JP2002315225A - Battery pack and external host equipment system using battery pack as power source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively draw a discharging capacity by suppressing a voltage drop of a large current period of pulse discharge with a simple circuit constitution and control. SOLUTION: An external host equipment system using a battery pack as a power source comprises a secondary cell 1, control switches 3, 4 for turning on/off charging/discharging current of the cell, temporary power storage circuits C1, L2, SW1 and SW2 each having a capacitor, a reactor and a switch element for temporarily storing power from the cell and outputting the power in parallel with a discharge current route passing through the control switches, and a control circuit 2 for controlling the switches and the storage circuits based on a signal from the external host equipment. The control circuit 2 controls the switches SW1, SW2 so as to store the power of the capacitor C1 of the storage circuit and to store the power of the capacitor in the reactor L1 and to output the power, based on the signal from the host equipment, suppresses the drop in the battery voltage during the large current period of the pulse discharge and effectively draws the discharging capacity of the secondary cell.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a battery pack corresponding to a large current period of pulse discharge and an external host device system using the battery pack as a power source.

[0002]

2. Description of the Related Art FIG. 3 is a view schematically showing the structure of a conventional battery pack, wherein 11 is a secondary battery, 12 is a monitor circuit, 13
Denotes a control circuit, 14 denotes a charge / discharge FET, 17 denotes a communication line, 18 denotes a bus, and 19 denotes a connector.

As shown in FIG. 3, for example, a battery pack includes a rechargeable secondary battery 11 and a monitor circuit 1 for monitoring them.
2, a control circuit 13 for communicating with the outside and controlling the inside of the battery pack, a charge / discharge FET 14 as a switch element for directly controlling charge / discharge, a connector 19 for connection to the outside, and the like.

The monitor circuit 12 monitors the charge / discharge state of the secondary battery 11, and includes, for example, a voltage detection circuit and a temperature detection circuit. By controlling the FET 14, the charge / discharge current is cut off to perform overcharge protection and overdischarge protection.

The control circuit 13 is, for example, a control IC for taking in data indicating the charge / discharge state detected by the monitor circuit 12, transmitting and receiving data and commands through communication with an external host device system, and controlling the charge / discharge FET 14.

[0006]

The discharge capacity of the battery pack can be increased by keeping the discharge current as constant as possible and suppressing the fluctuation of the battery voltage.
At the time of large current discharge, there is a problem that the discharge time is reduced because the battery voltage is reduced. Further, at low temperatures, the internal discharge impedance of the battery becomes large, so that the original discharge capacity cannot be obtained. As described above, in the battery pack, when the load is high, when the temperature is low, or when the discharge capacity is reduced, the internal impedance or the like causes a sudden drop in output, and the discharge capacity of the secondary battery cannot be used up effectively. There is.

Therefore, in a conventional battery pack using a secondary battery as a supply source, the voltage of the secondary battery is increased after the voltage of the secondary battery is increased in order to make it possible to use the discharge capacity of the secondary battery effectively even if the voltage drops. A corresponding proposal has been made by providing a booster circuit so as to be adjusted and used by a regulator (for example, see JP-A-6-291710 and JP-A-7-334257). However, such a conventional combination of a booster circuit and a regulator has a problem that the circuit configuration and control become complicated.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and is intended to suppress a voltage drop during a large current period of pulse discharge by a simple circuit configuration and control, and to effectively draw out a discharge capacity. Is what you do.

For this purpose, the present invention comprises a secondary battery, a control switch for turning on / off a charging / discharging current of the secondary battery, a capacitor, a reactor, and a switch element for temporarily storing power from the secondary battery. A temporary power storage circuit that outputs in parallel with a discharge current path passing through the control switch, and a control circuit that controls the control switch and the temporary power storage circuit based on a signal from an external host device, wherein the control circuit includes: A battery pack characterized in that the switch element is controlled to store power in the capacitor of the temporary power storage circuit and then store and output the power of the capacitor in the reactor based on a signal from the external host device. is there.

The control circuit controls the temporary power storage circuit on condition that the battery voltage at the time of discharge falls below a predetermined voltage, and the control switch includes a charge FET and a discharge F
ET, the control circuit turns off the charging FET when outputting power from the temporary power storage circuit, the temporary power storage circuit connects a rectifier on the output side, and the control circuit controls the temperature of the battery. Detecting means for detecting the battery temperature, operating the temporary power storage circuit as a DC / DC converter on the condition that the battery temperature falls below a predetermined value, boosting the battery voltage, and correlating the battery over-discharge detection voltage with the battery temperature. It is characterized by being changed.

Further, the battery pack is used as an external host device system including a battery pack and an external host device supplied with power from the battery pack, and the external host device controls the control immediately before a large current period of pulse discharge. A signal is provided to the pack, and the control circuit controls the switch element to store the power in the capacitor of the temporary power storage circuit and then store and output the power of the capacitor in the reactor based on the control signal. It is characterized by the following.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a view showing an embodiment of a battery pack according to the present invention, wherein 1 is a secondary battery, 2 is a control IC, 3 is a discharge FET, 4 is a charge FET, C1 is a capacitor, L1 is a reactor, and R1 is Resistance, SW1, SW2
Indicates a switch, and ZD1 indicates a Zener diode.

