WO2018047288A1 - Vehicle power supply system and method for controlling vehicle power supply system - Google Patents

Abstract

According to an embodiment of the present invention, a vehicle power supply system reduces, by means of a DC-DC converter, the voltage of a power supply that supplies a motor with power, said motor driving a vehicle, and supplies a battery with power. The vehicle power supply system is characterized by being provided with: a rectifying circuit, which is provided to the DC-DC converter, and is a circuit that rectifies, to a direct current, the power to be supplied to the battery by the DC-DC converter, and in which at least a part between a rectifying element and outside is connected via a fusing member; and a switch unit, which is provided between the rectifying circuit and the battery, detects a reverse current flowing from the battery to the DC-DC converter, and switches, corresponding to the reverse current, the state of a switch from the on-state to the off-state, said switch being connected between the battery and the rectifying circuit.

Description

Vehicle power supply system and control method for vehicle power supply system

The present invention relates to a vehicle power supply system and a control method for the vehicle power supply system.

In an electric vehicle, there is a DC-DC converter that steps down the voltage of a high-voltage side battery for driving a motor and charges the low-voltage side battery for supplying power to electrical components. There is a vehicle power supply system equipped with a transistor for protecting the DC-DC converter and a control circuit for controlling the transistor (for example, Patent Documents 1 and 2).

Japanese Unexamined Patent Publication No. 2007-82374 Japanese Unexamined Patent Publication No. 2010-233284

However, in the prior art, the protection of the DC-DC converter when a large backflow current flows through the rectifying element of the secondary rectifier circuit constituting the DC-DC converter, or the secondary side constituting the DC-DC converter. In order to protect parts such as vehicle body wiring including the rectifying element when a small backflow current continuously flows through the rectifying element of the rectifying circuit, the transistor and the transistor are controlled by the DC-DC converter. It is necessary to mount a control circuit for monitoring the transistor and the like. Therefore, the DC-DC converter is enlarged and cannot be made inexpensive. The present application relates to a vehicle power supply system and a vehicle power supply capable of protecting a large-current or small-current backflow current and making the DC-DC converter larger and less expensive than conventional ones. An object of the present invention is to provide a system control method.

In order to solve the above-described problem, an aspect of the present invention provides a vehicle power supply system in which a voltage of a power supply that supplies power to a motor that drives a vehicle is stepped down by a DC-DC converter to supply power to the battery. A circuit provided in the DC-DC converter for rectifying the power supplied to the battery by the DC-DC converter into a direct current, wherein at least a part between the rectifying element and the outside is connected via a fusing member A rectifier circuit that is provided between the rectifier circuit and the battery, detects a reverse current flowing from the battery to the DC-DC converter, and detects the reverse current and the battery and the rectifier circuit. And a switch unit that switches a switch connected between the switch and the switch to an OFF state. It is a stem.

Further, one aspect of the present invention is the above-described vehicle power supply system, wherein the fusing member is based on a first reference value that is a value of the backflow current that is a determination reference for turning the switch from an on state to an off state. Is blown when the second reference value, which is a large value, is exceeded.

One aspect of the present invention is the above-described vehicle power supply system, in which the switch unit is configured to switch the switch when the backflow current exceeds the first reference value for a predetermined delay time. Is turned from an on state to an off state.

Further, one aspect of the present invention is the above-described vehicle power supply system, wherein the fusing member is blown in a time shorter than the predetermined delay time.

One aspect of the present invention is the above-described vehicle power supply system, wherein the first reference value, the predetermined delay time, and the current value flowing through the fusing member and the current value in the fusing member are: The fusing characteristics indicating the fusing time until the fusing member blows when flowing through the fusing member is determined according to the component rating of the part through which the reverse current flows, including the rectifying element. And

Further, one aspect of the present invention is the above-described vehicle power supply system, wherein the fusing member has a number and a cross-sectional area set according to the second reference value.

