JP5708021B2 - Secondary battery protection circuit, device using secondary battery - Google Patents

Description

  The present invention relates to a circuit, an apparatus, and a method for controlling a secondary battery. For example, the present invention relates to a circuit, an apparatus, and a method for monitoring or protecting the state of a secondary battery.

  Conventionally, secondary batteries are used in various applications. The secondary battery market includes automobiles that use relatively large secondary batteries, agricultural / construction machinery, industrial machinery, mobile machinery such as automobiles, motorcycles, and trains, and energy. Examples include portable electronic devices such as notebook computers, portable telephones, electronic dictionaries, and electronic books that use small-sized secondary batteries, and watches with solar panels. However, in any field, it is necessary to control charging of the secondary battery, and to control discharging of the secondary battery. By appropriately performing these controls, the secondary battery can be used efficiently. For example, in Patent Document 1, an overcurrent is reliably detected without causing an excessive current to flow through the discharge control switch element and without changing the reference voltage for overcurrent detection set in the IC. It is described that a protection circuit device for a secondary battery capable of performing overcurrent protection is provided.

Japanese Patent Laid-Open No. 11-127543

  However, the protection circuit for the secondary battery always operates upon receiving power supply from the secondary battery, and this is one of the factors for shortening the time for power supply from the secondary battery.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following application examples or embodiments.

[Application Example 1]
The secondary battery protection circuit according to this application example includes a charging power supply monitoring circuit that monitors a power supply state of a charging power supply of a secondary battery, an overdischarge detection circuit that detects an overdischarge state of the secondary battery, and a control unit And when the charging power supply monitoring circuit determines that the power supply state is insufficient for charging the secondary battery, the control unit detects the overdischarge detection circuit. The operation is stopped.

  According to this configuration, when the charging power supply monitoring circuit monitors the power supply state of the charging power supply, and it is determined that the power supply state is insufficient for charging the secondary battery, the control is performed. When the unit stops the operation of the overdischarge detection circuit, it is possible to suppress the consumption of the secondary battery when the secondary battery cannot be charged.

[Application Example 2]
In the secondary battery protection circuit according to the application example, it is preferable that the overdischarge detection circuit is stopped when a voltage state of the secondary battery is an overdischarge state.

  According to this configuration, by stopping the operation of the overdischarge detection circuit when the secondary battery is in the overdischarge state, it is possible to monitor the state of the secondary battery when the secondary battery is not in the overdischarge state. It is possible to suppress the consumption of the secondary battery when the secondary battery is in an overdischarged state. Thereby, it is possible to provide a time allowance until the secondary battery is charged, and it is possible to reduce the influence on the life of the secondary battery due to the progress of the discharge.

[Application Example 3]
In the secondary battery protection circuit according to the application example described above, it is preferable that the charging power supply monitoring circuit operates when a voltage state of the secondary battery is an overdischarged state.

  According to this configuration, the power supply state can be confirmed in the overdischarged state by operating the charging power supply monitoring circuit in the overdischarged state. Thereby, the operation of the overdischarge detection circuit can be stopped when the secondary battery is in an overdischarged state and the power supply state is insufficient to charge the secondary battery.

[Application Example 4]
In the secondary battery protection circuit according to the application example described above, it is preferable that monitoring of the power supply state in the charging power supply monitoring circuit is performed by at least one of voltage and current.

  According to this configuration, the power supply state is monitored by using at least one of voltage and current, so that the degree of freedom in designing the charging power supply monitoring circuit can be increased. In order to charge the secondary battery, a voltage higher than a predetermined voltage is required. For this reason, the power supply monitoring may be performed by detecting whether the charging voltage is sufficient. However, when it is clear that the charging voltage necessary for charging the secondary battery can be maintained by the flow of the predetermined current, it is not detected by the charging voltage but is detected whether the predetermined current is flowing. You may judge by.

[Application Example 5]
An apparatus using a secondary battery according to this application example includes the secondary battery protection circuit described above.

  According to this configuration, the apparatus using the secondary battery has the above-described secondary battery protection circuit, so that it is possible to configure an apparatus that reduces power used for protecting the secondary battery.

[Application Example 6]
The secondary battery protection method according to this application example includes a first step of detecting a power supply state in a charging power source of the secondary battery, and the power supply state that is necessary for charging the secondary battery. A second step of determining whether or not the secondary battery is insufficient, and if the power supply state is determined to be insufficient for charging the secondary battery, the secondary battery is overloaded. And a third step of stopping the operation of the overdischarge detection circuit for detecting the discharge state.

