JP7388008B2 - Automotive power storage device - Google Patents

Description

The present invention relates to a protection circuit for a vehicle-mounted power storage element.

The power storage device is equipped with a cutoff switch, which protects the device by cutting off the current when an abnormality occurs. Patent Document 1 listed below discloses a technique using a semiconductor switch such as an FET as a cutoff switch.

Japanese Patent Application Publication No. 2003-169422

In order to prevent the vehicle from losing power, it is preferable that the vehicle-mounted power storage device maintains power supply even when charging is cut off. FIG. 13 shows a block of a power storage device 300, which includes a battery pack 310, a cutoff switch 320, and a management device 330.

When the cutoff switch 320 is two FETs 321 and 323 connected back-to-back, as shown in FIG. 13, by turning off the first FET 321 and turning on the second FET 323, discharging can be allowed and charging can be cut off. .

That is, since the parasitic diode 322 of the first FET 321 has a forward discharge direction, the discharge current can flow through the parasitic diode 322 of the first FET 321 and the source-drain of the second FET 323, as shown in FIG. On the other hand, the charging current is cut off because the parasitic diode 322 is in the opposite direction.

The parasitic diode 322 has a small current capacity. If a current exceeding the allowable value flows, heat may be generated and the parasitic diode 322 may fail. Even when the current capacity is increased by connecting another diode in parallel to the parasitic diode 322, a similar problem occurs if a current exceeding the allowable value flows.
The purpose of this invention is to suppress failure of the diode or FET when discharging is performed using an FET with a diode connected between the source and drain.

A protection circuit for a vehicle-mounted power storage element includes a cutoff switch that cuts off the current of the power storage element, a bypass circuit connected in parallel with the cutoff switch, and a control section, and the cutoff switch is connected back-to-back. a first FET and a second FET, the first FET having a first diode connected between a source and a drain, and the second FET having a first diode connected between a source and a drain, and a second FET having a diode in a direction opposite to that of the first diode. a second diode, the bypass circuit allows discharge from the power storage element to the vehicle while the current is cut off by the cutoff switch, and the control unit is configured such that the discharge current flowing through the bypass circuit is equal to or higher than a limit value. If so, the current path of the discharge current is switched from a path passing through the bypass circuit to a path passing through the cutoff switch.

The present technology can be applied to a vehicle-mounted power storage device. The present invention can be applied to a protection circuit control method, a protection circuit control program, and a recording medium storing a protection circuit control program.

When discharging is performed using an FET with a diode connected between the source and drain, failure of the diode or FET can be suppressed.

Exploded perspective view of battery Top view of secondary battery Cross-sectional view taken along line AA in Figure 2 car side view Battery block diagram IV characteristics of constant current diode Bypass circuit schematic Protection processing flowchart Explanatory diagram of circuit operation of protection circuit Explanatory diagram of circuit operation of protection circuit Side view of a motorcycle Bypass circuit schematic Circuit diagram of comparative example

A protection circuit for a vehicle-mounted power storage element includes a cutoff switch that cuts off the current of the power storage element, a bypass circuit connected in parallel with the cutoff switch, and a control section, and the cutoff switch is connected back-to-back. a first FET and a second FET, the first FET having a first diode connected between a source and a drain, and the second FET having a first diode connected between a source and a drain, and a second FET having a diode in a direction opposite to that of the first diode. a second diode, the bypass circuit allows discharge from the power storage element to the vehicle while the current is cut off by the cutoff switch, and the control unit is configured such that the discharge current flowing through the bypass circuit is equal to or higher than a limit value. If so, the current path of the discharge current is switched from a path passing through the bypass circuit to a path passing through the cutoff switch.

After the current is cut off by the cutoff switch, a discharge current is allowed to flow through the bypass circuit to maintain power supply to the vehicle. When a discharge current exceeding a limit value flows through the bypass circuit, the control unit switches the current path of the discharge current from the bypass circuit to a path passing through the cutoff switch. Therefore, it is possible to suppress a failure of the bypass circuit due to a current exceeding the limit value flowing through the bypass circuit.