Another aspect of the present invention is a control method for a vehicle power supply system that supplies power to a battery by stepping down a voltage of a power supply that supplies power to a motor that drives the vehicle, using a DC-DC converter. The DC-DC converter has a rectifier circuit in which at least a part between the rectifier element and the outside is connected via a fusing member, and a switch unit provided between the rectifier circuit and the battery, A vehicle power supply system characterized in that a switch connected between the battery and the rectifier circuit is changed from an on state to an off state in response to a reverse current flowing from the battery to the DC-DC converter. It is a control method.

According to the present invention, a vehicular power supply system that can protect a large-current or small-current backflow current and that does not make the DC-DC converter larger and less expensive than the conventional one, and a vehicle A method for controlling a power supply system for a vehicle can be provided.

It is a figure showing an example of composition of a power supply system for vehicles concerning an embodiment of the present invention. FIG. 2 is a block diagram illustrating a configuration example of an ON / OFF circuit 32 illustrated in FIG. 1. It is a characteristic view for demonstrating the operation example of the vehicle power supply system 1 shown in FIG. It is a figure for demonstrating the operation example of the switch part 3 shown in FIG.

<First Embodiment>
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram illustrating a configuration example of a vehicle power supply system 1 according to a first embodiment of the present invention. A vehicle power supply system 1 shown in FIG. 1 is mounted on an electric vehicle such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, or a hydrogen fuel cell vehicle. The vehicle power supply system 1 includes a DC-DC converter 2 and a switch unit 3. The vehicle power supply system 1 is a system that supplies power to the battery 5 and the like by stepping down the voltage of the power supply 4 that supplies power to the motor 61 that drives the vehicle by the DC-DC converter 2. The battery 5 is a power storage device having a rated voltage lower than the rated voltage of the power source 4, and is connected to an electrical load 9 such as an electrical component via a fuse 8.

The power source 4 is a direct current power source, for example, a high voltage battery having a rated voltage higher than the rated voltage of the battery 5. The positive electrode of the power supply 4 is connected to the input terminal 25 of the DC-DC converter 2, and the negative electrode of the power supply 4 is connected to the input terminal 26 of the DC-DC converter 2. The power source 4 is not limited to a high voltage battery, and may be a power source such as a capacitor, a hydrogen fuel cell, or a generator, or a combination of a plurality of types of power sources. In the example shown in FIG. 1, a motor 61 is connected to the power supply 4 via the control device 6. The motor 61 is an electric motor and is a drive source of a vehicle on which the vehicle power supply system 1 is mounted. The motor 61 is driven and controlled by the control device 6 using the power supply 4 as a power source. There may be a plurality of motors 61, or the motor 61 may be driven in cooperation with an engine such as an internal combustion engine (not shown) mounted on the vehicle.

The DC-DC converter (DC-DC converter) 2 steps down the DC voltage of the power supply 4 input between the input terminal 25 and the input terminal 26 and outputs it from between the output terminal 27 and the output terminal 28. In FIG. 1, illustration of a voltage detection unit, a part of current detection unit, a control line, and the like provided in the DC-DC converter 2 is omitted. The DC-DC converter 2 includes an inverter circuit 21, a transformer T, a rectifier circuit 22, a DC-DC converter control unit 24, a coil L, and a capacitor Cout. In this example, the DC-DC converter 2 is an insulation type using a transformer T, and has a synchronous rectification type configuration in which the rectifier element of the rectifier circuit 22 is configured by a transistor.

The inverter circuit 21 includes four transistors Q1 to Q4 made of, for example, n-channel MOSFETs (metal oxide semiconductor field effect transistors). The transistors Q1 to Q4 are bridge-connected and controlled by the DC-DC converter control unit 24. The DC power input from between the input terminal 25 and the input terminal 26 is converted into AC power to the primary coil 201 of the transformer T. Output. A current transformer CT is connected in series to the primary coil 201.

The secondary coil of the transformer T is composed of a secondary coil 202 and a secondary coil 203 connected in series. The connection end of the secondary coil 202 and the secondary coil 203 is connected to one end of the coil L. The other end of the secondary coil 202 is connected to a metal electrode (bonding pad) 221 in the rectifier circuit 22. The other end of the secondary coil 203 is connected to the metal electrode 222 in the rectifier circuit 22.

