Onboard power supply network

Abstract

An onboard power supply network according to the present invention is an onboard power supply network for supplying power to a load mounted on a vehicle via a plurality of nodes in the vehicle. The plurality of nodes include first nodes for transmitting power and second nodes for receiving power transmitted from the first nodes. The first and second nodes are interconnected by power lines through which power is supplied and signal lines by which information pertaining to power is transmitted and terminated at termination potentials via resistors. Each of the first and second nodes has a current measurement unit that measures the value of current flowing in and out of the node via a power line, a current input / output unit that inputs / outputs a current proportional to the current value between the signal line and the node, and a potential measurement unit that measures the potential of the signal line. The current input / output unit has a current limiting unit that limits the input / output current inputted to the current input / output unit or outputted from the current input / output unit, and when the potential of the signal line is different from a terminal potential, it is diagnosed that an abnormality has occurred somewhere in the onboard power supply network.

Description

Onboard power supply network

[0001] The present invention relates to a power supply network, and more particularly to an on-board power supply network suitable for electric vehicles.

[0002] Since the beginning of this century, there has been progress in the electrification of automobile auxiliary equipment such as electric power steering and electric brakes. In recent years, the electrification of main engines has also progressed, as exemplified by hybrid vehicles and electric bicycles. Furthermore, with the advancement of autonomous driving, automobiles will be required to operate autonomously and automatically without human intervention even in the event of a breakdown. Against this background, there is a growing demand for improved performance and reliability (continuous operation in the event of a breakdown) in the onboard power supply network that supports the electrification and automation of automobiles.

[0003] In order to ensure continued operation in the event of a fault in an on-board power supply network that has a daisy chain / ring topology configuration that passes through multiple stages of electronic control units (zone ECUs) located in the vehicle body, it is necessary to detect in which section (between which zone ECUs) the fault occurred and take measures to cut off or bypass the relevant section. Note that in this specification, "fault" refers to a "power short" in which wiring is shorted to a power source, and a "ground fault" in which wiring is shorted to ground potential (GND).

[0004] To identify a section where a fault has occurred, for example, Patent Document 1 discloses a differential current method that detects whether the sending current and the receiving current match on the power sending side and receiving side of that section. With this technology, when no fault has occurred in that section, the sending current and the receiving current match, but when a fault occurs, the sending current and the receiving current no longer match, making it possible to detect the occurrence of a fault.

[0005] Japanese Patent Application Laid-Open No. 2021-90257

[0006] However, in Patent Document 1, current is detected using a current transformer and abnormalities are determined using a relay, so the scope of application is limited to AC current, which is the mainstream in commercial power supplies, and it cannot be applied to DC current, which is the mainstream in current automotive power supply networks.

[0007] The present invention has been made in view of the above-mentioned problems, and has an object to provide an on-board power supply network that uses direct current and that is capable of quickly detecting the occurrence of a fault.

[0008] In order to achieve the above object, an on-board power supply network according to the present invention is an on-board power supply network that supplies power to a load mounted on a vehicle via a plurality of nodes within the vehicle, the plurality of nodes including a first node that transmits power and a second node that receives the power transmitted from the first node, the first and second nodes being connected by a power line through which power is supplied and a signal line through which information related to the power is transmitted and which is terminated at a termination potential via a resistor, each of the first and second nodes having a current measurement unit that measures the value of a current flowing in and out of the node via the power line, a current input / output unit that inputs and outputs a current proportional to the current value between the signal line and the node, and a potential measurement unit that measures the potential of the signal line, the current input / output unit having a current limiting unit that limits the input / output current input to or output from the current input / output unit, and if the potential of the signal line differs from the termination potential, it is diagnosed that an abnormality has occurred somewhere in the on-board power supply network.

[0009] According to the present invention, it is possible to quickly detect the occurrence of a fault in an on-board power supply network that uses direct current. Further features related to the present invention will become apparent from the description of this specification and the accompanying drawings. Furthermore, problems, configurations, and effects other than those described above will become apparent from the following description of the embodiments.

[0010] 1 is a diagram showing a basic configuration of an on-board power supply network according to a first embodiment of the present invention. FIG. 1 is a diagram showing an example of the time course of a diagnosis performed from when a fault occurs in an on-board power supply network until the location of the fault is identified. A graph showing the relationship between the type of fault that has occurred and the potential of a sense line. FIG. 2 is a diagram showing the configuration of an on-board power supply network according to a second embodiment of the present invention, in which a termination is a Thevenin termination. FIG. 3 is a diagram showing a configuration in which a Thevenin termination is built into ECU 200-1. FIG. 4 is a diagram showing a configuration in which a Thevenin termination is built into ECU 200-2. FIG. 5 is a diagram showing the configuration of an on-board power supply network according to a third embodiment of the present invention, in which network communications within the on-board power supply network are multiplexed. A graph showing a change in potential when a potential is transmitted using a recessive voltage of a CAN. FIG. 6 is a diagram showing an example of a configuration adopted when a potential is transmitted using a recessive voltage of a CAN. FIG. 7 is a diagram showing the configuration of an on-board power supply network according to a fourth embodiment of the present invention, in which a power line is branched and an ECU 200-3 is added. FIG. 8 is a diagram showing the configuration of an on-board power supply network according to a fifth embodiment of the present invention, in which the detailed configurations of a current measurement unit and a current input / output unit are shown. 19 is a diagram showing a configuration in which a current amplifier circuit is added to the configuration of FIG. 11 . FIG. 19 is a diagram showing a configuration of an on-board power supply network according to Reference Example 6, in which power is supplied redundantly. FIG. 20 is a diagram showing a modified example of the on-board power supply network according to Reference Example 6. FIG. 21 is a diagram showing another modified example of the on-board power supply network according to Reference Example 6. FIG. 22 is a diagram showing a configuration of an on-board power supply network according to Reference Example 7, which is applied to four ECUs mounted on an automobile. FIG. 23 is a table showing the relationship between the location of a failure and the opening and closing status of switches in the configuration of FIG. 16 . A modified example of the on-board power supply network according to Reference Example 7. FIG. 21 is a diagram showing the configuration of an on-board power supply network according to Reference Example 8, which is applied to four ECUs mounted on an automobile. FIG. 22 is a table showing the relationship between the location of a failure and the opening and closing status of switches in the configuration of FIG. 19 . FIG. 23 is a diagram showing a modified example of the on-board power supply network according to Reference Example 8. FIG. 24 is a diagram showing types of semiconductor switches. FIG. 25 is a diagram showing the basic configuration of an on-board power supply network according to Example 1 of the present invention. FIG. 26 is a graph showing the relationship between the type of failure that has occurred and the potential of the sense line, which is applied in Example 1. 1 is a diagram showing a basic configuration of an in-vehicle power supply network according to a second embodiment of the present invention, in which clamp diodes are added in parallel to Rsout and Rsin as a current limiting unit. 2 is a graph showing the relationship between Iout and Iin and Is1 and Is2 obtained by the second embodiment. 3 is a diagram showing a basic configuration of an in-vehicle power supply network according to a third embodiment, in which a current limiting resistor r is added in series to the output of a current input / output unit as a current limiting unit.1 is a graph showing the relationship between Vs1 and Vs2 and Is1 and Is2 obtained by Example 3. FIG. 1 shows a basic configuration of an on-board power supply network according to Example 4, in which a diode is added in series to the power supply ground of a current input / output unit as a current limiting unit. FIG. 2 is a graph showing the relationship between Vs1 and Vs2 and Is1 and Is2 obtained by Example 4. FIG. 3 is a graph showing the relationship between Vs1 and Vs2 and Is1 and Is2 obtained by Example 4. FIG. 4 shows a basic configuration of an on-board power supply network according to Example 5, in which the charging current and discharging current to a smoothing capacitor are used to test the abnormality detection function of the power line 20 provided by the present invention. FIG. 5 is a graph showing the time changes of Iout and Iin obtained by Example 5. FIG. 6 is a graph showing the relationship between the type of fault that has occurred and the potential of the sense line, as applied in Example 5. FIG. 7 is a diagram showing the basic configuration of an on-board power supply network according to Example 6, in which the ground potential that serves as the reference when measuring the potentials Vs1 and Vs2 of the sense line is the ground potential of the Thevenin termination. FIG. 8 is a diagram showing a configuration in which a Thevenin termination is built into ECU 200-1. FIG. 9 is a diagram showing a configuration in which a Thevenin termination is built into ECU 200-2. FIG. 10 is a diagram showing a basic configuration of an in-vehicle power supply network according to a seventh embodiment, in which a sense line and a line connected to the ground potential of the Thevenin termination are a twisted pair. FIG. 11 is a diagram showing a configuration in which a Thevenin termination is built into an ECU 200-1. FIG. 12 is a diagram showing a configuration in which a Thevenin termination is built into an ECU 200-2. FIG. 13 is a diagram showing a basic configuration of an in-vehicle power supply network according to an eighth embodiment, in which a sense line and a line connected to the ground potential of the Thevenin termination are shielded wires or coaxial cables. FIG. 14 is a diagram showing a configuration in which a Thevenin termination is built into an ECU 200-1. FIG. 15 is a diagram showing a configuration in which a Thevenin termination is built into an ECU 200-2.

