JP2008005626A - Battery pack and electronic equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide electronic equipment in a simple configuration that prevents continuous charge in a state close to the full charge of a secondary cell, and can stabilize cell performance. <P>SOLUTION: The electronic equipment has: a battery pack incorporating a temperature sensor for detecting the temperature of the secondary cell, and a protection circuit for prohibiting the charge and discharge of the secondary cell; and a discharge control circuit to which the battery pack and a load are connected. In the electronic equipment, a drive circuit for operating the protection circuit forcedly is incorporated into the battery pack when a prescribed control voltage is applied via the external connection terminal of the temperature sensor, and a charge current detection circuit is provided. The charge current detection circuit detects current supplied to the battery pack from the charge control circuit, and applies the prescribed control voltage to the external connection terminal of a temperature sensor in the battery pack when the supplied current does not meet a prescribed current threshold. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a battery pack including a secondary battery, the battery pack and a charge control circuit thereof, and an electronic device including a load connected to the charge control circuit in parallel with the battery pack.

  Electronic devices such as mobile phones usually have a built-in secondary battery and are detachably provided on the device body, a charging control circuit for the secondary battery incorporated in the device body, and the device body And a load (load circuit) that is operated by being supplied with electric power through the charge control circuit. The load is generally connected in parallel with the battery pack to the power output terminal of the charge control circuit. When power is supplied from an external charging adapter or the like via a charge control circuit, the load is driven by the output power of the charge control circuit, and when power supply from the outside is interrupted, the load is The battery pack is driven by the electric energy stored in the secondary battery.

  FIG. 3 shows a schematic configuration of such an electronic apparatus, wherein 10 is a battery pack, 20 is a charge control circuit, 30 is a load (load circuit), and 40 is a charge adapter as an external power source. Incidentally, the battery pack 10 includes a secondary battery 13 connected to a pair of charge / discharge terminals 11, 12, a charge prohibition switch 14 and a discharge prohibition switch 15 inserted in series in a charge / discharge path of the secondary battery 13. A protection circuit detects the terminal voltage Vbat of the secondary battery 13 and shuts off the charge prohibition switch 14 to prevent overcharge of the secondary battery 13 and shuts off the discharge prohibition switch 15 (off). And a temperature sensor 17 such as a thermistor for detecting the temperature of the secondary battery 13 and its external connection terminal 18.

  The charge control circuit 20 includes power output terminals 21 and 22 to which the charge / discharge terminals 11 and 12 of the battery pack 10 are connected, and a sensor input terminal to which the external connection terminal 18 of the temperature sensor 17 in the battery pack 10 is connected. 23. The charge control circuit 20 is mainly composed of a microprocessor (control IC) 24, and is detected by the temperature sensor 17 when the output current I detected via the shunt resistor 25 is less than a predetermined current threshold Ith. When the temperature Tbat of the secondary battery 13 obtained via the sensor input terminal 23 exceeds a predetermined temperature threshold value Tlimt, the charging control switch 26 provided at the output stage thereof is cut off (turned off). It has a function of prohibiting power output from the control circuit 20.

  The charge control circuit 20 basically turns on and off the charge control switch 26 at high speed when charging of the secondary battery 13 is started, and pulse-charges or continuously charges the secondary battery 13 with a constant current. When the secondary battery 13 is charged to a predetermined voltage or higher, a constant voltage is output via the charge control switch 26 to charge the secondary battery 13 at a constant voltage. When the secondary battery 13 reaches a fully charged state and the charging current I during constant voltage charging falls below the predetermined current threshold Ith, this is detected and the charging control switch 26 is shut off (turned off). The charging of the secondary battery 13 is stopped.

