Secondary battery protection circuit and battery pack

Abstract

The present application improves the consumption efficiency of power supplied to a load. A secondary battery protection circuit outputs a first output voltage corresponding to the voltage of a first secondary battery from between a first terminal and a second terminal to a first load in a state in which a first switching circuit and a second switching circuit are turned on, outputs a third output voltage obtained by adding a second output voltage corresponding to the voltage of a second secondary battery to the first output voltage from between the first terminal and a third terminal to a second load, stops the output of the first output voltage from between the first terminal and the second terminal to the first load and stops the output of the third output voltage from between the first terminal and the third terminal in a state in which the first switching circuit is turned off and the second switching circuit is turned on, outputs the first output voltage from between the first terminal and the second terminal to the first load and stops the output of the third output voltage from between the first terminal and the third terminal in a state in which the first switching circuit is turned on and the second switching circuit is turned off.

Description

[0001] This application is a divisional application of patent application filed on November 25, 2019, with application number 201911166939.4 and invention title "Secondary Battery Protection Circuit and Battery Pack". Technical Field

[0002] This invention relates to a secondary battery protection circuit and a battery pack. Background Technology

[0003] Previously, it was known that battery packs had a protection circuit that stopped outputting the voltage across the terminals of these secondary batteries to a load when an abnormality was detected in multiple secondary batteries connected in series (for example, see Patent Document 1).

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2012-9399.

[0007] However, in existing technologies where the battery pack outputs only one voltage value to the load, if the load requires two voltage values, the voltage value needs to be converted to both voltage values ​​on the load side. As a result, power conversion losses occur on the load side, reducing the efficiency of power consumption from the battery pack to the load side. Summary of the Invention

[0008] Therefore, this disclosure provides a secondary battery protection circuit and a battery pack that can improve the power consumption efficiency supplied to the load side.

[0009] This disclosure provides a secondary battery protection circuit that protects a first secondary battery and a second secondary battery connected in series, respectively. The secondary battery protection circuit includes:

[0010] First terminal;

[0011] Second terminal;

[0012] Third terminal;

[0013] The first switching circuit is connected in series between the negative terminal of the first secondary battery and the first terminal in the current path.

[0014] The second switching circuit is inserted in series into the current path between the negative terminal of the second secondary battery and the second terminal, or into the current path between the positive terminal of the second secondary battery and the third terminal.

[0015] The first protection IC, by disconnecting the first switching circuit, at least protects the first secondary battery from over-discharge or overcurrent discharge; and

[0016] The second protection IC, by disconnecting the second switching circuit, at least protects the second secondary battery from over-discharge or overcurrent discharge.

[0017] When the first switching circuit is turned on by the first protection IC and the second switching circuit is turned on by the second protection IC, a first output voltage corresponding to the voltage of the first secondary battery is output from between the first terminal and the second terminal to the first load, and a third output voltage obtained by adding the first output voltage to the second output voltage corresponding to the voltage of the second secondary battery is output from between the first terminal and the third terminal to the second load.

[0018] When the first switching circuit is disconnected by the first protection IC and the second switching circuit is turned on by the second protection IC, the output of the first output voltage from the first terminal to the first load and the output of the third output voltage from the first terminal to the third terminal are both stopped.

[0019] When the first switching circuit is turned on by the first protection IC and the second switching circuit is turned off by the second protection IC, the first output voltage is output from between the first terminal and the second terminal to the first load, and the output of the third output voltage from between the first terminal and the third terminal is stopped.

[0020] In addition, this disclosure provides a battery pack comprising:

[0021] A first secondary battery and a second secondary battery connected in series;

[0022] First terminal;

[0023] Second terminal;

[0024] Third terminal;

[0025] The first switching circuit is inserted in series into the current path between the negative terminal of the first secondary battery and the first terminal, or into the current path between the positive terminal of the first secondary battery and the second terminal.

[0026] The second switching circuit is inserted in series into the current path between the negative terminal of the second secondary battery and the second terminal, or into the current path between the positive terminal of the second secondary battery and the third terminal.

[0027] The first protection IC, by disconnecting the first switching circuit, at least protects the first secondary battery from over-discharge or overcurrent discharge; and

[0028] The second protection IC, by disconnecting the second switching circuit, at least protects the second secondary battery from over-discharge or overcurrent discharge.

[0029] When the first switching circuit is turned on by the first protection IC and the second switching circuit is turned on by the second protection IC, a first output voltage corresponding to the voltage of the first secondary battery is output from between the first terminal and the second terminal to the first load, and a third output voltage obtained by adding the first output voltage to the second output voltage corresponding to the voltage of the second secondary battery is output from between the first terminal and the third terminal to the second load.

[0030] When the first switching circuit is disconnected by the first protection IC and the second switching circuit is turned on by the second protection IC, the output of the first output voltage from between the first terminal and the second terminal to the first load is stopped, and the output of the third output voltage from between the first terminal and the third terminal is stopped.

[0031] When the first switching circuit is turned on by the first protection IC and the second switching circuit is turned off by the second protection IC, the first output voltage is output from between the first terminal and the second terminal to the first load, and the output of the third output voltage from between the first terminal and the third terminal is stopped.

[0032] Invention Effects

[0033] According to the technology disclosed herein, a secondary battery protection circuit and a battery pack can be provided that can improve the power consumption efficiency supplied to the load side. Attached Figure Description

[0034] Figure 1 This is a diagram illustrating the structure of a battery pack in one comparative method.

[0035] Figure 2 This diagram illustrates a situation in a battery pack in a comparative configuration where a discharge overcurrent is detected by a protection IC on the low-potential side.

[0036] Figure 3 This diagram illustrates a situation in a battery pack in a comparative configuration where a discharge overcurrent is detected by a protection IC on the high-potential side.

[0037] Figure 4 This diagram illustrates a situation in a battery pack in a comparative configuration where over-discharge of the secondary battery on the low-potential side is detected by the protection IC on the low-potential side.

[0038] Figure 5This diagram illustrates a situation in a battery pack in a comparative configuration where over-discharge of the secondary battery on the high-potential side is detected by the protection IC on the high-potential side.

[0039] Figure 6 This diagram illustrates the situation in the battery pack of the first embodiment where the discharge overcurrent is detected by the protection IC on the high-potential side.

[0040] Figure 7 This is a timeline illustrating the state before and after the overcurrent discharge is detected by the protection IC on the high-potential side in the battery pack of the first embodiment.

[0041] Figure 8 This diagram illustrates the situation in the battery pack of the first embodiment where the discharge overcurrent is detected by the protection IC on the low potential side.

[0042] Figure 9 This is a timeline illustrating the situation before and after the discharge overcurrent is detected by the protection IC on the low potential side in the battery pack of the first embodiment.

[0043] Figure 10 This diagram illustrates the situation in the battery pack of the second embodiment where the discharge overcurrent is detected by the protection IC on the high-potential side.

[0044] Figure 11 This diagram illustrates the situation in the battery pack of the second embodiment where the discharge overcurrent is detected by the protection IC on the high-potential side.

[0045] Figure 12 This diagram illustrates the situation in the battery pack of the second embodiment where the discharge overcurrent is detected by the protection IC on the low potential side.

[0046] Figure 13 This is a timeline illustrating the situation before and after the discharge overcurrent is detected by the protection IC on the low potential side in the battery pack of the second embodiment.

[0047] Figure 14 This diagram illustrates the situation in the battery pack of the third embodiment where the discharge overcurrent is detected by the protection IC on the low potential side.

[0048] Figure 15 This diagram illustrates the situation in the battery pack of the third embodiment where the discharge overcurrent is detected by the protection IC on the high-potential side.