  According to this method, the first step of detecting the power supply state in the charging power source of the secondary battery and the power supply state determine whether or not the power necessary for charging the secondary battery is insufficient. When the secondary battery cannot be charged by including the second step and the third step of stopping the operation of the overdischarge detection circuit when it is determined that the power necessary for charging is insufficient. It is possible to suppress the consumption of the secondary battery.

[Application Example 7]
In the method for protecting a secondary battery according to the application example described above, it is preferable that the overdischarge detection circuit is stopped in an overdischarge state.

  According to this method, by stopping the operation of the overdischarge detection circuit when the secondary battery is in the overdischarge state, it is possible to monitor the state of the secondary battery when the secondary battery is not in the overdischarge state. It is possible to suppress the consumption of the secondary battery when the secondary battery is in an overdischarged state. Thereby, it is possible to provide a time allowance until the secondary battery is charged, and it is possible to reduce the influence on the life of the secondary battery due to the progress of the discharge.

[Application Example 8]
In the secondary battery protection method according to the application example, it is preferable that the first step is performed when a voltage state of the secondary battery is in an overdischarge state.

  According to this method, the first step is performed when the voltage state of the secondary battery is in the overdischarge state, so that the confirmation of the power supply state can be performed in the overdischarge state. Thereby, the operation of the overdischarge detection circuit can be stopped when the secondary battery is in an overdischarged state and the power supply state is insufficient to charge the secondary battery.

[Application Example 9]
In the secondary battery protection method according to the application example described above, it is preferable that the power supply state monitoring in the second step is performed by at least one of a voltage and a current.

  According to this method, the power supply state is monitored using at least one of voltage and current, so that the degree of freedom in designing the charging power supply monitoring circuit can be increased. In order to charge the secondary battery, a voltage higher than a predetermined voltage is required. For this reason, the power supply monitoring may be performed by detecting whether the charging voltage is sufficient. However, when it is clear that the charging voltage necessary for charging the secondary battery can be maintained by the flow of the predetermined current, it is not detected by the charging voltage but is detected whether the predetermined current is flowing. You may judge by.

The schematic block diagram of the apparatus which has the charge power supply monitoring circuit in 1st Embodiment. The schematic block diagram of a charging power supply monitoring circuit. Circuit of voltage detector. 3 is a schematic flowchart of processing in an operation control circuit. The schematic flowchart of the process in an overdischarge detection circuit. The schematic flowchart of the process in an overdischarge detection circuit. The schematic flowchart of the process in an overdischarge detection circuit. The schematic block diagram of the apparatus which has the charging power supply monitoring circuit in 2nd Embodiment. The schematic block diagram of the apparatus which has the charging power supply monitoring circuit in 3rd Embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the words “on” and “off” may be used to describe the state of a signal or the like. For example, “ON” and “OFF” indicate that “A signal is ON” indicates that the meaning of the A signal is valid, and “A signal is OFF” indicates that the meaning of the A signal is invalid. It shall be shown that In addition, when using for description of operation | movement of a transistor etc., on and off are used in the meaning generally used.

(First embodiment)
FIG. 1 shows a schematic block diagram of an apparatus 100 to which the present invention is applied. The device 100 includes a discharge control circuit 110, a charge control circuit 120, a protection circuit 130, a secondary battery 140, and a solar battery 150. Although not shown, the device 100 has a function unit for executing a function as the device 100.

  The power supply line 11 is used for taking out power from the secondary battery 140 and supplying charging power to the secondary battery 140. The power supply line 11 is connected to the discharge control circuit 110, and power is supplied to the above-described functional unit via the discharge control circuit 110. The discharge control circuit 110 recognizes that the secondary battery 140 is in an overdischarge state via the overdischarge control signal 12, and can perform an operation suitable for the overdischarge state. Further, the power line 11 is connected to the charge control circuit 120, and charging power is supplied from the solar cell 150 to the secondary battery 140 via the charge control circuit 120. The charge control circuit 120 is controlled by the operation control circuit 133 via the charge control signal 13. The power line 11 is also connected to the protection circuit 130 for checking the state of the secondary battery 140. Although not all are shown, the power supply line 11 also supplies power for the operation of the protection circuit 130.

