Power supply device and power supply method

Abstract

The present invention comprises: a DC-DC conversion unit (101); a first FET (11) disposed upstream of the DC-DC conversion unit; and an OVP control unit (23) that controls the ON / OFF of the first FET. The DC-DC conversion unit includes a second FET (12) as a high-side switch, a third FET (13) as a low-side switch, an inductor (14), and a DC-DC control unit (19). The OVP control unit, after setting the first FET to ON so that a current flows through the high-side switch, monitors an output voltage of the DC-DC conversion unit. The OVP control unit, in response to the output voltage of the DC-DC conversion unit exceeding a protection threshold, starts temporary control including switching of the first FET.

Description

Power supply device, power supply method CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on Patent Application No. 2024-152493 filed in Japan on September 4, 2024, and the contents of the original application are incorporated by reference in their entirety.

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

[0003] A circuit that converts a first voltage, which is a direct current voltage input from a power source, into a second voltage suitable for the operation of a load and outputs the converted second voltage is known as a DC-DC converter. Patent Document 1 discloses a switching regulator configuration in which a switching element (hereinafter, referred to as a cutoff switch) is introduced as a circuit breaker between a voltage adjustment switching element and a diode. In the configuration disclosed in Patent Document 1, a control unit monitors the output voltage and turns off the cutoff switch when the output voltage exceeds a predetermined value. This prevents an overvoltage (e.g., the first voltage) from being continuously applied to the load even if the voltage adjustment switching element experiences a short-circuit failure.

[0004] Japanese Patent Application Laid-Open No. 2006-33943

[0005] In the configuration disclosed in Patent Document 1, if an abnormality occurs in the DCDC conversion circuit and the output voltage becomes an overvoltage state, the power supply to the load is cut off. In the configuration disclosed in Patent Document 1, if an abnormality that causes an overvoltage occurs in the DCDC conversion circuit, the load cannot continue to operate.

[0006] One object of the present disclosure is to provide a technology that can continue to supply power to a load even when an abnormality occurs in a DCDC conversion circuit.

[0007] One of the power supply devices disclosed herein is a power supply device for stepping down a first voltage corresponding to the voltage of a power supply of a vehicle and supplying the stepped down first voltage to at least one load device, and includes a load connection terminal which is a terminal electrically connected to at least one load device, a DCDC conversion unit which is a circuit for generating a second voltage lower than the first voltage based on the first voltage, an auxiliary switch which is a switching element attached to the DCDC conversion unit, and an auxiliary switch control unit which controls the on / off of the auxiliary switch, and the DCDC conversion unit is a switching element which is on / off controlled so that the output voltage becomes the second voltage, and includes a high-side switch connected to a power supply line to which the first voltage is applied, and an auxiliary switch control unit downstream of the high-side switch The power supply comprises a low-side element which is a switching element or diode connected in series with the high-side switch, and a DCDC control unit which controls the on / off of the high-side switch so that the voltage applied to the load connection terminal becomes a second voltage, the auxiliary switch is arranged between the low-side element and the power supply, and the auxiliary switch control unit monitors the output voltage of the DCDC conversion unit when the auxiliary switch is set to either on or off so that current flows through the high-side switch, and is configured to initiate temporary control which dynamically switches the auxiliary switch on and off so that the voltage applied to the load connection terminal becomes a predetermined temporary target voltage when the output voltage of the DCDC conversion unit exceeds a predetermined threshold.

[0008] The present disclosure also provides a power supply method implemented by at least one controller provided in a power supply circuit including: a load connection terminal that is a terminal electrically connected to at least one load device; a high-side switch to which a first voltage corresponding to the voltage of a vehicle power supply is input; a low-side element that is a switching element or a diode connected in series with the high-side switch downstream of the high-side switch; and an auxiliary switch that is a switching element different from the high-side switch and is arranged between the low-side element and the power supply, the power supply method including the steps of: setting the auxiliary switch to either on or off so that a current flows through the high-side switch; generating a second voltage lower than the first voltage by switching the high-side switch while the auxiliary switch is set to a state in which a current flows through the high-side switch; monitoring whether the voltage generated by switching the high-side switch exceeds a predetermined threshold; and, when the voltage generated by switching the high-side switch exceeds the threshold, starting temporary control of dynamically switching the auxiliary switch on and off so that the voltage applied to the load connection terminal becomes a predetermined temporary target voltage.

[0009] According to the above technology, when an abnormality occurs in the DCDC converter, causing an overvoltage to be output, temporary voltage reduction control is performed using the auxiliary switch as an alternative, thereby enabling continuous power supply to the load device.

[0010] Note that the symbols in parentheses in the claims indicate a correspondence with the specific means described in the embodiments described below as one aspect, and do not limit the technical scope of the present disclosure.

[0011] 9 is a diagram for explaining the configuration of a zone ECU; FIG. 10 is a diagram for explaining an example of a power supply circuit; FIG. 11 is a diagram for explaining an example of switch operation in a basic mode; FIG. 12 is a diagram for explaining an example of an abnormality related to overvoltage; FIG. 13 is a diagram for explaining an example of switch operation in a temporary mode; FIG. 14 is a flowchart for explaining an example of an operation of a zone ECU; FIG. 15 is a flowchart for explaining an example of overvoltage response processing; FIG. 16 is a diagram for explaining a basic mode in the circuit configuration shown in FIG. 15; FIG. 17 is a diagram for explaining a temporary mode in the circuit configuration shown in FIG. 16; FIG. 18 is a flowchart for explaining another example of operation of a zone ECU; FIG. 19 is a flowchart for explaining another example of overvoltage response processing.

[0012] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The present disclosure is not limited to the following embodiments. The configurations disclosed below may be modified in various ways without departing from the spirit of the present disclosure. Various modified examples may be appropriately combined as long as no technical contradictions arise. The present disclosure also includes configurations that are not explicitly stated and are formed by combining multiple modified examples. In the following description, components having the same function may be given the same reference numerals, and specific descriptions thereof may be omitted. Furthermore, components having the same function may be given the same or similar names, and specific descriptions thereof may be omitted. When only a portion of a configuration is mentioned, descriptions given elsewhere may apply to other parts.

[0013] 1 is a diagram illustrating a schematic configuration of a zone ECU (Electronic Control Unit) 1, which is one embodiment of a power supply control device according to the present disclosure. The zone ECU 1 of this embodiment is mounted on a vehicle and is connected to a central ECU 7, a power source 8, and a load device 9. The zone ECU 1 corresponds to a power supply device.

[0014] The central ECU 7 is a higher-level ECU than the zone ECUs 1. The central ECU 7 comprehensively controls the multiple zone ECUs 1 installed in the vehicle. The central ECU 7 generates commands (control signals) for controlling the on-board devices and transmits them to the corresponding zone ECUs 1. The central ECU 7 may be understood as an ECU that controls the on-board devices via the zone ECUs 1.

[0015] The power supply 8 may be a DC power supply mounted on the vehicle. The power supply 8 may be an on-board battery, etc. The power supply 8 is capable of supplying power to the zone ECU 1. The power supply 8 inputs, for example, a DC voltage of 48 V to the zone ECU 1. The load device 9 may be another ECU, an actuator, a sensor, etc. The load device 9 includes the above-mentioned on-board devices.

[0016] The zone ECUs 1, together with the central ECU 7, load devices 9, and communication lines, constitute an in-vehicle network system. The zone ECUs 1 are arranged in each of a plurality of pre-defined zones in the vehicle. At least one of the plurality of zone ECUs 1 includes a power supply circuit 100.

[0017] The power supply circuit 100 converts the voltage input from the power source 8 (hereinafter also referred to as the first voltage) into a predetermined second voltage suitable for the operation of the load device 9 and supplies it to the load device 9. The second voltage is a voltage lower than the first voltage, such as 12 V. The second voltage may also be 8 V or 10 V. The second voltage may be set to a value according to the specifications of the load device 9. The second voltage corresponds to a target voltage value. In the following, the second voltage may be referred to as a basic target voltage to distinguish it from a temporary target voltage described later. The zone ECU 1 is configured to operate according to a power supply method.

[0018] The zone ECU 1 is connected to a plurality of load devices 9. The zone ECU 1 distributes power to each of the plurality of load devices 9. A switch 201 may be provided between the load devices 9 and an output line 34 (described later). The zone ECU 1 may be configured to change the combination of the load devices 9 to which power is supplied by turning the switch 201 on and off.

[0019] In one embodiment, the zone ECU 1 may include a load control unit 200 that manages a plurality of load devices 9 connected to the zone ECU 1. The load control unit 200 is configured to select (dynamically change) the destination of power supply using a switch 201. The load control unit 200 may be realized using a computer including a processor and a memory, an IC, or an FPGA.

[0020] The load control unit 200 can control the distribution of power to other ECUs, actuators, sensors, etc. For example, when an abnormality occurs in the power supply circuit 100, the load control unit 200 may be configured to stop the power supply to some of the load devices 9 and supply power only to specific load devices 9.

[0021] The multiple load devices 9 may include priority loads 9a and normal loads 9b. The priority loads 9a are load devices 9 that maintain power supply even when an abnormality occurs, in other words, load devices 9 with high priority. The priority loads 9a may also be referred to as important loads. On the other hand, the normal loads 9b are load devices 9 that cut off power supply when an abnormality occurs, in other words, load devices 9 with low priority. The priority loads 9a may be safety-related in-vehicle equipment such as an electric power steering or a brake system. The priority loads 9a may also be other zone ECUs, forward monitoring sensors, etc. Load devices 9 other than the priority loads 9a are normal loads 9b. For example, an air conditioning system or an audio system could be the normal loads 9b.

[0022] The load control unit 200 may register load setting data, which is data indicating the load type of each load device 9, such as whether it is a priority load 9a or a normal load 9b. The load setting data may be stored in a non-volatile storage medium (not shown). When an abnormality is detected in the power supply circuit 100, the load control unit 200 may determine whether to continue or cut off the power supply to each load device 9 in accordance with the load setting data. The load control unit 200 may also be referred to as a load management unit.

[0023] In other embodiments, the zone ECU 1 may be configured to supply power to one load device 9. Furthermore, multiple load devices 9 having different rated voltages (or operating voltages) may be connected to the zone ECU 1. The zone ECU 1 may be configured to generate and output multiple voltages having different voltage values. Multiple target voltages may be set for the power supply circuit 100 to generate.

[0024] The zone ECU 1 may be equipped with functions other than the power supply function. For example, the zone ECU 1 may have a gateway function to convert and relay data between networks with different communication methods, enabling mutual communication. The zone ECU 1 may also have a function to control the load device 9 based on commands from the central ECU 7.

[0025] <Power Supply Circuit> Next, the configuration of the power supply circuit 100 will be described. The power supply circuit 100 includes a power supply connection terminal 10, a first FET 11, a second FET 12, a third FET 13, an inductor 14, a capacitor 15, a fourth FET 16, a first resistor 17, a second resistor 18, a DCDC control unit 19, and a load connection terminal 20. The power supply circuit 100 also includes a third resistor 21, a fourth resistor 22, and an OVP control unit 23 in addition to the above components. FET stands for Field Effect Transistor. The first FET 11, the second FET 12, the third FET 13, and the fourth FET 16 each include three terminals: a source, a drain, and a gate. OVP stands for Over Voltage Protection and means overvoltage protection. The power supply circuit 100 is mounted on a printed wiring board. For simplicity of illustration, only one load device 9 is shown below. Moreover, the switch 201 attached to the output line 34 is not shown.

[0026] Additionally, the power supply circuit 100 includes a plurality of conductive lines as wiring for connecting components that make up the circuit. The conductive lines may be copper conductive films provided on a printed wiring board. That is, the conductive lines may be patterned on the surface or an internal layer of the printed wiring board. In one aspect, the conductive lines may be microstrips or striplines. The conductive lines may include jumper wires or vias. The term "conductive lines" may be replaced with "signal lines" or "conductive paths," etc.

[0027] As will be described below, a circuit including the second FET 12, the third FET 13, the inductor 14, the capacitor 15, and the DCDC control unit 19 is configured to function as a DCDC converter, particularly as a synchronous rectification switching regulator. In this disclosure, a circuit module including the second FET 12, the third FET 13, the inductor 14, the capacitor 15, and the DCDC control unit 19 is referred to as a DCDC conversion unit 101. Note that the DCDC conversion unit 101 may also include a first resistor 17, a second resistor 18, a first feedback line 35, and the like. The inductor 14 or the capacitor 15 may be omitted.

