JP5544922B2 - Protection circuit and electronic equipment - Google Patents

Description

  The present invention relates to a protection circuit that protects a secondary battery by detecting an overcharged state or an overdischarged state of a secondary battery, and in particular, a technique for reducing power consumption necessary for detecting an overcharged state or an overdischarged state. About.

  A lithium ion battery is known as a rechargeable secondary battery. Lithium ion batteries provide high voltage, high energy density, and small memory effect that reduces capacity when repeated charge and discharge is repeated. Therefore, mobile phones, notebook computers, and personal digital assistants (PDA: Widely used in portable devices such as Personal Digital Assistants).

  In general, secondary batteries require a protection circuit that monitors charge / discharge for maintaining quality and ensuring safety, but in particular, lithium-ion batteries have a voltage range in the normal use area and overcharge / overdischarge states. In order to detect overcharge and overdischarge conditions, the voltage range of the hazardous area of the battery is very close to each other, and the quality deterioration and safety are greatly affected by the overcharge and overdischarge conditions. It is necessary to always perform voltage detection at a high accuracy, for example, at a level of several tens of mV. When the overcharge state is detected, the charging is turned off, and when the overdischarge state is detected, the discharge is turned off to protect the lithium ion battery.

  In a portable device using a secondary battery such as a lithium ion battery, it is required to reduce power consumption in order to extend the driving time. For this reason, it is desirable to reduce power consumption even in a protection circuit that monitors charge and discharge. Patent Document 1 discloses a method for reducing power consumption in an overcharge detection circuit and an overdischarge detection circuit that detect an overcharge state and an overdischarge state by comparing a voltage of a secondary battery and a reference voltage with high accuracy. Describes that the operations of the overcharge detection circuit and the overdischarge detection circuit are not performed continuously but periodically with a predetermined interval.

JP-A-8-23639

  By the way, in recent years, secondary batteries have come to be used in smaller devices such as watches. In this case, the secondary battery itself must be downsized, and the battery capacity is reduced. Even in a device using such a secondary battery with a small battery capacity, further power saving is required in the protection circuit in order to extend the driving time and improve the commercial value.

  By further increasing the operation interval of the overcharge detection circuit and the overdischarge detection circuit described in Patent Document 1, it is possible to reduce power consumption, but there is a risk that detection of the dangerous area may be delayed by that amount, Maintaining quality and ensuring safety will be insufficient.

  Therefore, an object of the present invention is to provide a protection circuit capable of reducing power consumption while maintaining the detection accuracy of the limit voltage for normal operation.

In order to solve this problem, the protection circuit according to the present invention is used together with a secondary battery whose terminal voltage is equal to or lower than the upper limit voltage and a power source that generates charging power. A first path that electrically connects the secondary battery and the power source, a second path that electrically connects the secondary battery and the load, and a first switching provided on the first path. A device, a charge state detection circuit for detecting a charge state indicating whether or not the secondary battery is charged from the power source, and a terminal voltage of the secondary battery, and the terminal voltage exceeds the upper limit voltage. And detecting an overcharge detection circuit for controlling the first switching element so that the first switching element is turned off, and when the terminal voltage of the secondary battery is within the normal operation range, State of charge If the detection result is there charged, the detection of the state of charge is compared with the case of no charge, and a control circuit for controlling so as to shorten the monitoring operation interval of the over-charge detection circuit, the charging state detection detection operation interval of the circuit to detect the state of charge, characterized by longer than monitoring operation interval of the over-charge detection circuit.

The charge state detection circuit detects the charge state at a detection operation interval longer than the monitoring operation interval of the overcharge detection circuit. When charging is performed, charging current flows into the secondary battery, so that the terminal voltage of the secondary battery increases. However, when charging is not performed, the terminal voltage of the secondary battery does not increase. Therefore, the possibility of transition from the normal state to the overcharged state is higher when there is charge than when there is no charge. Therefore, in the present invention, the monitoring operation interval of the overcharge detection circuit is greater when there is a charge with a high possibility of transition to the overcharge state than when there is no charge with a low possibility of transition to the overcharge state. Control to shorten. As a result, a monitoring operation according to the state of charge can be performed, and the power consumption can be reduced while maintaining the detection accuracy of the limit voltage for normal operation.

  The other protection circuit according to the present invention is used together with a secondary battery and a power source that generates power for charging, in which the terminal voltage is not lower than the upper limit voltage and lower than the upper limit voltage. A first path for electrically connecting the secondary battery and the power source; a second path for electrically connecting the secondary battery and a load; and a first switching element provided in the first path; A second switching element provided in the second path, a charging current detection circuit for detecting a magnitude of a charging current supplied from the power source to the secondary battery, and a supply from the secondary battery to a load The discharge current detection circuit for detecting the magnitude of the discharge current and the terminal voltage of the secondary battery are monitored, and when it is detected that the terminal voltage exceeds the upper limit voltage, the first switching element is turned off. So that the first An overcharge detection circuit for controlling the switching element; and a terminal voltage of the secondary battery is monitored, and when the terminal voltage is detected to be lower than the lower limit voltage, the second switching element is turned off. When the overdischarge detection circuit that controls the second switching element and the terminal voltage of the secondary battery are within the normal operation range, the charge current is compared with the discharge current, and the charge current is When the current is larger than the current, the overcharge detection circuit is controlled so that the monitoring operation interval is shorter than the overdischarge detection circuit, and when the charging current is smaller than the discharge current, the overdischarge detection circuit A control circuit that controls the monitoring operation interval to be shorter than the monitoring operation interval of the overcharge detection circuit.

When the charging current is increased, the terminal voltage of the secondary battery is increased, and when the discharging current is increased, the terminal voltage of the secondary battery is decreased. Whether the terminal voltage of the secondary battery increases or decreases is defined by the magnitude relationship between the charging current and the discharging current. According to the present invention, when the charging current is larger than the discharging current, the monitoring operation interval of the overcharge detection circuit is controlled to be shorter than the monitoring operation interval of the overdischarge detection circuit. As a result, a monitoring operation according to the magnitude relationship between the charging current and the discharging current can be performed, and the power consumption can be reduced while maintaining the detection accuracy of the limit voltage for normal operation.
Note that “control is performed so that the monitoring operation interval of the overcharge detection circuit is shorter than the monitoring operation interval of the overdischarge detection circuit” means that “the operation of the overcharge detection circuit is stopped and the overdischarge detection circuit is The monitoring operation interval is a predetermined interval. In addition, “control so that the monitoring operation interval of the overdischarge detection circuit is shorter than the monitoring operation interval of the overcharge detection circuit” means that “the operation of the overdischarge detection circuit is stopped, The case where the monitoring operation interval is a predetermined interval is included.

The other protection circuit according to the present invention is used together with a secondary battery and a power source that generates power for charging, in which the terminal voltage is not lower than the upper limit voltage and lower than the upper limit voltage. A first path for electrically connecting the secondary battery and the power source; a second path for electrically connecting the secondary battery and a load; and a first switching element provided in the first path; A second switching element provided in the second path, a charge state detection circuit for detecting a charge state indicating whether or not the secondary battery is charged from the power source, and a discharge of the secondary battery to the load A discharge state detection circuit for detecting a discharge state indicating presence / absence and a terminal voltage of the secondary battery are monitored, and when it is detected that the terminal voltage exceeds the upper limit voltage, the first switching element is turned off. So that the first An overcharge detection circuit that controls the switching element; and the terminal voltage of the secondary battery is monitored, and when the terminal voltage is detected to be lower than the lower limit voltage, the second switching element is turned off. In the case where the overdischarge detection circuit for controlling the second switching element and the terminal voltage of the secondary battery are within the normal operation range, the charge state detection result is no charge, and the discharge state detection result is If no discharge, the monitoring operation of the over-charge detection circuit is stopped, and a control circuit that perform the monitoring operation of the over-discharge detection circuit.

When there is no charge and no discharge, the terminal voltage of the secondary battery does not change. According to the present invention, when there is no charge without and discharging, the monitoring operation of the over-charge detection circuit is stopped, because that perform the monitoring operation of the over-discharge detection circuit, while maintaining the detection precision of the threshold voltage of normal operation, It becomes possible to reduce power consumption.

  The other protection circuit according to the present invention is used together with a secondary battery and a power source that generates power for charging, in which the terminal voltage is not lower than the upper limit voltage and lower than the upper limit voltage. A first path that electrically connects the secondary battery and the power source; a second path that electrically connects the secondary battery and a load; and a second switching element provided in the second path; A charging state detection circuit for detecting a charging state indicating whether or not the secondary battery is charged from the power source; and monitoring a terminal voltage of the secondary battery and detecting that the terminal voltage is lower than the lower limit voltage Then, in the overdischarge detection circuit that controls the second switching element so that the second switching element is turned off, and when the terminal voltage of the secondary battery is within the normal operation range, the charge state Detection For fruit is there charged with a detection result of the state of charge as compared with the case of no charge, and a control circuit for controlling so as to increase the monitoring operation interval of the over-discharge detection circuit.

When charging is performed, charging current flows into the secondary battery, so that the terminal voltage of the secondary battery increases. However, when charging is not performed, the terminal voltage of the secondary battery does not increase. Therefore, the possibility of transition from the normal state to the overdischarge state is lower when there is charge than when there is no charge. Therefore, according to the present invention, the monitoring operation interval of the overdischarge detection circuit is set longer when there is a charge with a high possibility of transition to the overdischarge state than when there is no charge with a low possibility of transition to the overdischarge state. Control to make it longer. As a result, a monitoring operation according to the state of charge can be performed, and the power consumption can be reduced while maintaining the detection accuracy of the limit voltage for normal operation.
Note that “increasing the monitoring operation interval of the overdischarge detection circuit” includes stopping the monitoring operation of the overdischarge detection circuit.

