JPH02168820A - Charge/discharge switching device for battery - Google Patents

Abstract

PURPOSE:To reduce the dimension and the cost, in a charger provided with a discharging circuit, by switching between charging operation and discharging operation through a transistor circuit. CONSTITUTION:Output terminal P1 of a microcomputer has a high level during initial quick charge operation of a battery B, thereby transistors Q1, Q2 are turned ON and current flows through the transistor Q3 and a diode D thus charging the battery B. When the battery B is fully charged, the output terminal P1 has a low level thereby the transistors Q1, Q3 are turned OFF thus charging the battery B only with current flowing through the diode D. When the output terminal P2 of the microcomputer has a high level, transistors Q2, Q4 are turned ON thus discharging the battery B through the transistor Q4 and a resistor R9.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a storage battery charging device equipped with a discharge circuit.

(b) Conventional technology In the case of a Ni-Cd battery pack used as a power source for electrical equipment such as a camera-integrated video, the battery discharges and its output voltage increases to the load driving dark value voltage (per cell) of a motor etc. 1.15 to 1.18) or less, the battery becomes exhausted and it becomes necessary to charge the battery.

By the way, the threshold voltage for driving the load is usually set higher than the end-of-discharge voltage of the battery, and a small amount of remaining capacity always remains when the battery is being charged.

As shown in Figure 4, the battery (
When B,) is charged to -position charge and discharged again,
No matter how many times this operation is repeated, no significant change is observed in the discharge characteristics. On the other hand, as mentioned above, the battery with remaining capacity (B2
) is charged to full charge and then discharged again to the extent that there is residual capacity.
A phenomenon occurs in which the level of the terminal voltage decreases (indicated by a broken line in the figure) compared to B,). This phenomenon is called the battery memory effect, and when detecting a battery's full charge based on a change in terminal voltage, if the battery has remaining capacity, it will not be possible to charge it further after reaching the preset full charge state. The problem was that it continued.

In addition, experience has shown that the memory effect of a battery can be eliminated by forcibly discharging a battery with remaining capacity once to the end-of-discharge voltage, charging it to full capacity, and then repeating the same process once again. Are known.

In addition, before starting to charge the storage batteries, there is a system that discharges the storage batteries once to make the initial capacity of all the storage batteries the same and perform uniform charging (see Japanese Patent Publication No. 31175/1983).
Since the memory effect of the battery is not removed by - times of discharge, there is a problem in that a charging control system that detects the terminal voltage of the battery cannot accurately detect full charge.

FIG. 5 does not show an example of a conventional charging circuit with a discharging circuit. In the figure, +IC and ++ are microcomputer (hereinafter referred to as microcomputer j) that detects the voltage when the storage battery (B) is fully charged, and (R1) (R1□) is the - output of the microcomputer (Ice). The voltage dividing resistor inserted between the terminal (Pl) and the ground, (Ql) is the voltage dividing resistor (Rt)
The first PNP type with a common emitter whose base is connected to the voltage dividing point of (R, +□) and the collector side is connected to the voltage source (vll) via the resistor (R2). -Randister, (R4t(
Rt3) is the other output terminal (
The voltage dividing resistor (Q2) is inserted between the voltage dividing resistor fR4i (Rt3) and the ground, and its base is connected to the voltage dividing point of the voltage dividing resistor fR4i (Rt3).
A second PNP transistor (Q, ) with a common emitter connected to the collector resistor (R2) of the t-transistor (Q, )
3) has its base connected to the collector terminal of the first transistor (Ql) via the base resistor (R3), and its emitter terminal is connected to the charging power supply N-type third transistor; (D) is the third transistor (Q3); A backflow prevention diode (+t, +oHn+) connected between the emitter and collector of the resistor (R6) and a normally closed first relay switch (C5) that is closed by excitation of the relay coil (1'ly)
+) is connected in parallel with the battery (B) and in parallel with the relay coil (
A normally open second relay switch (
a voltage dividing resistor (R9) that is connected via C2) and generates a voltage corresponding to the terminal voltage of the battery (B) at its voltage dividing point;
are resistors connected in parallel with the voltage dividing resistor (RtoJ (Rz), (R7) and (R8) are connected between the anode terminal of the diode (D) and the ground and have a high resistance value, and are connected to the battery (
A resistor (IC2) that generates a voltage corresponding to the terminal voltage of B) at the voltage dividing point connects its input terminal (■,) to the voltage dividing resistor (IC2).
R30) fRll), and the input terminal (12) is connected between the voltage dividing resistor (R7) (88); (S) is the input terminal ( The battery flows to the input terminal (113i) and the discharge of the battery (B) starts.

