JPH0236733A - Battery charger - Google Patents

Abstract

PURPOSE:To start a constant current circuit in a short time by starting the constant current circuit with a portion of the output current from a charge control circuit when an over discharge battery is charged. CONSTITUTION:The out of a constant current circuit 7 for feeding a constant charge current from a DC input voltage source to a battery 10 is connected with the output of a charge control circuit 13 for turning the output of the constant current circuit 7 ON/OFF through a diode 14 and a resistor 15 arranged in series. When a over discharged battery 10 is charged, a portion of the output current from the charge control circuit 13 flows into the diode 14 and the resistor 15 and the remaining current flows into the constant current circuit 7. Consequently, the diode 14 is biased reversely and the constant current circuit 7 is started in a short time.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to a battery charging device.

(Prior Art) As a conventional battery charging device, there is one shown in FIG. 2, for example.

In this battery charging device, a terminal 1 is connected to the emitter of a transistor 2 via a resistor 3. The base of transistor 2 is connected to the collector of transistor 4, and the emitter of transistor 4 is grounded via resistor 5. Furthermore, a resistor 6 is connected between the terminal 1 and the base of the transistor 2.

A constant current circuit 7 is composed of the transistor 2, the transistor 4, the resistor 3, the resistor 5, and the resistor 6.

Transistor 4 turns on when a current is input to its base, and when transistor 4 turns on, transistor 2 turns on.

The collector of the transistor 2 is connected to the anode side of the diode 9 via the charging current supply line 8, and the cathode side of the diode 9 is connected to the battery 10. Constant current circuit 7 charges battery 10 via charging current supply line 8 and diode 9.

The base of the transistor 4 is connected to the Nandts gate 12 via the resistor 11, and the Nandts gate 12 is connected to the charging control circuit 1.
3.

When the inputs S1 and S2 of the Nant gate 12 are both LOW, the output S3 becomes HIGH. The Nant gate 12 turns the transistor 4 on and off by setting the output S3 to H1gh level and Low level,
Controls the output of constant current circuit 1.

Next, the operation of this battery charging circuit will be explained.

A DC input current fin is given to the constant current circuit 7, and the human control power SL and s2 of the charging control circuit 13 are both Low.
When it is confirmed that the charging conditions for the battery 10 are satisfied, the output S3 of the charging control circuit 13 goes High.
h level. When the output S3 becomes High level,
The transistor 4 of the constant current circuit 7 is turned on, and furthermore,
Transistor 2 is turned on, and charging current is supplied from constant current circuit 7 to battery 10 via charging current supply line 8 and diode 9.

By the way, in this battery charging device, even if a short circuit to ground occurs somewhere between the output terminal of the constant current circuit 7 and the cathode of the diode 9, the transistor 2 continues to supply the same current as in the normal state. The loss in is as follows.

Normal loss P1=(Vln −R311n −VF9
-VB) 11n abnormality loss R2-(Vin -R31
in) 11nVin; input voltage! in
;Input current R3, resistance value VF6 of resistor 3;Diode voltage vB of diode 9;Battery voltage, that is, in abnormality, PL -R2-(VP9
VB) fin loss increases. Therefore, in order to prevent damage to transistor 2 in the event of an abnormality such as a short circuit accident, it is necessary to use a transistor with a power dissipation that can withstand the increase in loss in the event of an abnormality, which is a problem that goes against cost and energy savings. .

To solve this problem, a battery charging device was devised in which the output of the charging control circuit 13 and the output of the constant current circuit 7 are connected via a diode 14, as shown in FIG.

In this battery charging device, in the event of a short circuit, the output of the charging control circuit 13 is bypassed via the diode 14 and is supplied to the charging current supply line 8, so the transistor 4 and the transistor 2 are turned off, and the loss of the transistor 2 is zero. becomes. At this time, the charging control circuit 13 is connected to the diode 14.
Only a very small current, limited within and by resistor 11, flows.

However, in the battery charging device shown in FIG. 3, if it is left unused for a long period of time, it will over-discharge, and the open circuit voltage will change from the voltage at point a to the forward voltage of diode 9 and diode 14 (VF
When attempting to charge the battery 10 whose voltage is lower than the voltage obtained by subtracting 9+VF14), the charging control circuit 13
The output current from battery 1 passes through diode 14.9.
Since the current flows to 0, the constant current circuit 7 cannot be activated.

Note that due to the minute current passing through the diode 14, the battery 1
0 is gradually charged, and eventually the diode 14 becomes reverse biased, so that the transistors 4 and 2
is turned on and the constant current circuit 7 is activated, but generally the current flowing via the diode 14 is approximately 1 of the charging current.
Since the current is about 150 to 1/100, the battery 10 is charged with the current passing through the diode 14, and eventually the constant current circuit 7
It is not practical for this to start.

(Problems to be Solved by the Invention) As described above, the conventional battery charging device has a problem in that the constant current circuit does not start up in a short time when charging an over-discharged battery.

