Power supply

Abstract

A power supply device according to one embodiment of the present technology comprises: a plurality of secondary battery units that are connected in parallel to each other; and a control unit that controls the electrical discharge of the plurality of secondary battery units. Each of the secondary battery units has a plurality of secondary batteries and a switching unit that switches the connection of the plurality of secondary batteries. The control unit controls the switching unit so as to switch, from a parallel connection to a series connection, the connection between an arbitrary first secondary battery that is from among the plurality of secondary batteries and at least one second secondary battery that is from among the plurality of secondary batteries excluding the first secondary battery.

Description

[Technical field]

[0001] The present technology relates to a power supply device equipped with a plurality of secondary batteries. [Background technology]

[0002] In recent years, with the spread of electric vehicles and hybrid vehicles, and with the spread of power generation devices such as solar power generation and wind power generation, which generate unstable power and require leveling, the demand for various secondary batteries including lithium-ion secondary batteries has been rapidly increasing.

[0003] Incidentally, in a secondary battery, if an internal short circuit occurs due to, for example, an external foreign object (e.g., a nail or a piece of metal) piercing the battery, Joule heat is generated around the short circuit. Depending on the state of Joule heat generation, thermal runaway may occur in the secondary battery. Such an internal short circuit in a secondary battery caused by a foreign object may occur in the case of a collision accident in a secondary battery mounted on a mobile object, or may occur when a foreign object falls onto the secondary battery due to a disaster such as an earthquake. An internal short circuit may also occur due to dendrites.

[0004] As conventional techniques for reducing the risk of fire caused by an internal short circuit, for example, the inventions described in Patent Documents 1 and 2 have been proposed. In the invention described in Patent Document 1, two or more secondary batteries are arranged in parallel, and a secondary battery that has experienced an internal short circuit is subjected to emergency discharge using an MPPT (Maximum Power Point Tracking) circuit so as to maximize the output power. Also, for example, in the invention described in Patent Document 2, a secondary battery that has experienced an internal short circuit is subjected to emergency discharge by connecting it in series to a secondary battery that has not experienced an internal short circuit using a closed circuit. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication WO2018 / 186496 [Patent Document 2] JP 2008-289296 A Summary of the Invention

[0006] However, the method described in Patent Document 2 interrupts the power supply to the electronic device during emergency discharge, and is therefore not suitable for applications in which even a momentary loss of power is unacceptable. Therefore, it is desirable to provide a power supply device that does not interrupt the power supply during emergency discharge.

[0007] A power supply device according to an embodiment of the present technology includes a plurality of secondary battery units connected in parallel to each other, and a control unit that controls the discharge of the plurality of secondary battery units. Each secondary battery unit includes a plurality of secondary batteries and a switching unit that switches the connection of the plurality of secondary batteries. The control unit controls the switching unit to switch the connection between a first secondary battery, which is an arbitrary secondary battery among the plurality of secondary batteries, and one or more second secondary batteries, which are one or more secondary batteries other than the first secondary battery among the plurality of secondary batteries, from a parallel connection to a series connection.

[0008] According to a power supply device according to an embodiment of the present technology, the connection between the first secondary battery and one or more second secondary batteries is switched from a parallel connection to a series connection, so that, for example, when an internal short circuit occurs in the first secondary battery, the discharge current of the secondary battery unit including the first secondary battery in which the internal short circuit has occurred can be flowed into the other secondary battery units. This allows emergency discharge to be performed in the first secondary battery in which the internal short circuit has occurred without interrupting the power supply to the load.

[0009] Note that the effects of the present technology are not necessarily limited to the effects described here, but may be any of a series of effects related to the present technology described below. [Brief description of the drawings]

[0010] [Figure 1] 1 is a diagram illustrating an example of a circuit configuration of a power supply device according to an embodiment of the present technology. [Diagram 2]2 is a diagram illustrating a modified example of the circuit configuration of the power supply device of FIG. [Diagram 3] 1. FIG. 4 is a diagram illustrating an example of an emergency discharge procedure in the power supply device of FIG. [Figure 4] 2 is a diagram illustrating a normal discharge state in the power supply device of FIG. 1. [Diagram 5] FIG. 2 is a simplified diagram showing a normal discharge state. [Figure 6] 2 is a diagram illustrating a state in which a short circuit occurs in the power supply device of FIG. 1. [Figure 7] FIG. 2 is a diagram illustrating a partial series connection in the power supply device of FIG. [Figure 8] FIG. 1 is a simplified diagram showing a partial series connection. [Figure 9] 2 is a diagram showing a state in which a short-circuited portion is isolated in the power supply device of FIG. 1. [Figure 10] FIG. 13 is a simplified diagram showing a state in which a short-circuit point is isolated. [Figure 11] 2 is a diagram showing an example of the change over time in the voltage of each secondary battery and the amount of heat generated in a short-circuited secondary battery when a short circuit occurs in the power supply device of FIG. 1. [Figure 12] 2 is a diagram showing an example of the change over time in the voltage of each secondary battery and the amount of heat generated in a short-circuited secondary battery when a short circuit occurs in the power supply device of FIG. 1. [Figure 13] FIG. 10 is a simplified diagram illustrating a state in which a short circuit occurs in a power supply device according to a comparative example. [Figure 14] 14 is a diagram showing an example of the change over time in voltage of each secondary battery and the amount of heat generated in a short-circuited secondary battery when a short circuit occurs in the power supply device of FIG. 13. [Figure 15] 14 is a diagram showing an example of the change over time in voltage of each secondary battery and the amount of heat generated in a short-circuited secondary battery when a short circuit occurs in the power supply device of FIG. 13. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, embodiments of the present technology will be described in detail with reference to the drawings. The description will be given in the following order. 1. Secondary battery 2. Embodiment

