An in-vehicle device of the present invention includes a fuse and an upstream capacitor having one end connected to a connection node upstream of the fuse in a current path of current that flows through the fuse. One end of a downstream capacitor is connected to a connection node downstream of the fuse in the current path. A determiner determines whether or not the fuse is blown based on an upstream voltage that passed through the upstream capacitor and a downstream voltage that passed through the downstream capacitor.

TECHNICAL FIELD

The present disclosure relates to an in-vehicle device.

BACKGROUND

JP 2003-212065A discloses an in-vehicle device that includes a fuse. In JP 2003-212065A, a battery supplies power to a load via the fuse.

In JP 2003-212065A, consideration is not given to a method for checking whether or not a fuse is blown. If it is necessary for a person to visually check whether or not a fuse is blown, the fuse needs to be arranged at a location in the in-vehicle device where it can be seen by a person. This limits the locations where the fuse can be arranged.

The present disclosure has been made in view of such circumstances, and an object of the present disclosure is to provide an in-vehicle device with a high degree of freedom regarding the arrangement of a fuse.

SUMMARY

An in-vehicle device according to an aspect of the present disclosure includes: a fuse; an upstream capacitor having one end connected to a connection node located upstream of the fuse in a current path of current that flows through the fuse; a downstream capacitor having one end connected to a connection node located downstream of the fuse in the current path; and a determiner configured to determine whether or not the fuse is blown based on an upstream voltage that passed through the upstream capacitor and a downstream voltage that passed through the downstream capacitor.

Advantageous Effects

According to the above aspect, there is a high degree of freedom regarding the arrangement of a fuse.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

First, embodiments of the present disclosure will be listed and described. At least portions of the embodiments described below may be combined.

An in-vehicle device according to an aspect of the present disclosure includes: a fuse; an upstream capacitor having one end connected to a connection node located upstream of the fuse in a current path of current that flows through the fuse; a downstream capacitor having one end connected to a connection node located downstream of the fuse in the current path; and a determiner configured to determine whether or not the fuse is blown based on an upstream voltage that passed through the upstream capacitor and a downstream voltage that passed through the downstream capacitor.

In the above aspect, the AC component of the voltage of the connection node located upstream of the fuse passes through the upstream capacitor. The AC component of the voltage of the connection node located downstream of the fuse passes through the downstream capacitor. If the fuse is not blown, the waveform of the upstream voltage across the upstream capacitor substantially matches the waveform of the downstream voltage across the downstream capacitor. If the fuse is blown, the waveform of the upstream voltage is different from the waveform of the downstream voltage. The determiner determines whether or not the fuse is blown based on the upstream voltage and the downstream voltage. Since the determiner makes the determination, there is no need for a person to visually check whether the fuse is blown. As a result, there is a high degree of freedom regarding the arrangement of the fuse.

In another aspect of the present disclosure, the in-vehicle device may further include a substrate, and a terminal of the fuse may be attached to the substrate by solder.

In the above aspect, the fuse is attached to the substrate. If the fuse is blown, the substrate is replaced.

In another aspect of the present disclosure, the in-vehicle device may further include: an upstream reduction circuit configured to reduce a peak value of the upstream voltage; and a downstream reduction circuit configured to reduce a peak value of the downstream voltage, and the determiner may determine whether or not the fuse is blown based on the upstream voltage whose peak value was reduced by the upstream reduction circuit and the downstream voltage whose peak value was reduced by the downstream reduction circuit.

In the above aspect, the upstream reduction circuit and the downstream reduction circuit respectively reduce the peak values of the upstream voltage and the downstream voltage. This prevents a voltage with a large absolute value from being applied to the determiner.

In another aspect of the present disclosure, the determiner may determine that the fuse is blown in a case where the upstream voltage is greater than or equal to a first threshold and furthermore the downstream voltage is below a second threshold, and the first threshold may be greater than the second threshold.

In the above aspect, if the fuse is blown, the voltage of the connection node located upstream of the fuse increases due to, for example, the inductor component of a conducting wire located upstream of the fuse. The upstream voltage thus also increases. Also, if the fuse is blown, the voltage of the connection node located downstream of the fuse decreases due to, for example, the inductor component of a conducting wire located downstream of the fuse. The downstream voltage thus also decreases. The determiner determines that the fuse is blown if the upstream voltage is greater than or equal to the first threshold and furthermore the downstream voltage is below the second threshold.

In another aspect of the present disclosure, the determiner may include: a first resistor having one end to which a constant voltage is applied; a switch downstream of the first resistor in a second current path of current that flows through the first resistor; and a second resistor downstream of the switch in the second current path, a voltage of a connection node between the first resistor and the switch may be output from the determiner, and the switch may be on in a case where the upstream voltage is greater than or equal to the first threshold and furthermore the downstream voltage is below the second threshold.

In the above aspect, when the switch is off, the determiner outputs a constant voltage. If the fuse is blown, the switch changes from off to on. When the switch is on, the first resistor and the second resistor divide the constant voltage. The determiner outputs the voltage divided by the first resistor and the second resistor. If the fuse is blown, the output voltage of the determiner decreases, thus giving a notification of blowout of the fuse.

In another aspect of the present disclosure, the in-vehicle device may further include: an upstream diode configured to prevent the upstream voltage from decreasing to a voltage below a first predetermined voltage; and a downstream diode configured to prevent the downstream voltage from decreasing to a voltage below a second predetermined voltage.

In the above aspect, the upstream diode is provided, and thus a voltage below the first predetermined voltage is not applied to the determiner. Since the downstream diode is provided, a voltage below the second current threshold is not applied to the determiner.

In another aspect of the present disclosure, the determiner may determine that the fuse is blown in a case where the upstream voltage is greater than or equal to a threshold and furthermore the downstream voltage is below a threshold.

In the above aspect, the determiner detects blowout of the fuse if the upstream voltage is greater than or equal to a threshold and furthermore the downstream voltage is below a threshold.

In another aspect of the present disclosure, the in-vehicle device may include two or more of the fuses and two or more of the downstream capacitors, ends of the downstream capacitors on one side may be connected to connection nodes downstream of the fuses in current paths of current that flows through the fuses, in the current paths, the fuses may have an upstream portion common to all of the fuses, one end of the upstream capacitor may be connected to a connection node of a common portion of the current paths, and the determiner may determine whether or not one of the fuses is blown based on the upstream voltage and the downstream voltage that passed through one of the downstream capacitors.

In the above aspect, the determiner determines whether or not one fuse is blown based on the common upstream voltage.

In another aspect of the present disclosure, the in-vehicle device may include two or more of the fuses and two or more of the downstream capacitors, ends of the downstream capacitors on one side may be connected to connection nodes downstream of the fuses in current paths of current that flows through the fuses, in the current paths, the fuses may have an upstream portion common to all of the fuses, one end of the upstream capacitor may be connected to a connection node of a common portion of the current paths, and the determiner may determine whether or not at least one of the fuses is blown based on the upstream voltage and the downstream voltages that passed through the downstream capacitors.

In the above aspect, the determiner determines whether or not at least one of the fuses is blown.

DETAILS OF EMBODIMENTS OF PRESENT DISCLOSURE

Specific examples of a power supply system according to an embodiment of the present disclosure will be described below with reference to the drawings. Note that the present disclosure is not limited to these examples, but rather is indicated by the scope of the claims, and is intended to include all modifications within the scope and meaning equivalent to the scope of the claims.

First Embodiment

Configuration of Power Supply System

FIG.1is a block diagram showing the main configuration of a power supply system1in a first embodiment. The power supply system1is installed in a vehicle M. The power supply system1includes a DC power supply10, an ECU11, a sensor12, and a load E1. The DC power supply10is a battery, for example. Also, “ECU” is an abbreviation for “electronic control unit”. The ECU11functions as an in-vehicle device. The load E1is a piece of electrical equipment. The ECU11includes a microcomputer20, an upstream extraction circuit A1, a downstream extraction circuit B1, and a fuse F1. The term “microcomputer” is sometimes abbreviated to “MC”.

The negative electrode of the DC power supply10is grounded. Grounding is achieved by connection to the body of the vehicle M, for example. The body of the vehicle M is a conductor. The positive electrode of the DC power supply10is connected to one end of an upstream conducting wire X1. The other end of the upstream conducting wire X1is connected to one end of the fuse F1. The other end of the fuse F1is connected to one end of a downstream conducting wire Y1. The other end of the downstream conducting wire Y1is connected to one end of the load E1. The other end of the load E1is grounded.

Current flows from the positive electrode of the DC power supply10to the upstream conducting wire X1, the fuse F1, the downstream conducting wire Y1, and the load E1in this order. Power is thus supplied to the load E1. While the load E1is operating, current flows through the upstream conducting wire X1, the fuse F1, and the downstream conducting wire Y1. When the load E1stops operating, current stops flowing through the upstream conducting wire X1, the fuse F1, and the downstream conducting wire Y1.

Hereinafter, the path of the current flowing from the positive electrode of the DC power supply10through the upstream conducting wire X1, the fuse F1, and the downstream conducting wire Y1will be simply referred to as the current path. In the current path, the connection node located upstream of the fuse F1will be referred to as the upstream node. The upstream node is located downstream of the upstream conducting wire X1. In the current path, the connection node located downstream of the fuse F1will be referred to as the downstream node. The downstream node is located upstream of the downstream conducting wire Y1. The voltage at the upstream node will be referred to as the upstream node voltage. The voltage at the downstream node will be referred to as the downstream node voltage. The reference potential of the upstream node voltage and the downstream node voltage is the ground potential, such as the potential of the body of the vehicle M.

In the ECU11, the upstream extraction circuit A1and the downstream extraction circuit B1are respectively connected to the upstream node and the downstream node. The upstream extraction circuit A1and the downstream extraction circuit B1are also each connected to the microcomputer20. The microcomputer20is also connected to the sensor12. The microcomputer20is also connected to a communication line Lc. One or more communication devices (not shown) mounted in the vehicle M are also connected to the communication line Lc.