The rectifier circuit 22 is a circuit that rectifies the power supplied from the DC-DC converter 2 to the battery 5 into a direct current, and is configured on a substrate such as an insulating metal substrate. The rectifier circuit 22 includes two transistors Q5 and Q6 made of, for example, n-channel MOSFETs. The transistors Q5 and Q6 are on / off controlled by the DC-DC converter control unit 24 in synchronization with the on / off operation of the primary transistors Q1 to Q4, and the AC power output from the secondary side of the transformer T is supplied to the transistors Q5 and Q6. Rectify to DC power. Transistors Q5 and Q6 are one configuration example of the rectifying element.

The transistor Q5 and the transistor Q6 are bare chips that are not molded, and are bonded to, for example, a substrate constituting the rectifier circuit 22. The metal electrodes (bonding pads) 231 to 236 on the chips constituting the transistors Q5 and Q6 and the metal electrodes 221 to 224 on the substrate are bonded by bonding wires 225 to 228 which are fusing members. Yes. The transistors Q5 and Q6 in the bonding connection are hermetically sealed with a sealing material such as silicone gel. The bonding wires 225 to 228 or a part of the bonding wires 225 to 228 have a fusing characteristic that blows when a predetermined current is applied for a predetermined time. The bonding wires 225 to 228 may be composed of a single thin line or a plurality of thin lines. The fusing characteristics of the transistor Q5 may be the same or different for both the bonding wire 225 and the bonding wire 226. Similarly, for transistor Q6, the fusing characteristics of bonding wire 227 and bonding wire 228 may be the same or different. This fusing characteristic will be described later. The rectifier circuit 22 of the present embodiment is provided in the DC-DC converter 2 and is a circuit that rectifies the power supplied from the DC-DC converter 2 to the battery 5 into a direct current, and includes a transistor Q5 and a transistor that are rectifier elements. At least a part between Q6 and the outside of the rectifier circuit 22 is connected via bonding wires 225 to 228 which are fusing members. Here, the outside of the rectifier circuit 22 means a circuit outside the rectifier circuit 22, an external element, or an external wiring.

The metal electrode 231 on the chip connected to the drain of the transistor Q5 is connected to the metal electrode 221 on the substrate via the bonding wire 225. The metal electrode 232 on the chip connected to the source of the transistor Q5 is connected to the metal electrode 223 on the substrate via a bonding wire 226. The metal electrode 233 on the chip connected to the gate of the transistor Q5 is connected to a metal electrode on the substrate (not shown) via a bonding wire (not shown).

The metal electrode 234 on the chip connected to the drain of the transistor Q6 is connected to the metal electrode 222 on the substrate via the bonding wire 227. The metal electrode 235 on the chip connected to the source of the transistor Q6 is connected to the metal electrode 224 on the substrate through the bonding wire 228. The metal electrode 236 on the chip connected to the gate of the transistor Q6 is connected to the metal electrode on the substrate (not shown) via a bonding wire (not shown).

On the other hand, the other end of the coil L is connected to one end of the capacitor Cout and the output terminal 27. The other end of the capacitor Cout is connected to the metal electrode 223 and the metal electrode 224 via the wiring patterns P1 and P2 and to the output terminal 28. The coil L and the capacitor Cout constitute a smoothing circuit.

On the other hand, the switch unit 3 includes a switch 31, an ON / OFF circuit 32, a diode 33, and a current detection unit 34. The switch unit 3 is provided between the rectifier circuit 22 in the DC-DC converter 2 and the battery 5, and when a reverse current Io flowing from the battery 5 to the DC-DC converter 2 is detected, the reverse current In accordance with Io, the switch 31 connected between the battery 5 and the rectifier circuit 22 is switched from the on state to the off state, thereby blocking the reverse current Io. The input terminal 35 of the switch unit 3 is connected to one terminal of the switch 31, and the other terminal of the switch 31 is connected to the anode of the diode 33, and the output of the switch unit 3 through (or via) the current detection unit 34. The terminal 37 is connected. The input terminal 35 is connected to the output terminal 27 of the DC-DC converter 2, and the output terminal 37 is connected to the positive electrode of the battery 5 via the fuse 7. The input terminal 36 of the switch 31 is connected to the output terminal 28 of the DC-DC converter 2, the power supply terminal (negative power supply terminal) of the ON / OFF circuit 32, the output terminal 38 of the switch unit 3, and the negative electrode of the battery 5. Yes.