  The protection circuit 130 includes an overdischarge detection circuit 131, a charging power supply monitoring circuit 132, and an operation control circuit 133. The power supply line 11 is connected to the overdischarge detection circuit 131 and the charging power supply monitoring circuit 132. The overdischarge detection circuit 131 is a circuit for confirming the voltage level of the power supply line 11. When it is detected that the voltage of the power supply line 11 has become a predetermined voltage or less, the operation control circuit 133 is connected via the overdischarge state signal 16. Notify

  The charging power supply monitoring circuit 132 is a circuit for monitoring the power of the charging line 14 supplied from the solar battery 150. When it is determined that the power of the charging line 14 is not sufficient to charge the secondary battery 140, the low power determination signal 15 is turned on. The second control signal 19 is a signal for the operation control circuit 133 to control the charging power supply monitoring circuit 132.

  The operation control circuit 133 is a part that analyzes information sent from the overdischarge detection circuit 131 and the charging power supply monitoring circuit 132 and controls the charge control circuit 120 and the overdischarge detection circuit 131. Information sent from the overdischarge detection circuit 131 is an overdischarge state signal 16. The operation control circuit 133 grasps the power state of the charging line 14 from the solar cell 150 based on the low power determination signal 15 and performs appropriate control on the overdischarge detection circuit 131. This control is performed by the first control signal 17 output from the operation control circuit 133 to the overdischarge detection circuit 131.

  Since the voltage state of the power supply line 11 and the voltage state of the secondary battery 140 have a high correlation, the protection circuit 130 recognizes the voltage state of the power supply line 11 from the overdischarge state signal 16 to thereby detect the secondary battery 140. It can be determined whether or not is in an overdischarged state. Therefore, when the overdischarge state signal 16 is on, it is determined that the secondary battery 140 is in the overdischarge state. When the overdischarge state signal 16 is off, it is determined that the voltage state of the secondary battery 140 is not in the overdischarge state.

  When the operation control circuit 133 determines that the power state of the charging line 14 is not sufficient to charge the secondary battery 140, the operation control circuit 133 stops the operation of the overdischarge detection circuit 131 via the first control signal 17. Instruct. This is intended to reduce the power consumption of the device 100 in a state where the secondary battery 140 is not charged by stopping part of the operation of the protection circuit 130. When the operation control circuit 133 determines that the power state of the charging line 14 is not sufficient to charge the secondary battery 140, the operation control circuit 133 stops the operation of the charging control circuit 120 via the charging control signal 13. Instruct.

  FIG. 2 shows a schematic block diagram of the charging power supply monitoring circuit 132. The charging power supply monitoring circuit 132 includes a power detection unit 134 and a level shift unit 135. The power detection unit 134 operates by the charging line 14, and the voltage state of the charging line 14 is transmitted to the level shift unit 135 as two signals of the first state signal 21 and the second state signal 22. The level shift unit 135 has a voltage level suitable for the operation control circuit 133 because the voltage level at which the charging power supply monitoring circuit 132 operates at the voltage level of the charging line 14 varies. 15 is a circuit having a function for driving 15, and is operated by power supplied from the power supply line 11. The level shift unit 135 determines the voltage state of the charging line 14 from the first state signal 21 and the second state signal 22 and turns on the low power determination signal 15.

  FIG. 3 shows an example of the circuit of the power detection unit 134. The resistors R <b> 1 to R <b> 4 may be determined according to the characteristics of the solar cell 150 and the characteristics of the transistors in the power detection unit 134. The resistors R1 to R3 are set so that the transistor Tr2 is turned off when the voltage state of the charging line 14 drops to a voltage that is not sufficient for charging. When the voltage state of the charging line 14 is sufficient to charge, the transistors Tr2, Tr4 and Tr5 are on and the transistors Tr1, Tr3 and Tr6 are off. Accordingly, when the voltage state of the charging line 14 is sufficient for charging, the first state signal 21 is at a high level and the second state signal 22 is at a low level.

  When the potential of the charging line 14 is lowered due to, for example, the solar battery 150 being turned on, the potential difference necessary for turning on the source terminal and the gate terminal cannot be maintained in all the transistors Tr1 to Tr6. Although all the transistors Tr1 to Tr6 are turned off, the potential levels of the first state signal 21 and the second state signal 22 are higher than the potential level of the charging line 14 due to the presence of parasitic diodes in Tr3 and Tr4. In other words, both the first state signal 21 and the second state signal 22 are at a level recognized by the level shift unit 135 as a low level. When the level shift unit 135 recognizes that both the first state signal 21 and the second state signal 22 are at the low level, the level shift unit 135 turns on the low power determination signal 15.