In this example, the battery (B) is set in the circuit, the power supply tv, , +VB) is turned on, the output terminal P of the microcomputer (Ice) is set to "H" (quick charge mode), and the The first transistor (Ql) and the third transistor (Q3) conduct, and a large current flows from the power supply (VA) to the battery (B) through the main current path of the transistor (Q,), the resistor (R6), and the diode (D). A small current is supplied at the same time. The terminal voltage of the battery (B) during charging is detected by a voltage dividing resistor (R7) (Re) and input to the input terminal (1□) of the integrated circuit (IC2). When the terminal voltage of the battery (B) reaches the voltage at full charge, the microcomputer (Ice) calculates the input of the integrated circuit (IC2) and sets the output of the output terminal (Pl) to "L". As a result, both the first and third transistors (Q+) ((hi) become non-conductive. Therefore, charging of the battery (B) is switched to I-recycle charging by the current passing through the resistor (R6) and the diode (D>). Next, when the switch (S> is closed, the output terminal (
The output terminal (P coil (Ry'r) is closed to open the relay switch (C1), and the relay switch (C2) is closed. In this state, the battery (B)
starts discharging and resistors (R7) and (Rho) (R1
1) A discharge current flows through. This discharge current is caused by resistance (Rho
) (R+ +) as the dividing point voltage of the integrated circuit (IC2
) is taken into the input terminal (I, ) of the battery, and the microcomputer (ICe) calculates the amount of discharge current by calculating the product of the voltage and the time to complete discharge (until reaching 1.OV per cell). (
Determine the deterioration of B).

However, as mentioned above, when switching between charging and discharging using a relay, the size of the printed circuit board is five times larger than when it is assembled using a transistor circuit, and the manufacturing cost is also about 10 times higher. was there.

(c) Problems to be Solved by the Invention The problems to be solved by the present invention are, in order to eliminate the memory effect of batteries, to use a transistor circuit to switch between charging and discharging in a charging device equipped with a discharging circuit. The objective is to reduce the external dimensions of the container and reduce manufacturing costs.

(d) Means for Solving the Problem A first transistor whose base is connected to one output terminal of the microcomputer and is turned on when charging a battery, and a first transistor whose base is connected to another output terminal of the microcomputer are connected. a storage battery connected in series to the main current path; a backflow prevention diode connected via a resistor between the corephthal emitter of the third transistor; and a fourth transistor that is conductive.

(e) Charging of the working battery is carried out by the current flowing through the main current path of the third transistor due to the conduction of the third transistor due to the conduction of the first transistor, and at the same time via the resistor and diode between the corephthal emitters of the third transistor. It is also done.

When the battery is discharged, the fourth transistor is turned on due to the conduction of the second transistor.
This is done by the current flowing through the main current path of this fourth transistor due to the conduction of the h transistor.

The microcomputer determines full charge based on the terminal voltage of the battery during charging, and calculates the end of discharging based on the discharge voltage during discharging.

(F) Embodiment FIG. 1 shows an embodiment of the charge/discharge switching device of the present invention. Fifth
The difference from the conventional one shown in the figure is that the second transistor (
The collector terminal of C2) is connected to the collector terminal of the third transistor (Q, ) by connecting the main current path to the collector terminal of the third transistor (Q, ).
A resistor (R5) is connected to the base of the PN type fourth transistor (C4).
), and the fourth transistor (
A resistor (R9) and (RIOI) are connected to the collector terminal of C4).
(This is the point where R11+ is connected, and the other configuration is the same as that in FIG. 1.

