Secondary battery protection integrated circuit, power supply system, and battery device

Abstract

Improved convenience for deactivating the power-down state. [Solution] A secondary battery protection integrated circuit comprising a first power terminal and a second power terminal, wherein the first power terminal is connected to the first electrode of the secondary battery and the second power terminal is connected to the second electrode of the secondary battery, and the secondary battery is protected by blocking the discharge path with a discharge control transistor inserted in series with the discharge path connected to the first electrode, comprising: a first terminal connected to an external device; a second terminal connected to the discharge path; and a control circuit that transitions to a discharge interruption state that interrupts the discharge path, and conducts a first switch between the first power terminal and the first terminal and a second switch between the second power terminal and the second terminal, wherein the discharge circuit turns on the discharge control transistor when the potential difference between the first terminal and the second terminal changes from a first level in the discharge interruption state.

Description

Technical Field

[0001] The present disclosure relates to a secondary battery protection integrated circuit, a power supply system, and a battery device.

Background Art

[0002] Conventionally, there is known a circuit for protecting a secondary battery by turning off a discharge FET inserted in a charge / discharge current path between a negative electrode of the secondary battery and a negative terminal connected to a ground of a load (see, for example, Patent Document 1). This circuit includes a terminal to which a control signal is input. When the control signal is input to the terminal, the circuit powers down itself and turns off the discharge FET, thereby suppressing power consumption of the secondary battery.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the conventional technology, it is necessary to connect a charger to解除 the power-down state. Therefore, if there is no charger, the power-down state cannot be解除, and the usability may not be good.

[0005] The present disclosure provides a technology that improves the convenience of解除 the power-down state.

Means for Solving the Problems

[0006] The present disclosure includes a first power supply terminal and a second power supply terminal, A secondary battery protection integrated circuit protects the secondary battery by blocking the discharge path with a discharge control transistor inserted in series with the discharge path connected to the first electrode when the first power terminal is connected to the first electrode of the secondary battery and the second power terminal is connected to the second electrode of the secondary battery, A first terminal connected to an external device, A second terminal connected to the aforementioned discharge path, A first switch positioned between the first power terminal and the first terminal, A second switch is positioned between the second power terminal and the second terminal, The circuit includes a control circuit that transitions to a discharge interruption state that blocks the discharge path and causes the first switch and the second switch to conduct, In the discharge interruption state, the potential difference between the first terminal and the second terminal is at a first level. The control circuit provides a secondary battery protection integrated circuit that turns on the discharge control transistor when the potential difference between the first terminal and the second terminal changes from a first level. [Effects of the Invention]

[0007] According to this disclosure, the convenience of releasing the power-down state will be improved. [Brief explanation of the drawing]

[0008] [Figure 1] This figure shows an example configuration of the power supply system according to the first embodiment. [Figure 2] This is an example of a diagram showing the current path when the power switch is off during a discharge interruption state. [Figure 3] This is an example of a diagram showing the current path when the power switch is ON in a discharge interruption state. [Figure 4] This is a timing chart showing an example of operation of the power supply system according to the first embodiment. [Figure 5] This is an example of a diagram showing a first modified example of the power supply system of the first embodiment. [Figure 6]This is an example of a diagram showing a second modified example of the power supply system of the first embodiment. [Modes for carrying out the invention]

[0009] Embodiments of this disclosure will be described below with reference to the drawings.

[0010] <First Embodiment> Figure 1 shows an example configuration of a power supply system according to the first embodiment. The power supply system 401 shown in Figure 1 is a system that uses a secondary battery 70 as its power source. The power supply system 401 supplies power to an external device 301. The power supply system 401 includes a protection IC 201, a resistor 7, a power switch 40, and an external circuit 41. In this example, the protection IC 201 and the resistor 7 are provided in the battery device 101. In this example, the power switch 40 and the external circuit 41 are provided in the external device 301.

[0011] The battery device 101 comprises a secondary battery 70 and a battery protection device 80. The secondary battery 70 and the battery protection device 80 are built into the battery device 101. The battery device 101 may be built into the external device 301 or it may be externally mounted. The battery device 101 is, for example, a battery pack.

