201, 301 and the upper-level ECU 6 refer to the signals contained in the communication frame received from the CAN bus 7 and grasp the information indicating the vehicle status. These ECUs then output instruction signals to the DC-DC converters 85, 86, load relay 89, and load 4 (load ECU 104), etc., so that they enter an operating state corresponding to the grasped vehicle status.

[0261] (Summary of the Third Embodiment) In the third embodiment described above, the output voltage of the primary DC-DC converter 85, etc., is set to match the operating state of the vehicle load. As a result, the same effects as in the first and second embodiments can be achieved, and the energy efficiency in the vehicle can be improved.

[0262] In addition, in the third embodiment, the communication unit 88 is configured to be able to send and receive a communication frame (CAN frame) containing a signal indicating a voltage setting according to the vehicle state with other in-vehicle devices. The control unit is configured to determine a target output voltage of the primary DCDC converter 85 or the like based on the signal included in the communication frame.

[0263] As described above, the first zone ECU 1 can instruct not only the load 4 within its own zone, but also the power manager 23, the higher-level ECU 6, other zone ECUs 201 and 301, and the load ECU 104, etc., to switch on and off and change voltage. In this way, information sharing using communication frames can enable coordinated power control across the entire vehicle's power supply system. As a result, it becomes possible to further improve the effect of reducing power consumption.

[0264] (Fourth Embodiment) In the circuit section of the zone ECU 1 according to the fourth embodiment of the present disclosure shown in Figure 28, a sub-input line 194 and a sub-branch line 196 are further formed as conductive wires. In addition, the zone ECU 1 is further provided with a first LDO (Low Dropout) 185, a first diode 185a, a second LDO 186, and a second diode 186a.

[0265] The sub-introduction line 194 branches off from the introduction line 94 (hereinafter referred to as the main introduction line 94). One end of the sub-introduction line 194 is connected to the main introduction line 94 on the upstream side (second switch 83 side) of the primary DC-DC converter 85. The other end of the sub-introduction line 194 is connected to the second voltage line 95 on the downstream side (load relay 89 side) of the primary DC-DC converter 85. The sub-introduction line 194 forms a current path that bypasses the primary DC-DC converter 85.

[0266] The sub-branch line 196 branches off from the branch line 96 (hereinafter referred to as the main branch line 96). One end of the sub-branch line 196 is connected to the main branch line 96 on the upstream side (second voltage line 95 side) of the secondary DC-DC converter 86. The other end of the sub-branch line 196 is connected to the third voltage line 97 on the downstream side (control unit 87 side) of the secondary DC-DC converter 86. The sub-branch line 196 forms a current path that bypasses the secondary DC-DC converter 86.

[0267] The first LDO 185 is a linear regulator that can operate even with a small input-output voltage difference. The first LDO 185 is connected in parallel to the primary DDC converter 85 by being installed on the path of the sub-input line 194. Similar to the primary DDC converter 85, the first LDO 185 steps down the input power supply voltage to generate a voltage for supplying power to the 12V load 4β, the secondary DDC converter 86, and the second LDO 186, etc.

[0268] The first LDO 185 outputs a 10V voltage in states 2, 3, and 5, as described above, and a 4.8V voltage in states 4, 6, and 7, as described above. Thus, the first LDO 185 is a low-load power supply unit that operates when the vehicle is in standby mode, etc. Therefore, the maximum output current of the first LDO 185 is smaller than the maximum output current of the primary DC-DC converter 85. The peak power output of the first LDO 185 is, for example, 2W or less. In low-load states where the power required is smaller than in normal states, the first LDO 185 supplies power to the 12V load 4β and the 5V power supply unit, etc., in place of the primary DC-DC converter 85. The power conversion efficiency of the first LDO 185 in low-load states is higher than the power conversion efficiency when using the primary DC-DC converter 85. Furthermore, the output voltage of the first LDO185 may be set to a voltage lower than the lower limit voltage at which the 12V load 4β can operate, or in other words, a voltage lower than the lower limit of the range in which the primary target voltage is changed.

[0269] The first diode 185a is provided downstream of the first LDO 185 (on the second voltage line 95 side) in the sub-introduction line 194. The first diode 185a allows forward current from the first LDO 185 to the second voltage line 95. On the other hand, the first diode 185a blocks reverse current from the second voltage line 95 to the first LDO 185.

