JP2009290966A - Power supply protection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To protect a battery from over-discharge by making it possible to interrupt the short circuit route when micro short circuit arises in a power supply. <P>SOLUTION: A first route (a high current fuse 22a) which can be interrupted by a first current is formed as a conduction route in series with a battery 21, a second route (a low current fuse 22b) which can be interrupted by a second current smaller than the first current is formed in parallel with the first route, and the conduction route is switched between the first and second routes. When power is supplied, it is conducted via the first route, the conduction route is switched to the second route when power supply is stopped, and the second route is interrupted when micro short circuit arises. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a power supply protection device, and more particularly, to a technique for protecting a battery from overdischarge due to a fine short circuit that occurs inside a power supply configured by connecting a plurality of single cells in series.

  In an electric vehicle such as a hybrid vehicle, a power source for the motor is configured by connecting a plurality of batteries (single cells) in series in order to secure a current required for driving the motor. Here, as a problem caused by the fine short circuit generated in the power source, there is a concern about deterioration of the battery due to overdischarge, generation of tracking, or the like.

As a countermeasure against this fine short circuit, Patent Document 1 discloses that an abnormality of a battery is detected, and the battery in which the abnormality has occurred is disconnected from the power system so that the influence of the abnormal battery affects other batteries. The technique of avoiding is described. Specifically, a power source is constituted by a battery group in which a plurality of batteries (single cells) are connected in series, and a voltmeter is installed for each battery. When an abnormality of the battery is detected by the voltmeter, a circuit that bypasses the battery group is closed, and the battery and a fuse connected in series with the bypass circuit are blown, thereby removing the abnormal battery from the power system. To avoid the influence of other abnormal batteries on other batteries.
JP 2002-142353 A (paragraph numbers 0017, 0018)

However, the techniques described in the above documents have the following problems.
In a hybrid vehicle, a secondary battery is generally used as the power source. In the secondary battery, a slight short circuit occurs in the power source due to leakage of the electrolyte. A fine short circuit inside the power supply may be caused not only by leakage of the electrolytic solution but also by adhesion of conductive contamination such as condensed water or dust. Here, according to the technique described above, when an abnormality of a battery due to a fine short circuit is detected, it is possible to disconnect the abnormal battery from the power system by fusing the fuse and avoid the influence on other batteries. However, since the state of the slight short circuit is maintained even after the abnormality is detected, the abnormal battery itself cannot be protected.

  The present invention provides a power supply protection device that takes the above problems into consideration, and in the event of a slight short circuit in a power supply, the short circuit path can be cut off to protect the battery from overdischarge. Objective.

  In the present invention, as a current-carrying path in series with the battery, a first path that can be interrupted by a relatively large first current, a parallel to the first path, and more than the first current A second path that can be cut off by a small second current is formed, and the energization path is switched between the first and second paths. At the time of power supply, the battery power is supplied to the load by energizing through the first path. On the other hand, when the power supply is stopped, the energization path is switched to the second path to form a short circuit path for the battery. In this case, the discharge of the battery is suppressed by blocking the second path.

  A power supply protection device according to one embodiment of the present invention is a power supply protection device provided in a power supply including a plurality of single cells connected in series. Here, a high current fuse and a low current fuse are connected in parallel between a pair of single cells among the plurality of single cells. The high current fuse sets its breaking current to a relatively large value, and the low current fuse sets its breaking current to a smaller value than the high current fuse. A first relay and a first relay driving unit for driving the first relay are disposed, and the energization path between the pair of unit cells is divided into a first path via a high current fuse and a low current fuse. It is possible to switch between the second route through.

  According to the present invention, when a short circuit occurs in the power supply, the short circuit path is blocked by blocking the second path, and thus the battery can be protected from overdischarge due to the short circuit.

  According to one aspect of the present invention, in a power supply including a plurality of unit cells connected in series, a high current fuse and a low current fuse having different cutoff currents are interposed between a pair of unit cells, and the first By switching these fuses using a relay and causing them to function, when a short-circuit occurs, the short-circuit path can be cut off by the second fuse having a small cut-off current to protect the battery.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 shows a schematic configuration of a power unit including a power supply protection device according to an embodiment of the present invention.

  In the present embodiment, the motor generator 1 is a three-phase induction type rotating electrical machine and operates with the battery 2 as a power source. The motor generator 1 constitutes a drive source of a hybrid vehicle (in this embodiment, a series hybrid vehicle) that is an electric vehicle in combination with an internal combustion engine (not shown). The vehicle can be propelled by transmitting the output torque of the motor generator 1 to the drive wheels of the vehicle.

