JPH06335175A - Charger - Google Patents

Abstract

PURPOSE:To avoid the misdetection in a charger which stops charging when a battery is fully charged. CONSTITUTION:A battery voltage (VN) B6 is detected every ceratain period and compared with a maximum voltage (VPEAK) D1 before that period. If VN VPEAK, a counter is made forward by (n) (n>=2) steps, If VN=VPEAK, the counter is made forward by one step. If VN>VPEAK, the counter is cleared to zero. With this constitution, even if a power supply voltage fluctuates, the counter is made forward quickly after the battery voltage reaches the maximum value and the charging is stopped at the timing close to a full charge state.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to a charging device for a cadmium battery or the like.

[0002]

2. Description of the Related Art When a battery is charged, the battery voltage rises until it reaches a fully charged state, and if it continues to be charged after the full charge, the battery voltage falls. That is, the battery voltage becomes maximum in the fully charged state. Various techniques have been proposed that utilize this phenomenon to stop charging at the timing when the battery voltage becomes maximum.

For example, Japanese Unexamined Patent Publication No. 63-234844 discloses a technique of detecting a battery voltage every predetermined period and stopping charging when it is continuously found that the voltage has dropped a predetermined number of times or more. Has been done. According to this, the charging is stopped immediately after the full charge. FIG. 1B shows the details of this procedure. In step B1, the last battery voltage (V
0) and the battery voltage (VN) of this time are compared. When the latter is larger than the former, the counter is cleared to zero (B3),
On the other hand, when the latter is equal to or smaller than the former, the counter is set to 1.
Step forward (B2). When the count value of the counter reaches a predetermined value, step B4 becomes YES and the charging is stopped (B5). While the predetermined number of times is not reached, the processing after B1 is repeated every predetermined period. Step B6 replaces the previous battery voltage (V0) with the current battery voltage (VN). According to this technique, as shown in FIG. 1 (A), the counter advances when the battery voltage reaches the maximum, and the charging is stopped when the battery voltage starts to decrease continuously. In addition, ΔV in the figure indicates VN-VO, and
Is greater than the detected value this time, = is equal, −
Indicates that the detected value this time is smaller.

[0004]

[Problems to be Solved by the Invention]
A large motor may be turned on and off near the charging device, and the power supply voltage tends to fluctuate. Therefore,
The battery voltage as shown by the black dot in (C) may be detected. When the power supply voltage fluctuates irregularly or periodically in this way, the previous detection value and the current detection value fluctuate, and although the overall battery voltage is in the falling period, the current detection value is sometimes the previous value. It may be larger than the detected value, and when such a phenomenon occurs, the counter is cleared to zero each time. As a result, the stepping of the counter is delayed, and the charging may not be stopped unless the charging is continued for a considerable period after the battery is fully charged. If charging is continued even after full charge, the battery life will be shortened. Therefore, in the present invention, it is possible to more stably detect the timing close to the full charge timing.

[0005]

To this end, according to the present invention, there is provided a device for charging a battery by supplying a charging current to the battery and detecting the battery voltage at every predetermined period during charging. A device for extracting and storing the maximum voltage among the battery voltages, a counter that compares the detected battery voltage with the maximum voltage, and advances when the former is equal to or smaller than the latter, and a counter of the counter. A charging device having a device for stopping energization of a charging current when the count value becomes equal to or more than a predetermined value is created (corresponding to claim 1). The counter advances one step when a battery voltage equal to the maximum voltage is detected, and advances n (where n is an integer of 2 or more) when a battery voltage smaller than the maximum voltage is detected. It is desirable (corresponding to claim 2).

[0006]

[Operation] As shown in FIG. 1 (D), the detected value (VN) at this time
Is not the previously detected value (VO), but is compared with the maximum voltage (VPEAK) up to that point, even if the power supply voltage fluctuates slightly, the V
PEAK ≧ VN, and the counter continues to increment. That is, even if VN> V0 happens to happen, the counter is not cleared to zero, and the counter advances as long as VPEAK ≧ VN. For this reason, after the battery voltage reaches its maximum, the counter rapidly advances to reach a predetermined value. In this way, it is prevented that the charging is continued for a considerable period even after the battery is fully charged (corresponding to claim 1). In addition, when VN = VPEAK
When a counter that advances by two or more when VN <VPEAK is used, the counter advances rapidly after full charge and charging is stopped at a timing closer to full charge (corresponding to claim 2).

[0007]

FIG. 3 shows the system configuration of an example of a charging device embodying the present invention. The current supplied from the commercial power source 2 is rectified by the rectifying / smoothing circuit 4 and then smoothed, and the switching element 6 controls ON / OFF. The transformer 8 steps down the commercial voltage and supplies the charging current to the secondary side.
This current is rectified by the rectifying / smoothing circuit 9, smoothed, and then supplied to the battery 10. The battery 10 contains a plurality of 1.2 volt rated cells, a 7.2 volt rated battery containing 6 cells, a 9.6 volt rated battery containing 8 cells and a 10 rated rating of 12 cells. Any of the 0.0 volt batteries are used.

