JP2002233067A - Power source device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power source device for improving the instability of the operation of a system due to voltage drop caused by the fluctuation of consumption power in the system in the body system of a portable information terminal or the like and the power source device combined therewith. SOLUTION: The power source device is connected through a protection circuit to the system supplying voltage or current from a secondary battery, discharge voltage of the secondary battery supplied to a protection circuit and the system are synchronized, and any one of at least discharge voltage and discharge current is supplied to the system from the secondary battery by making the synchronous signal of the system a reference.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device used in a mobile communication device or the like and employing a structure such as a battery pack containing a secondary battery, for example, a lithium secondary battery. The present invention relates to a power supply device capable of supplying power following fluctuations in power consumption in a system.

[0002]

2. Description of the Related Art In recent years, a power source of a portable device represented by a mobile communication device, a portable information terminal and a notebook PC has an advantage in terms of a chargeable / dischargeable secondary battery, particularly in terms of energy density. Lithium ion secondary batteries are preferably used. In these secondary batteries, overcharging or overdischarging that is not performed under appropriate charge / discharge conditions is performed, or when an overcurrent is applied, gas is generated due to decomposition of the electrolytic solution, short-circuiting and heating inside the battery, etc. Problems will occur. Therefore,
Various power supply devices including a protection circuit provided with a means for preventing overcharge, overdischarge, and overcurrent have been proposed. This protection circuit is a control circuit that detects and controls the charge / discharge voltage of the secondary battery.When the battery voltage becomes a charging prohibition voltage during charging, charging is prohibited, and the protection voltage is lower than the prohibition voltage and slightly lower than the reference voltage. When the battery voltage drops, charging is started again.When discharging, if the battery voltage falls below the discharge prohibition voltage, discharging is prohibited, and if the battery voltage becomes slightly higher than the discharge prohibition voltage, charging is started. Like that.

Referring to the configuration of the battery pack shown in FIG.
A conventional example will be described. The battery pack 23 contains a chargeable / dischargeable secondary battery, and has unit cells 20 and 21, which are unit batteries, for example, a lithium ion secondary battery, arranged in a charge / discharge path. The protection IC 22 detects the state of charge and discharge of the secondary battery, and detects the FE inserted into the charge / discharge path.
By controlling the ON / OFF states of T29 and T30, the battery is prevented from falling into an overcharged / discharged state. In addition, the housing of the battery pack 23 has a + terminal 24 for supplying power to the main body system to which the battery pack 23 is connected,
In addition to the terminal 25, an identification terminal 28 for outputting battery pack specific information is provided. As a specific operation of the protection IC 22, a case where the output of the charger is charged from the + terminal 24 and the − terminal 25 and an overcharge prohibition operation is activated will be described. When the secondary battery is charged with a voltage higher than the specified value, the protection IC 2
2 reaches the preset overcharge prohibition voltage,
The overcharge control FET 30 is turned off. As a result, the charge / discharge path is cut off, and charging is stopped. In the case of the overdischarge state, the overdischarge control FET 29 is turned off, and the charge / discharge path is cut off as in the case of the overcharge, and a protection operation for stopping the discharge is performed. The battery is prevented from falling.

Further, the battery pack is provided with a thermistor 26 in contact with the battery in order to add a temperature protection function at the time of charging, and the detected battery temperature is determined by a temperature terminal 27 (T). Output to the system. The thermistor 26 has a characteristic in which the resistance value varies depending on the temperature, for example, 10 KΩ at 25 ° C., and 3 K at 60 ° C.
At kΩ and 0 ° C., it changes to 27 kΩ and is used as a temperature detection terminal. The main body system detects the resistance value of the thermistor 27 via the temperature terminal 27 so that the battery temperature is recognized. By setting in advance the resistance value of the thermistor 27 at the temperature at which charging stops when the battery is heated in the main body system, it becomes possible to operate as a temperature protection function of the secondary battery from a change in resistance of the thermistor. . Further, the temperature fuse 31 also performs a temperature protection function, and cuts off the charge / discharge path when the temperature exceeds a specified temperature. At this time, the protection function by the thermal fuse is set to be higher than the operating temperature of the thermistor in consideration of the non-return type.

