JPS59201641A - Charging circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a charging circuit for a device using a battery, such as a rechargeable electric drill.

[Background technology]

As seen in Japanese Patent Application Laid-open No. 56-68230 (Japanese Patent Application No. 54-132266), conventional charging circuits are used in equipment that uses batteries, such as rechargeable electric drills, to repeatedly charge and discharge. One of the multiple batteries
One or more batteries may short circuit. If the battery is charged in this state, the charging control circuit will not operate because the battery voltage will not reach the normal level, and the overcharging will continue, causing damage to the battery or the charging circuit. If rapid charging is performed for about one hour under such conditions, there is a problem in that the battery life deteriorates.

[Purpose of the invention]

The object of the present invention is to select one of a plurality of batteries.
To prevent overcharging and damage to a charging circuit when one or more batteries are short-circuited, and to recover battery voltage in a short time without deteriorating the battery.

[Disclosure of the invention]

Embodiment In FIG. 1, (1) is a battery, and the switching element S
CR are 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
Charge control is performed by performing a rechinking operation. The charging control circuit (2) is composed of an IC. (3) is a first reference voltage generation circuit, which includes a diode D6. A predetermined reference voltage is generated using the forward voltage drop of D7, and when the battery is turned on, it is placed closely to the battery (f1) and has a temperature detection function of the battery (1), and at that time the battery +11 The temperature is such that the reference voltage varies linearly accordingly. The reference voltage obtained from the first reference voltage generation circuit (3) is amplified inside the charge control circuit (2), outputted from the terminal (2) of the charge control circuit (2), and then output via the resistor R2 and the quartz D3. Tri-powers the switching element SCR.(4) is the second reference voltage generation circuit, which is composed of a Zener diode D8, a diode 1)Ha, a diode D, and a capacitor C2, and is connected to the base of the transistor Q through a resistor R11. Connect to. The transistor Q1 is a comparison element that compares the battery voltage with the reference voltage of the second reference voltage generation circuit (4).The collector of this transistor Q1 is connected to the base of the transistor Q2 and the current limiting element R12, and the voltage of the battery +11 is connected to the collector of the transistor Q1. The 0 transistor Q2 connected to the current limiting element R13
The collector is connected to the base of Q3 through a resistor R14 and also to a resistor R17. The collector of transistor Q3 is connected to the anode of diode D3, and the collector of transistor Q3 is connected to GND. The LED is a light emitting diode that lights up while the battery il+ is being charged. In other words, the output voltage of the rectifier circuit (5) is low while battery +11 is being charged, and the output voltage of the rectifier circuit (5) is high when charging is completed. Taking advantage of this fact, the charge control circuit (2) controls this voltage change. Detected and lights up the light emitting diodes L and ED during charging. A specific example of the charging control circuit (2) is constructed as shown in FIG. 2, and the terminals 1 to 2 correspond to the terminals 2 to 2 in FIG. 1.

Operation If the voltage of the battery fi+ is lower than the reference voltage of the second reference voltage generation circuit (4), the transistor Q1 turns on, which turns on the transistor Q2, turns on the transistor Q3, and increases the gate voltage applied to the switching element SCH. In order to lower the voltage, the switching element SCR remains off and the main charging current does not flow. At this time, the base current of the transistor Q2 determined by the current limiting element 1-13 and the current determined by the current limiting element R12 flow into the battery (1) through the transistor Ql. The current in this case can be determined by resistors R12 and R13, and a necessary trickle current can be caused to flow. This trickle current causes the battery (1) to
can be recovered to a normal state if it is in an over-discharged state, but after charging, the battery voltage does not rise enough to affect on/off of the transistor Q1. The output current of the terminal (2) flows to GND by the transistor Q3 and is not related to charging of the battery (1).

When the voltage of the battery Fi1 exceeds the reference voltage of the second reference voltage generation circuit (4) due to charging by this trickle current, the transistor Q1 is turned off, and the l-transistors Q2 and Q3
is also turned off, and the output of the charging control circuit (2) becomes a voltage determined by the reference voltage of the first reference voltage generating circuit (3). The output of the charging control circuit (2) triggers the Sugi 1 soting element SCR, and the main charging current flows to charge the battery (1). Terminal ■ of the charging control circuit (2) where the voltage of the battery (tl) is determined by the reference voltage of the first reference voltage generation circuit (3)
When the output voltage reaches , the switching element SCR turns off and charging ends.

〔Effect of the invention〕

As described above, the present invention connects a current limiting element that limits the current to a comparison element that compares the battery voltage and the reference voltage of the second reference voltage generation circuit, and charges the battery with a trickle current through the current limiting element. As a result, overcharging can be prevented when one or more of the batteries are short-circuited, and
This prevents damage to the charging circuit, and also limits the current flowing through the battery to the current determined by the circuit, allowing over-discharged batteries to recover, but preventing the battery voltage from rising more than necessary. .

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of one embodiment of the present invention, and FIG. 2 is a circuit diagram of a charging control circuit according to the second embodiment. fi+...Battery, (2)...Charging control circuit, (31...
- First reference voltage generation circuit, (4)... Second reference voltage generation circuit, SCR switching element, Ql... Comparison element, R12, R13... Current limiting element. Agent Patent Attorney Ishi 1) Choshichi

Claims (1)

[Claims] A switching element connected in series to the +11'lE battery to control charging, a charging control circuit that outputs an output based on the output of the first reference voltage generating circuit and controls the switching element, and a second reference that is compared with the battery voltage. a voltage generating circuit, the charging circuit is configured to turn off the switching element and charge the battery with a trickle current when the battery voltage is lower than the reference voltage of the second reference voltage generating circuit; A charging circuit characterized in that a current limiting element for limiting current is connected to a comparison element for comparing the voltage with a reference voltage, and a battery is charged with a trickle current through the current limiting element.