JPH031900B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a charging circuit for a device that uses batteries, such as a rechargeable electric drill, and its purpose is to charge one or more of a plurality of batteries. The purpose is to prevent overcharging and damage to the charging circuit in the event of a short circuit.
Another objective is to control the optimal trickle charge required for the recovery voltage during recharging according to the characteristics and number of batteries, and to recover the battery voltage in a short time without deteriorating the battery. Yet another purpose is to enable immediate determination of battery failure.

In devices that use batteries, such as rechargeable electric drills, one or more of the batteries may become short-circuited during repeated charging and discharging. If the battery is charged in this state, the charging control circuit will not operate because the battery voltage will not reach the normal voltage due to charging, and the overcharged state will continue, causing damage to the battery or the charging circuit. If rapid charging for about one hour is performed under such conditions, there is a problem in that the battery life deteriorates.

The present invention has been made in view of this point, and will be explained in detail below with reference to Examples.

In FIG. 1, reference numeral 1 denotes a battery, and a switching element SCR is connected in series, and the switching element SCR compares the output of the charging control circuit 2 with the voltage of the battery 1 and performs a switching operation to control charging.
The charging control circuit 2 is composed of an IC. Reference numeral 3 designates a first reference voltage generation circuit, which generates a predetermined reference voltage by using the forward voltage drop of diodes D ₆ and D _7. At the same time, it is placed closely to the battery 1 and performs the temperature detection function of the battery 1. The reference voltage is changed linearly according to the temperature of the battery 1 at that time. The reference voltage obtained from this first reference voltage generation circuit 3 is amplified inside the charge control circuit 2, outputted from the terminal of the charge control circuit 2, and connected to the switching element via the resistor R ₂ and the diode D ₃ .
Trigger SCR. 4 is a second reference voltage generating circuit, which is composed of a Zener diode _D3 and a capacitor _C2 , and is connected to the base of the transistor _Q1 . The collector of transistor _Q1 is connected to the gate of switching element SCR, and the emitter is connected to battery 1. The LED is a light emitting diode that lights up while the battery 1 is being charged. That is, the output voltage of the rectifier circuit 5 is low while the battery 1 is being charged, and the output voltage of the rectifier circuit 5 is high when charging is completed.The charge control circuit 2 detects this voltage change and Light up the light emitting diode LED.
A specific example of the charging control circuit 2 is constructed as shown in FIG. 2, and the terminals .about. correspond to the terminals .about. in FIG. 1.

Now, if the voltage of battery 1 is lower than the reference voltage of second reference voltage generation circuit 4, transistor _Q1 turns on, applies the trigger voltage applied to switching element SCR to battery 1, and switching element SCR remains off. There is little main charging current flowing through the transistor Q1, and the battery is charged by a trickle current through the transistor _Q1 . Charging with this trickle current causes the voltage of the battery 1 to rise to the second level.
When the reference voltage of the reference voltage generating circuit 4 is exceeded, the transistor Q ₁ is turned off, the switching element SCR is triggered by the output of the charging control circuit 2, and the main charging current flows, so that the battery 1 is charged. battery 1
When the voltage reaches the output voltage at the terminal of the charging control circuit 2 determined by the reference voltage of the first reference voltage generating circuit 3, the switching element SCR is turned off and charging is completed.

FIG. 3 shows another embodiment of the present description, in which a transistor
The collector of Q ₁ is connected to the base of transistor Q ₂ , and when transistor Q ₁ is on, a trickle current determined by resistor R ₉ flows through transistor Q ₂ to battery 1, and transistor Q ₃ is turned on to meet the first standard. A resistor _R11 is connected in series to both ends of the generation circuit 3, and the reference voltage of the first reference voltage circuit 3 is lowered or made close to zero to stop the output of the terminal of the charging control circuit 2, and the switching element SCR is turned off. As it is, the main charging current does not flow, and the transistor
Charged by trickle current through Q ₁ and Q ₂ . When the voltage of the battery 1 exceeds the reference voltage of the second reference voltage circuit 4, the transistor Q ₁ is turned off, and the transistors Q ₂ and Q ₃ are also turned off at the same time, so that the same operation as in the embodiment shown in FIG. 1 is performed. .

In the embodiment shown in FIG. 4, the transistor Q ₄ which is turned on by the second reference voltage generation circuit 4 is replaced by the transistor Q ₁
A transistor Q ₄ is connected in series to the battery 1 through a variable resistor _{R 1} and _Q4 are turned on to charge by flowing a trickle current through each, and the main charging current at this time can be variably set by a variable resistor _RX . Therefore, the optimal trickle current required for the recovery voltage during recharging can be controlled in accordance with the characteristics and number of batteries 1.

