JP2576148B2 - Battery charger - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The battery charger of the present invention will be described according to the following items.

A. Industrial application fields B. Summary of the invention C. Prior art D. Problems to be solved by the invention E. Means for solving the problems F. Embodiment F-1. First embodiment [ Fig. 1] a. Circuit [Fig. 1] b. Operation F-2. Second Embodiment a. Circuit [Fig. 3] b. Operation G. Effects of the Invention (A. Field of Industrial Application) The invention relates to a novel battery charging device. In detail, the charging target is not limited to sealed nickel-cadmium storage batteries, it can also handle differences in the ratio of charging current to cell capacity, battery characteristics, etc., and charges when the secondary battery reaches the rated voltage. It is an object of the present invention to provide a new battery charger that can be terminated.

(B. Summary of the Invention) The battery charger of the present invention obtains a time change rate of a terminal voltage of a secondary battery, codes the time change rate of the terminal voltage, and codes a set value for determining a charging condition. Since the two cords are compared and the charging current to the secondary battery is controlled according to the comparison result, the charging condition can be appropriately set, and the charging target is not limited to the sealed nickel-cadmium battery. And the ratio of charging current to cell capacity,
It is possible to perform appropriate charging corresponding to differences in battery characteristics and the like.

(C. Prior Art) Conventionally, in the case of rapidly charging a nickel-cadmium storage battery, as a method of detecting the end of charging, the electric energy used for charging the battery in the initial and middle stages of charging is used in the electrolysis at the end of charging. Consumed in the electrolysis of the liquid,
There is known a method of detecting the end of charging by utilizing the fact that the terminal voltage of a battery drops by a certain voltage from its maximum value in order to increase the temperature inside the battery.

In FIG. 2, a charging curve a shown by a solid line is obtained when the secondary battery is charged by the above-described method.

In the figure, the vertical axis represents the terminal voltage of the secondary battery, and the horizontal axis represents time.

When charging a secondary battery by such a method,
As shown by the charging curve a, the terminal voltage reaches the maximum value _Em (V) at the time t _i (minute) and then gradually decreases, and the terminal voltage at the time t _{i + 1} (minute) becomes E _{i + 1} ( V).

Then, the terminal voltage E _{i + 1} (V) at this time and the maximum value E
_When the difference from Δm (V) −ΔV = E _{i + 1} −E _m reaches a predetermined voltage value, charging is terminated and overcharging is prevented.

(D. Problems to be Solved by the Invention) However, in the battery charger described above, the charging target is limited to a sealed nickel-cadmium storage battery,
In addition, it is not possible to cope with the difference in the ratio of the charging current to the cell capacity, the characteristics of the battery, and the like, so that the versatility is poor.

In such a case, charging may be performed by setting a charging end time in advance using a timer or the like.However, for a battery that has been charged to some extent, or that has become old or deteriorated due to use, the timer setting time may be different. Therefore, there is a problem that the setting is extremely difficult and the utility is poor, and if the time setting is incorrect, the battery is overcharged.

(E. Means for Solving the Problems) In order to solve the above-described problems, the battery charger of the present invention encodes a setting unit for determining a charging condition and a place set by the setting unit. A table, a differential coefficient detection circuit for detecting the terminal voltage of the secondary battery and calculating the time change rate of the terminal voltage, a digital encoder for coding the time change rate of the terminal voltage, and comparing the data of the table and the digital encoder And a switching means for controlling power supply to the secondary battery according to the comparison result.

Therefore, in the battery charger of the present invention, the charging conditions can be appropriately set, so that the charging target is not limited to the sealed nickel-cadmium battery, the ratio of the charging current to the cell capacity, the characteristics of the battery, and the like. Thus, it is possible to perform appropriate charging corresponding to the difference.

(F. Embodiment) Hereinafter, the details of the battery charger of the present invention will be described in accordance with each embodiment shown in the attached drawings.

(F-1. First Embodiment) [FIG. 1] FIG. 1 shows a first embodiment of the battery charger of the present invention.

(A. Circuit) [FIG. 1] 1 is a circuit.