The current path of the cutoff switch is one that turns on both the first FET and the second FET and passes through the source-drain of the first FET and the second FET, and one that turns off the first FET and turns on the second FET and passes through the first diode and the second FET. There are two current paths, one through the source-drain of the 2FET. The control unit can select the above two current paths when switching the current path of the discharge current from the bypass circuit to the cutoff switch. Therefore, compared to the case where the discharge current continues to flow using only the path passing through the first diode, it is possible to suppress failure of the cutoff switch. During the discharge period in the bypass circuit, at least no current flows through the cutoff switch and no heat is generated in the diode or FET, so failure of the cutoff switch can be suppressed.

When the discharge current flowing through the bypass circuit exceeds a limit value, the control unit changes the current path of the discharge current from a path passing through the bypass circuit to a source of the first FET and the second FET of the cutoff switch. - You may switch to a path through the drain. A current exceeding the limit value flows between the sources and drains of the first FET and the second FET, and does not flow through the first diode or the second diode. Therefore, it is possible to suppress the diode from generating heat and breaking down.

The bypass circuit may include a current limiter. Since the current in the bypass circuit can be limited, the rating of the bypass circuit can be reduced.

The current limiting section may be a constant current element or a constant current circuit. Since the maximum current of the bypass circuit can be suppressed to a predetermined value or less, it is effective in protecting the bypass circuit.

The current limiting section has a linear region in IV characteristics, the control section detects the current of the bypass circuit based on the voltage across the current limiting section, and the limiting value is within the linear region. A current value within the range may be used. In the linear region, the current detection accuracy is high, so it can be determined with high accuracy whether the current in the bypass circuit exceeds the limit value. Therefore, responsiveness becomes high when a current exceeding the limit value flows. In other words, when the current in the bypass circuit exceeds the limit value, the current path can be quickly switched.

<Embodiment 1>
1. Structural Description of Battery 50 As shown in FIG. 1, the battery 50 includes an assembled battery 60, a circuit board unit 65, and a housing 71. Battery 50 is an example of a power storage device.

The container 71 includes a main body 73 and a lid 74 made of a synthetic resin material. The main body 73 has a cylindrical shape with a bottom. The main body 73 includes a bottom part 75 and four side parts 76. An upper opening 77 is formed at the upper end portion by the four side portions 76 .

The housing body 71 houses the assembled battery 60 and the circuit board unit 65. The assembled battery 60 has twelve secondary batteries 62. The 12 secondary batteries 62 are connected 3 in parallel and 4 in series. The circuit board unit 65 includes a circuit board 100 and electronic components mounted on the circuit board 100, and is arranged above the assembled battery 60.

The lid 74 closes the upper opening 77 of the main body 73. An outer peripheral wall 78 is provided around the lid body 74. The lid body 74 has a protrusion 79 that is approximately T-shaped in plan view. A first external terminal 51 of a positive electrode is fixed to one corner of the front part of the lid 74, and a second external terminal 52 of a negative electrode is fixed to the other corner.

As shown in FIGS. 2 and 3, the secondary battery 62 has an electrode body 83 housed in a rectangular parallelepiped-shaped case 82 together with a non-aqueous electrolyte. The secondary battery 62 is, for example, a lithium ion secondary battery. The case 82 includes a case body 84 and a lid 85 that closes an upper opening of the case body 84.

Although not shown in detail, the electrode body 83 has a porous structure between a negative electrode element made of a base material made of copper foil coated with an active material and a positive electrode element made of a base material made of aluminum foil coated with an active material. A separator made of resin film is arranged. All of these are band-shaped, and are wound in a flat shape so that they can be accommodated in the case body 84, with the negative electrode element and the positive electrode element shifted to opposite sides in the width direction with respect to the separator. .