[0012] The secondary battery 70 is an example of a rechargeable battery. The secondary battery 70 supplies power to an external device 301 electrically connected to terminals P+ and P-. The secondary battery 70 can be charged by a charger electrically connected to terminals P+ and P-. Specific examples of the secondary battery 70 include lithium-ion batteries and lithium polymer batteries. The secondary battery 70 has a positive electrode 71 and a negative electrode 72.

[0013] External device 301 is an example of a load powered by the secondary battery 70 of the battery device 101. Specific examples of external device 301 include portable devices such as mobile phones, smartphones, tablets, and earphones. However, external device 301 is not limited to these devices.

[0014] The battery protection device 80 is an example of a secondary battery protection device that operates using the secondary battery 70 as a power source. The battery protection device 80 protects the secondary battery 70 from overcharging etc. by controlling the charging of the secondary battery 70, and protects the secondary battery 70 from overdischarging etc. by controlling the discharging of the secondary battery 70. The battery protection device 80 includes a terminal P+, a terminal P-, a terminal B+, a terminal B-, a resistance element 7, a switch circuit 3, and a protection IC 201. The battery protection device 80 is, for example, a component having a substrate on which the protection IC 201 is mounted.

[0015] The terminal P+ is an example of a positive load terminal, and the power line 311 of the external device 301 is electrically connected thereto. The terminal P- is an example of a negative load terminal, and the ground line 312 of the external device 301 is electrically connected thereto. The terminal B+ is an example of a positive battery terminal, and is electrically connected to the positive electrode 71 of the secondary battery 70. The terminal B- is an example of a negative battery terminal, and is electrically connected to the negative electrode 72 of the secondary battery 70.

[0016] The terminal B+ and the terminal P+ are connected by a power line 4 which is a current path on the positive side. The power line 4 is a power path between the terminal B+ and the terminal P+. The power line 4 functions as a charging path through which the charging current of the secondary battery 70 flows or a discharging path through which the discharging current of the secondary battery 70 flows. The power line 4 is an example of a charging / discharging current path between the positive electrode 71 of the secondary battery 70 and the terminal P+.

[0017] The terminal B- and the terminal P- are connected by a ground line 5 which is a current path on the negative side. The ground line 5 is a current path between the terminal B- and the terminal P-. The ground line 5 functions as a charging path through which the charging current of the secondary battery 70 flows or a discharging path through which the discharging current of the secondary battery 70 flows. The ground line 5 is an example of a charging / discharging current path between the negative electrode 72 of the secondary battery 70 and the terminal P-. Between the terminal B+ and the terminal B-, a resistor 8 and a capacitor 9 connected in series are arranged.

[0018] The switch circuit 3 is inserted in series with the ground wire 5 between terminal B- and terminal P-. The switch circuit 3 is a series circuit comprising, for example, a charge control transistor 1 and a discharge control transistor 2, with the charge control transistor 1 and the discharge control transistor 2 connected in series. The charge control transistor 1 is an example of a charge path interruption unit that interrupts the charge path of the secondary battery 70. The discharge control transistor 2 is an example of a discharge path interruption unit that interrupts the discharge path of the secondary battery 70.

[0019] In the illustrated diagram, the charge control transistor 1 blocks the ground wire 5 through which the charging current of the secondary battery 70 flows, and the discharge control transistor 2 blocks the ground wire 5 through which the discharge current of the secondary battery 70 flows. The charge control transistor 1 and the discharge control transistor 2 are switching elements that switch between conducting and blocking the ground wire 5, and are inserted in series with the ground wire 5. The charge control transistor 1 and the discharge control transistor 2 are, for example, N-channel type MOSFETs (Metal Oxide Semiconductor Field Effect Transistors).

[0020] The charge control transistor 1 has a parasitic diode 1a between its drain and source, whose forward direction is opposite to the direction of the charging current of the secondary battery 70. The charge control transistor 1 is a switch element inserted in series with the ground wire 5 such that the forward direction of the parasitic diode 1a of the charge control transistor 1 matches the direction of the discharge current flowing through the secondary battery 70.