[0049] Figure 16 This diagram illustrates the situation in the battery pack of the fourth embodiment where the discharge overcurrent is detected by the protection IC on the high-potential side.

[0050] Figure 17This is a timeline illustrating the state before and after the overcurrent discharge is detected by the protection IC on the high-potential side in the battery pack of the fourth embodiment.

[0051] Figure 18 This is a diagram showing a first variation of the battery pack in the first embodiment.

[0052] Figure 19 This is a diagram showing a second variation of the battery pack in the first embodiment.

[0053] Figure 20 This is a diagram showing a first variation of the battery pack in the second embodiment.

[0054] Explanation of reference numerals in the attached figures

[0055] 1…First terminal; 2…Second terminal; 3…Third terminal; 4…Second current path; 5…First current path; 6…Third current path; 10, 20, 50, 210, 220…Protection IC; 30, 230…First switching circuit; 36…First protection element; 40, 60, 240…Second switching circuit; 46, 66…Second protection element; 71, 171…First secondary battery; 72, 172…Second secondary battery; 80, 80A, 80B, 82…Disconnection state detection circuit; 91, 191…First load; 92, 192…Second load; 100~104…Battery pack; 110~114…Secondary battery protection circuit; 121, 122, 123…Composite integrated circuit. Detailed Implementation

[0056] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. First, for comparison with embodiments of the present disclosure, the structure of a battery pack in a comparative embodiment will be described.

[0057] Figure 1 This is a diagram illustrating the structure of a battery pack in one comparative method. Figure 1 The battery pack 100 shown includes a first secondary battery 271 and a second secondary battery 272 connected in series, and a secondary battery protection circuit 110 that protects the first secondary battery 271 and the second secondary battery 272 respectively.

[0058] Hereinafter, the first secondary battery 271 and the second secondary battery 272 will be referred to as the first battery 271 and the second battery 272, respectively. In addition, the first secondary battery 271 and the second secondary battery 272 will also be referred to as batteries 271 and 272.

[0059] Batteries 271 and 272 are both rechargeable batteries. The first battery 271 supplies power to a first load 191 connected to the first terminal 201 and the second terminal 202. Additionally, batteries 271 and 272, connected in series, supply power to a second load 192 connected to the first terminal 201 and the third terminal 203. Batteries 271 and 272 can be charged using a charger (not shown) connected to the first terminal 201 and the third terminal 203. Specific examples of batteries 271 and 272 include lithium-ion batteries and lithium polymer batteries.

[0060] The secondary battery protection circuit 110 includes a first terminal 201, a second terminal 202, a third terminal 203, a first switch circuit 230, a second switch circuit 240, a first protection IC 210, and a second protection IC 220.

[0061] The negative terminal of the first battery 271 is connected to the first terminal 201 via a first current path 205, and the first switching circuit 230 is inserted in series into the first current path 205. The positive terminal of the first battery 271 is connected to the negative terminal of the second battery 272 via a second current path 204. The positive terminal of the second battery 272 is connected to the third terminal 203 via a third current path 206, and the second switching circuit 240 is inserted in series into the third current path 206.

[0062] The first switching circuit 230 includes, for example, a charging control transistor 231 whose gate is connected to the charging control terminal 211 (COUT terminal), and a discharging control transistor 232 whose gate is connected to the discharging control terminal 212 (DOUT terminal). The charging control transistor 231 cuts off the first current path 205 through which the charging current of the first battery 271 flows, and the discharging control transistor 232 cuts off the first current path 205 through which the discharging current of the first battery 271 flows. The charging control transistor 231 and the discharging control transistor 232 are switching elements that switch the first current path 205 on / off, and are inserted in series into the first current path 205. For example, both the charging control transistor 231 and the discharging control transistor 232 are NMOS transistors. The charging control transistor 231 has a diode parasitic between its drain and source. The discharging control transistor 232 has a diode parasitic between its drain and source.

[0063] The second switching circuit 240 includes, for example, a charging control transistor 241 whose gate is connected to the charging control terminal 221 (COUT terminal), and a discharging control transistor 242 whose gate is connected to the discharging control terminal 222 (DOUT terminal). The charging control transistor 241 cuts off the third current path 206 through which the charging current of the second battery 272 flows, and the discharging control transistor 242 cuts off the third current path 206 through which the discharging current of the second battery 272 flows. The charging control transistor 241 and the discharging control transistor 242 are switching elements that switch the third current path 206 on / off, and are inserted in series in the third current path 206. For example, both the charging control transistor 241 and the discharging control transistor 242 are PMOS transistors. The charging control transistor 241 has a diode parasitic between its drain and source. The discharging control transistor 242 has a diode parasitic between its drain and source.

[0064] The first protection IC210 is an integrated circuit that operates based on the battery voltage (also called "battery voltage") between the positive and negative terminals of the first battery 271. The first protection IC210 includes a charging control terminal 211 (COUT terminal), a discharging control terminal 212 (DOUT terminal), a monitoring terminal 218 (VM1 terminal), a power supply terminal 215 (VDD terminal), and a ground terminal 213 (VSS terminal).

[0065] The charging control terminal 211 is connected to the gate of the charging control transistor 231, and outputs a signal that turns the charging control transistor 231 on or off. The discharging control terminal 212 is connected to the gate of the discharging control transistor 232, and outputs a signal that turns the discharging control transistor 232 on or off.

[0066] Monitoring terminal 218 is used to monitor the potential of first terminal 201 and is connected to first terminal 201. Monitoring terminal 218 is used, for example, to protect IC 210 by monitoring whether a load 191 or a charger (not shown) is connected. It is connected to first current path 205 between first switching circuit 230 and first terminal 201 via resistor 214.

[0067] Power terminal 215 is the high-potential power terminal of the first protection IC 210, and is connected to the positive terminal of the first battery 271 and the second current path 204 via resistor 237. Ground terminal 213 is the low-potential power terminal of the first protection IC 210, and is connected to the negative terminal of the first battery 271 and the first current path 205.

[0068] The first protection IC 210 is an integrated circuit that protects the first battery 271 or both batteries 271 and 272 by turning the first switching circuit 230 off. The first protection IC 210 protects the first battery 271 from overcharging and other charging abnormalities by turning the charging control transistor 231 off, and protects the first battery 271 from over-discharging and other discharging abnormalities, as well as short-circuit abnormalities, by turning the discharging control transistor 232 off.

[0069] The first protection IC 210 detects the state of the first battery 271. The first protection IC 210 monitors the voltage between the VDD and VSS terminals, i.e., the power supply voltage Vd. The VDD terminal is connected to the positive terminal of the first battery 271, and the VSS terminal is connected to the negative terminal of the first battery 271, so the power supply voltage Vd is approximately equal to the battery voltage VBAT of the first battery 271. Therefore, the first protection IC 210 can detect the battery voltage VBAT of the first battery 271 by monitoring the power supply voltage Vd. Additionally, the first protection IC 210 monitors the voltage at the VM1 terminal, which uses the VSS terminal as a reference potential, i.e., the monitoring voltage V-.

[0070] The first protection IC 210, for example, generates an overcharge detection signal indicating that a power supply voltage Vd higher than the overcharge detection voltage Vdet1 has been detected when it detects a power supply voltage Vd higher than the overcharge detection voltage Vdet1. Additionally, the first protection IC 210 generates an overcharge recovery detection signal indicating that a power supply voltage Vd lower than the overcharge recovery voltage Vrel1 has been detected when it detects a power supply voltage Vd lower than the overcharge recovery voltage Vrel1. The overcharge detection voltage Vdet1 is a threshold for overcharge detection, and the overcharge recovery voltage Vrel1 is a threshold for overcharge recovery detection.