[0012] <1. Secondary battery> First, a secondary battery used in a power supply device according to an embodiment of the present technology will be described.

[0013] The secondary battery used in the present technology may include, for example, a secondary battery exceeding several hundreds of mAh that may actually cause smoke or fire when an internal short circuit occurs. Examples of secondary batteries exceeding several hundreds of mAh include laminated or cylindrical batteries. The charge / discharge principle of the secondary battery used in the present technology is not particularly limited, but the secondary battery used in the present technology is configured to obtain battery capacity by, for example, occlusion and release of an electrode reactant. The secondary battery used in the present technology includes, for example, a positive electrode and a negative electrode as well as an electrolyte. In the secondary battery used in the present technology, for example, in order to prevent deposition of an electrode reactant on the surface of the negative electrode during charging, the charge capacity of the negative electrode is larger than the discharge capacity of the positive electrode. At this time, the electrochemical capacity per unit area of ​​the negative electrode is set to be larger than the electrochemical capacity per unit area of ​​the positive electrode, for example.

[0014] The type of electrode reactant is not particularly limited, but specifically, it is a light metal such as an alkali metal or an alkaline earth metal. The alkali metal is lithium, sodium, potassium, etc., and the alkaline earth metal is beryllium, magnesium, calcium, etc. A secondary battery that obtains battery capacity by utilizing the absorption and release of lithium is a so-called lithium ion secondary battery. In this lithium ion secondary battery, lithium is absorbed and released in an ionic state.

[0015] Next, problems with the secondary battery used in the present technology will be described.

[0016] In the secondary battery used in the present technology, for example, when a short circuit (hereinafter referred to as "internal short circuit") occurs between the positive and negative electrodes due to the penetration of a foreign object (e.g., a nail or a piece of metal) from the outside, Joule heat is generated around the short circuit. Depending on the state of the generation of this Joule heat, thermal runaway may occur in the secondary battery. Such an internal short circuit in a secondary battery caused by a foreign object may occur in the case of a collision accident in a secondary battery mounted on a mobile object, or may occur when a foreign object falls onto the secondary battery due to a disaster such as an earthquake. An internal short circuit may also occur due to dendrites.

[0017] When localized heat is generated due to an internal short circuit, there is a very short time before the temperature exceeds the thermal decomposition temperature or ignition temperature of the secondary battery material. The most effective way to prevent ignition, which has such a short time window, is to suppress the Joule heat generated at the location where the internal short circuit occurred. To achieve this, when an internal short circuit is detected, an emergency discharge should be performed immediately on the secondary battery where the internal short circuit occurred, and the current flowing into the secondary battery where the internal short circuit occurred should be suppressed.

[0018] As conventional techniques for reducing the risk of fire caused by an internal short circuit, for example, the inventions described in Patent Documents 1 and 2 have been proposed. In the invention described in Patent Document 1, two or more secondary batteries are arranged in parallel, and a secondary battery that has experienced an internal short circuit is subjected to emergency discharge using an MPPT (Maximum Power Point Tracking) circuit so as to maximize the output power. Also, for example, in the invention described in Patent Document 2, a secondary battery that has experienced an internal short circuit is subjected to emergency discharge by connecting it in series to a secondary battery that has not experienced an internal short circuit using a closed circuit.

[0019] However, in the method described in Patent Document 1, it is difficult to miniaturize the MPPT circuit, and the cost is high. In addition, in the method described in Patent Document 2, the power supply to the electronic device is interrupted during emergency discharge, so it is not suitable for applications where even a momentary loss of power cannot be tolerated. Therefore, the inventor of the present application proposes below a power supply device that is easy to miniaturize and does not interrupt the power supply during emergency discharge.