[0021] The discharge control transistor 2 has a parasitic diode 2a between its drain and source, with its forward direction opposite to the direction of the discharge current of the secondary battery 70. The discharge control transistor 2 is a switching element inserted in series with the ground wire 5 such that the forward direction of the parasitic diode 2a of the discharge control transistor 2 matches the direction in which the charging current of the secondary battery 70 flows.

[0022] A sense resistor 6 is placed between the switch circuit 3 and terminal B-. A capacitor 10 is also connected in parallel with the sense resistor 6.

[0023] Protection IC 201 is an example of a secondary battery protection integrated circuit. Protection IC 201 operates using the secondary battery 70 as a power source. Protection IC 201 is an integrated circuit (IC) that operates using, for example, the battery voltage (also called "cell voltage") between the positive electrode 71 and the negative electrode 72 of the secondary battery 70.

[0024] The protection IC 201 protects the secondary battery 70 from over-discharge and other issues by controlling the switch circuit 3. For example, the protection IC 201 protects the secondary battery 70 from charging abnormalities (e.g., overcharging, overcurrent in the charging direction (charging overcurrent)) by turning off the charge control transistor 1. On the other hand, the protection IC 201 protects the secondary battery 70 from discharge abnormalities (e.g., over-discharge, overcurrent in the discharge direction (discharge overcurrent)) by turning off the discharge control transistor 2.

[0025] The protection IC 201 includes, for example, a charge control terminal (terminal COUT), a discharge control terminal (terminal DOUT), a monitoring terminal (terminal VM), a power terminal (terminal VDD), a ground terminal (terminal VSS), a current detection terminal (terminal CS), a control input terminal (terminal CTRL), and a power key terminal (terminal PWK). These terminals are external connection terminals for connecting the internal circuitry of the protection IC 201 to the outside of the protection IC 201.

[0026] Terminal COUT is connected to the gate (control terminal) of charge control transistor 1 and outputs a signal to turn charge control transistor 1 on and off. Terminal DOUT is connected to the gate (control terminal) of discharge control transistor 2 and outputs a signal to turn discharge control transistor 2 on and off.

[0027] Terminal VM is used to monitor the potential of terminal P- and is electrically connected to terminal P- via a resistive element 7. Terminal VM is used, for example, by a detection circuit in the protection IC 201 to monitor whether an external device 301 or a charger is connected. Terminal VM is electrically connected to the ground wire 5 between the switch circuit 3 and terminal P-.

[0028] Terminal VDD is the power terminal of the protection IC 201 and is electrically connected to the positive terminal 71 of the secondary battery 70 and the power line 4. Terminal VSS is the ground terminal of the protection IC 201 and is electrically connected to the negative terminal 72 of the secondary battery 70 and the ground wire 5. Terminal VSS is electrically connected to the ground wire 5 between the switch circuit 3 and terminal B-. In other words, terminal VSS is electrically connected to the ground wire 5 between the discharge control transistor 2 and the negative terminal 72. In this example, terminal VSS is electrically connected to the ground wire 5 between the sense resistor 6 and the negative terminal 72.

[0029] Terminal VDD is electrically connected to terminal VM within the protection IC 201 via switch SW2 and resistor Rpu. Switch SW2 is an internal switch built into the protection IC 201. Resistor Rpu is an internal resistor built into the protection IC 201.

[0030] Terminal CS is electrically connected to the ground wire 5 between the discharge control transistor 2 and the sense resistor 6 of the switch circuit 3. The sense resistor 6 is a current sensing resistor inserted in series with the ground wire 5 between the switch circuit 3 and terminal B-. The sense resistor 6 is inserted in series with the ground wire 5 between the discharge control transistor 2 and the negative electrode 72.

[0031] Terminal CTRL is electrically connected to terminal 43 of the external circuit 41 within the external device 301. Inside the protection IC 201, terminal CTRL is electrically connected to terminal VM via a control resistor Rctl. Terminal CTRL is an input terminal to which a signal is input from the external device 301. Terminal CTRL receives a predetermined first signal s1 output from the external circuit 41. The first signal s1 is, for example, a signal that commands a reduction in the power consumption of the protection IC 201, and is also called a forced shutdown signal.