[0011] An embodiment of the present invention will be described below with reference to the drawings.

[0012] [Reference Example 1] First, a reference example useful for understanding embodiments of the present invention will be described with reference to Figures 1 to 22. Figure 1 is a diagram showing the basic configuration of an on-board power supply network according to Reference Example 1 of the present invention. The on-board power supply network 1 according to Reference Example 1 supplies power from a power source (not shown) via multiple ECUs to a load (not shown) mounted on a vehicle. The on-board power supply network 1 includes an ECU 200-1 that outputs power and an ECU 200-2 that receives the power output from the ECU 200-1. The ECU 200-1 and the ECU 200-2 are connected by a power line 20 through which power is supplied and a sense line 21 through which information related to the power is transmitted.

[0013] ECU 200-1 includes a current measurement unit 201-1 that measures current Iout sent through power line 20, and a current input / output unit 202-1 that passes a current Is1=K×Iout proportional to the measured current Iout to sense line 21, where K is a predetermined proportionality constant. ECU 200-2 similarly includes a current measurement unit 203-2 that measures current Iin received through power line 20, and a current input unit 204-2 that receives a current Is2=K×Iin proportional to current Iin from sense line 21. Note that while FIG. 1 shows a configuration in which current flows from ECU 200-1 to ECU 200-2, a configuration in which current flows conversely from ECU 200-2 to ECU 200-1 is also possible. In this case, the current flowing through the sense line 21 is output from the current input unit 204-2 of the ECU 200-2 and input to the current input / output unit 202-1 of the ECU 200-1. Therefore, hereinafter, these will not be distinguished from each other and will be collectively referred to as the current input / output unit.

[0014] Furthermore, the sense line 21 is terminated at a potential VAG via a resistor R. Also connected to the power supply network 1 are a potential meter capable of measuring the potential at any position, a voltage source, an ECU, and a CPU (Central Processing Unit) for controlling the operation of the potential meter (none of which are shown).

[0015] Here, if the potential of the sense line 21 is Vs and the current flowing in via the resistor R is i, then i = (VAG - Vs) / R (1) From equation (1), Vs = VAG - R x i (2) According to Kirchhoff's law of current at point A, i + K x Iout - K x Iin = 0 (3) From equation (3), i = K x Iin - K x Iout (4) Substituting equation (4) into equation (2), we get Vs = VAG - R x K (Iin - Iout) (5)

[0016] From equation (5), it can be seen that the potential Vs of the sense line 21 contains information about the difference between the incoming current and the outgoing current (Iin-Iout), and when the two are equal, that is, when Iin=Iout, Vs=VAG.

[0017] The value of K is set so that the values ​​of Is1 and Is2 are in a range appropriate for information sharing with respect to the actual target Iin and Iout. For example, K=10 －３ Then, for Iin and Iout of several A, the values ​​of Is1 and Is2 are in the range of several mA, and K = 10 －４ In this case, the values ​​of Is1 and Is2 are in the range of several mA for Iin and Iout of several tens of A, and K = 10 －５ If this is the case, the values ​​of Is1 and Is2 will be in the range of a few mA for Iin and Iout of several hundred A, a range in which there will be no problem with noise caused by Is1 and Is2. The values ​​of VAG and R should be set so that the value of Vs is in a range that is convenient for measurement. For example, when measuring a circuit in which the positive power supply voltage Vcc of the entire circuit is 5V, it is best to set VAG = Vcc / 2 = approximately 2.5V.

[0018] In this case, VAG=Vcc / 2 (6) Substituting equation (6) into equation (5) gives Vs=(Vcc / 2)-R×K(Iin-Iout) (5)'.

[0019] In this case, R=10 ３ In this case, for a current difference (Iin-Iout) of several amperes, the voltage range is Vs=(Vcc / 2)±several volts.

[0020] As described above, when current flows from ECU 200-2 to ECU 200-1 in the opposite direction to the configuration in FIG. 1, the above operation is also established, except that the directions (signs) of Iout and Iin are reversed.

