JPS63190525A - Charger - 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 (a) Field of Industrial Application The present invention relates to a charging device for charging a secondary battery such as a nickel-cadmium battery used in a rechargeable electric shaver or the like.

(b) Prior art A conventional example of a charging device that detects the slope of the charging time-battery voltage characteristic curve of a secondary battery and terminates charging based on a change in this slope is disclosed in Japanese Patent Application Laid-open No. 103544/1983. Kaisho 5
4-158641, JP-A-56-25340, etc.

JP-A-53-103544 discloses a charging device that supplies a constant current to a storage battery through a switch to charge the storage battery. is held in a holding circuit, the output voltage of the holding circuit is compared with the terminal voltage of the storage battery, and when it is detected that the terminal voltage has become lower than the output voltage of the holding circuit, the switch is turned off. In addition, in Japanese Patent Application Laid-Open No. 54-158641, electrical energy is supplied to the battery for charging, battery characteristics that change depending on the charging state of the battery are monitored, and the charging is completed over time. The system analyzes the changes in the above-mentioned characteristics with respect to the change, confirms the occurrence of at least a negative inflection point during the above-mentioned changes, and controls the energy supply to the battery based on the above-mentioned occurrence. Publication No. 25340 discloses a detection circuit that detects and stores a proportional high voltage of the charging voltage of a battery to be charged, a storage circuit that stores a proportional low voltage of the maximum voltage of the charging voltage, and a detection circuit that decreases after the maximum voltage. a control circuit that detects a predetermined voltage difference between the output voltage of the battery and the storage voltage of the storage circuit to stop charging the battery; and a holding circuit that maintains the output voltage and the storage voltage in a constant relationship after stopping charging of the battery. It is equipped with

By the way, in JP-A-53-1.03544 and JP-A-54-158641, changes in battery voltage over a predetermined period of time are detected when detecting the peak point or inflection point of a characteristic curve. . However, with a normal charging device, it is impossible to detect minute voltage changes, and there is a limit to the detection accuracy at the end of charging.

Furthermore, in Japanese Patent Application Laid-Open No. 56-25340, when the maximum value of the battery voltage is memorized by a voltage storage element and charging is stopped when the battery voltage becomes a certain value lower than the maximum value, a large current is supplied to the battery. If charging is terminated in a short period of time, the problem arises that the battery may become overcharged, resulting in deterioration or damage.

(c) Problem to be solved by the present invention The problem to be solved by the present invention is that it is possible to accurately detect the end point of battery charging, and is particularly related to the magnitude of the charging Tt'Wl flow and the number of batteries to be charged. Always near the maximum voltage of the charging time-battery voltage characteristic curve! This is to stop charging the battery.

(d) Means for solving the problem In a charging device that detects the slope of the charging time-battery voltage characteristic curve of a secondary battery and terminates charging based on a change in this slope, the battery voltage is determined based on the previous slope detection. The slope is detected by counting the time required for the voltage to rise to a predetermined value from a certain point in time at minute time intervals.

(E) The time from the time of the previous detection to the time when the working battery voltage increases to the time when the voltage becomes higher by a predetermined value is recorded by counting and displaying force, nonta, etc. By comparing these counts, the slope between any two points on the battery charging time-battery voltage characteristic curve can be determined.

(F) Embodiment The charging device of the present invention will be explained in detail below according to an embodiment of the drawings.

FIG. 2 shows a schematic diagram of the circuit. (1) is 8 pits (bit
) is a microcomputer, (2) is a ladder resistance circuit,
(3) is a charging tfA that outputs DC current, and (4) is the output of the charging type vR (3) and the ladder resistance circuit (2).
), and (5) is a nickel-cadmium battery charged by the charging 1vR (3). The ladder resistance circuit (2) includes a plurality of resistors (2R) connected to the output terminals of each bit from 2 to 7 of the microcomputer (1), and each resistor (2R).
) consists of multiple resistors (R) bridging between bit
One resistor (2R) of fi is grounded. Further, the output terminal of the comparator (4) is connected to the input terminal (IN) of the microcomputer (1), and the output terminal (OUT> of the microcomputer (1) is connected to the charging type!<3). has been done.

The resistance circuit (2) is connected to the microcomputer (1).
The analog voltage value corresponding to the digital value outputted from each output bit of is outputted to the non-inverting input terminal of the comparator (4) with an accuracy of 256 (-2') steps. In this way, the ladder resistance circuit (2) and the comparator 4
) by configuring an A/D conversion circuit, it is possible to detect the voltage of the battery (5) as a digital value.