A positive electrode terminal 87 is connected to the positive electrode element via a positive electrode current collector 86, and a negative electrode terminal 89 is connected to the negative electrode element via a negative electrode current collector 88. The positive electrode current collector 86 and the negative electrode current collector 88 include a flat pedestal portion 90 and leg portions 91 extending from the pedestal portion 90. A through hole is formed in the pedestal portion 90. The leg portion 91 is connected to the positive electrode element or the negative electrode element. The positive electrode terminal 87 and the negative electrode terminal 89 consist of a terminal main body portion 92 and a shaft portion 93 that projects downward from the center portion of the lower surface thereof. Among them, the terminal body portion 92 and the shaft portion 93 of the positive electrode terminal 87 are integrally molded from aluminum (a single material). In the negative electrode terminal 89, the terminal main body portion 92 is made of aluminum, and the shaft portion 93 is made of copper, and these are assembled together. Terminal body portions 92 of the positive electrode terminal 87 and the negative electrode terminal 89 are arranged at both ends of the lid 85 with a gasket 94 made of an insulating material interposed therebetween, and are exposed to the outside from the gasket 94.

Lid 85 has a pressure release valve 95. The pressure release valve 95 is located between the positive terminal 87 and the negative terminal 89, as shown in FIG. The pressure release valve 95 opens to lower the internal pressure of the case 82 when the internal pressure of the case 82 exceeds a limit value.

The battery 50 can be used by being mounted on the automobile 10, as shown in FIG. The battery 50 may be used for starting the engine 20 that is the drive device of the automobile 10. The automobile 10 may be an idling stop vehicle. Idling stop is a system that automatically turns off the engine when the vehicle is stopped, such as when waiting at a traffic light, and restarts the engine when the vehicle is started.

2. Electrical Configuration of Battery 50 FIG. 5 is a block diagram of the battery 50. The battery 50 includes an assembled battery 60, a current sensor 53, a cutoff switch 55, a voltage measurement circuit 110, a management section 130, a bypass circuit 150, and a temperature sensor (not shown) that detects the temperature of the assembled battery 60. , is provided.

The assembled battery 60 is composed of a plurality of secondary batteries 62. There are 12 secondary batteries 62, which are connected three in parallel and four in series. In FIG. 5, three secondary batteries 62 connected in parallel are represented by one battery symbol. The secondary battery 62 is an example of a "power storage element." The battery 50 is rated at 12V.

The assembled battery 60, current sensor 53, and cutoff switch 55 are connected in series via a power line 66 and a power line 67. The power line 66 and the power line 67 are examples of current paths.

The power line 66 is a power line that connects the first external terminal 51 and the positive electrode of the assembled battery 60. The power line 67 is a power line that connects the second external terminal 52 and the negative electrode of the assembled battery 60.

The current sensor 53 is located at the negative electrode of the assembled battery 60 and is provided on the power line 67 on the negative electrode side. The current sensor 53 can measure the current I of the assembled battery 60.

The voltage measurement circuit 110 can detect the voltage V of the four secondary batteries 62 , the secondary battery 62 , the secondary battery 62 , the secondary battery 62 , and the total voltage of the assembled battery 60 . The total voltage of the assembled battery 60 is the total voltage of four secondary batteries.

The management unit 130 includes a CPU 131 and a memory 133. The management unit 130 performs monitoring processing of the battery 50 based on the outputs of the voltage measurement circuit 110, the current sensor 53, and the temperature sensor. The management unit 130 is an example of a control unit. The memory 133 may store information necessary for monitoring the battery 50 and information necessary for performing a protective operation in the event of overcharging. The information necessary for the protective operation during overcharging is, for example, the current limit value Ia of the bypass circuit 50 and the allowable current value of the parasitic diodes 56A and 56B.

Further, the battery 50 is communication-less and does not have a communication function with the automobile 10. That is, the battery 50 does not have a communication means (communication unit) that enables communication with the automobile 10, regardless of the communication form such as wired or wireless. Since the battery 50 is communication-less, the management unit 130 cannot receive information from the automobile 10 regarding the driving state of the vehicle or the operational status of the engine 20 (engine start, engine stop, etc.).

The cutoff switch 55 is located at the negative electrode of the assembled battery 60 and is provided on the negative electrode power line 67 . The cutoff switch 55 includes a first FET 55A and a second FET 55B. The first FET 55A and the second FET 55B are N-channel field effect transistors. By using an FET (field effect transistor) for the cutoff switch 55, the switch can be made smaller.