The method of charging the secondary battery 13 with constant current and then charging with constant voltage is well known as, for example, a charge control method for a lithium ion battery (see, for example, Patent Document 1). Various battery packs 10 including the above-described protection circuit have been proposed in the past (see, for example, Patent Document 2).
JP 2005-158285 A JP-A-9-329651

  By the way, the shunt resistor 25 in the charging control circuit 20 of the electronic device configured as described above is configured to calculate the sum of the currents supplied to the battery pack 10 (secondary battery 13) and the load 30 via the power output terminals 21 and 22. Detected. Therefore, when the power consumption at the load 30 is large, even if the secondary battery 13 reaches a fully charged state, the output current I from the charge control circuit 20 does not fall below the above-described current threshold Ith. There is a risk that things will happen. Then, since the charge control switch 26 remains conductive (on), the secondary battery 13 in the battery pack 10 is always in a fully charged state unless the protection circuit (charge prohibition switch 14) operates. Charging can be continued or repeated. Such a state becomes a factor that deteriorates the battery performance of the secondary battery 13, and is not preferable.

  The present invention has been made in view of such circumstances, and its purpose is to prevent continuous charging in a state close to full charge of the secondary battery while utilizing the function of the charge control circuit as it is. It is an object of the present invention to provide a battery pack and an electronic device having a simple configuration capable of stabilizing performance.

The battery pack according to the present invention includes a secondary battery, a temperature sensor that detects the temperature of the secondary battery and outputs detected temperature information via an external connection terminal, and the secondary battery and its charge / discharge terminal. A protection circuit that is provided in between and prohibits charging and discharging of the secondary battery,
In particular, a drive circuit for forcibly operating the protection circuit when a predetermined control voltage is applied via an external connection terminal of the temperature sensor is provided.

The electronic device according to the present invention is
<a> a secondary battery, a temperature sensor that detects the temperature of the secondary battery, and a battery pack that includes a protection circuit that prohibits charging and discharging of the secondary battery;
<b> A power output terminal to which a charge / discharge terminal of the battery pack is connected and a sensor input terminal to which an external connection terminal of the temperature sensor in the battery pack is connected, and an output current through the power output terminal When the temperature of the secondary battery detected by the temperature sensor and obtained through the sensor input terminal exceeds a predetermined temperature threshold, the power output through the power output terminal A charge control circuit having a charge control switch for inhibiting
<c> A load connected in parallel with the battery pack to the power output terminal of the charge control circuit [Precondition]
In particular
<d> A drive circuit for forcibly operating the protection circuit when a predetermined control voltage is applied to the battery pack via the external connection terminal of the temperature sensor,
<e> A current supplied to the battery pack from the power output terminal of the charge control circuit is detected, and a predetermined control voltage is applied to the external connection terminal of the temperature sensor when the supplied current is less than a predetermined current threshold. The charging current detection circuit which adds is provided.

  Preferably, the drive circuit includes a switch element that forcibly activates a charge prohibition switch in the protection circuit. The charging current detection circuit is realized as an external circuit provided between a power output terminal of the charging control circuit and a charging / discharging terminal of the battery pack, or as a built-in circuit incorporated in the battery pack. .

  According to the battery pack having the above-described configuration, when a predetermined control voltage is applied via the external connection terminal of the temperature sensor, the drive circuit that forcibly activates the protection circuit that prohibits charging and discharging of the secondary battery. Since it is equipped, charging / discharging of a secondary battery can be forcibly prohibited according to the use condition etc. of a secondary battery. Specifically, the secondary battery is fully charged and is detected independently of its charge control circuit to prohibit charging, or the secondary battery is discharged. It is possible to detect the discharge independently of the circuit and prohibit its discharge. That is, charging and discharging can be easily prohibited by external control using the external connection terminal of the temperature sensor.

  In addition, according to the electronic apparatus having the above-described configuration, a charging current detection circuit that detects a current supplied from the power output terminal of the charging control circuit to the battery pack is provided independently of the current detection function of the charging control circuit. Therefore, even when the power consumption at the load is large, the charging current for the secondary battery can be reliably detected. In addition, the battery pack incorporates a drive circuit that forcibly activates the protection circuit when a predetermined control voltage is applied via an external connection terminal of the temperature sensor. When a current that is less than the current threshold is detected, a predetermined control voltage is applied to the external connection terminal of the temperature sensor, so that when the secondary battery reaches a fully charged state and its charging current decreases, no more charging occurs. Can be definitely prohibited. As a result, overcharge of the secondary battery built in the battery pack can be easily and reliably prevented regardless of the power consumption of the load.