  The operation control circuit 133 recognizes that the voltage of the charging line 14 is insufficient for charging when the low power determination signal 15 is turned on, and instructs the overdischarge detection circuit 131 to stop the operation. It is transmitted via a control signal 17.

  In the present embodiment, the overdischarge detection circuit 131 immediately stops its operation in response to an instruction to stop the operation via the first control signal 17. When the charging power supply monitoring circuit 132 determines that the voltage of the charging line 14 is insufficient to charge the secondary battery 140, the operation control circuit 133 stops the operation of the overdischarge detection circuit 131. Since the operation of the overdischarge detection circuit 131 is stopped, it is possible to take a longer time to operate the apparatus 100 with the electric power held by the secondary battery 140.

  In this embodiment, the overdischarge detection circuit 131 stops when the voltage state of the power supply line 11 becomes an overdischarge state after an instruction to stop the operation via the first control signal 17. Accordingly, it is possible to reduce the voltage drop of the secondary battery 140 when the voltage state of the secondary battery 140 becomes an overdischarged state, and an effect of extending the life of the secondary battery 140 is expected. In addition, when it is determined that the voltage state of the secondary battery 140 is an overdischarged state, information necessary for restarting the operation can be stored in the apparatus 100, and the voltage state of the secondary battery 140 is normally changed from the overdischarged state. The processing in the apparatus 100 can be resumed when the state becomes. However, since the overdischarge detection circuit 131 operates until the secondary battery 140 is determined to be in the overdischarge state, the time until the voltage state of the secondary battery 140 becomes the overdischarge state is compared with that in the first embodiment. Shorter.

  The operation of the protection circuit 130 in this embodiment will be described using a flowchart. 4 to 7 show schematic flowcharts of processing in this embodiment. Note that the schematic flowcharts shown in FIGS. 4 to 7 describe only the parts necessary for the description of the present embodiment, and only show a part of the processing performed in the protection circuit 130.

  The operation control circuit 133 monitors the voltage state of the charging line 14, and operates the overdischarge detection circuit 131 when there is sufficient voltage to charge the secondary battery 140, causing the secondary battery 140 to On the other hand, when there is not enough voltage for charging, the overdischarge detection circuit 131 is stopped. The flowchart in FIG. 4 shows a part of the processing in the operation control circuit 133. FIG. 4- (1) shows a main routine, and FIG. 4- (2) shows a subroutine of the main routine shown in FIG. 4- (1).

  First, FIG. 4- (1) will be described. After the start-up, initial settings such as setting of flags necessary for the operation of the protection circuit 130 and the operation mode of each unit are performed (S01). As an example of setting the operation mode of each part, for example, an instruction to start the operation to the overdischarge detection circuit 131 is given. Thereafter, the operation control circuit 133 proceeds to a charging voltage monitoring process (S02) in which the value of the low power determination signal 15 output from the charging power supply monitoring circuit 132 is monitored to determine whether the charging voltage is sufficient. If it is determined in S02 that the charging voltage is not sufficient, the process proceeds to the overdischarge detection post-processing (S03). When the overdischarge detection post-process (S03) ends, the process returns to the charge voltage monitoring process (S02).

  Next, the overdischarge detection post-process (S03) will be described. FIG. 4- (2) is a flowchart of the overdischarge detection post-process (S03). First, the overdischarge detection circuit 131 is instructed to stop the operation (S11). Thereafter, the voltage state of the charging line 14 is monitored to determine whether the charging voltage is sufficient (S12). If it is determined that the charging voltage is sufficient, the overdischarge detection circuit 131 is instructed to start operation (S13). Thereafter, the process returns to the main routine (S14).

  The flowchart of FIG. 5 shows a main routine of processing in the overdischarge detection circuit 131. The flowcharts of FIGS. 6 and 7 are subroutines of the main routine shown in FIG.