The upstream extraction circuit A1extracts the AC component of the upstream node voltage. Hereinafter, the AC component of the upstream node voltage will be referred to as the upstream voltage. The upstream extraction circuit A1outputs the extracted upstream voltage to the microcomputer20. The downstream extraction circuit B1extracts the AC component of the downstream node voltage. Hereinafter, the AC component of the downstream node voltage will be referred to as the downstream voltage. The downstream extraction circuit B1outputs the extracted downstream voltage to the microcomputer20. The reference potential of the upstream voltage and the downstream voltage is the ground potential.

The microcomputer20detects blowout of the fuse F1based on the upstream voltage and the downstream voltage that have been input. In the case of detecting that the fuse F1is blown, the microcomputer20transmits a blowout signal indicating that the fuse F1is blown to a communication device via the communication line Lc. The microcomputer20detects the occurrence of a failure in the upstream extraction circuit A1or the downstream extraction circuit B1based on the upstream voltage and the downstream voltage that have been input. Upon detecting the occurrence of a failure, the microcomputer20transmits a failure signal indicating the occurrence of the failure to a communication device via the communication line Lc.

The sensor12detects a vehicle value regarding the vehicle M. Examples of the vehicle value include the speed of the vehicle M, the acceleration of the vehicle M, and the brightness around the vehicle M. Upon detecting the vehicle value, the sensor12outputs sensor data including the detected vehicle value to the microcomputer20. The microcomputer20transmits the received sensor data to a communication device via the communication line Lc.

The microcomputer20may determine the operation that is to be performed by the load E1. The microcomputer20determines the operation to be performed by the load E1based on, for example, the sensor data input from the sensor12or the data received via the communication line Lc. The microcomputer20outputs an operation signal indicating the determined operation to the load E1. Upon receiving the operation signal, the load E1performs the operation indicated by the input operation signal.

Method for Detecting Blowout of Fuse F1

When current flows through the fuse F1, the fuse F1generates heat. The amount of heat generated by the fuse F1increases as the current flowing through the fuse F1increases. In the fuse F1, when the amount of heat generated per unit time exceeds the amount of heat dissipated per unit time, the temperature of the fuse F1rises. When the temperature of the fuse F1reaches a certain temperature threshold, the fuse F1is blown. If a current that is above a certain current threshold flows through the fuse F1, the fuse F1is blown. This therefore prevents overcurrent from flowing through the upstream conducting wire X1and the downstream conducting wire Y1.

Blowout of the fuse F1occurs while current is flowing through the fuse F1. If the fuse F1is not blown, the upstream node voltage and the downstream node voltage substantially match each other. Therefore, the upstream voltage and the downstream voltage respectively extracted by the upstream extraction circuit A1and the downstream extraction circuit B1substantially match each other.

When the fuse F1is blown, current stops flowing through the upstream conducting wire X1and the downstream conducting wire Y1. As a result, the current flowing through the upstream conducting wire X1and the current flowing through the downstream conducting wire Y1decrease. The upstream conducting wire X1and the downstream conducting wire Y1each have an inductor component. When the current flowing through the upstream conducting wire X1decreases, the inductor component of the upstream conducting wire X1generates induced electromotive force. Specifically, in the upstream conducting wire X1, the voltage increases at the downstream end whose reference potential is the potential at the upstream end. The upstream node voltage thus increases. As a result, the upstream voltage increases.

When the current flowing through the downstream conducting wire Y1decreases, the inductor component of the downstream conducting wire Y1also generates induced electromotive force. Specifically, in the downstream conducting wire Y1, the voltage decreases at the upstream end whose reference potential is the potential at the downstream end. The downstream node voltage thus decreases. As a result, the downstream voltage decreases.

The upstream extraction circuit A1prevents the upstream voltage from dropping below a predetermined voltage. The predetermined voltage is a negative value, such as −0.6 V. Similarly, the downstream extraction circuit B1prevents the downstream voltage from dropping below a predetermined voltage. The microcomputer20detects blowout of the fuse F1when the upstream voltage is greater than or equal to a certain upper threshold and furthermore the downstream voltage is below the upper threshold. The upper threshold is a positive value.

Arrangement of Fuse F1

FIG.2is an illustrative diagram of the arrangement of the fuse F1. The ECU11has a rectangular substrate Q. The microcomputer20, the upstream extraction circuit A1, the downstream extraction circuit B1, and the fuse F1are arranged on a main face of the substrate Q. The main face is one of the large faces of the substrate, and is different from the end faces.

Attachment of Fuse F1

FIG.3is an illustrative diagram of attachment of the fuse F1.FIG.3shows an external view of the fuse F1and a cross-section of the substrate Q. In the fuse F1, a rod-shaped first terminal31and a rod-shaped second terminal32are housed in a hollow cuboid housing box30that is open on one side. The first terminal31and the second terminal32each have one end portion that projects outward from the open side of the housing box30.

Inside the housing box30, the first terminal31and the second terminal32are connected by a fuse portion (not shown). Current flows through the first terminal31, the fuse portion, and the second terminal32in this order. When current flows through the fuse portion, the fuse portion generates heat. The amount of heat generated by the fuse portion increases as the current flowing through the fuse portion increases. In the fuse portion, when the amount of heat generated per unit time exceeds the amount of heat dissipated per unit time, the temperature of the fuse portion rises. When the temperature of the fuse portion reaches the previously mentioned temperature threshold, the fuse portion is blown. When the fuse portion is blown, current stops flowing through the fuse portion. The blowing of the fuse portion corresponds to the blowing of the fuse F1.

A rectangular insulating plate40having an insulating property is arranged on the substrate Q. The insulating plate40includes a first through hole40aand a second through hole40bthat pass through the plate in the thickness direction. On the upper main face of the insulating plate40, a first conductive pattern41and a second conductive pattern42, which have conductivity are respectively arranged around the first through hole40aand the second through hole40b.

The inner surface of the first through hole40aof the substrate Q is covered by a first plating43that has conductivity. The first plating43has an inner surface portion that covers the inner surface of the first through hole40a, an upper portion that covers the insulating plate40from above the first conductive pattern41, and a lower portion that covers the insulating plate40from below. The inner surface portion of the first plating43is connected to both the upper portion and the lower portion. The first plating43is electrically connected to the first conductive pattern41.

Similarly, the inner surface of the second through hole40bof the substrate Q is covered by a second plating44that has conductivity. The second plating44has an inner surface portion that covers the inner surface of the second through hole40b, an upper portion that covers the insulating plate40from above the second conductive pattern42, and a lower portion that covers the insulating plate40from below. The inner surface portion of the second plating44is connected to both the upper portion and the lower portion. The second plating44is electrically connected to the second conductive pattern42.

The first terminal31and the second terminal32of the fuse F1are respectively inserted into the first through hole40aand the second through hole40bof the insulating plate40. The first terminal31is located inward of the first plating43in the first through hole40a. The second terminal32is located inward of the second plating44in the second through hole40b. The first terminal31is attached to the first plating43by solder H. The solder H has conductivity. The first terminal31is electrically connected to the first conductive pattern41via the first plating43. The second terminal32is attached to the second plating44by solder H. The second terminal32is electrically connected to the second conductive pattern42via the second plating44. The upper sides of the insulating plate40, the first plating43, and the second plating44are covered with a resist45that has an insulating property.

The first terminal31and the second terminal32are respectively the upstream end and the downstream end of the fuse F1. Current flows from the positive electrode of the DC power supply10to the first conductive pattern41, the first terminal31, the fuse portion, the second terminal32, the second conductive pattern42, and the load E1in this order.

As described above, the first terminal31and the second terminal32of the fuse F1are each attached to the substrate Q by the solder H. Therefore, if the fuse F1is blown, the substrate Q is replaced. The fuse F1is a mechanical fuse. One example of the fuse F1is a blade fuse. In this case, the first terminal31and the second terminal32each have a flat plate shape. The fuse F1need only be a fuse that can be attached to the substrate Q by the solder H. Therefore, the fuse F1may be a chip fuse, a thermal fuse, or a fusible link, for example.

Configuration of Upstream Extraction Circuit A1

FIG.4is a circuit diagram of the upstream extraction circuit A1. The upstream extraction circuit A1includes a first capacitor50, a reduction circuit51, a diode52, and a first circuit resistor53. The reduction circuit51includes a second circuit resistor60and a second capacitor61. One end of the first capacitor50is connected to the upstream node of the fuse F1. The first capacitor50of the upstream extraction circuit A1functions as an upstream capacitor.

Inside the reduction circuit51, the other end of the first capacitor50is connected to one end of the second circuit resistor60of the reduction circuit51. The other end of the second circuit resistor60is connected to the microcomputer20, the cathode of the diode52, one end of the first circuit resistor53, and one end of the second capacitor61of the reduction circuit51. The anode of the diode52, the other end of the first circuit resistor53, and the other end of the second capacitor61are grounded.

FIG.5is a waveform diagram for describing operation of the upstream extraction circuit A1.FIG.5shows the waveform of the upstream node voltage, the waveform of the upstream voltage that passed through the first capacitor50, the waveform of the upstream voltage that passed through the reduction circuit51, and the waveform of the upstream voltage that is output to the microcomputer20. Time is shown on the horizontal axis of these waveforms. For example, if a surge occurs in the current path or disturbance noise enters the current path, an AC component will appear in the upstream node voltage. InFIG.5, the upper threshold is denoted by Vp.

The voltage across the DC power supply10will be referred to as the power supply voltage. InFIG.5, the power supply voltage is denoted by Vb. When there is no AC component, the upstream node voltage matches the power supply voltage Vb. When there is an AC component, the upstream node voltage varies from the power supply voltage Vb. In the example shown inFIG.5, a positive surge voltage that raises the upstream node voltage and a negative surge voltage that lowers the upstream node voltage are shown. The positive surge voltage first increases over time, and then decreases over time. The negative surge voltage first decreases over time, and then increases over time.

As shown inFIG.5, the first capacitor50extracts the AC component from the upstream node voltage. As described above, the AC component of the upstream node voltage will be referred to as the upstream voltage. The upstream voltage passing through the first capacitor50varies from zero V. The upstream voltage passing through the first capacitor50includes a positive surge voltage and a negative surge voltage.