[0020] <2. Embodiment> [composition] Next, a configuration of the power supply device 100 according to an embodiment of the present technology will be described.

[0021] FIG. 1 shows an example of a circuit configuration of a power supply device 100 according to the present embodiment. The power supply device 100 includes, for example, two secondary battery units 110, 120 connected in parallel to each other as shown in FIG. 1. When the two secondary battery units 110, 120 connected in parallel to each other are configured as a secondary battery module 100A, the power supply device 100 may include, for example, two secondary battery modules 100A connected in parallel to each other as shown in FIG. 2. When the two secondary battery modules 100A connected in parallel to each other are configured as a secondary battery module 100B, the power supply device 100 may include, for example, two secondary battery modules 100B connected in series to each other as shown in FIG. 2.

[0022] In the power supply device 100, the number of secondary battery units connected in parallel to each other is not limited to two, but may be three or more. In the power supply device 100, the number of secondary battery modules 100A connected in parallel to each other is not limited to two, but may be three or more. In the power supply device 100, the number of secondary battery modules 100A connected in series to each other is not limited to two, but may be three or more.

[0023] 1, the power supply device 100 further includes a control unit 130 that controls the discharge of the two secondary battery units 110, 120. The control unit 130 includes, for example, a central processing unit (CPU) that executes predetermined arithmetic processing, a read only memory (ROM) that stores a predetermined control program, and a random access memory (RAM) that temporarily stores data, and controls the discharge of the two secondary battery units 110, 120 by executing the control program stored in the ROM.

[0024] (Secondary battery unit 110) The secondary battery unit 110 has, for example, three secondary batteries Ba, Bb, and Bc, and three sensors Sa, Sb, and Sc. The sensor Sa is connected in series with the secondary battery Ba, or is installed near the wiring connected to the positive or negative electrode of the secondary battery Ba. The sensor Sb is connected in series with the secondary battery Bb, or is installed near the wiring connected to the positive or negative electrode of the secondary battery Bb. The sensor Sc is connected in series with the secondary battery Bc, or is installed near the wiring connected to the positive or negative electrode of the secondary battery Bc.

[0025] The secondary battery unit 110 further includes, for example, four field effect transistors (FETs) Ta1, Ta2, Ta3, and Ta4 connected in series with the secondary battery Ba. The secondary battery unit 110 further includes, for example, four field effect transistors (FETs) Tb1, Tb2, Tb3, and Tb4 connected in series with the secondary battery Bb. The secondary battery unit 110 further includes, for example, four field effect transistors (FETs) Tc1, Tc2, Tc3, and Tc4 connected in series with the secondary battery Bc. Note that the number of secondary batteries in the secondary battery unit 110 is not limited to three, and may be two, or may be four or more.

[0026] The field effect transistors Ta1 and Ta2 are provided on the positive electrode side of the secondary battery Ba, and the field effect transistors Ta3 and Ta4 are provided on the negative electrode side of the secondary battery Ba. The drain of the field effect transistor Ta1 and the source of the field effect transistor Ta2 are connected to each other. The connection point between the drain of the field effect transistor Ta1 and the source of the field effect transistor Ta2 is connected to the positive electrode of the secondary battery Ba directly or via a sensor Sa. The drain of the field effect transistor Ta3 and the source of the field effect transistor Ta4 are connected to each other. The connection point between the drain of the field effect transistor Ta3 and the source of the field effect transistor Ta4 is connected to the negative electrode of the secondary battery Ba directly or via a sensor Sa.

[0027] The field effect transistors Tb1 and Tb2 are provided on the positive electrode side of the secondary battery Bb, and the field effect transistors Tb3 and Tb4 are provided on the negative electrode side of the secondary battery Bb. The drain of the field effect transistor Tb1 and the source of the field effect transistor Tb2 are connected to each other. The connection point between the drain of the field effect transistor Tb1 and the source of the field effect transistor Tb2 is connected to the positive electrode of the secondary battery Bb directly or via a sensor Sb. The drain of the field effect transistor Tb3 and the source of the field effect transistor Tb4 are connected to each other. The connection point between the drain of the field effect transistor Tb3 and the source of the field effect transistor Tb4 is connected to the negative electrode of the secondary battery Bb directly or via a sensor Sb.

[0028] The field effect transistors Tc1 and Tc2 are provided on the positive electrode side of the secondary battery Bc, and the field effect transistors Tc3 and Tc4 are provided on the negative electrode side of the secondary battery Bc. The drain of the field effect transistor Tc1 and the source of the field effect transistor Tc2 are connected to each other. The connection point between the drain of the field effect transistor Tc1 and the source of the field effect transistor Tc2 is connected to the positive electrode of the secondary battery Bc directly or via a sensor Sc. The drain of the field effect transistor Tc3 and the source of the field effect transistor Tc4 are connected to each other. The connection point between the drain of the field effect transistor Tc3 and the source of the field effect transistor Tc4 is connected to the negative electrode of the secondary battery Bc directly or via a sensor Sc.

