JPH0119568Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to an automatic charging device for rapidly charging a secondary battery.

Conventional Structure and Problems Generally, when rapidly charging a secondary battery such as a Ni--Cd battery, it is necessary to charge it with a large charging current I, as shown in FIG. The charging voltage V increases as charging progresses, but for example, when the charging atmosphere temperature is 0°C, V ₁ point,
The charging voltage V increases to ₂ V points at 20°C and ₃ V points at 40°C, and if the large charging current I mentioned above continues to flow, each of the ₁ V points (t ₁ ), the battery internal pressure P rises rapidly at point V ₂ (t ₂ o'clock) and V ₃ point (t ₃ o'clock), and as charging progresses further, the battery internal pressure P reaches point P _D , where the battery's safety valve operates. is reached and actuates said safety valve, thereby:
This led to a decrease in lifespan. In order to eliminate such problems, the battery internal pressure P begins to rise.
As shown in Fig. 2 from t ₁ , t ₂ , and t ₃ , it is sufficient to gradually reduce the charging current I. When the charging current I is gradually reduced in this way, as shown in Fig. 2, the battery Since the internal pressure P is suppressed to P ₁ ′, P ₂ ′, and P ₃ ′, the battery can be rapidly charged without reaching the operating pressure P _D of the safety valve.

Figure 3 shows the circuit configuration of a conventional automatic charging device, where 1 is a power rectifier circuit that rectifies and smoothes an AC power source (not shown), B is a secondary battery to be charged, and this secondary battery B is, for example, a Ni-Cd battery. 2 is a voltage detection circuit that detects the voltage of the secondary battery B, and 3 is an output terminal of the voltage detection circuit 2. Further, a secondary battery B, a diode D ₁ and a main transistor Q ₁ are connected in series between the positive and negative terminals of the power supply rectifier circuit 1, and the output terminal 3 of the voltage detection circuit 2 is connected to one end of a resistor R ₁ and a diode. The resistor R 1 is connected to the connection point with the anode side of D ₂ , and the other end of the resistor R ₁ is connected to the positive side of the power rectifier circuit 1 .
The cathode side of the diode _D2 is connected to the gate of the field effect transistor _Q2 , and one side of a parallel circuit consisting of a capacitor _C and a resistor _R2 is connected to the connection point between the diode D2 and the field effect transistor _Q2 . The other side of the parallel circuit is connected to the negative side of the power rectifier circuit 1. Furthermore, the drain of the field effect transistor Q ₂ is connected to the positive side of the power rectifier circuit 1, and the source is connected to the resistor.
Connect to the base of transistor Q ₃ through R ₃ ,
In addition, the collector of the transistor _Q3 is connected to the positive side of the power rectifier circuit ₁ , and the emitter is connected to the base of the main transistor _Q1 via the resistor _R4 .
A resistor _R5 is connected between the emitters.

In the conventional circuit configuration shown in FIG _. 3 above, for example, the charging voltage at each temperature in FIG.
If voltage detection circuit 2 operates at V ₂ points and V ₃ points at 40°C, capacitor C stops charging and resists
Discharge starts from R ₂ . As a result, the gate potential of the field effect transistor _Q2 gradually decreases over time. That is, the main transistor Q ₁ gradually becomes unsaturated via the transistor Q ₃ ,
As shown in FIG. 2, the charging current I finishes gradually decreasing equivalently to I ₀ °C', I ₂₀ °C', and I ₄₀ °C' at each temperature.