  The other protection circuit according to the present invention is used together with a secondary battery and a power source that generates power for charging, in which the terminal voltage is not lower than the upper limit voltage and lower than the upper limit voltage. A first path for electrically connecting the secondary battery and the power source; a second path for electrically connecting the secondary battery and a load; and a first switching element provided in the first path; A discharge state detection circuit for detecting a discharge state indicating the presence or absence of discharge from the secondary battery to the load; and monitoring the terminal voltage of the secondary battery, and detecting that the terminal voltage exceeds the upper limit voltage An overcharge detection circuit that controls the first switching element so that the first switching element is turned off; and a terminal voltage of the secondary battery is within the range of the normal operation. Detection result And a control circuit that controls to increase the monitoring operation interval of the overcharge detection circuit as compared to the case where the discharge state detection result is no discharge when the discharge state is present.

Since discharge current flows out from the secondary battery when there is a discharge, the terminal voltage of the secondary battery decreases, but when there is no discharge, the terminal voltage of the secondary battery does not decrease. Therefore, the possibility of transition from the normal state to the overcharged state is lower when there is discharge than when there is no discharge. Therefore, the present invention provides a monitoring operation interval of the overcharge detection circuit when there is a discharge with a low possibility of transition to the overcharge state, compared with a case without discharge with a high possibility of transition to the overcharge state. Control to make it longer. As a result, a monitoring operation according to the discharge state can be performed, and the power consumption can be reduced while maintaining the detection accuracy of the limit voltage for normal operation.
Note that “increasing the monitoring operation interval of the overcharge detection circuit” includes stopping the monitoring operation of the overcharge detection circuit.

  Another protection circuit according to the present invention is used together with a power source that generates charging power and a secondary battery whose terminal voltage is not less than the lower limit voltage and not more than the upper limit voltage. A first path that electrically connects the secondary battery and the power source, a second path that electrically connects the secondary battery and the load, and a first switching provided on the first path. An element, a discharge state detection circuit for detecting a discharge state indicating whether or not to supply power from the secondary battery to a load, and a terminal voltage of the secondary battery, and the terminal voltage exceeds the upper limit voltage. In the state where the overcharge detection circuit controls the first switching element so that the first switching element is turned off, and the terminal voltage of the secondary battery exceeds the upper limit voltage, the discharge State If the detection result is there discharged, by the detection result of the discharge state is compared with the case of no discharge, and a control circuit for controlling so as to shorten the monitoring operation interval of the over-charge detection circuit.

  Since discharge current flows out from the secondary battery when there is a discharge, the terminal voltage of the secondary battery decreases, but when there is no discharge, the terminal voltage of the secondary battery does not decrease. Therefore, when there is a discharge, there is a higher possibility of transition from an overcharge state to an overdischarge state than when there is no discharge. Therefore, the present invention shortens the monitoring operation interval of the overcharge detection circuit when there is a discharge with a high possibility of transition to the normal state, compared with a case without discharge with a low possibility of transition to the normal state. To control. As a result, a monitoring operation according to the discharge state can be performed, and the power consumption can be reduced while maintaining the detection accuracy of the limit voltage for normal operation.

  Another protection circuit according to the present invention is used together with a power source that generates charging power and a secondary battery whose terminal voltage is not less than the lower limit voltage and not more than the upper limit voltage. A second path electrically connecting the secondary battery and the power source, a second path electrically connecting the secondary battery and the load, and a second switching provided in the second path. An element, a discharge current detection circuit for detecting a magnitude of a discharge current supplied from the secondary battery to the load, and a terminal voltage of the secondary battery is monitored, and the terminal voltage is less than the lower limit voltage. When detected, an overdischarge detection circuit that controls the second switching element so that the second switching element is turned off; and a state in which the terminal voltage of the secondary battery exceeds the upper limit voltage, the magnitude of the discharge current In response And a control circuit for controlling a monitoring operation interval of the overdischarge detection circuit.

When the discharge current is increased, the terminal voltage of the secondary battery is lowered. The degree to which the terminal voltage of the secondary battery decreases depends on the magnitude of the discharge current. According to the present invention, the monitoring operation interval of the overdischarge detection circuit is controlled according to the magnitude of the discharge current. As a result, a monitoring operation corresponding to the discharge current can be performed, and the power consumption can be reduced while maintaining the detection accuracy of the limit voltage for normal operation.
In addition, it is preferable that the monitoring operation interval of the overdischarge detection circuit monotonously decreases as the magnitude of the discharge current increases.

Another protection circuit according to the present invention is used together with a power source that generates charging power and a secondary battery whose terminal voltage is not less than the lower limit voltage and not more than the upper limit voltage. A second path electrically connecting the secondary battery and the power source; a second path electrically connecting the secondary battery and the load; and a second switching provided in the second path. Elements,
An overdischarge detection circuit that monitors the terminal voltage of the secondary battery and controls the second switching element to turn off the second switching element when it is detected that the terminal voltage has fallen below the lower limit voltage. And a control circuit that controls to stop the monitoring operation of the overdischarge detection circuit in a state where the terminal voltage of the secondary battery exceeds the upper limit voltage.

  The overdischarge detection circuit controls on / off of the second switching element at the lower limit voltage. Therefore, it does not operate in an overcharged state in which the terminal voltage is equal to or higher than the upper limit voltage far from the lower limit voltage. Therefore, the present invention can reduce power consumption while maintaining the detection accuracy of the limit voltage for normal operation by stopping the monitoring operation of the overdischarge detection circuit in a state where the terminal voltage exceeds the upper limit voltage. Become.

  Another protection circuit according to the present invention is used together with a power source that generates charging power and a secondary battery whose terminal voltage is not less than the lower limit voltage and not more than the upper limit voltage. A second path electrically connecting the secondary battery and the power source; a second path electrically connecting the secondary battery and the load; and a second switching provided in the second path. An element, a charge state detection circuit for detecting a charge state indicating whether or not the secondary battery is charged from the power source, and a terminal voltage of the secondary battery is monitored, and the terminal voltage falls below the lower limit voltage. And detecting an overdischarge detection circuit for controlling the second switching element so that the second switching element is turned off, and a state in which the terminal voltage of the secondary battery is lower than the lower limit voltage. Detection result If it is indicative of the presence of charge, and the detection result of the state of charge as compared with the case of no charge, and a control circuit for controlling so as to shorten the monitoring operation interval of the over-discharge detection circuit.

  When charging is performed, charging current flows into the secondary battery, so that the terminal voltage of the secondary battery increases. However, when charging is not performed, the terminal voltage of the secondary battery does not increase. Therefore, the possibility of transition from the overdischarge state to the normal state is higher when there is charge than when there is no charge. Therefore, the present invention shortens the monitoring operation interval of the overdischarge detection circuit when there is a charge with a high possibility of transition to the normal state, compared with the case without charge with a low possibility of transition to the normal state. To control. As a result, a monitoring operation according to the state of charge can be performed, and the power consumption can be reduced while maintaining the detection accuracy of the limit voltage for normal operation.

  Another protection circuit according to the present invention is a protection circuit used together with a power source that generates charging power and a secondary battery whose terminal voltage is not less than the lower limit voltage and not more than the upper limit voltage. A first path electrically connecting the secondary battery and the power source; a second path electrically connecting the secondary battery and the load; and a second path provided in the second path. The switching element, the discharge current detection circuit for detecting the magnitude of the discharge current supplied from the secondary battery to the load, and the terminal voltage of the secondary battery are monitored, and the terminal voltage falls below the lower limit voltage. And detecting an overdischarge detection circuit for controlling the second switching element so that the second switching element is turned off, and a state in which the terminal voltage of the secondary battery is lower than the lower limit voltage. In size Flip and, and a control circuit for controlling the monitoring operation interval of the over-discharge detection circuit.

When the charging current is increased, the terminal voltage of the secondary battery is increased. The extent to which the terminal voltage of the secondary battery increases depends on the magnitude of the charging current. According to the present invention, the monitoring operation interval of the overdischarge detection circuit is controlled according to the magnitude of the charging current. As a result, a monitoring operation according to the charging current can be performed, and the power consumption can be reduced while maintaining the detection accuracy of the limit voltage for normal operation.
It is preferable that the monitoring operation interval of the overdischarge detection circuit monotonously decreases as the charging current increases.

  Another protection circuit according to the present invention is used together with a power source that generates charging power and a secondary battery whose terminal voltage is not less than the lower limit voltage and not more than the upper limit voltage. A first path that electrically connects the secondary battery and the power source, a second path that electrically connects the secondary battery and the load, and a first switching provided on the first path. And monitoring the terminal voltage of the secondary battery, and detecting that the terminal voltage exceeds the upper limit voltage, the control circuit controls the first switching element to turn off the first switching element. A charge detection circuit; and a control circuit that controls to stop the monitoring operation of the overcharge detection circuit in a state where the terminal voltage of the secondary battery is lower than the lower limit voltage.

  The overcharge detection circuit controls on / off of the first switching element at the upper limit voltage. Therefore, it does not operate in an overdischarge state in which the terminal voltage falls below the lower limit voltage that is far from the upper limit voltage. Therefore, the present invention can reduce the power consumption while maintaining the detection accuracy of the limit voltage of the normal operation by stopping the monitoring operation of the overcharge detection circuit in a state where the terminal voltage is lower than the lower limit voltage. Become.

  In the protection circuit described above, it is preferable that a detection operation interval at which the charge state detection circuit detects the charge state is longer than a monitoring operation interval of the overcharge detection circuit or the overdischarge detection circuit. Thus, by performing the operation in two stages, it is possible to further reduce power consumption.

  Further, in order to solve this problem, according to the present invention, a power source that generates power for charging and a secondary that is a condition for normal operation that the terminal voltage is higher than the lower limit voltage and lower than the upper limit voltage. An electronic device including a battery, a load, and the protection circuit is provided. Since this protection circuit can reduce power consumption while maintaining the detection accuracy of the limit voltage for normal operation, it is possible to provide an electronic device with reduced power consumption while extending the life of the secondary battery.