In the reduction circuit51, the upstream voltage that passed through the first capacitor50is applied to the second capacitor61via the second circuit resistor60. The second circuit resistor60limits the amount of current flowing through first capacitor50. The second capacitor61smoothes the voltage applied thereto via the second circuit resistor60. The reduction circuit51thus reduces the peak value (absolute value) of the upstream voltage that passed through the first capacitor50. As a result, this prevents a voltage with a large absolute value from being applied to the microcomputer20. The voltage across the second capacitor61is output as an upstream voltage whose peak value was reduced by the reduction circuit51.

If the upstream voltage that passed through the reduction circuit51drops to a certain predetermined voltage that is a negative value, current flows through the anode and cathode of the diode52in this order. The voltage therefore never drops to a voltage below the predetermined voltage. The diode52prevents the upstream voltage whose peak value was reduced by the reduction circuit51from dropping to a voltage below the predetermined voltage. Accordingly a voltage below the predetermined voltage is never applied to the microcomputer20. The diode52of the upstream extraction circuit A1functions as an upstream diode. The absolute value of the predetermined voltage is the absolute value of the forward voltage of the diode52, and is 0.6 V for example. Due to the diode52, an upstream voltage that is prevented from dropping below the predetermined voltage is applied across the first circuit resistor53. The upstream voltage applied across the first circuit resistor53is output to the microcomputer20.

The allowable range of voltage that is allowed to be input to the microcomputer20is limited. Due to the operation of the reduction circuit51and the diode52, the voltage input to the microcomputer20falls within the allowable range.

Configuration of Downstream Extraction Circuit B1

As shown inFIG.4, the downstream extraction circuit B1has a configuration similar to that of the upstream extraction circuit A1. In the description of the configuration of the upstream extraction circuit A1, replace the upstream extraction circuit A1, the upstream node, the upstream node voltage, and the upstream voltage respectively with the downstream extraction circuit B1, the downstream node, the downstream node voltage, and the downstream voltage. This therefore obtains a description of the configuration of the downstream extraction circuit B1.

Accordingly, one end of the first capacitor50of the downstream extraction circuit B1is connected to the downstream node. In the downstream extraction circuit B1, the reduction circuit51reduces the peak value of the downstream voltage that passed through the first capacitor50. Accordingly this prevents a voltage with a large absolute value from being applied to the microcomputer20. The diode52of the downstream extraction circuit B1prevents the downstream voltage whose peak value was reduced by the reduction circuit51from dropping to a voltage below a predetermined voltage. Accordingly a voltage below the predetermined voltage is never applied to the microcomputer20. Due to the operation of the reduction circuit51and the diode52, the voltage input to the microcomputer20falls within the allowable range. The first capacitor50, the reduction circuit51, and the diode52of the downstream extraction circuit B1respectively function as a downstream capacitor, a downstream reduction circuit, and a downstream diode. Note that it is preferable that the first capacitors50of the upstream extraction circuit A1and the downstream extraction circuit B1have the same capacitance.

The predetermined voltage of the diode52of the upstream extraction circuit A1corresponds to a first predetermined voltage. The predetermined voltage of the diode52of the downstream extraction circuit B1corresponds to a second predetermined voltage. It is preferable that the predetermined voltage of the diode52of the upstream extraction circuit A1is the same as the predetermined voltage of the diode52of the downstream extraction circuit B1.

Determination of State of ECU11

FIG.6is a chart showing the relationship between states of the ECU11and output voltages of the upstream extraction circuit A1and the downstream extraction circuit B1. As shown inFIG.6, when the output voltages of the upstream extraction circuit A1and the downstream extraction circuit B1are both below the upper threshold Vp, or greater than or equal to the upper threshold Vp, the microcomputer20determines that the state of the ECU11is a normal state. When the output voltage of the upstream extraction circuit A1is greater than or equal to the upper threshold Vp and furthermore the output voltage of the downstream extraction circuit B1is below the upper threshold Vp, the microcomputer20determines that the fuse F1is blown.

As long as a failure has not occurred in the upstream extraction circuit A1or the downstream extraction circuit B1, the state of the ECU11does not transition to a state in which the output voltage of the upstream extraction circuit A1is below the upper threshold Vp and furthermore the output voltage of the downstream extraction circuit B1is greater than or equal to the upper threshold Vp. Accordingly, when the output voltage of the upstream extraction circuit A1is below the upper threshold Vp and furthermore the output voltage of the downstream extraction circuit B1is greater than or equal to the upper threshold Vp, the microcomputer20determines that a failure has occurred in the upstream extraction circuit A1or the downstream extraction circuit B1.

Operation of Microcomputer20

The microcomputer20includes a processing element that executes processing and a storage unit that stores data. The processing element is a CPU (Central Processing Unit), for example. The storage unit is constituted by a volatile memory and a nonvolatile memory, for example. A computer program is stored in the storage unit. In the microcomputer20, the processing element executes blowout detection processing to detect blowout of the fuse F1, by executing a computer program. Note that the microcomputer20may include two or more processing elements. In this case, the processing elements may execute the blowout detection processing in cooperation with each other.

FIG.7is a flowchart showing a procedure of blowout detection processing. In the blowout detection processing, first, the microcomputer20acquires the output voltage of the upstream extraction circuit A1(step S1). Next, the microcomputer20acquires the output voltage of the downstream extraction circuit B1(step S2). The microcomputer20determines whether or not the fuse F1is blown based on the two output voltages obtained in steps S1and S2(step S3). In step S3, as shown inFIG.6, if the output voltage of the upstream extraction circuit A1is greater than or equal to the upper threshold Vp and furthermore the output voltage of the downstream extraction circuit B1is below the upper threshold Vp, the microcomputer20determines that the fuse F1is blown.

The output voltage of the upstream extraction circuit A1is the upstream voltage that passed through the first capacitor50of the upstream extraction circuit A1, and is the upstream voltage whose peak value was reduced by the reduction circuit51of the upstream extraction circuit A1. The output voltage of the downstream extraction circuit B1is the downstream voltage that passed through the first capacitor50of the downstream extraction circuit B1, and is the downstream voltage whose peak value was reduced by the reduction circuit51of the downstream extraction circuit B1. The microcomputer20therefore functions as a determiner.

In the case of determining that the fuse F1is blown (S3: YES), the microcomputer20transmits the blowout signal to a communication device via the communication line Lc (step S4). In the case of determining that the fuse F1is not blown (S3: NO), the microcomputer20determines whether or not a failure has occurred in the upstream extraction circuit A1or the downstream extraction circuit B1(step S5). In step S5, as shown inFIG.6, if the output voltage of the upstream extraction circuit A1is below the upper threshold Vp and furthermore the output voltage of the downstream extraction circuit B1is greater than or equal to the upper threshold Vp, the microcomputer20determines that a failure has occurred in the upstream extraction circuit A1or the downstream extraction circuit B1.

In the case of determining that a failure has occurred (S5: YES), the microcomputer20transmits the failure signal to a communication device via the communication line Lc (step S6). After executing steps S4and S6, the microcomputer20ends the blowout detection processing. In this case, the microcomputer20does not execute the blowout detection processing again.

If the output voltages of the upstream extraction circuit A1and the downstream extraction circuit B1are both below the upper threshold Vp, or greater than or equal to the upper threshold Vp, in step S5, the microcomputer20determines that a failure has not occurred. In the case of determining that a failure has not occurred (S5: NO), the microcomputer20ends the blowout detection processing. In this case, the microcomputer20executes the blowout detection processing again. The microcomputer20periodically executes the blowout detection processing until blowout of the fuse F1or the occurrence of a failure is detected.

Effects of ECU11

In the ECU11, the microcomputer20determines whether or not the fuse F1is blown. Therefore, there is no need for a person to visually check whether the fuse F1is blown. As a result, there is a high degree of freedom regarding the arrangement of the fuse F1, that is to say the substrate Q.

Second Embodiment

In the first embodiment, power is supplied to one load via the ECU11. However, power may be supplied to two or more loads via the ECU11. The following description of a second embodiment focuses on differences from the first embodiment. Configurations other than those described below are the same as those of the first embodiment, and constituent elements that are the same as those of the first embodiment are denoted by the same reference signs as in the first embodiment and will not be described.

Configuration of Power Supply System1

FIG.8is a block diagram showing the main configuration of the power supply system1in the second embodiment. The power supply system1of the second embodiment includes the DC power supply10, the ECU11, and the sensor12, similarly to the first embodiment. The power supply system1of the second embodiment further includes a plurality of loads E1, E2, . . . and an upstream switch G1. A plurality of downstream conducting wires Y1, Y2, . . . are arranged in the power supply system1of the second embodiment. Similarly to the first embodiment, the ECU11in the second embodiment includes the microcomputer20and the upstream extraction circuit A1. The ECU11in the second embodiment further includes a plurality of downstream extraction circuits B1, B2, . . . and a plurality of fuses F1, F2, and so on.

In the following, “i” represents a natural number. The natural number “i” may be 1, 2, or so on. The load Ei is a piece of electrical equipment. The positive electrode of the DC power supply10is connected to one end of the upstream switch G1. The other end of the upstream switch G1is connected to one end of the upstream conducting wire X1. The other end of the upstream conducting wire X1is connected to one end of the fuse Fi. The other end of the fuse Fi is connected to one end of the downstream conducting wire Yi. The other end of the downstream conducting wire Yi is connected to one end of the load Ei. The other end of the load Ei is grounded.

The upstream switch G1is the ignition switch of the vehicle M, for example. When the upstream switch G1is on, current flows from the positive electrode of the DC power supply10to the upstream switch G1, the upstream conducting wire X1, the fuse Fi, the downstream conducting wire Yi, and the load Ei in this order. Power is thus supplied to the load Ei. While the load Ei is operating, current flows through the upstream switch G1, the upstream conducting wire X1, the fuse Fi, and the downstream conducting wire Yi. When the load Ei stops operating, current stops flowing through the upstream switch G1, the upstream conducting wire X1, the fuse Fi, and the downstream conducting wire Yi. When the upstream switch G1is off, current does not flow through the fuses F1, F2, and so on. Note that the microcomputer20may control operation of the load Ei similarly to operation of the load E1in the first embodiment.