[0071] The first protection IC 210, for example, generates an over-discharge detection signal indicating that a power supply voltage Vd below the specified over-discharge detection voltage Vdet2 has been detected when it detects a power supply voltage Vd below the specified over-discharge detection voltage Vdet2. Additionally, the first protection IC 210 generates an over-discharge recovery detection signal indicating that a power supply voltage Vd above the specified over-discharge recovery voltage Vrel2 has been detected when it detects a power supply voltage Vd above the specified over-discharge recovery voltage Vrel2. The over-discharge detection voltage Vdet2 is a threshold for over-discharge detection, and the over-discharge recovery voltage Vrel2 is a threshold for over-discharge recovery detection.

[0072] For example, when the first protection IC 210 detects a monitoring voltage V- that is higher than the predetermined discharge overcurrent detection voltage Vdet3, it generates a discharge overcurrent detection signal indicating that a monitoring voltage V- higher than the discharge overcurrent detection voltage Vdet3 has been detected. Additionally, when the first protection IC 210 detects a monitoring voltage V- that is lower than the predetermined discharge overcurrent recovery voltage Vrel3, it generates a discharge overcurrent recovery detection signal indicating that a monitoring voltage V- lower than the discharge overcurrent recovery voltage Vrel3 has been detected. The discharge overcurrent detection voltage Vdet3 is a threshold for discharge overcurrent detection, and the discharge overcurrent recovery voltage Vrel3 is a threshold for discharge overcurrent recovery detection.

[0073] For example, when the first protection IC 210 detects a monitoring voltage V- that is lower than the predetermined charging overcurrent detection voltage Vdet4, it generates a charging overcurrent detection signal indicating that a monitoring voltage V- lower than the charging overcurrent detection voltage Vdet4 has been detected. Additionally, when the first protection IC 210 detects a monitoring voltage V- that is higher than the predetermined charging overcurrent recovery voltage Vrel4, it generates a charging overcurrent recovery detection signal indicating that a monitoring voltage V- higher than the charging overcurrent recovery voltage Vrel4 has been detected. The charging overcurrent detection voltage Vdet4 is a threshold for charging overcurrent detection, and the charging overcurrent recovery voltage Vrel4 is a threshold for charging overcurrent recovery detection.

[0074] Upon detecting overcharging or overcurrent in the first battery 271, the first protection IC 210, after a predetermined delay, changes the output state of the COUT terminal from high to low. By making the COUT terminal output low, the charging control transistor 231 is turned off, thus preventing current from flowing through the first current path 205 in the direction of charging the first battery 271. Therefore, charging of the first battery 271 stops, protecting it from overcharging or overcurrent.

[0075] On the other hand, when the first protection IC 210 detects over-discharge or overcurrent in the first battery 271, it changes the output state of the DOUT terminal from high to low after a predetermined delay time. Since the output state of the DOUT terminal becomes low, the discharge control transistor 232 is turned off, thus preventing current flowing through the first current path 205 in the direction of discharging the first battery 271. Therefore, the discharge of the first battery 271 stops, protecting it from over-discharge or overcurrent.

[0076] The first protection IC210, for example, is formed using multiple analog logic circuits instead of a CPU (Central Processing Unit).

[0077] The second protection IC220 is an integrated circuit that operates based on the battery voltage (also known as "battery voltage") between the positive and negative terminals of the second battery 272. The second protection IC220 includes a charging control terminal 221 (COUT terminal), a discharging control terminal 222 (DOUT terminal), a monitoring terminal 228 (VM2 terminal), a power supply terminal 225 (VDD terminal), and a ground terminal 223 (VSS terminal).

[0078] The charging control terminal 221 is connected to the gate of the charging control transistor 241, and outputs a signal that turns the charging control transistor 241 on or off. The discharging control terminal 222 is connected to the gate of the discharging control transistor 242, and outputs a signal that turns the discharging control transistor 242 on or off.

[0079] Monitoring terminal 228 is used to monitor the potential of third terminal 203 and is connected to third terminal 203. Monitoring terminal 228 is used, for example, to protect IC 220 by monitoring whether a load 192 or a charger (not shown) is connected. It is connected to third current path 206 between second switching circuit 240 and third terminal 203 via resistor 224.

[0080] Power terminal 225 is the high-potential power terminal of the second protection IC 220, and is connected to the positive terminal of the second battery 272 and the third current path 206 via resistor 247. Ground terminal 223 is the low-potential power terminal of the second protection IC 220, and is connected to the negative terminal of the second battery 272 and the second current path 204.

[0081] The second protection IC 220 is an integrated circuit that protects the second battery 272 or both batteries 271 and 272 by turning the second switching circuit 240 off. The second protection IC 220 protects the second battery 272 from overcharging and other charging abnormalities by turning the charging control transistor 241 off, and protects the second battery 272 from over-discharging and other discharging abnormalities, as well as short-circuit abnormalities, by turning the discharging control transistor 242 off.

[0082] The second protection IC 220 detects the state of the second battery 272. The second protection IC 220 monitors the voltage between the VDD and VSS terminals, i.e., the power supply voltage Vd. The VDD terminal is connected to the positive terminal of the second battery 272, and the VSS terminal is connected to the negative terminal of the second battery 272, so the power supply voltage Vd is approximately equal to the battery voltage VBAT of the second battery 272. Therefore, the second protection IC 220 can detect the battery voltage VBAT of the second battery 272 by monitoring the power supply voltage Vd. Additionally, the second protection IC 220 monitors the voltage at the VM2 terminal, which uses the VDD terminal as a reference potential, i.e., the monitoring voltage V+.

[0083] The second protection IC220 can detect overcharge or over-discharge in the same way as the first protection IC210 using the aforementioned threshold detection method.

[0084] For example, when the second protection IC 220 detects a monitoring voltage V+ that is lower than the predetermined discharge overcurrent detection voltage Vdet3, it generates a discharge overcurrent detection signal indicating that a monitoring voltage V+ lower than the discharge overcurrent detection voltage Vdet3 has been detected. Additionally, when the second protection IC 220 detects a monitoring voltage V+ that is higher than the predetermined discharge overcurrent recovery voltage Vrel3, it generates a discharge overcurrent recovery detection signal indicating that a monitoring voltage V+ higher than the discharge overcurrent recovery voltage Vrel3 has been detected.

[0085] The second protection IC 220, for example, generates a charging overcurrent detection signal indicating that a monitoring voltage V+ higher than the predetermined charging overcurrent detection voltage Vdet4 has been detected when it detects a monitoring voltage V+ higher than the predetermined charging overcurrent detection voltage Vdet4. Additionally, the second protection IC 220 generates a charging overcurrent recovery detection signal indicating that a monitoring voltage V+ lower than the predetermined charging overcurrent recovery voltage Vrel4 has been detected when it detects a monitoring voltage V+ lower than the predetermined charging overcurrent recovery voltage Vrel4.

[0086] Upon detecting overcharging or overcurrent in the second battery 272, the second protection IC 220, after a predetermined delay, changes the output state of the COUT terminal from high to low. Because the COUT terminal output state becomes low, the charging control transistor 241 is turned off, thus preventing current from flowing through the first current path 205 in the direction of charging the second battery 272. Therefore, charging of the second battery 272 stops, protecting it from overcharging or overcurrent.