It is a block diagram which shows the structure of the electronic device provided with the protection circuit of this embodiment. It is a figure explaining an example of the relationship between the voltage and state of a lithium ion battery. It is a figure explaining the relationship between the voltage of a secondary battery, and an operation timing. It is a figure explaining the relationship between an operation timing and current consumption. It is a timing diagram which shows the relationship between the operation interval of a discharge state and a charge condition detection, and an overcharge detection circuit and an overdischarge detection circuit detection operation interval. It is a figure which shows the circuit structural example of an overcharge detection circuit and an overdischarge detection circuit. It is a figure which shows another example of the circuit structure of an overcharge detection circuit and an overdischarge detection circuit. It is a flowchart which shows 1st Example of the operation | movement space | interval control of the overcharge detection circuit and overdischarge detection circuit by a control circuit. It is a flowchart which shows 2nd Example of the operation | movement space | interval control of the overcharge detection circuit and overdischarge detection circuit by a control circuit. It is a flowchart which shows 3rd Example of operation | movement interval control of the overdischarge detection circuit by a control circuit. It is a flowchart which shows the relationship between the discharge current and overcharge monitoring period in case the monitoring operation | movement interval is made into three steps or more in 3rd Example. It is a graph which shows the relationship between the charging current in 4th Example, and the monitoring operation interval of an overcharge detection circuit. It is a graph which shows the relationship between the differential electric current in 5th Example, and the monitoring operation | movement interval of an overcharge detection circuit and an overdischarge detection circuit. It is a flowchart which shows the control content of the monitoring operation | movement interval which concerns on 6th Example. It is a graph which shows the control content of 6th Example. It is a block diagram which shows another example of a structure of the electronic device provided with the protection circuit which concerns on a modification. It is a flowchart which shows the control content of the monitoring operation | movement interval of the protection circuit which concerns on a modification. It is a chart which shows the contents of control of a modification. It is a perspective view of the wristwatch which is an example of electronic equipment. It is a perspective view of the mobile telephone which is an example of an electronic device. It is a perspective view of the portable information terminal which is an example of an electronic device. It is a block diagram which shows another example of a structure of the electronic device provided with the protection circuit which concerns on a modification.

<1. Embodiment>
Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram illustrating a configuration of an electronic device including the protection circuit of the present embodiment. As shown in the figure, the electronic device 10 includes a rechargeable secondary battery 100, a protection circuit 200, a charging power supply 300, and a main body 400. The secondary battery 100 is charged via the protection circuit 200. The power supply 300 and the main body 400 are electrically connected. The main body 400 includes a control circuit 410 and a load 420. Therefore, the secondary battery 100 is connected to the control circuit 410 and the load 420 via the protection circuit 200. The electronic device 10 is a device that operates using the secondary battery 100 as a driving power source, and can be, for example, a wristwatch, a mobile phone, a portable information terminal, or the like.

In the present embodiment, the secondary battery 100 is a lithium ion battery. However, the secondary battery 100 may be a secondary battery other than the lithium ion battery, and the present invention can be effectively applied to a lithium ion polymer battery or the like.
FIG. 2 is a diagram illustrating an example of the relationship between the terminal voltage of the lithium ion battery used as the secondary battery 100 and the battery state. As shown in the figure, the lithium ion battery has a normal use region (normal state) in which a voltage range of 2.60 V to 4.20 V is used for normal operation.
4.20 V to 4.25 V is set as an overcharge region, and in this voltage range, characteristics deteriorate due to overcharge. If the voltage exceeds 4.25 V, the battery is in a dangerous state, and therefore, it becomes a dangerous area for which use is prohibited. The usage region above 4.2V is overcharged. On the other hand, 1.00 to 2.60 V is an overdischarge region, and in this voltage range, the characteristics are deteriorated by overdischarge. If the voltage is lower than 1.00 V, the battery is in a dangerous state, so that it becomes a use-prohibited dangerous area.

For this reason, in the present embodiment, the upper limit of the normal use region 4.20V is referred to as an overcharge detection voltage, and the lower limit of the normal use region 2.60V is referred to as an overdischarge detection voltage, thereby limiting the normal operation limit voltage. To be detected. Of course, these numerical values are examples, and are adapted to the characteristics of the secondary battery 100, the use of the electronic device 10, and the like.
In addition, as a battery state of the secondary battery 100, a terminal voltage Vx that is higher than the overdischarge detection voltage and lower than the overcharge detection voltage is referred to as a normal state in which normal operation is guaranteed, and the terminal voltage Vx exceeds the overcharge detection voltage. A state in which normal operation is not guaranteed is referred to as an overcharge state, and a state in which the terminal voltage Vx is below the overdischarge detection voltage and normal operation is not guaranteed is referred to as an overdischarge state.

  Returning to the description of FIG. 1, the protection circuit 200 detects the battery state of the secondary battery 100 (three states including an overcharge state, an overdischarge state, and a normal state), and performs the protection operation of the secondary battery 100. . Specifically, when an overcharge state is detected, the electrical connection with the charging power source 300 is interrupted, and when an overdischarge state is detected, the electrical connection with the main body 400 is interrupted. .

The charging power source 300 is a power source used for charging the secondary battery 100, and for example, a solar cell can be used. However, the charging power supply 300 may not be provided in the electronic device 10 but may be provided outside the electronic device 10 using a charger, a constant voltage power supply, or the like.
The main body 400 is a functional unit that is supplied with power from the secondary battery 100. When the electronic device 10 is applied to a wristwatch, the main body 400 corresponds to the wristwatch body, and when the electronic device 10 is applied to a mobile phone, This corresponds to the mobile phone body.

In this embodiment, the protection circuit 200 includes an overcharge detection circuit 210, an overdischarge detection circuit 220, a charge state detection circuit 230, a timing signal generation circuit 240, a charge control switch 250, a discharge control switch 260, and a diode 270. Prepare.
The charging control switch 250 is a switching element provided in a path that electrically connects the secondary battery 100 and the charging power source 300. The discharge control switch 260 is a switching element provided in a path that electrically connects the secondary battery 100 and the main body 400 (load 420). In this embodiment, a p-channel transistor is used as a switching element.

  The overcharge detection circuit 210 monitors the terminal voltage Vx of the secondary battery 100 and, when detecting that the voltage exceeds the overcharge detection voltage, causes the charge control switch 250 to transition from on to off in order to stop charging. . Specifically, the gate voltage Vg1 is changed from the low level to the high level. The detection of exceeding the overcharge detection voltage can be performed by, for example, comparing the divided voltage of the secondary battery 100 with a reference voltage corresponding to the overcharge detection voltage. In order to prevent erroneous detection due to noise or the like, the determination may be made based on a plurality of detection results.

  The overdischarge detection circuit 220 monitors the terminal voltage Vx of the secondary battery 100 and, when detecting that the voltage is lower than the overdischarge detection voltage, causes the discharge control switch 260 to transition from on to off in order to stop the discharge. . Specifically, the gate voltage Vg2 is changed from the low level to the high level. Detection that the voltage is lower than the overdischarge detection voltage can be performed by, for example, comparing the divided voltage of the secondary battery 100 with a reference voltage corresponding to the overdischarge detection voltage. In order to prevent erroneous detection due to noise or the like, the determination may be made based on a plurality of detection results.

  The charging state detection circuit 230 detects a charging state indicating whether or not the secondary battery 100 is charged in a normal state. Specifically, based on the terminal voltage Vx of the secondary battery 100 and the power supply voltage Vy of the charging power supply 300, a charging state indicating the presence or absence of charging is detected. For example, if the drop voltage of the diode 270 is Vth and the on-resistance of the charge control switch 250 is ignored, the charge state detection circuit 230 determines that the charge state is charged and Vy−Vth ≦ Vx when Vy−Vth> Vx. In this case, the charging state detection circuit 230 can set the charging state to no charging. This detection result is output to the control circuit 410. The charging state detection circuit 230 does not need to continuously detect the charging state of the secondary battery 100, and can detect the charging state of the secondary battery 100 at a predetermined interval, for example, 60 seconds. The charge state detection circuit 230 can be configured using, for example, a voltage comparator, an A / D converter, or the like.

Further, the control circuit 410 provided in the main body 400 is constituted by, for example, a CPU that controls the entire electronic device 10 and has the following functions.
First, the control circuit 410 detects the battery state of the secondary battery 100 based on the terminal voltage Vx. That is, three states are detected: an overcharge state, a normal state, and an overdischarge state. In this example, the overcharge state is assumed when the gate voltage Vg1 is high level, the normal state is assumed when the gate voltages Vg1 and Vg2 are low level, and the overdischarge is caused when the gate voltage Vg2 is high level. Suppose that it is in a state. The terminal voltage Vx may be supplied to the control circuit 410, and the control circuit 410 may determine three states such as an overcharge state, a normal state, and an overdischarge state based on the terminal voltage Vx.

Second, the control circuit 410 controls the operation of the load 420. Further, the control circuit 420 acquires the magnitude of the discharge current flowing through the load 420 and detects the presence or absence of discharge. That is, the control circuit 410 functions as a discharge current detection circuit that detects the magnitude of the discharge current supplied from the secondary battery 100 to the load 420 and also functions as a discharge state detection circuit that detects a discharge state indicating the presence or absence of discharge. To do. The load 420 is various components that consume power in the main body 400. One of the components operates, the load 420 is on and discharge occurs, all the components stop operating, and the load 420 is off and no discharge occurs. Since the control circuit 410 gives operation instructions to various components, the presence or absence of discharge is detected as a discharge state based on the operation instructions.
For example, in a wristwatch that automatically receives the time information included in the mobile phone communication signal or satellite signal, the communication module, a motor that moves the hands, a vibration motor that generates vibration, or a buzzer are loaded. It corresponds to 420. The control circuit 410 operates the communication module to acquire an accurate time when a predetermined condition is satisfied. Alternatively, the vibration motor is activated at a predetermined time, and the user is notified by vibration that the current time is the predetermined time. The control circuit 410 may measure the discharge current in order to acquire the magnitude of the discharge current flowing through the load 420, but stores a predetermined condition for executing the operation and the magnitude of the discharge current in association with each other. The control circuit 410 may acquire the magnitude of the discharge current with reference to the table.