  After startup, the overdischarge detection circuit 131 monitors a command from the operation control circuit 133 (S21). As described above, in the initial setting (S01) process, the operation control circuit 133 is instructed to start an operation, and this instruction is transmitted by a command. In the initial setting (S01) shown in FIG. 4, a command indicating the start of overdischarge detection is transmitted. When a command is sent, the overdischarge detection circuit 131 first determines whether the sent command is a command for instructing start of detection (S22). If the command instructs the start of detection, the process proceeds to the first detection process (S23). The first detection process (S23) is a process in which the overdischarge detection circuit 131 monitors the overdischarge of the power supply line 11 when an instruction to stop the overdischarge detection circuit 131 is not issued. If the received command is not an instruction to start detection, it is determined whether the command is an instruction to stop detection (S25). If the command is an instruction to stop detection, the process proceeds to the second detection process (S26). The second detection process (S26) is a process for stopping monitoring of overdischarge of the power supply line 11. If it is determined in the process of S25 that the command does not instruct detection stop, this is a case in which the command does not instruct detection start and does not instruct detection stop. In this case, the received command is determined to be erroneous reception due to noise or the like, and the process returns to the command monitoring process (S21).

  As will be described later, commands from the operation control circuit 133 are also monitored in the first detection process (S23) and the second detection process (S26). If a command to start detection of overdischarge of the power supply line 11 is received during the execution of the first detection process (S23), since the overdischarge state has already been monitored, the first detection process (S23) There is no need to return from the process to the main routine. However, if a command other than the start of overdischarge detection is received during the execution of the first detection process (S23), it is necessary to return to the main flow from the first detection process (S23) and determine the command. When the process returns from the first detection process (S23), it is determined whether the command received during the process of the first detection process (S23) is an overdischarge detection stop command (S24). If the command instructs to stop detection of overdischarge, the process proceeds to the second detection process (S26). If the command does not instruct to stop overdischarge detection, it is determined that the command is erroneously received due to noise or the like, and the process returns to the first detection process (S23).

  If a command to stop detection of overdischarge of the power supply line 11 is received during execution of the second detection process (S26), the second detection process (S26) is already in the process of stopping detection of overdischarge. There is no need to return to the main routine from this process. However, if a command other than the overdischarge detection stop is received during the execution of the second detection process (S26), it is necessary to return to the main flow from the second detection process (S26) and determine the command. When the process returns from the second detection process (S26), it is determined whether or not the command received during the process of the second detection process (S26) is an overdischarge detection start command (S27). If the command instructs the start of overdischarge detection, the process proceeds to the first detection process (S23). If the command does not instruct the start of overdischarge detection, it is determined that the command is erroneously received due to noise or the like, and the process returns to the second detection process (S26).

  FIG. 6 is a flowchart of the first detection process (S23). First, detection of an overdischarge state in the power line 11 is started (S31). The overdischarge state is monitored (S32), and when the overdischarge state is detected, the operation control circuit 133 is notified via the overdischarge state signal 16 that the overdischarge state is detected (S33).

  The first detection process (S23) is performed when the charging voltage of the charging line 14 is maintained at a level sufficient to charge the secondary battery 140 (the overdischarge detection circuit 131 is not instructed to stop the operation). When not). When the secondary battery 140 is in an overdischarged state, the discharge control circuit 110 that recognizes the overdischarge by the overdischarge control signal 12 performs an appropriate operation, so that the power supplied to the functional unit in the device 100 can be suppressed. Thus, the voltage state of the secondary battery 140 will eventually return to the normal state. It is determined whether or not the voltage state of the secondary battery 140 has returned to the normal state by detecting whether the power line 11 is overdischarged (S34). If it is determined that the secondary battery 140 has returned to the normal state, overdischarge detection is performed. The circuit 131 notifies the operation control circuit 133 that the voltage state of the secondary battery 140 is in the normal state (S35). Thereafter, the process proceeds to a command monitoring process (S36).

  If it is detected in the overdischarge state monitoring process (S32) of the power line 11 that the overdischarge state is not detected, the process proceeds to a command monitoring process (S36). If no command is detected in the command monitoring process (S36), the process proceeds to an overdischarge monitoring process (S32). If no overdischarge is detected and no command is detected, the processes of (S32) and (S36) are repeated.

  When a command is detected in the command monitoring process (S36), it is determined whether or not the command is an overdischarge detection start command (S37). In the case of a command for instructing the start of overdischarge detection, since detection has already started, the process proceeds to overdischarge monitoring processing (S32). If it is not a command for instructing the start of overdischarge detection, processing other than the first detection processing (S23) is necessary, and the routine returns to the main routine (S38).