The switch 31 is a relay having a make contact, and the switch 31 is turned on when a direct current is supplied from the battery 5 via a diode 33 and an ON / OFF circuit 32 to a coil (not shown) of the relay. . When the coil of the relay constituting the switch 31 is not energized, the switch 31 is turned off. In this configuration, for example, when the battery 5 is reversely connected, the diode 33 is in the reverse direction, so that the switch 31 is turned off. When the battery 5 is connected in the forward direction, the switch 31 is controlled to be turned on or off by the ON / OFF circuit 32 according to the detection result of the current detector 34.

The ON / OFF circuit 32 controls the switch 31 to be on or off according to the detection result of the current detector 34.

The diode 33 has an anode connected to the output terminal 37 and a cathode connected to the power supply terminal (positive power supply terminal) of the ON / OFF circuit 32. When the battery 5 is connected in the forward direction, the diode 33 inputs DC power supplied from the battery 5 to the ON / OFF circuit 32 and to the coil of the switch 31 via the ON / OFF circuit 32. To do.

The current detection unit 34 includes a current detector such as a current transformer or a shunt resistor, and detects the generation of the reverse current Io flowing from the output terminal 37 toward the switch 31 and turns the detection result ON. / OFF circuit 32 to output. The current detection unit 34 only needs to have at least performance capable of detecting whether or not a predetermined (eg, several A or more) backflow current Io is generated. However, the current detection unit 34 has, for example, the performance of changing the output signal according to the magnitude of the current and the performance of detecting whether or not a short-circuit current (large current) is generated from the battery 5. Also good.

The fuse 7 is a large-capacity current fuse, and the rated current is, for example, about several tens to several hundreds A. The rated current of the fuse 7 can be determined according to the rated current of the DC-DC converter 2, for example. For example, the fuse 7 is blown when the output terminal 27 and the output terminal 28 of the DC-DC converter 2 are short-circuited due to a failure or the like and a short-circuit current is output from the battery 5 to protect components such as wiring. It is provided for.

On the other hand, the fuse 8 is a small-capacity current fuse, and its rated current is about several A to several tens A. The rated current of the fuse 8 can be determined according to the rated current of the electric load 9 and the like. The fuse 8 is provided, for example, when the electrical load 9 is short-circuited due to a failure or the like and a short-circuit current is generated from the battery 5 to protect the wiring and the like by fusing. Note that a plurality of fuses 8 may be connected in parallel, and one or a plurality of electric loads 9 may be connected to each fuse 8.

Next, a configuration example of the switch unit 3 will be described with reference to FIG. In FIG. 2, the same components as those shown in FIG.

In the configuration example shown in FIG. 2, the switch 31 includes a make contact 311 and a coil 312. The make contact 311 switches between the input terminal 35 and the output terminal 37 to an on state or an off state. The make contact 311 is turned on when a predetermined current is supplied to the coil 312 and turned off when no current is supplied. When the drive unit 326 is turned on, the coil 312 passes a current corresponding to the output voltage of the battery 5 (or controlled to a predetermined value by the drive unit 326) from the battery 5 shown in FIG.