[0087] On the other hand, when the second protection IC 220 detects over-discharge or overcurrent in the second battery 272, it changes the output state of the DOUT terminal from high to low after a predetermined delay time. Because the output state of the DOUT terminal changes to low, the discharge control transistor 242 is turned off, thus preventing current flowing in the direction of discharge of the second battery 272 from passing through the third current path 206. Therefore, the discharge of the second battery 272 stops, protecting it from over-discharge or overcurrent.

[0088] The second protection IC220, for example, is formed using multiple analog logic circuits instead of a CPU (Central Processing Unit).

[0089] Here, the state in which the first switching circuit 230 is turned on through the first protection IC 210 and the second switching circuit 240 is turned on through the second protection IC 220 is defined as the "normal state". In the normal state, the secondary battery protection circuit 110 outputs a first output voltage Vo1 corresponding to the voltage of the first battery 271 from between the first terminal 201 and the second terminal 202 to the first load 191. Additionally, in the normal state, the secondary battery protection circuit 110 outputs a third output voltage Vo3, obtained by adding the first output voltage Vo1 to the second output voltage Vo2 corresponding to the voltage of the second battery 272, from between the first terminal 201 and the third terminal 203 to the second load 192.

[0090] Furthermore, the state in which the first switching circuit 230 is disconnected via the first protection IC 210 and the second switching circuit 240 is turned on via the second protection IC 220 is defined as the "first protection state". In the first protection state, the secondary battery protection circuit 110 stops outputting the first output voltage Vo1 from between the first terminal 201 and the second terminal 202 to the first load 191, and stops outputting the third output voltage Vo3 from between the first terminal 201 and the third terminal 203. This is because, if the transition from the normal state to the first protection state occurs, the potential of the first terminal 201 changes from the potential of the negative terminal of the first battery 271 to the potential of the positive terminal of the second battery 272.

[0091] Furthermore, the state in which the first switching circuit 230 is turned on through the first protection IC 210 and the second switching circuit 240 is turned off through the second protection IC 220 is defined as the "second protection state". In the second protection state, the secondary battery protection circuit 110 outputs the first output voltage Vo from between the first terminal 201 and the second terminal 202 to the first load 191, and stops outputting the third output voltage Vo3 from between the first terminal 201 and the third terminal 203. This is because, if the transition from the normal state to the second protection state occurs, the potential of the third terminal 203 changes from the potential of the positive terminal of the second battery 272 to the potential of the negative terminal of the first battery 271; on the other hand, the potentials of the first terminal 201 and the second terminal 202 do not change.

[0092] Thus, according to a comparison method, not only are the protection functions of batteries 271 and 272 provided, but a first output voltage Vo can also be output to the first load 191, and a third output voltage Vo3 can be output to the second load 192. Therefore, on the side of the device receiving power from the battery pack 100 (the device having the first load 191 and the second load 192), no voltage conversion is required, thus improving the power efficiency of the device. In other words, the power consumption efficiency supplied to the device from the battery pack 100 can be improved.

[0093] However, there is a case where the first protection IC 210 has a first protection element 236 that forms an internal current path from the monitoring terminal 218 to the power supply terminal 215. Similarly, there is a case where the second protection IC 220 has a second protection element 246 that forms an internal current path from the ground terminal 223 to the monitoring terminal 228. The protection elements 236 and 246 are, for example, diode elements for electrostatic discharge (ESD) countermeasures. In this configuration where the protection elements 236 and 246 are present, a positive voltage is applied to the protection element 236 or the protection element 246 in either the first protection state or the second protection state. A current path is formed on the protection element to which the positive voltage is applied, and the current continuously flows through the protection element.

[0094] Next, refer to Figures 2-5 The case where a positive voltage is applied to protection element 236 or protection element 246 in either the first protection state or the second protection state will be described. Furthermore, Figures 2-5 This example illustrates the case where batteries 271 and 272 have voltages of 4V under normal conditions.

[0095] Figure 2This diagram illustrates a situation in a battery pack 100 in a comparative configuration where a discharge overcurrent is detected by a first protection IC 210 on the low-potential side. When the first protection IC 210 detects a discharge overcurrent flowing due to a short circuit in the second load 192, it disconnects the discharge control transistor 232 (first protection state). In this first protection state, the potential of the first terminal 201 changes from 0V to 8V. As a result, as... Figure 2 As shown, an internal current path is formed through the first protection element 236, so unwanted current may flow through it.

[0096] Figure 3 This diagram illustrates a situation in a battery pack 100 in a comparison configuration where a discharge overcurrent is detected by a second protection IC 220 on the high-potential side. If the second protection IC 220 detects a discharge overcurrent flowing due to a short circuit in the second load 192, it disconnects the discharge control transistor 242 (second protection state). In this second protection state, the potential of the third terminal 203 changes from 8V to 0V. As a result, as... Figure 3 As shown, an internal current path is formed through the second protection element 246, so unwanted current may flow through it.

[0097] Figure 4 This diagram illustrates a situation in a battery pack 100 in a comparison configuration where over-discharge of the first battery 271 on the low-potential side is detected by the first protection IC 210 on the low-potential side. If the first protection IC 210 detects over-discharge of the first battery 271, it disconnects the discharge control transistor 232 (first protection state). In this first protection state, the potential of the first terminal 201 changes from 0V to 8V. As a result, as... Figure 4 As shown, an internal current path is formed through the first protection element 236, so unwanted current may flow through it.

[0098] Figure 5 This diagram illustrates a situation in a battery pack 100 in a comparison configuration where over-discharge of the second battery 272 on the high-potential side is detected by the second protection IC 220 on the high-potential side. If the second protection IC 220 detects over-discharge of the second battery 272, it disconnects the discharge control transistor 242 (second protection state). In this second protection state, the potential of the third terminal 203 changes from 8V to 0V. As a result, as... Figure 5 As shown, an internal current path is formed through the second protection element 246, so unwanted current may flow through it.

[0099] Next, refer to Figure 6An embodiment that can prevent the flow of undesirable current as described above, even when protective elements such as 236 and 246 are present, will be described.

[0100] Figure 6 This diagram illustrates the structure of the battery pack in the first embodiment, showing the situation where a discharge overcurrent is detected by the protection IC on the high-potential side. Furthermore, descriptions of the same structure and effects as described above in the first embodiment are omitted or simplified by referring to the above description.

[0101] Figure 6 The battery pack 101 shown includes a first secondary battery 71 and a second secondary battery 72 connected in series, and a secondary battery protection circuit 111 that protects the first secondary battery 71 and the second secondary battery 72 respectively. The secondary battery protection circuit 111 outputs the voltages of the first secondary battery and the second secondary battery connected in series, and the voltage obtained by adding the voltages together.

[0102] Hereinafter, the first secondary battery 71 and the second secondary battery 72 will be referred to as the first battery 71 and the second battery 72, respectively. In addition, the first secondary battery 71 and the second secondary battery 72 will also be referred to as batteries 71 and 72.

[0103] The secondary battery protection circuit 111 includes a first terminal 1, a second terminal 2, a third terminal 3, a first switching circuit 30, a second switching circuit 40, a first protection IC 10, and a second protection IC 20. The first terminal 1 is an example of a first output terminal connected to the negative terminal of the first secondary battery. The second terminal 2 is an example of a second output terminal connected to both the positive terminal of the first secondary battery and the negative terminal of the second secondary battery. The third terminal 3 is an example of a third output terminal connected to the positive terminal of the second secondary battery.

[0104] The negative terminal of the first battery 71 is connected to the first terminal 1 via a first current path 5, and the first switching circuit 30 is inserted in series into the first current path 5. The positive terminal of the first battery 71 and the negative terminal of the second battery 72 are connected to the second terminal 2 via a second current path 4. The positive terminal of the second battery 72 is connected to the third terminal 3 via a third current path 6, and the second switching circuit 40 is inserted in series into the third current path 6.