[0029] The secondary battery unit 110 further includes, for example, one field effect transistor Tg. The source of the field effect transistor Tg is connected to the sources of the field effect transistors Ta1, Tb1, and Tc1 and the drains of the field effect transistors Ta4, Tb4, and Tc4. The drain of the field effect transistor Tg is connected to the drains of the field effect transistors Ta2, Tb2, and Tc2 and the positive terminal P1 of the power supply device 100. The sources of the field effect transistors Ta2, Tb2, and Tc2 are connected to the negative terminal P2 of the power supply device 100.

[0030] (Secondary battery unit 120) The secondary battery unit 120 has, for example, three secondary batteries Bd, Be, and Bf and three sensors Sd, Se, and Sf. The sensor Sd is connected in series with the secondary battery Bd or is installed near the wiring connected to the positive or negative electrode of the secondary battery Bd. The sensor Se is connected in series with the secondary battery Be or is installed near the wiring connected to the positive or negative electrode of the secondary battery Be. The sensor Sf is connected in series with the secondary battery Bf or is installed near the wiring connected to the positive or negative electrode of the secondary battery Bf.

[0031] The secondary battery unit 120 further includes, for example, four field effect transistors (FETs) Td1, Td2, Td3, and Td4 connected in series with the secondary battery Bd. The secondary battery unit 120 further includes, for example, four field effect transistors (FETs) Te1, Te2, Te3, and Te4 connected in series with the secondary battery Be. The secondary battery unit 120 further includes, for example, four field effect transistors (FETs) Tf1, Tf2, Tf3, and Tf4 connected in series with the secondary battery Bf. Note that the number of secondary batteries in the secondary battery unit 120 is not limited to three, and may be two, or may be four or more.

[0032] The field effect transistors Td1 and Td2 are provided on the positive electrode side of the secondary battery Bd, and the field effect transistors Td3 and Td4 are provided on the negative electrode side of the secondary battery Bd. The drain of the field effect transistor Td1 and the source of the field effect transistor Td2 are connected to each other. The connection point between the drain of the field effect transistor Td1 and the source of the field effect transistor Td2 is connected to the positive electrode of the secondary battery Bd directly or via a sensor Sd. The drain of the field effect transistor Td3 and the source of the field effect transistor Td4 are connected to each other. The connection point between the drain of the field effect transistor Td3 and the source of the field effect transistor Td4 is connected to the negative electrode of the secondary battery Bd directly or via a sensor Sd.

[0033] The field effect transistors Te1 and Te2 are provided on the positive electrode side of the secondary battery Be, and the field effect transistors Te3 and Te4 are provided on the negative electrode side of the secondary battery Be. The drain of the field effect transistor Te1 and the source of the field effect transistor Te2 are connected to each other. The connection point between the drain of the field effect transistor Te1 and the source of the field effect transistor Te2 is connected to the positive electrode of the secondary battery Be directly or via a sensor Se. The drain of the field effect transistor Te3 and the source of the field effect transistor Te4 are connected to each other. The connection point between the drain of the field effect transistor Te3 and the source of the field effect transistor Te4 is connected to the negative electrode of the secondary battery Be directly or via a sensor Se.

[0034] The field effect transistors Tf1 and Tf2 are provided on the positive electrode side of the secondary battery Bf, and the field effect transistors Tf3 and Tf4 are provided on the negative electrode side of the secondary battery Bf. The drain of the field effect transistor Tf1 and the source of the field effect transistor Tf2 are connected to each other. The connection point between the drain of the field effect transistor Tf1 and the source of the field effect transistor Tf2 is connected to the positive electrode of the secondary battery Bf directly or via a sensor Sf. The drain of the field effect transistor Tf3 and the source of the field effect transistor Tf4 are connected to each other. The connection point between the drain of the field effect transistor Tf3 and the source of the field effect transistor Tf4 is connected to the negative electrode of the secondary battery Bf directly or via a sensor Sf.

[0035] The secondary battery unit 120 further includes, for example, one field effect transistor Th. The source of the field effect transistor Th is connected to the sources of the field effect transistors Td1, Te1, and Tf1 and the drains of the field effect transistors Td4, Te4, and Tf4. The drain of the field effect transistor Th is connected to the drains of the field effect transistors Td2, Te2, and Tf2 and the positive terminal P1 of the power supply device 100. The sources of the field effect transistors Td2, Te2, and Tf2 are connected to the negative terminal P2 of the power supply device 100.