[0021] FIG. 2 is a diagram showing an example of the time course of a diagnosis performed from the occurrence of a fault in an on-board power supply network until the location of the fault is identified. Specifically, the diagram shows the flow of fault occurrence → fault detection → shutdown switching → network communication → fault location identification. First, in Phase 1, the occurrence of a fault is detected as an abnormality in the potentials Vs1 and Vs2 of the sense lines 21 connected to ECUs 200-1 and 200-2. Then, the power line 20 is shut off and switched to protect the power line 20 and the circuits in ECUs 200-1 and 200-2 from heat generation, breakdown, and fire due to overcurrent. Next, in Phase 2, the potentials Vs1 and Vs2 of the sense lines 21 measured by ECUs 200-1 and 200-2 are exchanged via network communication. By sharing the potentials Vs1 and Vs2 of the sense lines 21 detected by both ECUs in this way, the location of the fault can be identified in Phase 3, as described below.

[0022] 3 is a graph showing the relationship between the type of fault that has occurred and the potential of the sense line, used in the diagnosis to identify the fault location in Phase 3. The vertical axis represents the potential Vs1 of the sense line 21 measured by ECU 200-1, and the horizontal axis represents the potential Vs2 of the sense line 21 measured by ECU 200-2. When no fault has occurred in the on-board power supply network 1 and everything is normal, both Vs1 and Vs2 take values ​​that are approximately equal to VAG (=Vcc / 2).

[0023] In the case of a power line ground fault, the impedance of the entire system decreases, and the current flowing into the sense line 21 increases. Therefore, both Vs1 and Vs2 take values ​​in region (1) that are greater than Vcc / 2. Conversely, in the case of a power line ground fault, the impedance of the entire system increases, and the current flowing into the sense line 21 decreases. Therefore, both Vs1 and Vs2 take values ​​in region (2) that are smaller than Vcc / 2.

[0024] When the Vs1 detection circuit of ECU 200-1 fails, Vs2 is approximately equal to Vcc / 2 and Vs1 is a value different from Vcc / 2 in region (3).When the Vs2 detection circuit of ECU 200-2 fails, Vs1 is approximately equal to Vcc / 2 and Vs2 is a value different from Vcc / 2 in region (4).

[0025] If the sense line is broken at a position closer to ECU 200-1 than the position where potential VAG is connected to sense line 21, for example, at point B in Figure 1, Vs1 will swing out to Vcc due to Is1 because it is not terminated by resistor R, and Vs2 will be 0 V when current input / output unit 204-2 is driven by a single power supply (Vcc to 0 V) ​​because it is terminated by resistor R, and will be -Is2 x R in proportion to Is2 when it is driven by both power supplies (Vcc to -Vcc) (area (5)). If the sense line is broken at a position closer to ECU 200-2 than the position where potential VAG is connected to sense line 21, for example, at point C in Figure 1, Vs1 is terminated by resistor R and therefore becomes a value Is1 x R proportional to Is1, and Vs2 is not terminated by resistor R and therefore becomes 0 V when current input / output unit 204-2 is driven by a single power supply (Vcc to 0 V) ​​and becomes -Vcc when driven by both power supplies (Vcc to -Vcc) (region (6)).

[0026] Using the principle described above, simply by measuring the potential of the sense line 21 connected between ECU 200-1 and ECU 200-2, it is possible to quickly identify the location of a fault that has occurred in the on-board power supply network 1 that uses direct current, and to cut off the circuitry that bypasses the faulty location, thereby protecting the entire system.

[0027] 4 is a diagram showing the configuration of an on-board power supply network 1 according to Reference Example 2. The on-board power supply network 1 according to Reference Example 2 differs from the on-board power supply network 1 according to Reference Example 1 in that the sense line 21 is terminated using a Thevenin termination. In this reference example, the sense line 21 is terminated at a ground potential GND and a positive power supply voltage Vcc with a resistor 2R, respectively, which is equivalent to a circuit terminated at a potential Vcc / 2 with a resistor R according to Thevenin's theorem. According to this reference example, there is no need to provide a power supply (voltage source) for the termination potential VAG=Vcc / 2 separately from the positive power supply voltage Vcc, as in Reference Example 1, and therefore the circuit configuration can be simplified.

[0028] In Fig. 4, the Thevenin resistor is provided on the sense line 21 between ECU 200-1 and ECU 200-2, but the terminal unit may be built into either ECU 200-1 or ECU 200-2 as shown in Fig. 5 and Fig. 6. Fig. 5 shows a reference example in which the terminal unit is built into ECU 200-1, and Fig. 6 shows a reference example in which the terminal unit is built into ECU 200-2.

[0029] 7 is a diagram showing the configuration of an in-vehicle power supply network 1 according to a third embodiment, in which internal network communications are multiplexed. In the in-vehicle power supply network 1 according to this embodiment, network transceivers 206-1 and 206-2 are built into the ECUs 200-1 and 200-2, respectively. These network transceivers 206-1 and 206-2 can be used as communication lines for sharing Vs1 and Vs2 between the ECUs 200-1 and 200-2 in Phase 2, as described in FIG. 2.

[0030] The following methods can be used for bidirectional communication to share Vs1 and Vs2: ■ Baseband transmission: TDMA (Time Division Multiple Access) ■ Modulated wave transmission: TDMA (Time Division Multiple Access) FDMA (Frequency Division Multiple Access) CDMA (Code Division Multiple Access)

[0031] 8 and 9 are diagrams showing the potential change and configuration when a CAN (Control Area Network) is used for network communication using network transceivers 206-1 and 206-2 and sense line 21, and potential Vs is transmitted as a voltage during recessive mode. The voltage during recessive mode of a CAN is normally about 2.5 V, but by setting the voltage during recessive mode to Vs, ECUs 200-1 and 200-2 connected to sense line 21 can share Vs as Vs1 and Vs2.

[0032] 9, during Dominant mode, the transistors connected to Vcc for the CANH terminals of CAN transceivers 206-1 and 206-2 are ON, and the transistors connected to GND for the CANL terminals are ON. During Recessive mode, the transistors connected to Vcc for the CANH terminals of CAN transceivers 206-1 and 206-2 are OFF, and the transistors connected to GND for the CANL terminals are OFF, and the voltage is normally around 2.5 V. However, the potential becomes Vs according to equation (5)' due to current Is1 from current input / output unit 202-1, current Is2 from current input / output unit 204-2, and the termination resistor.

[0033] In this case, as shown in FIG. 8, the differential voltage is less than 0.5 V in the Recessive state and exceeds 0.9 V in the Dominant state, so Vs can be transmitted without affecting the CAN communication itself.

[0034] According to this reference example, detection → cutoff switching in Phase 1 of FIG. 2 is performed based on the voltage Vs in the Recessive state in each of ECU 200-1 and ECU 200-2, and the CAN can be used for network communication in Phase 2 and for identifying the fault location in Phase 3.