  FIG. 7 is a flowchart of the second detection process (S26). As described above, the second detection process (S26) is a process performed when a command instructing to stop detecting overdischarge is received. Further, as described above, the first embodiment stops the operation of the overdischarge detection circuit 131 immediately upon receiving an instruction to stop the overdischarge detection. However, in this embodiment, the secondary battery 140 is in an overdischarge state. This is an example in which the operation of the overdischarge detection circuit 131 is stopped after it is determined that this has occurred, and this process is performed in the second detection process (S26).

  First, detection of overdischarge is started (S41). Assuming a normal management flow of the secondary battery 140, it is considered that the process of S41 is instructed by the operation control circuit 133 before the second detection process (S26) is performed. There is no problem. Next, overdischarge monitoring processing (S42) is performed. When an overdischarge state is detected, the operation control circuit 133 is notified of the overdischarge state (S43), and then the operation of the overdischarge detection circuit 131 is stopped. (S44). Although a detailed flow is not particularly shown for the detection circuit operation stop process (S44), overdischarge detection other than the part that recognizes the detection operation restart signal (may be a reset signal) from the operation control circuit 133 The operation in the circuit 131 is stopped.

  If no overdischarge is detected in the overdischarge monitoring process (S42), a command monitoring process (S45) is performed. If a command is not detected, overdischarge monitoring processing (S42) is performed. That is, when no overdischarge is detected and no command is detected, the processes of (S42) and (S45) are repeated.

  If a command is detected in the command monitoring process (S45), it is first determined whether or not it is an instruction to stop detection of overdischarge (S46). In the case of an instruction to stop overdischarge detection, since the process has already been started, the process returns to the overdischarge monitoring process (S42). If the command is not an instruction to stop detection of overdischarge, processing other than the second detection processing (S26) is necessary, and the routine returns to the main routine (S47).

  Note that what is described as a command in the flowchart is not particularly defined as long as it is transmitted via the first control signal 17. For example, a data signal may be defined in the first control signal 17, and a command may be defined as one of data sent from the operation control circuit 133, or a signal indicating a command may be defined in the first control signal 17. Good. When the command is defined in association with the signal line, the flow from S25 to S21, the flow from S24 to S23, and the flow from S27 to S26 in FIG. 5 include a detection start instruction signal and a detection stop instruction signal. This can be handled as a process when they are simultaneously turned on.

  Although the flowcharts of FIGS. 5 to 7 are used to explain the processing of the overdischarge detection circuit 131, the implementation of these processes in the overdischarge detection circuit 131 may be performed by a program using a microcomputer. All may be configured by hardware.

  In this embodiment, the charging power supply monitoring circuit 132 operates when the secondary battery 140 is in an overdischarged state. When the secondary battery 140 is not in an overdischarged state, the operation control circuit 133 stops operating.

  When the overdischarge detection circuit 131 detects that the secondary battery 140 has shifted to the overdischarge state, the overdischarge detection circuit 131 controls the operation of the secondary battery 140 in the overdischarge state via the overdischarge state signal 16. The circuit 133 is notified. When the operation control circuit 133 recognizes that the secondary battery 140 is in an overdischarged state, the operation control circuit 133 gives an instruction via the second control signal 19 to start the operation of the charging power supply monitoring circuit 132.

  The charging power supply monitoring circuit 132 that has started the operation monitors the charging line 14 and turns on the low power determination signal 15 when it is determined that the charging power is insufficient to charge the secondary battery 140. When the operation control circuit 133 recognizes that the low power determination signal 15 is turned on, the operation control circuit 133 gives an instruction via the first control signal 17 to stop the operation of the overdischarge detection circuit 131.

  Although the present embodiment has been described above, by applying the present invention, power consumption in the protection circuit 130 can be reduced, and the life of the secondary battery 140 can be extended.

  The second embodiment and the third embodiment will be described below. In the following description of the embodiments, the same reference numerals are given to portions having the same configuration and the same functions as those of the above-described embodiments, and the description thereof is omitted.

(Second Embodiment)
The present embodiment is an example of a device 200 in which a solar battery 150 is removed from the device 100 and a charging power supply source 151 that is a charging power source is provided outside. A schematic block diagram is shown in FIG. The charging power supply source 151 may be an AC adapter or a USB power source.