[0105] The first switching circuit 30, for example, has a switch, namely a charging control transistor 31, whose gate is connected to the charging control terminal 11 (COUT terminal), and a switch, namely a discharging control transistor 32, whose gate is connected to the discharging control terminal 12 (DOUT terminal).

[0106] The second switching circuit 40, for example, has a switch, namely a charging control transistor 41, whose gate is connected to the charging control terminal 21 (COUT terminal), and a switch, namely a discharging control transistor 42, whose gate is connected to the discharging control terminal 22 (DOUT terminal). The discharging control transistor 42 is an example of a second switch disposed in the discharging path.

[0107] The first protection IC 10 includes a first monitoring terminal 18 (VM1 terminal) connected to the first current path 5 via a resistor 14 between the first terminal 1 and the first switching circuit 30, and a first power supply terminal 15 (VDD terminal) connected to the positive terminal of the second battery 72 via a resistor 37. Additionally, the first protection IC 10 includes a charging control terminal 11 (COUT terminal), a discharging control terminal 12 (DOUT terminal), a battery voltage input terminal 16 (VH terminal), and a ground terminal 13 (VSS terminal). Furthermore, the first protection IC 10 has a first protection element 36 forming an internal current path from the first monitoring terminal 18 to the first power supply terminal 15. The first protection IC 10 is an example of a first protection circuit that protects the first secondary battery from over-discharge or overcurrent discharge by a first switch provided in the discharge path.

[0108] The second protection IC 20 includes a second monitoring terminal 28 (VM2 terminal) connected to the third current path 6 via a resistor 24 between the third terminal 3 and the second switching circuit 40, and a ground terminal 23 (VSS terminal) connected to the negative terminal of the second battery 72. Additionally, the second protection IC 20 includes a charging control terminal 21 (COUT terminal), a discharging control terminal 22 (DOUT terminal), and a second power supply terminal 25 (VDD terminal) connected to the positive terminal of the second battery 72 via a resistor 47. Furthermore, the second protection IC 20 has a second protection element 46 forming an internal current path from the ground terminal 23 to the second monitoring terminal 28. The second protection IC 20 is an example of a second protection circuit that protects the second secondary battery from over-discharge or overcurrent discharge by using a second switch provided in the discharge path.

[0109] When the disconnection state detection circuit 80 detects that the second switching circuit 40 is in an disconnected state, it cuts off the current flowing to the second protection element 46 by fixing the potential of the second monitoring terminal 28. The disconnection state detection circuit 80 includes switches 83 and 84, and a resistor 81. Switches 83 and 84 are, for example, PMOS transistors.

[0110] Switch 83 is inserted in series between resistor 24 and third terminal 3. The gate of switch 83 is connected to second terminal 2. Resistor 81 is connected in parallel with switch 83. Switch 83 is a component that detects the potential relationship between second terminal 2 and third terminal 3, and switches the current (in other words, changes from on to off) when the potential relationship is reversed.

[0111] Regarding switch 84, one end is connected to monitoring terminal 28 and the other end is connected to second terminal 2. The gate of switch 84 is connected to third terminal 3. Switch 84 is an element that performs the opposite operation to switch 83 and is used to fix the potential of terminal VM2 when the current is cut off by switch 83.

[0112] Resistor 81 is a component used to disconnect the third terminal 3 from the VM2 terminal by switching 83, thereby enabling the second protection IC 20 to monitor the potential of the third terminal 3 through the VM2 terminal.

[0113] Figure 6 This diagram illustrates the situation in the battery pack 101 of the first embodiment where a discharge overcurrent is detected by the second protection IC 20 on the high-potential side. If the second protection IC 20 detects a discharge overcurrent flowing due to a short circuit or the like that causing the second load 92, it disconnects the discharge control transistor 42 (second protection state). Figure 7 This is a timeline illustrating the state before and after the discharge overcurrent is detected by the second protection IC 20 on the high-potential side in the battery pack 101 of the first embodiment. Figure 7 In the diagram, SW42, SW83, and SW84 represent discharge control transistor 42, switch 83, and switch 84, respectively, and Vth represents the threshold voltage of each of switches 83 and 84.

[0114] State 1: Under normal discharge conditions, if an overcurrent is detected due to a short circuit in the second load 92, the second protection IC 20 disconnects the discharge control transistor 42 after the overcurrent detection delay time, thus cutting off the discharge.

[0115] State 2: By disconnecting the discharge control transistor 42, the potential V3 of the third terminal 3 changes from 8V to 0V. Consequently, switch 83 changes from on to off, and switch 84 changes from off to on. In other words, the disconnection state detection circuit 80 detects the change in the potential V3 of the third terminal 3 from 8V to 0V, thereby detecting the disconnection state of the second switching circuit 40. Because switch 83 changes from on to off, and switch 84 changes from off to on, the potential of the monitoring terminal 28 of the protection IC 20 is approximately equal to the potential of the ground terminal 23, so no current is generated to the protection element 46. On the other hand, if a discharge overcurrent is detected, the VM2 terminal is pulled up (connected) to the VDD terminal via resistor 45.

[0116] State 3: If the second load 92 is released from the third terminal 3, the potential of the third terminal 3 rises from 0V to near the potential of the second terminal 2 due to the presence of resistors 45, 24, and 81. At this time, the switch 84, which short-circuits the VM2 terminal and the VSS terminal, changes from on to off. Furthermore, if the potential of the third terminal 3 rises, the switch 83 changes from off to on. Also, if the potential of the third terminal 3 rises, the protection IC 20 detects that the potential of the VM2 terminal has changed from the level of the VSS terminal to the level of the VDD terminal due to the presence of resistor 45. As a result, the second protection IC 20 turns the discharge control transistor 42 from off to on, so the state of the protection circuit returns from the second protection state to the normal state.

[0117] Thus, in the first embodiment, during the second protection state, current will not flow from the first battery 71 to the protection element 46. Therefore, during the second protection state, the secondary battery protection circuit 111 stops outputting current from the first battery 71 to the second load 92 and the first load 91 via the second protection IC 20.

[0118] Figure 8 This diagram illustrates the situation in the battery pack 101 of the first embodiment where a discharge overcurrent is detected by the first protection IC 10 on the low-potential side. If the first protection IC 10 detects a discharge overcurrent flowing due to a short circuit or the like that causing the first load 91, it disconnects the discharge control transistor 32 (first protection state). Figure 9 This is a timeline illustrating the state before and after the first protection IC 100 on the low-potential side detects a discharge overcurrent in the battery pack 101 of the first embodiment. Figure 8 In the diagram, SW32 represents discharge control transistor 32.

[0119] State 1: Under normal discharge conditions, if an overcurrent is detected due to a short circuit in the first load 91, the first protection IC 10 will disconnect the discharge control transistor 32 after the overcurrent detection delay time to cut off the discharge.

[0120] State 2: By disconnecting the discharge control transistor 32, the potential of the first terminal 1 and the VM1 terminal changes from 0V to 4-8V. In this case, the power supply voltage of the first protection IC 10 and the potential difference between the negative terminal of the first battery 71 and the positive terminal of the second battery 72 are approximately equal, so there is no problem with the potential range of the VM2 terminal.

[0121] Thus, in the first embodiment, during the first protection state, current will not flow from the second battery 72 to the protection element 36. Therefore, during the first protection state, the secondary battery protection circuit 111 stops outputting current from the second battery 72 to the second load 92 and the first load 91 via the first protection IC 10.