[0270] The second LDO 186 is an LDO regulator with substantially the same configuration as the first LDO 185. The second LDO 186 is connected in parallel to the secondary DC-DC converter 86 by being provided on the path of the sub-branch line 196. Similar to the secondary DC-DC converter 86, the second LDO 186 steps down the input power supply voltage to generate a voltage for supplying power to the control unit 87 and the like.

[0271] The second LDO 186 is a low-load power supply unit that operates when the vehicle is in standby mode, and outputs a voltage of 4.8 to 5.0V in states 2 to 7, for example. Therefore, the maximum output current of the second LDO 186 is smaller than the maximum output current of the secondary DC-DC converter 86. The peak power output of the second LDO 186 is about the same as that of the first LDO 185 (for example, 2W or less). In low-load states where the required power is small, the second LDO 186 supplies power to a 5V load including the control unit 87, in place of the secondary DC-DC converter 86. The power conversion efficiency of the second LDO 186 in low-load states is higher than the power conversion efficiency when using only the second LDO 186. In addition, the output voltage of the second LDO 186 may be set to the lower limit voltage at which the control unit 87 can operate (for example, about 3.3V), in other words, a voltage lower than the lower limit of the range in which the secondary target voltage is changed.

[0272] The second diode 186a is provided downstream of the second LDO 186 (on the third voltage line 97 side) in the sub-branch line 196. The second diode 186a allows forward current from the second LDO 186 to the third voltage line 97. On the other hand, the second diode 186a blocks reverse current from the third voltage line 97 to the second LDO 186.

[0273] The control unit 87 is connected to the first LDO 185 and the second LDO 186 via signal lines. The control unit 87 can transmit instruction signals to the first LDO 185 and the second LDO 186. However, if the transmission of instruction signals from the control unit 87 to each DDC converter 85 and 86 enables switching from each DDC converter 85 and 86 to each LDO 185 and 186, then the transmission of instruction signals to each LDO 185 and 186 does not need to be performed.

[0274] Based on the signal received by the communication unit 88, the control unit 87 controls the power supply to the 12V load 4β and the control unit 87 from each LDO 185, 186 instead of each DDC converter 85, 86. More specifically, when the control unit 87 transitions to a low-load state based on sensor information or a state transition instruction signal, it first lowers the target output voltage of the primary DDC converter 85, similar to the first embodiment. When the power required from the load side decreases further in the low-load state, the control unit 87 stops the primary DDC converter 85. As a result, the power supply from the primary DDC converter 85 to the second voltage line 95 is stopped, and the main lead line 94 and the second voltage line 95 are electrically disconnected. Consequently, power supply to the second voltage line 95 by the first LDO 185 via the sub lead line 194 is started.

[0275] Similarly, the control unit 87, with respect to the secondary DC-DC converter 86, first changes the setting to lower the target output voltage (secondary target voltage) as the system transitions to a low-load state. When the power required from the 5V load (including the control unit 87) decreases further in the low-load state, the control unit 87 stops the secondary DC-DC converter 86. As a result, the power supply from the secondary DC-DC converter 86 to the third voltage line 97 is stopped, and the connection between the branch line 96 and the third voltage line 97 is electrically interrupted. Consequently, power supply to the third voltage line 97 by the second LDO 186 via the sub-branch line 196 begins.

[0276] (Summary of the Fourth Embodiment) In the fourth embodiment described above, the output voltage of the primary DC-DC converter 85, etc., is set to match the operating state of the vehicle load. As a result, the same effects as in the first to third embodiments can be achieved, and the energy efficiency of the vehicle can be increased.

[0277] In addition, in the fourth embodiment, a first LDO 185 is provided, which has a smaller maximum output current than the primary DDC converter 85. The first LDO 185 is connected in parallel with the primary DDC converter 85 and generates a voltage for stepping down the input voltage to supply power to the load. The control unit 87 is configured to supply power from the first LDO 185 instead of the primary DDC converter 85 based on the signal received by the communication unit 88. With this configuration, power supply with high efficiency and low dark current becomes possible under conditions where the output current is very small.

[0278] In the fourth embodiment, the first LDO 185 corresponds to the "low-load power supply unit." In this way, since an LDO regulator is used as the low-load power supply unit, it becomes possible to reduce the voltage difference between the input voltage from the isolated DC-DC converter 22 (e.g., 12V) and the output voltage (e.g., 10V). As a result, it is possible to achieve lower losses, lower noise, lower costs, and miniaturization of the low-load power supply unit.