The first FET 55A has its source connected to the second external terminal 52, and the second FET 55B has its source S connected to the negative electrode of the assembled battery 60. The drain of the first FET 55A and the drain of the second FET 55B are connected. The first FET 55A and the second FET 55B are connected back-to-back.

Back-to-back connection means connecting two FETs back to back, i.e. connecting the drains of the two FETs or connecting the sources of the two FETs.

The first FET 55A has a built-in parasitic diode 56A, and the second FET 55B has a built-in parasitic diode 56B. The parasitic diode 56A is a first diode connected between the source and drain of the first FET 55A. The forward direction of the parasitic diode 56A is the same as the discharge direction. The parasitic diode 56B is a second diode connected between the source and drain of the second FET 55B. The forward direction of the parasitic diode 56B is the same as the charging direction. Parasitic diode 56B has the opposite direction to parasitic diode 56A.

The first FET 55A is turned on when the gate G is at the H level, and turned off when the gate G is at the L level. The same applies to the second FET 55B.

The management unit 130 sends a control signal to the gates G of the first FET 55A and the second FET 55B to control the first FET 55A and the second FET 55B. The control signals can be sent individually, and the first FET 55A and the second FET 55B can also be controlled separately.

When the battery 50 is normal, the management unit 130 sends a control signal to the gate G of the first FET 55A to turn on the first FET 55A. Further, a control signal is sent to the gate of the second FET 55B to turn on the second FET 55B.

When the first FET 55A and the second FET 55B are on, conduction occurs between the source and drain of the first FET 55A and between the source and drain of the second FET 55B, so that the assembled battery 60 can be charged and discharged.

Bypass circuit 150 is connected in parallel with cutoff switch 55. Bypass circuit 150 includes a constant current diode 151 and a switch 155. Constant current diode 151 and switch 155 are connected in series. Constant current diode 151 is an example of a current limiting element. The bypass circuit 150 is for small current, and has a smaller rated current than the cutoff switch 55.

The constant current diode 151 has a forward discharge direction (direction C shown in FIG. 5). FIG. 6 shows the IV characteristics of the constant current diode 151. I is the current of the constant current diode, and V is the voltage across the constant current diode 151 (voltage between the anode and cathode).

Constant current diode 151 has a linear region F1 and a constant current region F2. The linear region F1 is a voltage band from 0 to Vc, and is a region in which the current I increases almost in proportion to the voltage V at both ends. The constant current region is a voltage band equal to or higher than Vc, and is a region in which the current remains constant even if the voltage V between both ends increases. The current value Ic in the constant current region F2 may be approximately several amperes.

As shown in FIG. 5, both ends (anode and cathode) of the constant current diode 151 are connected to the management unit 130 via the signal line 68. The management unit 130 can detect the current flowing through the bypass circuit 150 based on the voltage V across the constant current diode 151. That is, in the linear region F1, the voltage V at both ends and the current I are almost proportional, so the current I can be detected from the voltage V at both ends.

The switch 155 may be a third FET 155A and a fourth FET 155B, as shown in FIG. The third FET 155A and the fourth FET 155B are N-channel field effect transistors.

The third FET 155A has its source connected to the cathode of the constant current diode 151, and the fourth FET 155B has its source S connected to the source of the second FET 55B. The drain of the third FET 155A and the drain of the fourth FET 155B are connected. The third FET 155A and the fourth FET 155B are connected back-to-back.

The third FET 155A has a parasitic diode 156A, and the fourth FET 155B has a parasitic diode 156B. The forward direction of the parasitic diode 156A is the same as the discharge direction. The forward direction of the parasitic diode 156B is the same as the charging direction.

The third FET 155A is turned on when the gate G is at the H level, and turned off when the gate G is at the L level. The same applies to the fourth FET 155B.

By providing the bypass circuit 150 in parallel with the cutoff switch 55, the path through which the discharge current flows is via the bypass circuit 150 and the first path 67A that passes through the source-drain of the first FET 55A and the second FET 55B of the cutoff switch 55. There are two routes, the second route 67B.