[0032] Terminal PWK is electrically connected to the power switch 40 and terminal 44 of the external circuit 41. Inside the protection IC 201, terminal PWK is electrically connected to terminal VSS via switch SW1 and resistor Rpwk. Switch SW1 is an internal switch built into the protection IC 201. Resistor Rpwk is an internal resistor built into the protection IC 201.

[0033] The protection IC 201 performs protective operations for the secondary battery 70. The protection IC 201 includes an abnormality detection circuit 20 and a control circuit 21. The abnormality detection circuit 20 is an example of a means for detecting abnormalities in the current or voltage of the secondary battery 70. The control circuit 21 has a switch control circuit that controls the on / off state of the charge control transistor 1 or the discharge control transistor 2 of the switch circuit 3 based on the abnormality detection result from the abnormality detection circuit 20. The control circuit 21 and the switch control circuit are composed of, for example, logic circuits.

[0034] The abnormality detection circuit 20 monitors the power supply voltage Vd between terminal VDD and terminal VSS. When the abnormality detection circuit 20 detects a power supply voltage Vd higher than a predetermined overcharge detection voltage VDET1, the control circuit 21 turns off the charge control transistor 1. When the abnormality detection circuit 20 detects a power supply voltage Vd lower than a predetermined overcharge recovery voltage VREL1, the control circuit 21 turns on the charge control transistor 1. When the abnormality detection circuit 20 detects a power supply voltage Vd lower than a predetermined over-discharge detection voltage VDET2, the control circuit 21 turns off the discharge control transistor 2. When the abnormality detection circuit 20 detects a power supply voltage Vd higher than a predetermined over-discharge recovery voltage VREL2, the control circuit 21 turns on the discharge control transistor 2.

[0035] The protection IC 201 includes a detection circuit 23 and a comparison circuit 22.

[0036] The detection circuit 23 is electrically connected to terminal CTRL and electrically connected to terminal VM via resistor Rctrl. The detection circuit 23 monitors for the presence or absence of input of the first signal s1. If input of the first signal s1 is detected, the detection circuit 23 outputs an active-level detection signal to the control circuit 21 indicating that input of the first signal s1 is detected. If input of the first signal s1 is not detected, the detection circuit 23 outputs an inactive-level detection signal to the control circuit 21 indicating that input of the first signal s1 is not detected. If the first signal s1 is a high-level or low-level logic signal, the detection circuit 23 has a configuration that allows it to detect the logic level of that logic signal. The detection circuit 23 is, for example, a circuit including a CMOS (Complementary Metal Oxide Semiconductor) structure to which the first signal s1 is input.

[0037] The comparator circuit 22 has its output electrically connected to the control circuit 21, and its inputs electrically connected to terminals PWK and VM. The comparator circuit 22 monitors the change in the potential difference ΔV between terminals PWK and VM and outputs the monitoring result to the control circuit 21. The comparator circuit 22 includes, for example, a comparator. The comparator has a non-inverting input terminal electrically connected to terminal PWK, an inverting input terminal electrically connected to terminal VM, and an output terminal electrically connected to the control circuit 21.

[0038] The external device 301 includes a power switch 40 and an external circuit 41.

[0039] The power switch 40 is located outside the protection IC 201, and in this example, outside the battery device 101. The power switch 40 has a first switch terminal electrically connected to terminals PWK and 44, and a second switch terminal electrically connected to terminals P- and 45. The second switch terminal is electrically connected to terminal VM via terminal P- and a resistor 7. The power switch 40 is an element that can be turned on or off by user operation, for example. The power switch 40 is, for example, a switch for turning on the power to an external device 301. The power switch 40 may have a function to turn off the power to the external device 301 in addition to the function to turn it on.

[0040] The external circuit 41 operates on the power supply voltage input between terminal 42, which is electrically connected to the power line 311, and terminal 45, which is electrically connected to the ground line 312. The external circuit 41 is, for example, a semiconductor integrated circuit including a power supply circuit.