[0028] The power supply connection terminal 10 is electrically connected to the power supply 8. The power supply connection terminal 10 may be integrally formed with a connector exposed outside the housing of the zone ECU 1. Power from the power supply 8 is supplied to the power supply connection terminal 10 through a wire harness or the like connected to the connector. A first voltage, which is the output voltage of the power supply 8, is input to the power supply connection terminal 10. Note that the term "first voltage" may be replaced with expressions such as power supply voltage or input voltage. A power supply line 30, which is a conductive wire to which the first voltage is applied, is connected to the power supply connection terminal 10. "Vin" in the figure indicates the first voltage.

[0029] The first FET 11 is an N-channel MOS (Metal-Oxide-Semiconductor) FET. The drain of the first FET 11 is connected to the power supply line 30. That is, the drain of the first FET 11 is connected to the power supply 8 via the power supply line 30 and the power supply connection terminal 10. The source of the first FET 11 is connected to the drain of the second FET 12 via a conductive line. Hereinafter, the conductive line connecting the source of the first FET 11 and the drain of the second FET 12 will be referred to as a first relay line 31.

[0030] The first FET 11 functions as a switch for switching the connection state (connection / disconnection) between the power supply line 30 and the first relay line 31. In other words, the first FET 11 corresponds to a relay for the DCDC conversion unit 101. The gate of the first FET 11 is connected to the output terminal of the OVP control unit 23. The on / off of the first FET 11 is controlled by the OVP control unit 23. The first FET 11 corresponds to an auxiliary switch, particularly a first auxiliary switch.

[0031] The first FET 11 is always set to on in a basic mode, which will be described later. On the other hand, the first FET 11 is on / off controlled as a high-side switch in place of the second FET 12 in a temporary mode, which will be described later. Therefore, the first FET 11 may be referred to as an alternative switch or an alternative FET. The first FET 11 includes a body diode. The anode of the body diode is connected to the first relay line 31, and the cathode is connected to the power supply line 30.

[0032] The second FET 12 and the third FET 13 are also N-channel MOSFETs. The drain of the second FET 12 is connected to the first relay line 31. The source of the second FET 12 is connected to the drain of the third FET 13 via a conductive line. In other words, the second FET 12 and the third FET 13 are connected in series. Hereinafter, the conductive line connecting the source of the second FET 12 and the drain of the third FET 13 will be referred to as the second relay line 32.

[0033] The gate of the second FET 12 is connected to the DCDC control unit 19. Therefore, the on / off of the second FET 12 is controlled by the DCDC control unit 19. The second FET 12 includes a body diode. The anode of the body diode in the second FET 12 is connected to the second relay line 32, and the cathode is connected to the first relay line 31. The second FET 12 is a switching element that serves as a high-side switch in the DCDC converter. Therefore, the second FET 12 may be referred to as a high-side switch or a high-side FET.

[0034] The drain of the third FET 13 is connected to the source of the second FET 12 via the second relay line 32. The source of the third FET 13 is connected to the circuit ground. The gate of the third FET 13 is connected to the DCDC control unit 19. Therefore, the on / off of the third FET 13 is controlled by the DCDC control unit 19. The third FET 13 includes a body diode. The anode of the body diode in the third FET 13 is connected to the ground, and the cathode is connected to the second relay line 32. The third FET 13 is a switching element that serves as a low-side switch in the DCDC converter. Therefore, the third FET 13 may be referred to as a low-side switch or a low-side FET. The third FET 13 corresponds to a low-side element.

[0035] A third relay line 33, which is a conductive line connected to one end of the inductor 14, is connected to the middle of the second relay line 32. One end of the inductor 14 is connected to the source of the second FET 12 and the drain of the third FET 13 via the third relay line 33. The other end of the inductor 14 is connected to the load connection terminal 20 via an output line 34.

[0036] The output line 34 is a conductive line connected to the load connection terminal 20. One end of the output line 34 is connected to the downstream terminal of the inductor 14, and the other end is connected to the load connection terminal 20. The inductor 14 smoothes the current input from the second FET 12 and stores power. The output line 34 may be connected to the ground line via a power Zener diode. The power Zener diode protects the load device 9 from abnormal voltage (overvoltage).

[0037] Furthermore, the output line 34 is connected to the ground line via a capacitor 15. One end of the capacitor 15 is connected to the output line 34, and the other end is connected to ground. The capacitor 15 stabilizes the output voltage in cooperation with the inductor 14. The voltage applied to the output line 34 is the output voltage of the power supply circuit 100. The output voltage of the power supply circuit 100, in other words, the voltage applied to the load connection terminal 20, may also be referred to as the circuit output voltage. Basically, the output voltage below may be interpreted as the circuit output voltage. "Vout" in the diagram represents the circuit output voltage. In the basic mode, the output voltage of the DCDC conversion unit 40 corresponds to the circuit output voltage.

[0038] The fourth FET 16 is a switching element connected in parallel to the second FET 12 as a high-side switch. The fourth FET 16 may be an N-channel MOSFET. The drain of the fourth FET 16 is connected to the first relay line 31. In other words, the drain of the fourth FET 16 is electrically connected to the source of the first FET 11 and the drain of the second FET 12. The source of the fourth FET 16 is connected to the third relay line 33. Note that the second relay line 32 and the third relay line 33 are electrically connected, so the source of the fourth FET 16 may be the second relay line 32. It is sufficient that the source of the fourth FET 16 is electrically connected to the source of the second FET 12 and the drain of the third FET 13.

[0039] The gate of the fourth FET 16 is connected to the OVP control unit 23. Therefore, the on / off of the fourth FET 16 is controlled by the OVP control unit 23. The fourth FET 16 includes a body diode. The anode of the body diode in the fourth FET 16 is connected to the second relay line 32 or the third relay line 33, and the cathode is connected to the first relay line 31.

[0040] The fourth FET 16 is set to off in the basic mode. Therefore, in the basic mode, the current path through the fourth FET 16 is disabled, and the current from the first FET 11 flows toward the first FET 11. On the other hand, the fourth FET 16 is set to on in the temporary mode. This disables the current path through the second FET 12, and the current from the first FET 11 flows into the third relay line 33 through the fourth FET 16. In this way, the fourth FET 16 is a switching element for forming a current path (a detour) that does not pass through the second FET 12 in the temporary mode. The fourth FET 16 may be referred to as a detour switch, a detour FET, or the like.

[0041] The first resistor 17 and the second resistor 18 form a voltage divider circuit for inputting a voltage corresponding to the output voltage to the DCDC control unit 19. The first resistor 17 and the second resistor 18 are connected in series between the output line 34 and ground. The upstream terminal of the first resistor 17 is connected to the output line 34, and the downstream terminal of the first resistor 17 is connected to one end of the second resistor 18. The upstream terminal of the second resistor 18 is connected to the downstream terminal of the first resistor 17, and the downstream terminal of the second resistor 18 is connected to ground. The total resistance value of the first resistor 17 and the second resistor 18 may be set to a sufficiently large value (e.g., 6 MΩ or more) so that the current flowing through the voltage divider circuit is as small as possible. Furthermore, when the resistance value of the first resistor 17 is R1 and the resistance value of the second resistor 18 is R2, R1 may be set to a value sufficiently larger than R2 (e.g., 8 to 10 times).

[0042] The conductive line connecting the first resistor 17 and the second resistor 18 is connected to the DCDC control unit 19 via a first feedback line 35. The first feedback line 35 is one of the conductive lines. One end of the first feedback line 35 is electrically connected to the downstream terminal of the first resistor 17, and the other end is connected to the DCDC control unit 19. For convenience, the voltage of the first feedback line 35 is also referred to as a first feedback voltage Va.

[0043] The DCDC control unit 19 is configured to adjust the circuit output voltage to the second voltage by PWM control using the second FET 12 and the third FET 13. That is, the DCDC control unit 19 controls the on / off of the second FET 12 and the third FET 13 so that the output voltage becomes the second voltage. Such a DCDC control unit 19 may be realized using a general-purpose IC, an ASIC, an FPGA, or the like. The DCDC control unit 19 may also be called a DCDC driver, etc.

[0044] The DCDC control unit 19 is connected to the gates of the second FET 12 and the third FET 13. That is, the DCDC control unit 19 includes a high-side output terminal P1 which is an output terminal electrically connected to the gate of the second FET 12, and a low-side output terminal P2 which is an output terminal electrically connected to the gate of the third FET 13. The DCDC control unit 19 is configured to be able to apply a predetermined positive voltage (hereinafter, gate voltage) to each of the gates of the second FET 12 and the third FET 13 using the high-side output terminal P1 and the low-side output terminal P2.

[0045] When the DCDC control unit 19 applies a gate voltage to the gate of the second FET 12, the drain and source of the second FET 12 are conductive (ON state). When no gate voltage is applied to the gate of the second FET 12, the drain and source of the second FET 12 are non-conductive (OFF state). The state in which a gate voltage is applied to the gate of the second FET 12 corresponds to the state in which a high-level signal corresponding to the gate voltage is output from the high-side output terminal P1. The state in which no gate voltage is applied to the gate of the second FET 12 corresponds to the state in which the output of the high-side output terminal P1 is set to a low level. The low level may be interpreted as a level (e.g., 0 V) ​​sufficiently lower than the gate voltage. In this way, the DCDC control unit 19 is configured to control the on / off of the second FET 12 by changing the voltage level output from the high-side output terminal P1. Similarly, the DCDC control unit 19 controls the on / off of the third FET 13 by changing the output level of the low-side output terminal P2.

[0046] The DCDC control unit 19 further includes a feedback power supply connection terminal and a ground terminal. The feedback power supply connection terminal is connected to the first feedback line 35 and is a terminal to which the first feedback voltage Va is input. The ground terminal is a terminal connected to ground.

[0047] Furthermore, the DCDC control unit 19 includes an error amplifier 191 that compares the first feedback voltage Va with a predetermined reference voltage. The error amplifier 191 outputs a signal indicating the difference between the output voltage and the second voltage or the magnitude relationship between them. The reference voltage of the error amplifier 191 may be designed based on a value obtained by multiplying the second voltage by R2 / (R1+R2).

[0048] The DCDC control unit 19 determines the duty ratio (also called duty cycle) for PWM control based on the output of the error amplifier 191, and controls the on / off of the second FET 12 and the third FET 13. The switching frequency for PWM control may be 800 kHz, 1 MHz, or the like. The second FET 12 and the third FET 13 may be switching elements having performance corresponding to the required switching frequency.

[0049] The DCDC control unit 19 sets the third FET 13 to off when the second FET 12 is turned on, and sets the third FET 13 to on when the second FET 12 is turned off. A dead time may be provided so that the second FET 12 and the third FET 13 are not turned on simultaneously. During a period when the second FET 12 is on and the third FET 13 is off, a current flows to the inductor 14 via the second FET 12. Furthermore, even when the second FET 12 is off and the third FET 13 is turned on, a current flows from ground to the load connection terminal 20 via the inductor 14 and the third FET 13 due to the function of the inductor 14, which attempts to continue flowing a current.

[0050] The DCDC control unit 19 indirectly monitors the output voltage using the first feedback voltage Va and dynamically adjusts the duty cycle to keep the output voltage within a predetermined target range based on the second voltage. The target range may be, for example, 12 V ± 5%. The target range may also be 8 V ± 5%. The target range based on the second voltage is also referred to as a basic target range. The tolerance defining the basic target range is not limited to 5% and may be, for example, 3%.

[0051] The load connection terminal 20 is a terminal for electrically connecting to the load device 9. The load connection terminal 20 is electrically connected to a connector exposed on the outside of the housing of the zone ECU 1. A switch 201 may be interposed between the load connection terminal 20 and the connector connected to the load device 9 by cable. The output line 34 may also have branch paths connected to multiple load devices 9. A switch 201 may be provided midway in each branch path. The connection state of the switch 201 may be controlled by the load control unit 200.