Hereinafter, the path of current flowing from the positive electrode of the DC power supply10through the upstream switch G1, the upstream conducting wire X1, the fuse Fi, and the downstream conducting wire Yi will be referred to as the current path of the fuse Fi. In the current paths of the fuses F1, F2, . . . , the fuses F1, F2, . . . have an upstream portion common to all of the fuses F1, F2, and so on. In the second embodiment, the upstream node is the connection node of the common portion on the upstream side of the fuses F1, F2, . . . in the current paths. The upstream node is located downstream of the upstream conducting wire X1. One end of the first capacitor50of the upstream extraction circuit A1is connected to the upstream node, similarly to the first embodiment.

In the second embodiment, the connection node located downstream of the fuse Fi in the current path of the fuse Fi will be referred to as the downstream node of the fuse Fi. The downstream node of the fuse Fi is located upstream of downstream conducting wire Yi. Similarly to first embodiment, the voltage at the upstream node will be referred to as the upstream node voltage. In the second embodiment, the voltage at the downstream node of the fuse Fi will be referred to as the downstream node voltage of the fuse Fi. The reference potential of the upstream node voltage and the downstream node voltages of the fuses F1, F2, . . . is the ground potential.

As mentioned in the description of the first embodiment, the upstream voltage is the AC component of the upstream node voltage. In the second embodiment, the downstream extraction circuit Bi extracts the AC component of the downstream node voltage of the fuse Fi. In the following, the AC component of the downstream node voltage of the fuse Fi will be referred to as the downstream voltage of the fuse Fi. The downstream extraction circuit Bi outputs the extracted downstream voltage of the fuse Fi to the microcomputer20. The reference potential of the downstream voltage of the fuse Fi is the ground potential.

The microcomputer20detects blowout of the fuse Fi based on the upstream voltage and the downstream voltage of the fuse Fi. Upon detecting that the fuse Fi is blown, the microcomputer20transmits a blowout signal indicating that the fuse Fi is blown to a communication device via the communication line Lc. The microcomputer20detects the occurrence of a failure in the upstream extraction circuit A1or the downstream extraction circuit Bi based on the upstream voltage and the downstream voltage of the fuse Fi. Upon detecting the occurrence of a failure, the microcomputer20transmits a failure signal indicating the occurrence of the failure to a communication device via the communication line Lc.

Method for Detecting Blowout of Fuse Fi

When upstream switch G1is off, current does not flow through the fuse Fi, and thus blowout of the fuse Fi does not occur. While the upstream switch G1is on, if the temperature of the fuse Fi reaches a temperature threshold, the fuse Fi is blown.

The upstream conducting wire X1operates similarly to the first embodiment. The fuse Fi and the downstream conducting wire Yi operate similarly to the fuse F1and the downstream conducting wire Y1of the first embodiment. When the fuse Fi is blown, the current flowing through the upstream conducting wire X1decreases. The inductor component of the upstream conducting wire X1generates an induced electromotive force. Therefore, in the upstream conducting wire X1, the voltage increases at the downstream end whose reference potential is the potential at the upstream end. As a result, the upstream node voltage increases, and thus the upstream voltage increases. When the fuse Fi is blown, the current flowing through the downstream conducting wire Yi decreases. The inductor component of the downstream conducting wire Yi generates an induced electromotive force. Therefore, in the downstream conducting wire Yi, the voltage decreases at the upstream end whose reference potential is the potential at the downstream end. As a result, the downstream node voltage decreases, and thus the downstream voltage decreases.

Similarly to the first embodiment, the upstream extraction circuit A1prevents the upstream voltage from dropping below a predetermined voltage. Similarly to the downstream extraction circuit B1of the first embodiment, the downstream extraction circuit Bi prevents the downstream voltage of the fuse Fi from dropping to a voltage below a predetermined voltage. If the upstream voltage is greater than or equal to the upper threshold and furthermore the downstream voltage of the fuse Fi is below the upper threshold, the microcomputer20detects that the fuse Fi is blown.

The fuses F1, F2, . . . are each arranged on a main face of the substrate Q. The fuse Fi has a configuration similar to that of the fuse F1of the first embodiment. The first terminal31and the second terminal32of the fuse Fi are each attached to the substrate Q by solder H. Therefore, if at least one of the fuses F1, F2, . . . is blown, the substrate Q is replaced.

Configuration of Downstream Extraction Circuit Bi

The downstream extraction circuit Bi has a configuration similar to that of the downstream extraction circuit Bi in the first embodiment. The downstream extraction circuit Bi therefore includes the first capacitor50, the reduction circuit51, the diode52, and the first circuit resistor53. One end of the first capacitor50of the downstream extraction circuit Bi is connected to the downstream node of the fuse Fi. The AC component of the downstream node voltage of the fuse Fi (i.e., the downstream voltage of the fuse Fi) passes through the first capacitor50of the downstream extraction circuit Bi. Note that it is preferable that the first capacitors50of the upstream extraction circuit A1and the downstream extraction circuit Bi have the same capacitance.

In the downstream extraction circuit Bi, the reduction circuit51reduces the peak value of the downstream voltage that passed through the first capacitor50. Accordingly, this prevents a voltage with a large absolute value from being applied to the microcomputer20. The diode52of the downstream extraction circuit Bi prevents the downstream voltage whose peak value was reduced by the reduction circuit51from dropping to a voltage below a predetermined voltage. Accordingly, a voltage below the predetermined voltage is never applied to the microcomputer20. Due to the operation of the reduction circuit51and the diode52, the voltage input to the microcomputer20falls within the allowable range. The first capacitor50, the reduction circuit51, and the diode52of the downstream extraction circuit Bi respectively function as a downstream capacitor, a downstream reduction circuit, and a downstream diode. The ECU11includes a plurality of downstream extraction circuits B1, B2, and so on. Therefore, two or more first capacitors50function as downstream capacitors.

Determination of State of ECU11

FIG.9is a chart showing the relationship between states of the ECU11and output voltages of the upstream extraction circuit A1and the downstream extraction circuit Bi. As shown inFIG.9, when the output voltages of the upstream extraction circuit A1and the downstream extraction circuit Bi are both below the upper threshold Vp, or greater than or equal to the upper threshold Vp, the microcomputer20determines that the state of the ECU11is a normal state. When the output voltage of the upstream extraction circuit A1is greater than or equal to the upper threshold Vp and furthermore the output voltage of the downstream extraction circuit Bi is below the upper threshold Vp, the microcomputer20determines that the fuse Fi is blown.

As long as a failure has not occurred in the upstream extraction circuit A1or the downstream extraction circuit Bi, the state of the ECU11does not transition to a state in which the output voltage of the upstream extraction circuit A1is below the upper threshold Vp and furthermore the output voltage of the downstream extraction circuit Bi is greater than or equal to the upper threshold Vp. Accordingly, when the output voltage of the upstream extraction circuit A1is below the upper threshold Vp and furthermore the output voltage of the downstream extraction circuit Bi is greater than or equal to the upper threshold Vp, the microcomputer20determines that a failure has occurred in the upstream extraction circuit A1or the downstream extraction circuit Bi.

Operation of Microcomputer20

The microcomputer20executes blowout detection processing to detect blowout of the fuse Fi, by executing a computer program. When the upstream switch G1is on, the microcomputer20executes blowout detection processing for each of the fuses F1, F2, and so on. If the microcomputer20includes two or more processing elements, the processing elements may execute the blowout detection processing for the fuses F1, F2, . . . in cooperation with each other.

The blowout detection processing for the fuse Fi is similar to the blowout detection processing for the fuse F1in the first embodiment. In the description of the blowout detection processing of the fuse F1in the first embodiment, replace the downstream extraction circuit B1and the fuse F1respectively with the downstream extraction circuit Bi and the fuse Fi. This therefore obtains a description of blowout detection processing for the fuse Fi. In the blowout detection processing for the fuse Fi, the microcomputer20determines whether or not the fuse Fi is blown based on the upstream voltage and the downstream voltage of the fuse Fi. As described above, the microcomputer20uses the common upstream voltage to determine whether or not the fuse Fi is blown.

Effects of ECU11

The ECU11in the second embodiment has effects similar to those of the ECU11in the first embodiment.

Third Embodiment

In the second embodiment, a switch may be placed in the current paths of the fuses F1, F2, and so on.

The following description of a third embodiment focuses on differences from the second embodiment. Configurations other than those described below are the same as those of the second embodiment, and constituent elements that are the same as those of the second embodiment are denoted by the same reference signs as in the second embodiment and will not be described.

Configuration of Power Supply System1

FIG.10is a block diagram showing the main configuration of the power supply system1in the third embodiment. Similarly to the second embodiment, the power supply system1of the third embodiment includes the DC power supply10, the ECU11, the sensor12, and a plurality of loads E1, E2, and so on. The power supply system1of the third embodiment further includes a plurality of upstream switches G1, G2, and so on. A plurality of upstream conducting wires X1, X2, . . . are arranged in the power supply system1according to the third embodiment.

The positive electrode of the DC power supply10is connected to one end of each of the upstream switches G1, G2, and so on. The other end of the upstream switch Gi is connected to one end of the upstream conducting wire Xi. As mentioned in the description of the second embodiment, “i” is a natural number. The other end of the upstream conducting wire Xi is connected to one end of the fuse Fi.

When the upstream switch Gi is on, current flows from the positive electrode of the DC power supply10to the upstream switch Gi, the upstream conducting wire Xi, the fuse Fi, the downstream conducting wire Yi, and the load Ei in this order. Power is thus supplied to the load Ei. While the load Ei is operating, current flows through the upstream switch Gi, the upstream conducting wire Xi, the fuse Fi, and the downstream conducting wire Yi. When the load Ei stops operating, current stops flowing through the upstream switch Gi, the upstream conducting wire Xi, the fuse Fi, and the downstream conducting wire Yi. When upstream switch Gi is off, current does not flow through the fuse Fi.