  In particular, use of the external connection terminal of the temperature detection element in the battery pack to activate the protection circuit built in the battery pack and prohibit charging of the secondary battery. Without effectively changing the battery pack, charge control circuit, and load connection configuration, effectively preventing deterioration of battery characteristics due to repeated charging and discharging in a state close to the fully charged state of the secondary battery In practice, a great effect can be obtained.

Hereinafter, a battery pack and an electronic apparatus according to an embodiment of the present invention will be described with reference to the drawings, taking a mobile phone attached with the battery pack 10 as an example.
FIG. 1 shows a schematic configuration of an electronic apparatus according to this embodiment. Basically, like the electronic apparatus shown in FIG. 3, a charge control circuit 20 to which power is supplied from a charge adapter 40 as an external power source. And the battery pack 10 and the load 30 connected to the power output terminals 21 and 22 of the charge control circuit 20. In addition, the same code | symbol is attached | subjected and shown to the same component as the component of the conventional electronic device shown in FIG.

  In particular, this electronic device is characterized in that when a predetermined control voltage is applied to the protection circuit in the battery pack 10 via the external connection terminal 18 of the temperature sensor 17, the charge prohibition switch 14 of the protection circuit is set. A drive circuit (semiconductor switch) 19 for forcibly shutting off (off) and prohibiting charging of the secondary battery 13 is provided, and a supply current (charge current) from the charge control circuit 20 to the battery pack 10 is detected. In addition, a charging current detection circuit 50 is provided that applies a predetermined control voltage to the external connection terminal 18 of the temperature sensor 17 when the charging current I is less than a predetermined current threshold Ith.

  Incidentally, the charge current detection circuit 50 includes a shunt resistor 51 provided between the power output terminal 21 of the charge control circuit 20 and the charge / discharge terminal 11 of the battery pack 10, and a voltage generated between both ends of the shunt resistor 51. The control IC 52 detects the charging current I of the secondary battery 13 and compares it with a predetermined current threshold Ith. The control IC 52 detects the voltage of the shunt resistor 51 corresponding to the current value, and outputs an H signal that is an ON signal when the current value falls below a predetermined current threshold value. This is the same as the control IC in the charge control circuit 20 described above. The drive circuit (semiconductor switch) 19 is composed of a MOS-FET whose source and drain are connected in parallel between the gate and drain of the MOS-FET constituting the charge prohibition switch 14. The semiconductor switch (MOS-FET) 19 conducts (turns on) when a predetermined control voltage of its gate is applied in response to an ON signal from the control IC 52, whereby the charge inhibition switch (MOS-FET) 14 is turned on. Functions to shut off (off).

  Thus, according to the electronic apparatus configured as described above, the charging current detection circuit 50 provided between the charging control circuit 20 and the battery pack 10 supplies the current supplied to the battery pack 10 and, consequently, the charging of the secondary battery 13. The current can be detected independently of the charge control circuit 20. When the charging current of the secondary battery 13 falls below a predetermined current threshold value, the secondary battery is activated by operating the protection circuit of the battery pack 10, particularly the charging prohibition switch 14 via the external connection terminal 18 of the temperature sensor 17. 13 can be prohibited from being charged. Therefore, it is possible to effectively prevent the secondary battery 13 from repeatedly charging and discharging in a state close to a fully charged state, and the secondary battery accompanying the repeated charging and discharging in a state close to the fully charged state. Thus, it is possible to prevent the battery characteristics from deteriorating. In addition, the symbol R described in common in each drawing has each shown resistance.

  Further, according to the electronic device described above, the function of the protection circuit basically provided in the battery pack 10 is effectively used to prohibit the charging of the secondary battery 13 and the temperature sensor 17 in the battery pack 10 is also prohibited. The external connection terminal 18 is used to provide a control signal for prohibiting the charging of the secondary battery 13, so that it is not necessary to provide a new terminal in the battery pack 10, the charge control circuit 20, or the like. Therefore, the basic configuration of the electronic device can be utilized as it is, and charging of the secondary battery 13 in the fully charged state can be reliably prohibited.