  Fourth, the control circuit 410 generates a control signal CTL that specifies the monitoring operation timing of the overcharge detection circuit 210 and the overdischarge detection circuit 220 based on the battery state, the charge state, the discharge state, and the like.

The diode 270 is used to prevent a current from flowing from the secondary battery 100 to the charging power source 300 to adversely affect the charging power source 300.
The timing signal generation circuit 240 controls the monitoring operation timing of the overcharge detection circuit 210 and the monitoring operation timing of the overdischarge detection circuit 220 according to the control signal CTL generated by the control circuit 410. In the present embodiment, the monitoring operation timings of the overcharge detection circuit 210 and the overdischarge detection circuit 220 are changed according to the charge state and the discharge state of the secondary battery 100. The monitoring operation timings of the overcharge detection circuit 210 and the overdischarge detection circuit 220 may be synchronized or asynchronous. Further, either the monitoring operation timing of the overcharge detection circuit 210 or the monitoring operation timing of the overdischarge detection circuit 220 may be changed according to the characteristics of the secondary battery 100 or the like.

  More specifically, the timing signal generation circuit 240 determines the monitoring operation timing so that the monitoring interval of the voltage of the secondary battery 100 is shortened in a situation where the secondary battery 100 may be in an overcharged state or an overdischarged state. By changing the voltage, the detection accuracy of the limit voltage for normal operation is maintained, and in a situation where there is no risk of being immediately overcharged or overdischarged, monitoring is performed so that the voltage monitoring interval of the secondary battery 100 becomes longer. Power consumption is reduced by changing the operation timing.

There are various modes of the monitoring operation timing of the overcharge detection circuit 210 and the overdischarge detection circuit 220 controlled by the timing signal generation circuit 240, but it is complicated to cover all the modes and explain them. In this example, “solid”, “1-second cycle”, and “10-second cycle” are taken as typical examples of the monitoring operation timing. Note that “solid” means that a monitoring operation is always performed. FIG. 3 shows the monitoring operation timing of the voltage of the secondary battery and the overcharge detection circuit 210 and the overdischarge detection circuit 220.
As shown in FIG. 3, in this example, in the normal state, both the charge control switch 250 and the discharge control switch 260 are turned on.

First, in the normal state, when the detection result of the charge state is charged and the detection result of the discharge state is no discharge, the monitoring operation timing of the overcharge detection circuit 210 is set to “1 second period” or “ The monitoring operation timing of the overdischarge detection circuit 220 is “10-second cycle”.
Second, in the normal state, when the charge state detection result is “no charge” and the discharge state detection result is “discharge”, the monitoring operation timing of the overcharge detection circuit 210 is set to “10-second cycle”, and overdischarge The monitoring operation timing of the detection circuit 220 is set to “1-second cycle” or “solid”.
Third, in the normal state, when the charge state detection result is charging and the discharge state detection result is discharge, the monitoring operation timing of the overcharge detection circuit 210 is set to “one-second cycle” or “solid”. The monitoring operation timing of the overdischarge detection circuit 220 is “one-second cycle” or “solid”.
Fourth, when the charge state detection result is “no charge” and the discharge state detection result is “no discharge” in the normal state, the overcharge detection circuit 210 has a monitoring operation timing of “10-second cycle” and overdischarge The monitoring operation timing of the detection circuit 220 is assumed to be “10-second cycle”.

In other words, in the normal state, the interval of the monitoring operation timing of the overcharge detection circuit 210 is shortened when charging is performed and when charging is not performed. This is because in the case of charging, the possibility of changing from the normal state to the overcharged state due to continued charging is higher than in the case of no charging.
On the other hand, in the normal state, when there is a discharge, the interval of the monitoring operation timing of the overdischarge detection circuit 220 is made shorter than when there is no discharge. This is because in the presence of discharge, the possibility of a change from the normal state to the overdischarge state is higher than in the case of no discharge by continuing the discharge.
Here, as described above, only the overcharge detection circuit 210 may change the interval of the monitoring operation timing depending on the situation, and the overdischarge detection circuit 220 may have a fixed interval of the monitoring operation timing, or may be overdischarged. As described above, only the detection circuit 220 may change the monitoring operation timing interval according to the situation, and the overcharge detection circuit 210 may have a fixed monitoring operation timing interval.

Next, when the battery state is an overcharged state, in order to protect the secondary battery 100, the discharge control switch 260 is turned on to lower the terminal voltage Vx, while the charge control switch 250 is turned on. The terminal voltage Vx is controlled not to increase by turning it off. At this time, the interval of the monitoring operation timing of the overcharge detection circuit 210 is set to “one-second cycle” or “solid” regardless of the presence or absence of charging or the presence or absence of discharging. That is, in the overcharged state, the monitoring operation timing interval is set shorter than in the case of no charge in the normal state. Accordingly, it is possible to detect the transition from the overcharge state to the normal state without delay.
Also, the monitoring operation of the overdischarge detection circuit 220 is stopped. In order to transition from the overcharged state to the overdischarged state, it is always necessary to go through the normal state. Therefore, even if the monitoring operation is stopped in the overcharged state, it does not immediately shift to the overdischarged state, so that power consumption can be reduced while ensuring the safety of the secondary battery 100.

Next, when the battery state is an overdischarged state, in order to protect the secondary battery 100, the charge control switch 250 is turned on to increase the terminal voltage Vx, while the discharge control switch 260 is turned on. The terminal voltage Vx is controlled not to drop by turning off. At this time, the interval of the monitoring operation timing of the overdischarge detection circuit 220 is set to “10-second period” regardless of the presence or absence of charging or the presence or absence of discharging. Thereby, it becomes possible to detect without delay from the normal state to the overcharged state. Also, in the overdischarge state, the charge control switch is turned off and the power supply to the main body 400 is stopped, so there is no discharge to the load 420. Compared to the case where there is discharge in the normal state. The monitoring operation timing interval is set longer.
Further, the monitoring operation of the overcharge detection circuit 210 is stopped. In order to transition from the overdischarged state to the overcharged state, it is always necessary to go through the normal state. Therefore, even if the monitoring operation is stopped in the overdischarged state, it does not immediately shift to the overcharged state, so that the power consumption can be reduced while ensuring the safety of the secondary battery 100.

Here, the current consumed by the detection circuit (overcharge detection circuit 210, overdischarge detection circuit 220) in the case of “solid”, “1 second period”, and “10 second period” of the monitoring operation timing will be specifically described. To do. It is assumed that one detection operation is performed in 0.1 seconds, and during that time, a current of 3.0 μA flows through the detection circuit.
FIG. 4A shows the current flowing through the detection circuit when the voltage of the secondary battery 100 is continuously detected with “solid”, that is, with an operation interval of zero. In the example of this figure, in the case of “solid”, 3.0 μA is consumed per second.

FIG. 4B shows the current flowing through the detection circuit when the voltage of the secondary battery 100 is detected at “one-second period”. The detection time is 0.1 seconds, and the detection operation is paused for 0.9 seconds thereafter, and no current is consumed. In the example of this figure, in the case of “1 second period”, 0.3 μA is consumed per second (3.0 μA × 0.1 second / 1 second).
FIG. 4C shows the current flowing through the detection circuit when the voltage of the secondary battery 100 is detected at “10-second period”. The detection time is 0.1 second, and thereafter, the detection operation is paused for 9.9 seconds, and no current is consumed. In the example of this figure, in the case of “10-second period”, 0.03 μA is consumed per second (3.0 μA × 0.1 seconds / 10 seconds).

  Assuming that the capacity of the secondary battery 100 is 10 mAH and the current consumed by the load 420 is 0.5 μA, it is considered that two detection circuits, an overcharge detection circuit 210 and an overdischarge detection circuit 220, are used. The driving time in the case of “solid” is 10 mAH [battery capacity] / (0.5 uA [load operation] +3 uA [overcharge detection] +3 uA [overdischarge detection]) / 24 hours = 64 days = about 2 A month.

Similarly, the driving time in the case of “1-second cycle” is 10 mAH [battery capacity] / (0.5 uA [load operation] +0.3 uA [overcharge detection] +0.3 uA [overdischarge detection]) / 24 Time = 379 days = about one year.
Further, when the driving time in the case of “10-second cycle” is obtained, 10 mAH [battery capacity] / (0.5 uA [load operation] +0.03 uA [overcharge detection] +0.03 uA [overdischarge detection]) / 24 hours = 744 days = about 2 years.
Therefore, by setting the monitoring operation timing of the detection circuit to a period of 10 seconds as much as possible, it is possible to reduce power consumption and extend the driving time.

  Further, in the example illustrated in FIG. 5, the charging state detection interval by the charging state detection circuit 230 is controlled to be longer than the monitoring operation interval of the overcharge detection circuit 210. That is, the monitoring operation of the overcharge detection circuit 210 is either a 1-second cycle or a 10-second cycle, whereas the detection operation of the charge state detection circuit 230 is a 60-second cycle. Further, in the normal state, the control circuit 410 controls the operation of the load 420, and therefore always knows the discharge state.