[0052] The third resistor 21 and the fourth resistor 22 form a voltage divider circuit for inputting a voltage corresponding to the output voltage to the OVP control unit 23. The third resistor 21 and the fourth resistor 22 are connected in series between the output line 34 and ground. One end of the third resistor 21 is connected to the output line 34, and the other end is connected to one end of the fourth resistor 22. The other end of the fourth resistor 22 is connected to ground. The conductive line connecting the third resistor 21 and the fourth resistor 22 is connected to the OVP control unit 23 via the second feedback line 36. The total resistance value of the third resistor 21 and the fourth resistor 22 may be set to a sufficiently large value (e.g., 3 MΩ or more) so as to minimize the current flowing through the voltage divider circuit. If the resistance value of the third resistor 21 is R3 and the resistance value of the fourth resistor 22 is R4, R3 may be set to a value sufficiently larger than R4 (e.g., 8 to 10 times larger).

[0053] The second feedback line 36 is one of the conductive lines mounted on the printed circuit board. One end of the second feedback line 36 is connected to the downstream terminal of the third resistor 21, and the other end is connected to the OVP control unit 23. For convenience, the voltage of the second feedback line 36 is also referred to as a second feedback voltage Vb.

[0054] The resistance values ​​(R1, R2, R3, R4) of the first resistor 17, the second resistor 18, the third resistor 21, and the fourth resistor 22 may be designed so that the first feedback voltage Va and the second feedback voltage Vb are at the same level. For example, R1 and R3 may be the same, and R2 and R4 may be the same. Of course, the resistance values ​​of the first resistor 17, the second resistor 18, the third resistor 21, and the fourth resistor 22 may be designed so that the first feedback voltage Va and the second feedback voltage Vb are different values. R1, R2, R3, and R4 may be different from one another.

[0055] The OVP control unit 23 is configured to execute control to continue operation of the load device 9 while protecting the load device 9 when the output voltage exceeds a predetermined protection threshold due to an abnormality occurring in the DCDC conversion unit 101. The protection threshold is a voltage value corresponding to an overvoltage state. Such an OVP control unit 23 may be realized using an ASIC, a general-purpose IC, an FPGA, or the like. The OVP control unit 23 mainly corresponds to a driver that controls switches such as the first FET 11 and the fourth FET 16 that are additionally (in other words, auxiliary) provided to the DCDC conversion unit 101. The OVP control unit 23 corresponds to an auxiliary switch control unit. The OVP control unit 23 may also be called an auxiliary switch driver, etc.

[0056] The OVP control unit 23 is connected to the gate of the first FET 11 and the gate of the fourth FET 16. The OVP control unit 23 is configured to be able to apply a gate voltage to each of the gates of the first FET 11 and the fourth FET 16. That is, the OVP control unit 23 has an output terminal P3 electrically connected to the gate of the first FET 11 and an output terminal P4 electrically connected to the gate of the fourth FET 16. When the OVP control unit 23 applies a gate voltage to the gate of the first FET 11, the drain and source of the first FET 11 are in a conductive state (ON state). In contrast, when no gate voltage is applied, the drain and source of the first FET 11 are in a non-conductive state (OFF state). The OVP control unit 23 also controls the ON / OFF of the fourth FET 16 based on the presence or absence of a gate voltage.

[0057] The OVP control unit 23 also includes a feedback power supply connection terminal and a ground terminal. The feedback power supply connection terminal is connected to the second feedback line 36 and is a terminal to which the second feedback voltage Vb is input. The ground terminal is a terminal connected to ground. The OVP control unit 23 also includes an error amplifier 231 that compares the second feedback voltage Vb with a predetermined reference voltage.

[0058] The circuit module including the first FET 11, the fourth FET 16, and the OVP control unit 23 corresponds to the protection circuit unit 102 of this embodiment. The protection circuit unit 102 may also include the third resistor 21, the fourth resistor 22, and the second feedback line 36. To ensure visibility of the figures, the broken lines indicating the protection circuit unit 102 are omitted from Figure 3 and subsequent figures.

[0059] In the basic mode, the OVP control unit 23 monitors the output voltage generated by the DCDC conversion unit 101 based on the second feedback voltage Vb input from the second feedback line 36. The output voltage can be calculated backward from the second feedback voltage Vb, the resistance value of the third resistor 21, and the resistance value of the fourth resistor 22. If the resistance value of the third resistor 21 is R3 and the resistance value of the fourth resistor 22 is R4, the output voltage (Vout) may be calculated as Vout = α·Vb using α = (R3 + R4) / R4. Because the coefficient α is constant, the OVP control unit 23 may simply estimate the current output voltage by multiplying the second feedback voltage Vb by the coefficient α registered in advance.

[0060] The OVP control unit 23 then determines whether the output voltage of the DCDC conversion unit 40 is greater than a predetermined protection threshold. The protection threshold may be set based on the maximum operating voltage or the second voltage of the load device 9. The maximum operating voltage is the upper limit of a recommended operating voltage range determined by specifications. For example, in a configuration in which the second voltage is 12 V, the protection threshold may be set to 18 V, 16 V, or the like. The protection threshold corresponds to the first threshold. The OVP control unit 23 may also determine whether the output voltage exceeds the protection threshold by comparing the second feedback voltage Vb with the protection threshold multiplied by 1 / α.

[0061] When the OVP control unit 23 detects that the output voltage of the DCDC conversion unit 101 is higher than the protection threshold, it starts temporary control to keep the output voltage within a predetermined temporary target range. The temporary control includes PWM control of the first FET 11 instead of the second FET 12. Switching of the first FET 11 during the temporary control is performed in accordance with the output of the error amplifier 231. Here, switching does not mean a single switching from on to off or from off to on, but may be understood as control or operation of repeatedly switching on and off at a predetermined switching frequency. Details of the temporary control will be described separately below.

[0062] The OVP control unit 23 of this embodiment is configured to be able to input a synchronization signal to the DCDC control unit 19. The OVP control unit 23 may include a synchronization signal output terminal, and the DCDC control unit 19 may include a synchronization signal input terminal. The synchronization signal output terminal of the OVP control unit 23 is connected to the synchronization signal input terminal of the DCDC control unit 19 by a conductive line. The synchronization signal output terminal is a terminal for outputting a synchronization signal. The synchronization signal input terminal is a terminal to which the synchronization signal is input. The synchronization signal may be a signal that indicates the timing at which the OVP control unit 23 turns on and off the first FET 11.

[0063] The synchronization signal may be a signal whose voltage level rises and falls in conjunction with the on / off of the first FET 11. The synchronization signal may be a signal that takes dead time into consideration. The synchronization signal may be a signal with which the OVP control unit 23 instructs the DCDC control unit 19 to turn on and off the third FET 13. The DCDC control unit 19 may set the third FET 13 on in response to the falling edge of the synchronization signal, and may set the third FET 13 off in response to the rising edge of the synchronization signal. The synchronization signal is a signal that allows the OVP control unit 23 and the DCDC control unit 19 to cooperate so that the third FET 13 and the first FET 11 are not turned on simultaneously during execution of temporary control.

[0064] The OVP control unit 23 further includes a storage unit 232 that stores data indicating the number of times an abnormality has been detected in the power supply circuit 100. The storage unit 232 may be a non-volatile recording medium that allows stored data to be rewritten. The storage unit 232 may be a flash memory, an EEPROM (registered trademark, Electrically Erasable Programmable Read Only Memory), a ferroelectric memory, or the like. The storage unit 232 may also be a volatile memory such as a RAM (Random Access Memory).

[0065] The OVP control unit 23 may separately store the number of times an abnormality in the protection circuit unit 102 is detected and the number of times an abnormality in the DCDC conversion unit 101 is detected. An abnormality in the protection circuit unit 102 may be a short-circuit failure of the first FET 11 or the fourth FET 16. Hereinafter, the number of times an abnormality in the protection circuit unit 102 is detected may be referred to as the number of first error detections. As will be described later, abnormalities in the DCDC conversion unit 101 include (i) a short-circuit failure of the second FET 12, (ii) an open-circuit failure of the first resistor 17, (iii) a break in the first feedback line 35, and (iv) a ground fault in the first feedback line 35. Hereinafter, the number of times an abnormality in the DCDC conversion unit 101 is detected may be referred to as the number of second error detections.

[0066] The OVP control unit 23 checks the protection circuit unit 102 at startup, and if an error is detected in the protection circuit unit 102, increments the value of the first error detection count stored in the storage unit 232. The OVP control unit 23 also checks the DCDC conversion unit 101 at startup, and if an abnormality is detected in the DCDC conversion unit 101, increments the value of the second error detection count stored in the storage unit 232. Here, "increment" refers to the process of increasing the value by one. If the OVP control unit 23 detects an abnormality, it may notify a higher-level device (such as a central ECU) that an abnormality has occurred. Note that in other embodiments, the first error detection count and the second error detection count may be counted without distinction.

[0067] <Basic Mode> Here, the operation of the power supply circuit 100 in basic mode will be described. Basic mode is the operating mode of the power supply circuit 100 when no abnormality such as an output voltage exceeding the protection threshold occurs in the DCDC conversion unit 101. In other words, basic mode is the operating mode under normal conditions. The term "basic mode" may be replaced with "normal mode" or "normal mode." After startup, the power supply circuit 100 performs a predetermined check process, and if no abnormality is detected, begins operating in basic mode. Note that the power supply circuit 100 transitions to temporary mode when the OVP control unit 23 detects an overvoltage while operating in basic mode. An overvoltage may be understood as a voltage greater than the protection threshold. The temporary mode will be described separately below.

[0068] 3 is a diagram showing the state of each switch in the basic mode. In the basic mode, the OVP control unit 23 sets the first FET 11 to on and the fourth FET 16 to off. Then, the DCDC control unit 19 switches the second FET 12 and the third FET 13 based on the output of the error amplifier 191 (i.e., the first feedback voltage Va). As described above, switching can be understood as control that repeatedly turns on and off at a switching frequency.

[0069] As described above, in the fundamental mode, the DCDC control unit 19 generates the second voltage as the output voltage by switching the second FET 12. In the present embodiment, the generation of the second voltage in the fundamental mode also includes switching the third FET 13 so as to turn on the third FET 13 at a timing when the second FET 12 is off. The generation of the second voltage by switching includes alternately repeating a storage operation of storing energy in the inductor 14 and a release operation of releasing the energy stored in the inductor 14.

[0070] In the basic mode, the accumulation operation is an operation in which the second FET 12, which corresponds to a high-side switch, is set on and the third FET 13, which corresponds to a low-side switch, is set off. The accumulation operation causes current to flow from the power supply 8 to the load via the second FET 12 and inductor 14, and energy is accumulated in the inductor 14. The line indicated by 301 in Figure 3 indicates the current path to the inductor 14 during the accumulation operation.

[0071] In the basic mode, the discharge operation is an operation in which the second FET 12, which corresponds to a high-side switch, is set to off and the third FET 13, which corresponds to a low-side switch, is set to on. The discharge operation causes the energy stored in the inductor 14 to circulate through the third FET 13. The discharge operation can also be called a regeneration operation because it is an operation in which the energy stored in the inductor 14 is regenerated.

[0072] 3, if any one of (i) a short-circuit fault in the second FET 12, (ii) an open-circuit fault in the first resistor 17, (iii) a disconnection in the first feedback line 35, and (iv) a ground fault in the first feedback line 35 occurs, the output voltage may rise up to the first voltage. As a result, the load device 9 may suffer an overvoltage fault.

[0073] For these reasons, the power supply circuit 100 of this embodiment is configured to transition to temporary mode when the OVP control unit 23 detects that the output voltage is higher than the protection threshold in basic mode. (i) A short circuit failure of the second FET 12 refers to a failure in which current flows from the drain to the source of the second FET 12 even when no gate voltage is applied. An FET short circuit failure is not limited to a drain-source impedance of exactly 0 Ω. An FET short circuit failure may also include a state in which a minute resistance of several tens to several hundreds of Ω exists between the drain and source. In other words, a short circuit failure includes an incomplete short circuit failure. Furthermore, an open circuit failure or disconnection refers to a state in which the second resistor 18 is not electrically connected. (iv) A ground fault of the first feedback line 35 may also include a state in which the second resistor 18 is shorted.

[0074] FIG. 5 is a diagram showing the state of each switch in the temporary mode. FIG. 5 illustrates, as an example, a case where a short circuit fault occurs in the second FET 12. In the temporary mode, the OVP control unit 23 turns on the fourth FET 16 and then switches the first FET 11 based on the output of the error amplifier 231 (i.e., the second feedback voltage Vb). The line indicated by 302 in FIG. 5 indicates the current path to the inductor 14 during the accumulation operation in the temporary mode.