2, the ON / OFF circuit 32 includes a power supply unit 321, an input unit 322, a determination unit 323, a delay unit 324, a blocking unit 325, and a drive unit 326. The power supply unit 321 supplies direct current power supplied from the battery 5 via the diode 33 as it is, or by converting voltage to supply power to each unit. The input unit 322 inputs the output signal of the current detection unit 34, and outputs a signal resulting from performing signal processing such as amplification, current-voltage conversion, smoothing on the input signal. Based on the output signal of the input unit 322, the determination unit 323 determines whether or not the current detection unit 34 has detected a backflow current Io having a magnitude greater than or equal to a predetermined reference value, and outputs a signal indicating the determination result. . When a signal indicating that a backflow current Io having a magnitude equal to or larger than a predetermined reference value is input from the determination unit 323, the delay unit 324 delays the signal for a predetermined time and outputs the delayed signal. The blocking unit 325 blocks the energization of the coil 312 by the driving unit 326 when the delay unit 324 outputs a predetermined signal. That is, the blocking unit 325 controls the driving unit 326 to be turned off when the delay unit 324 outputs a predetermined signal.

The drive unit 326 is turned on when electric power is supplied from the power supply unit 321, and supplies a predetermined current to the coil 312. In addition, when a control signal for instructing an off state is input from the blocking unit 325, the driving unit 326 enters an off state and stops energization of the coil 312. Note that once the drive unit 326 is turned off by the blocking unit 325, the control of the off state is continued regardless of the presence or absence of the signal output of the delay unit 324. This OFF state is continued until, for example, a predetermined release signal (not shown) is input or the supply of power from the power supply unit 321 is stopped. The drive unit 326 includes, for example, a transistor provided on the high side or the low side of the coil 312 so as to be in series with the diode 33, a drive circuit for the transistor, a flip-flop circuit for continuing the OFF state, and the like. It is configured.

Next, an example of setting the fusing characteristics of the bonding wires 225, 227 and the like as fusing members and the operating characteristics of the switch unit 3 will be described with reference to FIG. In FIG. 3, the horizontal axis represents the magnitude of the backflow current Io shown in FIG. 1, and the unit is arbitrary. The vertical axis is time, and the unit is second.

Characteristic B indicates the rated value of the part. Here, the component means a component through which a reverse current Io including a rectifying element, wiring, a fuse, and the like flows. At a certain current value, if the energization time of the backflow current Io is shorter than the time indicated by the characteristic B corresponding to the current value, the component can operate safely.

On the other hand, a region A indicated by shading is a region corresponding to the magnitude and duration of the current at which the switch 31 is turned off. The magnitude of the current is set according to the determination reference value of the determination unit 323. The duration time is set by the delay time of the delay unit 324. In the example shown in FIG. 3, the region A can be adjusted in the left-right direction indicated by the arrow A1 by changing the determination reference value of the magnitude of the backflow current Io by the determination unit 323. The value of the backflow current Io, which is a criterion for determining the switch 31 from the on state to the off state, is defined as a first reference value. In the example shown in FIG. 3, the switch 31 is turned off when the backflow current Io equal to or greater than the first reference value continues for 1 second or more. Further, by changing the delay time of the delay unit 324, the region A can be adjusted in the vertical direction indicated by the arrow A2. In the example shown in FIG. 3, the delay time of the delay unit 324 is set to 1 second.

The characteristics C1 and C2 are fusing characteristics of the bonding wires 225 to 228. For example, the characteristic C1 has the same cross-sectional area (or wire diameter) of the bonding wire as the characteristic C2 and the number is smaller than that of the characteristic C2, or the number of bonding wires is the same as the characteristic C2 and the cross-sectional area is the characteristic C2. It is a characteristic when it is small. The characteristic C2 is, for example, a characteristic when the cross-sectional area of the bonding wire is the same as the characteristic C1 and the number is larger than the characteristic C1, or the number of bonding wires is the same as the characteristic C1 and the cross-sectional area is larger than the characteristic C1. The fusing characteristics of the bonding wire can be adjusted by the number of bonding wires and the cross-sectional area (or wire diameter) as indicated by an arrow C. In addition, when making a bonding wire into a some thin wire, the cross-sectional area of a some fine wire may be the same, and may differ. In addition, the configuration (number and cross-sectional area) of the bonding wire 225 and the configuration (number and cross-sectional area) of the bonding wire 226 shown in FIG. The fusing characteristics can be adjusted by changing the configuration (number and cross-sectional area).