As described above, the detection result of the charge state detection circuit 230 is used to determine the possibility that the secondary battery 100 transitions from the normal state to the overcharge / discharge state. The high accuracy as the detection accuracy of the overcharge detection circuit 210 is not required. Therefore, the detection interval of the charging state by the charging state detection circuit 230 is longer than the monitoring operation interval of the overcharge detection circuit 210. Thereby, the electric energy consumed by detection of the charging state of the secondary battery 100 by the charging state detection circuit 230 can be reduced.
In this example, in the periods T1 to T4, the terminal voltage Vx is in the range from 2.6V to 4.2V, and the battery state is the normal state.

In the period T1, the charge state detection result is no charge, and the discharge state detection result is also no discharge. Therefore, the monitoring operation interval of the overcharge detection circuit 210 is set to 10 seconds, and the monitoring operation interval of the overdischarge detection circuit 220 is set to 10 seconds.
Next, in the period T2, the charge state detection result indicates that there is a charge, and the discharge state detection result indicates that there is no discharge. Since the terminal voltage Vx may exceed the overcharge detection voltage due to charging, the monitoring operation interval of the overcharge detection circuit 210 is set to 1 second, and the monitoring operation interval of the overdischarge detection circuit 220 is set to 10 seconds.

Next, in the period T3, the detection result of the charging state is charging, and the detection result of the discharging state is also discharging. Since the terminal voltage Vx may exceed the overcharge detection voltage due to charging, the monitoring operation interval of the overcharge detection circuit 210 may be set to 1 second, and the terminal voltage Vx may fall below the overdischarge detection voltage due to discharge. The monitoring operation interval between the overcharge detection circuit 210 and the overdischarge detection circuit 220 is set to 1 second.
Next, in the period T4, the charge state detection result is “no charge”, and the discharge state detection result is “discharge”. Since the terminal voltage Vx may fall below the overdischarge detection voltage due to discharge, the monitoring operation interval of the overdischarge detection circuit 220 is set to 1 second, and the monitoring operation interval of the overcharge detection circuit 210 is set to 10 seconds.

  Note that the overcharge detection circuit 210 and the overdischarge detection circuit 220 can be configured by a circuit as shown in FIG. 6, for example. In the example of this figure, in any of the detection circuits, a voltage obtained by dividing the voltage VB of the secondary battery 100 by the resistor R11 (R21) and the resistor R12 (R22) is used as a detection voltage using the comparator Cmp1 (Cmp2). By comparing with the corresponding reference voltage V1 (V2), it is detected that the detection voltage has been exceeded (below), and the charge control switch 250 (discharge control switch 260) is detected via the latch circuit 211 (221). ) To control. Here, reference numerals without parentheses indicate the configuration of the overcharge detection circuit 210, and reference numerals in parentheses indicate the configuration of the overdischarge detection circuit 220.

  The monitoring operation based on the comparison with the reference voltage V1 (V2) is performed by the comparators Cmp1 (Cmp2) by the switches Sw11 (Sw21) and Sw12 (Sw22), which are switched on and off by the timing signal TS1 (TS2) from the timing signal generation circuit 240. The monitoring operation interval is controlled by turning on / off the power supply to).

  That is, when the monitoring operation is performed with “solid”, the switch Sw11 (Sw21) and the switch Sw12 (Sw22) are always turned on, and when the monitoring operation is performed with “one second period”, the switch Sw11 (Sw21). The switch Sw12 (Sw22) is repeatedly turned on and off at a cycle of 1 second, and when the monitoring operation is performed at a cycle of 10 seconds, the switch Sw11 (Sw21) and the switch Sw12 (Sw22) are turned on and off at a cycle of 10 seconds. Like that.

Or you may comprise the overcharge detection circuit 210 and the overdischarge detection circuit 220 with a circuit as shown in FIG. In the example of this figure, as indicated by a broken-line rectangle C, a resistor that divides the voltage VB of the secondary battery 100 is configured by a resistor R1, a resistor R2, and a resistor R3, and an overcharge detection circuit 210, an overdischarge detection circuit 220, To share. With such a configuration, power consumption in the detection circuit can be further reduced.
Next, various embodiments will be described with respect to specific control contents of the monitoring operation interval between the overcharge detection circuit 210 and the overdischarge detection circuit 220 by the control circuit 410.

<1-1: First Example>
FIG. 8 is a flowchart showing a first embodiment of the operation interval control of the overcharge detection circuit 210 by the control circuit 410 in the normal state. The process of this flowchart is executed every time the state of charge detection circuit 230 detects the state of charge.
First, the control circuit 410 acquires the charge state detected by the charge state detection circuit 230 (S101), and determines whether or not the detection result of the charge state is being charged (S102). If charging is in progress, the monitoring operation interval of the overcharge detection circuit 210 is set to a 1-second cycle (S103), and if not charging, the monitoring operation interval of the overcharge detection circuit 210 is set to a 10-second cycle (S104). ). In the determination of whether or not charging is in progress, it may be determined that charging is being performed or charging is not being performed when a plurality of determination results match. If only the detection result of one charge state is used, an erroneous determination may occur due to noise, but the determination accuracy can be improved by using a condition that the determination results are matched a plurality of times.

  That is, when the charge state detection result indicates that there is a charge, the monitoring operation interval of the overcharge detection circuit 210 is set shorter than in the case where there is no charge. As a result, when the possibility of exceeding the overcharge detection voltage is high, the number of monitoring operations per unit time can be increased to protect the secondary battery 100 from overcharge, while the possibility of exceeding the overcharge detection voltage is possible. When is low, power consumption can be reduced by reducing the number of monitoring operations per unit time.

<1-2: Second Embodiment>
FIG. 9 is a flowchart showing a second embodiment of the operation interval control of the overdischarge detection circuit 220 by the control circuit 410 in the normal state. The processing of this flowchart is executed at a predetermined cycle.
First, the control circuit 410 acquires a discharge state (S201). In the normal state, since the control circuit 410 controls the operation of the load 420, the control circuit 410 always knows the discharge state. Next, the control circuit 410 determines whether or not the detection result of the discharge state is discharging (S202). Specifically, when any one of the components of the load 420 is operated, the discharge is being performed. If discharging is in progress, the monitoring operation interval of the overdischarge detection circuit 220 is set to a 1-second cycle (S203). If not discharging, the monitoring operation interval of the overdischarge detection circuit 220 is set to a 10-second cycle (S204). ). In order to avoid erroneous determination due to noise, in the determination of whether or not the discharge is in progress, it may be determined that the discharge is being performed or the discharge is not being performed when the determination results of a plurality of times match.

  That is, when the discharge state detection result indicates that there is a discharge, the monitoring operation interval of the overdischarge detection circuit 220 is set shorter than when there is no discharge. As a result, when the possibility of falling below the overdischarge detection voltage is high, the number of monitoring operations per unit time can be increased to protect the secondary battery 100 from overdischarge, while the possibility of falling below the overdischarge detection voltage. When is low, power consumption can be reduced by reducing the number of monitoring operations per unit time.

<1-3: Third embodiment>
Next, control of the monitoring operation interval of the overdischarge detection circuit 220 based on the magnitude of the discharge current will be described.
FIG. 10 is a flowchart showing a third embodiment of the operation interval control of the overdischarge detection circuit 220 by the control circuit 410 in the normal state. As described above, the control circuit 410 functions as a discharge current detection circuit. First, when the load 420 becomes heavier than normal, the control circuit 410 sets the monitoring operation interval of the overdischarge detection circuit 220 to 1 second (S301). As an example of a heavy load, the case where the communication module is activated and the time is adjusted corresponds. In this case, a large discharge current flows from the secondary battery 100 to the load 420. As a result, the terminal voltage Vx may drop and fall below the overdischarge detection voltage. Therefore, the monitoring operation interval of the overdischarge detection circuit 220 is set as short as 1 second. Then, the control circuit 410 starts heavy load operation (S302), and stops heavy load operation when a predetermined condition is satisfied (S303). Thereafter, the control circuit 410 sets the monitoring operation interval of the overdischarge detection circuit 220 to 10 seconds (S304).

  Here, focusing on the magnitude of the discharge current, the discharge current is large while the heavy load is operating, and the discharge current is small while the heavy load is stopped. That is, the control circuit 410 performs control so that the monitoring operation interval of the overdischarge detection circuit 220 is shorter when the discharge current is large than when the discharge current is small. As a result, when the discharge current is large and the possibility of transition to the overdischarge state is high, the number of detections per unit time of the discharge state is increased, and the discharge current is small and the possibility of transition to the overdischarge state is low. Can reduce the number of detections of the discharge state per unit time. As a result, the terminal voltage Vx of the secondary battery 100 can be prevented from falling below the overdischarge detection voltage, the secondary battery 100 can be protected, and power consumption can be reduced.

  In this example, the monitoring operation interval is set to two stages of 1 second and 10 seconds, but may be three or more stages as shown in FIG. In this example, the monitoring operation interval is “solid” at 100 mA or more, that is, constant monitoring, the monitoring operation interval is “1 second” at 10 mA or more and less than 100 mA, the monitoring operation interval is “5 seconds” at 0.1 mA or more and less than 10 mA, 0.1 mA. When the monitoring operation interval is “10 seconds” at less than 1 mA, more than 0.1 mA, less than 1 mA, “10 seconds”, more than 0 mA, less than 0.1 mA, and “30 seconds” at 0 mA Stop operation. That is, as the discharge current increases, the monitoring operation interval only needs to monotonously decrease. Thereby, it is possible to further balance the protection of the secondary battery 100 and the reduction of power consumption. In this example, as the discharge current increases, the monitoring operation interval decreases monotonically in a stepwise manner, but may continuously decrease monotonously. Further, “solid” can be regarded as the monitoring operation interval becoming zero, and the operation stop can be regarded as the monitoring operation interval becoming infinite.