[0075] Furthermore, in the temporary mode, the OVP control unit 23 outputs a synchronization signal to the DCDC control unit 19. "Sg_Sync" in the figure indicates the synchronization signal. In accordance with the synchronization signal received from the OVP control unit 23, the DCDC control unit 19 executes switching control to set the third FET 13 on at the timing when the first FET 11 is turned off. Note that in the temporary mode, the DCDC control unit 19 sets the output of the high-side output terminal P1 to a low level. As a result, the path passing through the second FET 12 is disabled even if no short-circuit failure has occurred in the second FET 12.

[0076] In this way, in the temporary mode, the OVP control unit 23 switches the first FET 11 to keep the output voltage within the temporary target range. In this embodiment, the temporary control may be switching the first FET 11 while adjusting the duty cycle based on the second feedback voltage Vb. The state in which the temporary control is being performed may be considered to be the temporary mode.

[0077] The temporary control also includes repeatedly repeating a storage operation of storing energy in inductor 14 and a discharging operation of discharging the energy stored in inductor 14. The storage operation in the temporary mode (temporary control) of this embodiment is to set first FET 11 on and third FET 13 off. The discharging operation in the temporary mode of this embodiment is to set first FET 11 off and third FET 13 on.

[0078] In the temporary control, it is not necessary to set the third FET 13 on when the first FET 11 is off. Even if the third FET 13 remains off, the body diode of the third FET 13 can release energy. In other words, the temporary control may be step-down control using asynchronous rectification. However, energy efficiency can be improved by using synchronous rectification, which sets the third FET 13 on when the first FET 11 is off.

[0079] Hereinafter, the control of switching the first FET 11 while keeping the third FET 13 off will be referred to as asynchronous temporary control. Also, the control of turning the third FET 13 on in conjunction with turning off the first FET 11 will be referred to as synchronous temporary control. As an example, the OVP control unit 23 of this embodiment is configured to first perform asynchronous temporary control after detecting an overvoltage, and then transition to synchronous temporary control.

[0080] The target range of the output voltage in temporary control, i.e., the temporary target range, is defined based on the temporary target voltage. The temporary target voltage may be the same as the second voltage or a third voltage that is a predetermined amount higher than the second voltage. For example, if the second voltage is 12 V and the maximum operating voltage of the load device 9 is 18 V, the temporary target voltage may be set to 15 V. The protection threshold is a parameter that is valid only in the basic mode and may be disabled in the temporary mode. The temporary target voltage may be set to the same voltage as the protection threshold or to a voltage higher than the protection threshold. In one embodiment, the temporary target voltage may be set to 15 V, and the temporary target range may be set to 15 V ±8%. The tolerance of the temporary target range is not limited to 8% and may be 6%, 10%, or the like. The tolerance of the temporary target range may be set to be larger than the tolerance defining the basic target range.

[0081] The error amplifier 231 of the OVP control unit 23 may be configured to output a signal indicating the difference between the current output voltage and the temporary target voltage or the magnitude relationship between them. The reference voltage input to the error amplifier 231 may be designed based on a value obtained by multiplying the temporary target voltage by R4 / (R3+R4).

[0082] In one embodiment, the temporary target voltage may be set several volts higher than the basic target voltage (i.e., the second voltage). In a situation where an overvoltage-type abnormality occurs in the power supply circuit 100, the load control unit 200 may operate only the minimum number of load devices 9 necessary and stop the load devices 9 that are less necessary. In this case, the current value flowing through the load devices 9 may be smaller than the current value in the basic mode. By increasing the output voltage by the amount of the reduced current, it is possible to maintain the required amount of power.

[0083] <Operation Sequence> Next, the operation of the zone ECU 1 will be described with reference to the flowcharts shown in Figures 6 and 7. The flowchart shown in Figure 6 may be started when the power supply from the power source 8 to the zone ECU 1 is started or when a start signal is input from the central ECU 7.

[0084] In step S101, the OVP control unit 23 reads the value of the first error detection count stored in the memory unit 232 and determines whether it is less than a predetermined first threshold. In the figure, "Err1_Num" represents the first error detection count, i.e., the number of times an abnormality in the first FET 11 has been detected. Furthermore, "Th1" represents the first threshold. The first threshold may be set to, for example, 20 or 40 times. The first threshold is a parameter for determining whether a short circuit failure in the first FET 11 is temporary (accidental) or permanent. The first threshold can also be interpreted as a threshold for abandoning operation of the power supply circuit 100 (and thus power supply to the load device 9). If the first error detection count is less than the first threshold, processing proceeds to step S102. On the other hand, if the first error detection count is equal to or greater than the first threshold, processing proceeds to step S111.

[0085] In step S102, the OVP control unit 23 reads the value of the number of second error detections stored in the memory unit 232 and determines whether the value is less than a predetermined second threshold. In the figure, "Err2_Num" represents the number of second error detections, i.e., the number of times an abnormality in the DCDC conversion unit 101 has been detected. Furthermore, "Th2" represents the second threshold. The second threshold may be set to, for example, 20 or 40 times. The second threshold is a parameter for determining whether an abnormality occurring in the DCDC conversion unit 101 is temporary (accidental) or permanent. The second threshold can also be interpreted as a threshold for abandoning operation of the power supply circuit 100. If the number of second error detections is less than the second threshold, processing proceeds to step S103. On the other hand, if the number of second error detections is equal to or greater than the second threshold, processing proceeds to step S111.

[0086] In step S103, the OVP control unit 23 sets the first FET 11 to OFF to check whether the first FET 11 has a short circuit. At this time, the connection states of the second FET 12, the third FET 13, and the fourth FET 16 may be set in any manner. This is because no current flows if the first FET 11 is normal, i.e., if no short circuit has occurred. However, if the first FET 11 has a short circuit, a large current may flow if either the second FET 12 or the fourth FET 16 is ON and the third FET 13 is also ON. For this reason, the second FET 12, the third FET 13, and the fourth FET 16 may all be set to OFF in step S103. In FIGS. 6 and 7, "FET1" refers to the first FET 11, "FET2" refers to the second FET 12, "FET3" refers to the third FET 13, and "FET4" refers to the fourth FET 16, respectively.

[0087] After step S103, in step S104, the OVP control unit 23 determines whether the source voltage of the first FET 11 is 0 V. Here, 0 V is not limited to completely 0 V, but may also include non-zero voltage values ​​that can be considered substantially low. For example, 0.3 V or 0.5 V may also be considered 0 V. If the first FET 11 has a short circuit fault, the source voltage of the first FET 11 can be a sufficiently high value. On the other hand, if the first FET 11 does not have a short circuit fault, the source voltage of the first FET 11 is 0 V. In other words, if the source voltage of the first FET 11 is not 0 V, it means that a short circuit fault has occurred in the first FET 11.

[0088] Note that the OVP control unit 23 of this embodiment does not have a conductive line or terminal for directly referencing the source voltage of the first FET 11. The OVP control unit 23 may perform the determination of step S104 by regarding the second feedback voltage Vb as the source voltage. That is, the OVP control unit 23 may determine that the source voltage of the first FET 11 is 0 V based on the second feedback voltage Vb being 0 V. In other words, the OVP control unit 23 may determine that the first FET 11 does not have a short-circuit fault based on the second feedback voltage Vb being 0 V. Note that in other embodiments, the power supply circuit 100 may be provided with a conductive line through which the source voltage of the first FET 11 is input to the OVP control unit 23.

[0089] If OVP control unit 23 detects in step S104 that the source voltage of first FET 11 is not 0 V, it executes step S105. On the other hand, if OVP control unit 23 detects in step S104 that the source voltage of first FET 11 is 0 V, it executes step S106.

[0090] In step S105, the OVP control unit 23 increments the value of the number of first error detections stored in the storage unit 232. After completing the process of step S105, the OVP control unit 23 may re-execute the processes from step S101 onwards after a certain period of time.

[0091] In step S106, a process is executed to check the second FET 12 and the fourth FET 16. Specifically, the DCDC control unit 19 sets the second FET 12 to OFF. Furthermore, the OVP control unit 23 sets the first FET 11 to ON and the fourth FET 16 to OFF. If both the second FET 12 and the fourth FET 16 are normal, i.e., if no short-circuit fault occurs, no current flows. Therefore, the third FET 13, which is located downstream of the second FET 12, may be either ON or OFF. However, if the third FET 13 is set to ON in the unlikely event that either the second FET 12 or the fourth FET 16 has a short-circuit fault, a large current may flow through the third FET 13. In consideration of such concerns, the third FET 13 may be set to OFF in step S106.

[0092] When the switch control in step S106 is completed, the process proceeds to step S107. Note that the process of step S106 may be executed in cooperation with the OVP control unit 23 and the DCDC control unit 19 by communicating with each other via a communication line (not shown). For example, the OVP control unit 23 may control the on / off of the second FET 12 and the third FET 13 by issuing an instruction to the DCDC control unit 19. The DCDC control unit 19 and the OVP control unit 23 may control the connection state (on / off) of each switch according to a predetermined schedule without communicating with each other.

[0093] In step S107, the OVP control unit 23 determines whether the output voltage (Vout) is 0 V. For example, the OVP control unit 23 may determine that the output voltage is 0 V based on the second feedback voltage Vb being 0 V. Note that step S107 may also be a step in which the DCDC control unit 19 determines that the output voltage is 0 V based on the first feedback voltage Va being 0 V.

[0094] If it is confirmed in step S107 that the output voltage is 0 V, the process proceeds to step S108. On the other hand, if it is confirmed in step S107 that the output voltage is not 0 V, the process proceeds to step S112. In step S112, the OVP control unit 23 increments the value of the number of second error detections stored in the storage unit 232. When the process of step S112 is completed, the process proceeds to step S120.

[0095] In step S108, the power supply circuit 100 starts operating in basic mode. That is, the DCDC control unit 19 monitors the first feedback voltage Va and alternately sets the second FET 12 and the third FET 13 to ON. The length of the period during which the second FET 12 is set to ON, i.e., the duty cycle, may be automatically adjusted based on the result of comparing the first feedback voltage Va output by the error amplifier 191 with a reference voltage. Through this basic operation as a switching regulator, the output voltage falls within a predetermined range determined based on the second voltage.

[0096] After step S108, the OVP control unit 23 checks in step S109 whether the output voltage is equal to or less than the protection threshold. Step S109 may be performed at a predetermined sampling interval. The sampling interval may be, for example, several milliseconds. "Vpr" in the figure represents the protection threshold. If the output voltage is equal to or less than the protection threshold (YES in S109), it is determined in step S110 whether a stop command has been input from the central ECU 7. Step S110 may be executed by the OVP control unit 23 or the DCDC control unit 19. A stop command may be input, for example, when the vehicle is parked and the vehicle power supply is turned off.

[0097] When the zone ECU 1 receives a stop command from the central ECU 7, the zone ECU 1 executes a predetermined stop process in step S111. The stop process is a process for stopping (terminating) operation, and the specific content of the stop process may be designed as desired. The stop process may be a process of turning off each switch in a predetermined order so that the zone ECU 1 terminates normally. The stop process may include setting the first error detection count and the second error detection count stored in the memory unit 232 to zero.

[0098] Operation in the basic mode may continue until a stop command is received or until it is detected in step S109 that the output voltage exceeds the protection threshold. If the OVP control unit 23 detects that the output voltage exceeds the protection threshold in step S109 (S109 NO), the process proceeds to step S120. Monitoring of the output voltage may be performed not only by the OVP control unit 23 but also by the DCDC control unit 19. The DCDC control unit 19 may sequentially determine whether the output voltage is equal to or lower than the protection threshold based on the first feedback voltage Va.

[0099] Step S120 is a step in which the zone ECU 1 executes overvoltage response processing. Note that part or all of the overvoltage response processing may be executed by the OVP control unit 23 and the DCDC control unit 19 in cooperation with each other. Depending on the content of the overvoltage response processing, the OVP control unit 23 and the DCDC control unit 19 may be executed without cooperation with each other. Also, part of the overvoltage response processing may be executed by the load control unit 200. The overvoltage response processing may include steps S121 to S130, as shown in FIG. 7 .