Reference numeral 2 denotes a power supply line for charging, which is connected to the positive electrode side of the secondary battery 5 via the changeover switch 3 and the diode 4.

Reference numeral 6 denotes a control unit, which includes a differential coefficient detection circuit 7, a digital encoder 8, a comparator 9, and a conversion table 10, and can be easily configured by, for example, software processing by a microcomputer.

The differential coefficient detection circuit 7 has an input terminal connected between the diode 4 and the secondary battery 5, and detects a time change rate (differential value) of the terminal voltage of the secondary battery 5;
For example, it can be detected by sending two gate pulses slightly out of phase to each sample and hold circuit, comprising two sample and hold circuits and a comparator, and taking out the two outputs as a difference output by the comparator. it can.

The input terminal of the digital encoder 8 is connected to the output terminal of the differential coefficient detection circuit 7.
Means for A / D converting the output value (differential value) from the digital signal into a digital signal and converting the digital signal into a predetermined binary code.

Reference numeral 9 denotes a comparator whose input terminal is connected to the digital encoder 8 and the output terminal of the conversion table 10, respectively, and whose output terminal is connected to the changeover switch 3. Then, the binary code sent from the digital encoder 8 and the conversion table 10 are compared and calculated, and the switching operation of the changeover switch 3 is controlled according to the result.

Reference numeral 11 denotes a setting unit including a variable resistor 12, and the setting unit 11
Has an input terminal connected to the control circuit power supply line 13, and an output terminal connected to the conversion table 10. The conversion table 10 A / D converts a predetermined voltage value set by the variable resistor 12 into a digital signal, and converts the digital signal into a predetermined binary code.

Adjusting the set voltage by the variable resistor 12 enables application to a secondary battery having various characteristics.

(B. Operation) Hereinafter, the circuit operation of the first embodiment of the battery charger of the present invention will be described with reference to FIG. 1 and Table 1 below.

Table 1 shows the set voltage V _R (V) set by the variable resistor 12, and
The binary code and the output voltage ΔV /
It is a table ^| surface which shows a correspondence relationship with (DELTA) t ( ^mv / _min ). And
The correspondence between the set voltage V _R (V) set by the variable resistor 12 and the binary code is stored in the conversion table 10 in advance, and the output voltage ΔV / Δt ( ^mv
/ _min ) and the binary code are used at the time of conversion processing from a digital signal to a binary code in the digital encoder 8.

Thus, the circuit operation of setting the set voltage V _R of the variable resistor 12 to 1 (V) is as follows.

When charging is started, first, a signal from the comparator 9 is sent to the changeover switch 3, the changeover switch 3 is closed, and a charging voltage is applied to the secondary battery 5.

Then, as the terminal voltage of the secondary battery 5 increases, the time change rate (differential value) of the terminal voltage is sent from the differential coefficient detection circuit 7 to the comparator 9 via the digital encoder 8 as a binary code.

The binary code output from the digital encoder 8 is compared with a binary code 010 corresponding to V _R = 1 (V) in the conversion table 10. If the binary code does not match, a signal from the comparator 9 for setting the changeover switch 3 to the "closed" state. Is transmitted, and the power supply to the secondary battery 5 is continued as it is.

Then, when the two binary codes match, that is, when the differential value ΔV / Δt = −10 ( ^mv / _min ) and the binary code becomes 010 (point B (point B of the charging curve a in FIG. 2) t _{i + 1} ), a signal for turning the changeover switch 3 to the “open” state is transmitted from the comparator 9, the power supply to the secondary battery 5 is stopped, and the charging ends.

The secondary battery having different charging characteristics, for example, a secondary battery having a charge curve 14, as shown by the dashed line in Figure 2 shows the maximum voltage E _m at the point A (time t), then the constant It indicates the voltage value, the voltage change rate is 0 ( ^mv / _min ), and when charging such a secondary battery, the set voltage V _R = 2
If (V) is set, charging can be terminated when the voltage change stops.

