JP4189987B2 - Battery pack and external host device system using the battery pack as a power source - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
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]
[Prior art]
FIG. 3 is a diagram showing a configuration outline of a conventional battery pack. 11 is a secondary battery, 12 is a monitor circuit, 13 is a control circuit, 14 is a charge / discharge FET, 17 is a communication line, 18 is a bus, 19 is Indicates a connector.
[0003]
For example, as shown in FIG. 3, the battery pack includes a rechargeable secondary battery 11, a monitor circuit 12 that monitors them, a control circuit 13 that performs communication with the outside and controls the battery pack, and a switch that directly controls charging and discharging. It comprises a charge / discharge FET 14 which is an element, a connector 19 for connecting to the outside, and the like.
[0004]
The monitor circuit 12 monitors the charge / discharge state of the secondary battery 11 and has, for example, a voltage detection circuit, a temperature detection circuit, and the like, and controls the charge / discharge FET 14 when an abnormal voltage or an abnormal temperature is detected. The charge / discharge current is cut off, and overcharge protection and overdischarge protection are performed.
[0005]
The control circuit 13 is, for example, a control IC that takes in data indicating the charge / discharge state detected by the monitor circuit 12, exchanges data and commands through communication with an external host device system, and controls the charge / discharge FET 14.
[0006]
[Problems to be solved by the invention]
The discharge capacity of the battery pack can be increased by keeping the discharge current as constant as possible and suppressing fluctuations in the battery voltage. However, in the case of pulse discharge, the discharge time decreases because the battery voltage decreases during high current discharge. There is a problem. Further, since the internal impedance of the battery becomes large at low temperatures, the original discharge capacity cannot be taken out. As described above, in battery packs, problems such as a sudden drop in output due to the effects of internal impedance, etc., when connected to high loads, at low temperatures, or when the discharge capacity is reduced, cannot effectively use up the discharge capacity of the secondary battery. There is.
[0007]
Therefore, in a battery pack using a conventional secondary battery as a supply source, the secondary battery voltage is boosted and adjusted with a regulator in order to effectively use the discharge capacity of the secondary battery even if the voltage drops. A proposal has been made to provide a booster circuit so that it can be used (see, for example, JP-A-6-291710 and JP-A-7-334257). However, the conventional correspondence that combines such a booster circuit and a regulator has a problem that the circuit configuration and control become complicated.
[0008]
[Means for Solving the Problems]
The present invention solves the above-described problems, and suppresses a voltage drop during a large current period of pulse discharge by a simple circuit configuration and control so as to effectively draw out a discharge capacity.
[0009]
For this purpose, the present invention comprises 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, and temporarily stores electric power from the secondary battery for the control. A temporary power storage circuit that outputs in parallel with a discharge current path passing through the switch, and a control circuit that controls the control switch and the temporary power storage circuit based on a control signal from an external host device, the control switch comprising a charge FET And the discharge FET, and the control circuit stores the power in the capacitor of the temporary power storage circuit and then stores the power of the capacitor in the reactor based on a control signal from the external host device and outputs the switch. controls the device, the one o'clock power in parallel with the discharge current path through the control switch to turn off the charging FET It is characterized in that the output power from the built circuit.
[0011]
Further, as an external host device system including a battery pack and an external host device receiving power supply from the battery pack, in the external host device system including a battery pack and external host device receiving power supply from the battery pack, the battery pack includes: A secondary battery, a control switch for turning on / off a charge / discharge current of the secondary battery, a capacitor, a reactor, and a switch element, and a discharge current that temporarily stores power from the secondary battery and passes through the control switch A temporary power storage circuit that outputs in parallel with a path; and a control circuit that controls the control switch and the temporary power storage circuit based on a control signal from the external host device, wherein the external host device has a large current for pulse discharge. giving the control signal immediately before the period in the battery pack, the control circuit, the co temporary power storage circuit Is characterized in that for controlling the switching element so that the power of the capacitor to output stored in the reactor based on the control signal from the stored power to the capacitor.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing an embodiment of a battery pack according to the present invention, where 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 Resistors, SW1 and SW2 are switches, and ZD1 is a Zener diode.