In FIG. 1, a secondary battery 1 is a chemical cell such as a lithium ion battery or a lithium polymer battery. The control IC 2 detects a battery voltage to protect the battery from overcharge or overdischarge, and determines whether the battery voltage is equal to or higher than a predetermined fixed voltage (set voltage) or equal to or lower than a predetermined voltage.
A protection circuit that controls on / off of the discharge FET 3 and on / off of the charge FET 4 in response to the current to cut off the charge / discharge current at the time of overcharge or overdischarge, thereby performing overcharge protection and overdischarge protection.

A capacitor C1, a reactor L1, and switches SW1 and SW2 temporarily store power from the secondary battery 1 and output the power in parallel with a discharge current path passing through a control switch including a discharge FET 3 and a charge FET 4. The resistor R1 is a current limiting resistor. This temporary power storage circuit includes a switch SW1, a reactor L1, a Zener diode ZD together with a resistor R1.
1 is connected in parallel with the series circuit of the discharge FET 3 and the charge FET 4, a capacitor C1 is connected between the input side and the − side of the reactor L1, and a switch SW2 is connected between the output side and the − side. To operate as a DC / DC converter.

A control IC is provided for the temporary power storage circuit.
2 stores power from the secondary battery to the capacitor C1 by turning on the switch SW1 and turning off the switch SW2. The switch SW1 is turned off and the switch SW2 is turned on in response to the PD signal from the external host device immediately before the large current period for performing the pulse discharge, the power of the capacitor C1 is stored in the reactor L1, and the large current of the pulse discharge starts to flow. The time point is set as the falling edge of the PD signal and the switch SW2
Is turned off, the power stored in reactor L1 is output through zener diode ZD1.

FIG. 2 is a diagram for explaining the operation timing of the circuit shown in FIG. The above operation will be described more specifically. Now, the discharge current in the external host device is
There is a large current period while a small current flows as shown in FIG. FIG. 2 immediately before the high current period from the external host device.
A pulse PD signal as shown in (F) is supplied to the control IC 2. In response to the PD signal, the control IC 2 switches the switch SW2 at the rising edge as shown in FIG.
Turn on. When the switch SW2 is turned on, a current flows from the capacitor C1 to the reactor L1 through the switch SW2 as shown in FIG.

Next, when the PD signal falls and a large current period is reached, the switch SW2 is turned off as shown in FIG. 2C at the falling of the PD signal. When the switch SW2 is turned off, the current of the reactor L1 that has been flowing through the switch SW2 is output through the Zener diode ZD1 as shown in FIG. 2E and supplied to an external host device. Therefore, the current supplied through the Zener diode ZD1 can reduce the current supplied from the secondary battery 1 to the external host device directly through the discharge FET 3 during the large current period. Can be reduced from the solid line to the dotted line during the large current period.

The switch SW1 is connected to the capacitor C1
Since the power is turned on to store power, the switch SW2 may be controlled to be turned on for a certain period required for storing power in the capacitor C1 while the switch SW2 is turned off, or the switch SW2 may be turned on from off. After that, as shown in FIG. 2C, control may be performed so that the switch is turned on after the elapse of the large current period until immediately before the switch SW2 is turned on.

When the battery voltage is equal to or higher than a predetermined value, the control IC 2 keeps the switch SW2 off, does not store power in the reactor L1, and when the battery voltage is lower than the predetermined value, the control IC 2 operates as described above. The switch SW1 is turned off and the switch SW1 is turned off in response to the rise of the PD signal from the host device.
2 may be controlled to be turned on. by this,
When a current flows through the switch SW2, power is stored in the reactor L1 from the capacitor C1, and the PD signal falls, the switch SW2 is turned off. At this time, a back electromotive force is generated in reactor L1, and Zener diode ZD
1, a current can flow, and the large current of the pulse discharge can be partially compensated.

Further, by providing a thermistor in close contact with the battery and measuring the resistance value of the thermistor,
The battery temperature is detected, and the battery temperature is set to a predetermined value, for example, 0 ° C.
When the battery voltage becomes equal to or lower than a predetermined value, for example, 3 V or less, the switch SW2 is turned on / off at several tens of kHz, and DC
It may be controlled to operate as a / DC converter to increase the battery voltage. Also in this case, since a capacitor is usually inserted in the input section of the external host device, the output voltage is stabilized.

At this time, if the overdischarge detection voltage of the control IC is, for example, usually 2.5 V in accordance with the battery temperature, the overdischarge detection voltage decreases as the battery voltage decreases, such as 2 V at 0 ° C. The energy stored in the battery can be taken out even if the internal impedance of the battery increases.