A charging current detection circuit 12 and a battery voltage detection circuit 14 are attached to the secondary side circuit. Further, a temperature sensitive switch (specifically, a thermostat) 16 that is turned on / off as the battery temperature rises is additionally provided. These are input to the microcomputer 18. An auxiliary power supply 20 is attached to the transformer 8 and the microcomputer 1
The power supply voltage is supplied to 8. Microcomputer 18
Executes the processing described later according to a predetermined program, and sends the processing result to the primary side control circuit 26 via the photocoupler 24. The primary side control circuit 26 controls ON / OFF of the switching element 6 based on the processing result of the microcomputer 18. A driving voltage is supplied to the primary side control circuit 26 from the auxiliary power source 22 attached to the transformer 8.

The microcomputer 18 inputs the signal of the charging current detection circuit 12 and adjusts the duty ratio of the switching element 6 so that the charging current has a substantially constant value. Further, according to the processing procedure of FIGS. 4 and 5, when the battery 10 is in a fully charged state, the switching element 6 is fixed off. The processing of FIGS. 4 and 5 compares the detected value VN of this time with the maximum voltage VPEAK up to now, and stops the charging when VN ≦ VPEAK continues. However, as will be described later, the comparison is not performed until the condition that the battery voltage starts to largely change is satisfied, and the VN and VPEAK are compared only when the battery voltage largely changes. This process prevents erroneous determination.

The processing of FIG. 4 is performed by the microcomputer 18
Shows a processing procedure executed by the step S
As shown in 0, a predetermined time (T1) after the start of charging
Is executed when is passed.

The predetermined time (T1) mentioned here is a predetermined time, and is a time at which the initial voltage fluctuations shown by lines A5 and A6 in FIG. 2 are almost completed. When the over-discharged battery is charged, the battery voltage rises rapidly at the beginning (line A
5) After that, it lowers once (line A6), and then gradually rises (line A2) like a normal battery. When T1 hours have elapsed after the start of charging, the battery voltage becomes a value that corresponds well to the rated voltage of the battery, regardless of the degree of discharge at the start of charging. On the other hand, the battery voltage at the start of charging may not be related to the rated voltage. For example, the battery voltage V00 (A) rated at 12 volts may be lower than the battery voltage V0 (B) rated at 7.2 volts. To get. After the lapse of T1 time from the start of charging, the above problem is resolved, and the initial voltage fluctuation that occurs during charging of the over-discharged battery has also subsided, and the situation in which the battery voltage of a battery with a low rated voltage becomes higher does not occur. There is.

The process of FIG. 4 is programmed so as to be executed when a predetermined time (T1) has elapsed after the start of charging based on such knowledge. First, in step S2, the battery voltage at that time is detected to obtain V1. Memorize as.

Next, in step S4, the detected battery voltage V1 is compared with a predetermined voltage. The charging device of this embodiment is rated at 7.2 volts, 9.6 volts and 12.0 volts.
It is planned to charge a battery having three rated voltages of V, and V9.6L, 9.6V and 12.V as predetermined voltages for distinguishing 7.2V and 9.6V.
V9.6U is used as a predetermined voltage for dividing 0 volt. V9.6L is a battery with a rating of 9.6 volts.
Batteries generated when charged for 1 hour are slightly lower than the lowest voltage among batteries, and V9.6U is slightly higher than the maximum voltage. If V1 ≦ V9.6L, the rating is 7.
A 2-volt battery is charged and V9.6L <V1 <
It can be seen that if V9.6U, the battery having a rating of 9.6 volts is charged, and if V1 ≧ V9.6U, the battery having a rating of 12.0 volts is charged.

In FIG. 4, step S6 is executed when the battery is rated at 7.2 volts, step S8 is executed when the battery is rated at 9.6 volts, and step S10 is executed when the battery is rated at 12.0 volts. To be done. Steps S6, S
8 and S10 are the predetermined potential difference ΔVS, the values ΔVS (7.2) and ΔVS (9.
6) and ΔVS (12.0) are stored.

After the above processing is finished, the processing is once finished (step S12). Next, when a predetermined period has elapsed, FIG.
Is interrupted. After that, the processing of FIG. 5 is executed by interruption every predetermined period (S14). In addition, a timer in the microcomputer 18 is used in order to execute the operation every predetermined period. First, in step S16, the battery voltage is read and set to VN (step S16). Next, the current battery voltage VN is compared with the current maximum voltage VPEAK. If the current battery voltage exceeds the current maximum voltage, that is, if step S18 is NO, the current voltage VN is determined as the maximum voltage VPEAK. Yes (step S20). If the maximum voltage VPEAK up to now is larger, step S20 is skipped. While the voltage is rising, that is, VN> V
The counter value is set to zero during PEAK (step S).
22). While the voltage is rising, the process after step S24 is not executed and the process is temporarily ended (step S36). Step S16 is a process executed by the device that detects the battery voltage every predetermined period, and steps S18 and 20 are processes executed by the device that extracts and stores the maximum voltage. That is, the battery voltage detecting device is constructed by the battery voltage detecting circuit 14, the microcomputer 18, and a program for executing the processing of FIG. 5 (particularly step S16), and the maximum voltage extracting / storing device is the microcomputer 18 and the drawing. It is constructed by a program for executing the processing of step 5 (in particular, steps S18 and S20).