[0279] <Supplementary Information on the Low-Load Power Supply Section> The low-load power supply section is configured to operate efficiently at milliampere-level output. Therefore, a configuration other than an LDO regulator may be used as the low-load power supply section. More specifically, the loss of the LDO regulator is the product of the voltage difference and the current. Therefore, if the current increases instantaneously or the voltage difference increases, the loss of the LDO regulator, and consequently the heat generated, will also increase. For this reason, a small, high-efficiency switching power supply (such as a DC-DC converter) is provided as the low-load power supply section in circuit sections where the current or voltage difference may increase. Switching power supplies include buck converters that use coils and switched capacitors that do not have coils. The control unit 87 controls the output voltage and supplied power of the switching power supply by providing instruction signals (such as PWM signals) to the switching power supply.

[0280] Furthermore, the low-load power supply unit may be configured in a combination of a step-down DC-DC converter (hereinafter referred to as a step-down DC-DC converter) and an LDO regulator. The step-down DC-DC converter is configured to step down the input voltage (e.g., 60V or 48V, etc.) to half or one-third of that value. The output voltage of the step-down DC-DC converter may fluctuate significantly. The LDO regulator is placed downstream of the step-down DC-DC converter. The LDO regulator stabilizes the output voltage of the step-down DC-DC converter, which has large fluctuations, and supplies it to the second voltage line 95 or the third voltage line 97.

[0281] (Fifth Embodiment) The fifth embodiment of the present disclosure is a modification of the fourth embodiment. In the fifth embodiment, the function of the control unit 87 that changes the target output voltage of the primary DC-DC converter 85 and the secondary DC-DC converter 86 is omitted. The control unit 87 selects whether to use the primary DC-DC converter 85 or the first LDO 185 to supply power to the second voltage line 95. Similarly, the control unit 87 selects whether to use the secondary DC-DC converter 86 or the second LDO 186 to supply power to the third voltage line 97.

[0282] More specifically, when the control unit 87 transitions to a low-load state based on sensor information or a state transition instruction signal, it stops the primary DC-DC converter 85 without changing the target output voltage of the primary DC-DC converter 85. As a result, the power supply from the primary DC-DC converter 85 to the second voltage line 95 is stopped, and power supply to the second voltage line 95 by the first LDO 185 via the sub-input line 194 is started.

[0283] Similarly, the control unit 87 also stops the secondary DC-DC converter 86 when transitioning to a low-load state, without changing the setting to lower the secondary target voltage. As a result, power supply from the secondary DC-DC converter 86 to the third voltage line 97 is stopped, and power supply to the third voltage line 97 is started by the second LDO 186 via the sub-branch line 196.

[0284] In the fifth embodiment described so far, the configuration that supplies power is selected from among the primary DC-DC converter 85 and the first LDO 185 depending on the vehicle state. Therefore, the configuration that is suitable for the vehicle state and, consequently, the operating state of the on-board load, will supply power. As a result, power loss or excessive power supply can be reduced, and thus, as in the first to fourth embodiments, power consumption in the vehicle can be reduced.

[0285] <Other Modifications> The above describes an embodiment in which the control unit 87 sets the output of the primary DC-DC converter 85 to 4.8V and sets the secondary DC-DC converter 86 to a continuous conduction state when only the 5V load of the control unit 87 is operating (hereinafter also referred to as the deep sleep state). The deep sleep state may be the sixth state or the seventh state.

[0286] However, the power saving method in deep sleep mode is not limited to this. The control unit 87 may intermittently drive the secondary DC-DC converter 86 during deep sleep mode. When the secondary DC-DC converter 86 is driven intermittently, the target output voltage (corresponding to a temporary voltage) of the primary DC-DC converter 85 located before it may be set to a predetermined value based on the maximum voltage of the control unit 87. The maximum voltage of the control unit 87 means the maximum value within the voltage range in which the control unit 87 can operate.

[0287] Intermittent driving of the secondary DC-DC converter 86 here may involve intermittently turning on the core switch (e.g., high-side switch) at intervals during which no coil current flows, as shown in Figure 29. The coil current here refers to the current flowing through the coil (in other words, inductor) provided at the output section of the secondary DC-DC converter 86. Intermittent driving corresponds to the discontinuous current mode (DCM) in a step-down DC-DC converter. The intermittent driving interval (Tid), which is the interval at which the core switch of the secondary DC-DC converter 86 is turned on, may be longer than the switching frequency in PWM control, for example, twice or more.