[0122] Figure 10 This is a diagram illustrating the situation in the battery pack 102 of the second embodiment where the discharge overcurrent is detected by the protection IC on the high-potential side. Figure 11 This is a diagram illustrating the situation in the battery pack 102 of the second embodiment where the discharge overcurrent is detected by the protection IC on the high-potential side. Figure 12 This is a diagram illustrating the situation in the battery pack 102 of the second embodiment where the discharge overcurrent is detected by the protection IC on the low potential side. Figure 13 This is a timeline illustrating the state before and after the discharge overcurrent is detected by the protection IC on the low-potential side in the battery pack 102 of the second embodiment. Furthermore, descriptions of the same structures and effects as those in the above-described embodiments in the second embodiment are omitted or simplified based on the foregoing description.

[0123] Figure 10 The battery pack 102 shown includes a first secondary battery 71 and a second secondary battery 72 connected in series, and a secondary battery protection circuit 112 that protects the first secondary battery 71 and the second secondary battery 72 respectively.

[0124] The first protection IC 10 includes a first monitoring terminal 18 (VM1 terminal) connected to the first current path 5 via a resistor 14 between the first terminal 1 and the first switching circuit 30, and a first power supply terminal 15 (VDD terminal) connected to the positive terminal of the second battery 72. Additionally, the first protection IC 10 includes a charging control terminal 11 (COUT terminal), a discharging control terminal 12 (DOUT terminal), a battery voltage input terminal 16 (VC1 terminal), and a ground terminal 13 (VSS terminal). Furthermore, the first protection IC 10 has a first protection element 36 forming an internal current path from the first monitoring terminal 18 to the first power supply terminal 15.

[0125] The second protection IC 20 includes a second monitoring terminal 28 (VM2 terminal) connected to the third current path 6 via a resistor 24 between the third terminal 3 and the second switching circuit 40, and a ground terminal 23 (VSS terminal) connected to the negative terminal of the second battery 72. Additionally, the second protection IC 20 includes a charging control terminal 21 (COUT terminal), a discharging control terminal 22 (DOUT terminal), a battery voltage input terminal 26 (VC2), and a second power supply terminal 25 (VDD terminal). Furthermore, the second protection IC 20 has a second protection element 46 forming an internal current path from the ground terminal 23 to the second monitoring terminal 28.

[0126] In the second embodiment, the power supply voltages of protection ICs 10 and 20 are both the potential difference between the negative terminal of battery 71 and the positive terminal of battery 72. Therefore, even when switching to the first protection state or the second protection state, the voltages of monitoring terminals 18 and 28 can be used within the allowable voltage range of the ICs, so there is no problem with the potential range of the monitoring terminals.

[0127] Figure 14 This is a diagram illustrating the situation in the battery pack 103 of the third embodiment where the discharge overcurrent is detected by the protection IC on the low potential side. Figure 15 A diagram illustrating the situation where a discharge overcurrent is detected by a protection IC on the high-potential side in the battery pack 103 of the third embodiment. Furthermore, descriptions of structures and effects identical to those in the embodiments described above are omitted or simplified in the third embodiment, referencing the above description.

[0128] Figure 14 The battery pack 103 shown includes a first secondary battery 71 and a second secondary battery 72 connected in series, and a secondary battery protection circuit 113 that protects the first secondary battery 71 and the second secondary battery 72 respectively.

[0129] The secondary battery protection circuit 113 includes a first terminal 1, a second terminal 2, a third terminal 3, a first battery pack section 103A, and a second battery pack section 103B. Furthermore, the first battery pack section 103A includes a first switching circuit 30 and a first protection IC 10, and the second battery pack section 103B includes a second switching circuit 60 and a second protection IC 50.

[0130] The negative terminal of the first battery 71 is connected to the first terminal 1 via a first current path 5, and the first switching circuit 30 is inserted in series into the first current path 5. The positive terminal of the first battery 71 is connected to the second terminal 2 via a second current path 4A. The negative terminal of the second battery 72 is connected to the second terminal 2 via a second current path 4B, and the second switching circuit 60 is inserted in series into the second current path 4B.

[0131] The positive terminal of the second battery 72 is connected to the third terminal 3 via a third current path 6.

[0132] The first switching circuit 30, for example, has a switch, namely a charging control transistor 31, whose gate is connected to the charging control terminal 11 (COUT terminal), and a switch, namely a discharging control transistor 32, whose gate is connected to the discharging control terminal 12 (DOUT terminal). The discharging control transistor 32 is an example of a first switch disposed in the discharging path.

[0133] The second switching circuit 60, for example, has a switch, namely a charging control transistor 61, whose gate is connected to the charging control terminal 51 (COUT terminal), and a discharge control transistor 62, whose gate is connected to the discharge control terminal 52 (DOUT terminal), which also serves as a switch. The discharge control transistor 62 is an example of a second switch disposed in the discharge path.

[0134] The first protection IC 10 includes a first monitoring terminal 18 (VM1 terminal) connected to the first current path 5 via a resistor 14 between the first terminal 1 and the first switching circuit 30, and a first power supply terminal 15 (VDD terminal) connected to the positive terminal of the first battery 71 via a resistor 37. Additionally, the first protection IC 10 includes a charging control terminal 11 (COUT terminal), a discharging control terminal 12 (DOUT terminal), and a ground terminal 13 (VSS terminal). Furthermore, the first protection IC 10 has a first protection element 36 forming an internal current path from the first monitoring terminal 18 to the first power supply terminal 15. The first protection IC 10 or the first battery pack section 103A is an example of a first protection circuit that protects the first secondary battery from over-discharge or overcurrent discharge by means of a first switch provided in the discharge path.

[0135] The second protection IC 50 includes a second monitoring terminal 58 (VM2 terminal) connected to the second current path 4B via a resistor 54 between the second terminal 2 and the second switching circuit 60, and a second power supply terminal 55 (VDD terminal) connected to the positive terminal of the second battery 72 via a resistor 67. Additionally, the second protection IC 50 includes a charging control terminal 51 (COUT terminal), a discharging control terminal 52 (DOUT terminal), and a ground terminal 53 (VSS terminal). Furthermore, the second protection IC 50 has a second protection element 66 forming an internal current path from the second monitoring terminal 58 to the second power supply terminal 55. The second protection IC 50 or the second battery pack section 103B is an example of a second protection circuit that protects the second secondary battery from over-discharge or overcurrent discharge by means of a second switch provided in the discharge path.

[0136] When the disconnection state detection circuit 80A detects that the first switching circuit 30 is in an open state, it cuts off the current flowing to the first protection element 36 by fixing the potential of the first monitoring terminal 18. The disconnection state detection circuit 80A includes switches 83A and 84A, and a resistor 81A. Switches 83A and 84A are, for example, NMOS transistors.

[0137] When the disconnection state detection circuit 80B detects that the second switching circuit 60 is in an open state, it cuts off the current flowing to the second protection element 66 by fixing the potential of the second monitoring terminal 58. The disconnection state detection circuit 80B includes switches 83B and 84B, and a resistor 81B. Switches 83B and 84B are, for example, NMOS transistors.

[0138] The disconnection state detection circuits 80A and 80B have the same function as the disconnection state detection circuit 80 of the first embodiment described above. In other words, when the disconnection state detection circuit 80A detects that the first switching circuit 30 is in an open state, it cuts off the current flowing to the first protection element 36; when the disconnection state detection circuit 80B detects that the second switching circuit 60 is in an open state, it cuts off the current flowing to the second protection element 66. The only difference between the disconnection state detection circuits 80A and 80B and the disconnection state detection circuit 80 described above is that the PMOS structure is changed to an NMOS structure; therefore, a detailed description is omitted as described above.

