JPS605134B2 - charger - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a charger that initially charges a battery with a large current at a constant current, and after the terminal voltage of the charger reaches a constant voltage, charges the battery with a constant current.

In order to charge a battery in a short time, a charger is known that charges the battery at a constant current with a relatively large current to nearly 90% of the battery capacity, and then charges at a constant voltage.

This is because constant current charging to nearly 100% of the battery capacity may cause damage to the battery due to gas generation and temperature rise. First, this type of charger will be explained with reference to the drawings.

FIG. 1 is a circuit diagram of the charger, and FIG. 3A is a graph for explaining the operation of the charger. In FIG. 1, 1 is a rectifier and smoother, and 2 is a control transistor. One input terminal of the error amplifier 4 is connected to a reference voltage point formed by a resistor 8 and a constant voltage diode 6, and the other input terminal is connected to one end of a reference resistor 10 that indicates the exposure drop with respect to the charging current. The output of the amplifier 4 is connected to the base of the transistor 3, and the emitter of the transistor 3 is connected to the base voltage of the control transistor 2. A negative feedback circuit formed by this transistor 2, resistance value 10, amplifier 4, and transistor 3 forms a circuit for constant current supply.

One input terminal is the reference voltage point formed by the resistor 10 and the voltage regulator diode 7, and the other is the output terminal 13 of the charger.
The output terminal of the error amplifier 5, which is connected to the voltage divider 12 that divides the voltage of This circuit system is configured so that it does not operate before the terminal voltage reaches a certain voltage. 11 is a diode for preventing backflow.

When charging a battery with such a charger, the variable resistor 12 is set so that when the voltage at the output terminal 13 of the electric appliance reaches the set voltage Eo of the battery, constant current charging is switched to constant voltage charging. . FIG. 3A is a graph showing charging characteristics in such a case. The voltage at the output terminal is the set voltage E
The terminal voltage of the battery 15 when the voltage reaches 0 is the value obtained by subtracting the voltage drop Δe due to the resistance of the succeeding cable 14 from Eo.

At that point, if you switch to constant voltage charging, the battery's set voltage E.
It takes quite a long time to reach that point. In FIG. 3A, the period indicated by a indicates the period of constant current charging. then b
Constant voltage charging is performed during the period indicated by , the charging current gradually decreases, and the voltage gradually increases until it reaches the set voltage Eo, and the charging ends. Complete charging cannot be achieved unless the constant voltage charging period b is considerably long. Theoretically, the voltage at terminal 13 is used to shorten the charging period.

It is conceivable that by performing constant current charging until the voltage reaches 10 (Δe, 10e2), the voltage can be charged to around 90% in a short time. However, if charging is not stopped immediately, the battery may be overcharged and damaged, so it is not generally used. An object of the present invention is to provide a charger that can charge a battery to 100% in a shorter time than a conventional constant current constant voltage charger and does not damage the battery due to overcharging. . In order to achieve the above object, the charger according to the present invention is a charger that initially charges a battery with a constant current and then charges the battery with a constant voltage from a certain point, and a resistor circuit is inserted in series with the charging current circuit of the charger. , from the voltage drop due to the charging current of the resistor circuit, detect a voltage corresponding to the voltage drop due to the known resistance inserted in the cable connecting the charger and the battery and the internal resistance of the battery, and calculate the output terminal voltage of the charger. By switching to constant voltage charging when the voltage reaches the sum of the battery's set voltage and the detected voltage, the battery is configured to be charged at a constant current with a large current at the beginning of charging, and then to be charged at a constant voltage. .

According to such a configuration, the constant current charging time can be increased and reasonable constant voltage charging can be continued, so that the object of the present invention can be completely achieved.

Next, the present invention will be explained in more detail with reference to the drawings and the like.

FIG. 2 is a circuit diagram showing an embodiment of the charger according to the present invention. Parts corresponding to the charger shown in FIG. 1 are given the same reference numerals. In the charger according to the present invention, a resistance circuit, specifically, resistors 16 and 17, is connected to the charging current circuit to compensate for the voltage drop due to the resistance of the cable connecting the charger and the battery 15 and the internal resistance of the battery. There is. The resistor 17 is a voltage divider for adjusting the voltage drop occurring across the resistor 16 to correspond to the voltage drop caused by the cable resistance and the internal resistance of the battery. One ends of the constant voltage diodes 6 and 7 are connected to a resistor 16, and the configuration is such that the reference voltage is supplied from a voltage higher than the ground level of the charger by the voltage drop caused by the resistor 16, and is used for constant voltage charging. The input voltage of the error amplifier, ie the output of the voltage divider 12, is also subject to the voltage drop across the compensation resistor.