[0288] The intermittent drive interval (Tid) may not be a constant value but may be dynamically determined according to the power consumption of the load. The control unit 87 may be configured to turn on the core switch when the output voltage of the secondary DC-DC converter 86 drops to a predetermined drive threshold (Vc). The drive threshold may be set to the same value as the minimum voltage of the control unit 87 or to a predetermined amount higher. Such a setting can reduce the risk of the control unit 87 stopping or resetting.

[0289] Furthermore, the on-time (Ton), which is the length of time the core switch is turned on during intermittent drive, may be a constant value or may be adjusted according to the output voltage or load current. Even after the core switch is turned off, the output voltage continues to rise due to regeneration by low-side elements (e.g., low-side switches or diodes). The on-time (Ton) may be controlled so that the peak of the output voltage does not exceed the maximum voltage of the control unit 87. By introducing such intermittent drive control, power consumption in deep sleep mode can also be reduced. In Figure 29, "Va" represents the minimum voltage of the control unit 87, "Vb" represents the maximum voltage of the control unit 87, and "Vc" represents the drive threshold. The horizontal axis of the graph shown in Figure 29 represents time.

[0290] In addition, the control unit 87 may stop the isolated DC-DC converter 22 when it detects that the vehicle state has transitioned to a deep sleep state or a low load state. The zone ECU 1 may be configured to operate using the power of the sub-battery 3 when it detects that the vehicle state has transitioned to a deep sleep state or a low load state. In this case, the control unit 87 executes a process to stop receiving power from the isolated DC-DC converter 22 when it detects that the vehicle state has transitioned to a deep sleep state or a low load state. The process to stop receiving power from the isolated DC-DC converter 22 may be to send a stop request signal to the power manager 23 using the communication unit 88, or to turn off the main power switch 8A. Furthermore, the control unit 87 executes a process to start receiving power from the sub-battery 3 when it detects that the vehicle state has transitioned to a deep sleep state or a low load state. The process to start receiving power from the sub-battery 3 may be to set the sub-power switch 82 to ON.

[0291] <Design of Target Output Voltage> The primary target voltage (Vo1) in deep sleep mode is not limited to 4.8V. It may be set based on the lower limit of the voltage at which the control unit 87 can operate. The primary target voltage (Vo1) in deep sleep mode may also be 4.7V or 4.5V, etc.

[0292] In the case where a low-power 12V load is operating while a high-power 12V load is not operating (second, third, or fifth state), the primary target voltage (Vo1) is not limited to 10V, but may be 9V, 8.5V, etc. The primary target voltage in the case where a low-power 12V load is operating while a high-power 12V load is not operating may be any value within the voltage range in which the low-power 12V load can operate.

[0293] As described above, the primary and secondary target voltages for each vehicle state may be appropriately designed according to the combination of loads to be operated. The output voltage of the isolated DC-DC converter 22 according to the vehicle state may also be appropriately designed according to the combination of operating loads.

[0294] <Addendum (1)> This specification discloses several technical ideas and several combinations thereof, as listed below. Methods, programs, computers, and recording media on which programs are stored that correspond to the following technical ideas are also included in the scope of this disclosure.

[0295] [Technical Concept 1] A power distribution device mounted on a vehicle, comprising: a DC-DC converter (85) that steps down the power supply voltage input from a power supply system to generate a voltage for supplying power to a load; a control unit (87) that controls the output voltage of the DC-DC converter; and a communication unit (88) that receives a signal indicating the vehicle status or a signal indicating a voltage setting according to the vehicle status from another on-board device, wherein the control unit is configured to change the target output voltage of the DC-DC converter based on the signal received by the communication unit.

[0296] [Technical Concept 2] The power distribution device according to Technical Concept 1, comprising: a first converter which is a DC-DC converter for stepping down the power supply voltage; and a second converter (86) which is a DC-DC converter for further stepping down the output voltage of the first converter, wherein the control unit is configured to change the target output voltage of the first converter and the target output voltage of the second converter based on a signal received by the communication unit.