[0041] The external circuit 41 outputs a first signal s1 (forced shutdown signal) from terminal 43 when predetermined conditions (sometimes referred to as "shutdown conditions") are met. For example, the shutdown conditions include at least the case where the input voltage between terminals 42 and 45 remains below a predetermined voltage value for a predetermined input time, while the power supply voltage between terminals 42 and 45 is at or above the reset voltage. For example, by outputting the first signal s1 from terminal 43 from the external circuit 41 at the time of product shipment, the power consumption of the secondary battery 70 during product storage can be reduced.

[0042] The external circuit 41 has a diode 46 connected to terminals 44 and 45. The diode 46 is connected between terminals 44 and 45 inside the external circuit 41, but may also be connected between terminals 44 and 45 outside the external circuit 41. The diode 46 has an anode electrically connected to terminal 45 and a cathode electrically connected to terminal 44. Examples of the diode 46 include a parasitic diode that occurs between terminals 44 and 45, and an electrostatic discharge protection diode provided between terminals 44 and 45.

[0043] Next, we will explain the transitions in the operating modes of the protection IC201.

[0044] In normal mode, the control circuit 21 of the protection IC 201 turns on the charge control transistor 1 and the discharge control transistor 2. Normal mode is the state in which voltage is supplied from the secondary battery 70 to the external circuit 41. With the discharge control transistor 2 turned on, the output voltage of the battery device 101 (voltage between terminals P+ and P-) is approximately equal to the cell voltage of the secondary battery 70. In normal mode, the control circuit 21 cuts off the conduction between terminals PWK and VSS when switch SW1 is turned off, and cuts off the conduction between terminals VDD and VM when switch SW2 is turned off.

[0045] When a predetermined condition is met, the external circuit 41 of the external device 301 outputs a first signal s1 (forced shutdown signal) from terminal 43.

[0046] In normal mode, when the input of the first signal s1 is detected by the detection circuit 23, the control circuit 21 transitions the operating mode of the protection IC 201 from normal mode to ship mode. Ship mode is a mode that reduces the power consumption of the secondary battery 70 when it is stored. Ship mode is also called power save mode.

[0047] Ship mode is a discharge-blocking state in which the discharge control transistor 2 is turned off, and switches SW1 and SW2 are conductive. In ship mode, the control circuit 21 conducts between terminal PWK and terminal VSS via switch SW1 and resistor Rpwk by conducting switch SW1. In ship mode, the control circuit 21 conducts between terminal VDD and terminal VM via switch SW2 and resistor Rpu by conducting switch SW2. In ship mode, the control circuit 21 blocks the discharge path of the secondary battery 70 by turning off the discharge control transistor 2.

[0048] In ship mode, the discharge control transistor 2 is turned off, and the switch SW2 is turned on, causing the output voltage of the battery device 101 (voltage between terminals P+ and P-) to become approximately zero. As a result, the external circuit 41 stops, and the current consumption of the external device 301 is reduced. Meanwhile, in ship mode, the control circuit 21 cuts off the power supply to the abnormality detection circuit 20. Cutting off the power supply to the abnormality detection circuit 20 reduces the current consumption of the protection IC 201.

[0049] Next, we will explain the transition from ship mode to normal mode.

[0050] In ship mode, the control circuit 21 makes the connection between terminal PWK and terminal VSS conductive by conducting switch SW1, and also makes the connection between terminal VDD and terminal VM conductive by conducting switch SW2. Therefore, in ship mode, when the power switch 40 is off, current flows through the path indicated by the arrow in Figure 2. When the user turns on the power switch 40 from the state in Figure 2, current flows through the path indicated by the arrow in Figure 3.