[0036] The sensor Sa is a sensor that detects a physical quantity that serves as a clue for detecting an internal short circuit in the secondary battery Ba and outputs a signal indicating the physical quantity to the control unit 130. The sensor Sa is, for example, an ammeter that detects a current flowing through a shunt resistor connected in series to the secondary battery Ba. The sensor Sa may be configured to detect a physical quantity having a predetermined correlation with the current flowing through the shunt resistor, and may be, for example, a voltmeter that detects the voltage of the shunt resistor, or a magnetometer that detects a magnetic field generated by a wiring connected to the positive electrode or negative electrode of the secondary battery Ba.

[0037] The sensor Sb is a sensor that detects a physical quantity that serves as a clue for detecting an internal short circuit in the secondary battery Bb and outputs a signal indicating the physical quantity to the control unit 130. The sensor Sb is, for example, an ammeter that detects a current flowing through a shunt resistor connected in series to the secondary battery Bb. The sensor Sb may be configured to detect a physical quantity having a predetermined correlation with the current flowing through the shunt resistor, and may be, for example, a voltmeter that detects the voltage of the shunt resistor, or a magnetometer that detects a magnetic field generated by a wiring connected to the positive electrode or negative electrode of the secondary battery Bb.

[0038] The sensor Sc is a sensor that detects a physical quantity that serves as a clue for detecting an internal short circuit in the secondary battery Bc and outputs a signal indicating the physical quantity to the control unit 130. The sensor Sc is, for example, an ammeter that detects a current flowing through a shunt resistor connected in series to the secondary battery Bc. The sensor Sc may be configured to detect a physical quantity having a predetermined correlation with the current flowing through the shunt resistor, and may be, for example, a voltmeter that detects the voltage of the shunt resistor, or a magnetometer that detects a magnetic field generated by a wiring connected to the positive electrode or negative electrode of the secondary battery Bc.

[0039] The sensor Sd is a sensor that detects a physical quantity that serves as a clue for detecting an internal short circuit in the secondary battery Bd and outputs a signal indicating the physical quantity to the control unit 130. The sensor Sd is, for example, an ammeter that detects a current flowing through a shunt resistor connected in series to the secondary battery Bd. The sensor Sd may be configured to detect a physical quantity that has a predetermined correlation with the current flowing through the shunt resistor, and may be, for example, a voltmeter that detects the voltage of the shunt resistor, or a magnetometer that detects a magnetic field generated by a wiring connected to the positive electrode or negative electrode of the secondary battery Bd.

[0040] The sensor Se is a sensor that detects a physical quantity that serves as a clue for detecting an internal short circuit in the secondary battery Be and outputs a signal indicating the physical quantity to the control unit 130. The sensor Se is, for example, an ammeter that detects a current flowing through a shunt resistor connected in series to the secondary battery Be. The sensor Se may be configured to detect a physical quantity having a predetermined correlation with the current flowing through the shunt resistor, and may be, for example, a voltmeter that detects the voltage of the shunt resistor, or a magnetometer that detects a magnetic field generated by a wiring connected to the positive electrode or negative electrode of the secondary battery Be.

[0041] The sensor Sf is a sensor that detects a physical quantity that serves as a clue for detecting an internal short circuit in the secondary battery Bf and outputs a signal indicating the physical quantity to the control unit 130. The sensor Sf is, for example, an ammeter that detects a current flowing through a shunt resistor connected in series to the secondary battery Bf. The sensor Sf may be configured to detect a physical quantity having a predetermined correlation with the current flowing through the shunt resistor, and may be, for example, a voltmeter that detects the voltage of the shunt resistor, or a magnetometer that detects a magnetic field generated by a wiring connected to the positive electrode or negative electrode of the secondary battery Bf.

[0042] [Operation] Next, the operation of power supply device 100 according to the present embodiment will be described.

[0043] FIG. 3 shows an example of an emergency discharge procedure in the power supply device 100. First, the control unit 130 performs initial settings of each field effect transistor (Ta1 to Th) (step S101). The control unit 130 performs initial settings of each field effect transistor (Ta1 to Th) so that the secondary batteries Ba to Bf are connected in parallel with each other, for example, as shown in FIG. 4 and FIG. 5. The control unit 130 turns on, for example, the field effect transistors Ta1, Ta3, Tb1, Tb3, Tc1, Tc3, Td1, Td3, Te1, Te3, Tf1, Tf3, Tg, and Th. The control unit 130 further turns off, for example, the field effect transistors Ta2, Ta4, Tb2, Tb4, Tc2, Tc4, Td2, Td4, Te2, Te4, Tf2, and Tf4.