[0297] [Technical Concept 3] The power distribution device according to Technical Concept 2, wherein the vehicle state includes a normal state corresponding to the state in which the vehicle is running, and a low-load state in which less power is required compared to the normal state, and the control unit is configured to lower the target output voltage of the first converter when the vehicle state corresponds to the low-load state compared to when the vehicle state corresponds to the normal state.

[0298] [Technical Concept 4] A power distribution device according to any one of technical concepts 1 to 3, further comprising a low-load power supply unit (185) connected in parallel to the DC-DC converter, which steps down the input voltage to generate a voltage for supplying power to the load side, and which has a smaller maximum output current than the DC-DC converter, wherein the control unit is configured to supply power from the low-load power supply unit instead of the DC-DC converter based on a signal received by the communication unit.

[0299] [Technical Concept 5] A power distribution device according to technical concept 2 or 3 for supplying power to a plurality of loads with different operating voltages, wherein the plurality of loads include a first type load, a second type load operating at a lower voltage than the first type load, and a third type load operating at a lower voltage than the second type load, and the control unit is configured to set the target output voltage of the first converter to a voltage at which the third type load can operate, and to set the second converter to a continuous conduction state when the vehicle state is such that the first type load and the second type load are stopped.

[0300] [Technical Concept 6] A power distribution device according to any one of technical concepts 2, 3, and 5 for supplying power to a plurality of loads with different operating voltages, wherein the plurality of loads include a first type load, a second type load that operates at a lower voltage than the first type load, and a third type load that operates at a lower voltage than the second type load, and when the vehicle state is such that the first type load and the second type load are stopped, the control unit is configured to set the target output voltage of the first converter to a predetermined temporary voltage higher than the minimum voltage at which the third type load can operate, and to operate the second converter intermittently.

[0301] [Technical Concept 7] The power distribution device according to technical concept 6, further comprising: a first supply circuit for supplying the power supply voltage to the first type of load; a second supply circuit for supplying the output voltage of the first converter to the second type of load; and a third supply circuit for supplying the output voltage of the second converter to the third type of load.

[0302] [Technical Concept 8] The power distribution device according to Technical Concept 7, wherein the first supply circuit includes first load switches (89A, 89B) for switching the power supply state to the first type of load, the second supply circuit includes second load switches (89K, 89L) for switching the power supply state to the first type of load, and the control unit is configured to switch the open / closed state of the first load switch or the second load switch according to the vehicle state.

[0303] [Technical Concept 9] The power distribution device according to any one of Technical Concepts 1 to 8, wherein the control unit is configured to change the operating state of the load to a low power consumption state that consumes less power than before the target output voltage of the DC-DC converter is reduced in accordance with the vehicle state.

[0304] [Technical Concept 10] The power supply system includes a high-voltage battery with an output voltage of 200V or more, and an isolated DC-DC converter that reduces the output voltage of the high-voltage battery to 60V or less, the output voltage of the isolated DC-DC converter is input as the power supply voltage, and the power supply system is connected to the power supply system by one or more cables for use, the power distribution device according to any one of Technical Concepts 1 to 9.

[0305] [Technical Concept 11] The power distribution device according to technical concept 10, wherein the vehicle state includes a normal state corresponding to the state in which the vehicle is running and a low-load state in which less power is required compared to the normal state, and the control unit is configured to output a signal to the power supply system using the communication unit to request that the output voltage of the isolated DC-DC converter be reduced when the vehicle state is the low-load state.

[0306] [Technical Concept 12] The power distribution device according to technical concept 10 or 11, wherein the vehicle state includes a normal state corresponding to the state in which the vehicle is running and a low-load state in which the power required is less than that of the normal state, and comprises: a power input terminal into which the power supply voltage is input; a power supply voltage line which is a conductive wire connecting the power supply input terminal and the DC-DC converter; a power storage unit (90) connected to the power supply voltage line and configured to supply power to the DC-DC converter; and a charge state monitoring unit (F2) which monitors the remaining power of the power storage unit, and the control unit is configured to perform a process to stop receiving power from the isolated DC-DC converter when the vehicle state is the low-load state and the remaining power of the power storage unit detected by the charge state monitoring unit is sufficient, and to perform a process to resume receiving power from the isolated DC-DC converter when the remaining power of the power storage unit has fallen to a predetermined level while receiving power from the isolated DC-DC converter has been stopped.