In the third embodiment, the current path of the fuse Fi is the path of current that flows from the positive electrode of the DC power supply10through the upstream switch Gi, the upstream conducting wire Xi, the fuse Fi, and the downstream conducting wire Yi. In the current path of the fuse Fi, the connection node located upstream of the fuse Fi will be referred to as the upstream node of the fuse Fi. The upstream node of the fuse Fi is located downstream of the upstream conducting wire Xi. The voltage at the upstream node of the fuse Fi will be referred to as the upstream node voltage of the fuse Fi. The reference potential of the upstream node voltage of the fuse Fi is the ground potential. In the third embodiment, the downstream node and the downstream node voltage of the fuse Fi are defined similarly to the second embodiment.

The upstream extraction circuit Ai extracts the AC component of the upstream node voltage of the fuse Fi. Hereinafter, the AC component of the upstream node voltage of the fuse Fi will be referred to as the upstream voltage of the fuse Fi. The upstream extraction circuit Ai outputs the extracted upstream voltage of the fuse Fi to the microcomputer20. The reference potential of the upstream voltage of the fuse Fi is the ground potential.

The microcomputer20detects blowout of the fuse Fi based on the upstream voltage and the downstream voltage of the fuse Fi. Upon detecting that the fuse Fi is blown, the microcomputer20transmits a blowout signal indicating that the fuse Fi is blown to a communication device via the communication line Lc. The microcomputer20detects the occurrence of a failure in the upstream extraction circuit Ai or the downstream extraction circuit Bi based on the upstream voltage and the downstream voltage of the fuse Fi. Upon detecting the occurrence of a failure, the microcomputer20transmits a failure signal indicating the occurrence of the failure to a communication device via the communication line Lc.

Method for Detecting Blowout of Fuse Fi

When the upstream switch Gi is off, current does not flow through the fuse Fi, and thus blowout of the fuse Fi does not occur. While the upstream switch Gi is on, if the temperature of the fuse Fi reaches a temperature threshold, the fuse Fi is blown.

The upstream conducting wire Xi operates similarly to the upstream conducting wire X1in the first embodiment. When the fuse Fi is blown, the current flowing through the upstream conducting wire Xi decreases. The inductor component of the upstream conducting wire Xi generates an induced electromotive force. Therefore, in the upstream conducting wire Xi, the voltage increases at the downstream end whose reference potential is the potential at the one end on the upstream side. As a result, the upstream node voltage of the fuse Fi increases, and thus the upstream voltage of the fuse Fi increases. Similarly to the second embodiment, when the fuse Fi is blown, in the downstream conducting wire Yi, the voltage increases at upstream end whose reference potential is the potential at the one downstream end. As a result, the downstream node voltage of the fuse Fi decreases, and thus the downstream voltage of the fuse Fi decreases.

Similarly to the upstream extraction circuit A1in the first embodiment, the upstream extraction circuit Ai prevents the upstream voltage of the fuse Fi from dropping to a voltage below a predetermined voltage. Similarly to the second embodiment, the downstream extraction circuit Bi prevents the downstream voltage of the fuse Fi from dropping to a voltage below a predetermined voltage. The microcomputer20detects blowout of the fuse F1when the upstream voltage of the fuse Fi is greater than or equal to the upper threshold and furthermore the downstream voltage of the fuse Fi is below the upper threshold.

Configuration of Upstream Extraction Circuit Ai

The upstream extraction circuit Ai has a configuration similar to that of the upstream extraction circuit A1in the first embodiment. The upstream extraction circuit Ai therefore includes the first capacitor50, the reduction circuit51, the diode52, and the first circuit resistor53. One end of the first capacitor50of the upstream extraction circuit Ai is connected to the upstream node of the fuse Fi. The AC component of the upstream node voltage of the fuse Fi (i.e., the upstream voltage of the fuse Fi) passes through the first capacitor50of the upstream extraction circuit Ai. Note that it is preferable that the first capacitors50of the upstream extraction circuit Ai and the downstream extraction circuit Bi have the same capacitance.

In the upstream extraction circuit Ai, the reduction circuit51reduces the peak value of the upstream voltage that passed through the first capacitor50. Accordingly, this prevents a voltage with a large absolute value from being applied to the microcomputer20. The diode52of the upstream extraction circuit Ai prevents the upstream voltage whose peak value was reduced by the reduction circuit51from dropping to a voltage below a predetermined voltage. Accordingly, a voltage below the predetermined voltage is never applied to the microcomputer20. Due to the operation of the reduction circuit51and the diode52, the voltage input to the microcomputer20falls within the allowable range. The first capacitor50, the reduction circuit51, and the diode52of the upstream extraction circuit Ai respectively function as an upstream capacitor, an upstream reduction circuit, and an upstream diode. The ECU11includes a plurality of upstream extraction circuits A1, A2, and so on. Therefore, two or more first capacitors50function as upstream capacitors.

Determination of State of ECU11

The relationship between states of the ECU11and the output voltages of the upstream extraction circuit Ai and the downstream extraction circuit Bi is similar to the relationship between states of the ECU11and the output voltages of the upstream extraction circuit A1and the downstream extraction circuit B1(seeFIG.6). Therefore, when the output voltages of the upstream extraction circuit Ai and the downstream extraction circuit Bi are both below the upper threshold Vp, or greater than or equal to the upper threshold Vp, the microcomputer20determines that the state of the ECU11is a normal state. When the output voltage of the upstream extraction circuit Ai is greater than or equal to the upper threshold Vp and furthermore the output voltage of the downstream extraction circuit Bi is below the upper threshold Vp, the microcomputer20determines that the fuse Fi is blown.

As long as a failure has not occurred in the upstream extraction circuit Ai or the downstream extraction circuit Bi, the state of the ECU11does not transition to a state in which the output voltage of the upstream extraction circuit Ai is below the upper threshold Vp and furthermore the output voltage of the downstream extraction circuit Bi is greater than or equal to the upper threshold Vp. Accordingly, when the output voltage of the upstream extraction circuit Ai is below the upper threshold Vp and furthermore the output voltage of the downstream extraction circuit Bi is greater than or equal to the upper threshold Vp, the microcomputer20determines that a failure has occurred in the upstream extraction circuit Ai or the downstream extraction circuit Bi.

Operation of Microcomputer20

The microcomputer20executes blowout detection processing to detect blowout of the fuse Fi, by executing a computer program. When the upstream switch Gi is on, the microcomputer20executes blowout detection processing for the fuse Fi. If the microcomputer20includes two or more processing elements, the processing elements may execute the blowout detection processing for the fuses F1, F2, . . . in cooperation with each other.

The blowout detection processing for the fuse Fi is similar to the blowout detection processing for the fuse F1in the first embodiment. In the description of the blowout detection processing of the fuse F1in the first embodiment, replace the upstream extraction circuit A1, the downstream extraction circuit B1, and the fuse F1respectively with the upstream extraction circuit Ai, the downstream extraction circuit Bi, and the fuse Fi. This therefore obtains a description of blowout detection processing for the fuse Fi. In the blowout detection processing for the fuse Fi, the microcomputer20determines whether or not the fuse Fi is blown based on the upstream voltage and the downstream voltage of the fuse Fi.

Effects of ECU11

The ECU11in the third embodiment has effects similar to those of the ECU11in the first embodiment.

Fourth Embodiment

In the first embodiment, the upstream extraction circuit A1and the downstream extraction circuit B1may each have a configuration in which the diode52is omitted.

The following description of a fourth embodiment focuses on differences from the first embodiment. Configurations other than those described below are the same as those of the first embodiment, and constituent elements that are the same as those of the first embodiment are denoted by the same reference signs as in the first embodiment and will not be described.

Configuration of Upstream Extraction Circuit A1

FIG.11is a circuit diagram of the upstream extraction circuit A1in the fourth embodiment. The configuration of the upstream extraction circuit A1in the fourth embodiment is the same as the configuration of the upstream extraction circuit A1in the first embodiment except that the diode52is omitted.

FIG.12is a waveform diagram for describing operation of the upstream extraction circuit A1.FIG.12shows the waveform of the upstream node voltage, the waveform of the upstream voltage that passed through the first capacitor50, and the waveform of the upstream voltage that passed through the reduction circuit51. Time is shown on the horizontal axis of these waveforms. These waveforms are the same as those shown inFIG.4. The first capacitor50and the reduction circuit51operate similarly to the corresponding elements in the first embodiment. Therefore, the reduction circuit51reduces the peak value (absolute value) of the upstream voltage that passed through the first capacitor50. As a result, this prevents a voltage with a large absolute value from being applied to the microcomputer20. The reduction circuit51outputs the upstream voltage whose peak value was reduced to the microcomputer20.

Configuration of Downstream Extraction Circuit B1

As shown inFIG.11, the downstream extraction circuit B1has a configuration similar to that of the upstream extraction circuit A1. The upstream extraction circuit A1, the upstream node, the upstream node voltage, and the upstream voltage respectively correspond to the downstream extraction circuit B1, the downstream node, the downstream node voltage, and the downstream voltage.

Method for Detecting Blowout of Fuse F1

As described above, the diode52is omitted from both the upstream extraction circuit A1and the downstream extraction circuit B1. Therefore, when the upstream node voltage decreases, the upstream voltage also decreases. Similarly if the downstream node voltage decreases, the downstream voltage also decreases.

As mentioned in the description of the first embodiment, when the fuse F1is blown, the upstream voltage increases, and the downstream voltage decreases. Therefore, if the upstream voltage is greater than or equal to the upper threshold and furthermore the downstream voltage is below a certain lower threshold, the microcomputer20detects blowout of the fuse F1. The lower threshold is a negative value. As mentioned in the description of the first embodiment, the upper threshold is a positive value. The upper threshold thus is higher than the lower threshold. InFIG.12, the upper threshold and the lower threshold are indicated by Vp and Vn, respectively.

Determination of State of ECU11

FIG.13is a chart showing the relationship between states of the ECU11and output voltages of the upstream extraction circuit A1and the downstream extraction circuit B1. When the output voltages of the upstream extraction circuit A1and the downstream extraction circuit B1are both greater than or equal to the lower threshold Vn and furthermore below the upper threshold Vp, the microcomputer20determines that the state of the ECU11is a normal state. Similarly to the first embodiment, when the output voltages of the upstream extraction circuit A1and the downstream extraction circuit B1are both greater than or equal to the upper threshold Vp, or below the lower threshold Vn, the microcomputer20determines that the state of the ECU11is a normal state.