However, in the conventional circuit configuration shown in FIG. 3, the charging current gradually decreasing mode shown in FIG.
t ₇ - _{t 1} = t ₅ - t ₂ = t ₈ - t ₃ , which is the result of the capacitor C and resistor of the discharge timer circuit shown in Figure 3.
Determined by the time constant of R ₂ . In this case, since the temperature dependence of the resistance value of the resistor R ₂ and the capacitance value of the capacitor C is generally negligible, the charging current gradual decrease region time at each ambient temperature is the same. Therefore, in the conventional circuit configuration shown in FIG. 3, in the charging mode shown in FIG. 2, when comparing the amount of charge at each ambient temperature from _t0 at the start of charging until the charging current I finishes gradually decreasing, , the amount of charge at 0°C < the amount of charge at 20°C < the amount of charge at 40°C. For example, if the amount of charge at 20°C is appropriate, there will be an insufficient charge at 0°C, and at 40°C, the charge amount will be insufficient. Therefore, in the case of a temperature of 40°C, it has the disadvantage that it leads to deterioration of the life of the secondary battery from the viewpoint of long-term charging and discharging cycles.

Purpose of the invention In view of the above-mentioned conventional drawbacks, the present invention eliminates the imbalance in the amount of charge at each ambient temperature, provides a simple structure for the appropriate amount of charge at each ambient temperature, and sufficiently suppresses the increase in battery internal pressure. The purpose of this invention is to provide an automatic charging device that can be secured in the same state.

Structure of the invention In order to achieve the above object, the present invention connects a capacitor and a temperature-sensitive semiconductor resistor having a negative resistance temperature characteristic in parallel via a diode to the output terminal of a voltage detection circuit that detects the voltage of a secondary battery. One end of the circuit is connected, and the other end of this parallel circuit is connected to the negative side of a power rectifier circuit, and when the voltage of the secondary battery reaches a set voltage or higher, the secondary battery is charged by a signal from the voltage detection circuit. A drive circuit is provided that discharges the electric charge of the capacitor, operates proportionally with the terminal voltage of this capacitor, and automatically controls the time during which the charging current gradually decreases depending on the temperature of the charging atmosphere, thereby gradually reducing the charging current to a minute current or less. According to this configuration, since a temperature-sensitive semiconductor resistor having a negative resistance-temperature characteristic is used, the resistance value increases when the ambient temperature is low, and as a result,
The time for the charging current to gradually decrease due to the time constant with the capacitor becomes longer, and on the other hand, when the ambient temperature is high, the resistance value becomes smaller, and as a result, the time for the charging current to gradually decrease due to the time constant with the capacitor becomes shorter. Since the amount of charge at each ambient temperature is almost the same, there is no longer a problem of overcharging or undercharging when the ambient temperature is high or low, as was the case in the past. It is possible to always ensure an appropriate amount of charge at ambient temperature.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. Note that in FIG. 4, the same parts as those in FIG. 3 showing the conventional example are given the same numbers, and only the points that are different from FIG. 3 will be explained.
That is, in one embodiment of the present invention shown in FIG. 4, instead of the conventional resistor _R2 connected in parallel with the capacitor C, a temperature-sensitive semiconductor resistor consisting of a thermistor having a negative resistance-temperature characteristic is used. It uses R ₂ ′.