[0035] 10 is a diagram showing the configuration of an in-vehicle power supply network according to a fourth embodiment, in which the power line 20 is branched to add an ECU 200-3. Kirchhoff's law for the current flowing in and out of ECUs 200-1, 200-2, and 200-3 via the sense line 21, which has the same topology as the power line 20, is similarly true for the current flowing in and out of ECUs 200-1, 200-2, and 200-3 via the power line 20. Therefore, the operation shown in the first embodiment also applies to a branched system, as in this embodiment. While this embodiment shows a case in which the power line 20 branches into two lines, the operation shown in the first embodiment also applies to any number of branches, because Kirchhoff's law for the current flowing in and out of multiple ECUs via the sense line 21, which has the same topology as the power line 20, is similarly true for the current flowing in and out of multiple ECUs via the power line 20.

[0036] Reference Example 5 FIG. 11 is a diagram showing the configuration of an in-vehicle power supply network according to Reference Example 5, showing the detailed configuration of current measurement units 201-1 and 203-2 and current input / output units 202-1 and 204-2.

[0037] In the current measurement unit 201-1 and the current input / output unit 202-1, the current Iout output from the ECU 200-1 is measured by a shunt resistor Rsout. At this time, the voltage difference across the shunt resistor Rsout is Iout×Rsout. The voltages across the shunt resistor Rsout are connected to the + input terminal and - input terminal of the operational amplifier OA via input resistor Ri, respectively. The output of the operational amplifier OA is output to the sense line 21 via another shunt resistor Rso. Here, the shunt resistor Rso is provided to measure the output current from the operational amplifier OA, and the voltage difference across the shunt resistor Rso is Is1×Rso. The voltages across the shunt resistor Rso are connected to the + input terminal and - input terminal of the operational amplifier OA via feedback resistor Rf, respectively. Here, considering the potential difference [(Vin+)-(Vin-)] between the + input terminal and the - input terminal of the operational amplifier OA, the following is obtained: (Vin+)-(Vin-)=(Rf×Iout×Rsout-Ri×Is1×Rso) / (Rf+Ri) (7)

[0038] Here, the gain of the operational amplifier OA is ideally infinite, so it operates to output a voltage from the output terminal so that (Vin+) - (Vin-) → 0. Therefore, if we set the left side of equation (7) to 0, we get Is1 = Rf x Iout x Rsout / Ri x Rso (8) K = Is1 / Iout = Rf x Rsout / (Ri x Rso) (9).

[0039] Similarly, for the current measurement unit 203-2 and the current input / output unit 204-2 on the ECU 200-2 side, the following equation is obtained: K=Is2 / Iin=Rf×Rsin / (Ri×Rso) (10)

[0040] 12 is a reference example in which a current amplifier circuit is added to the rear stage of the operational amplifier OA in addition to the configuration shown in Fig. 11. The output current of the operational amplifier OA is normally about 25 mA, but by adding a current amplifier circuit, it is possible to output a current exceeding this to the sense line 21. Even in this case, the output currents Is1 and Is2 are measured by the shunt resistor Rso and fed back to the operational amplifier OA, so that the operation is as shown in equations (7) to (10).

[0041] [Example 6] Figure 13 shows an example of ECUs 200-1 and 200-2 for implementing the present invention. ECU 200-1 is connected to another ECU 200-2 via power line 20 via switches SW1 and SW2, and further connected to load 40-1 via switch SW11. It is also connected to control function 210-2 of the other ECU 200-2 via switch SW12. Control function 210-1 controls switches SW1, SW2, SW11, and SW12 based on potentials Vs1 and Vs2 of the sense lines. Power is supplied to control function 210-1 from the connection point of switches SW1 and SW2 and from an external power source via a diode OR (DOR). With this power supply configuration, even if switches SW1 and SW2 are shut off in the event of a failure, power is still supplied from the external power source, allowing control of switches SW1, SW2, SW11, and SW12 to continue.

[0042] Similarly, ECU 200-2 is connected to other ECUs via switches SW3 and SW4 via power line 20, and is further connected to loads 40-3 and 40-4 via switches SW21 and SW22. Control function 210-2 controls switches SW3, SW4, SW21, and SW22 based on potentials Vs1 and Vs2 of the sense lines. Power is supplied to control function 210-2 from the connection point of switches SW3 and SW4 and from the external power supply (ECU 200-1) via a diode OR (DOR). With the above-described power supply configuration, even if switches SW3 and SW4 are shut off in the event of a failure, power is supplied from the external power supply (ECU 200-1), allowing control of switches SW3, SW4, SW21, and SW22 to continue.

[0043] 14 shows a reference example in which power is supplied to control function 210-2 in ECU 200-2 from power line 20-12 connected to ECU 200-1 via a diode OR (DOR) and from power line 20-23 connected to another power source. With the power supply configuration described above, even if switches SW3 and SW4 are shut off in the event of a failure, power is supplied from power line 20-12 or power line 20-23, so that control of switches SW3, SW4, SW21, and SW22 can continue.

[0044] 15 shows a reference example in which power is supplied to control function 210-2 in ECU 200-2 from the connection point of switches SW3 and SW4 and from an external power supply (ECU 200-3) via a diode OR (DOR). With the power supply configuration described above, even if switches SW3 and SW4 are shut off in the event of a malfunction, power is supplied from an external power supply (ECU 200-3) that is separate from ECU 200-1, which receives power via SW3, so that control of switches SW3, SW4, SW21, and SW22 can continue.

[0045] 16 to 22 show reference examples in which the above-described power supply network is mounted on a vehicle. Fig. 16 shows a reference example in which power is supplied from power source 100-1 to ECU 200-1, power is supplied from power source 100-2 to ECU 200-3, ECU 200-1 and ECU 200-3 are connected via power line 20-13, power is further supplied from ECU 200-1 to ECU 200-2 via power line 20-12, and power is further supplied from ECU 200-3 to ECU 200-4 via power line 20-34. Note that, to simplify the explanation, only components that require particular explanation will be denoted by reference numerals.

[0046] Power is supplied to ECU 200-1 from power source 100-1 via switch SW1, power is supplied to ECU 200-2 via switch SW2 and power line 20-12, and connected to ECU 200-3 via SW9 and power line 20-13. Power is supplied to ECU 200-2 from ECU 200-1 via switch SW3.

[0047] Power is supplied to ECU 200-3 from power source 100-2 via switch SW5, and power is supplied to ECU 200-4 via SW5 and power line 20-34, and connected to ECU 200-1 via switch SW10 and power line 20-13. Power is supplied to ECU 200-4 from ECU 200-3 via switch SW7.

[0048] The power lines 20-12, 20-13, and 20-34 are each provided with a sense line (not shown) which is a signal line for sharing current information, and a fault in the power lines 20-12, 20-13, and 20-34 is detected by the method provided by the present invention.