<1-4: Fourth Embodiment>
The fourth embodiment of the operation interval control by the control circuit 410 in the normal state relates to the relationship between the magnitude of the charging current and the monitoring operation interval of the overcharge detection circuit 210. The charging current acts in the direction of increasing the terminal voltage Vx of the secondary battery 100. Therefore, when the charging current flows in the normal state, the terminal voltage Vx gradually increases and exceeds the overcharge detection voltage, and there is a possibility that the overcharge state is entered. Therefore, in the fourth embodiment, the monitoring operation interval of the overcharge detection circuit 210 is switched according to the magnitude of the charging current as shown in FIG.

  In this example, a solar cell is used as the charging power source 300. The solar cell generates a charging current having a magnitude corresponding to the illuminance. In this embodiment, the magnitude of the charging current is detected by the charging state detection circuit 230. There are various methods for detecting the charging current. In this example, the charging current is detected based on the power supply voltage Vy. The electromotive voltage of the solar cell is determined according to the illuminance, and the charging current increases as the electromotive voltage increases. Therefore, the charging current can be specified from the power supply voltage Vy. The power supply voltage Vy may be supplied to the control circuit 410 and the control circuit 410 may specify the magnitude of the charging current.

In the example shown in FIG. 12, when the illuminance is 0 lux, the charging current is 0 mA. At this time, the control circuit 410 stops the operation of the overcharge detection circuit 210. This is because there is no possibility of transition from the normal state to the overcharged state due to the terminal voltage Vx rising because there is no charging current.
Further, when the illuminance exceeds 0 lux and is less than 1000 lux, the charging current exceeds 0 mA and is less than 0.1 mA. At this time, the control circuit 410 sets the monitoring operation interval of the overcharge detection circuit 210 to 30 seconds. Next, when the illuminance exceeds 1000 lux and is less than 5000 lux, the charging current exceeds 0.1 mA and is less than 1 mA. At this time, the control circuit 410 sets the monitoring operation interval of the overcharge detection circuit 210 to 10 seconds. Next, when the illuminance exceeds 5000 lux and is less than 10000 lux, the charging current exceeds 1 mA and is less than 10 mA. At this time, the control circuit 410 sets the monitoring operation interval of the overcharge detection circuit 210 to 1 second. Next, when the illuminance is 10,000 lux or more, the charging current becomes 10 mA or more. At this time, the control circuit 410 sets the monitoring operation interval of the overcharge detection circuit 210 to be solid.

  The relationship between the charging current and the monitoring operation interval may be such that the monitoring operation interval monotonously decreases as the charging current increases. Thereby, it is possible to further balance the protection of the secondary battery 100 and the reduction of power consumption. In this example, as the charging current increases, the monitoring operation interval decreases monotonically in a stepwise manner, but may continuously decrease monotonously.

<1-5: Fifth embodiment>
The third embodiment described above focuses on the discharge current, and the fourth embodiment focuses on the charging current. The terminal voltage Vx of the secondary battery 100 is determined by the charging current flowing into the secondary battery 100 and the discharging current flowing out from the secondary battery 100. In the fifth embodiment, the monitoring operation interval between the overcharge detection circuit 210 and the overdischarge detection circuit 220 is controlled based on the difference between the discharge current and the charge current.

  In the fifth embodiment, the control circuit 410 first calculates a differential current between the discharge current and the charging current. Secondly, the monitoring operation interval of the overcharge detection circuit 210 and the overdischarge detection circuit 220 is set corresponding to the differential current. FIG. 13 shows the relationship between the differential current and the monitoring operation interval of the overcharge detection circuit 210 and the overdischarge detection circuit 220. The control circuit 410 determines the monitoring operation interval with reference to the table storing the relationship shown in FIG.

  In this example, when the differential current exceeds 0 mA, that is, when the discharge current is larger than the charging current, the operation of the overcharge detection circuit 210 is stopped. This is because if the discharge current is larger than the charging current, the terminal voltage Vx decreases, so there is no possibility of transition from the normal state to the overcharged state. On the other hand, since the terminal voltage Vx decreases, there is a possibility of transition from the normal state to the overdischarge state. And the possibility that it will change to an overdischarge state becomes high, so that differential current is large. For this reason, the control circuit 410 performs control so as to shorten the monitoring operation interval of the overdischarge detection circuit 220 as the differential current increases.

  When the differential current is 0 mA, that is, when the discharge current and the charging current are equal, the terminal voltage Vx does not change. For this reason, a normal state is maintained and it does not change to an overcharge state and an overdischarge state. Therefore, when the differential current is 0 mA, the control circuit 410 stops the operations of the overcharge detection circuit 210 and the overdischarge detection circuit 220 to reduce power consumption.

  Next, when the differential current is less than 0 mA, that is, when the charging current is larger than the discharging current, the operation of the overdischarge detection circuit 220 is stopped. This is because if the charging current is larger than the discharging current, the terminal voltage Vx increases, so there is no possibility of transition from the normal state to the overdischarge state. On the other hand, since the terminal voltage Vx increases, there is a possibility of transition from the normal state to the overcharge state. And possibility that it will change to an overcharge state becomes high, so that difference current is small. For this reason, the control circuit 410 performs control so that the monitoring operation interval of the overcharge detection circuit 210 is shortened as the differential current becomes smaller.

<1-6: Sixth embodiment>
FIG. 14 is a flowchart showing the control contents of the monitoring operation interval according to the sixth embodiment. However, it is assumed that this control is in a normal state. In this example, it is assumed that the charging current of the solar cell is 10 mA, the heavy load is a communication module, and the discharging current is 100 mA.

First, when the charging state detection circuit 230 detects the charging state (S401), the control circuit 410 determines whether or not the detection result of the charging state is being charged (with charging) (S402). If charging is in progress, it is further determined whether or not discharging is in progress (S403). If the determination condition in step S403 is affirmed, that is, if charging and discharging are present, the control circuit 410 stops the operation of the overcharge detection circuit 210 and sets the monitoring operation interval of the overdischarge detection circuit 220 to 1. Seconds are set (S404).
On the other hand, when the determination condition of step S403 is negative, that is, when charging is performed and discharging is not performed, the control circuit 410 sets the monitoring operation interval of the overcharge detection circuit 210 to be solid and monitors the overdischarge detection circuit 220. The operation interval is set to 10 seconds (S405).

  On the other hand, when the charge state detection result indicates that there is no charge and the determination condition in step S402 is negative, the control circuit 410 determines whether or not discharging is in progress (S406). When the determination condition in step S406 is affirmative, that is, when there is no charge and there is discharge, the control circuit 410 sets the monitoring operation interval of the overcharge detection circuit 210 to 10 seconds and the monitoring operation of the overdischarge detection circuit 220. The interval is set to be solid (S407). On the other hand, when the determination condition of step S406 is negative, that is, when there is no charge and no discharge, the control circuit 410 sets the monitoring operation interval of the overcharge detection circuit 210 to 30 seconds, and the overdischarge detection circuit 220 The monitoring operation interval is stopped (S408).

As derived from the flowchart of FIG. 14, in the sixth embodiment, the control as shown in FIG. 15 is performed. In this case, as shown in the figure, the monitoring operation of the overcharge detection circuit 210 is stopped when there is charge and discharge in the normal state. This is because the discharge current is 100 mA and the charging current is 10 mA, and the discharging current is sufficiently larger than the charging current. In this case, the differential current is 90 mA. Referring to the relationship shown in FIG. 13, the overcharge monitoring operation is stopped, while the overdischarge monitoring operation is executed at 1 second intervals.
Thus, in the present embodiment, when charging and discharging are performed simultaneously, the monitoring operation interval is controlled based on the differential current, so that the secondary battery 100 is reliably protected while reducing current consumption. be able to.

<2. Variation example>
The present invention is not limited to the above-described embodiments, and for example, various modifications described below are possible.
(1) In the embodiment described above, the control circuit 410 provided in the main body 400 controls the overcharge detection circuit 210 and the overdischarge detection circuit 220 in the protection circuit 200, but the present invention is not limited to this. Instead, the control circuit 410 may be provided in the protection circuit 200 as shown in FIG. In this case, since the control circuit 410 is constantly supplied with power, the control circuit 410 can operate even when the discharge control switch 260 is turned off. The control circuit 410 receives a signal indicating the magnitude of the discharge current from the CPU 421 of the main body 400. Note that a resistor may be provided in a path from the discharge control switch 260 to the main body 400, and a discharge current detection circuit that measures the voltage at both ends thereof may be provided in the protection circuit 200.

  FIG. 17 shows the control contents of the monitoring operation interval of the overcharge detection circuit 210 and the overdischarge detection circuit 220. First, the control circuit 410 detects a battery state based on the gate voltage Vg1 and the gate voltage Vg2 (S501). That is, the control circuit 410 determines that the terminal is discharged when the terminal voltage Vx falls below the overdischarge detection voltage (2.6V), and if the terminal voltage Vx is equal to or higher than the overdischarge detection voltage and equal to or lower than the overcharge detection voltage. When the terminal voltage Vx exceeds the overcharge detection voltage, it is determined that the battery is in the overcharge state.

  Next, the control circuit 410 determines whether or not the battery state is an overcharged state (S502). If the battery state is an overcharged state, it is further determined whether or not the discharge state detection result indicates that there is a discharge (see FIG. S503). When there is a discharge, the control circuit 410 controls the overcharge detection circuit 210 so that the monitoring operation interval is 1 second, and stops the overdischarge detection circuit 220 (S504). On the other hand, when the discharge state detection result indicates no discharge, the overcharge detection circuit 210 is controlled so that the monitoring operation interval is 10 seconds, and the overdischarge detection circuit 220 is stopped (S505).

  Next, when the determination condition in step S502 is negative, the control circuit 410 determines whether or not the battery state is an overdischarged state (S505). It is determined whether or not the result is charged (S506). When there is a charge, the control circuit 410 performs control so that the monitoring operation interval of the overdischarge detection circuit 220 is 1 second, and stops the monitoring operation of the overcharge detection circuit 210 (S507). On the other hand, when the charge state detection result indicates no charging, control is performed so that the monitoring operation interval of the overdischarge detection circuit 220 is 10 seconds, and the monitoring operation of the overcharge detection circuit 210 is stopped (S508).