[0005]

The battery pack provided with the above-described protection circuit is widely used as a power source for various portable devices, but the characteristics required for the battery pack differ depending on the system on the main body side. . For example, digital mobile communication devices (cellular phones), particularly terminals employing the GSM system, which is the mainstream in European countries, have a maximum transmission output of up to 2 W, so that a power supply device including a battery pack is not used. It is necessary to supply the power required for transmission at the maximum output to the system on the main unit side. GSM
The transmission signal in the system is a burst signal. This signal is about 4.6 ms in one cycle, and 1/8 of one cycle is the time actually transmitted from the terminal, but consumes about 2 A at the maximum transmission output. On the other hand, the reception time is set to another ８ of the same period as the previous transmission signal, and the remaining time is a standby. The current consumption during the standby time is 1/10 to 1/2 of the current at the time of transmission.
0, which is very small. In addition, P which is the mainstream in Japan
Even in a terminal adopting the DC scheme, a large current is required only for the actual transmission time, as in the GSM scheme, and the difference between the current values required for transmission and other times is large.

[0006] As described above, in the mobile communication device, the system on the main body side depends on the state of transmission, reception and standby.
The power (current value) required by the system fluctuates greatly during one cycle. On the other hand, the battery pack which is a power supply source to the main body system supplies a constant voltage irrespective of fluctuation in power consumption due to the burst signal. For this reason, at the time of transmission where a large current flows, the discharge voltage of the secondary battery drops due to the internal resistance in the power supply system including the battery pack (secondary battery), and the voltage actually supplied to the system and the voltage of the secondary battery are reduced. A difference occurs between the discharge voltage and the discharge voltage. However, no measures have been taken against the voltage drop of the secondary battery caused by the difference in current required during transmission and during standby. As a result, the operating voltages of various devices on the system side during transmission decrease, and not only the functions cannot be sufficiently exhibited, but also the state of the system becomes unstable, which hinders functions as a mobile communication device such as call disconnection. There is a problem that it may come.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems, and stabilizes the system on the main body by changing the supplied power with high accuracy and stability in response to the power fluctuation on the main system. It is an object of the present invention to provide a power supply device capable of performing the above operation.

[0008]

In order to achieve the above object, a power supply device according to the present invention comprises a protection device having an overcharge and overdischarge detection circuit for detecting an overcharge / discharge state of a chargeable / dischargeable secondary battery. A power supply device including a circuit, which is connected to a system to which a voltage or a current is supplied from the secondary battery via the protection circuit, and includes a discharge voltage of the secondary battery supplied to the protection circuit. The system is synchronized with the system, and at least one of a discharge voltage and a discharge current is supplied from the secondary battery to the system based on a synchronization signal of the system.

According to this structure, the system on the main body side synchronizes with the power supply device, and supplies the discharge current and the discharge voltage in accordance with the synchronization signal from the system side, thereby coping with the power fluctuation on the system side. Since the supplied current and voltage are supplied, the system on the main body side enables stable operation.

In a power supply device equipped with a plurality of secondary batteries, at least one of the secondary batteries is connected to a DC / DC converter and connected to the other secondary battery via a switch. By making the supply voltage and current to the system variable, the discharge voltage supplied from the power supply device is kept constant by the DC-DC converter. Thereby, the stability of the operation in the system on the main body side is further kept higher.

On the other hand, it is preferable that the system is applied to a mobile communication device, and a power supply device combined with the mobile communication device synchronizes a discharge voltage or a discharge current with a transmission signal of the mobile communication device, and By making the supply voltage from one of the batteries discontinuous in time, it is possible to supply a current and a voltage corresponding to fluctuations in power consumption in this communication device. More preferably, the power supply device has a protection circuit terminal connected to the mobile communication device, extracts a synchronizing signal from an ACP signal in an amplifier of the mobile communication device, and performs switching in accordance with the synchronizing signal. Voltage and current to the communication device can be time controlled.