[0049] Power source 100-1 is a DC / DC converter connected to a main engine drive battery and main engine (motor / generator) (not shown). If the vehicle is a hybrid vehicle, the main engine is mechanically connected to the engine, and if the vehicle is an electric vehicle, the main engine drive battery is connected to a charger or a connection terminal for the charger. Under normal circumstances, regenerative power from the main engine drive battery or main engine (motor / generator) is converted into an auxiliary equipment drive voltage by the DC / DC converter of power source 100-1 and supplied to ECU 200-1.

[0050] The power source 100-2 is a battery for driving auxiliary equipment, and is normally charged in a floating state by the output of the power source 100-1 via the ECU 200-1 and the ECU 200-3.

[0051] The operation of each switch in this reference example is shown in Figure 17. Case 0 is a case where there is no fault (normal), and all switches are ON and power is supplied to all loads. Power is supplied to the steering ECU 200-5 and the automatic driving ECU 200-6 via diode OR, and power is also supplied to the electric brake ECUs (BK ECUs) 200-7 to 200-10 via each switch.

[0052] Note that the "normal" state in which there is no fault here does not simply mean that there is no fault in power line 20 and it is normal, but also includes a case in which the elements that constitute the function of detecting an abnormality in power line 20, such as sense line 21, node (electronic control unit: ECU) 200, current measurement units 201 and 203, and current input / output units 202 and 204, are also normal. This is because if an abnormality in power line 20 cannot be detected due to an abnormality in an element that constitutes the function of detecting an abnormality in power line 20, each switch will be operated based on erroneous information, and normal operation as a whole cannot be expected.

[0053] Therefore, in this reference example, by comparing the potential of the sense line 21 detected by the ECUs at both ends, it is possible to detect breaks in the sense line 21, power faults, and ground faults, as well as failures in the elements that make up the function of detecting abnormalities in the power line 20.

[0054] Case 1 shows a case where a fault occurs in power line 20-12. The fault is detected by the principle of the present invention described with reference to Figures 1 to 3, and switches SW2 and SW3 are turned OFF to disconnect power line 20-12. At this time, the power supply to ECU 200-2 is cut off, and the power supply to load 40-21 is also cut off.

[0055] Case 2 is when a fault occurs in power line 20-13. The fault is detected according to the principles of the present invention, and switches SW9 and SW10 are turned OFF, disconnecting power line 20-13. At this time, the battery, which is power source 100-2, is cut off from power source 100-1 and is no longer floating charged.

[0056] Case 3 shows a case where a fault occurs in the power line 20-34. The fault is detected according to the principles of the present invention, and the switches SW6 and SW7 are turned OFF, disconnecting the power line 20-34. At this time, the power supply to the ECU 200-4 is cut off, as well as the power supplies to the loads 40-41 and the rear wheel electric brake ECUs (BK ECUs) 200-8 and 200-10. By connecting the battery, which is the power source 100-2, to the ECU 200-4 as shown in FIG. 18, power supply to the ECU 200-4, the loads 40-41, and the rear wheel electric brake ECUs (BK ECUs) 200-8 and 200-10 continues even if a fault occurs in the power line 20-34. Because important loads are typically concentrated in the front of the vehicle, it is preferable to connect the battery, which is the power source 100-2, to the ECU 200-3 as shown in FIG. 16.

[0057] Case 4 is when a failure occurs in power source 100-1. The failure is detected by monitoring the output of power source 100-1 or by the self-diagnosis function of power source 100-1, and switch SW1 is turned OFF to disconnect power source 100-1. At this time, power is supplied to the entire in-vehicle power supply network by the output of power source 100-2, which has been floating-charged.

[0058] Case 5 is a case where a failure occurs in power source 100-2. The failure is detected by monitoring the output of power source 100-2 or by the self-diagnosis function of power source 100-2, and switch SW5 is turned OFF to disconnect power source 100-2. At this time, power is supplied to the entire in-vehicle power supply network by the output of power source 100-1.

[0059] [Reference Example 8] Figure 19 shows a reference example in which ECU 200-2 and ECU 200-4 are further connected by power line 20-24 via switches SW4 and SW8 in addition to the configuration in Figure 16. An example of the operation of switch SW in this reference example is shown in Figure 20. Note that Figure 20 adds control of switches SW4 and SW8 provided at both ends of power line 20-24 to the operation example shown in Figure 17.

[0060] When there is no fault (when the system is normal), there is no need for all switches to be turned OFF and power is supplied to all loads, but even in this case, two options exist: Case 0A and Case 0B. As shown in Case 0A, when switches SW9 and SW10 are turned ON and ECU 200-1 and ECU 200-3 are connected via power line 20-13, SW4 and SW8 connected to power line 20-24 connecting ECU 200-2 and ECU 200-4 may be turned ON or OFF. Also, as shown in Case 0B, when switches SW4 and SW8 are turned ON and ECU 200-2 and ECU 200-4 are connected via power line 20-24, SW9 and SW10 connected to power line 20-13 connecting ECU 200-1 and ECU 200-3 may be turned ON or OFF. In the table, "*" indicates "don't care," ie, it does not matter whether it is ON or OFF.

[0061] Cases 1 to 3 are the same as the cases shown in FIG. 17, and therefore the description thereof will be omitted.

[0062] If a failure occurs in power source 100-1, there are two options: Case 4A and Case 4B. When switches SW9 and SW10 are turned ON to connect ECU 200-1 and ECU 200-3 via power line 20-13 as in Case 4A, SW4 and SW8 connected to power line 20-24 connecting ECU 200-2 and ECU 200-4 may be turned ON or OFF. Also, when switches SW4 and SW8 are turned ON to connect ECU 200-2 and ECU 200-4 via power line 20-24 as in Case 4B, SW9 and SW10 connected to power line 20-13 connecting ECU 200-1 and ECU 200-3 may be turned ON or OFF. At this time, power is supplied to the entire in-vehicle power supply network by the output of power source 100-2.

[0063] Similarly, if a failure occurs in power source 100-2, there are two options, Case 5A and Case 5B. When switches SW9 and SW10 are turned ON to connect ECU 200-1 and ECU 200-3 via power line 20-13 as in Case 5A, SW4 and SW8 connected to power line 20-24 connecting ECU 200-2 and ECU 200-4 may be turned ON or OFF. Also, when switches SW4 and SW8 are turned ON to connect ECU 200-2 and ECU 200-4 via power line 20-24 as in Case 5B, SW9 and SW10 connected to power line 20-13 connecting ECU 200-1 and ECU 200-3 may be turned ON or OFF. At this time, power is supplied to the entire in-vehicle power supply network by the output of power source 100-1.

[0064] Case 6 is a case where a fault occurs in the power line 20-24. The fault is detected according to the principles of the present invention, and the switches SW4 and SW8 are turned OFF, disconnecting the power line 20-24. Power is supplied to the ECUs 200-2 and 200-4 via the power lines 20-12 and 20-34, respectively.