[0100] Step S121 is a step in which the load control unit 200 cuts off the power supply to the normal load. The power supply may be cut off by turning off the switch 201. Step S121 may also be a step in which the function of the normal load is stopped. By executing step S121, the power supply destination is limited to the priority load. This reduces the amount of current that needs to flow from the load connection terminal 20 to the load side.

[0101] In step S121 or before, the OVP control unit 23 may notify the load control unit 200 and the central ECU 7 that an overvoltage has occurred. The overvoltage response process may include notifying the load control unit 200, the central ECU 7, or both of them that an overvoltage has occurred. Upon receiving the overvoltage occurrence notification from the OVP control unit 23, the load control unit 200 may start load limitation.

[0102] Upon receiving the overvoltage occurrence notification, the central ECU 7 may display an image on the display indicating that an abnormality has occurred in the vehicle. The display may be an in-vehicle display. This allows vehicle occupants to recognize that an abnormality has occurred in the power supply circuit 100. If the vehicle is a service vehicle, the display indicating the abnormality may be a display installed in the operation management center. This configuration allows the vehicle manager to recognize in real time that an abnormality has occurred in the vehicle's power system. Alternatively, upon receiving the overvoltage occurrence notification, the central ECU 7 may notify a specific server that an abnormality has occurred. The process of notifying occupants or managers of a power supply abnormality may be performed by the zone ECU 1 (e.g., the OVP control unit 23). Notifying a higher-level ECU of the overvoltage occurrence notification or displaying an image indicating a power supply abnormality on the display corresponds to the process of notifying the user of the abnormality. After step S121 is completed, the process proceeds to step S122. Note that step S121 is optional and may be omitted.

[0103] In step S122, the OVP control unit 23 turns off the first FET 11. This disconnects the circuitry following the first FET 11 from the power supply line 30. After turning off the first FET 11, the OVP control unit 23 then turns on the fourth FET 16 in step S123. This creates a current path that does not pass through the second FET 12.

[0104] Step S122 may include the DCDC control unit 19 setting the output voltage to the gate of the second FET 12 to a low level. That is, step S122 may include setting the output level of the high-side output terminal P1 to a low level. As a result, the second FET 12 is set to off. The output level control of the high-side output terminal P1 may be executed by the DCDC control unit 19 in response to an instruction from the OVP control unit 23. Alternatively, if the DCDC control unit 19 itself has a function for monitoring the output voltage, the DCDC control unit 19 may voluntarily stop switching of the second FET 12 and set the second FET 12 to off when the output voltage exceeds the protection threshold. Step S122 may also include setting the third FET 13 to off.

[0105] When the OVP control unit 23 sets the fourth FET 16 to ON, in step S124, it determines whether the output voltage has dropped below a predetermined safety threshold. "Vsf" in the figure represents the safety threshold. The safety threshold may be set to a value smaller than the protection threshold. The safety threshold may be set to 1.1 times the second voltage, or may be set to a value higher than the second voltage by a predetermined amount (for example, 1 V). The safety threshold may be the same value as the second voltage or the temporary target voltage, or may be a value lower than them. For example, the safety threshold may be set to 13 V. The safety threshold corresponds to the second threshold.

[0106] If the output voltage has not fallen below the predetermined safety threshold in step S124, the OVP control unit 23 determines in step S125 whether a certain time has elapsed since the fourth FET 16 was set to on. The processes of steps S124 to S125 may be repeatedly executed until a certain time has elapsed since the fourth FET 16 was turned on or until the output voltage falls below the safety threshold. If the output voltage has not fallen below the safety threshold even after a certain time has elapsed since the fourth FET 16 was turned on (YES in S125), the OVP control unit 23 executes step S126.

[0107] In step S126, the OVP control unit 23 increments the value of the first error detection count stored in the memory unit 232. This is because the fact that the output voltage does not fall below the safety threshold even after a certain time has passed since the fourth FET 16 was turned on indicates that the first FET 11 has experienced a short-circuit fault. After step S126 is completed, the OVP control unit 23 may execute the processing from step S101 onward in FIG. 6 after a certain time has passed.

[0108] On the other hand, if the output voltage falls below the safety threshold before a certain time has elapsed since the fourth FET 16 was turned on (YES in S124), the OVP control unit 23 executes step S127. In step S127, the OVP control unit 23 starts switching the first FET 11 based on the second feedback voltage Vb. At this time, the third FET 13 is set to off, and therefore functions as a diode that allows current to flow in a direction from ground to the second relay line 32. In other words, step S127 corresponds to a step of starting DCDC conversion using asynchronous rectification (in other words, asynchronous temporary control).

[0109] The OVP control unit 23 starts switching the first FET 11, and after performing the discharge operation at least once, confirms in step S128 that the output voltage is within the temporary target range. For example, the OVP control unit 23 determines whether the output voltage is within the temporary target range when the discharge operation has been performed five or ten times. If it is confirmed that the output voltage is within the temporary target range, the OVP control unit 23 starts outputting a synchronization signal to the DCDC control unit 19 in step S129. This starts synchronous temporary control in which the OVP control unit 23 and the DCDC control unit 19 cooperate, and the temporary target voltage is supplied to the load device 9. By performing step-down control using synchronous rectification, energy efficiency can be improved.

[0110] As described above, when the voltage generated by the DCDC converter 101 reaches an overvoltage level, the power supply circuit 100 transitions from the basic mode to the temporary mode and attempts to generate power using asynchronous rectification or synchronous rectification. This allows the load device 9 to continue operating even when an abnormality related to overvoltage occurs in the power supply circuit 100.

[0111] 6 is executed, and the zone ECU 1 stops operating. Also, during the temporary mode, the OVP control unit 23 monitors whether the output voltage is within the temporary target range. If the output voltage deviates from the temporary target range by a predetermined amount, or if the state in which the output voltage deviates from the temporary target range by a predetermined amount continues for a predetermined period of time, the OVP control unit 23 may set the first FET 11 to OFF and stop operating.

[0112] <Effects> With the above configuration, even if an abnormality occurs in the DCDC conversion unit 101 and the output voltage becomes an overvoltage state, it is possible to continue operation of important load devices 9. For example, safety-related devices such as driving assistance devices and autonomous driving devices can continue to operate. Furthermore, in an autonomous driving system, it is possible to reduce the risk that an abnormality in the power supply system will make it impossible to perform evacuation control or emergency control such as MRM (Minimal / Minimum Risk Maneuver).

[0113] Furthermore, during the overvoltage response process, if a voltage equal to or greater than a predetermined value (i.e., the safety threshold) continues to be output even after the first FET 11 is set to OFF (YES in S125), the OVP control unit 23 does not initiate emergency control. This reduces the impact on the load. Furthermore, if a voltage equal to or greater than the safety threshold continues to be output even after the first FET 11 is set to OFF, this indicates that the fourth FET 16, which was introduced as an overvoltage countermeasure, may have experienced a short circuit. This control reduces the risk of emergency control being performed when the fourth FET 16 has experienced a short circuit. Furthermore, if it is confirmed that the output voltage has dropped after the first FET 11 is set to OFF, emergency control can be performed to continue power supply to the load device 9.

[0114] The power supply circuit 100 of this embodiment also includes a fourth FET 16 connected in parallel to the second FET 12 as a high-side switch. In the emergency mode, the fourth FET 16 is set to on and the first FET 11 starts switching. This prevents current from flowing through the second FET 12 even if the second FET 12 has a low resistance and is short-circuited. This reduces the risk of the second FET 12 being damaged by Joule heat.

[0115] If the cause of the short circuit failure in the first FET 11 is liquid such as condensation, foreign metal particles, high temperature, or the like, the first FET 11 may be restored to normal by repeatedly turning the first FET 11 on and off several times. In other words, if the short circuit failure in the first FET 11 is due to a temporary cause, the number of first error detections is expected to be less than the specified number. On the other hand, if the first FET 11 is shorted due to a complete failure, the first FET 11 will not recover even if the gate voltage is turned on and off multiple times. If the number of first error detections is equal to or greater than the specified number, it means that there is a high possibility that the first FET 11 has completely failed.

[0116] For this reason, in steps S103 and S104 of the startup process, the OVP control unit 23 of this embodiment checks whether a short circuit has occurred in the first FET 11. If it is determined that a short circuit has occurred in the first FET 11, the OVP control unit 23 increments the first error detection count. The OVP control unit 23 then stops operation if the first error detection count exceeds a predetermined value. In other words, the zone ECU 1 does not transition to the basic mode if there is a history of detecting an error a certain number of times or more. This makes it possible to prohibit power supply to the load device 9 when the first FET 11 is in a faulty state.

[0117] In this embodiment, the fourth FET 16 is used to form a current path that bypasses the second FET 12. Even during a short circuit, the second FET 12 is expected to have a small resistance (e.g., several tens of ohms). If the second FET 12 has a relatively small resistance, it may burn if a current flows through it. In response to such concerns, the configuration of this embodiment reduces the risk of the second FET 12 burning. A short circuit is an accidental abnormality that may recover over time. In contrast, a burn is an irreversible failure that requires repair, such as replacing a component or board. Introducing the fourth FET 16 reduces the risk of an accidental short circuit escalating into a burn (complete failure).

[0118] Furthermore, even if second FET 12 is completely shorted, it may be unclear whether it is safe to continue to pass current through second FET 12, which is experiencing a short circuit. By bypassing the current through fourth FET 16 when an abnormality occurs in second FET 12, it is possible to ensure the stability and safety of operation.

[0119] Furthermore, the fourth FET 16 is not used for high-speed switching for stepping down. Therefore, the fourth FET 16 may be an inexpensive switching element that can support a relatively low switching frequency. In other words, the switching element introduced as the second auxiliary switch may be a switching element with lower performance than the high-side switch. This reduces the increase in manufacturing costs of the power supply circuit 100.

[0120] In the basic mode, the first FET 11 is also set to be always on and is not switched. The first FET 11 is merely an element used for temporary switching to step down the voltage. Therefore, the first FET 11 does not need to be a switching element with as high performance as the second FET 12 used as a high-side switch. The switching element used as the first auxiliary switch may also be a switching element with lower performance than the high-side switch. This reduces the increase in manufacturing costs of the power supply circuit 100.

[0121] In this embodiment, the load control unit 200 throttles the loads to which power is supplied based on the detection of an overvoltage. For example, the load control unit 200 maintains the supply of power only to the priority load 9a and stops the supply to the normal load 9b. This reduces the amount of current that needs to flow through the load connection terminal 20. As a result, the amount of current flowing through the fourth FET 16 is also reduced. As a result, the fourth FET 16 may be a switching element with a smaller maximum current than the second FET 12. In other words, the configuration that throttles the loads to which power is supplied in the emergency mode allows a relatively small and inexpensive switching element to be used as the fourth FET 16.

[0122] The first FET 11 or the fourth FET 16 may be an FET having performance (switching frequency and maximum current) equivalent to that of the second FET 12. If the first FET 11 has performance equivalent to that of the second FET 12, heat generation due to switching of the first FET 11 is reduced. If the short circuit failure of the second FET 12 is caused by high temperature, the risk of the first FET 11 itself being damaged by switching of the first FET 11 can be reduced.

[0123] <Modification of First Embodiment> When the OVP control unit 23 detects an overvoltage, it may execute a process to determine whether the overvoltage is due to (i) a short-circuit failure of the second FET 12 or another reason. The other reasons include (ii) an open-circuit failure of the first resistor 17, (iii) a disconnection of the first feedback line 35, or (iv) a ground fault of the first feedback line 35. For example, when the OVP control unit 23 or the DCDC control unit 19 detects an overvoltage, the OVP control unit 23 causes the DCDC control unit 19 to turn off the second FET 12 and the third FET 13, and then turns on the first FET 11 and the fourth FET 16. If the output voltage is 0 V or higher with this switch setting, it can be determined that the cause of the overvoltage is a short-circuit failure of the second FET 12. Furthermore, if the output voltage is 0 V with the above switch setting, the OVP control unit 23 may determine that the cause of the overvoltage is any of (ii), (iii), and (iv).

[0124] If it is determined that the cause of the overvoltage is any one of (ii), (iii), and (iv) and that the second FET 12 is normal, the OVP control unit 23 may switch the first FET 11 based on the second feedback voltage Vb while the second FET 12 is set to on. If the second FET 12 is normal, the fourth FET 16 may not be necessary as a bypass.