[0051] In Figure 2, the current flows in the following order: positive terminal 71, terminal B+, terminal VDD, resistor Rpu, terminal VM, resistor element 7, terminal P-, terminal 45, diode 46, terminal 44, terminal PWK, resistor Rpwk, terminal VSS, terminal B-, and negative terminal 72. In Figure 3, the current flows in the following order: positive terminal 71, terminal B+, terminal VDD, resistor Rpu, terminal VM, resistor element 7, terminal P-, power switch 40, terminal PWK, resistor Rpwk, terminal VSS, terminal B-, and negative terminal 72. Therefore, in ship mode, the difference in the forward voltage of diode 46 between when the power switch 40 is on and when it is off results in a potential difference ΔV between terminal PWK and terminal VM. The control circuit 21 detects this change in potential difference ΔV and transitions (returns) the operating mode of the protection IC 201 from ship mode to normal mode. By turning on the power switch 40, the current path from terminal VM to terminal PWK becomes a path that goes through the power switch 40. In other words, by pressing the power switch 40, the external device 301 is started and at the same time the current path from terminal VM to terminal PWK is changed. As a result, a circuit to detect when power is supplied to the external device 301 becomes unnecessary.

[0052] In the first embodiment, the control circuit 21 turns on the discharge control transistor 2 when it detects a change in the potential difference ΔV in the discharge interruption state (ship mode). The control circuit 21 also turns off switches SW1 and SW2. For example, the potential difference ΔV when the power switch 40 is in the off state in the discharge interruption state (ship mode) is defined as the first level. At this time, when the potential difference ΔV changes from the first level in ship mode, the control circuit 21 determines that the power switch 40 has changed from the off state to the on state and turns on the discharge control transistor 2. As a result, the operating mode of the protection IC 201 transitions (returns) from ship mode to normal mode.

[0053] The first level is generated by the potential difference between terminals 45 and 44. In this example, the first level is generated by the forward voltage of diode 46 and is less than or equal to the forward voltage of diode 46. Although the potential difference across the resistor element 7 also contributes to the generation of the first level, this potential difference is smaller than the forward voltage of diode 46 and can therefore be ignored. This potential difference can also be generated by resistor elements other than diodes, transistors, etc.

[0054] In ship mode, the power supply to the external circuit 41 is cut off by the off state of the discharge control transistor 2. Therefore, the external circuit 41 cannot detect the on state of the power switch 40 and cannot output a control signal to the protection IC 201 to exit ship mode.

[0055] However, according to the first embodiment, in the discharge interruption state (ship mode), switches SW1 and SW2 are conductive, and the discharge control transistor 2 is not conductive, so the control circuit 21 can detect the change in potential difference ΔV that is linked to turning on the power switch 40. When the potential difference ΔV changes from the first level in ship mode, the control circuit 21 turns on the discharge control transistor 2, thereby transitioning (returning) the operating mode of the protection IC 201 from ship mode to normal mode. Therefore, even without connecting a charger, the ship mode is released by turning on the power switch 40, improving the convenience of releasing the power-down state.

[0056] In the first embodiment, terminal VSS is an example of a first power supply terminal. Terminal VDD is an example of a second power supply terminal. Negative electrode 72 is an example of a first electrode. Positive electrode 71 is an example of a second electrode. Ground wire 5 is an example of a discharge path connected to the first electrode. Terminal PWK is an example of a first terminal connected to an external device. Terminal VM is an example of a second terminal connected to the discharge path. Switch SW1 is an example of a first switch located between the first power supply terminal and the first terminal. Switch SW2 is an example of a second switch located between the second power supply terminal and the second terminal. Terminal 45 is an example of a third power supply terminal connected to the discharge path. Terminal 44 is an example of a third terminal connected to the first terminal. Terminal P- or terminal 45 is an example of a ground terminal.

[0057] Figure 4 is a timing chart showing an example of operation of the power supply system in the first embodiment. Figure 4 shows the transition of the operating modes of the protection IC 201. Next, Figure 4 will be described with reference to Figure 1.

[0058] In Figure 4, "CTRL" represents the voltage level of terminal CTRL (the voltage level of the first signal s1 input to terminal CTRL). "PWK" represents the voltage level of terminal PWK. "VM" represents the voltage level of terminal VM. The level difference between PWK and VM corresponds to the potential difference ΔV.

[0059] In normal mode, the control circuit 21 of the protection IC 201 turns on the charge control transistor 1 and the discharge control transistor 2.