[0065] As described above, by connecting ECU 200-2 and ECU 200-4 via power line 20-24 via switches SW4 and SW8, it is possible to continue supplying power to the load even if a failure occurs in power line 20-12, power line 20-13, or power line 20-34.Therefore, it is also possible to omit the diode OR for supplying power from power source 100-2 to steering ECU 200-5 and automatic driving ECU 200-6, as shown in Figure 21.

[0066] In [Reference Example 7], current flows bidirectionally only in the wiring to power source 100-2 and in power line 20-13. Therefore, if switches SW5, SW9, and SW10 are implemented as semiconductor switches, it is necessary to connect elements with opposite polarity as shown in FIG. 22(b) so that bidirectional current can be controlled. Current flows unidirectionally in the other power lines 20-12 and 20-34. Therefore, the other SWs can be implemented as elements with a single polarity as shown in FIG. 22(a). Furthermore, in [Reference Example 8], current flows bidirectionally in the wiring to power source 100-2 and all power lines 20-12, 20-13, 20-34, and 20-24. Therefore, if switches SW2 to SW10 are implemented as semiconductor switches, it is necessary to connect elements with opposite polarity as shown in FIG. 22(b) so that bidirectional current can be controlled.

[0067] According to the above-described reference example, it is possible to quickly detect ground faults and shorts to power in the power line 20, failures in the ECU's potential detection circuit, and failures related to disconnection of the sense line 21. However, it is difficult to accurately detect failures related to ground faults and shorts to power in the sense line 21. This is because when the sense line 21 has a ground fault, the current flowing through the sense line 21 flows to ground, resulting in a significant decrease in the current flowing through the sense line 21. When the sense line 21 has a ground fault, the current flowing through the sense line 21 is significantly reduced. When the sense line 21 has a power short, this indicates that the sense line 21 has come into contact with a power source, resulting in a significantly large current flow. On the other hand, as described with reference to FIG. 3 , the current flowing through the sense line 21 also increases or decreases when the power line 20 has a ground or power short. Therefore, when the current flowing through the sense line 21 increases or decreases due to an increase or decrease in the potentials of both ECUs 2001 and 200-2, as in the regions (1) and (2) of FIG. 3 , it may be difficult to determine whether this is a ground or power short in the power line 20 or a ground or power short in the sense line 21.

[0068] The present inventors have found the above-mentioned problems in addition to those described in the reference example above, and have obtained the configurations according to the embodiments described below in order to solve the problems.

[0069] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the same components as those in the above-described reference example will be designated by the same reference numerals, and the description thereof will be omitted in some cases.

[0070] 23 is a diagram showing the basic configuration of an in-vehicle power supply network according to a first embodiment, in which current limiting units 220-1 and 220-2 are added to the current input / output units 202-1 and 204-2 in the reference example shown in FIG. In this embodiment, by providing the current limiting units 220-1 and 220-2 in the current input / output units 202-1 and 204-2, the input / output currents of the current input / output units 202-1 and 204-2 are limited to values ​​smaller than the current that flows when a power fault or ground fault occurs in the sense line 21. This makes it possible to clearly distinguish between the current that occurs when a power fault / ground fault occurs in the power line and the current that occurs when a power fault / ground fault occurs in the sense line 21.

[0071] 24 is a graph applied in this embodiment showing the relationship between the type of fault that has occurred and the potential of the sense line. As in FIG. 3, the vertical axis represents the potential Vs1 of the sense line 21 measured by ECU 200-1, and the horizontal axis represents the potential Vs2 of the sense line 21 measured by ECU 200-2. When no fault has occurred in the on-board power supply network 1 and everything is normal, both Vs1 and Vs2 take values ​​approximately equal to VAG (=Vcc / 2).

[0072] In the graph of Figure 24 showing the relationship between the type of fault that has occurred and the potential of the sense line, by limiting the output current range of current input / output units 202-1 and 204-2 according to this embodiment, it is possible to create a region of potential of sense line 21 that cannot be achieved with the limited output current of current input / output units 202-1 and 204-2 and that appears only when sense line 21 is in a ground or power short state without current limitation, as shown by regions (7) and (8) in Figure 24. Specifically, region (7) appears only when sense line 21 is in a ground short, and region (8) appears only when sense line 21 is in a power short. Therefore, when the potential of the sense line is in region (7), it represents a fault state in which the sense line is in a ground short, and region (8) represents a fault state in which sense line 21 is in a power short.

[0073] [Example 2] Figure 25 shows the configuration of an in-vehicle power supply network according to Example 2, in which clamp diodes are added in parallel to Rsout and Rsin as current limiting units 220-1 and 220-2 in the configuration of Figure 11. With this configuration, the clamp diodes function as current limiters, and the current output ranges Is1 and Is2 can be set so that the voltages across Rsout and Rsin are less than Vf, as shown in Figure 26. As shown by regions (7) and (8) in Figure 24, it is possible to create regions that cannot be achieved with the output currents of current input / output units 202-1 and 204-2. Specifically, when a current smaller than the current output ranges of Is1 and Is2 flows, this corresponds to region (7) in Figure 24, and it can be determined that the sense line has a ground fault. On the other hand, when a current larger than the current output ranges of Is1 and Is2 flows, this corresponds to region (8) in Figure 24, and it can be determined that the sense line has a power fault.

[0074] 27 is a diagram showing the configuration of an onboard power supply network according to a third embodiment, in which current limiting resistors r are added in series to the outputs of current input / output units 202-1 and 204-2 as current limiting units 220-1 and 220-2 in addition to the configuration of FIG. 11. This embodiment makes it possible to limit the current output in the upper right region (where Vs1, Vs2 and Is1, Is2 are all large, i.e., Is1<(Vcc-Vs1) / r) and the lower left region (where Vs1, Vs2 and Is1, Is2 are all small, i.e., Is1>-Vs1 / r) in the graph of Vs1, Vs2 versus Is1, Is2 shown in FIG. 28. When a current corresponding to the upper right region flows, it can be determined that the sense line has a power short, and when a current corresponding to the lower left region flows, it can be determined that the sense line has a ground short. In this way, also in this embodiment, it is possible to create regions that cannot be realized by the output currents of the current input / output units 202-1 and 204-2, as shown in regions (7) and (8) in FIG.

[0075] [Example 4] Figure 29 shows the configuration of an in-vehicle power supply network according to Example 4, in which diodes 220-1a, 220-1b, 220-2a, and 220-2b are added to the configuration of Figure 11 as current limiting units 220-1 and 220-2, connected in series to the power supply grounds of current input / output units 202-1 and 204-2. This example limits the current output in the rightmost (Vs1, Vs2 > Vcc - Vf) region and the leftmost (Vs1, Vs2 < Vf) region in the graph of Vs1, Vs2 versus Is1, Is2 shown in Figure 30. Therefore, if a current corresponding to the rightmost region flows, it can be determined that the sense line has a short circuit to the power supply, and if a current corresponding to the leftmost region flows, it can be determined that the sense line has a ground fault. Thus, this example also creates regions that cannot be achieved by the output current of current input / output units 202-1 and 204-2, as shown in regions (7) and (8) of Figure 24.