[0139] Figure 16 This is a diagram illustrating the situation in the battery pack 104 of the fourth embodiment where the discharge overcurrent is detected by the protection IC on the high-potential side. Figure 17 This is a timeline illustrating the state before and after the overcurrent discharge is detected by the protection IC on the high-potential side in the battery pack 104 of the fourth embodiment. Furthermore, in the fourth embodiment, descriptions of structures and effects identical to those in the embodiments described above are omitted or simplified based on the aforementioned descriptions.

[0140] Among the methods for restoring from the protected state after overcurrent detection, there are two types: load release restoration, which restores from the protected state by releasing the load, and charger connection restoration, which restores from the protected state by connecting the charger. In the fourth embodiment, the charger connection restoration method is shown.

[0141] Figure 16 The battery pack 104 shown includes a first secondary battery 71 and a second secondary battery 72 connected in series, and a secondary battery protection circuit 114 that protects the first secondary battery 71 and the second secondary battery 72 respectively.

[0142] The first protection IC 10 includes a first monitoring terminal 18 (VM1 terminal) connected to the first current path 5 via a resistor 14 between the first terminal 1 and the first switching circuit 30, and a first power supply terminal 15 (VDD terminal) connected to the positive terminal of the second battery 72. Additionally, the first protection IC 10 includes a charging control terminal 11 (COUT terminal), a discharging control terminal 12 (DOUT terminal), a battery voltage input terminal 16 (VC terminal), and a ground terminal 13 (VSS terminal). Furthermore, the first protection IC 10 has a first protection element 36 forming an internal current path from the first monitoring terminal 18 to the first power supply terminal 15.

[0143] The second protection IC 50 includes a second monitoring terminal 58 (VM2 terminal) connected to the second current path 4B via a resistor 54 between the second terminal 2 and the second switching circuit 60, and a second power supply terminal 55 (VDD terminal) connected to the positive terminal of the second battery 72 via a resistor 67. Additionally, the second protection IC 50 includes a charging control terminal 51 (COUT terminal), a discharging control terminal 52 (DOUT terminal), and a ground terminal 53 (VSS terminal). Furthermore, the second protection IC 50 has a second protection element 66 forming an internal current path from the second monitoring terminal 58 to the second power supply terminal 55.

[0144] When the disconnection state detection circuit 82 detects that the second switch circuit 60 is in an open state, it cuts off the current flowing to the second protection element 66 by fixing the potential of the second monitoring terminal 58. Furthermore, the disconnection state detection circuit 82 maintains the state of cutting off the current flowing to the second protection element 66 until the charger is connected to the first terminal 1 and the third terminal 3. The disconnection state detection circuit 82 includes switches 83, 86, and 87 and a resistor 85. Switch 83 is, for example, a PMS transistor, and switches 86 and 87 are, for example, NMOS transistors.

[0145] Switch 83 is connected in series to the third current path 6. Resistor 85 is connected between the gate and source of switch 83. Switches 86 and 87 are connected in series, and their gates are connected to the discharge control terminal 52. The source of switch 86 is connected to the gate of switch 83, and the source of switch 87 is connected to the second terminal 2.

[0146] In the fourth embodiment, if the second protection IC 50 detects a discharge overcurrent flowing to the first load 91, the VM2 terminal is pulled up (connected) to the VDD terminal via resistor 65 through switch 64. Thus, the second protection state is maintained even if the first load 91 is released. To restore to the normal state, the potential of the VM2 terminal is lowered to the level of the VSS terminal by connecting the charger. As a result, it is possible to restore from the second protection state to the normal state.

[0147] The secondary battery protection circuit and battery pack have been described above through embodiments, but the present invention is not limited to the above embodiments. Various modifications and improvements, such as combinations, substitutions, and other variations, can be made with some or all of the other embodiments within the scope of the present invention.

[0148] For example, in Figure 14 , 16 In the structure, the first switching circuit 30 can also be inserted in series between the positive terminal of the first secondary battery 71 and the second terminal 2 into the second current path 4A. Additionally, in Figure 14 , 16 In the structure, the second switch circuit 60 can also be inserted in series into the third current path 6 between the positive terminal of the second secondary battery 72 and the third terminal 3.

[0149] Figure 18 This diagram illustrates a first variation of the battery pack in the first embodiment. The secondary battery protection circuit 111 includes a composite integrated circuit 121 that integrates (compositely integrated) the first protection IC 10 and the second protection IC 20. The composite integrated circuit 121 is a multi-chip package that encapsulates the first protection IC 10 and the second protection IC 20 in one package. By housing the two components in one package, the ease of substrate mounting is improved, and the mounting area is reduced. The composite integrated circuit 121 may also compositely integrate at least one of the pair of the first protection IC 10 and the first switching circuit 30, and the pair of the second protection IC 20 and the second switching circuit 40.

[0150] Figure 19 This diagram illustrates a second variation of the battery pack in the first embodiment. The secondary battery protection circuit 111 includes a composite integrated circuit 122 that integrates a second protection IC 20, a second switching circuit 40, and a switch 83. The composite integrated circuit 122 is a multi-chip package in which the second protection IC 20, the second switching circuit 40, and the switch 83 are packaged together. By housing the three components in one package, the ease of substrate mounting is improved, and the mounting area is reduced.

[0151] Figure 20 This diagram illustrates a first variation of the battery pack in the second embodiment. The secondary battery protection circuit 112 includes a composite integrated circuit 123 that integrates (compositely integrates) the first protection IC 10 and the second protection IC 20. The composite integrated circuit 123 is a multi-chip circuit in which the first protection IC 10 and the second protection IC 20 are packaged in a single package. By confining the two components to a single package, the ease of substrate mounting is improved, and the mounting area is reduced. The composite integrated circuit 123 may also compositely integrate at least one of the pair of the first protection IC 10 and the first switching circuit 30, and the pair of the second protection IC 20 and the second switching circuit 40.

[0152] Furthermore, in various embodiments, at least one of the charging control transistor 31 and the discharging control transistor 32 can also be integrated on the same chip as the first protection IC 10. Similarly, at least one of the charging control transistor 41 and the discharging control transistor 42 can also be integrated on the same chip as the second protection IC 20. Similarly, at least one of the charging control transistor 61 and the discharging control transistor 62 can also be integrated on the same chip as the second protection IC 50.

Claims

1. A secondary battery protection circuit, which protects a first secondary battery and a second secondary battery connected in series, characterized in that, The secondary battery protection circuit includes: a first terminal; a second terminal; a third terminal; a current path connecting between a positive electrode of the first secondary battery and the second terminal, and being different from a current path between a negative electrode of the second secondary battery and the second terminal; a first switching circuit inserted in a current path between a negative electrode of the first secondary battery and the first terminal in series; a second switching circuit inserted in a current path between a negative electrode of the second secondary battery and the second terminal or a current path between a positive electrode of the second secondary battery and the third terminal in series; a first protection IC protecting at least the first secondary battery from overdischarge or overdischarge current by making the first switching circuit open; a second protection IC protecting at least the second secondary battery from overdischarge or overdischarge current by making the second switching circuit open, when the first switching circuit is turned on by the first protection IC and the second switching circuit is turned on by the second protection IC, a first output voltage corresponding to a voltage of the first secondary battery is output from between the first terminal and the second terminal to a first load, and a third output voltage obtained by adding a second output voltage corresponding to a voltage of the second secondary battery to the first output voltage is output from between the first terminal and the third terminal to a second load, when the first switching circuit is open by the first protection IC and the second switching circuit is turned on by the second protection IC, the first output voltage is stopped from being output from between the first terminal and the second terminal to the first load, and the third output voltage is stopped from being output from between the first terminal and the third terminal, when the first switching circuit is turned on by the first protection IC and the second switching circuit is open by the second protection IC, the first output voltage is output from between the first terminal and the second terminal to the first load, and the third output voltage is stopped from being output from between the first terminal and the third terminal.