Figure 2 shows an excerpt of the main part of Figure 1. In the figure, during the first rapid charging of the battery (B) (time T + ), the output terminal (P, ) of the microcomputer (Ice) is at the "H" level and the first,
The third transistor (Ql) (C3) conducts, and the large current (jc+) passing through the third transistor (ql) and the resistance (R
6) and a small current (jC2) passing through the diode (D>), the fast charging current j Q (-jc++jCz)
It flows to B). The battery voltage when fully charged is determined by the resistance (R7) (R
8) is taken into the integrated circuit (IC2) through the voltage dividing point, and the microcomputer CICI) thereby makes the 1.3 transistor (qi) (lhi both non-conductive and supplies the supplementary charging current of only the small current fjc2). j T (-jC2) is supplied to the battery.

At time t, the switch (S) is closed to discharge the fully charged battery in the above process. That is, microcomputer (I+C+)
The output of the output terminal (R2) becomes rH, and the 2.4th transistor (C21 (04)) becomes conductive.

Therefore, the discharge current of the battery (B) is increased by the fourth transistor (C4
) base current (j B), current passing through the resistor (R9) (
The current (jC2) passing through the diode (D>
) is subtracted. Resistance (R1°) and (R++)
has a high resistance, and since only voltage VD2 is generated at the voltage dividing point, the current that flows is so small that it can be ignored. This is the same in the case of the current flowing through the resistors (R7) and (R8) during charging, and only the voltage VD is generated at the voltage dividing point. Since the current (jCz) flowing through the diode <D> and the base current (j[l) of the fourth transistor (C4) can be considered to be almost the same, the discharge current is approximately equal to the magnitude of jR. Therefore, during time T 2 (between t + and t2) the battery (B) is discharged with a current of jR, which means that the terminal voltage of the battery (B) is 1
1 per cell. ○It will continue until it reaches V.

The microcomputer (lc+) calculates the discharge capacity from the voltage dividing point VD2 of the resistor (R+o)in++) and the discharge time (tz t+), and if the value is 60% or more (relative to the nominal capacity), the battery (B) is It is determined that no memory effect has occurred, and the battery (B) is charged again until it is fully charged (time t3).

If it is less than 60%, the battery is fully charged again, then discharged again in the same manner as before to remove the memory effect, and then charged again to finally bring the battery (B) to a fully charged state.

(g) Effects of the Invention As described above, the present invention includes a first transistor whose base is connected to one output terminal of the microcomputer and is turned on when charging a battery, and a first transistor whose base is connected to the other output terminal of the microcomputer. The second conductor conducts when the battery is discharged.
a third transistor whose base is connected to the main current path of the first transistor and becomes conductive when the first transistor is conductive; a storage battery connected in series to the main current path of the third transistor; a reverse rain-proofing diode connected between the collector and emitter of the transistor through a resistor; and a fourth transistor whose base is connected to the twenty-first transistor to conductive when the second transistor is conductive.
1- We have provided a charging/discharging device consisting of a transistor that can switch between charging and discharging a storage battery, which can remove the memory effect from a battery where it has occurred, and reduce the usage time of the battery when fully charged. In addition to being able to achieve uniformity, the charge/discharge switching circuit using transistors is
Since the printed circuit board can be made smaller, the charging device itself can be made smaller, and manufacturing costs can also be reduced.
There is an effect that can be done.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing a charging/discharging device for a storage battery according to the present invention, Fig. 2 is a partial circuit diagram of Fig. 1 showing the current flow, and Fig. 3 is a time characteristic showing the terminal voltage during charging and discharging of the storage battery. Figure 4 is a diagram showing the difference in discharge characteristics depending on the presence or absence of the memory effect.
FIG. 5 is a conventional circuit diagram corresponding to FIG. 1. +IC++...Microcomputer, (Ql)...Eleventh transistor, (B)...Battery, (Q2)...Second transistor, (q,)...Third transistor, (R6
)...Resistance, (D>...Diode, (Q4)...
No. 47-Ransistau

Claims (1)

[Claims] (1) a first transistor whose base is connected to the output terminal of the microcomputer and which becomes conductive when charging the storage battery;
a second transistor whose base is connected to the other output terminal of the microcomputer and conducts when the battery is discharged; and a third transistor whose base is connected to the main current path of the first transistor and which becomes conductive when the first transistor is conductive. , the storage battery connected in series to the main current path of the third transistor, a backflow prevention diode connected between the collector and emitter of the third transistor via a resistor, and a base connected to the second transistor. A storage battery charging/discharging switching device comprising a fourth transistor that becomes conductive when the second transistor is conductive.