When the switch FET2 is turned off when the switch SW2 is turned off, the rechargeable battery 1 can be prevented from being recharged, and current is supplied to the external host device. Then, when a predetermined period has elapsed, the charging FET 4 is turned on, the switch SW1 is turned on, and the electric charge is stored in the capacitor C1. By doing so, an excessive load is not applied during the small current period and the capacitor C
1 can store an electric charge.

It should be noted that the present invention is not limited to the above embodiment, and various modifications are possible. For example, in the above embodiment, the discharge FET 3 and the charge FET 4 are inserted on the + side, but they may be inserted on the − side. Although the Zener diode is connected to the output side of the temporary power storage circuit, a diode or another rectifying element may be used. As for the PD signal from the external host device, the switch SW2 was turned on at the rising edge and turned off at the falling edge using a pulse signal.
Only one timing signal may be received, and thereafter, the off timing and the on / off timing of the switch SW1 may be controlled according to a fixed time schedule.

[0024]

As is apparent from the above description, according to the present invention, a secondary battery, a control switch for turning on / off the charge / discharge current of the secondary battery, a capacitor, a reactor, and a switch element are provided. A temporary power storage circuit that temporarily stores power from the secondary battery and outputs the power in parallel with a discharge current path passing through the control switch, and a control circuit that controls the control switch and the temporary power storage circuit based on a signal from an external host device. The control circuit controls the switch element to store the power in the capacitor of the temporary power storage circuit and then store and output the power of the capacitor in the reactor based on the signal from the external host device. With the control, the output of the temporary power storage circuit can be used together with the output of the secondary battery during the large current period of the pulse discharge, suppressing the battery voltage from dropping, It can be pulled out to enable the discharge capacity of the pond.

The control circuit controls the temporary power storage circuit on condition that the battery voltage at the time of discharging falls below a predetermined voltage. The control switch includes a charging FET and a discharging FET. When the power is output from the storage circuit, the charging FET is turned off, the temporary power storage circuit is connected to a rectifier on the output side, and the control circuit is provided with detection means for detecting the temperature of the battery. The temporary power storage circuit operates as a DC / DC converter under the condition that the battery voltage becomes zero, the battery voltage is boosted, and the overdischarge detection voltage of the battery is changed in correlation with the battery temperature, so that the power of the temporary power storage circuit is wasted. It is possible to effectively use the battery and control according to the battery temperature and the battery voltage.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of a battery pack according to the present invention.

FIG. 2 is a diagram for explaining operation timing of the circuit shown in FIG. 1;

FIG. 3 is a diagram showing a configuration outline of a conventional battery pack.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Secondary battery, 2 ... Control IC, 3 ... Discharge FET, 4 ... Charge FET, C1 ... Capacitor, L1 ... Reactor, R1
... Resistance, SW1, SW2 ... Switch, ZD1 ... Zener diode

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5G003 AA04 BA01 CB01 DA16 GA01 5H040 AA01 AA03 AA40 AS11 AY08 DD08

Claims (7)

[Claims] 1. A control switch comprising a secondary battery, a control switch for turning on / off a charging / discharging current of the secondary battery, and a capacitor, a reactor, and a switch element for temporarily storing power from the secondary battery. A temporary power storage circuit that outputs the temporary power storage circuit in parallel with a discharge current path passing therethrough, and a control circuit that controls the control switch and the temporary power storage circuit based on a signal from an external host device. A battery pack, comprising: storing power in a capacitor of a circuit; and controlling the switch element so as to store and output the power of the capacitor in the reactor based on a signal from the external host device. 2. The battery pack according to claim 1, wherein the control circuit controls the temporary power storage circuit on condition that a battery voltage at the time of discharging falls below a predetermined voltage. 3. The battery according to claim 1, wherein the control switch comprises a charge FET and a discharge FET, and wherein the control circuit turns off the charge FET when outputting power from the temporary power storage circuit. pack. 4. The battery pack according to claim 1, wherein the temporary power storage circuit has a rectifier connected to an output side. 5. The control circuit includes a detecting means for detecting a battery temperature, and operates the temporary power storage circuit as a DC / DC converter on condition that the battery temperature becomes a predetermined value or less, and controls a battery voltage. The battery pack according to claim 1, wherein the pressure is increased. 6. The battery pack according to claim 5, wherein the control circuit changes the overdischarge detection voltage of the battery in correlation with the battery temperature. 7. In an external host device system including a battery pack and an external host device supplied with power from the battery pack, the battery pack turns on / off a secondary battery and a charge / discharge current of the secondary battery. A control switch, a temporary power storage circuit comprising a capacitor, a reactor, and a switch element for temporarily storing power from the secondary battery and outputting in parallel with a discharge current path passing through the control switch; and control from the external host device. A control circuit that controls the control switch and the temporary power storage circuit based on a signal,
The external host device supplies the control signal to the pack immediately before a high current period of pulse discharge, and the control circuit includes:
Externally using a battery pack as a power supply, wherein the switch element is controlled so as to store power in the capacitor of the temporary power storage circuit and then store and output the power of the capacitor in the reactor based on the control signal. Host equipment system.