The management unit 130 sends a control signal to the gates G of the third FET 155A and the fourth FET 155B to control the third FET 155A and the fourth FET 155B. Control signals can be sent individually, and the third FET 155A and fourth FET 155B can also be controlled separately.

The cutoff switch 55, the bypass circuit 150, and the management unit 130 are a protection circuit 120 that protects the assembled battery 60. Protection circuit 120 is mounted on circuit board 100.

As shown in FIG. 5, the battery 50 is connected to a starting motor 21 which is an engine starting device, an alternator 23 which is a vehicle generator, and a general electric load 25. The general electrical load 25 has a rated voltage of 12V, and includes, for example, a vehicle ECU mounted on the automobile 10, an air conditioner, an audio system, a car navigation system, and auxiliary equipment.

3. Protective operation during overcharging The management unit 130 performs monitoring processing of the battery 50 based on the outputs of the voltage measurement circuit 110, current sensor 53, and temperature sensor.

When the battery 50 is normal, the management unit 130 controls the first FET 55A and the second FET 55B to be turned on, and controls the third FET 155A and the fourth FET 155B to be turned off. Therefore, the first path 67A passing through the source-drain of the first FET 55A and the second FET 55B of the cutoff switch 55 is conductive, and the second path 67B passing through the bypass circuit 150 is non-conducting, so that during normal charging and discharging. The current flows through the first path 67A via the cutoff switch 55, and does not flow through the second path 67B via the bypass circuit 150.

When the amount of power generated by the alternator 23 is larger than the general electrical load 25 of the automobile 10, the assembled battery 60 is charged, which may lead to overcharging.

Overcharging can be determined based on the battery voltage V of the secondary battery 62. For example, the battery voltage V of each secondary battery 62 is compared with a voltage threshold value, and if the battery voltage V of any of the secondary batteries 62 exceeds the voltage threshold value, it can be determined that overcharging has occurred.

FIG. 8 is a flowchart of protection processing executed when overcharging is detected. When the management unit 130 detects overcharging in the battery 50 monitoring process, it switches the cutoff switch 55 from on to off. That is, the management unit 130 sends a control signal to each gate G of the first FET 55A and the second FET 55B, and switches the first FET 55A and the second FET 55B from on to off (S10). By switching off the first FET 55A and the second FET 55B, the first path 67A passing through the source-drain of the first FET 55A and the second FET 55B of the cutoff switch 55 becomes non-conductive, and the current can be cut off. By cutting off the current, charging is cut off.

After cutting off charging, the management unit 130 switches the switch 155 of the bypass circuit 150 from off to on. That is, the management unit 130 sends a control signal to each gate G of the third FET 155A and the fourth FET 155B, and switches the third FET 155A and the fourth FET 155B from off to on (S20).

By turning on the switch 155, the bypass circuit 150 becomes conductive, so that the assembled battery 60 can be discharged through the second path 67B, as shown in FIG. Therefore, the discharge current I flowing from the positive electrode of the assembled battery 60 to the vehicle 10 returns to the negative electrode of the assembled battery 60 through the second path 67B (S30).

If charging is detected after overcharging is interrupted, the management unit 130 may turn off the third FET 155A. Charging can be interrupted by turning off the third FET 155A.

After switching the current path, the management unit 130 monitors the discharge current I flowing through the second path 67B (S40). The discharge current I can be detected from the voltage V across the constant current diode 151.

The management unit 130 determines whether the discharge current I is greater than or equal to the limit value Ia (S50). The limit value Ia is a value smaller than the constant current Ic, as shown in FIG. 6, and is included in the linear region F1 of the constant current diode 151. The limit value Ia is a value smaller than the rated current of the bypass circuit 150, specifically, the rated current of the switch 155.

The management unit 130 maintains the switch 155 of the bypass circuit 150 on when the discharge current I is equal to or less than the limit value Ia. By keeping switch 155 on, bypass circuit 150 remains conductive and discharge current I flows through bypass circuit 150 in second path 67B.