[0125] The second feedback voltage Vb may also be configured to be input to the DCDC control unit 19. If the DCDC control unit 19 determines that the second FET 12 is normal after detecting an overvoltage, it may perform switching of the second FET 12 and the third FET 13 based on the second feedback voltage Vb with the first FET 11 set to on. When the DCDC control unit 19 performs switching based on the second feedback voltage Vb, a circuit equivalent to the error amplifier 231 may also be implemented in the DCDC control unit 19. Such a configuration corresponds to a configuration in which the voltage feedback circuit in the DCDC conversion unit 101 is duplicated.

[0126] The fourth FET 16 connected in parallel with the second FET 12 as a high-side switch is an optional element and may be omitted, for example, as shown in FIG. 8 . This configuration can be useful as a countermeasure against overvoltages caused by abnormalities in the DCDC converter 101, such as (ii) an open circuit failure of the first resistor 17, (iii) a break in the first feedback line 35, and (iv) a ground fault in the first feedback line 35. Even if the second FET 12 experiences a short circuit failure, power supply through temporary control can continue until the second FET 12 burns out and becomes completely open. If the fourth FET 16 is not provided, the DCDC controller 19 continues to set the second FET 12 to on in the temporary mode.

[0127] Each of the multiple switching elements included in the power supply circuit 100 of the first embodiment is not limited to an N-channel MOSFET. The switching elements may be P-channel MOSFETs, GaNFETs, SiC-MOSFETs, bipolar transistors, or other types of switching elements. The modified examples of the first embodiment described above may be modified as appropriate and applied to the second embodiment described below.

[0128] Second Embodiment The configuration of the power supply circuit 100 is not limited to the configuration shown in Fig. 2 etc. The power supply circuit 100 may have the configuration shown in Fig. 9. Fig. 9 shows the power supply circuit 100 according to a second embodiment.

[0129] 9 and 2 , the configuration of the DCDC conversion unit 101 is similar between the second embodiment and the first embodiment. The power supply circuit 100 in the second embodiment and the power supply circuit 100 in the first embodiment differ in the position of the auxiliary switch connected to the OVP control unit 23. The power supply circuit 100 in the second embodiment includes a first protection switch 51 and a second protection switch 52 instead of the first FET 11 and the fourth FET 16.

[0130] In the description of the second embodiment, in order to avoid confusion between components derived from the prefixes "first" and "second," the second FET 12 included in the DCDC conversion unit 40 will also be referred to as the high-side switch 12, and the third FET 13 will also be referred to as the low-side switch 13. The description of the first embodiment may be used as appropriate to describe the high-side switch 12 and the low-side switch 13.

[0131] The first protection switch 51 and the second protection switch 52 may be N-channel MOSFETs, similar to the first FET 11. Of course, the first protection switch 51 and the second protection switch 52 may each be another type of switching element.

[0132] The first protection switch 51 is a switching element provided between the power supply 8 and the upstream terminal of the low-side switch 13. That is, the first protection switch 51 connects the power supply line 30 to the third relay line 33 or the second relay line 32. The drain of the first protection switch 51 is connected to the power supply line 30. The source of the first protection switch 51 is electrically connected to the drain of the low-side switch 13 and the upstream terminal of the inductor 14. For example, the source of the first protection switch 51 is connected to the third relay line 33 or the second relay line 32.

[0133] The gate of the first protection switch 51 is connected to the OVP control unit 23. The on / off of the first protection switch 51 is controlled by the OVP control unit 23. In the second embodiment, as will be described later, the first protection switch 51 is a switching element that is switched in place of the high-side switch 12 in the emergency mode. Therefore, the first protection switch 51 may be referred to as an alternative switch or an alternative FET. The first protection switch 51 remains set to off in the basic mode.

[0134] The second protection switch 52 is a switching element provided between the power supply 8 and the upstream terminal of the high-side switch 12. The drain of the second protection switch 52 is connected to the power supply line 30. The source of the second protection switch 52 is electrically connected to the drain of the high-side switch 12 via the first relay line 31. That is, in the second embodiment, the drain of the high-side switch 12 is connected to the power supply line 30 via the second protection switch 52. The gate of the second protection switch 52 is connected to the OVP control unit 23. The on / off of the second protection switch 52 is controlled by the OVP control unit 23.

[0135] As is clear from the above description, the second protection switch 52 is a switching element having substantially the same connection relationship as the first FET 11 in the first embodiment. However, the element that is switched in the temporary mode of the second embodiment is the first protection switch 51, not the second protection switch 52. In other words, although the second protection switch 52 is a switching element provided in the same position as the first FET 11, its role is different. The second protection switch 52 remains on in the basic mode. Furthermore, the second protection switch 52 remains off in the temporary mode.

[0136] Fig. 10 is a diagram showing the setting / operation of each switch in the basic mode of the second embodiment. In the basic mode, the OVP control unit 23 continues to set the first protection switch 51 to OFF and the second protection switch 52 to ON. Then, the DCDC control unit 19 switches the high-side switch 12 and the low-side switch 13 based on the output of the error amplifier 191 (i.e., the first feedback voltage Va). 401 in Fig. 10 indicates an example of a current path in the basic mode of the second embodiment.

[0137] 11 is a diagram showing the setting / operation of each switch in the temporary mode. In the temporary mode, the OVP control unit 23 sets the second protection switch 52 to OFF, and then switches the first protection switch 51 based on the output of the error amplifier 231 (i.e., the second feedback voltage Vb). 402 in FIG. 11 shows an example of a current path in the temporary mode of the second embodiment.

[0138] Even in the temporary mode of the second embodiment, the OVP control unit 23 may output a synchronization signal to the DCDC control unit 19. "Sg_Sync" in FIG. 11 indicates a synchronization signal. The DCDC control unit 19 executes switch control to intermittently turn on the low-side switch 13 when the first protection switch 51 is turned off, in accordance with the synchronization signal received from the OVP control unit 23. Note that in the second embodiment, if the second protection switch 52 is set to off, the current path passing through the second protection switch 52, the first relay line 31, and the high-side switch 12 is basically disabled regardless of whether the high-side switch 12 is on or off. Therefore, in the temporary mode of the second embodiment, the output of the high-side output terminal P1 may be either high or low. However, considering the possibility that the second protection switch 52 may have a short-circuit failure, the DCDC control unit 19 may set the high-side switch 12 to off. This reduces the risk of a large current flowing from the power supply line 30 to the low-side switch 13.

[0139] <Operation Sequence> Next, the operation of the zone ECU 1 of the second embodiment will be described with reference to the flowcharts shown in Figures 12 and 13. The flowchart shown in Figure 12 may be started when power supply from the power source 8 to the zone ECU 1 is started or when a start signal is input from the central ECU 7. The flowchart shown in Figure 12 starts from step S201.

[0140] Steps S201 and S202 are similar to steps S101 and S102 described above, and therefore description thereof will be omitted. The OVP control unit 23 executes step S203 when the number of first error detections stored in the storage unit 232 is equal to or less than the first threshold and the number of second error detections is equal to or less than the second threshold. In step S203, the OVP control unit 23 checks the auxiliary switches. Specifically, it sets both the first protection switch 51 and the second protection switch 52 to off. Note that if the high-side switch 12 is off, no abnormal voltage is observed even if a short-circuit fault occurs in the second protection switch 52. Step S203 may include the DCDC control unit 19 setting the high-side switch 12 to on. Furthermore, in case a short-circuit fault occurs in the first protection switch 51 or the second protection switch 52, step S203 may include the DCDC control unit 19 setting the low-side switch 13 to off.

[0141] Step S204, which follows step S203, is a step in which the OVP control unit 23 determines whether the output voltage is 0 V in the switch setting of step S203. The OVP control unit 23 may determine that the output voltage is 0 V based on the second feedback voltage Vb being 0 V. If the OVP control unit 23 detects that the output voltage is not 0 V, it increments the first error detection count in step S205. Step S205 corresponds to step S105.

[0142] On the other hand, when the OVP control unit 23 detects that the output voltage is 0 V, it checks the DCDC conversion unit 101 in step S206. Specifically, in step S206, the OVP control unit 23 sets the first protection switch 51 to OFF and sets the second protection switch 52 to ON. Also in step S206, the DCDC control unit 19 sets both the high-side switch 12 and the low-side switch 13 to OFF. Then, in step S207, the OVP control unit 23 determines whether the output voltage is 0 V.

[0143] If the OVP control unit 23 detects in step S207 that the output voltage is not 0 V, it increments the second error detection count in step S212 and executes step S220. Step S212 corresponds to step S112. On the other hand, if the OVP control unit 23 detects in step S207 that the output voltage is 0 V, it executes steps S208 to S211 in the order shown in the flow. Steps S208 to S211 correspond to the processes in steps S108 to S111, and therefore will not be described here. When applying the descriptions in FIGS. 6 and 7 to the descriptions in FIGS. 12 and 13, the second FET 12 may be interpreted as the high-side switch 12, and the third FET 13 may be interpreted as the low-side switch 13. If the OVP control unit 23 detects that the output voltage exceeds the protection threshold (Vpr) while repeating steps S209 to S210, it executes the overvoltage response process in step S220.

[0144] The overvoltage response processing in step S220 is generally similar to the overvoltage response processing in step S120. The overvoltage response processing in the second embodiment includes steps S221 to S230 as shown in FIG. 13 . Step S221 corresponds to step S121. In step S221, the load control unit 200 narrows down the destinations to which power is supplied. In step S222, the OVP control unit 23 sets the second protection switch 52 to OFF. In step S223, the OVP control unit 23 sets the first protection switch 51 to OFF. Furthermore, the DCDC control unit 19 sets the low-side switch 13 to OFF. In step S223, the DCDC control unit 19 may set the high-side switch 12 to OFF. Because the second protection switch 52 is OFF, the high-side switch 12 may be ON or OFF. When the overvoltage response processing is started, the first protection switch 51 is originally OFF. Therefore, the operation to turn OFF the first protection switch 51 may be omitted.

[0145] Steps S224 to S226 correspond to steps S124 to S126. If the output voltage does not fall below the safety threshold even after a certain time has elapsed since the second protection switch 52 was turned off (YES in S225), the OVP control unit 23 executes step S226. Step S226 is a step of incrementing the number of first error detections. After step S226 is completed, the OVP control unit 23 re-executes the processing from step S201 onwards after a certain time has elapsed.

[0146] On the other hand, if the output voltage falls below the safety threshold before the predetermined time has elapsed since the second protection switch 52 was turned off (YES in S224), the OVP control unit 23 executes the processes from step S227 onward. In step S227, the OVP control unit 23 starts switching the first protection switch 51 based on the second feedback voltage Vb. At this time, the low-side FET is set to off and therefore functions as a diode. In other words, step S227 corresponds to the step of starting DCDC conversion using asynchronous rectification (in other words, asynchronous temporary control).

[0147] The OVP control unit 23 starts switching the first protection switch 51 and performs the discharge operation at least once. For example, the OVP control unit 23 performs the discharge operation five times. Thereafter, the OVP control unit 23 confirms in step S228 that the average value of the output voltage is within the temporary target range. Upon confirming that the output voltage is within the temporary target range, the OVP control unit 23 starts outputting a synchronization signal to the DCDC control unit 19 in step S229. This initiates synchronized temporary control in which the OVP control unit 23 and the DCDC control unit 19 cooperate with each other. In other words, the temporary target voltage is supplied to the load device 9. In this way, in the second embodiment as well, the load device 9 can continue to operate even in a situation where an abnormality related to overvoltage has occurred in the power supply circuit 100.

[0148] If the OVP control unit 23 receives a stop command from the central ECU 7 during synchronous temporary control (YES in S230), step S211 in FIG. 12 is executed, and the zone ECU 1 stops operating. Also, during temporary mode, the OVP control unit 23 monitors whether the output voltage is within the temporary target range. If the output voltage significantly deviates from the temporary target range or if the output voltage continues to deviate from the temporary target range by a predetermined amount for a predetermined period of time, the OVP control unit 23 may turn off the first protection switch 51 and stop operation.

[0149] <Effects> The second embodiment described above also provides the same effects as the first embodiment described above. Furthermore, in the emergency mode, the second protection switch 52 remains off, and no current flows through the second protection switch 52. This makes it possible to prevent the second protection switch 52 and the high-side switch 12 located downstream from being burned out.