  The battery 2 is a direct current power source, and is configured by connecting a plurality of batteries (corresponding to “single cells”) in series. In this embodiment, a nickel metal hydride battery that is a secondary battery is used as the battery. It is also possible to use a lithium ion battery for the battery. The battery 2 has a power supply line 4 connected to the positive terminal and a ground line 5 connected to the negative terminal, and the phase arms 31 u to 31 w of the inverter 3 are connected in parallel between these lines 4 and 5. ing.

  The inverter 3 converts the DC voltage of the battery 2 into u to w-phase AC voltage. The converted AC voltage is applied to the motor generator 1 as a drive voltage. The motor generator 1 can also be operated as a generator by driving a rotating shaft (not shown), and the AC power generated by the motor generator 1 is converted into DC power by the inverter 3 to charge the battery 2. be able to. A pair of power semiconductor elements (hereinafter referred to as “power switching elements”) are connected in series to the phase arms 31 u to 31 w of the inverter 3. The inverter 3 converts a voltage between direct current and alternating current based on the on / off operation of the power switching elements 32a to 32f. The power switching elements 32 a to 32 f can be implemented by insulated gate bipolar transistors (IGBTs), and their on / off operations are controlled based on switching control signals output by the control unit 8. An intermediate point of each phase arm 31 u to 31 w is connected to a corresponding coil of motor generator 1, and an AC voltage converted by on / off operation of power switching elements 32 a to 32 f is applied to motor generator 1.

  The capacitor 6 functions as a smoothing capacitor, and is connected between the power supply line 4 and the ground line 5 in parallel to the inverter 3 and closer to the power supply side than the inverter 3.

  Control unit 8 detects a current (hereinafter referred to as “motor current”) supplied to each phase coil of motor generator 1, and controls on / off operation of power switching elements 32 a to 32 f based on this current. Sets and outputs a switching control signal. In the present embodiment, a u-phase current sensor 81 that detects a motor current (u-phase motor current) supplied to the u-phase coil of the motor generator 1 and a motor current (v-phase motor current) supplied to the v-phase coil are detected. The rotation angle sensor 83 which detects the rotation angle of the rotor which comprises the v phase current sensor 82 which performs the motor generator 1, and the rotor is provided. The control unit 8 sets a switching control signal based on the detection signals from these sensors 81 to 83 and outputs the switching control signal to the drive unit 7.

  The drive unit 7 converts the switching control signal output by the control unit 8 into a voltage signal and applies it to the corresponding power switching elements 32a to 32f.

  FIG. 2 shows the configuration of the power supply unit of the power plant according to this embodiment. This power supply unit has a function as a “power supply device”.

  In the present embodiment, a battery 2 as a power source is configured by connecting a plurality of batteries 21, 21... In series, and the DC voltage of the battery 2 is increased to a predetermined system voltage by the boost converter 9. , Supplied to the inverter 3. The battery 2 incorporates the power protection device according to the present embodiment. This power protection device includes fuses having different cutoff currents (a high current fuse 22a and a low current fuse 22b) and these fuses 22a and 22b. Is provided with a relay (corresponding to a “first relay”) 23 configured to be able to switch a contact with respect to. The high current fuse 22a is set to a large cut-off current that can energize a current necessary for driving the motor generator 1 during traveling of the vehicle, and a pair of adjacent batteries 21 among a plurality of batteries constituting the power source, 21 are connected in series to these batteries. On the other hand, the low current fuse 22b is set to a cut-off current smaller than that of the high current fuse 22a, which can be cut off by a current due to a short circuit, and is parallel to the high current fuse 22a between the batteries 21 and 21. It is connected. The connection of the fuses 22 a and 22 b to the batteries 21 and 21 is switched by switching the contact of the relay 23 by a relay drive unit (corresponding to “first relay drive unit”) 24. The pair of batteries 21 and 21 sandwiching the high current fuse 22a and the low current fuse 22b can be appropriately selected.

  In the present embodiment, a fuse sensor 25 for detecting the interruption of the low current fuse 22b is provided. A warning light (corresponding to a “warning unit”) 26 is used to make the driver recognize the occurrence of a fine short circuit inside the battery 2, and the fuse sensor 25 detects the interruption of the low-current fuse 22 b. In some cases, it is actuated by the detection signal of the fuse sensor 25. The fuse sensor 25 can be implemented by a voltmeter.