When the discharge current I is equal to or greater than the limit value Ia, the management unit 130 switches the cutoff switch 55 from off to on. That is, the management unit 130 sends a control signal to the gates G of the first FET 55A and the second FET, and switches the first FET 55A and the second FET 55B from off to on (S60).

After switching the cutoff switch 55 from off to on, the management unit 130 switches the switch 155 of the bypass circuit 150 from on to off. That is, the management unit 130 outputs a control signal to the gate G of the third FET 155A and the fourth FET 155B to switch the third FET 155A and the fourth FET 155B from on to off (S70).

When the cutoff switch 55 is turned on, the current path of the discharge current changes from the second path 67B passing through the bypass circuit 150 to the first path 67A passing through the source-drain of the first FET 55A and second FET 55B of the cutoff switch 55. Switch to . Therefore, a current exceeding the limit value Ia can be discharged through the first path 67A (S80). In other words, a current exceeding the limit value Ia can be discharged through a path passing through the source and drain of the first FET 55A and the second FET 55B of the cutoff switch 55. Further, by turning off the switch 155, the bypass circuit 150 becomes non-conductive, and the second path 67B passing through the bypass circuit 150 is cut off. By turning on the cutoff switch 55 and then turning off the switch 155, the current path can be switched without cutting off the discharge to the vehicle 10.

5. Effect Description Since the management unit 130 detects overcharging and turns off the cutoff switch 55, it is possible to protect the battery 50 from overcharging. After detecting overcharging, the management unit 130 turns on the switch 155, so that the battery 50 can be discharged into the vehicle 10 through the bypass circuit 150. Therefore, power supply to the vehicle 10 can be maintained.

Since the parasitic diode 56A of the first FET 55A and the parasitic diode 56B of the second FET 55B are in opposite directions, when the first FET 55A and the second FET 55B are off, no current flows through the parasitic diode 56A of the first FET 55A and the parasitic diode 56B of the second FET 55B. . Therefore, during discharge through the bypass circuit 150, it is possible to suppress the parasitic diode 56A and the parasitic diode 56B from generating heat and causing the first FET 55A and the second FET 55B to fail.

Since the battery 50 does not have a communication function with the vehicle 10, it cannot receive information regarding the operating state of the engine 20 from the vehicle 10. The battery 50 is used for starting the engine, and it is necessary to supply a large discharge current I of about 1000 A to the automobile 10 when starting the engine, but the timing cannot be known in advance.

When the discharge current I exceeds the limit value Ia, the management unit 130 changes the current path of the discharge current from a second path passing through the bypass circuit 150 to a second path passing through the source-drain of the first FET 55A and the second FET 55B of the cutoff switch 55. Switch to route 1. By switching the current path, it is possible to suppress a current exceeding the limit value Ia from flowing through the bypass circuit 150. Moreover, even if a discharge current I exceeding the limit value Ia momentarily flows into the bypass circuit 150 when switching the discharge path, the constant current characteristic of the constant current diode 151 allows the current value to be suppressed to below Ic. . Therefore, it is possible to prevent the bypass circuit 150 from generating heat and being damaged by a large current.

Further, after switching the current path, the discharge current passes through the source-drain of the first FET 55A and the second FET 55B, and does not flow into the two parasitic diodes 56A and 56B. Therefore, it is possible to prevent the parasitic diode 56A and the parasitic diode 56B from generating heat and damaging the first FET 55A and the second FET 55B of the cutoff switch 55.

By applying this technology, when the battery 50 discharges a large current, such as when starting the engine after current cutoff due to overcharging, the parasitic diode 56A and the parasitic diode 56B generate heat, and the first FET 55A of the cutoff switch 55 Thus, damage to the second FET 55B can be suppressed. In an idling stop vehicle, the engine is started many times, so the battery 50 frequently discharges a large current, and the bypass circuit 150 and cutoff switch 55 are likely to fail. By applying this technology to an idling stop vehicle, failures in the bypass circuit 150 and cutoff switch 55 can be suppressed.