[0150] Furthermore, the second protection switch 52 is not used for high-speed switching for stepping down. Therefore, the second protection switch 52 may be an inexpensive switching element with a relatively low switching frequency. Because the protection switch may be a switching element with lower performance than the high-side switch, an increase in the manufacturing cost of the power supply circuit 100 can be reduced.

[0151] In the basic mode, the first protection switch 51 is also set to be always on and is not switched. The first protection switch 51 is merely an element used for temporary switching to step down the voltage when an abnormality occurs in the DCDC conversion unit 101. Therefore, the first protection switch 51 does not need to be a switching element with as high performance as the high-side switch 12. This can reduce the increase in manufacturing costs of the power supply circuit 100.

[0152] <Modification of Second Embodiment> The first protection switch 51 may be a P-channel MOSFET. However, when comparing a P-channel MOSFET and an N-channel MOSFET having the same level of rated current, the P-channel MOSFET may generally be larger in element size than the N-channel MOSFET. By employing an N-channel MOSFET as the first protection switch 51, it is possible to reduce the size of the circuit board.

[0153] The first protection switch 51 is not limited to an N-channel MOSFET or a P-channel MOSFET, and may be any of various other switching elements. The first protection switch 51 may be a GaNFET, a SiC-MOSFET, a bipolar transistor, etc. The second protection switch 52 is also not limited to an N-channel MOSFET, and may be any of various other switching elements.

[0154] [Modifications / Supplements Common to the First and Second Embodiments] When the OVP control unit 23 detects an overvoltage output from the DCDC conversion unit 101, as described above, the OVP control unit 23 may execute processing to determine whether the cause is a short-circuit failure of the high-side switch 12 or another reason. The other reasons include a feedback loop abnormality such as (ii) an open failure of the first resistor 17, (iii) a break in the first feedback line 35, or (iv) a ground fault in the first feedback line 35. The OVP control unit 23 may be configured to transition to the temporary mode only when a short-circuit failure of the high-side switch 12 occurs. Alternatively, the OVP control unit 23 may be configured to transition to the temporary mode only when an abnormality in the feedback loop occurs.

[0155] The high-side switch 12 (= second FET 12) used for step-down control in the basic mode is preferably a high-performance switching element, i.e., an element with a high switching frequency, to eliminate switching loss. On the other hand, the first auxiliary switch, such as the first FET 11 or the first protection switch 51, which is switched in the emergency mode, may be a switching element with a lower switching frequency than the high-side switch 12. This is because in the emergency mode, it is sufficient to temporarily supply the minimum necessary amount of power. If the high-side switch 12 is an element capable of switching at 1 MHz or the like, the first auxiliary switch may be an element capable of switching at 200 kHz or 400 kHz. The switching frequency of the first auxiliary switch may be half or less of the switching frequency of the high-side switch 12.

[0156] If the switching frequency of the first auxiliary switch is half or less of the switching frequency of the high-side switch 12, the ripple of the output voltage during the emergency mode may increase compared to that during the basic mode. The ripple is the amplitude (fluctuation range) of the voltage relative to the target value. In one embodiment, the OVP control unit 23 may be configured to increase the maximum allowable ripple value during the emergency mode compared to that during the normal mode. This configuration allows a low-performance switching element to be used as the first FET 11 or the first protection switch 51 (i.e., the first auxiliary switch).

[0157] A basic allowable value, which is an allowable value for the ripple value for the second voltage, and a temporary allowable value, which is an allowable value for the ripple value for a temporary target voltage, may be registered in the OVP control unit 23. Control parameters such as the basic allowable value and the temporary allowable value may be stored in the storage unit 232 or a ROM (not shown). The OVP control unit 23 monitors the ripple value, which is the fluctuation range of the output voltage relative to the target value according to the operation mode.

[0158] When the basic mode is applied, the OVP control unit 23 stops the power supply to the load device 9 based on the ripple value exceeding the basic allowable value. Also, when the temporary mode is applied, the OVP control unit 23 may be configured to stop the power supply to the load device 9 based on the ripple value exceeding the temporary allowable value. The ripple value compared with the threshold value may be an instantaneous value (in other words, a raw observed value), or may be a moving average value, etc.

[0159] The power supply to the load device 9 may be stopped by keeping the first FET 11 off or by keeping the first protection switch 51 off. The power supply to the load device 9 may be stopped by turning off the switch 201. In such a configuration, the temporary tolerance may be set to a value greater than the basic tolerance. For example, the basic tolerance may be 0.6 V, and the temporary tolerance may be 1.12 V or 1.28 V. The basic tolerance and the temporary tolerance may be defined as percentages of the target voltage. For example, the basic tolerance may be 5%, and the temporary tolerance may be 8%. In this way, during temporary control, a larger ripple may be allowed compared to during normal operation.

[0160] The DCDC control unit 19 may be configured to sink the current flowing through the second FET 12 or the third FET 13 to reduce the output voltage when an overvoltage state is detected based on the first feedback voltage Va. However, to prevent overcurrent breakdown, an upper limit may be set on the amount of current that can be absorbed. Such a configuration may be effective for a short period of time when the second FET 12 has a certain resistance value and is short-circuited.

[0161] A coil or a resistive element may be interposed between the power supply line 30 and the first FET 11 / first protection switch 51. The first FET 11 / first protection switch 51 may be configured to receive a voltage slightly smaller than the first voltage. The first FET 11 / first protection switch 51 may be configured to receive a voltage corresponding to the first voltage and sufficiently larger than the second voltage.

[0162] The high-side switch 12 and the low-side switch 13 may be built into an IC that serves as the DCDC control unit 19. The power supply circuit 100 may include various elements other than those shown in the figure, such as a low-pass filter, a resistor, a Zener diode, etc. As one modified example, the DCDC conversion unit 101 may be configured as an LDO (Low Dropout) regulator.

[0163] The OVP control unit 23 and the DCDC control unit 19 may be connected by a signal line for data communication. In addition to the OVP control unit 23 and the DCDC control unit 19, the power supply circuit 100 may further include an arbitration unit configured to control the OVP control unit 23 and the DCDC control unit 19. The OVP control unit 23 may be realized using multiple ICs. The OVP control unit 23 may include an IC that controls the first auxiliary switch and an IC that controls the second auxiliary switch.

[0164] The functions of the OVP control unit 23 may be provided by the DCDC control unit 19. The functions of the DCDC control unit 19 may be provided by the OVP control unit 23. The OVP control unit 23 may be integrated with the DCDC control unit 19. In the above flowchart, the steps executed by the OVP control unit 23 may be executed by the DCDC control unit 19. The steps executed by the DCDC control unit 19 may be executed by the DCDC control unit 19. The functions of the load control unit 200 may be provided by the OVP control unit 23 or the DCDC control unit 19. The load setting data may be stored in the memory unit 232. The storage medium storing the load setting data corresponds to the load information memory unit. The functional layout in the zone ECU 1 may be changed as appropriate. The above functional layout is merely an example. The DCDC control unit 19, the OVP control unit 23, and the load control unit 200 may be simply replaced with a control unit. The zone ECU 1 / power supply circuit 100 includes hardware as at least one control unit.

[0165] The memory unit 232 may be provided in the DCDC control unit 19 or the load control unit 200. The location of the memory unit 232 may also be changed as appropriate. The various switching elements described above are not limited to FETs and may be various other switching elements. The ECU in which the power supply circuit 100 is implemented is not limited to the zone ECU 1 and may be various other ECUs. The present disclosure may be applied to in-vehicle devices other than ECUs. The present disclosure may be applied to devices other than in-vehicle devices. The power source does not have to be an in-vehicle power source.

[0166] The DCDC conversion unit 101 does not necessarily have to be compatible with synchronous rectification. The low-side switch 13 may be replaced with a diode. The anode of the diode implemented in place of the low-side switch 13 may be connected to ground, and the cathode may be electrically connected to the source of the high-side switch 12. Although power efficiency will be reduced, the DCDC conversion unit 101 may also be implemented as a step-down circuit using asynchronous rectification. In this case, transmission and reception of a synchronization signal will be unnecessary.

[0167] Furthermore, the DCDC conversion unit 101 may include both an FET and a diode as the low-side element. When the low-side element is a GaNFET, a regenerative diode may be connected in parallel to the GaNFET.

[0168] <Supplementary Remarks (1)> This specification discloses the following technical ideas and their combinations. This specification also includes methods, programs, etc. corresponding to the following technical ideas.

[0169] [Technical Idea 1] A power supply device for stepping down a first voltage corresponding to a voltage of a power supply of a vehicle and supplying the first voltage to at least one load device, the power supply device comprising: a load connection terminal (20) that is a terminal electrically connected to the at least one load device; a DCDC conversion unit (101) that is a circuit for generating a second voltage lower than the first voltage based on the first voltage; an auxiliary switch (11) that is a switching element attached to the DCDC conversion unit; and an auxiliary switch control unit (23) that controls on / off of the auxiliary switch, the DCDC conversion unit comprising: a high-side switch (12) that is a switching element that is on / off controlled so that an output voltage becomes the second voltage, and that is connected to a power supply line to which the first voltage is applied; a low-side element (13) that is a switching element or a diode connected in series with the high-side switch downstream of the high-side switch; and a DCDC control unit (19) that controls on / off of the high-side switch so that a voltage applied to the load connection terminal becomes the second voltage, the auxiliary switch being disposed between the low-side element and the power supply, The power supply device is configured to monitor the output voltage of the DCDC conversion unit while the auxiliary switch is set to either on or off so that current flows through the high-side switch, and when the output voltage of the DCDC conversion unit exceeds a predetermined threshold, initiate temporary control to dynamically switch the auxiliary switch on and off so that the voltage applied to the load connection terminal becomes a predetermined temporary target voltage.

[0170] [Technical Idea 2] The power supply device according to Technical Idea 1, wherein the auxiliary switch is arranged between the high-side switch and the power supply, and the auxiliary switch control unit is configured to keep the auxiliary switch set to on when the output voltage of the DCDC conversion unit does not exceed a predetermined value, and to start the temporary control when the output voltage of the DCDC conversion unit exceeds the threshold value.

[0171] [Technical Idea 3] The power supply device according to Technical Idea 2, wherein the auxiliary switch control unit is configured to turn off the auxiliary switch when the output voltage of the DCDC conversion unit exceeds a first threshold, which is the threshold, and to start the temporary control when the voltage of the load connection terminal falls below a second threshold that is smaller than the first threshold.

[0172] [Technical Idea 4] The power supply device according to Technical Idea 2, wherein the auxiliary switch control unit is configured to turn off the auxiliary switch when the output voltage of the DCDC conversion unit exceeds a first threshold value, which is the threshold value, and not to execute the emergency control if the voltage at the load connection terminal does not fall below a second threshold value that is smaller than the first threshold value even after a predetermined time has elapsed since the auxiliary switch was set to off.

[0173] [Technical Idea 5] The power supply device according to any one of Technical Ideas 2 to 4, further comprising a memory unit (232) that is a storage medium for storing data indicating the number of times a circuit abnormality has been detected, wherein the auxiliary switch control unit turns off the auxiliary switch when the output voltage of the DCDC conversion unit exceeds a first threshold that is the threshold, and increments the value of the number of detections stored in the memory unit if the voltage of the load connection terminal does not fall below a second threshold that is smaller than the first threshold even after a predetermined time has elapsed since the auxiliary switch was set to off, and the auxiliary switch control unit keeps the auxiliary switch off when the value of the number of detections stored in the memory unit is equal to or greater than a predetermined value.

[0174] [Technical Idea 6] The power supply device according to any one of Technical Ideas 2 to 5, wherein the auxiliary switch is a first auxiliary switch, and further comprises a second auxiliary switch (16) that is a switching element different from the first auxiliary switch and whose connection state is controlled by the auxiliary switch control unit, and the second auxiliary switch is connected in parallel with the high-side switch.

[0175] [Technical Idea 7] The power supply device according to Technical Idea 6, comprising, as operation modes, a basic mode in which the second voltage is generated using the high-side switch, and a temporary mode in which the temporary control is performed using the first auxiliary switch, wherein the auxiliary switch control unit is configured to: in the basic mode, set the first auxiliary switch to ON and the second auxiliary switch to OFF; and, when the output voltage exceeds the threshold value while the basic mode is applied, switch the second auxiliary switch ON and then start the temporary control.