Further, when charging a secondary battery having charging characteristics as indicated by a two-dot chain line, the charging curve 15 has a steep slope C.
It is necessary to terminate charging at a point (differential value ΔV / Δt = −20 ( ^mv / _min )), and it is sufficient to set V _R = 4 (V).

It is possible to apply to the secondary battery having various charging characteristics by providing means for associating this way the set voltage V _R and the secondary battery changing rate [Delta] V / Delta] t of the terminal voltage of.

(F-2. Second Embodiment) FIG. 3 shows a second embodiment 1A of the battery charger of the present invention.

Incidentally, when the battery charging apparatus 1A shown in this second embodiment is different from the battery charging device 1 shown in the first embodiment, the set voltage V _R by determining the type of battery to be charged Therefore, only the different parts will be described, and the parts which are not different will be given the same reference numerals as those used in the first embodiment for the same parts. Description is omitted.

(A. Circuit) [FIG. 3] Reference numeral 16 denotes a battery detection unit, which is provided with means for detecting characteristics such as the shape and size of the battery when the battery is inserted.

The control unit 6A includes, in addition to the control unit 6 of the first embodiment,
A type discriminating circuit 17 is provided. The input terminal of the type discriminating circuit 17 is connected to the output terminal of the battery detecting section 16 so as to discriminate the type of the secondary battery to be charged.

Reference numeral 18 denotes a setting unit including a setting voltage switch 19,
The set voltage changeover switch 19 has one fixed contact, a plurality of changeover contacts, and a mover for connecting both contacts, and the changeover contact is connected to each part of the tap resistor 20, respectively. One of the switching contacts is selectively connected. The setting unit 18 is connected to the battery type discriminating circuit 17 and the conversion table 10, and the setting voltage changeover switch 19 of the setting unit 18 operates its movable element according to the command signal of the battery type discriminating circuit 17, and one switching contact And makes a connection with the fixed contact, and a set voltage corresponding to the one switching contact is input to the conversion table 10.

(B. Operation) Thus, in the second embodiment 1A of the battery charger of the present invention, the type of the battery is specified by the signal from the battery detector 16 being input to the type determination circuit 17, The mover of the setting voltage changeover switch 19 is switched accordingly,
Charging according to the charging characteristics of the battery is performed.

(G. Effects of the Invention) As is apparent from the above description, the battery charging apparatus of the present invention includes a setting unit for determining a charging condition, a table for coding the setting values by the setting unit, and a secondary battery. A differential coefficient detecting circuit for detecting the terminal voltage of the terminal voltage, and calculating a time change rate of the terminal voltage; a digital encoder for encoding the time change rate of the terminal voltage; a comparator for comparing data of the table and the digital encoder; Switching means for controlling power supply to the secondary battery according to the comparison result.

Therefore, according to the battery charging device of the present invention, the charging conditions can be set according to the charging target, so that the charging target is not limited to the sealed nickel-cadmium battery, and the ratio of the charging current to the cell capacity, the characteristics of the battery, etc. Can be charged corresponding to the difference, and overcharge of the secondary battery can be prevented.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a first embodiment of the battery charger of the present invention, FIG. 2 is a graph showing charging characteristics of a secondary battery, and a charge curve diagram. FIG. 3 is a second diagram of the battery charger of the present invention. FIG. 3 is a circuit diagram showing an example of the embodiment. DESCRIPTION OF SYMBOLS 1 ... Battery charger, 3 ... Switching means, 5 ...
Rechargeable battery, 7 ... differential coefficient detection circuit, 8 ... digital encoder, 9 ... comparator, 10 ... table, 11 ...
… Setting section, 1A …… Battery charger, 18 …… Setting section

Claims (1)

(57) [Claims] 1. A setting unit for determining a charging condition, a table for coding a set value by the setting unit, a differential coefficient detection circuit for detecting a terminal voltage of a secondary battery and obtaining a time change rate of the terminal voltage And a digital encoder for coding the rate of change of the terminal voltage with time, a comparator for comparing the data of the table and the data of the digital encoder, and switching means for controlling power supply to the secondary battery according to the comparison result. Battery charging device characterized by the following