For example, when the fusing characteristic of the bonding wire is set to the characteristic C1, when the value of the backflow current Io exceeds the second reference value that is the value of the backflow current Io at the point where the curve of the characteristic C1 deviates from the region A, the delay The bonding wire is melted in a time shorter than the delay time (1 second) set in the part 324, and the backflow current Io is cut off. The fusing time in this case varies depending on the characteristic C1 depending on the magnitude of the backflow current Io. For example, assuming that the maximum output current of the battery 5 has a characteristic indicated by a broken line, the reverse current Io is blocked by the switch unit 3 indicated by the region A and the reverse current Io is interrupted by a bonding wire (melting member) indicated by the characteristic C1. By combining them, the backflow current Io can be cut off within the rated region indicated by the characteristic B. Even if the fusing characteristic of the bonding wire is the characteristic C2, the characteristic C2 is a curve that passes through the intersection of the characteristic B and the maximum output current of the battery. The reverse current Io can be interrupted within the rated region indicated by the characteristic B by combining the interruption of the reverse current Io by the bonding wire (melting member) indicated by the characteristic C2. In addition, the number and cross-sectional area of a bonding wire (melting member) can be set according to a 2nd reference value.

Further, as shown in FIG. 3, according to the magnitude of the backflow current Io, the parts are protected by bonding wire when the backflow current Io is relatively large, and the parts of the backflow current Io are relatively small. The following effects can be obtained by performing protection by shutting off the switch unit 3. That is, the interruption capacity of the switch 31 can be reduced by limiting the interruption by the switch unit 3 to a case where the backflow current Io is relatively small. That is, the generation of an arc when the switch 31 is interrupted can be suppressed. Moreover, since the fusing characteristics by the bonding wire do not depend on the direction of the current, for example, the fusing characteristics cannot be such that the fusing does not occur with a large forward current and the fusing with a relatively small reverse current Io. On the other hand, in the configuration of the present embodiment, by combining the fusing member and the switch unit 3, it is easy to protect the component from the large reverse current Io and to protect the component from the small reverse current Io. Both can be achieved.

FIG. 4 is a diagram showing operation states of the vehicle power supply system 1 shown in FIG. FIG. 4 shows, in order from the left, the connection state of the battery 5, the state of the rectifying element (transistor Q5 and transistor Q6) of the DC-DC converter 2, the direction of current (the direction of the energization current of the switch unit 3), and the magnitude of the current. (The magnitude of the energization current of the switch unit 3), the state of the switch unit 3, and the state of the fusing members (bonding wires 225 to 228) are shown. It is assumed that the operating area A of the switch unit 3, the fusing characteristics C1 of the fusing members (bonding wires 225 to 228), the characteristics B of the parts, and the maximum output current of the battery 5 are as shown in FIG.

When the connection state of the battery 5 is “forward connection” (normal state) and the state of the rectifying element of the DC-DC converter 2 is “normal”, the current direction is “forward direction” and the magnitude of the current Is “under rated” by the control of the DC-DC converter 2 or the like. Moreover, the switch part 3 is "on state", and the state of a fusing member is "non-fusing". For reference, in FIG. 3, the magnitude of the rated current is indicated by a broken line.

When the connection state of the battery 5 is “forward connection” (normal state) and the state of the rectifying element of the DC-DC converter 2 is “failure occurrence”, the direction of the current is “reverse direction”. However, it is assumed that the content of “failure occurrence” is a failure in a state where the drain and source of the transistor Q5 or Q6 are short-circuited or a failure in a state where the transistor Q5 or Q6 is always turned on. At this time, when the magnitude of the current is less than the first reference value shown in FIG. 3, the state of the switch unit 3 is “ON”, and the state of the fusing member is within the characteristic C1 shown by the chain line in FIG. State. In addition, when the magnitude of the current is not less than the first reference value shown in FIG. 3 (and not more than the second reference value), the state of the switch unit 3 becomes “off state” after the delay time has elapsed, and the state of the fusing member Is within the characteristic C1 shown by the chain line in FIG. Further, when the magnitude of the current is larger than the second reference value shown in FIG. 3, the state of the switch unit 3 becomes “off state” after the delay time elapses, and the state of the fusing member is the fusing characteristic indicated by the chain line in FIG. According to C1, it will be in the "melting" state after a predetermined time has elapsed. However, when the magnitude of the current is larger than the second reference value shown in FIG. 3, the time required for the fusing member to “blow” is shorter than the delay time for the switch unit 3 to be in the “off state”. Is first blown out, the switch unit 3 does not actually perform the operation of setting the reverse current Io larger than the second reference value to the “off state”.