[0076] [Example 5] Figure 31 shows the configuration of an in-vehicle power supply network according to Example 5, in which a smoothing capacitor C is inserted in the power line 20 (at any location between Rsout and Rsin), and the charging current and discharging current to the smoothing capacitor C are used to test the power line 20 abnormality detection function itself provided by the present invention. According to the configuration of this example, at the moment when Zone ECU 1 is turned ON, as shown in Figure 32, a portion of Iout output from ECU 200-1 becomes the charging current (A) to smoothing capacitor C, so that Iout becomes larger than Iin by that amount. Subsequently, at the moment when Zone ECU 1 is turned OFF, the discharging current (B) from smoothing capacitor C is added to Iin, so that Iin becomes larger than Iout by that amount. As described above, the series of ON and OFF operations of Zone ECU 1 shown in Figure 32 causes the values ​​of Iout and Iin to temporarily differ. Therefore, in the graph of FIG. 33 showing the relationship between the type of fault that has occurred and the potential of the sense line, the change in the graph of the potential of the sense line 21 as shown in (A) and (B) allows confirmation that the power line 20 anomaly detection function provided by the present invention is normal, i.e., that the power line 20 is not broken and that the Vs1 and Vs2 detection functions are normal. Specifically, it is possible to confirm that no abnormality has occurred in which only the value Vcc / 2 can be read due to a failure of the potential (Vs1, Vs2) detection circuit caused by a break in the power line 20. Note that, although smoothing capacitor C is located within Zone ECU 2 in FIG. 31 , smoothing capacitor C may be located anywhere between Rsout and Rsin, either within Zone ECU 1 or outside the two ECUs.

[0077] [Example 6] Figure 34 is a diagram showing the configuration of an on-board power supply network according to Example 6, in which the ground potential used as the reference when measuring the potentials Vs1 and Vs2 of the sense lines in Figure 4 is the ground potential of the Thevenin termination. Therefore, in this example, a signal line connected to the ground potential of the Thevenin termination is connected to the point where the potentials Vs1 and Vs2 of the sense lines are measured, and the potentials Vs1 and Vs2 of the sense lines 21 are measured as a differential input between the ground potential of the Thevenin termination and the potential of the signal line on the node side of the point where the signal line is terminated with the Thevenin termination. Note that the current limiting units 220-1 and 220-2 are omitted from Figure 34 and subsequent figures.

[0078] According to this embodiment, even if there is a difference in ground potential between Zone ECU1 (200-1) and Zone ECU2 (200-2), the potentials Vs1 and Vs2 of the sense lines can be measured without being affected by the ground potential difference, enabling more accurate fault determination.

[0079] While Fig. 34 has been described with reference to a case where there is a Thevenin termination between Zone ECU1 (200-1) and Zone ECU2 (200-2), a Thevenin termination may be built into Zone ECU1 (200-1) as shown in Fig. 35, which is a modification of Fig. 34. In this case, the potential Vs1 of the sense line on the Zone ECU1 (200-1) side can be measured as a normal single-ended input, and the potential Vs2 of the sense line on the Zone ECU2 (200-2) side can be measured as a differential input between the ground potential of the Thevenin termination and the potential of the signal line on the node side of the position where the signal line is terminated with the Thevenin termination.

[0080] Also, similar to Fig. 35, a Thevenin termination can be built into Zone ECU2 (200-2) as shown in Fig. 36. In that case, the potential Vs2 of the sense line on the Zone ECU2 (200-2) side can be measured as a normal single-ended input, and the potential Vs1 of the sense line on the Zone ECU1 (200-1) side can be measured as a differential input between the ground potential of the Thevenin termination and the potential of the signal line on the node side of the position where the signal line is terminated with the Thevenin termination.

[0081] [Example 7] Figure 37 shows the configuration of an in-vehicle power supply network according to Example 7, in which the signal line connected to the sense line 21 and the ground potential of the Thevenin termination is a twisted pair. Here, a twisted pair refers to a wiring formed by twisting two wires together. In a twisted pair, the magnetic flux generated in adjacent twisted pairs is oriented in opposite directions, and the current generated by this magnetic flux is also oriented in opposite directions, making it less susceptible to external influences, i.e., reducing electromagnetic induction noise. As explained using Figure 34 and other figures, when the sense line 21 is grounded, only a very weak current flows, and therefore, noise due to electromagnetic induction may have a significant impact. However, by reducing noise due to electromagnetic induction according to this example, it is possible to reliably detect the weak current generated when the sense line 21 is grounded. Note that Figures 38 and 39, similar to Figures 35 and 36, show configurations in which the Thevenin termination is incorporated into Zone ECU1 (200-1) and Zone ECU2 (200-2), respectively.

[0082] [Embodiment 8] Fig. 40 is a diagram showing the configuration of an in-vehicle power supply network according to embodiment 8, in which the sense line 21 connected to the ground potential of the Thevenin termination is surrounded by a shield 22. The shield 22 functions as an electromagnetic induction barrier, and in this embodiment as well, it is possible to reduce electromagnetic induction noise as in embodiment 7. Note that Figs. 41 and 42 are diagrams showing configurations in which the Thevenin termination is built into Zone ECU1 (200-1) and Zone ECU2 (200-2), respectively, similar to Figs. 35 and 36.

[0083] The above-described embodiment of the present invention provides the following advantageous effects: (1) An on-board power supply network according to the present invention is an on-board power supply network that supplies power to a load mounted on a vehicle via a plurality of nodes in the vehicle, the plurality of nodes including a first node that transmits power and a second node that receives the power transmitted from the first node, the first and second nodes being connected by a power line through which power is supplied and a signal line through which information related to the power is transmitted and which is terminated at a termination potential via a resistor, each of the first and second nodes having a current measurement unit that measures a value of a current flowing in and out of the node via the power line, a current input / output unit that inputs and outputs a current proportional to the current value between the signal line and the node, and a potential measurement unit that measures the potential of the signal line, the current input / output unit having a current limiting unit that limits an input / output current input to or output from the current input / output unit, and when the potential of the signal line differs from the termination potential, it is diagnosed that an abnormality has occurred somewhere in the on-board power supply network.

[0084] By employing the above configuration, it becomes possible to quickly detect the occurrence of a fault in an on-board power supply network that uses direct current.

[0085] (2) The current measurement unit and the current input / output unit are composed of operational amplifiers. This makes it possible to reliably detect even weak currents output from the ECU by amplifying them.