[0044] After the above-mentioned initial setting is completed, the control unit 130 detects whether or not an internal short circuit has occurred in any of the secondary batteries Ba to Bf using the detection results of the sensors Sa to Sf (step S102). When the sensors Sa to Sf are current sensors, it is assumed that a short circuit has occurred in the secondary battery Bf, for example, as shown in FIG. 6. At this time, a current output from the secondary batteries Ba to Be that are not short-circuited flows into the secondary battery Bf where a short circuit has occurred, for example, as shown in FIG. 6. At this time, the sensor Sf detects the current flowing into the secondary battery Bf, and outputs the detection result to the control unit 130.

[0045] Based on the detection result input from the sensor Sf, the control unit 130 determines that a short circuit has occurred in the secondary battery Bf (step S102; Y), and performs emergency discharge (step S103). When performing the emergency discharge, the control unit 130 controls the field effect transistors Ta1 to Th to switch the connection between the secondary battery Bf in which a short circuit has occurred and the secondary batteries Bd and Be in which no short circuit has occurred from a parallel connection to a series connection. For example, the control unit 130 turns off the field effect transistors Tf1 and Tf3, then turns off the field effect transistor Th, and turns on the field effect transistors Tf2 and Tf4. As a result, for example, as shown in FIGS. 7 and 8, the secondary battery Bf in which a short circuit has occurred is connected in series to the secondary batteries Bd and Be in which no short circuit has occurred, and the positive electrode of the secondary battery Bf is connected to the positive electrode terminal P1 of the power supply device 100.

[0046] At this time, when the secondary battery Bf is connected in series to the secondary batteries Bd and Be, the voltage V2 of the entire secondary battery unit 120 becomes larger than the voltage V1 of the entire secondary battery unit 110 by the voltage of the secondary battery Bf. As a result, current inflow from the secondary battery unit 120 to the secondary battery unit 110 is started. That is, the discharge of the secondary battery unit 120 is started and the charging of the secondary battery unit 110 is started. Then, until V2 = V1, the discharge of the secondary battery unit 120 and the charging of the secondary battery unit 110 are continued. After that, when V2 < V1, current inflow from the secondary battery unit 110 to the secondary battery unit 120 is started. That is, in the secondary battery unit 110, the direction of current flow is reversed.

[0047] Based on the detection result input from the sensor Sf, when the control unit 130 determines that the direction of the current flowing through the secondary battery Bf in which a short circuit has occurred has reversed (step S104; Y), the control unit 130 isolates the short circuit location (step S105). For example, the control unit 130 turns off the field effect transistors Tf2 and Tf4, and then turns on the field effect transistor Th to separate the secondary battery Bf in which a short circuit has occurred from the current paths of the secondary batteries Bd and Be in which no short circuit has occurred, as shown in FIGS. 9 and 10, for example.

[0048] The timing for isolating the short-circuited secondary battery Bf is not limited to when the direction of the current flowing through the short-circuited secondary battery Bf is reversed. For example, the control unit 130 may isolate the short-circuited portion when it determines that the magnitude of the current flowing through the short-circuited secondary battery Bf is equal to or less than a predetermined threshold based on the detection result input from the sensor Sf. Also, the control unit 130 may isolate the short-circuited portion when a predetermined time has elapsed since partial serialization was performed.

[0049] In the above manner, emergency discharge is performed in the power supply device 100. Incidentally, this emergency discharge operation is realized by a plurality of field effect transistors Ta1 to Th. Therefore, there is no need to use an MPPT circuit, and the emergency discharge operation can be realized with small elements. Furthermore, emergency discharge can be performed without interruption of the current supply from the power supply device 100 to an external load. Therefore, there is no risk of the power supply device 100 losing its function even during emergency discharge.

[0050] Figures 11 and 12 show an example of the voltages of the secondary batteries Ba to Bf and the change over time in the amount of heat generated by the short-circuited secondary battery Bf when a short circuit occurs in the power supply device 100. The horizontal axis in Figure 11 is in ms, and the horizontal axis in Figure 12 is in min. Figures 11 and 12 show the results of an evaluation of the effectiveness of the power supply device 100 using an electronic circuit simulator.

[0051] In the electronic circuit simulator, when describing the secondary batteries Ba to Bf, a capacitor with a capacitance of 4kF (initial voltage 4V, internal resistance 30mΩ, parasitic inductance 10nH) was used instead of a voltage source. This is because a voltage source can draw out an unlimited amount of current and has no concept of capacity. A capacitor with a capacitance of 4kF was used to reproduce the behavior of the secondary batteries Ba to Bf decreasing in voltage due to discharge. In the electronic circuit simulator, the total energy held by the secondary batteries Ba to Bf was set to 32kJ x 6 = 192kJ, and a constant power load of 10W was connected to each secondary battery Ba to Bf. In other words, it was assumed that power was constantly being supplied to the load.