Further, when the connection state of the battery 5 is “reverse connection” (abnormal state), the power is not supplied to the ON / OFF circuit 32, so that the switch unit 3 is in the “off state” and the switch 31 is turned off. Since no current flows from the battery 5 into the rectifier circuit 22, the fusing member is in a “non-blown” state.

As described above, in the first embodiment, the vehicle power supply system 1 that supplies the power to the battery 5 by stepping down the voltage of the power supply 4 that supplies power to the motor 61 that drives the vehicle by the DC-DC converter 2. The rectifier circuit 22 and the switch unit 3 are configured as follows. That is, the rectifier circuit 22 is provided in the DC-DC converter 2 and is a circuit that rectifies the electric power supplied from the DC-DC converter 2 to the battery 5 to a direct current, and includes a rectifier element (transistors Q5 and Q6) and an external circuit. At least a part of the wire is connected via a fusing member (bonding wires 225 to 228). The switch unit 3 is provided between the rectifier circuit 22 and the battery 5, detects a reverse current Io flowing from the battery 5 to the DC-DC converter 2, and according to the reverse current Io, the battery 5 and the rectifier circuit 22. The switch 31 connected between is switched from the on state to the off state. That is, the first embodiment is based on the backflow current detection between the rectifier circuit 22 in which at least a part between the rectifier element and the outside is connected via the fusing member, and the DC-DC converter 2 and the battery 5. A switch unit 3 having a blocking function. As a result, when the backflow current Io is generated, the fusing member is blown for a large current, and the switch unit 3 can be turned off for a small current. Therefore, the DC-DC converter 2 is made larger than the conventional one. Thus, it is possible to provide a vehicle power supply system 1 that can be made inexpensive and inexpensive.

As shown in FIG. 3, in the first embodiment, the fusing member has a value larger than a first reference value that is a value of the backflow current Io that is a determination criterion for switching the switch 31 from the on state to the off state. Fusing when a certain second reference value is exceeded. According to this configuration, when the second reference value is exceeded, by setting the fusing member to blow before the switch 31 is turned off, the switch 31 is turned off when the switch 31 is turned off. It is possible to prevent the occurrence of arcing at the point. Therefore, in the first embodiment, the switch unit 3 switches the switch 31 from the on state to the off state when the state in which the backflow current Io exceeds the first reference value continues for a predetermined delay time. Yes. Further, the fusing member is blown out in a time shorter than the predetermined delay time.

Further, in the first embodiment, when the first reference value, the predetermined delay time, and the fusing member, the current value flowing through the fusing member and the current value flowing through the fusing member, the fusing member is blown. The fusing characteristics indicating the fusing time until the time is determined are determined according to the component rating of the component including the rectifying element and through which the backflow current Io flows. Thus, according to the first embodiment, it is possible to protect components including the rectifying element and through which the backflow current Io flows.

Also, the number and cross-sectional area of the fusing member can be set according to the second reference value. In this case, the cooperation between the protection by the switch unit 3 and the protection by the fusing member can be easily set.