[0086] (3) The current limiting unit limits the measurement range of the current measuring unit, making it possible to determine that a ground / power short has occurred in the sense line when a current corresponding to the limited range flows.

[0087] (4) The current limiting unit includes a voltage clamp circuit connected in parallel to the shunt resistor in the current measuring unit, a resistor inserted in series with the output of the current input / output unit, or a clamp circuit connected in series with the power supply and ground of the current input / output unit. Specifically, the current limiting unit is composed of these elements.

[0088] (5) The termination potential and resistance are configured using the Thévenin termination. This eliminates the need to provide a power supply for the termination potential separately from the positive power supply voltage, which is expected to reduce the size and cost of the entire system.

[0089] (6) The potential measurement unit of each of the first and second nodes measures the potential of the signal line on the node side relative to the point where the signal line is terminated with the termination potential, thereby enabling each node to determine where the fault occurs on the signal line.

[0090] (7) The first and second nodes exchange the measured potentials of the signal lines via the network, which allows each node to identify the cause of the failure by comparing the potential it measured with the received potential.

[0091] (8) If the potentials of the exchanged signal lines of the first and second nodes are different, it is diagnosed that one of the signal lines, the current measurement unit, and the current input / output unit is abnormal. By adopting the configuration of (5) above, it becomes possible to specifically perform such a diagnosis.

[0092] (9) The first and second nodes encode the measured potential of the signal line, superimpose the encoded potential on the signal line, and transmit the encoded potential. By employing the multiplexed network communication as shown in the third embodiment, such efficient information transmission can be achieved.

[0093] (10) The first and second node potential measuring units measure, as a differential input, the potential of the signal line on the node side of the terminal of the signal line, with the ground potential of the terminal potential as a reference. This allows the potential of the sense line to be measured without being affected by the ground potential difference, even if there is a difference in ground potential between the first node and the second node, enabling more accurate fault detection.

[0094] (11) The ground potential of the terminal potential and the signal line are connected by a twisted pair or a coaxial cable, which makes it possible to reduce electromagnetic induction noise generated in the signal line.

[0095] (12) A capacitor is connected to the power line, and a fault in the potential measurement unit is detected based on a change in the potential of the signal line due to a charging current to the capacitor when power transmission from one of the first and second nodes to the other of the first and second nodes begins, and a discharge current from the capacitor when power transmission from one of the first and second nodes to the other of the first and second nodes ends. By utilizing the change in current related to the discharging / charging of the capacitor, it is possible to confirm that the signal line abnormality detection function according to the present invention is functioning properly.

[0096] (13) The node is an electronic control unit, and the electronic control unit has a current measurement unit, a current input / output unit, a first switch that switches current to a power line connected to the electronic control unit, a second switch that switches current to a load connected to the electronic control unit, and a control circuit, and the control circuit controls the first and second switches. This makes it possible to immediately cut off a power line or a load current supply path that has been diagnosed as having a fault, and to quickly protect the power supply network.

[0097] It should be noted that the present invention is not limited to the above-described embodiments, and various modifications are possible. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to embodiments that include all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment. It is also possible to add the configuration of another embodiment to the configuration of one embodiment. It is also possible to delete part of the configuration of each embodiment, or to add or replace other configurations.

[0098] 20...power line, 21...sense line, 22...shield, 40...load, 100...power source, 200...node (electronic control unit: ECU), 201, 203...current measurement section, 202, 204...current input / output section, 210...control function (control circuit), 220...current limiting section

Claims

1. An on-board power supply network that supplies power to loads mounted on a vehicle via a plurality of nodes within the vehicle, the plurality of nodes including a first node that transmits power and a second node that receives the power transmitted from the first node, the first and second nodes being connected by a power line through which power is supplied and a signal line through which information related to the power is transmitted and which is terminated at a termination potential via a resistor, each of the first and second nodes having a current measurement unit that measures the value of a current flowing in and out of the node via the power line, a current input / output unit that inputs and outputs a current proportional to the current value between the signal line and the node, and a potential measurement unit that measures the potential of the signal line, the current input / output unit having a current limiting unit that limits the input / output current input to or output from the current input / output unit, and if the potential of the signal line differs from the termination potential, it is diagnosed that an abnormality has occurred somewhere in the on-board power supply network.

2. An in-vehicle power supply network according to claim 1, wherein the current measurement unit and the current input / output unit are configured by operational amplifiers.

3. An in-vehicle power supply network according to claim 1, wherein the current limiting unit sets a limit on the measurement range of the current measuring unit.

4. An in-vehicle power supply network according to claim 3, wherein the current limiting unit includes a voltage clamp circuit connected in parallel to a shunt resistor in the current measuring unit.

5. An in-vehicle power supply network according to claim 1, wherein the current limiting unit includes a resistor inserted in series with the output of the current input / output unit.

6. An in-vehicle power supply network according to claim 1, wherein the current limiting unit includes a clamp circuit connected in series to a power supply to the current input / output unit and to ground.

7. An in-vehicle power supply network according to claim 1, wherein the termination potential and the resistance are configured by a Thevenin termination.

8. An in-vehicle power supply network according to claim 1, wherein the potential measurement unit of each of the first and second nodes measures the potential of the signal line on the node side relative to the position where the signal line is terminated with the termination potential.

9. An in-vehicle power supply network according to claim 8, wherein the first and second nodes exchange the measured potentials of the signal lines with each other via a network.

10. An in-vehicle power supply network according to claim 9, wherein, if the potentials of the signal lines of the replaced first and second nodes are different, any of the signal lines, the current measurement unit, and the current input / output unit is diagnosed as abnormal.

11. An in-vehicle power supply network according to claim 8, wherein the first and second nodes encode the measured potential of the signal line and transmit the encoded potential superimposed on the signal line.

12. An in-vehicle power supply network according to claim 8, wherein the potential measurement units of the first and second nodes measure, as a differential input, the potential of the signal line on the node side of the node where the signal line is terminated with the termination potential, with the ground potential of the termination potential as a reference.

13. An in-vehicle power supply network according to claim 12, wherein the ground potential of the termination potential and the signal line are connected by a twisted pair or a coaxial cable.

14. An in-vehicle power supply network according to claim 1, wherein a capacitor is connected to the power line, and a failure in the potential measurement unit is detected based on a change in the potential of the signal line due to a charging current to the capacitor at the start of power transmission from one of the first and second nodes to the other of the first and second nodes, and a discharge current from the capacitor at the end of power transmission from one of the first and second nodes to the other of the first and second nodes.

15. An in-vehicle power supply network according to claim 1, wherein the node is an electronic control unit, the electronic control unit having the current measurement unit, the current input / output unit, a first switch that opens and closes the current to the power line connected to the electronic control unit, a second switch that opens and closes the current to a load connected to the electronic control unit, and a control circuit, and the control circuit controls the first and second switches.

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