  When charging power from the charging power supply source 151 is monitored by the charging power supply monitoring circuit 132 and it is determined that charging for the secondary battery 140 is insufficient, the overdischarge detection circuit 131 of the protection circuit 130 Control to stop the operation is performed. Thereby, the power consumed by the protection circuit 130 can be reduced.

  The present embodiment is an example in the case where the device 200 has a function of recognizing the connection state of the charging power supply source 151. The function may be, for example, by providing a switch at a connection portion of the charging power supply source 151 so that the charging power supply monitoring circuit 132 can recognize the on / off state of the switch. When the charging power supply monitoring circuit 132 recognizes that the charging power supply source 151 is not connected to the apparatus 200, the charging power supply monitoring circuit 132 turns on the low power determination signal 15. In response to this, the operation control circuit 133 stops the operation of the overdischarge detection circuit 131.

  In addition, Example 4 and Example 5 may be performed when the secondary battery 140 is in an overdischarged state.

(Third embodiment)
The present embodiment is an example of a device 300 in which a sampling circuit 136 is added to the device 100 described in the first embodiment. A schematic block diagram of the apparatus 300 is shown in FIG. The sampling circuit 136 turns on the sampling signal 18 at predetermined time intervals. The operation control circuit 133 generates a timing signal based on the sampling signal 18 and outputs the generated timing signal to the charging power supply monitoring circuit 132 via the second control signal 19. The charging power supply monitoring circuit 132 samples the voltage state of the charging line 14 when the timing signal sent via the second control signal 19 is turned on. The timing signal may be, for example, a signal that is turned on for a predetermined period at predetermined time intervals. The predetermined period may be a period longer than the length of time during which the charging power supply monitoring circuit 132 samples the charging line 14 and the sampled result can be reflected in the low power determination signal 15. The operation control circuit 133 can know whether or not the charging line 14 has power necessary for charging the secondary battery 140 by capturing the value of the low power determination signal 15 at the timing when the timing signal is turned off. Since the detection of the state of the charging line 14 is performed at a predetermined time interval, the power consumption of the protection circuit 130 can be reduced.

  The operation in the present embodiment may be performed when the secondary battery 140 is in an overdischarged state.

  Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and can be widely applied without departing from the gist of the present invention.

  DESCRIPTION OF SYMBOLS 11 ... Power line, 12 ... Overdischarge control signal, 13 ... Charge control signal, 14 ... Charge line, 15 ... Low power determination signal, 16 ... Overdischarge state signal, 17 ... First control signal, 18 ... Sampling signal, 19 2nd control signal, 21 ... 1st state signal, 22 ... 2nd state signal, 100 ... device, 110 ... discharge control circuit, 120 ... charge control circuit, 130 ... protection circuit, 131 ... overdischarge detection circuit, 132 ... Charging power supply monitoring circuit, 133 ... operation control circuit, 134 ... power detection unit, 135 ... level shift unit, 136 ... sampling circuit, 140 ... secondary battery, 150 ... solar battery, 151 ... charging power supply source, 200 ... device, 300 ... Device.

Claims (5)

A charging power supply monitoring circuit for monitoring the power supply state of the charging power supply of the secondary battery;
An overdischarge detection circuit for detecting an overdischarge state of the secondary battery;
A control unit,
The charging power supply monitoring circuit includes a power detection unit and a level shift unit,
The power detection unit is connected to a charging power source of the secondary battery,
The level shift unit is connected to the output of the secondary battery,
The controller stops the operation of the overdischarge detection circuit when the charging power supply monitoring circuit determines that the power supply state is insufficient for charging the secondary battery. A secondary battery protection circuit. The overdischarge detection circuit is a case where the charging power supply monitoring circuit determines that the power supply state is insufficient for charging the secondary battery, and the voltage of the secondary battery is The secondary battery protection circuit according to claim 1, wherein the secondary battery protection circuit is stopped when the state is an overdischarged state. The secondary battery protection circuit according to claim 1, wherein the charging power supply monitoring circuit operates at least when the voltage state of the secondary battery is an overdischarged state. 4. The secondary battery protection circuit according to claim 1, wherein monitoring of the power supply state in the charging power supply monitoring circuit is performed by at least one of voltage and current. 5. The apparatus using the secondary battery characterized by including the secondary battery protection circuit as described in any one of Claims 1 thru | or 4.

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