  Here, an example in which the charging current detection circuit 50 is realized as an external circuit provided between the charging control circuit 20 and the battery pack 10 is shown, but it is needless to say that the charging current detection circuit 50 is realized as an internal circuit of the battery pack 10. Is possible. If comprised in this way, an electronic device can be implement | achieved, without changing the connection structure of the charge control circuit 20 and the said battery pack 10, and the change of the circuit specification with respect to the existing electronic device shown in FIG. 3 is also easy. It is.

  By the way, it is also possible to prohibit the discharge of the secondary battery 13 using the external connection terminal 18 of the temperature sensor 17 described above. In this case, for example, as shown in FIG. 2, a control signal output from the load 30 is used to shut off (turn off) the discharge prohibition switch (MOS-FET) 15 of the protection circuit in the battery pack 10. It ’s fine. Specifically, the source and drain of a semiconductor switch (MOS-FET) 19 are connected in parallel between the gate and drain of a MOS-FET forming the discharge inhibition switch 15, and the gate of the semiconductor switch (MOS-FET) 19 is connected to the outside. A predetermined control voltage may be applied via the connection terminal 18 to turn on the MOS-FET 19 and thereby cut off the discharge inhibition switch (MOS-FET) 15. With this configuration, it is possible to easily prevent unintentional discharge of the secondary battery 13 under the control of the load 30.

  The present invention is not limited to the embodiment described above. For example, as the drive circuit 19 that forcibly activates the protection circuit in the battery pack 10 and prohibits the charging of the secondary battery 13, it is possible to use a circuit other than the semiconductor switch described above. Various configurations can be employed for the charging current detection circuit 50 as well. In short, the present invention can be implemented with various modifications without departing from the gist thereof.

1 is a schematic configuration diagram of an electronic device according to an embodiment of the present invention. The figure which shows the application example of this invention. 1 is a schematic configuration diagram of a conventional general electronic device.

Explanation of symbols

10 Battery pack 13 Secondary battery 15 Charge prohibition switch (protection circuit)
19 Semiconductor switch (drive circuit)
17 Temperature sensor (Thermaster)
20 Charge control circuit 30 Load 40 Charge adapter (external power supply)
50 Charging current detection circuit

Claims (5)

A secondary battery, a temperature sensor for detecting the temperature of the secondary battery and outputting the detected temperature information via an external connection terminal, and the secondary battery provided between the secondary battery and the charge / discharge terminal A battery pack with a built-in protection circuit that prohibits charging and discharging of the battery,
The battery pack further comprises a drive circuit that forcibly activates the protection circuit when a predetermined control voltage is applied via an external connection terminal of the temperature sensor.   The battery pack according to claim 1, wherein the drive circuit includes a switch element that forcibly activates a charge prohibition switch in the protection circuit. A battery pack incorporating a secondary battery, a temperature sensor for detecting the temperature of the secondary battery, and a protection circuit for prohibiting charging and discharging of the secondary battery;
A power output terminal to which a charge / discharge terminal of the battery pack is connected; and a sensor input terminal to which an external connection terminal of the temperature sensor in the battery pack is connected; and an output current through the power output terminal is predetermined. When the current threshold value is not reached, and when the temperature of the secondary battery detected by the temperature sensor and obtained through the sensor input terminal exceeds a predetermined temperature threshold value, the power output through the power output terminal is prohibited. A charge control circuit having a charge control switch;
An electronic device comprising a load connected in parallel with the battery pack to the power output terminal of the charge control circuit,
When a predetermined control voltage is applied to the battery pack via the external connection terminal of the temperature sensor, a drive circuit for forcibly operating the protection circuit is incorporated,
Charging that detects a supply current from the power output terminal of the charge control circuit to the battery pack and applies a predetermined control voltage to the external connection terminal of the temperature sensor when the supply current is less than a predetermined current threshold An electronic device comprising a current detection circuit.   The electronic device according to claim 3, wherein the drive circuit includes a switch element that forcibly activates a charge prohibition switch in the protection circuit.   The charge current detection circuit is realized as an external circuit provided between a power output terminal of the charge control circuit and a charge / discharge terminal of the battery pack, or as a built-in circuit incorporated in the battery pack. Item 4. The electronic device according to Item 3.

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