The operation of the circuit configuration shown in FIG. 4 will be explained. As shown in FIG. 1, the voltage V of the secondary battery B is the set voltage of the voltage detection circuit 2, that is, the voltage at which the internal pressure of the battery starts to rise significantly, that is, 0°C V ₁
point, 20℃V ₂ points, 40℃V ₃ points or less, the potential of the output terminal 3 of the voltage detection circuit 2 becomes the same potential as the voltage of the secondary battery B, and as a result, the capacitor C is connected to the resistor R ₁ , charged through diode D ₂ and field effect transistor Q ₂ and transistor Q ₃ ,
Both _Q1 are turned on and charging of secondary battery B starts. As this charging progresses, the battery voltage V
increases and the set voltage of voltage detection circuit 2, that is, 0
When reaching ℃V ₁ point, 20℃V ₂ points, 40℃V ₃ points or less,
The potential at the output terminal 3 of the voltage detection circuit 2 drops to near zero, and the potential on the anode side of the diode _D2 becomes lower than the potential on the cathode side, so that no charging current flows through the capacitor C. As a result, the voltage across the capacitor C, that is, the gate potential of the field effect transistor Q ₂ , gradually decreases as the temperature sensitive semiconductor resistor R ₂ ' starts discharging _the capacitor C. Since the source potential of the main transistor Q 3 also decreases, the transistor Q ₃ goes from a saturated state to an unsaturated state, and the main transistor Q ₁ similarly goes from a saturated state to an unsaturated state. Therefore, in the operating mode of FIG. 1 in one embodiment of the present invention, the charging current I starts to gradually decrease as shown in FIG. That is,
When the battery internal pressure P starts to rise rapidly, the charging current I is gradually reduced to suppress the rise in the battery internal pressure P to a low level. As the capacitor C discharges further, the field effect transistor Q ₂
and transistor Q ₃ are turned off, and the main transistor Q ₁ is also turned off, completing the gradual reduction of the charging current I. However, after the completion of this gradual reduction of the charging current, the resistor R connected in parallel between the collector and emitter of the main transistor Q _{1 5} to cause a supplementary charging current to flow through the secondary battery B. Furthermore, as shown in Fig. 1, when charging is carried out with a large constant current I, the points at which the battery internal pressure P starts to rise significantly depending on the ambient temperature are, for example, _one point at 0°CV, _two points at 20°CV, 40℃V ₃ points, and the electrochemical reaction of secondary battery B during charging is also different, generally 0℃t ₁
−t ₀ <20℃t ₂ −t ₀ <40℃t ₃ −t ₀ . That is, in a low temperature range, the time at which the battery internal pressure P starts to rise significantly is early, and in a high temperature range, it is slow. For example, in the charging mode shown in FIG.
In the case of 0℃, if you set the time from the charging start time t ₀ to the charge current gradual decrease start time t ₂ , which is the same as at 20℃, and let the decreasing current flow in the same gradual decrease time as at 20℃, the battery internal pressure P will be Immediately after the charging current starts to gradually decrease, the safety valve operating pressure P _D of the secondary battery B reaches approximately. In other words, if we take into consideration the variations in the safety valve operating pressure,
Therefore, in one embodiment of the present invention, the safety valve is operated at low temperatures, for example, 0°C.
In this case, as shown in Fig. 5, the charging current gradually decreasing starting point is set as short as t ₁ , and the charging current gradually decreasing region is set as long as t ₆ - _{t 1} . , it is possible to charge 100% of the battery capacity of the secondary battery B with a gradually decreasing charging current while suppressing the rise in the battery internal pressure P to a low level like _P1 . Also, in high temperature ranges, for example 40℃,
Contrary to the low temperature range, the range from charging start point t ₀ to charging current starting point t ₃ is set long, and the charging current gradually decreasing region is set short as t ₄ - t ₃ . It is possible to charge 100% of the battery capacity of the secondary battery B with a gradually decreasing charging current while suppressing the rise in battery internal pressure to a low level as shown in _P3 . Therefore, if the total charge amount at 20°C is used as an appropriate standard, the charging current gradually decreasing region becomes longer at 0°C, and the charging current gradually decreasing region becomes shorter at 40°C. 4th example
In the charging operation mode with the configuration shown in the figure, as shown in Figure 5, the charging current is equivalently I0℃, I20
℃, I gradually decreases to 40℃, and the battery internal pressure P
are also suppressed to sufficiently low values such as P ₁ (0°C), P ₂ (20°C), and P ₃ (40°C).