[0060] When a predetermined condition is met, the external circuit 41 of the external device 301 activates the first signal s1 output from terminal 43 at time t1 (in this example, the logic level of the first signal s1 is set to a low level). The external circuit 41 maintains the first signal s1 in the active state for the duration that the predetermined condition is met.

[0061] In normal mode, when an active first signal s1 is input, the control circuit 21 transitions the operating mode of the protection IC 201 from normal mode to ship mode (discharge interruption state). In this example, if the active first signal s1 continues for a predetermined input time tVsp1 or longer, the control circuit 21 transitions the operating mode of the protection IC 201 from normal mode to ship mode via discharge-off mode (D-OFF mode). Here, the potential difference ΔV in normal mode is at level 0.

[0062] When the active first signal s1 is continuously input for a predetermined input time tVsp1 or longer, the control circuit 21 turns off the discharge control transistor 2 at time t2. As a result, the operating mode of the protection IC 201 transitions from normal mode to discharge-off mode.

[0063] When the discharge control transistor 2 is turned off, the output voltage of the battery device 101 becomes approximately zero, so the external circuit 41 stops, and the current consumption of the external device 301 is reduced. Meanwhile, in discharge-off mode, the control circuit 21 turns off the discharge control transistor 2 and turns on switches SW1 and SW2. As a result, when the power switch 40 is off, current flows through the path shown in Figure 2, and the voltage at terminal VM gradually increases from approximately zero. On the other hand, terminal PWK initially drops to approximately zero when switch SW1 is turned on, and then gradually increases from approximately zero due to the current flowing as shown in Figure 2. At this time, terminals VM and PWK gradually increase while maintaining the potential difference ΔV at the first level.

[0064] When the voltage at terminal VM rises above a predetermined standby voltage Vstb at time t3, the control circuit 21 transitions the operating mode of the protection IC 201 from discharge-off mode to ship mode. In ship mode, the control circuit 21 cuts off the power supply to the abnormal detection circuit 20. Cutting off the power supply to the abnormal detection circuit 20 reduces the current consumption of the protection IC 201.

[0065] Next, in ship mode, when the power switch 40 is turned on at time t4, current flows through the path shown in Figure 3, and the potential difference ΔV drops below the first level. In ship mode (discharge interruption state), when the potential difference ΔV changes from the first level and the changed level (second level) continues for a predetermined time tVrelsp1 or longer, the control circuit 21 turns on the discharge control transistor 2 and turns off switches SW1 and SW2. As a result, the operating mode of the protection IC 201 transitions (returns) from ship mode to normal mode. Note that the second level of potential difference ΔV is smaller than the first level. The output detected by the comparison circuit 22 from this change in potential difference ΔV is transmitted to the control circuit 21.

[0066] The control circuit 21 does not necessarily have to simultaneously turn on the discharge control transistor 2, turn off switch SW1, and turn off switch SW2 at time t5; a time difference may be provided between these actions.

[0067] Figure 5 shows a first modified example of the power supply system of the first embodiment. The resistor Rpwk (see Figure 1) connected in series with switch SW2 may be replaced with a constant current source 24, as shown in Figure 5. The constant current source 24 keeps the value of the current flowing in ship mode constant, as shown in Figure 2 or Figure 3, so that power consumption can be stably reduced. Similarly, the resistor Rpu (see Figure 1) connected in series with switch SW1 may also be replaced with a constant current source.

[0068] Figure 6 shows a second modified example of the power supply system of the first embodiment. The diode 11 may be mounted on the battery device 101 or placed between terminal PWK and terminal VM. The diode 11 has an anode electrically connected to terminal VM via a resistive element 7 and an anode electrically connected to terminal PWK. In ship mode, current flows through the diode 11, so a change in potential difference ΔV can be generated when the power switch 40 is on and when it is off.

[0069] Furthermore, the potential difference ΔV is generated using a circuit element (for example, a diode 46) built into the external circuit 41. As a result, an external resistor for generating the potential difference ΔV becomes unnecessary.