[0176] [Technical Idea 8] The power supply device according to Technical Idea 1, further comprising a second auxiliary switch (16) that is a switching element different from the first auxiliary switch as the auxiliary switch and whose connection state is controlled by the auxiliary switch control unit, wherein the first auxiliary switch is arranged to connect the power supply and the low-side element, and the second auxiliary switch is arranged between the power supply and the high-side switch.

[0177] [Technical Idea 9] The power supply device according to Technical Idea 8, comprising, as operation modes, a basic mode in which the second voltage is generated using the high-side switch, and a temporary mode in which the temporary control is performed using the first auxiliary switch, wherein the auxiliary switch control unit is configured to: in the basic mode, set the first auxiliary switch to OFF and the second auxiliary switch to ON; and, when the output voltage exceeds the threshold value while the basic mode is applied, switch the second auxiliary switch to OFF and then start the temporary control using the first auxiliary switch.

[0178] [Technical Idea 10] The power supply device according to any one of Technical Ideas 1 to 9, wherein the low-side element is a switching element serving as a low-side switch, the DCDC conversion unit is configured as a DCDC converter of a synchronous rectification type, and the auxiliary switch control unit is configured, when executing the temporary control, to output a synchronization signal to the DCDC control unit for the DCDC control unit to specify the timing for switching on and off the low-side switch.

[0179] [Technical Idea 11] The at least one load device includes a plurality of load devices, and is equipped with a load management unit (200) that manages the plurality of load devices connected to the load connection terminal, and the load management unit has a load information storage unit in which data indicating priority loads that are load devices with high priority and normal loads that are load devices with low priority is registered, and when the auxiliary switch control unit executes the temporary control, the power supply device described in any one of Technical Ideas 1 to 10 is configured to maintain power supply to the priority loads while stopping power supply to the normal loads.

[0180] [Technical Idea 12] The power supply device according to any one of Technical Ideas 1 to 11, wherein the auxiliary switch control unit is configured to execute a process for notifying a user that an abnormality has occurred when the temporary control is executed.

[0181] [Technical Concept 13] The power supply device according to any one of Technical Concepts 1 to 12, wherein the temporary target voltage is set to a third voltage that is higher than the second voltage by a predetermined amount.

[0182] [Technical Idea 14] A power supply device according to any one of Technical Ideas 1 to 13, comprising, as operation modes, a basic mode in which the second voltage is generated using the high-side switch, and a temporary mode in which the temporary control is performed using the auxiliary switch, wherein the auxiliary switch control unit is configured to: monitor a ripple value which is a fluctuation range of the output voltage relative to a target value; and, when the basic mode is applied, stop the power supply to the load device based on the ripple value exceeding a predetermined basic allowable value; and, when the temporary mode is applied, stop the power supply to the load device based on the ripple value exceeding a predetermined temporary allowable value, wherein the temporary allowable value is set to a value greater than the basic allowable value.

[0183] The DCDC converter of Technical Concept 1 may include an inductor (14) provided between the load connection terminal and the high-side switch. The DCDC converter may also include a capacitor (15) provided between the output line connected to the load connection terminal and ground. The power source is not limited to the vehicle power source, and may be another power source.

[0184] <Supplementary Remark (2)> In the present disclosure, the upstream terminal of a circuit element refers to the terminal of multiple terminals included in the circuit element that is closer to the power supply 8. Furthermore, the downstream terminal refers to the terminal of multiple terminals included in the circuit element that is farther from the power supply 8. In an N-channel FET, the upstream terminal is the drain, and the downstream terminal is the source. In a P-channel FET, the upstream terminal may be interpreted as the source, and the downstream terminal as the drain. The term "attached" means being provided around a certain circuit to assist / control the operation of the circuit. A switching element (i.e., an auxiliary switch) attached to a DCDC conversion unit, or a switch installed in the DCDC conversion unit, may be interpreted as a switch provided in a current path related to the DCDC conversion unit to control the current input to the DCDC conversion unit.

[0185] The various flowcharts shown in this disclosure are merely examples, and the number of steps constituting the flowcharts and the order of execution of the processes can be changed as appropriate. The controls shown in each flowchart may be combined / executed in parallel to the extent that there is no contradiction. Expressions such as acquisition, determination, detection, generation, and calculation may be used interchangeably. When a device acquires certain data, it also includes the device generating the data based on a signal input from another device / sensor.

[0186] The apparatus, system, and methods described herein may be implemented by a special-purpose computer comprising a processor programmed to perform one or more functions embodied in a computer program. The apparatus and methods described herein may also be implemented using special-purpose hardware logic circuitry. The apparatus and methods described herein may also be implemented by one or more special-purpose computers configured by a combination of a processor executing a computer program and one or more hardware logic circuits. The processor may be any computing core, such as a CPU, MPU, GPU, or DFP (Data Flow Processor). Some or all of the functionality of the power supply circuit 100 may be implemented using a system-on-chip (SoC), an integrated circuit (IC), or a field-programmable gate array (FPGA). The computer program includes instructions for execution by a computer. The computer program may be stored on a computer-readable, non-transitory, tangible storage medium. The computer program recording medium may be a variety of media such as a hard-disk drive (HDD), a solid-state drive (SSD), or a flash memory.

Claims

1. A power supply device for stepping down a first voltage corresponding to the voltage of a vehicle power supply and supplying the first voltage to at least one load device, comprising: a load connection terminal (20) that is a terminal electrically connected to the at least one load device; a DCDC conversion unit (101) that is a circuit for generating a second voltage lower than the first voltage based on the first voltage; an auxiliary switch (11) that is a switching element attached to the DCDC conversion unit; and an auxiliary switch control unit (23) that controls the on / off of the auxiliary switch, wherein the DCDC conversion unit comprises: a high-side switch (12) that is a switching element that is on / off controlled so that the output voltage becomes the second voltage, and is connected to a power supply line to which the first voltage is applied; a low-side element (13) that is a switching element or diode connected in series with the high-side switch downstream of the high-side switch; and a DCDC control unit (19) that controls the on / off of the high-side switch so that the voltage applied to the load connection terminal becomes the second voltage, wherein the auxiliary switch is disposed between the low-side element and the power supply, The power supply device is configured to monitor the output voltage of the DCDC conversion unit while the auxiliary switch is set to either on or off so that current flows through the high-side switch, and when the output voltage of the DCDC conversion unit exceeds a predetermined threshold, initiate temporary control to dynamically switch the auxiliary switch on and off so that the voltage applied to the load connection terminal becomes a predetermined temporary target voltage.

2. The power supply device of claim 1, wherein the auxiliary switch is disposed between the high-side switch and the power supply, and the auxiliary switch control unit is configured to keep the auxiliary switch set to on when the output voltage of the DCDC conversion unit does not exceed a predetermined value, and to start the temporary control when the output voltage of the DCDC conversion unit exceeds the threshold value.

3. The power supply device of claim 2, wherein the auxiliary switch control unit is configured to turn off the auxiliary switch when the output voltage of the DC-DC conversion unit exceeds a first threshold value, which is the threshold value, and to start the temporary control when the voltage at the load connection terminal falls below a second threshold value that is smaller than the first threshold value.

4. The power supply device of claim 2, wherein the auxiliary switch control unit is configured to turn off the auxiliary switch when the output voltage of the DCDC conversion unit exceeds a first threshold value, which is the threshold value, and not to execute the temporary control if the voltage at the load connection terminal does not fall below a second threshold value that is smaller than the first threshold value even after a predetermined time has elapsed since the auxiliary switch was set to off.

5. A power supply device as described in claim 2, further comprising a memory unit (232) which is a storage medium in which data indicating the number of times a circuit abnormality has been detected is stored, wherein the auxiliary switch control unit turns off the auxiliary switch when the output voltage of the DCDC conversion unit exceeds a first threshold which is the threshold, and increments the value of the number of detections stored in the memory unit if the voltage of the load connection terminal does not fall below a second threshold which is smaller than the first threshold even after a predetermined time has elapsed since the auxiliary switch was set to off, and the auxiliary switch control unit keeps the auxiliary switch off if the value of the number of detections stored in the memory unit is equal to or greater than a predetermined value.

6. The power supply device according to claim 2, wherein the auxiliary switch is a first auxiliary switch, and further comprises a second auxiliary switch (16) which is a switching element different from the first auxiliary switch and whose connection state is controlled by the auxiliary switch control unit, and the second auxiliary switch is connected in parallel with the high-side switch.

7. A power supply device as described in claim 6, comprising, as operating modes, a basic mode in which the second voltage is generated using the high-side switch, and a temporary mode in which the temporary control is performed using the first auxiliary switch, wherein the auxiliary switch control unit is configured to: in the basic mode, set the first auxiliary switch to ON and the second auxiliary switch to OFF; and, when the output voltage exceeds the threshold value while the basic mode is applied, switch the second auxiliary switch ON and then start the temporary control.

8. The power supply device according to claim 1, further comprising a second auxiliary switch (16) that is a switching element different from the first auxiliary switch as the auxiliary switch, the connection state of which is controlled by the auxiliary switch control section, wherein the first auxiliary switch is arranged to connect the power supply and the low-side element, and the second auxiliary switch is arranged between the power supply and the high-side switch.

9. A power supply device as described in claim 8, comprising, as operating modes, a basic mode in which the second voltage is generated using the high-side switch, and a temporary mode in which the temporary control is performed using the first auxiliary switch, wherein the auxiliary switch control unit is configured to: in the basic mode, set the first auxiliary switch to OFF and the second auxiliary switch to ON; and, when the output voltage exceeds the threshold value while the basic mode is applied, switch the second auxiliary switch to OFF and then start the temporary control using the first auxiliary switch.

10. The power supply device of claim 1, wherein the low-side element is a switching element serving as a low-side switch, the DCDC conversion unit is configured as a DCDC converter of a synchronous rectification type, and the auxiliary switch control unit is configured, when executing the temporary control, to output a synchronization signal to the DCDC control unit for the DCDC control unit to specify the timing for switching the low-side switch on and off.

11. The power supply device according to claim 1, wherein the at least one load device includes a plurality of load devices, and the power supply device is provided with a load management unit (200) that manages the plurality of load devices connected to the load connection terminal, the load management unit having a load information storage unit in which data indicating priority loads that are load devices with high priority and normal loads that are load devices with low priority is registered, and when the auxiliary switch control unit executes the temporary control, the power supply device is configured to maintain power supply to the priority loads while stopping power supply to the normal loads.

12. The power supply device according to claim 1, wherein the auxiliary switch control unit is configured to execute processing to notify the user that an abnormality has occurred when executing the temporary control.

13. The power supply device according to claim 1, wherein the temporary target voltage is set to a third voltage that is higher than the second voltage by a predetermined amount.

14. A power supply device as described in claim 1, comprising as operating modes a basic mode in which the second voltage is generated using the high-side switch and a temporary mode in which the temporary control is performed using the auxiliary switch, wherein the auxiliary switch control unit is configured to monitor a ripple value, which is the fluctuation range of the output voltage relative to a target value, and when the basic mode is applied, stop the power supply to the load device based on the ripple value exceeding a predetermined basic allowable value, and when the temporary mode is applied, stop the power supply to the load device based on the ripple value exceeding a predetermined temporary allowable value, wherein the temporary allowable value is set to a value greater than the basic allowable value.

15. A power supply method implemented by at least one control unit (19, 23) provided in a power supply circuit including: a load connection terminal (20) that is a terminal electrically connected to at least one load device; a high-side switch (12) to which a first voltage corresponding to the voltage of a vehicle's power supply is input; a low-side element (13) that is a switching element or diode connected in series with the high-side switch downstream of the high-side switch; and an auxiliary switch (11) that is a switching element different from the high-side switch and is arranged between the low-side element and the power supply, wherein the at least one control unit: sets the auxiliary switch to either on or off so that a current flows through the high-side switch; generates a second voltage lower than the first voltage by switching the high-side switch while the auxiliary switch is set to a state in which a current flows through the high-side switch; and monitors whether the voltage generated by switching the high-side switch exceeds a predetermined threshold. and initiating temporary control of dynamically switching on and off the auxiliary switch in response to the voltage generated by switching the high-side switch exceeding the threshold value so that the voltage applied to the load connection terminal becomes a predetermined temporary target voltage.

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