  Further, in the present embodiment, a first main relay 27 for cutting off the power supply line 4 between the battery 2 and the boost converter 9 when the system of the power unit is stopped and a first main relay 27 for cutting off the ground line 5 are used. Two main relays 28 are interposed. The on / off operation of the first and second main relays 27, 28 is controlled by the main relay drive unit 29. The main relays 27 and 28 correspond to a “second relay”, and the main relay drive unit 29 corresponds to a “second relay drive unit”.

  Next, the operation of the power protection device according to this embodiment will be described.

  FIG. 3 is a flowchart showing operations performed by the relay drive unit 24 and the main relay drive unit 29 when the system is stopped.

  In S101, a power switch signal is read. This power switch is configured as a key switch or the like, and is operated by the driver.

  In S102, it is determined based on the read power switch signal whether the system is stopped. When the system is stopped, the process proceeds to S103, and when it is during other driving (running), this routine is terminated.

  In S103, the system (power unit) is stopped, and the first and second main relays 27 and 28 are shut off. The process of S103 is performed by the main relay drive unit 29.

  In S104, it is determined whether or not a predetermined time t1 has elapsed after the system is stopped. This t1 is set to such a length that the system can be regarded as being left after the system is stopped. When the predetermined time t1 has elapsed, the process proceeds to S105, and when it has not elapsed, the process returns to S102 and the processes of S102 to 104 are repeated. The process of S104 is performed by the relay drive unit 24.

  In S105, the contact of the relay 23 is set to the low current fuse 22b side.

  In S106, the relay 23 is driven by the relay drive unit 24, and the contact of the relay 23 is switched to the low current fuse 22b side.

  FIG. 4 schematically shows an energization path during traveling. During traveling, the contact of the relay 23 is set on the high current fuse 22a side, and a voltage is applied to the motor generator 1 through an energization path (corresponding to a “first path”) via the high current fuse 22a. . The cut-off current of the high current fuse 22a is set to such a magnitude that a current necessary for driving the motor can be passed.

  FIG. 5 schematically shows an energization path when the system is stopped (when left). When the system is stopped, the main relays 27 and 28 are cut off, and the contact of the relay 23 is switched to the low current fuse 22b side. If the battery 2 is in a normal state, the battery 21 is not discharged. However, when a slight short circuit occurs due to leakage of the electrolyte solution or adhesion of conductive contamination (in FIG. 5, a conductive material such as the electrolyte solution is indicated by a minute resistance r), a short circuit path of the battery 21 is formed, and the battery 2 causes a discharge due to a short circuit. Here, since the cut-off current of the low-current fuse 22b is set to a magnitude that can be cut off by the current due to the fine short circuit, the low-current fuse 22b is quickly blown when the fine short-circuit occurs, and the short-circuit path Is cut off. The occurrence of the slight short circuit is detected as a blow of the low current fuse 22b by the fuse sensor 25 at the next system start-up and is notified to the driver by the warning lamp 26.

  As described above, in this embodiment, since the contact of the relay 23 is switched to the low current fuse 22b side when the system is stopped (when left), a low current is generated when a short circuit occurs in the battery 2. The fuse 22b can be quickly blown to cut off the short circuit path. Therefore, it is possible to protect the battery 21 from overdischarge due to a fine short circuit and to prevent occurrence of tracking. Since leakage of the electrolyte tends to occur when the system is left standing for a long time with the system stopped, in this embodiment, switching to the low current fuse 22b is performed only when left unattended. Therefore, unnecessary switching operation of the relay 23 is avoided. A slight short circuit that occurs during traveling can be detected by a separately performed leakage detection routine.

  In the present embodiment, “the means for forming the first and second paths” is configured by the high current fuse 22 a and the low current fuse 22 b, and “the means for switching the energization path” is configured by the relay 23 and the relay drive unit 24. Composed.

  In the above, the case where one power supply protection device is installed in the battery 2 constituted by a series of batteries 21, 21... Connected in series has been described as an example. However, the present invention is not limited to this, and two or more power protection devices may be installed in the battery 2. FIG. 6 shows an example in which two power protection devices A and B are installed. A first power protection device A is connected in series between the pair of batteries 21a and 21a on the positive terminal side, and a second power source is connected between the pair of batteries 21b and 21b on the negative terminal side. A protection device B is connected in series with these batteries. In this way, by installing the plurality of power protection devices A and B, when a short circuit occurs at a plurality of locations in the battery 2, the short-circuit path is interrupted at each location, and the battery 21a is protected from overdischarge. , 21b can be protected.