  Moreover, when the determination condition of step S505 is denied, the battery state becomes the normal state. In this case, the control circuit 410 executes the normal process described in the above-described embodiment (S509). As derived from the flowchart of FIG. 17, in the modified example, control as shown in FIG. 18 is performed.

  That is, the control circuit 410 performs control so that the monitoring operation interval of the overcharge detection circuit 210 is shorter in the overcharge state when the detection result of the discharge state is with discharge than when there is no discharge. This is because when there is a discharge, the terminal voltage Vx may drop and fall below the overdischarge detection voltage to transition to a normal state, but when there is no discharge, the terminal voltage Vx is maintained and a transition to a normal state is possible. This is because the nature is low. As described above, in the overcharge state, the monitoring operation interval of the overcharge detection circuit 210 is controlled according to the presence or absence of discharge, so that the power consumption can be reduced while the secondary battery 100 is appropriately protected.

  In addition, the control circuit 410 performs control so that the monitoring operation interval of the overdischarge detection circuit 220 is shortened in the overdischarge state when the charge state detection result indicates that there is charge compared to the case where there is no charge. This is because the terminal voltage Vx rises and exceeds the overcharge detection voltage when there is a charge and may transition to the normal state, but when there is no charge, the terminal voltage Vx is maintained and the transition to the normal state is possible. This is because the nature is low. As described above, in the overdischarge state, the monitoring operation interval of the overcharge detection circuit 210 is controlled according to the presence / absence of discharge, so that the power consumption can be reduced while appropriately protecting the secondary battery 100.

In the overcharge state, the monitoring operation interval of the overcharge detection circuit 210 may be controlled according to the magnitude of the discharge current. If the magnitude of the discharge current increases, the terminal voltage of the secondary battery decreases quickly, so that the possibility of transition from the overcharge state to the normal state is increased because the terminal voltage is lower than the overcharge detection voltage. That is, the larger the discharge current, the higher the possibility that it will fall below the overcharge detection voltage in a shorter time. Therefore, it is preferable to perform control so that the monitoring operation interval of the overcharge detection circuit 210 monotonously decreases as the discharge current increases.
In the overdischarge state, the monitoring operation interval of the overcharge detection circuit 210 may be controlled according to the magnitude of the charging current. If the magnitude of the charging current increases, the terminal voltage of the secondary battery rises faster, so that the overdischarge detection voltage is increased by that much and the possibility of transition from the overdischarge state to the normal state increases. That is, the higher the charging current, the higher the possibility that the overdischarge detection voltage will be exceeded in a shorter time. Therefore, it is preferable to perform control so that the monitoring operation interval of the overcharge detection circuit 210 monotonously decreases as the charging current increases.

(2) In the embodiment and the modification described above, the terminal voltage of the secondary battery 100 is monitored using the overcharge detection circuit 210, and when the overcharge detection voltage is detected, the charge control switch 250 is turned off. I made it. Moreover, the terminal voltage of the secondary battery 100 was monitored using the overdischarge detection circuit 220, and when it was detected that the voltage was below the overdischarge detection voltage, the discharge control switch 260 was turned off. This is based on the premise that a lithium ion battery or the like having dangerous areas on the high potential side and the low potential side is used as the secondary battery 100. The present invention is not limited to this, and a nickel-cadmium battery or the like having a dangerous area on the high potential side and no dangerous area on the low potential side may be used as the secondary battery 100. In this case, since there is no danger region on the low potential side, the overdischarge detection circuit 220 and the discharge control switch 260 can be omitted.

  In this case, it is assumed that the protection circuit 200 is used together with a charging power source 300 that generates charging power and the secondary battery 100 whose terminal voltage is equal to or lower than the upper limit voltage. The protection circuit 200 electrically connects the secondary battery 100 and the load 420 to the charge control switch 250 provided in the first path that electrically connects the secondary battery 100 and the charging power source 300. The second path to be connected, the charge state detection circuit 230 for detecting the terminal voltage of the secondary battery 100, and the terminal voltage of the secondary battery are monitored, and when it is detected that the terminal voltage exceeds the upper limit voltage, the charge control is performed. The overcharge detection circuit 210 that controls the switch 250 to be turned off, and the monitoring operation interval of the overcharge detection circuit 210 is controlled according to the terminal voltage of the secondary battery 100 detected by the charge state detection circuit 230. A timing signal generation circuit 240.

(3) In the embodiment and the modification described above, the same overcharge detection voltage is used in the case of transition from the normal state to the overcharge state and in the case of transition from the overcharge state to the normal state. The present invention is not limited to this. When the first overcharge detection voltage is exceeded, the normal state transitions to the overcharge state, and when the second overcharge detection voltage falls below, the overcharge state transitions to the normal state. Also good. In this case, the first overcharge detection voltage is set higher than the second overcharge detection voltage. In this way, the control system can be stabilized by giving hysteresis characteristics to the state transition.
Further, when the voltage is lower than the first overdischarge detection voltage, the normal state may be changed to the overdischarge state, and when the second overdischarge detection voltage is exceeded, the overdischarge state may be changed to the normal state. In this case, the first overdischarge detection voltage is set lower than the second overdischarge detection voltage. In this way, the control system can be stabilized by giving hysteresis characteristics to the state transition.

(4) In the embodiment and the modification described above, the protection circuit 200 is provided with the diode 270 to connect the secondary battery 100 and the load 410 to the first path that connects the secondary battery 100 and the charging power source 300. A second path was provided independently. The present invention is not limited to this, and the first route and the second route may be shared.

FIG. 22 shows a circuit configuration of an electronic device using the protection circuit 205 according to the modification. In this example, a charge control switch 251 and a discharge control switch 261 are provided in one path connecting the first terminal Ta and the second terminal Tb. A diode 271 is provided between the charging power supply 300 and the second terminal Tb, and the main body 400 is connected to the second terminal Tb.
Here, the protection circuit 205 turns on the charge control switch 251 and the discharge control switch 261 in a normal state where the terminal voltage Vx of the secondary battery 100 is not less than the overdischarge detection voltage and not more than the overcharge detection voltage.

Further, the protection circuit 205 turns the charge control switch 251 on and the discharge control switch 261 off in the overdischarge state where the terminal voltage Vx of the secondary battery 100 is lower than the overdischarge detection voltage. In this case, the charging current can be supplied to the secondary battery 100 via a parasitic diode formed in parallel with the discharge control switch 261.
Further, in the overcharge state in which the terminal voltage Vx of the secondary battery 100 exceeds the overcharge detection voltage, the protection circuit 205 turns the charge control switch 251 off and the discharge control switch 261 on. In this case, the discharge current can be supplied to the main body 400 via a parasitic diode formed in parallel with the charge control switch 251.

<3. Electronic equipment>
The protection circuits described in the above-described embodiments and modifications can be applied to various electronic devices.
FIG. 19 shows a configuration of a wristwatch to which an electronic device including the protection circuit according to the present invention is applied. The wrist watch 2000 includes a time display unit including a dial plate 2002 and a hand 2003. An opening is formed in a part of the dial plate 2002 and a solar cell 2004 is provided. The solar cell 2004 is an example of the charging power supply 300 described above. The wristwatch 2000 is provided with a crown 2005 and buttons 2006 and 2007. The secondary battery 100 is used as a driving power source for the wristwatch 2000, and the protection circuit according to the present invention is used to protect the secondary battery 100 from the overcharged state and the overdischarged state.

  FIG. 20 illustrates a configuration of a mobile phone to which an electronic device including the protection circuit according to the present invention is applied. The cellular phone 3000 includes a plurality of operation buttons 3001, scroll buttons 3002, and a liquid crystal device 3003. The secondary battery 100 is used as a driving power source for the mobile phone 3000, and the protection circuit according to the present invention is used to protect the secondary battery 100 from the overcharged state and the overdischarged state.

FIG. 21 shows a configuration of a personal digital assistant (PDA) to which an electronic device including a protection circuit according to the present invention is applied. The portable information terminal 4000 includes a plurality of operation buttons 4001, scroll buttons 4002, and a liquid crystal device 4003. The secondary battery 100 is used as a driving power source of the portable information terminal 4000, and the protection circuit according to the present invention is used to protect the secondary battery 100 from the overcharged state and the overdischarged state.
Electronic devices to which the protection circuit according to the present invention is applied include those shown in FIGS. 19 to 21, video cameras, digital cameras, car navigation devices, electronic notebooks, electronic papers, calculators, videophones, POSs. Terminal, etc.

DESCRIPTION OF SYMBOLS 10 ... Electronic device, 100 ... Secondary battery, 200, 205 ... Protection circuit, 210 ... Overcharge detection circuit, 220 ... Overdischarge detection circuit, 230 ... Charge state detection circuit, 240 ... Timing signal generation circuit, 250 ... Charge control Switch, 260 ... discharge control switch, 270 ... diode, 300 ... charging power source, 400 ... main body, 410 ... control circuit, 420 ... load, 2000 ... wristwatch, 3000 ... mobile phone, 4000 ... portable information terminal, Vx ... Terminal voltage, Vy: power supply voltage.