<Second Embodiment>
Next, a second embodiment of the present invention will be described with reference to FIG. The second embodiment is different from the first embodiment in the following configuration. That is, in the first embodiment, the bonding wires 225 to 228 that connect the semiconductor chip constituting the rectifying element (transistor Q5 and transistor Q6) and the outside of the semiconductor chip are used as the fusing member. On the other hand, in the second embodiment, a fusing member is provided in the wiring patterns P1 and P2 on the substrate in the rectifier circuit 22. The fusing member may be a pattern itself in which the thickness or width of all or part of the wiring patterns P1 and P2 has a predetermined fusing characteristic, or functions as a fuse in the wiring patterns P1 and P2. It is good also as a structure which interposes the chip components to perform in series. Also in the second embodiment, the bonding wires 225 to 228 may have predetermined fusing characteristics as in the first embodiment.

According to the second embodiment, as in the first embodiment, the DC-DC converter 2 is not made larger and less expensive than the conventional one while protecting against a large or small backflow current Io. The vehicular power supply system 1 can be provided.

It should be noted that the first embodiment and the second embodiment can be modified as follows, for example. That is, in each of the above embodiments, the rectifier circuit 22 is configured as a synchronous rectification system, but the transistors Q5 and Q6 may be configured as an asynchronous rectification system instead of a bare chip diode, for example. In the above embodiment, the switch unit 3 includes the current detection unit 34. However, the current detection unit 34 is provided outside the switch unit 3 so that the input unit 322 receives the detection signal of the reverse current Io. Also good. In addition, a function for inputting a control signal from an external ECU (electronic control unit) or DC-DC converter control unit 24 to the switch unit 3 and turning on or off the switch 31 according to the control signal is added to the switch unit 3 May be. Further, the switch unit 3 and the DC-DC converter 2 may be configured integrally. In FIG. 1, the large-capacity fuse 7 may be omitted.

As described above, the embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes design and the like within the scope not departing from the gist of the present invention.

DESCRIPTION OF SYMBOLS 1 Vehicle power supply system 2 DC-DC converter 3 Switch part 4 Power supply 5 Battery 22 Rectifier circuit 31 Switch Q5, Q6 Transistor (rectifier element)
225 to 228 Bonding wire (melting member)

Claims (7)

In a vehicle power supply system for supplying power to a battery by stepping down a voltage of a power supply that supplies power to a motor that drives the vehicle by a DC-DC converter,
The circuit is provided in the DC-DC converter and rectifies the electric power supplied to the battery by the DC-DC converter into a direct current, and at least a part between the rectifying element and the outside is provided via a fusing member. A connected rectifier circuit;
Provided between the rectifier circuit and the battery, detects a reverse current flowing from the battery to the DC-DC converter, and is connected between the battery and the rectifier circuit according to the reverse current. A switch part for turning the switch off from the on state,
A vehicle power supply system comprising: The fusing member is blown when it exceeds a second reference value that is larger than a first reference value that is a value of the backflow current that is a criterion for determining the switch from an on state to an off state. The vehicle power supply system according to claim 1. 3. The switch unit according to claim 2, wherein the switch unit turns the switch from an on state to an off state when a state in which the backflow current exceeds the first reference value continues a predetermined delay time. 4. Power supply system for vehicles. The vehicular power supply system according to claim 3, wherein the fusing member is fused in a time shorter than the predetermined delay time. The first reference value and the predetermined delay time;
In the fusing member, a fusing characteristic indicating a current value flowing through the fusing member and a fusing time until the fusing member is blown when the current value flows through the fusing member,
5. The vehicle power supply system according to claim 3, wherein the vehicle power supply system is determined according to a component rating of a component including the rectifying element and through which the reverse current flows. The vehicular power supply system according to any one of claims 2 to 5, wherein the fusing member has a number and a cross-sectional area set in accordance with the second reference value. A control method of a vehicle power supply system for supplying power to a battery by stepping down a voltage of a power supply that supplies power to a motor that drives the vehicle by a DC-DC converter,
The DC-DC converter has a rectifier circuit in which at least a part between the rectifier element and the outside is connected via a fusing member,
In a switch unit provided between the rectifier circuit and the battery, a switch connected between the battery and the rectifier circuit is turned on in response to a reverse current flowing from the battery to the DC-DC converter. From state to off,
A control method for a vehicle power supply system.

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