<Other embodiments>
The present invention is not limited to the embodiments described above and illustrated in the drawings; for example, the following embodiments are also included within the technical scope of the present invention.

(1) In the first embodiment, the secondary battery 62 is illustrated as an example of the power storage element. The power storage element is not limited to the secondary battery 62, but may be a capacitor. The secondary battery 62 is not limited to a lithium ion secondary battery, but may be any other non-aqueous electrolyte secondary battery. It is also possible to use lead acid batteries. The power storage elements are not limited to the case where a plurality of power storage elements are connected in series and parallel, but may be connected in series or configured as a single cell.

(2) In the first embodiment described above, the battery 50 is mounted on the four-wheeled motor vehicle 10. As shown in FIG. 11, it may be mounted on a motorcycle 200. 210 is a motorcycle engine. Since the motorcycle 200 requires a smaller installation space than the four-wheeled vehicle 10, the battery 50 is required to be smaller. Furthermore, the current in the motorcycle 200 is often smaller than that in the four-wheeled vehicle 10. According to the present technology, by using the battery 50 in the motorcycle 200, it is possible to use a semiconductor switch (FET) instead of a relay (mechanical switch) as a current interrupt device. There is no need to separately install a diode for FET 55A and FET 55B, and it is possible to downsize the current interrupt device and the battery 50.

(3) In the first embodiment, the battery 50 is used for starting the engine of the automobile 10. The battery 50 may be used for purposes other than engine starting.

(4) In the first embodiment, the cutoff switch 55 is arranged on the negative electrode side (low side) of the assembled battery 60, but it may be arranged on the positive electrode side (high side) of the assembled battery 60.

(5) In the first embodiment, the bypass circuit 150 is provided with the constant current diode 151, but instead of the constant current diode 151, a constant current circuit may be provided. The constant current circuit may be any circuit as long as it has a current I limiting function (constant current function). For example, a circuit may be used that limits the current by detecting the current I and adjusting the amplification factor of the current output transistor.

(6) In the first embodiment, the discharge current I was measured based on the voltage V across the constant current diode 151, but the discharge current I may be measured by the current sensor 53.

(7) In the first embodiment, charging is cut off when the battery 50 is overcharged, but the reason for cutting off charging is not limited to overcharging. For example, charging may be interrupted when battery 50 reaches full charge.

(8) In the first embodiment, when switching the discharge path from the path passing through the bypass circuit 150 to the path passing through the source-drain of the first FET 55A and the second FET 55B of the cut-off switch 55, the cut-off switch 55 is first switched ( S60), the switch 155 of the bypass circuit 150 was switched later (S70), but the switching may be done at the same time or vice versa. Furthermore, the switch 155 of the bypass circuit 150 may be omitted. In this case, the discharge path can be switched by switching the first FET 55A and the second FET 55B on and off.

(9) In the first embodiment described above, the first diode 56A was a parasitic diode of the first FET 55A. The first diode 56A may be a parasitic diode or may be other than a parasitic diode as long as it is connected between the source and drain of the first FET 55A. It may also be a diode connected in parallel to the parasitic diode. The same applies to the second diode 56B.

(10) In the first embodiment, when the discharge current I flowing through the bypass circuit 150 is equal to or greater than the limit value Ia, the management unit 130 switches the first FET 55A and the second FET 55B from off to on, and controls the discharge current between the first FET 55A and the second FET 55B. The discharge took place via the source-drain path of 2FET55B. However, the present invention is not limited to this, and the first FET 55A may be kept off, only the second FET 55B may be switched from off to on, and the discharge current may be discharged through a path passing through the parasitic diode 56A and the source-drain of the second FET 55B.
Which of the two current paths of the cutoff switch 50 is used may be determined depending on the magnitude of the discharge current I. For example, when switching the current path from the bypass circuit 150 to the cutoff switch 50, if the discharge current I is lower than the allowable value of the parasitic diode 56A, the first FET 55A remains off, only the second FET 55B is switched from off to on, and the discharge The current I may be passed through the parasitic diode 56A and the source-drain of the second FET 55B. If the discharge current I is greater than the allowable value of the parasitic diode 56A, it is possible to switch both the first FET 55A and the second FET 55B from off to on and let the discharge current I flow through the source-drain path of the first FET 55A and the second FET 55B. good. The discharge current I may be measured by the current sensor 53 or may be measured using the IV characteristic of the constant current diode 151.