[0070] As described above, embodiments have been explained, but these embodiments are presented as examples only, and the present invention is not limited by these embodiments. The above embodiments can be implemented in various other forms, and various combinations, omissions, substitutions, and modifications are possible without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents.

[0071] Furthermore, for example, the positions of the charge control transistor 1 and the discharge control transistor 2 may be interchangeable with each other relative to the positions shown in the figure. Also, the switch circuit 3 may be built into the secondary battery protection integrated circuit. [Explanation of Symbols]

[0072] 1. Charge control transistor 2. Discharge control transistor 3 Switch Circuit 4 Power line 5 Ground wire 6 Sense Resistance 7 Resistor elements 8 resistors 9 Capacitors 11 diodes 20 Anomaly detection circuit 21 Control circuits 22 Comparison circuit 23 Detection Circuit 24 Constant current source 40 Power switch 41 External circuit 70 Secondary battery 71 Positive electrode 72 Negative electrode 80 Battery protection device 101 Battery device 201 Protection IC 301 External device 401 Power System

Claims

1. It is equipped with a first power terminal and a second power terminal, A secondary battery protection integrated circuit protects the secondary battery by blocking the discharge path with a discharge control transistor inserted in series with the discharge path connected to the first electrode when the first power terminal is connected to the first electrode of the secondary battery and the second power terminal is connected to the second electrode of the secondary battery, A first terminal connected to an external device, A second terminal connected to the aforementioned discharge path, A first switch positioned between the first power terminal and the first terminal, A second switch is positioned between the second power terminal and the second terminal, The control circuit includes a mechanism that transitions to a discharge interruption state that blocks the discharge path and also causes the first switch and the second switch to conduct, In the discharge interruption state, the potential difference between the first terminal and the second terminal is at a first level. The control circuit is a secondary battery protection integrated circuit that turns on the discharge control transistor when the potential difference between the first terminal and the second terminal changes from a first level.

2. The secondary battery protection integrated circuit according to claim 1, wherein the control circuit turns on the discharge control transistor when the potential difference between the first terminal and the second terminal changes from a first level in the discharge interruption state and the changed level continues for a predetermined time or longer.

3. The secondary battery protection integrated circuit according to claim 2, wherein the control circuit interrupts the first switch when the potential difference between the first terminal and the second terminal changes from a first level in the discharge interruption state and the changed level continues for a predetermined time or longer.

4. The secondary battery protection integrated circuit according to claim 3, wherein the control circuit, in the discharge interruption state, interrupts the second switch when the potential difference between the first terminal and the second terminal changes from the first level and the changed level continues for a predetermined time or longer.

5. The secondary battery protection integrated circuit according to claim 1, further comprising a comparison circuit whose output is connected to the control circuit and whose inputs are connected to the first terminal and the second terminal.

6. The device further includes an input terminal to which a signal is input from the aforementioned external device. The secondary battery protection integrated circuit according to claim 1, wherein when a first signal is input from the external device, the control circuit transitions to the discharge interruption state.

7. The external device has a third power supply terminal connected to the discharge path and a third terminal connected to the first terminal. The secondary battery protection integrated circuit according to claim 6, wherein the first level is generated by the potential difference between the third power supply terminal and the third terminal.

8. The secondary battery protection integrated circuit according to claim 7, wherein the first level is generated using the third power supply terminal and a diode connected to the third terminal.

9. The secondary battery protection integrated circuit according to claim 1, wherein the first level is generated using a diode disposed between the first terminal and the second terminal.

10. The secondary battery protection integrated circuit according to claim 8, wherein the first level is less than or equal to the forward voltage of the diode.

11. A secondary battery protection integrated circuit according to any one of claims 1 to 10, The external device is activated, and a power switch is connected to the ground terminal at one end and to the first terminal at the other end, A power supply system comprising a resistive element connected between the second terminal and the discharge path.

12. By turning on the power switch, the current path from the first terminal to the second terminal becomes a path that goes through the power switch. The power supply system according to claim 11.

13. A secondary battery protection integrated circuit according to any one of claims 1 to 10, The aforementioned secondary battery, A battery device comprising the aforementioned discharge control transistor.

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