When the battery (5) is fully charged, the microcomputer (1) outputs a control signal from its output terminal (OUT) to control the charging power source (3) to charge the battery (5).
The current supply is stopped when charging 1.

Next, we will discuss the operation of the above circuit, especially the microcomputer (1).
About the operation of 1st v1! This will be explained based on the flow chart of J and the charging time-battery voltage characteristic diagram of FIG.

Time T in FIG. Assume that charging of the battery (5) is started at . The microcomputer (1) first clears the register R6 that records the current count number, and also clears the register R6 that records the current count number.
The registers R+ and R2, which store the previous count value, are initialized to a number sufficiently large for the maximum possible count value (not shown in the figure), and at the same time as this initialization, the time T. The value E0 of the battery voltage at is recorded with E being 1.

Every time a certain sampling time Ts elapses (Ts elapses, the register R6 is counted up (Ro
+ 1-Ro)* Also, it is determined whether the value of register R0 is equal to twice the previous count value R1, and R
When 0≧2R+, stop charging. If R0≧2
If it does not become R+, it is further determined whether the value of register R0 is equal to twice the count value R2 two times before,
When R0≧2R2, charging is stopped. R0≧2R2
If this is not the case, the recorded value E 艷1 of the voltage of one battery is compared with the voltage En after the elapse of the Ts time, and if the difference is not ΔE, the next sampling time Ts is executed. This operation is based on the battery voltage memory value E%-1 and the voltage/I! at each sampling time. ! Voltage En
The process continues until the difference between En-E and satisfies 1≧ΔE. At time T1, El −EO−”ΔE, and E
When n-ETl-1≧ΔE is satisfied, the value of register R0 at that time is rewritten to R1, the value of register R1 is rewritten to R2, register R0 is set to Z and cleared, and the battery voltage value En is recorded as gv+, Start sampling again. Then, the above series of operations is performed until the value of register R0 is 1.
This continues until the value of register R1 reaches twice the previous value or twice the value of register R2 two times before.

In the characteristic diagram of FIG. 3, the battery voltage E. -R5 has an interval of ΔE (V), and the charging time T0 to T6 is battery 1!
Indicates the time when the pressure increases by 8E (V), and the count number N
0 to Ns indicate the number of counts in the register R6 required to increase by ΔE(V), respectively. For example, charging time 1
Between 0 and 11, Ts waiting time sampling is performed N0 times as shown in FIG.
, Ts - Te as shown in FIG.
．． It has been performed N4°NS times. Here, when comparing the magnitude of N1-N3, the slope of the battery voltage characteristic curve (6) gradually increases until time Te (i.e., the number of counts decreases).
Since the slope becomes smaller after time T5 (that is, the number of counts increases), (a) N3 (2N2, N3 <2N+(b) N
4<2N3, N4<2N2 (one) Ns ≧2N! , NS <2N3. That is, at time T8, the count number NS at that time
becomes twice the previous count number N, and charging stops.

This means that the slope of the battery voltage characteristics, which had been large up to a certain point, becomes smaller (the count number increases) after that point. It is detected by the change in the number, and suggests that charging should be terminated when the slope becomes sufficiently late after the maximum value of the battery voltage characteristic.

(G) Effects of the Invention As described above, the present invention provides a charging device that detects the slope of the charging time-battery voltage characteristic curve of a secondary battery and terminates charging based on a change in the slope. By detecting the slope by counting the time required for the voltage to rise from the previous slope detection point to a predetermined voltage at minute time intervals, it is possible to accurately detect the slope regardless of the magnitude of the charging current or the number of batteries being charged. It is possible to detect the charging end state. Moreover, compared to the conventional method of determining the slope based on the rise in battery voltage per predetermined time, counting the time required for a constant voltage (ΔEV) to rise improves the accuracy of slope measurement by making this counting period as minute as possible. It is possible to increase it easily.

[Brief explanation of the drawing]

FIG. 1 is a flowchart showing the operation of the charging device of the present invention, FIG. 2 is an implementation circuit diagram, FIG. 3 is a charging time-battery voltage characteristic diagram, and FIGS. 4 and 5 are the same as those shown in FIG. It is an enlarged view of the main part. (5)...Battery, (6)...Charging time-battery voltage characteristic curve, (ΔE)...Predetermined voltage, (RO)(R1)(
R2)... Count value.

Claims (1)

[Claims] (1) In a charging device that detects the slope of the charging time-battery voltage characteristic curve of a secondary battery and terminates charging based on a change in this slope, even if the battery voltage increases by a predetermined voltage from the time of the previous slope detection, A charging device characterized in that the slope is detected by counting the time required at minute time intervals.