The present invention has been made in view of the above problems, and an object thereof is to provide a battery charging device in which a constant current circuit is activated in a short time when charging an over-discharged battery.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention provides a constant current circuit that supplies a constant charging current to a battery from a DC input voltage, and an output of the constant current circuit. The present invention is characterized in that it includes a charging control circuit that turns on and off, and a diode and a resistor provided in series between the output of the constant current circuit and the output of the charging control circuit.

(Function) In the present invention, the output of the constant current circuit that supplies a constant charging current to the battery from the DC input voltage and the output of the charging control circuit that turns on and off the output of the constant current circuit are connected in series. By connecting the diode and the resistor, when charging an over-discharged battery, part of the output current of the charging control circuit flows into the diode and the resistor, and the remaining current is input to the constant current circuit. The constant current circuit starts charging the battery with a current lower than normal, and in a short time the diode is reverse biased and the constant current circuit starts up. Therefore, when charging an over-discharged battery, the constant current circuit is activated in a short time.

(Example) Hereinafter, an example of the present invention will be described in detail based on the drawings.

FIG. 1 is a circuit diagram of a battery charging device according to an embodiment of the present invention.

In FIG. 1, elements that perform the same functions as those of the battery charging device shown in FIGS. 2 and 3 are given the same numbers to avoid redundant explanation.

In this embodiment, in the battery charging circuit shown in FIG. 2, a diode 14 and a resistor 15 as a resistance applying section are connected in series between the output of the constant current circuit 7 and the output of the electric control circuit 13.

Next, the operation of the battery charging device of this embodiment will be explained.

First, a normal state, that is, a state in which there is no short circuit in the charging current supply line 8 and the battery 10 is not over-discharged, will be described. DC human power 11n is given to the constant current circuit 7, and the charging control circuit 1
When it is confirmed that the inputs S1 and S2, which are the control inputs of the charging control circuit 13, become Low level and that the charging conditions for the battery 10 are satisfied, the output S3 of the charging control circuit 13 becomes High level, and a current is output. Since the voltage of battery 10 is high and reverse biases diode 14, diode 1
4. The output current from the charging control circuit 13 does not flow into the resistor 15. Therefore, when a current is output from the charging control circuit 13, the transistor 4 of the constant current circuit 7 is turned on, and the transistor 2 is also turned on, so that the charging current from the constant current circuit 7 flows through the charging current supply line 8 and the diode 9. It is supplied to the battery 10 via the battery 10.

Next, when a short circuit occurs in the charging current supply line, a part of the output current of the charging control circuit 13 flows into the ground from the short circuit point via the diode 14 and the resistor 15.

Therefore, the output current of the remaining charging control circuit 13 flows into the transistor 4 of the constant current circuit 7, so the base current of the transistor 4 is less than normal, and therefore the collector current of the transistor 2 is also reduced, and the power of the transistor 2 is reduced. Losses will be equal to or lower than normal. The degree to which the base current of the transistor 4 decreases is roughly determined by the relationship between the resistance values of the resistors 5, 11, and 15.

Also, if the battery is left unused for a long period of time, it may over-discharge and the open circuit voltage may drop to a.
When charging the battery 10 whose voltage is lower than the voltage obtained by subtracting the forward voltage (VP9+VP14) of the diode 9 and the diode 14 from the voltage at the point, it is assumed that there is a short circuit on the apparent main charging current supply line 8, so charging is stopped. Control circuit 1
A part of the output current of No. 3 flows into the battery 10 via the diode 14 and the resistor 15. Since the output current of the remaining charging control circuit 13 flows into the transistor 4 of the constant current circuit 7, transistors 4 and 2 are turned on, and the constant current circuit 7 stops charging the battery 10 even if the current is lower than normal. Start. Therefore, in a relatively short period of time, the battery voltage rises to reverse bias the diode 14, after which the transistor 4 can supply the normal charging current to the battery.

Thus, in this embodiment, when charging the over-discharged battery 10, the constant current circuit 7 starts charging the battery 10 even if the current is lower than normal, so the constant current circuit 7 is activated in a short time.

[Effects of the Invention] As described above, according to the present invention, it is possible to provide a battery charging device in which a constant current circuit is activated in a short time when charging an over-discharged battery.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a battery charging device according to an embodiment of the present invention, and FIGS. 2 and 3 are circuit diagrams of a conventional battery charging device. 7... Constant current circuit, 10... Battery, 13... Charging control circuit, 14... Diode, 15... Resistor 1 Figure 2 Figure 2

Claims (1)

[Scope of Claims] A constant current circuit that supplies a constant charging current to a battery from a DC input voltage, a charging control circuit that turns on and off the output of the constant current circuit, and an output of the constant current circuit and the charging control. A battery charging device characterized by comprising a diode and a resistance applying section provided in series between outputs of a circuit.