[0307] [Technical Concept 13] A power distribution device according to any one of technical concepts 10 to 12, which is used in conjunction with a sub-battery capable of outputting the power supply voltage, wherein the vehicle state includes a normal state corresponding to the state in which the vehicle is running and a low-load state in which the power required is less than that of the normal state, and the control unit is configured to perform a process to stop receiving power from the isolated DC-DC converter and start receiving power from the sub-battery when the vehicle state transitions to the low-load state.

[0308] [Technical Concept 14] A power distribution device according to any one of technical concepts 1 to 13, further comprising a memory (872) storing setting data for the target output voltage according to the operating state of the vehicle, wherein the communication unit is configured to receive a signal indicating the vehicle state from a vehicle state sensor which is another in-vehicle device, and the control unit is configured to identify the operating state of the vehicle based on the signal received by the communication unit, and to determine the target output voltage of the DC-DC converter based on the identified operating state of the vehicle and the setting data stored in the memory.

[0309] [Technical Concept 15] The power distribution device according to any one of Technical Concepts 1 to 13, wherein the communication unit is configured to transmit and receive a communication frame including a signal indicating the vehicle status or a signal indicating the voltage setting according to the vehicle status to the other in-vehicle device, and the control unit is configured to determine the target output voltage of the DC-DC converter based on the signal included in the communication frame.

[0310] [Technical Concept 16] The power distribution device according to any one of technical concepts 1 to 15, wherein the communication unit is configured to receive an instruction signal regarding the target output voltage from a power management device (6) that performs power management according to the vehicle state, and the control unit is configured to adjust the target output voltage based on the instruction signal received by the communication unit.

[0311] [Technical Concept 17] The power distribution device according to technical concept 16, wherein the control unit is configured to report to the power management device, using the communication unit, data relating to the power received from the power supply system and the power output to the load.

[0312] [Technical Concept 18] A power supply system comprising a power supply system and a power distribution device mounted on a vehicle, wherein the power supply system comprises a high-voltage battery (21) with an output voltage of 200V or more, and an isolated DC-DC converter (22) that reduces the output voltage of the high-voltage battery to 60V or less, and the power distribution device comprises a power input terminal (11) that receives the output voltage of the isolated DC-DC converter as a power supply voltage, a DC-DC converter (85) that steps down the power supply voltage to generate a voltage for supply to a load, a low-load power supply unit (185) connected in parallel to the DC-DC converter, which steps down the power supply voltage to generate a voltage for supply to the load and has a smaller maximum output current than the DC-DC converter, a communication unit (88) that receives a signal indicating the vehicle status or a signal indicating a voltage setting according to the vehicle status from another on-board device, and a control unit (87) that selects whether to use the DC-DC converter or the low-load power supply unit for supplying power to the load based on the signal received by the communication unit.

[0313] [Technical Concept 19] A power distribution device comprising: a DC-DC converter (85) that steps down the power supply voltage input from a power supply system to generate a voltage for supply to a load; a low-load power supply unit (185) connected in parallel to the DC-DC converter, which steps down the power supply voltage to generate a voltage for supply to the load and has a smaller maximum output current than the DC-DC converter; and a communication unit (88) configured to communicate with other in-vehicle devices, wherein a power supply control program is executed by a computer connected to at least the DC-DC converter and the communication unit, and includes instructions to cause the computer to: obtain information indicating the vehicle status or information on voltage settings corresponding to the vehicle status from the other in-vehicle devices using the communication unit; and select whether to use the DC-DC converter or the low-load power supply unit for supplying power to the load based on the information indicating the vehicle status or the information on voltage settings obtained using the communication unit.

[0314] <Addendum (2)> The various flowcharts shown in this disclosure are all examples, and the number of steps constituting the flowchart and the order of execution of processes can be changed as appropriate. The controls shown in each flowchart may be combined and executed in parallel to the extent that they do not contradict each other. Expressions such as acquisition, determination, detection, generation, and calculation may be used interchangeably. When a device acquires certain data, it also includes when the device generates such data based on signals input from other devices / sensors.

[0315] The devices, systems, and methods described in this disclosure may be implemented by a dedicated computer comprising a processor programmed to perform one or more functions embodied by a computer program. The devices and methods described in this disclosure may be implemented using dedicated hardware logic circuits. The devices and methods described in this disclosure may be implemented by one or more dedicated computers comprising a combination of a processor that executes a computer program and one or more hardware logic circuits. The processor may be any arithmetic core, such as a CPU, MPU, GPU, or DFP (Data Flow Processor). Some or all of the functions of the control unit may be implemented as hardware. Some or all of the functions of the control unit may be implemented using a system-on-a-chip (SoC), integrated circuit (IC), or field-programmable gate array (FPGA).