[0013]
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 the battery voltage in order to protect overcharge and overdischarge, and the discharge FET 3 according to whether the battery voltage is higher than a predetermined voltage (set voltage) or lower than a predetermined voltage. Is a protection circuit that controls overcharge protection and overdischarge protection by cutting off the charge / discharge current in the case of overcharge or overdischarge by controlling on / off of the charge FET4.
[0014]
Capacitor C1, reactor L1, and switches SW1 and SW2 constitute a temporary power storage circuit that temporarily stores power from secondary battery 1 and outputs it in parallel with a discharge current path that passes through a control switch including discharge FET3 and charge FET4. The resistor R1 is a current limiting resistor. In this temporary power storage circuit, a series circuit of a switch SW1, a reactor L1, and a Zener diode ZD1, together with a resistor R1, is connected in parallel to a series circuit of a discharge FET 3 and a charge FET 4, and between the input side and the negative side of the reactor L1. The capacitor C1 is connected to the switch SW2, and the switch SW2 is connected between the output side and the negative side to operate as a DC / DC converter.
[0015]
For the temporary power storage circuit, the control IC 2 stores power from the secondary battery to the capacitor C1 by turning on the switch SW1 and turning off the switch SW2. Then, immediately before the large current period in which pulse discharge is performed, the PD signal is received from the external host device, the switch SW1 is turned off, the switch SW2 is turned on, the electric power of the capacitor C1 is stored in the reactor L1, and the large current of pulse discharge begins to flow. By turning off the switch SW2 with the time point falling as the PD signal, the electric power stored in the reactor L1 is output through the Zener diode ZD1.
[0016]
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 such that a small current flows and a large current period is as shown in FIG. A pulse PD signal as shown in FIG. 2F is supplied to the control IC 2 immediately before the large current period from the external host device. In response to the PD signal, the control IC 2 turns on the switch SW2 at the rising edge as shown in FIG. When the switch SW2 is turned on, a current flows from the capacitor C1 to the reactor L1 through the switch SW2 and increases as shown in FIG.
[0017]
Next, when the PD signal falls and enters a large current period, the switch SW2 is turned off at the fall of the PD signal as shown in FIG. Since 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 and supplied to the external host device as shown in FIG. Accordingly, since the current output through the Zener diode ZD1 can reduce the current supplied directly from the secondary battery 1 to the external host device through the discharge FET 3 during the large current period, the battery voltage is as shown in FIG. As shown by the solid line to the dotted line in FIG.
[0018]
Since the switch SW1 is turned on to store power in the capacitor C1, the switch SW1 may be controlled to be turned on only for a certain period required to store power in the capacitor C1 while the switch SW2 is turned off. After the switch SW2 is turned off, the control may be performed so that the switch SW2 is turned on after the large current period elapses and immediately before the switch SW2 is turned on as shown in FIG.
[0019]
Further, when the battery voltage is equal to or higher than the predetermined value, the control IC 2 keeps the switch SW2 off, does not store the power to the reactor L1, and when the battery voltage becomes lower than the predetermined value, The switch SW1 may be turned off and the switch SW2 may be turned on in response to the rise of the PD signal. As a result, current flows through the switch SW2, power is stored in the reactor L1 from the capacitor C1, and the switch SW2 is turned off when the PD signal falls. At this time, a counter electromotive force is generated in the reactor L1, a current flows through the Zener diode ZD1, and the large current of the pulse discharge can be partially compensated.
[0020]
Furthermore, a thermistor is provided in close contact with the battery, and the temperature of the battery is detected by measuring the resistance value of the thermistor. The battery temperature is a predetermined value, for example, 0 ° C. or less, and the battery voltage is a predetermined value, for example, 3V. When the following condition is reached, the switch SW2 may be turned on / off at several tens of kHz and operated as a DC / DC converter to increase the battery voltage. Even in this case, the output voltage is stabilized because a capacitor is usually inserted in the input section of the external host device.
[0021]
At this time, if the overdischarge detection voltage of the control IC is normally 2.5 V, for example, depending on the battery temperature, the overdischarge detection voltage is lowered as the battery voltage becomes lower, such as 2 V at 0 ° C. If it is changed, the energy stored in the battery can be taken out even if the internal impedance of the battery increases.