In the embodiment shown in FIG. 5, the switching element SCR is intermittently turned on for short periods of time to perform trickle current charging, and a monostable multivibrator 6 is used to turn on the switching element SCR intermittently for short periods of time. It is prepared. In other words, battery 1
When the voltage is lower than the reference voltage of the second reference voltage generation circuit 4, the monostable multivibrator 6 is operated by turning on the transistors Q ₅ and Q ₆ , and the output of the monostable multivibrator 6 is used to generate the transistor Q _{1 .} By turning on and off the switching element SCR, which operates with the pulsating output of the rectifier circuit 5, by reducing the firing angle
The ON period of the SCR is shortened to allow a trickle current to flow through the battery 1. The period during which transistor Q ₁ is turned on at the output of monostable multivibrator 6 is t ₁ in FIG. 6, and since monostable multivibrator 6 operates using the output of rectifier circuit 5 as a power source, operates in synchronization with the pulsating output of the
Note that the time t ₁ is shorter than one cycle of pulsating output. And this switching element SCR
When the voltage of the battery 1 rises above the reference voltage of the second reference voltage generation circuit 4 due to the trickle current caused by the intermittent operation (the sixth
At time t ₀ in the figure, transistors Q ₅ and Q ₆ are turned off, monostable multivibrator 6 does not operate, and transistor Q ₁ is kept in the off state, so switching element SCR is controlled by the output of charging control circuit 2. That is, the main charging current flows to the battery 1. In the case of this embodiment, as in the above-mentioned embodiment, by charging the battery 1 with a trickle current at the initial stage of charging the battery 1, even if the battery 1 is completely discharged, an excessive amount of energy is applied to the battery 1. No charging current flows,
Therefore, there is an advantage that the life of the battery 1 is not shortened. Moreover, multiple batteries 1 to be charged
If one or more of these are shorted,
Even with trickle charging, the battery voltage will not rise above the reference voltage of the second reference voltage generation circuit 4, so in such a case, the battery 1 can be quickly charged by turning on the switching element SCR. Therefore, there is an advantage that the battery 1 and the charging circuit will not be damaged by a large current.

In Figure 7, the display device 7 is turned on when the switching element SCR is off, and the display device (light emitting diode) 7 is connected in series with the transistor Q ₇ which operates in the same way as the transistor Q ₁ . When _Q1 is on, the transistor _Q7 is turned on and the display device 7 is turned on to indicate a voltage failure of the battery 1. If the battery is a good one, the battery voltage will recover within about one minute, but if it is a defective one, it will not recover forever, so a defect in the battery 1 can be detected.

As described above, the present invention includes a switching element inserted in series between a DC power source and a battery, a first reference voltage generation circuit that generates a first reference voltage indicating completion of charging of the battery, and a first reference voltage generating circuit that generates a first reference voltage indicating completion of charging of the battery. a second reference voltage generation circuit that generates a second reference voltage lower than the voltage;
trickle current supply means for supplying a trickle current to the battery when the battery voltage is lower than a second reference voltage; and a trickle current supply means for turning on the switching element when the battery voltage is higher than the second reference voltage and lower than the first reference voltage. and a charging control circuit that charges the battery with the main charging current, and when the battery voltage is lower than the second reference voltage, the battery is charged with a trickle current, so that the battery is not completely discharged. It is possible to charge the battery with a trickle current at the initial stage of charging in a state where the battery is in a state where the battery is charged with a trickle current, which has the advantage that an excessive charging current does not flow through the battery and the battery life is not shortened. Moreover, if one or more of the batteries being charged is short-circuited, the battery voltage will not rise above the second reference voltage even with a trickle current. There is also the advantage that the battery is not rapidly charged by turning on the switching element, and therefore the battery or charging circuit will not be damaged by a large current.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of one embodiment of the present invention, FIG. 2 is a specific circuit diagram of the same charging control circuit, FIGS. 3 to 5 are circuit diagrams of another embodiment of the present invention, and FIG. This figure is a charging current waveform diagram of the embodiment shown in FIG. 5, and FIG. 7 is a circuit diagram of another embodiment of the present invention. 1...Battery, 2...Charging control circuit, 3...First
Reference voltage generation circuit, 4...second reference voltage generation circuit, 7...display device, SCR...switching element, _Q1 ...transistor.

Claims (1)

[Scope of Claims] 1. A switching element inserted in series between a DC power supply and a battery, a first reference voltage generation circuit that generates a first reference voltage indicating completion of charging of the battery, and the first reference voltage. a second reference voltage generation circuit that generates a second reference voltage lower than the second reference voltage; a trickle current supply means that supplies a trickle current to the battery when the battery voltage is lower than the second reference voltage; and a charging control circuit that turns on the switching element to charge the battery with the main charging current when the voltage is higher than the first reference voltage and lower than the first reference voltage. 2. When the battery voltage is lower than the second reference voltage, the trickle current supply means lowers the first reference voltage, turns off the switching element by the charging control circuit, and stops supplying the main charging current to the battery. A charging circuit according to claim 1, characterized in that: 3. The charging circuit according to claim 1, wherein the trickle current supply means comprises trickle current setting means for variably setting the trickle current. 4. The charging circuit according to claim 1, wherein said trickle current supply means performs trickle current charging by intermittently turning on a switching element for a short period of time. 5. The charging circuit according to claim 1, further comprising a display device that lights up when the switching element is off.