The voltage setting for switching from constant current charging to constant voltage charging is as follows.

First, the output voltage of the voltage divider 17 is set to zero at one end, and in that state, the voltage divider 12 is adjusted so that when the voltage at the output terminal 13 becomes equal to the set voltage Eo of the battery, switching to constant voltage charging is performed.
This will be explained in more detail with reference to FIG. 3B and the like.

Measure the voltage drop Δe due to the resistance of the cable and the voltage drop Δe2 due to the internal resistance of the battery under constant current charging in the charging current characteristics shown in FIG. 3B.

Under constant current charging, the voltage E at the output terminal 13 of the charger
,, the terminal voltage E2 of the battery 15 and the open circuit voltage (current zero) E3 of the battery 15 are measured with a voltmeter, and △e,=E,
-E2, △e2=E2-E3.

Note that the voltage drops Δe, Δe2 are under constant current. When switching from constant current charging to constant voltage charging, the voltage of the output terminal 13 of the charger is set to Eo+ (△e, +△e2), and when charging is completed (charging current is zero), the terminal voltage of the battery 15 is set to the set voltage. Set it to be Eo.

Setting voltage bug.

In order to separate the voltage (△e, +△e2) that compensates for the voltage drop due to the resistance of the cable blue 4 and the internal resistance of the battery 15, the compensation voltage is set to zero (the output of the voltage divider 17 by adjusting the variable resistance). ), output terminal 1
The voltage divider 12 is adjusted so that the voltage of 3 becomes Eo. Next, the variable resistor is adjusted to add the output voltage of the voltage divider '7 to the constant voltage charging circuit, and the voltage at the output terminal 13 is set to Eo+(Δe, +Δe2).

FIG. 3B is a graph for explaining the characteristics of the charger of the above configuration.

This figure corresponds to the graph in FIG. 3A. Constant current charging is performed for a period indicated by a' until the output terminal voltage reaches Eo+ (Δe, +Δe2). When the battery is rapidly charged by constant current charging, the terminal voltage of the battery rises, reaches the terminal voltage, and is switched to constant voltage charging, the charging current gradually decreases. Therefore, since the compensation voltage decreases, the output voltage of the charger also decreases as shown in the figure, and when the charging current is zero, that is, the compensation voltage is zero, the voltage at the terminal 13 becomes the set voltage Eo of the battery, and charging ends. As is clear from a comparison between FIG. 3A and FIG. 3B, the charger according to the present invention can perform constant current charging for a longer period of time than the conventional charger, for a period c in FIG. can.

In addition, the constant voltage charging point is higher than the voltage Eo at terminal 13 and the voltage drop due to internal resistance and cable resistance, but it does not exceed Eo + △e2 from the battery's perspective, so it can be charged to 100% without unreasonable charging. The current then becomes zero and charging ends naturally.

As is clear from the above description, the charger according to the present invention can perform 100% charging in a shorter time than the conventional charger.

Moreover, the battery will not be damaged due to overcharging.
Various modifications can be made to the embodiments described in detail above within the scope of the present invention.

Although the above explanation has been made regarding charging of a single cell battery, it can also be applied to charging a battery having multiple cells connected in series.

The scope of the present invention extends to all of the claims, including such applications and modifications.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram for explaining a secondary charger, Fig. 2 is a circuit diagram showing an embodiment of the charger according to the present invention, and Fig. 3A
and FIG. 3B are graphs for explaining the operation of a conventional charger and a charger according to the present invention, respectively. 1... Rectifier smoother, 2... Control transistor, 3... Transistor, 4... Error amplifier (for constant current), 5... Error amplifier (For constant voltage), 6, 7... Constant voltage diode, 10, 16
...Resistor, 11 ...Diode, 1
2, 17... Voltage divider, 13... Output terminal,
14...Cable, 15...Battery. Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1. In a charger that initially charges a battery with a constant current and then with a constant voltage from a certain point, a resistor circuit is inserted in series with the charging current circuit of the charger, and from the voltage drop due to the charging current of the resistor circuit, the A voltage corresponding to the voltage drop due to a known resistance inserted in the cable connecting the charger and the battery and the internal resistance of the battery is detected, and the output terminal voltage of the charger reaches the sum of the battery's set voltage and the detected voltage. A charger characterized in that the battery is charged by switching to constant voltage charging when the battery is charged, so that constant current charging is performed with a large current at the initial stage of charging, and then constant voltage charging is performed to charge the battery.