[0052] In the electronic circuit simulator, an internal short circuit was generated in the secondary battery Bf at an elapsed time of 5 ms. Specifically, a separate resistor was connected in parallel to the secondary battery Bf, and the resistance value of this resistor was reduced from 1 MΩ to 30 mΩ at an elapsed time of 5 ms. A simulation was then performed on the amount of heat generated (in kJ) by this resistor when it was partially serially connected (see Figure 8) and when it was not partially serially connected (see Figure 13). The results when it was partially serially connected are shown in Figures 11 and 12, and the results when it was not partially serially connected are shown in Figures 14 and 15.

[0053] When partial serialization was not performed, the voltages of all of the secondary batteries Ba to Bf decreased at the 5 ms boundary, as shown in Fig. 14. This is because all of the energy of the secondary batteries Ba to Bf flows into the secondary battery Bf where an internal short circuit has occurred. As shown in Fig. 15, at the point where 12 minutes has elapsed, 130 kJ of energy, equivalent to about 68% of the total energy, has become heat in the secondary battery Bf where an internal short circuit has occurred.

[0054] On the other hand, when the batteries were connected in partial series, only the secondary battery Bf in which an internal short circuit occurred was subjected to emergency discharge as shown in FIG. 11. Then, as shown in FIG. 12, after sufficient discharging, the secondary battery Bf was isolated. As a result of this control, the amount of heat generated by the secondary battery Bf in which an internal short circuit occurred was 7.2 kJ at 12 minutes elapsed. This indicates that the amount of heat generated by the secondary battery Bf in which an internal short circuit occurred was reduced by 94% compared to when the batteries were not connected in partial series. In addition, as shown in FIG. 11 and FIG. 12, there is no interruption in the current flowing through the secondary batteries Ba to Be. Therefore, it can be seen that power is constantly being supplied to the load.

[0055] [effect] Next, the effects of the power supply device 100 according to this embodiment will be described.

[0056] In this embodiment, the connection between the secondary battery Bf and the secondary batteries Bd, Be can be switched from a parallel connection to a series connection. This allows, for example, when an internal short circuit occurs in the secondary battery Bf, the discharge current of the secondary battery unit 120 including the secondary battery Bf in which the internal short circuit has occurred to flow into the other secondary battery units 110. As a result, emergency discharge can be performed in the secondary battery Bf in which the internal short circuit has occurred without interrupting the power supply to the load.

[0057] In this embodiment, sensors Sa to Sf are provided to detect currents flowing through the respective secondary batteries Ba to Bf, and the connection between the secondary battery Bf and the secondary batteries Bd, Be can be switched from parallel connection to series connection based on the detection results of the sensors Sa to Sf. This allows, for example, when an internal short circuit occurs in the secondary battery Bf, the discharge current of the secondary battery unit 120 including the secondary battery Bf with the internal short circuit to flow into the other secondary battery units 110. As a result, emergency discharge can be performed in the secondary battery Bf with the internal short circuit without interrupting the power supply to the load.

[0058] In this embodiment, after emergency discharge, the secondary battery Bf in which an internal short circuit has occurred is separated from the current paths of the secondary batteries Bd and Be in which no internal short circuit has occurred. This eliminates the risk of charging the secondary battery Bf in which an internal short circuit has occurred, making it possible to prevent thermal runaway from occurring in the secondary battery Bf.

[0059] In this embodiment, the secondary battery Bf is connected to the secondary batteries Bd and Be by a plurality of field effect transistors Ta1 to Th. This eliminates the need for an MPPT circuit in emergency discharge, making it possible to reduce the size of the power supply device 100.

[0060] The effects described in this specification are merely examples, and the effects of the present technology are not limited to the effects described in this specification. Therefore, other effects may be obtained with respect to the present technology.

Claims

1. A secondary battery unit, A control unit that controls discharging of the secondary battery unit; Equipped with The secondary battery unit includes: A plurality of secondary batteries; A switching unit that switches connections of the plurality of secondary batteries; a sensor for detecting a current flowing through each of the secondary batteries or a physical quantity having a predetermined correlation with the current; having When the control unit determines, based on a detection result of the sensor, that a short circuit has occurred in a first secondary battery, which is an arbitrary secondary battery among the plurality of secondary batteries, the control unit controls the switching unit to switch a connection between the first secondary battery and one or more second secondary batteries, which are one or more secondary batteries other than the first secondary battery among the plurality of secondary batteries, from a parallel connection to a series connection. power supply.

2. A secondary battery unit, A control unit that controls discharging of the secondary battery unit; Equipped with The secondary battery unit includes: A plurality of secondary batteries; A switching unit that switches connections of the plurality of secondary batteries; a sensor for detecting a current flowing through each of the secondary batteries or a physical quantity having a predetermined correlation with the current; having The control unit controls the switching unit based on the detection result of the sensor to switch a connection between a first secondary battery, which is an arbitrary secondary battery among the plurality of secondary batteries, and one or more second secondary batteries, which are one or more secondary batteries other than the first secondary battery among the plurality of secondary batteries, from a parallel connection to a series connection, and then isolates the first secondary battery from a current path of the one or more second secondary batteries. power supply.