Claims (13)

A protection circuit used together with a secondary battery and a power source that generates power for charging, where the terminal voltage is equal to or lower than the upper limit voltage,
A first path for electrically connecting the secondary battery and the power source;
A second path for electrically connecting the secondary battery and the load;
A first switching element provided in the first path;
A charge state detection circuit for detecting a charge state indicating whether or not the secondary battery is charged from the power source;
An overcharge detection circuit that monitors the terminal voltage of the secondary battery and controls the first switching element to turn off the first switching element when it is detected that the terminal voltage exceeds the upper limit voltage. When,
When the terminal voltage of the secondary battery is within the range of the normal operation, the overcharge is detected when the detection result of the charge state is charged, compared with the case where the detection result of the charge state is not charged. A control circuit that controls to shorten the monitoring operation interval of the detection circuit ,
The detection operation interval at which the charge state detection circuit detects the charge state is longer than the monitoring operation interval of the overcharge detection circuit,
A protection circuit characterized by that . A protection circuit that is used together with a secondary battery and a power source that generates power for charging, where the terminal voltage is not less than the upper limit voltage and not more than the lower limit voltage,
A first path for electrically connecting the secondary battery and the power source;
A second path for electrically connecting the secondary battery and the load;
A first switching element provided in the first path;
A second switching element provided in the second path;
A charging current detection circuit for detecting the magnitude of the charging current supplied from the power source to the secondary battery;
A discharge current detection circuit for detecting the magnitude of the discharge current supplied from the secondary battery to the load;
An overcharge detection circuit that monitors the terminal voltage of the secondary battery and controls the first switching element to turn off the first switching element when it is detected that the terminal voltage exceeds the upper limit voltage. When,
An overdischarge detection circuit that monitors the terminal voltage of the secondary battery and controls the second switching element to turn off the second switching element when it is detected that the terminal voltage has fallen below the lower limit voltage. When,
When the terminal voltage of the secondary battery is within the range of the normal operation, the charge current is compared with the discharge current, and when the charge current is larger than the discharge current, the overcharge detection circuit is monitored. When the control is performed so that the interval is shorter than the monitoring operation interval of the overdischarge detection circuit and the charging current is smaller than the discharge current, the monitoring operation interval of the overdischarge detection circuit is the monitoring operation interval of the overcharge detection circuit. A control circuit that controls to be shorter than
Protection circuit with. A protection circuit that is used together with a secondary battery and a power source that generates power for charging, where the terminal voltage is not less than the upper limit voltage and not more than the lower limit voltage,
A first path for electrically connecting the secondary battery and the power source;
A second path for electrically connecting the secondary battery and the load;
A first switching element provided in the first path;
A second switching element provided in the second path;
A charge state detection circuit for detecting a charge state indicating whether or not the secondary battery is charged from the power source;
A discharge state detection circuit for detecting a discharge state indicating the presence or absence of discharge from the secondary battery to the load;
An overcharge detection circuit that monitors the terminal voltage of the secondary battery and controls the first switching element to turn off the first switching element when it is detected that the terminal voltage exceeds the upper limit voltage. When,
An overdischarge detection circuit that monitors the terminal voltage of the secondary battery and controls the second switching element to turn off the second switching element when it is detected that the terminal voltage has fallen below the lower limit voltage. When,
When the terminal voltage of the secondary battery is within the range of the normal operation, if the detection result of the charge state is not charged and the detection result of the discharge state is no discharge, the monitoring operation of the overcharge detection circuit is performed. A control circuit for stopping and executing a monitoring operation of the overdischarge detection circuit ;
Protection circuit with. A protection circuit that is used together with a secondary battery and a power source that generates power for charging, where the terminal voltage is not less than the upper limit voltage and not more than the lower limit voltage,
A first path for electrically connecting the secondary battery and the power source;
A second path for electrically connecting the secondary battery and the load;
A second switching element provided in the second path;
A charge state detection circuit for detecting a charge state indicating whether or not the secondary battery is charged from the power source;
An overdischarge detection circuit that monitors the terminal voltage of the secondary battery and controls the second switching element to turn off the second switching element when it is detected that the terminal voltage has fallen below the lower limit voltage. When,
When the terminal voltage of the secondary battery is within the range of the normal operation, when the charge state detection result is charged, the overdischarge is compared with the case where the charge state detection result is no charge. A control circuit that controls the detection circuit to increase the monitoring operation interval;
Protection circuit with. A protection circuit that is used together with a secondary battery and a power source that generates power for charging, where the terminal voltage is not less than the upper limit voltage and not more than the lower limit voltage,
A first path for electrically connecting the secondary battery and the power source;
A second path for electrically connecting the secondary battery and the load;
A first switching element provided in the first path;
A discharge state detection circuit for detecting a discharge state indicating the presence or absence of discharge from the secondary battery to the load;
An overcharge detection circuit that monitors the terminal voltage of the secondary battery and controls the first switching element to turn off the first switching element when it is detected that the terminal voltage exceeds the upper limit voltage. When,
When the terminal voltage of the secondary battery is within the range of the normal operation, the overcharge is detected when the discharge state detection result is discharged, compared to the discharge state detection result is no discharge. A control circuit that controls the detection circuit to increase the monitoring operation interval;
Protection circuit with. A power source that generates power for charging, and a protection circuit used together with a secondary battery whose terminal voltage is not lower than the lower limit voltage and lower than the upper limit voltage, which is a condition for normal operation,
A first path for electrically connecting the secondary battery and the power source;
A second path for electrically connecting the secondary battery and the load;
A first switching element provided in the first path;
A discharge state detection circuit for detecting a discharge state indicating the presence or absence of discharge for supplying power from the secondary battery to a load;
An overcharge detection circuit that monitors the terminal voltage of the secondary battery and controls the first switching element to turn off the first switching element when it is detected that the terminal voltage exceeds the upper limit voltage. When,
In the state where the terminal voltage of the secondary battery exceeds the upper limit voltage, when the detection result of the discharge state is discharge, the detection result of the overcharge detection circuit is compared with the case where the detection result of the discharge state is no discharge. A control circuit that controls to shorten the monitoring operation interval;
A protection circuit comprising. A power source that generates power for charging, and a protection circuit used together with a secondary battery whose terminal voltage is not lower than the lower limit voltage and lower than the upper limit voltage, which is a condition for normal operation,
A first path for electrically connecting the secondary battery and the power source;
A second path for electrically connecting the secondary battery and the load;
A second switching element provided in the second path;
A discharge current detection circuit for detecting the magnitude of the discharge current supplied from the secondary battery to the load;
An overdischarge detection circuit that monitors the terminal voltage of the secondary battery and controls the second switching element to turn off the second switching element when it is detected that the terminal voltage has fallen below the lower limit voltage. When,
In a state where the terminal voltage of the secondary battery exceeds the upper limit voltage, a control circuit that controls the monitoring operation interval of the overcharge detection circuit according to the magnitude of the discharge current;
A protection circuit comprising. A power source that generates power for charging, and a protection circuit used together with a secondary battery whose terminal voltage is not lower than the lower limit voltage and lower than the upper limit voltage, which is a condition for normal operation,
A first path for electrically connecting the secondary battery and the power source;
A second path for electrically connecting the secondary battery and the load;
A second switching element provided in the second path;
An overdischarge detection circuit that monitors the terminal voltage of the secondary battery and controls the second switching element to turn off the second switching element when it is detected that the terminal voltage has fallen below the lower limit voltage. When,
In a state where the terminal voltage of the secondary battery exceeds the upper limit voltage, a control circuit that controls to stop the monitoring operation of the overdischarge detection circuit;
A protection circuit comprising. A power source that generates power for charging, and a protection circuit used together with a secondary battery whose terminal voltage is not lower than the lower limit voltage and lower than the upper limit voltage, which is a condition for normal operation,
A first path for electrically connecting the secondary battery and the power source;
A second path for electrically connecting the secondary battery and the load;
A second switching element provided in the second path;
A charge state detection circuit for detecting a charge state indicating whether or not the secondary battery is charged from the power source;
An overdischarge detection circuit that monitors the terminal voltage of the secondary battery and controls the second switching element to turn off the second switching element when it is detected that the terminal voltage has fallen below the lower limit voltage. When,
In a state where the terminal voltage of the secondary battery is lower than the lower limit voltage, when the charge state detection result indicates that there is a charge, the overdischarge detection circuit is compared with a case where the charge state detection result is that there is no charge. A control circuit that controls to shorten the monitoring operation interval of
A protection circuit comprising. A power source that generates power for charging, and a protection circuit used together with a secondary battery whose terminal voltage is not lower than the lower limit voltage and lower than the upper limit voltage, which is a condition for normal operation,
A first path for electrically connecting the secondary battery and the power source;
A second path for electrically connecting the secondary battery and the load;
A second switching element provided in the second path;
A discharge current detection circuit for detecting the magnitude of the discharge current supplied from the secondary battery to the load;
An overdischarge detection circuit that monitors the terminal voltage of the secondary battery and controls the second switching element to turn off the second switching element when it is detected that the terminal voltage has fallen below the lower limit voltage. When,
In a state where the terminal voltage of the secondary battery is lower than the lower limit voltage, a control circuit that controls the monitoring operation interval of the overdischarge detection circuit according to the magnitude of the charging current;
A protection circuit comprising. A power source that generates power for charging, and a protection circuit used together with a secondary battery whose terminal voltage is not lower than the lower limit voltage and lower than the upper limit voltage, which is a condition for normal operation,
A first path for electrically connecting the secondary battery and the power source;
A second path for electrically connecting the secondary battery and the load;
A first switching element provided in the first path;
An overcharge detection circuit that monitors the terminal voltage of the secondary battery and controls the first switching element to turn off the first switching element when it is detected that the terminal voltage exceeds the upper limit voltage. When,
A control circuit that controls to stop the monitoring operation of the overcharge detection circuit in a state where the terminal voltage of the secondary battery is lower than the lower limit voltage;
Protection circuit provided. Detection operation interval of the charging state detection circuit detects the state of charge according to claim 3, 4, characterized in longer than monitoring operation interval of the over-charge detection circuit or the overdischarge detecting circuit, and among the 9 The protection circuit according to any one of the above. A power source that generates power for charging;
A secondary battery in which the terminal voltage is not less than the lower limit voltage and not more than the upper limit voltage is a condition for normal operation;
Load,
The protection circuit according to any one of claims 2 to 12 ,
An electronic device characterized by comprising:

Images