When the output voltage of the upstream extraction circuit A1is greater than or equal to the upper threshold Vp and furthermore the output voltage of the downstream extraction circuit B1is below the lower threshold Vn, the microcomputer20determines that the fuse F1is blown.

A first state is a state in which the output voltage of the upstream extraction circuit A1is greater than or equal to the lower threshold Vn and furthermore below the upper threshold Vp, and also the output voltage of the downstream extraction circuit B1is below the lower threshold Vn or greater than or equal to the upper threshold Vp. A second state is a state in which the output voltage of the upstream extraction circuit A1is below the lower threshold Vn or greater than or equal to the upper threshold Vp, and also the output voltage of the downstream extraction circuit B1is greater than or equal to the lower threshold Vn and below the upper threshold Vp. A third state is a state in which the output voltage of the upstream extraction circuit A1is below the lower threshold Vn and furthermore the output voltage of the downstream extraction circuit B1is greater than or equal to the upper threshold Vp.

As long as a failure has not occurred in the upstream extraction circuit A1or the downstream extraction circuit B1, the state of the ECU11will not transition to the first state, the second state, or the third state. Therefore, when the state of the ECU11is the first state, the second state, or the third state, the microcomputer20determines that a failure has occurred in the upstream extraction circuit A1or the downstream extraction circuit B1.

Operation of Microcomputer20

The microcomputer20executes blowout detection processing similarly to the first embodiment (seeFIG.7). In steps S3and S5of the blowout detection processing, the microcomputer20makes determinations according to the chart inFIG.13. Therefore, when the output voltage of the upstream extraction circuit A1is greater than or equal to the upper threshold Vp and furthermore the output voltage of the downstream extraction circuit B1is below the lower threshold Vn, the microcomputer20determines that the fuse F1is blown. The output voltage of the upstream extraction circuit A1is the upstream voltage that passed through the first capacitor50of the upstream extraction circuit A1, and is the upstream voltage whose peak value was reduced by the reduction circuit51of the upstream extraction circuit A1. The output voltage of the downstream extraction circuit B1is the downstream voltage that passed through the first capacitor50of the downstream extraction circuit B1, and is the downstream voltage whose peak value was reduced by the reduction circuit51of the downstream extraction circuit B1.

Effects of ECU11

The ECU11in the fourth embodiment has effects similar to those of the ECU11in the first embodiment.

Variations of Second and Third Embodiments

In the second embodiment, the upstream extraction circuit A1and the downstream extraction circuits B1, B2, . . . may each have a configuration in which the diode52is omitted, similarly to the fourth embodiment. In this case, the microcomputer20determines whether or not the fuse Fi is blown and whether or not a failure has occurred in the upstream extraction circuit A1or the downstream extraction circuit Bi in a manner similar to the fourth embodiment. In this case, the chart inFIG.13shows the relationship between states of the ECU11and output voltages of the upstream extraction circuit A1and the downstream extraction circuit Bi. InFIG.13, “blowout” indicates blowout of the fuse Fi. InFIG.13, “failure” indicates a failure in the upstream extraction circuit A1or the downstream extraction circuit Bi.

Similarly, in the third embodiment, the upstream extraction circuits A1, A2, . . . and the downstream extraction circuits B1, B2, . . . may each have a configuration in which the diode52is omitted, similarly to the fourth embodiment. In this case, the microcomputer20determines whether or not the fuse Fi is blown and whether or not a failure has occurred in the upstream extraction circuit Ai or the downstream extraction circuit Bi in a manner similar to the fourth embodiment. In this case, the chart inFIG.13shows the relationship between states of the ECU11and output voltages of the upstream extraction circuit Ai and the downstream extraction circuit Bi. InFIG.13, “blowout” indicates blowout of the fuse Fi. InFIG.13, “failure” indicates a failure in the upstream extraction circuit Ai or the downstream extraction circuit Bi.

Fifth Embodiment

In the first embodiment, the microcomputer20detects blowout of the fuse F1. However, a device different from the microcomputer20may detect blowout of the fuse F1.

The following description of a fifth embodiment focuses on differences from the first embodiment. Configurations other than those described below are the same as those of the first embodiment, and constituent elements that are the same as those of the first embodiment are denoted by the same reference signs as in the first embodiment and will not be described.

Configuration of Power Supply System1

FIG.14is a block diagram showing the main configuration of the power supply system1in the fifth embodiment. Similarly to the first embodiment, the ECU11in the fifth embodiment includes the microcomputer20, the upstream extraction circuit A1, the downstream extraction circuit B1, and the fuse F1. The ECU11in the fifth embodiment further includes a determination circuit J1. The upstream extraction circuit A1and the downstream extraction circuit B1are each connected to the determination circuit J1instead of the microcomputer20. The determination circuit J1is also connected to the microcomputer20.

Similarly to the first embodiment, the upstream extraction circuit A1extracts the AC component of the upstream node voltage, that is to say the upstream voltage, from the upstream node voltage. Similarly to the first embodiment, the downstream extraction circuit B1extracts the AC component of the downstream node voltage, that is to say the downstream voltage, from the downstream node voltage. The determination circuit J1determines whether or not the fuse F1is blown based on the upstream voltage and the downstream voltage respectively extracted by the upstream extraction circuit A1and the downstream extraction circuit B1. The determination circuit J1notifies the microcomputer20of the determination result. When the microcomputer20is notified that the fuse F1is blown, the microcomputer20transmits the blowout signal to a communication device via the communication line Lc.

Circuit Diagram of Upstream Extraction Circuit A1, Downstream Extraction Circuit B1, and Determination Circuit J1

FIG.15shows a circuit diagram of the upstream extraction circuit A1, the downstream extraction circuit B1, and the determination circuit J1. The upstream extraction circuit A1includes the first capacitor50, similarly to the first embodiment. One end of the first capacitor50of the upstream extraction circuit A1is connected to the upstream node of the fuse F1. The other end of the first capacitor50of the upstream extraction circuit A1is connected to the determination circuit J1. Similarly to the first embodiment, the first capacitor50of the upstream extraction circuit A1extracts the AC component of the upstream node voltage, that is to say the upstream voltage (seeFIG.5). The first capacitor50of the upstream extraction circuit A1outputs the extracted upstream voltage to the determination circuit J1. When the fuse F1is blown, the upstream voltage rises to a voltage greater than or equal to the upper threshold. As mentioned in the description of the first embodiment, the upper threshold is a positive value.

The downstream extraction circuit B1includes the first capacitor50, similarly to the first embodiment. One end of the first capacitor50of the downstream extraction circuit B1is connected to the downstream node of the fuse F1. The other end of the first capacitor50of the downstream extraction circuit B1is connected to the determination circuit J1. Similarly to the first embodiment, the first capacitor50of the downstream extraction circuit B1extracts the AC component of the downstream node voltage, that is to say the downstream voltage. The first capacitor50of the downstream extraction circuit B1outputs the extracted downstream voltage to the determination circuit J1. If the fuse F1is blown, the downstream voltage drops to a voltage below a certain lower threshold. Similarly to the fourth embodiment, the lower threshold is a negative value.

The determination circuit J1includes an input resistor70, a control resistor71, an upstream resistor72, a downstream resistor73, a limiting resistor74, and a circuit switch75. The circuit switch75is an NPN type bipolar transistor. The other end of the first capacitor50of the upstream extraction circuit A1is connected to one end of the input resistor70and the control resistor71. The other end of the input resistor70is grounded. The other end of the control resistor71is connected to the base of circuit switch75.

The collector of the circuit switch75is connected to one end of the upstream resistor72. A constant voltage Vc is applied to the other end of the upstream resistor72. The upstream resistor72functions as a first resistor. The constant voltage Vc has a positive value, and is generated by a regulator stepping down the power supply voltage of the DC power supply10, for example. The connection node between the upstream resistor72and the collector of the circuit switch75is connected to the microcomputer20. The emitter of the circuit switch75is connected to one end of the downstream resistor73. The other end of the downstream resistor73is grounded. The other end of the first capacitor50of the downstream extraction circuit B1is connected to one end of the limiting resistor74. The other end of the limiting resistor74is connected to the connection node between the downstream resistor73and the emitter of the circuit switch75.

The upstream voltage that passed through the first capacitor50of the upstream extraction circuit A1is applied across the input resistor70. The voltage across input resistor70is applied to the base of the circuit switch75. The downstream voltage that passed through the first capacitor50of the downstream extraction circuit B1is applied across the downstream resistor73via the limiting resistor74. The limiting resistor74limits the magnitude of the current flowing through the first capacitor50of the downstream extraction circuit B1.

Regarding the circuit switch75, when the voltage at the base, whose reference potential is the potential at the emitter, is greater than or equal to a certain ON voltage, the circuit switch75is on. When the circuit switch75is on, the resistance value between the collector and the emitter of the circuit switch75is sufficiently small. Therefore, current can flow through the collector and emitter of the circuit switch75.

Regarding the circuit switch75, if the voltage at the base, whose reference potential is the potential at the emitter, is below a certain OFF voltage, the circuit switch75is off. When the circuit switch75is off, the resistance value between the collector and the emitter of the circuit switch75is sufficiently large. Therefore, current does not flow through the collector and emitter of the circuit switch75. The ON voltage is greater than or equal to the OFF voltage. The ON voltage and the OFF voltage are positive values.

The voltage at the connection node between the upstream resistor72and the collector of the circuit switch75is output from the determination circuit J1to the microcomputer20. The reference potential of the output voltage of the determination circuit J1is the ground potential. When the circuit switch75is off, current does not flow through the upstream resistor72. Therefore, the constant voltage Vc is output from the determination circuit J1to the microcomputer20. When the circuit switch75is on, current flows through the upstream resistor72, the circuit switch75, and the downstream resistor73in this order. The path of current flowing through the upstream resistor72functions as a second current path. In the second current path, the circuit switch75is arranged downstream of the upstream resistor72. In the second current path, the downstream resistor73is arranged downstream of the circuit switch75. The downstream resistor73functions as a second resistor.