3. When the control unit determines that the direction of the current flowing through the first secondary battery has reversed based on the detection result of the sensor, the control unit controls the switching unit to separate the first secondary battery from the current path of the one or more second secondary batteries.

2. The power supply device of claim 1.

4. The switching unit includes a plurality of transistors. The power supply device according to any one of claims 1 to 3.

5. the switching unit has first to fourth transistors for each of the secondary batteries, and further has a fifth transistor provided in common to the plurality of secondary batteries; a drain of the first transistor and a source of the second transistor are connected to each other, and a connection point between the drain of the first transistor and the source of the second transistor is connected to a positive electrode of the secondary battery; a source of the first transistor is connected to a source of the first transistor provided for another of the secondary batteries and to a source of the fifth transistor; a drain of the second transistor is connected to a drain of the second transistor provided for another of the secondary batteries and to a drain of the fifth transistor; a drain of the third transistor and a source of the fourth transistor are connected to each other, and a connection point between the drain of the third transistor and the source of the fourth transistor is connected to a negative electrode of the secondary battery; a source of the third transistor is connected to a source of the third transistor provided for another of the secondary batteries; The drain of the fourth transistor is connected to the drain of the fourth transistor provided for the other secondary battery and to the source of the fifth transistor. The power supply device according to any one of claims 1 to 3.

6. Further comprising another secondary battery unit connected in parallel to the secondary battery unit, a source of the fifth transistor is connected to a source of the fifth transistor provided for another of the secondary battery units; The source of the third transistor is connected to the source of the third transistor provided for the other secondary battery unit.

6. The power supply device according to claim 5.

7. A plurality of secondary battery units connected in parallel with each other; a control unit for controlling discharging of the plurality of secondary battery units; Equipped with Each of the secondary battery units is A plurality of secondary batteries; A switching unit that switches connections of the plurality of secondary batteries; a sensor for detecting a current flowing through each of the secondary batteries or a physical quantity having a predetermined correlation with the current; having When the control unit determines, based on a detection result of the sensor, that a short circuit has occurred in a first secondary battery, which is an arbitrary secondary battery among the plurality of secondary batteries, the control unit controls the switching unit to switch a connection between the first secondary battery and one or more second secondary batteries, which are one or more secondary batteries other than the first secondary battery among the plurality of secondary batteries, from a parallel connection to a series connection. power supply.

8. A plurality of secondary battery units connected in parallel with each other; a control unit for controlling discharging of the plurality of secondary battery units; Equipped with Each of the secondary battery units is A plurality of secondary batteries; A switching unit that switches connections of the plurality of secondary batteries; a sensor for detecting a current flowing through each of the secondary batteries or a physical quantity having a predetermined correlation with the current; having The control unit controls the switching unit based on the detection result of the sensor to switch a connection between a first secondary battery, which is an arbitrary secondary battery among the plurality of secondary batteries, and one or more second secondary batteries, which are one or more secondary batteries other than the first secondary battery among the plurality of secondary batteries, from a parallel connection to a series connection, and then isolates the first secondary battery from a current path of the one or more second secondary batteries. power supply.

9. When the control unit determines that the direction of the current flowing through the first secondary battery has been reversed based on the detection result of the sensor, the control unit controls the switching unit to separate the first secondary battery from a current path of the one or more second secondary batteries.

8. The power supply device of claim 7.

10. The switching unit is configured to include a plurality of transistors. The power supply device according to any one of claims 7 to 9.

11. The switching unit has first to fourth transistors for each of the secondary batteries, and further has a fifth transistor provided in common to the plurality of secondary batteries; a drain of the first transistor and a source of the second transistor are connected to each other, and a connection point between the drain of the first transistor and the source of the second transistor is connected to a positive electrode of the secondary battery; a source of the first transistor is connected to a source of the first transistor provided for another of the secondary batteries and to a source of the fifth transistor; a drain of the second transistor is connected to a drain of the second transistor provided for another of the secondary batteries and to a drain of the fifth transistor; a drain of the third transistor and a source of the fourth transistor are connected to each other, and a connection point between the drain of the third transistor and the source of the fourth transistor is connected to a negative electrode of the secondary battery; a source of the third transistor is connected to a source of the third transistor provided for another of the secondary batteries; The drain of the fourth transistor is connected to the drain of the fourth transistor provided for the other secondary battery and to the source of the fifth transistor. The power supply device according to any one of claims 7 to 9.

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