Furthermore, in the configuration shown in FIG. 4, which is an example of the present invention, the charging current is gradually reduced by the main transistor Q ₁ , but the gradually decreasing time and the gradually decreasing charging current are controlled by the terminal voltage of the capacitor C using the field effect transistors Q ₂ , Resistor R ₃ , Transistor Q ₃ , Resistor R ₄
proportionally controlled by That is, let E be the voltage of capacitor C immediately before voltage detection circuit 2 operates, and let e be the gate potential of field effect transistor Q ₂ at any time when the charging current is gradually decreasing, and the time from the start to the end of gradual decrease is If T, then e=Eexp− by capacitor C and temperature-sensitive semiconductor resistor R ₂ ′.
The discharge equation of T/R ₂ 'C is established. That is, since the temperature-sensitive semiconductor resistor R ₂ ' has a negative resistance temperature characteristic, when the ambient temperature is low, for example, 0° C., the resistance value of the semiconductor resistor R ₂ ' becomes large.
As a result, the time for the charging current I to gradually decrease due to the time constant with the capacitor C becomes longer.On the other hand, when the ambient temperature is high, for example 40℃, the semiconductor resistor
The resistance value of R ₂ ' becomes smaller, and as a result, the time for the charging current I to gradually decrease due to the time constant with the capacitor C becomes shorter. t ₆ −t ₁ ＞20℃t ₅ −
The relationship t ₂ > 40°C t ₄ −t ₃ can be easily obtained. As a result, the amount of charge at each ambient temperature is approximately the same, so there is no longer a problem of overcharging or undercharging due to a change in ambient temperature as in the conventional case.

Further, a discharge circuit 4 consisting of a parallel circuit of a capacitor C and a temperature-sensitive semiconductor resistor R _{2 '} shown in FIG _.
A series circuit of C and a capacitor C are connected in parallel, and two temperature-sensitive semiconductor resistors are connected in parallel as shown in Figure 7.
A series circuit of R ₂ ′ and a resistor R ₇ is connected in parallel with a capacitor C, and a capacitor C is connected in parallel with two temperature-sensitive semiconductor resistors R ₂ ′ connected in parallel as shown in Figure 8. If this is done, it is possible to accurately set the charging current gradual reduction start point and the charging current gradual reduction region time at any ambient temperature.

Effects of the invention As described above, according to the invention, since a temperature-sensitive semiconductor resistor with a negative resistance-temperature characteristic is used, the resistance value increases when the ambient temperature is low, and as a result, the capacitor The charging current gradually decreases due to the time constant of Since the amount of charge at each temperature is almost the same, there will be no overcharging or undercharging when the ambient temperature is high or low, as was the case in the past. It is possible to always ensure an appropriate amount of charge at all times.

[Brief explanation of the drawing]

Figure 1 is a characteristic diagram showing the relationship between charging time, battery voltage, and battery internal voltage when charging current is constant. Figure 2 is a characteristic diagram showing the relationship between charging time, battery internal voltage, and battery internal voltage in a conventional automatic charging device. 3 is an electric circuit diagram of a conventional automatic charging device, FIG. 4 is an electric circuit diagram of an automatic charging device showing an embodiment of the present invention, and FIG. A characteristic diagram showing the relationship between the charging time, the internal voltage of the battery, and the charging current, and FIGS. 6, 7, and 8 are circuit diagrams showing each embodiment of the discharging circuit in the charging device. B... Secondary battery, 1... Power rectifier circuit, 2...
Voltage detection circuit, 4...discharge circuit, C...capacitor, R2 _' ...temperature-sensitive semiconductor resistor, _Q1 ...main transistor, _Q2 ...field effect transistor, _Q3 ...
Transistor, D ₂ ... Diode, R ₁ , R ₃ , R ₄
……resistance.

Claims (1)

[Scope of utility model registration request] A main circuit comprising a secondary battery to be charged and a main transistor connected in series at both ends of a power supply rectifier circuit, and a voltage detection circuit for detecting the voltage of the secondary battery, and an output terminal of the voltage detection circuit. One end of a parallel circuit of a capacitor and a temperature-sensitive semiconductor resistor having a negative resistance-temperature characteristic is connected via a diode, and the other end of this parallel circuit is connected to the negative side of the power supply rectifier circuit, and the secondary When the voltage of the battery reaches a set voltage or higher, the charged capacitor is discharged according to a signal from the voltage detection circuit, and the charging current gradually decreases depending on the charging atmosphere temperature by proportional operation according to the terminal voltage of this capacitor. An automatic charging device equipped with a drive circuit that automatically controls the time and gradually reduces the charging current to below a minute current.