When the circuit switch75is on, the upstream resistor72and the downstream resistor73divide the constant voltage Vc. The divided voltage of the upstream resistor72and the downstream resistor73is output to the microcomputer20. The divided voltage is expressed as Vc·R73/(R72+R73), where R72and R73are respectively the resistance values of the upstream resistor72and the downstream resistor73. Here, “·” represents multiplication.

Since the constant voltage Vc and the resistance values R72and R73are constant values, the divided voltage is constant. Furthermore, since the resistance values R72and R73are positive values, the divided voltage is below the constant voltage Vc. A certain reference voltage is set in the microcomputer20. The reference voltage is greater than the divided voltage and less than or equal to the constant voltage Vc. A voltage that is greater than or equal to the reference voltage will be referred to as a high-level voltage. A voltage that is below the reference voltage will be referred to as a low-level voltage. Therefore, when the circuit switch75is off, a high-level voltage is output from the determination circuit J1to the microcomputer20. When the circuit switch75is on, a low-level voltage is output from the determination circuit J1to the microcomputer20.

Operation of Determination Circuit J1

FIG.16is a chart for describing operation of the determination circuit J1. As described above, when the fuse F1is blown, the upstream voltage increases to a voltage greater than or equal to the upper threshold Vp and furthermore the downstream voltage decreases to a voltage below the lower threshold Vn. The upstream voltage and the downstream voltage are the output voltages of the upstream extraction circuit A1and the downstream extraction circuit B1, respectively. As shown inFIG.16, when the output voltage of the upstream extraction circuit A1is greater than or equal to the upper threshold Vp and furthermore the output voltage of the downstream extraction circuit B1is below the lower threshold Vn, in the circuit switch75, the voltage at the base, whose reference potential is the potential at the emitter, is greater than or equal to the ON voltage. Therefore, the circuit switch75is on, and a low-level voltage is output from the determination circuit J1.

When the output voltages of the upstream extraction circuit A1and the downstream extraction circuit B1are both greater than or equal to the upper threshold Vp, or below the lower threshold Vn, in the circuit switch75, the voltage at the base, whose reference potential is the potential at the emitter, is a value that is near zero V and below the OFF voltage. In this case, regarding the circuit switch75, the voltage at the base, whose reference potential is the potential at the emitter, is below the OFF voltage. Therefore, the circuit switch75is off, and a high-level voltage is output from the determination circuit J1.

When the output voltage of the upstream extraction circuit A1is below the lower threshold Vn and furthermore the output voltage of the downstream extraction circuit B1is greater than or equal to the upper threshold Vp, in the circuit switch75, the voltage at the base, whose reference potential is the potential at the emitter, is a negative value and below the OFF voltage. Therefore, the circuit switch75is off, and a high-level voltage is output from the determination circuit J1.

As described above, the determination circuit J1determines whether or not the fuse F1is blown based on the output voltages of the upstream extraction circuit A1and the downstream extraction circuit B1. In the case of determining that the fuse F1is not blown, the determination circuit J1outputs a high-level voltage to the microcomputer20. In the case of determining that the fuse F1is blown, the determination circuit J1outputs a low-level voltage to the microcomputer20. The microcomputer20is thus notified of blowout of the fuse F1. In the fifth embodiment, the determination circuit J1functions as a determiner.

Effects of ECU11

The ECU11in the fifth embodiment exhibits effects similar to those of the ECU11in the first embodiment, except for the effect obtained by the microcomputer20detecting a blowout.

Sixth Embodiment

In the second embodiment, the microcomputer20detects blowout of a plurality of fuses F1, F2, and so on. However, a device different from the microcomputer20may detect blowout of the fuses F1, F2, and so on.

The following description of a sixth embodiment focuses on differences from the second embodiment. Configurations other than those described below are the same as those of the second embodiment, and constituent elements that are the same as those of the second embodiment are denoted by the same reference signs similarly to the second embodiment and will not be described.

Configuration of Power Supply System1

FIG.17is a block diagram showing the main configuration of the power supply system1in the sixth embodiment. Similarly to the second embodiment, the ECU11in the sixth embodiment includes the microcomputer20, the upstream extraction circuit A1, a plurality of downstream extraction circuits B1, B2, . . . , and a plurality of fuses F1, F2, and so on. The ECU11in the sixth embodiment further includes the determination circuit J1. The upstream extraction circuit A1and the downstream extraction circuits B1, B2, . . . are each connected to the determination circuit J1instead of the microcomputer20. The determination circuit J1is also connected to the microcomputer20.

The upstream extraction circuit A1has a configuration similar to that in the fifth embodiment. The downstream extraction circuit Bi has a configuration similar to that of the downstream extraction circuit Bi in the fifth embodiment. As mentioned in the description of the second embodiment, “i” is a natural number. One end of the first capacitor50of the downstream extraction circuit Bi is connected to the downstream node of the fuse Fi. The upstream extraction circuit A1outputs the AC component of the upstream node voltage, that is to say the upstream voltage, to the determination circuit J1. The downstream extraction circuit Bi outputs the AC component of the downstream node voltage of the fuse Fi, that is to say the downstream voltage of the fuse Fi, to the determination circuit J1.

he determination circuit J1determines whether or not at least one of the fuses F1, F2, . . . is blown based on the upstream voltage received from the upstream extraction circuit A1and the downstream voltages received from the downstream extraction circuits B1, B2, and so on. The determination circuit J1notifies the microcomputer20of the determination result. Upon receiving a notification that at least one of the fuses F1, F2, . . . is blown, the microcomputer20transmits a blowout signal indicating that at least one of the fuses F1, F2, . . . is blown to a communication device via the communication line Lc.

Circuit Diagram of Determination Circuit J1

FIG.18is a circuit diagram of the determination circuit J1. Similarly to the fifth embodiment, the determination circuit J1includes the input resistor70, the control resistor71, the upstream resistor72, the downstream resistor73, and the circuit switch75. The connections of these elements are similar to the connections described in the fifth embodiment. The constant voltage Vc is applied to the upstream end of the upstream resistor72. The connection node between the upstream resistor72and the collector of the circuit switch75is connected to the microcomputer20. The downstream end of the downstream resistor73is grounded.

The determination circuit J1in the sixth embodiment further includes a plurality of limiting resistors74. As described above, one end of the first capacitor50of the downstream extraction circuit Bi is connected to the downstream node of the fuse Fi. The other end of each of the first capacitors50of the downstream extraction circuits B1, B2, . . . is connected to one end of the corresponding limiting resistor74. Similarly to the fifth embodiment, the other end of each of the limiting resistors74is connected to the connection node between the downstream resistor73and the emitter of the circuit switch75.

When none of the fuses F1, F2, . . . is blown, in the circuit switch75, the voltage at the base, whose reference potential is the potential at the emitter, is below the OFF voltage. At this time, the circuit switch75is off. When the circuit switch75is off, the determination circuit J1outputs a high-level voltage.

When at least one of the fuses F1, F2, . . . is blown, the output voltage of the upstream extraction circuit A1increases to a voltage greater than or equal to the upper threshold. Furthermore, the output voltage of at least one of the downstream extraction circuits B1, B2, . . . decreases to a voltage below the lower threshold. At this time, the circuit switch75is turned on, and a low-level voltage is output from the determination circuit J1. The output voltage of the upstream extraction circuit A1is the upstream voltage. The output voltage of the downstream extraction circuit Bi is the downstream voltage of the fuse Fi.

As described above, the determination circuit J1determines whether or not at least one of the fuses F1, F2, . . . is blown based on the output voltages of the upstream extraction circuit A1, and the downstream extraction circuits B1, B2, and so on. In the case of determining that none of the fuses F1, F2, . . . are blown, the determination circuit J1outputs a high-level voltage to the microcomputer20. In the case of determining that at least one of the fuses F1, F2, . . . is blown, the determination circuit J1outputs a low-level voltage to the microcomputer20. The microcomputer20is thus notified that at least one of the fuses F1, F2, . . . is blown. In the sixth embodiment as well, the determination circuit J1functions as a determiner.

Effects of ECU11

The ECU11in the sixth embodiment achieves effects similar to those of the ECU11in the second embodiment, except for the effect obtained by the microcomputer20detecting a blowout.

Seventh Embodiment

In the third embodiment, the microcomputer20detects blowout of the fuse Fi. However, a device different from the microcomputer20may detect blowout of the fuse Fi. As mentioned in the description of the second embodiment, “i” is a natural number.

The following description of a seventh embodiment focuses on differences from the third embodiment. Configurations other than those described below are the same as those of the third embodiment, and constituent elements that are the same as those of the third embodiment are denoted by the same reference signs as in the third embodiment and will not be described.

Configuration of Power Supply System1

FIG.19is a block diagram showing the main configuration of the power supply system1in the seventh embodiment. Similarly to the third embodiment, the ECU11in the seventh embodiment includes the microcomputer20, a plurality of upstream extraction circuits A1, A2, . . . , a plurality of downstream extraction circuits B1, B2, . . . , and a plurality of the fuses F1, F2, and so on. The ECU11in the seventh embodiment further includes a plurality of determination circuits J1, J2, and so on. The upstream extraction circuit Ai and the downstream extraction circuit Bi are each connected to the determination circuit Ji instead of the microcomputer20. The determination circuit Ji is also connected to the microcomputer20.

The upstream extraction circuit Ai has a configuration similar to that of the upstream extraction circuit A1in the fifth embodiment. The downstream extraction circuit Bi has a configuration similar to that of the downstream extraction circuit B1in the fifth embodiment. One end of the first capacitor50of the upstream extraction circuit Ai is connected to the upstream node of the fuse Fi. One end of the first capacitor50of the downstream extraction circuit Bi is connected to the downstream node of the fuse Fi. The upstream extraction circuit Ai outputs the AC component of the upstream node voltage of the fuse Fi, that is to say the upstream voltage of the fuse Fi, to the determination circuit Ji. The downstream extraction circuit Bi outputs the AC component of the downstream node voltage of the fuse Fi, that is to say the downstream voltage of the fuse Fi, to the determination circuit Ji.