  In the above description, the case where the power protection device is interposed between the pair of batteries 21 and 21 constituting the battery 2 has been described as an example. However, the present invention is not limited to this. You may install a power supply protective device in the negative electrode terminal side rather than the battery of the most negative electrode side. FIG. 7 shows, as an example of the latter case, a power supply unit in which the power supply protection device is installed closer to the negative electrode terminal side than the battery 21 on the most negative electrode side. According to such a configuration, it is possible to protect the battery 21 from overdischarge and prevent the occurrence of tracking against a fine short circuit generated between the negative electrode terminal (or the positive electrode terminal) and the battery 21.

  Furthermore, a battery group may be configured by a plurality of batteries 21, 21... Connected in series, and the battery 2 may be configured by connecting a plurality of battery groups in parallel to each other. The power protection device can be installed at an appropriate location in each battery group.

  The electric vehicle to which the present invention is applied is not limited to a hybrid vehicle, and may be an electric vehicle using only a motor as a drive source.

Configuration of a power unit including a power protection device according to an embodiment of the present invention Configuration of the power supply unit (power supply unit) of the power unit Flow chart of system stop control routine Schematic circuit configuration during driving Schematic circuit configuration when the system is stopped (when left) Configuration of a power supply device according to another embodiment of the present invention Configuration of power supply apparatus according to still another embodiment of the present invention

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Motor generator, 2 ... Battery, 21 ... Battery (single cell), 22a ... High current fuse, 22b ... Low current fuse, 23 ... Relay as "first relay", 24 ... "First relay drive unit , 25 ... fuse sensor (voltmeter), 26 ... warning light as "warning unit", 27, 28 ... main relay as "second relay", 29 ... "second relay driving Main relay drive unit as unit ", 3 ... inverter, 31u to 31w ... arm of inverter, 32a to 32f ... power switching element (IGBT), 4 ... power supply line, 5 ... ground line, 6 ... capacitor, 7 ... drive unit 8 ... Control unit, 81 ... u-phase current sensor, 82 ... v-phase current sensor, 83 ... rotation angle sensor, 9 ... boost converter Micro-resistance due to the r ... conductive material.

Claims (8)

A power protection device provided in a power supply comprising a plurality of single cells connected in series,
A high current fuse having a relatively large breaking current connected in series between a pair of cells among the plurality of cells;
A low current fuse having a cut-off current smaller than that of the high current fuse, connected in parallel to the high current fuse between the pair of cells;
A first relay disposed so that the energization path between the pair of single cells can be switched between a first path via the high current fuse and a second path via the low current fuse;
A first relay driving unit configured to drive the first relay, and switching a contact of the first relay between the high current fuse side and the low current fuse side;
A power protection device configured to include.   The power supply protection device according to claim 1, wherein the power supply is a power supply for a travel motor of an electric vehicle.   The first relay drive unit sets the contact point of the first relay to the high current fuse side when the electric vehicle is running, and switches to the low current fuse side when the system of the electric vehicle is stopped. The power protection device described in 1.   The first relay drive unit switches the contact of the first relay to the low-current fuse side when the electric vehicle is left standing for a predetermined time after the system is stopped. The power protection device described in 1. A fuse sensor for detecting disconnection of the low current fuse;
A warning unit configured to generate a warning regarding the disconnection based on the output of the fuse sensor;
The power supply protection device according to claim 1, further comprising: A plurality of cells connected in series;
The power protection device according to any one of claims 1 to 5, wherein the high-current fuse and the low-current fuse are connected between a pair of single cells among the plurality of single cells.
A power supply comprising the above. A second relay arranged to be able to cut off the connection to the load of the positive line or the negative line of the power supply;
A second relay driving unit configured to drive the second relay, and further comprising
The said 1st relay drive unit switches the contact of the said 1st relay to the said low current fuse side in response to interruption | blocking of the connection of the said positive electrode line or negative electrode line by the said 2nd relay. Power supply. As a current-carrying path in series with the battery, a first path that can be cut off by a relatively large first current and a second path that is parallel to the first path and smaller than the first current. A second path that can be interrupted by a current of
Means for switching the energization path between the first and second paths,
At the time of power supply, the power of the battery is supplied to the load by energizing through the first path,
A power protection device that suppresses discharge of the battery by switching the energization path to the second path and stopping the second path when the battery is short-circuited when power supply is stopped.

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