[0316] A computer program includes instructions that are executed by a computer. A computer program may be stored on a computer-readable, non-transitory tangible storage medium. The storage medium for a computer program may be a variety of media, such as an HDD (Hard-disk drive), an SSD (Solid State Drive), or flash memory.

Claims

1. A power distribution device mounted on a vehicle, comprising: a DC-DC converter (85) that steps down a power supply voltage input from a power supply system to generate a voltage for supplying power to a load; a control unit (87) that controls the output voltage of the DC-DC converter; and a communication unit (88) that receives a signal indicating the vehicle status or a signal indicating a voltage setting according to the vehicle status from another on-board device, wherein the control unit is configured to change the target output voltage of the DC-DC converter based on the signal received by the communication unit.

2. The power distribution device according to claim 1, comprising: a first converter which is a DC-DC converter for stepping down the power supply voltage; and a second converter (86) which is a DC-DC converter for further stepping down the output voltage of the first converter, wherein the control unit is configured to change the target output voltage of the first converter and the target output voltage of the second converter based on a signal received by the communication unit.

3. The power distribution device according to claim 2, wherein the vehicle state includes a normal state corresponding to the state in which the vehicle is running, and a low-load state in which the power required is less than that of the normal state, and the control unit is configured to lower the target output voltage of the first converter when the vehicle state corresponds to the low-load state compared to when the vehicle state corresponds to the normal state.

4. The power distribution device according to claim 1, further comprising a low-load power supply unit (185) connected in parallel to the DC-DC converter, which steps down the input voltage to generate a voltage for supplying power to the load side, and which has a smaller maximum output current than the DC-DC converter, wherein the control unit is configured to supply power from the low-load power supply unit instead of the DC-DC converter based on a signal received by the communication unit.

5. A power distribution device according to claim 2 for supplying power to a plurality of loads with different operating voltages, wherein the plurality of loads include a first type load, a second type load operating at a lower voltage than the first type load, and a third type load operating at a lower voltage than the second type load, and the control unit is configured to set the target output voltage of the first converter to a voltage at which the third type load can operate, and to set the second converter to a continuous conduction state when the vehicle state is such that the first type load and the second type load are stopped.

6. A power distribution device according to claim 2 for supplying power to a plurality of loads with different operating voltages, wherein the plurality of loads include a first type load, a second type load operating at a lower voltage than the first type load, and a third type load operating at a lower voltage than the second type load, and when the vehicle state is such that the first type load and the second type load are stopped, the control unit is configured to set the target output voltage of the first converter to a predetermined temporary voltage higher than the minimum voltage at which the third type load can operate, and to operate the second converter intermittently.

7. The power distribution device according to claim 6, further comprising: a first supply circuit for supplying the power supply voltage to the first type of load; a second supply circuit for supplying the output voltage of the first converter to the second type of load; and a third supply circuit for supplying the output voltage of the second converter to the third type of load.

8. The power distribution device according to claim 7, wherein the first supply circuit includes first load switches (89A, 89B) for switching the power supply state to the first type of load, the second supply circuit includes second load switches (89K, 89L) for switching the power supply state to the first type of load, and the control unit is configured to switch the open / closed state of the first load switch or the second load switch according to the vehicle state.

9. The power distribution device according to claim 1, wherein the control unit is configured to change the operating state of the load to a low power consumption state, which consumes less power than before the target output voltage of the DC-DC converter was reduced in accordance with the vehicle state.

10. The power distribution device according to claim 1, wherein the power supply system includes a high-voltage battery with an output voltage of 200V or more and an isolated DC-DC converter that reduces the output voltage of the high-voltage battery to 60V or less, the output voltage of the isolated DC-DC converter is input as the power supply voltage, and the device is used by being connected to the power supply system by one or more cables.

11. The power distribution device according to claim 10, wherein the vehicle state includes a normal state corresponding to the state in which the vehicle is running and a low-load state in which less power is required compared to the normal state, and the control unit is configured to output a signal to the power supply system using the communication unit requesting that the output voltage of the isolated DC-DC converter be reduced when the vehicle state is the low-load state.