The determination circuit Ji has a configuration similar to that of the determination circuit J1in the fifth embodiment, and determines whether or not the fuse Fi is blown based on the output voltages of the upstream extraction circuit Ai and the downstream extraction circuit Bi. In the case of determining that the fuse Fi is not blown, the determination circuit Ji outputs a high-level voltage to the microcomputer20. In the case of determining that the fuse Fi is blown, the determination circuit Ji outputs a low-level voltage to the microcomputer20. The microcomputer20is thus notified of blowout of the fuse Fi. In the seventh embodiment, the determination circuit Ji functions as a determiner.

Effects of ECU11

The ECU11in the seventh embodiment exhibits effects similar to those of the ECU11in the third embodiment, except for the effect obtained by the microcomputer20detecting a blowout.

Variations of Fifth to Seventh Embodiments

In the fifth embodiment, the upstream extraction circuit A1and the downstream extraction circuit B1may have configurations similar to those of the upstream extraction circuit A1and the downstream extraction circuit B1in the first embodiment or the fourth embodiment. In the sixth embodiment, the upstream extraction circuit A1and the downstream extraction circuit Bi may have configurations similar to those of the upstream extraction circuit A1and the downstream extraction circuit B1in the first embodiment or the fourth embodiment. In the seventh embodiment, the upstream extraction circuit Ai and the downstream extraction circuit Bi may have configurations similar to those of the upstream extraction circuit A1and the downstream extraction circuit B1in the first embodiment or the fourth embodiment.

In the fifth and sixth embodiments, the circuit switch75of the determination circuit J1is not limited to being an NPN type bipolar transistor, and may also be an N-channel type FET (Field Effect Transistor) or an IGBT (Insulated Gate Bipolar Transistor), for example. In the seventh embodiment, the circuit switch75of the determination circuit Ji is not limited to being an NPN bipolar transistor, and may be an N-channel FET, an IGBT, or the like.

Eighth Embodiment

In the first embodiment, the reduction circuit51is not limited to being a circuit that includes the second circuit resistor60.

The following description of an eighth embodiment focuses on differences from the first embodiment. Configurations other than those described below are the same as those of the first embodiment, and constituent elements that are the same as those of the first embodiment are denoted by the same reference signs as in the first embodiment and will not be described.

Configuration of Upstream Extraction Circuit A1

FIG.20is a circuit diagram of the upstream extraction circuit A1in the eighth embodiment. Similarly to the first embodiment, the upstream extraction circuit A1in the eighth embodiment includes the first capacitor50, the reduction circuit51, and the first circuit resistor53. The reduction circuit51in the eighth embodiment includes the second capacitor61and a first Zener diode62.

One end of the first capacitor50is connected to the upstream node of the fuse F1. In the reduction circuit51, the other end of the first capacitor50is connected to the microcomputer20, one end of the first circuit resistor53, one end of the second capacitor61, and the cathode of the first Zener diode62. The other end of the first circuit resistor53, the other end of the second capacitor61, and the anode of the first Zener diode62are grounded.

FIG.21is a waveform diagram for describing operation of the upstream extraction circuit A1.FIG.21shows the waveform of the upstream node voltage, the waveform of the upstream voltage that passed through the first capacitor50, and the waveform of the upstream voltage that passed through the reduction circuit51. Time is shown on the horizontal axis of these waveforms. Similarly to the first embodiment, the first capacitor50extracts the AC component of the upstream node voltage, that is to say the upstream voltage. The upstream voltage that passed through the first capacitor50is applied across the second capacitor61of the reduction circuit51. The second capacitor61smoothes the voltage applied thereto via the second circuit resistor60.

In the first Zener diode62of the reduction circuit51, when the voltage at the cathode, whose reference potential is the ground potential, reaches a certain breakdown voltage, current flows through the cathode and the anode in this order. This prevents the upstream voltage from exceeding the breakdown voltage. The breakdown voltage is greater than or equal to the upper threshold Vp. Also, the first Zener diode62operates similarly to the diode52in the first embodiment. The upstream voltage is thus prevented from dropping to a voltage below a predetermined voltage. The upstream voltage whose peak value was reduced by the reduction circuit51is applied across the first circuit resistor53. The upstream voltage applied across the first circuit resistor53is output to the microcomputer20. Due to the operation of the first Zener diode62of the reduction circuit51, the voltage input to the microcomputer20falls within an allowable range. In the eighth embodiment, the first Zener diode62of the upstream extraction circuit A1functions as the upstream diode.

Configuration of Downstream Extraction Circuit B1

As shown inFIG.20, the downstream extraction circuit B1has a configuration similar to that of the upstream extraction circuit A1. In the description of the configuration of the upstream extraction circuit A1, replace the upstream extraction circuit A1, the upstream node voltage, and the upstream voltage respectively with the downstream extraction circuit B1, the downstream node voltage, and the downstream voltage. This therefore obtains a description of the configuration of the downstream extraction circuit B1. In the eighth embodiment, the first Zener diode62of the downstream extraction circuit B1functions as the downstream diode.

Effects of ECU11

The ECU11in the eighth embodiment achieves effects similar to those of the ECU11in the first embodiment.

Variations of Second and Third Embodiments

The upstream extraction circuit A1and the downstream extraction circuit B1in the second embodiment may have configurations similar to those of the upstream extraction circuit A1and the downstream extraction circuit B1in the eighth embodiment. The upstream extraction circuit A1and the downstream extraction circuit Bi in the third embodiment may have configurations similar to those of the upstream extraction circuit A1and the downstream extraction circuit B1in the eighth embodiment.

Ninth Embodiment

In the fourth embodiment, the reduction circuit51is not limited to being a circuit that includes the second circuit resistor60.

The following description of a ninth embodiment focuses on differences from the fourth embodiment. Configurations other than those described below are the same as those of the fourth embodiment, and constituent elements that are the same as those of the fourth embodiment are denoted by the same reference signs similarly to the fourth embodiment and will not be described.

Configuration of Upstream Extraction Circuit A1

FIG.22is a circuit diagram of the upstream extraction circuit A1in the ninth embodiment. The upstream extraction circuit A1in the ninth embodiment has constituent elements similar to those of the upstream extraction circuit A1in the eighth embodiment. The connections of these elements are similar to the connections described in the eighth embodiment. The upstream extraction circuit A1in the eighth embodiment further includes a second Zener diode63. The anode of the second Zener diode63is connected to the anode of the first Zener diode62. The cathode of the second Zener diode63is grounded.

FIG.23is a waveform diagram for describing operation of the upstream extraction circuit A1.FIG.21shows the waveform of the upstream node voltage, the waveform of the upstream voltage that passed through the first capacitor50, and the waveform of the upstream voltage that passed through the reduction circuit51. Time is shown on the horizontal axis of these waveforms. Similarly to the first embodiment, the first capacitor50extracts the AC component of the upstream node voltage, that is to say the upstream voltage. The upstream voltage that passed through the first capacitor50is applied across the second capacitor61of the reduction circuit51. The second capacitor61smoothes the voltage applied thereto via the second circuit resistor60.

Hereinafter, a circuit in which the first Zener diode62and the second Zener diode63are connected in series will be referred to as a diode circuit. In the diode circuit, when the upstream voltage rises to a certain first voltage that is a positive value, current flows through the diode circuit, and the upstream voltage does not exceed a first voltage. The first voltage is greater than or equal to the upper threshold Vp. In the diode circuit, when the upstream voltage decreases to a certain second voltage that is a negative value, current flows through the diode circuit, and the upstream voltage does not decrease to a voltage below the second voltage. The second voltage is below the lower threshold Vn.

The upstream voltage whose peak value was reduced by the reduction circuit51is applied across the first circuit resistor53. The upstream voltage applied across the first circuit resistor53is output to the microcomputer20. Due to the operation of the first Zener diode62of the reduction circuit51, the voltage input to the microcomputer20falls within an allowable range.

Configuration of Downstream Extraction Circuit B1

As shown inFIG.22, the downstream extraction circuit B1has a configuration similar to that of the upstream extraction circuit A1. In the description of the configuration of the upstream extraction circuit A1, replace the upstream extraction circuit A1, the upstream node voltage, and the upstream voltage respectively with the downstream extraction circuit B1, the downstream node voltage, and the downstream voltage. This therefore obtains a description of the configuration of the downstream extraction circuit B1.

Effects of ECU11

The ECU11in the ninth embodiment has effects similar to those of the ECU11in the fourth embodiment.

Variation of Ninth Embodiment

The diode circuit may be a circuit in which the cathode of the first Zener diode62is connected to the cathode of the second Zener diode63. In this case, the anode of the first Zener diode62is connected to the other end of the first capacitor50. The anode of the second Zener diode63is grounded. Also, in the reduction circuit51, a suppressor, a varistor, or the like may be used instead of the diode circuit. These elements operate similarly to the diode circuit.

Variations of Fourth to Seventh Embodiments

In the fourth and fifth embodiments, the upstream extraction circuit A1and the downstream extraction circuit B1may have configurations similar to those of the upstream extraction circuit A1and the downstream extraction circuit B1in the ninth embodiment. In the sixth embodiment, the upstream extraction circuit A1and the downstream extraction circuit Bi may have configurations similar to those of the upstream extraction circuit A1and the downstream extraction circuit B1in the ninth embodiment. In the seventh embodiment, the upstream extraction circuit Ai and the downstream extraction circuit Bi may have configurations similar to those of the upstream extraction circuit A1and the downstream extraction circuit B1in the ninth embodiment.

Variations of First to Ninth Embodiments

In the first to ninth embodiments, one or more upstream extraction circuits and one or more downstream extraction circuits may output the output voltage to a multiplexer. In this case, the multiplexer notifies the microcomputer20of the output voltage of one or more upstream extraction circuits and the output voltage of one or more downstream extraction circuits by transmitting data to the microcomputer20via one communication line. Furthermore, the member in which a surge is generated is not limited to being an upstream conducting wire or a downstream conducting wire. If the load includes an inductor, a surge may be generated in the inductor of the load. While the DC power supply10is supplying power to an electrical device that includes an inductor, a surge may be generated in the inductor of the electrical device.

Technical features (constituent elements) described in the first to ninth embodiments can be combined with each other, and new technical features can be formed by such combinations.

The first to ninth embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present disclosure is indicated by the scope of the claims, not the meaning described above, and is intended to include meanings equivalent to the scope of the claims and all changes within the scope of the claims.