(11) In the first embodiment, the bypass circuit 150 includes the constant current diode 151 and the switch 155. Instead of the constant current diode 151, a current limiting resistor may be used. Although the switch 155 is composed of two FETs 55A and 55B, a contact switch may also be used. Bypass circuit 250 in FIG. 12 includes a current limiting resistor 260 and a contact switch 270. The bypass circuit 250 may include a diode 280 whose discharge direction (direction C in FIG. 12) is the forward direction. Diode 280 can restrict charging through bypass circuit 250.

(12) The present technology can be applied to a control program for a protection circuit of an on-vehicle power storage element. The protection circuit includes a cutoff switch that cuts off the current of the power storage element, and a bypass circuit connected in parallel with the cutoff switch, and the cutoff switch is a first FET and a second FET connected back-to-back, The first FET has a first diode connected between the source and the drain, and the second FET has a second diode connected between the source and the drain in the opposite direction to the first diode, and the second FET has a second diode connected between the source and the drain. The bypass circuit allows discharge from the power storage element to the vehicle while the current is cut off by the cutoff switch. The protection circuit control program causes the computer to execute a process of switching the current path of the discharge current from the bypass circuit to a path passing through the cutoff switch when the discharge current flowing through the bypass circuit exceeds a limit value. This is a program that allows you to The present technology can be applied to a recording medium in which a control program for a protection circuit of a power storage element is recorded. The computer is the management unit 130, for example. The power storage element is, for example, the secondary battery 62. The control program can be recorded on a recording medium such as a ROM.

10 Automobile 50 Battery (power storage device)
51, 52 External terminal 55 Cutoff switch 55A 1st FET
55B 2nd FET
56A parasitic diode (first diode)
56B Parasitic diode (second diode)
60 Assembled battery 62 Secondary battery (power storage element)
120 Protection circuit 130 Management section (control section)
150 Bypass circuit 151 Constant current diode 155 Switch

Claims (6)

An in-vehicle power storage device that does not have a communication function with a vehicle,
In-vehicle power storage element,
A protection circuit for the power storage element for vehicle use,
The protection circuit of the in-vehicle power storage element includes:
a cutoff switch that is provided on a power line of a negative electrode of the power storage element and interrupts the current of the power storage element;
a bypass circuit connected in parallel with the cutoff switch;
including control unit,
The cutoff switch is an N-channel first FET and an N-channel second FET connected back-to-back,
The first FET has a first diode connected between a source and a drain,
The second FET has a second diode connected between a source and a drain, the second diode having a direction opposite to that of the first diode,
The bypass circuit allows discharge from the power storage element to the vehicle while the current is cut off by the cutoff switch,
The control unit includes:
An on-vehicle power storage device that switches a current path of the discharge current from a path passing through the bypass circuit to a path passing through the cutoff switch when the discharge current flowing through the bypass circuit exceeds a limit value. The vehicle-mounted power storage device according to claim 1,
When the discharge current flowing through the bypass circuit exceeds a limit value, the control unit changes the current path of the discharge current from a path passing through the bypass circuit to a source of the first FET and the second FET of the cutoff switch. - An on-vehicle power storage device that switches to a path that passes through the drain. The vehicle-mounted power storage device according to claim 1 or 2,
The bypass circuit is an in-vehicle power storage device including a current limiter that limits current. The vehicle-mounted power storage device according to claim 3,
In the vehicle-mounted power storage device , the current limiter is a constant current element or a constant current circuit. The vehicle-mounted power storage device according to claim 3 or 4,
The current limiting section has a linear region in IV characteristics,
The control unit detects the current of the bypass circuit based on the voltage across the current limiter,
In the vehicle-mounted power storage device , the limit value is a current value within the linear region. The power storage device for a motorcycle according to any one of claims 1 to 5 .

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