2. The secondary battery protection circuit according to claim 1, wherein when the first switching circuit is open by the first protection IC and the second switching circuit is turned on by the second protection IC, a current is stopped from being output from the first secondary battery to the first load via the first protection IC, and when the first switching circuit is turned on by the first protection IC and the second switching circuit is open by the second protection IC, a current is stopped from being output from the first secondary battery to the second load via the second protection IC.

3. The secondary battery protection circuit according to claim 1, wherein the secondary battery protection circuit includes an open state detection circuit detecting an open state of at least one of the first switching circuit and the second switching circuit.

4. The secondary battery protection circuit according to claim 3, wherein ​ The first switch circuit is inserted in series into a first current path between a negative electrode of the first secondary battery and the first terminal, The second switch circuit is inserted in series into a second current path between a negative electrode of the second secondary battery and the second terminal, The first protection IC has a first monitoring terminal connected to the first current path via a resistance between the first terminal and the first switch circuit, a first power terminal connected to a positive electrode of the first secondary battery, and a first protection element forming an internal current path from the first monitoring terminal to the first power terminal, The second protection IC has a second monitoring terminal connected to the second current path via a resistance between the second terminal and the second switch circuit, a second power terminal connected to a positive electrode of the second secondary battery, and a second protection element forming an internal current path from the second monitoring terminal to the second power terminal, In the case where the open state detection circuit detects the open state of the first switch circuit, the current flowing through the first protection element is cut off, and in the case where the open state detection circuit detects the open state of the second switch circuit, the current flowing through the second protection element is cut off.

5. The secondary battery protection circuit according to claim 4, wherein In the case where the open state detection circuit detects the open state of the first switch circuit, the current flowing through the first protection element is cut off by fixing the potential of the first monitoring terminal, In the case where the open state detection circuit detects the open state of the second switch circuit, the current flowing through the second protection element is cut off by fixing the potential of the second monitoring terminal.

6. The secondary battery protection circuit according to claim 3, wherein The first switch circuit is inserted in series into a first current path between a negative electrode of the first secondary battery and the first terminal, The second switch circuit is inserted in series into a third current path between a positive electrode of the second secondary battery and the third terminal, The first protection IC has a first monitoring terminal connected to the first current path via a resistance between the first terminal and the first switch circuit, a first power terminal connected to a positive electrode of the second secondary battery, and a first protection element forming an internal current path from the first monitoring terminal to the first power terminal, The second protection IC has a second monitoring terminal connected to the third current path via a resistance between the third terminal and the second switch circuit, a ground terminal connected to a negative electrode of the second secondary battery, and a second protection element forming an internal current path from the ground terminal to the second monitoring terminal, The open state detection circuit cuts off the current flowing to the second protection element in the case where the open state of the second switch circuit is detected.

7. The secondary battery protection circuit according to claim 6, wherein ​ The open state detection circuit cuts off the current flowing to the second protection element by fixing the potential of the second monitoring terminal when the open state of the second switching circuit is detected.

8. The secondary battery protection circuit according to claim 3, wherein The first switching circuit is inserted in a first current path between a negative electrode of the first secondary battery and the first terminal in series, The second switching circuit is inserted in a second current path between a negative electrode of the second secondary battery and the second terminal in series, The first protection IC has a first monitoring terminal connected to the first current path via a resistance between the first terminal and the first switching circuit, a first power terminal connected to a positive electrode of the second secondary battery, and a first protection element forming an internal current path from the first monitoring terminal to the first power terminal, The second protection IC has a second monitoring terminal connected to the second current path via a resistance between the second terminal and the second switching circuit, a second power terminal connected to a positive electrode of the second secondary battery, and a second protection element forming an internal current path from the second monitoring terminal to the second power terminal, The open state detection circuit cuts off the current flowing to the second protection element when the open state of the second switching circuit is detected.

9. The secondary battery protection circuit according to claim 8, wherein The open state detection circuit cuts off the current flowing to the second protection element by fixing the potential of the second monitoring terminal when the open state of the second switching circuit is detected.

10. The secondary battery protection circuit according to claim 9, wherein The open state detection circuit maintains the state of cutting off the current flowing to the second protection element until a charger is connected to the first terminal and the third terminal.

11. The secondary battery protection circuit according to claim 1, wherein The first switching circuit is inserted in a first current path between a negative electrode of the first secondary battery and the first terminal in series, The second switching circuit is inserted in a third current path between a positive electrode of the second secondary battery and the third terminal in series, The first protection IC has a first monitoring terminal connected to the first current path via a resistance between the first terminal and the first switching circuit, a first power terminal connected to a positive electrode of the second secondary battery, and a first protection element forming an internal current path from the first monitoring terminal to the first power terminal, The second protection IC has a second monitoring terminal connected to the third current path via a resistance between the third terminal and the second switching circuit, a ground terminal connected to a negative electrode of the first secondary battery, and a second protection element forming an internal current path from the ground terminal to the second monitoring terminal.

12. The secondary battery protection circuit according to any one of claims 1 to 11, characterized in that the first protection IC and the second protection IC are complexly integrated.

13. The secondary battery protection circuit according to any one of claims 1 to 11, characterized in that at least one of the pair of the first protection IC and the first switch circuit and the pair of the second protection IC and the second switch circuit is complexly integrated.

14. A battery pack, characterized by provided with: a first secondary battery and a second secondary battery connected in series; a first terminal; a second terminal; a third terminal; a current path connecting between a positive electrode of the first secondary battery and the second terminal, and being a different path from a current path between a negative electrode of the second secondary battery and the second terminal; a first switch circuit inserted in a current path between a negative electrode of the first secondary battery and the first terminal in series; a second switch circuit inserted in a current path between a negative electrode of the second secondary battery and the second terminal or a current path between a positive electrode of the second secondary battery and the third terminal in series; a first protection IC protecting at least the first secondary battery from overdischarge or discharge overcurrent by making the first switch circuit open; and a second protection IC protecting at least the second secondary battery from overdischarge or discharge overcurrent by making the second switch circuit open, when the first switch circuit is turned on by the first protection IC and the second switch circuit is turned on by the second protection IC, a first output voltage corresponding to a voltage of the first secondary battery is output from between the first terminal and the second terminal to a first load, and a third output voltage obtained by adding a second output voltage corresponding to a voltage of the second secondary battery to the first output voltage is output from between the first terminal and the third terminal to a second load, when the first switch circuit is open by the first protection IC and the second switch circuit is turned on by the second protection IC, the output of the first output voltage from between the first terminal and the second terminal to the first load is stopped, and the output of the third output voltage from between the first terminal and the third terminal is stopped, when the first switch circuit is turned on by the first protection IC and the second switch circuit is open by the second protection IC, the first output voltage is output from between the first terminal and the second terminal to the first load, and the output of the third output voltage from between the first terminal and the third terminal is stopped.

15. The battery pack according to claim 14, characterized in that When the first switch circuit is turned off by the first protection IC and the second switch circuit is turned on by the second protection IC, the current output from the second secondary battery to the first load via the first protection IC is stopped. When the first switch circuit is turned on by the first protection IC and the second switch circuit is turned off by the second protection IC, the current output from the first secondary battery to the second load via the second protection IC is stopped.

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