When a plurality of secondary batteries are mounted on the power supply device according to the present invention, the discharge voltage at the output terminal is equal to the discharge voltage corresponding to one secondary battery and the discharge voltage corresponding to two secondary batteries. A configuration may be employed in which switching can be performed in accordance with the discharge voltage connected in series and the load in the system on the main body side.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings using a power supply device combined with a mobile communication device as an example. FIG. 1 is a configuration diagram of a power supply device according to an embodiment of the present invention, in which a chargeable / dischargeable secondary battery is accommodated, and two unit cells as unit batteries are connected in series. As is clear from the figure, the battery pack
It has a basic configuration of a unit cell 1 and a unit cell 2, and a protection circuit 5 for controlling the charge and discharge states of the unit cell.
The protection circuit 5 controls charging / discharging based on the charging / discharging voltage of each of the unit cells 1 and 2, detects an overcharge / discharge state of the chargeable / dischargeable battery, and outputs an overcharge detection signal. An overdischarge detection circuit that outputs an overcharge detection signal is provided. Voltage and current are output from the protection circuit 5 to the main system from the + terminal 6 and the − terminal 7. Further, in the above configuration, the voltage of only the unit cell 1 from between the + terminal 6 and the − terminal 7,
And input / output voltages connected in series.

The output voltage of the unit cell 2 is controlled by a DC / DC converter 3. Between the unit cell 1 and the unit cell 2, a final-stage amplifier (hereinafter referred to as PA) in a transmission circuit portion of a mobile communication device is provided. The terminal which can detect the synchronizing signal of the automatic output control (APC) of ()) is set. In addition, it has a switching function for controlling an intermediate potential between the unit cells 1 and 2 in parallel with the control IC 8 side. Therefore, the FET is returned and the FET is
Is connected to the PA of the main system, and when the PA is turned on, it can be turned off. In the figure, the PA terminal is described as a synchronization terminal A9. As with the conventional battery pack shown in FIG. 2, a temperature terminal 8 connected to a thermistor for protection during charging.
(T) Also, the identification terminal 7 (S) is provided in the battery pack.

Hereinafter, an example will be described in which a lithium secondary battery is used for the unit cells 1 and 2 and the unit cell is used for a mobile communication device adopting the GSM system. Note that the nominal voltage of the lithium secondary battery is 3.6 V. In this mobile communication device, the maximum transmission output is 2W. In addition, the transmission / reception state 1
The cycle is a burst signal of about 4.6 ms, and transmission is performed for 1/8 cycle, reception is performed for 1/8 cycle, and the remaining time is in a standby state. In this device, the maximum output 2
In order to obtain W, when the operating voltage of the system is 3.6 V, a current of about 2 A is required. On the other hand, the current consumption is about 0.1 A in the reception time and about several mA less in the standby time. The maximum output transmission condition is determined by the transmission / reception level between the terminal and the base station receiving the terminal. In order to achieve the required transmission level, the level of PA in the transmission section of the terminal is controlled by APC according to the communication state with the base station, the operating voltage of the amplifier is varied, and the output level of the amplifier is adjusted. I have. In the GSM system, the voltage is controlled so that the output is usually at a 4 dB step interval. Also,
+ Terminal 6 and-terminal 7 of the battery pack including the conventional protection circuit
The impedance between them is about 200 mΩ.

When a current of 2 A at the time of the maximum transmission is sent, a voltage drop of about 0.4 V occurs due to the impedance of the battery pack. Considering that at most about 0.1 A during times other than transmission, the voltage drop is about 0.02 V, and the voltage effect is very small. On the other hand, from the viewpoint of the communication device which is the main body of the system, the transmission / reception 1
This means that the voltage of about 0.4 V fluctuates in the cycle. Voltage fluctuation is not preferable in terms of obtaining stable operation of various devices used in the transmission and reception systems of the system main body, and a fluctuation of 0.4 V with respect to a voltage of about 3.6 V has a very large effect.