12. The power distribution device according to claim 10, wherein the vehicle state includes a normal state corresponding to the state in which the vehicle is running and a low-load state in which the power required is less than that of the normal state, and comprises: a power input terminal into which the power supply voltage is input; a power supply voltage line which is a conductive wire connecting the power supply input terminal and the DC-DC converter; a power storage unit (90) connected to the power supply voltage line and configured to supply power to the DC-DC converter; and a charge state monitoring unit (F2) which monitors the remaining power of the power storage unit, and the control unit is configured to perform a process to stop receiving power from the isolated DC-DC converter when the vehicle state is the low-load state and the remaining power of the power storage unit detected by the charge state monitoring unit is sufficient, and to perform a process to resume receiving power from the isolated DC-DC converter when the remaining power of the power storage unit has fallen to a predetermined level while receiving power from the isolated DC-DC converter has been stopped.

13. A power distribution device according to claim 12, which is used in conjunction with a sub-battery capable of outputting the power supply voltage, wherein the control unit is configured to perform a process to stop receiving power from the isolated DC-DC converter and start receiving power from the sub-battery when the vehicle state transitions to the low-load state.

14. The power distribution device according to any one of claims 1 to 13, further comprising a memory (872) storing setting data for the target output voltage corresponding to the operating state of the vehicle, wherein the communication unit is configured to receive a signal indicating the vehicle state from another in-vehicle device, which is a vehicle state sensor, and the control unit is configured to identify the operating state of the vehicle based on the signal received by the communication unit, and to determine the target output voltage of the DC-DC converter based on the identified operating state of the vehicle and the setting data stored in the memory.

15. The power distribution device according to any one of claims 1 to 13, wherein the communication unit is configured to transmit and receive a communication frame including a signal indicating the vehicle status or a signal indicating the voltage setting according to the vehicle status to the other in-vehicle device, and the control unit is configured to determine the target output voltage of the DC-DC converter based on the signal included in the communication frame.

16. The power distribution device according to any one of claims 1 to 13, wherein the communication unit is configured to receive an instruction signal regarding the target output voltage from a power management device (6) that performs power management according to the vehicle state, and the control unit is configured to adjust the target output voltage based on the instruction signal received by the communication unit.

17. The power distribution device according to claim 16, wherein the control unit is configured to report to the power management device, using the communication unit, data relating to the power received from the power supply system and the power output to the load.

18. A power supply system including a power supply system and a power distribution device mounted on a vehicle, wherein the power supply system includes a high-voltage battery (21) with an output voltage of 200V or more, and an isolated DC-DC converter (22) that reduces the output voltage of the high-voltage battery to 60V or less, and the power distribution device includes a power input terminal (11) that receives the output voltage of the isolated DC-DC converter as a power supply voltage, a DC-DC converter (85) that steps down the power supply voltage to generate a voltage for supply to a load, a control unit (87) that controls the output voltage of the DC-DC converter, and a communication unit (88) that receives a signal indicating the vehicle status or a signal indicating a voltage setting according to the vehicle status from another on-board device, wherein the control unit is configured to change the target output voltage of the DC-DC converter based on the signal received by the communication unit.

19. A supply control program executed by a computer connected to a DC-DC converter (85) that steps down the power supply voltage input from a power supply system to generate a voltage for supply to a load, and a communication unit (88) configured to communicate with other in-vehicle devices, the supply control program including an instruction to cause the computer to: obtain information indicating the vehicle status or information on voltage settings corresponding to the vehicle status from the other in-vehicle devices using the communication unit; and adjust the output voltage of the DC-DC converter based on the information indicating the vehicle status or the information on voltage settings obtained using the communication unit.

20. A power distribution device mounted on a vehicle, comprising: a DC-DC converter (85) that steps down the power supply voltage input from a power supply system to generate a voltage for supplying power to a load; a low-load power supply unit (185) connected in parallel to the DC-DC converter, which steps down the power supply voltage to generate a voltage for supplying power to the load and has a smaller maximum output current than the DC-DC converter; a communication unit (88) that receives signals indicating the vehicle status or signals indicating voltage settings according to the vehicle status from other on-board devices; and a control unit (87) that selects whether to use the DC-DC converter or the low-load power supply unit for supplying power to the load based on the signals received by the communication unit.

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