[0022]
When the switch SW2 is turned off, if the charging FET 4 is also turned off, the secondary battery 1 can be prevented from being recharged, and current is supplied to the external host device. Then, when the predetermined period has elapsed, the charging FET 4 is turned on and the switch SW1 is turned on to store the charge in the capacitor C1. By doing so, electric charge can be stored in the capacitor C1 without applying an excessive load during a small current period.
[0023]
In addition, this invention is not limited to the said embodiment, A various deformation | transformation is possible. For example, in the above embodiment, the discharge FET 3 and the charge FET 4 are inserted on the + side, but may be inserted on the − side. Further, although a Zener diode is connected to the output side of the temporary power storage circuit, a diode or other rectifying element may be used. For the PD signal from the external host device, the switch SW2 is turned on at the rising edge and turned off at the falling edge using a pulse signal. However, only one timing signal is received from the external host device, and then the constant is set. The off timing and the on / off timing of the switch SW1 may be controlled according to the time schedule.
[0024]
【The invention's effect】
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 switching element are temporarily included in the secondary battery. A temporary power storage circuit for storing electric power and outputting in parallel with a discharge current path passing through the control switch, and a control circuit for controlling the control switch and the temporary power storage circuit based on a control signal from an external host device The switch is composed of a charge FET and a discharge FET, and the control circuit stores the power in the capacitor of the temporary power storage circuit and then stores the power of the capacitor in the reactor based on the control signal from the external host device and outputs it. And turning off the charge FET to output power from the temporary power storage circuit in parallel with the discharge current path through the control switch, In addition, as an external host device system including a battery pack and an external host device receiving power supply from the battery pack, in the external host device system including a battery pack and an external host device receiving power supply from the battery pack, the battery pack includes: A secondary battery, a control switch for turning on / off the charging / discharging current of the secondary battery, and a discharge current path that temporarily stores power from the secondary battery and passes through the control switch, which is composed of a capacitor, a reactor, and a switch element And a control circuit for controlling the control switch and the temporary power storage circuit based on a control signal from the external host device. The external host device controls the control signal immediately before the large current period of the pulse discharge. The control circuit stores power in the capacitor of the temporary power storage circuit and then based on the control signal. Since the switch element is controlled so that the power of the capacitor is stored and output in the reactor, the output of the temporary power storage circuit should be used together with the output of the secondary battery during the high current period of pulse discharge with a simple circuit configuration and control. Therefore, it is possible to suppress the decrease in battery voltage and to effectively draw out the discharge capacity of the secondary battery.
[0025]
In addition, the temporary power storage circuit can be used effectively without wasting power, and control according to the battery temperature and battery voltage can be performed.
[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 the 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 ... Resistor, SW1, SW2 ... Switch, ZD1 ... Zener diode

Claims (2)

A secondary battery,
A control switch for turning on / off the charge / discharge current of the secondary battery;
A temporary power storage circuit comprising a capacitor, a reactor and a switch element, temporarily storing power from the secondary battery and outputting 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 control signal from an external host device, the control switch includes a charge FET and a discharge FET, and the control circuit includes a control circuit for the temporary power storage circuit. Based on a control signal from the external host device after storing power in a capacitor, the switch element is controlled to store and output the power of the capacitor in the reactor, and the control switch is turned off by turning off the charging FET. A battery pack , wherein power is output from the temporary power storage circuit in parallel with a discharge current path passing therethrough . In an external host device system comprising a battery pack and an external host device that receives power supply from the battery pack,
The battery pack is
A secondary battery,
A control switch for turning on / off the charge / discharge current of the secondary battery;
A temporary power storage circuit comprising a capacitor, a reactor and a switch element, temporarily storing power from the secondary battery and outputting in parallel with a discharge current path passing through the control switch;
A control circuit for controlling the control switch and the temporary power storage circuit based on a control signal from the external host device,
The external host device gives the control signal to the battery pack immediately before a large current period of pulse discharge,
The control circuit controls the switch element to store power in the capacitor of the temporary power storage circuit and then to store and output the power of the capacitor in the reactor based on the control signal. External host equipment system that uses as a power source.

Images