When the operating voltage of the system is 3.6 V, in the conventional configuration, it is usual to use only the unit cell 1, but the voltage of the unit cell 2 is used to compensate for the voltage fluctuation. If the unit cells 1 and 2 are simply connected in series, an excessive voltage will result. Here, DC /
The DC converter 3 is installed, and the voltage is set to a required voltage. In this case, when a high current is required, the FET A4 is turned on and the FET A4 is turned on based on the synchronization signal at the time of the PA operation of the main system.
B11 is simultaneously turned off. In order to compensate for the voltage drop of 0.4 V from the above condition, the output voltage from the DC / DC converter 3 is set to the same potential as during the transmission time of the system. Since the voltage drop is small during periods other than the transmission time, the FET A4 is turned off and the FET B11 is simultaneously turned on. That is, to compensate for this voltage drop,
By using a DC-DC converter to synchronize with the burst signal of the system, the supply voltage during the operation of the main body system is kept constant, and a stable battery pack can be realized.

The present invention is intended to improve the instability of the system due to the difference in voltage drop between transmission and reception of a portable information terminal and a portable telephone. It can also be provided to portable devices such as personal computers and printers that need to supply a large current in a burst signal.

Although the present embodiment has been described in connection with the case where there are two unit cells, the same usage method can be used when three or more cells are connected in series and three or more cells are connected in parallel. Furthermore, although an example in which a lithium secondary battery is used as the unit cell has been described, even a secondary battery such as a polymer lithium battery, nickel hydride, or Ni-Cd can be obtained simply by increasing the required number of battery voltages. Can be treated similarly.

[0020]

As described above, in the power supply device of the present invention,
It is possible to improve the phenomenon that the system on the main body side becomes unstable due to the difference in the voltage drop amount.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a power supply device according to an embodiment.

FIG. 2 is a configuration diagram of a conventional power supply device.

[Explanation of symbols]

 1, 2 unit cell 3 DC / DC converter 4 FET 5 protection circuit 6 + terminal 7-terminal 8 control IC 9 synchronization terminal A 10 synchronization terminal B 11 FET 12 identification terminal 13 temperature terminal 20, 21 unit cell 22 protection IC 23 protection Circuit 24 + Terminal 25-Terminal 26 Thermistor 27 Temperature Terminal (T) 28 Identification Terminal (S) 29 Overdischarge Control FET 30 Overcharge Control FET

Claims (5)

[Claims] 1. A power supply device including a protection circuit provided with an overcharge and overdischarge detection circuit for detecting an overcharge / discharge state of a chargeable / dischargeable secondary battery, wherein the power supply device includes Connected to the system to which the voltage or the current is supplied through the protection circuit, and synchronizes the discharge voltage of the secondary battery supplied to the protection circuit with the system, and uses a synchronization signal of the system as a reference. And supplying at least one of a discharge voltage and a discharge current from the secondary battery to the system. 2. The power supply device has a plurality of secondary batteries mounted thereon, at least one of the secondary batteries being connected to a DC / DC converter and being connected to the other secondary battery via a switch. 2. The power supply device according to claim 1, wherein a supply voltage and a current supplied to the system can be varied. 3. The mobile communication device, wherein the power supply unit synchronizes a discharge voltage or a discharge current with a transmission signal of the mobile communication device, and adjusts a supply voltage from at least one battery in time. 3. The power supply according to claim 2, wherein the power supply is discontinuous. 4. The power supply device has a protection circuit terminal connected to the mobile communication device, extracts a synchronization signal from an ACP signal in an amplifier of the mobile communication device, and performs switching in accordance with the synchronization signal. 4. The power supply device according to claim 3, wherein voltage and current to the mobile communication device are time-controlled. 5. The power supply device has a plurality of secondary batteries mounted thereon, and a discharge voltage at an output terminal is connected in series with a discharge voltage corresponding to one secondary battery and two discharge batteries. The power supply device according to claim 2, wherein the power supply device is switched to the discharged discharge voltage.