When the current battery voltage VN is equal to or smaller than the maximum voltage VPEAK up to then, step S24 is executed. Here, a value obtained by adding a predetermined potential difference (ΔVS) to the battery voltage (V1) when a predetermined time (T1) has elapsed after the start of charging is compared with the current battery voltage (VN). Here, V1 is stored in step S2 of FIG. Also ΔV
S is step S6, S8, S1 depending on the rated voltage of the battery
It is set to either 0.

The processing in step S24 is performed in step S26.
It decides whether or not to skip the subsequent processing. It skips during the time of NO and executes when it becomes YES. When the battery is charged, the battery voltage rises as shown by the line A in FIG. That is, the rate of voltage increase increases before the battery is fully charged (see line A3). In step S24, it is determined whether or not the voltage sudden change range indicated by the line A3 has been reached. During the period indicated by the line A2, that is, while the voltage fluctuation is small, the processes after step S26 are not executed.
This is because if the comparison of VN ≦ VPEAK is executed also during this period, VN = VPEAK will be obtained if the voltage is detected with a coarse resolution. On the other hand, after the line A3,
Even if the coarse resolution is detected, VN and VPEAK are not always equal to each other, and the coarse resolution can be compared accurately.

The processing after step S26 is performed by the battery voltage VN.
The timing at which the voltage starts to drop after the voltage reaches the maximum voltage is detected. Therefore, if the battery voltage VN this time is smaller than the maximum voltage VPEAK, the counter value is set to 2
Step forward (step S28), and if equal (step S30) (step S18,
It will never be VN> VPEAK). As a result, VN ≦
A counter counts the number of times the VPEAK relationship is continuously detected. At this time, counting is performed once when VN = VPEAK and twice when VN <VPEAK. When it is definitely descending, it is weighted and counted.

The number of times counted as described above is compared with a predetermined number of times in step S32. VN ≦ a certain number of times
When VPEAK continues, charging is stopped in step S34. That is, the switching element 6 is held in the off state. A charge stop device is constructed by the microcomputer 18, the switching element 6, and a program for executing step S34 of FIG. If the value of the counter does not reach the predetermined number, step S32 becomes NO and the process of FIG. 5 is repeated. And when VN> VPEAK,
Step S18 becomes NO and the counter is cleared to zero (step S22). That is, V
Even if N ≦ VPEAK, unless charging is continued, charging is not stopped, and when it is continued, processing for stopping charging is executed.

As described above, when VN <VPEAK is found and it is sure that the value has fallen, weighting is performed and counting is performed so that step S32 quickly becomes YES. Although the counter is incremented by 2 in step S28 in this embodiment, it may be incremented by 3, 4, 5 ...

In the case of this embodiment, steps S26-
Since the means for detecting the timing at which the battery voltage becomes maximum after S32 starts to decrease, and this processing is executed only when the result in step S24 is YES, the battery voltage (VN) is a predetermined potential difference (Δ) to the battery voltage (V1) when a predetermined time (T1) has elapsed.
The timing detecting means is activated after the voltage becomes equal to (VS). Further, step S34 is means for stopping the charging current, and this is executed when the timing at which the charging current becomes maximum and then starts to fall is detected in steps S26 to 32.

The advantages of this embodiment will be described with reference to FIG. In the case of this embodiment, the reversal from rising to falling is detected when the voltage increase rate becomes large immediately before the fully charged state. That is, the inversion is detected when the voltage fluctuation is large within a predetermined period. Therefore, the voltage detection accuracy may be relatively rough, and for example, originally, the voltage fluctuation of the solid line may be detected as a broken line (the broken line has a coarse resolution). If the detection resolution is rough, it will not be erroneously detected that a reversal phenomenon from rising to falling has accidentally occurred due to a minute fluctuation in the battery voltage. If the resolution is coarse, detection delay may occur, but in the present embodiment, not only VN <VPEAK but also VN = VPEAK is included in the count. Therefore, the counter advances after the timing of X in FIG. 6, so that it is possible to detect a timing very close to the timing at which the counter reverses from rising to falling. Note that VPEAK = VN
However, when the counter is stepped, if it is detected with a coarse resolution, even if VPEAK <VN, VPEAK = VN
May be In this embodiment, since VPEAK and VN are compared only when the voltage changes greatly,
Even if the resolution is coarse, no inconvenience will occur.

As described above, according to this embodiment, the timing detection performance does not deteriorate even with a coarse resolution. Further, since the coarse resolution is sufficient, the electronic parts and the like can be inexpensive. In order to detect the timing when the battery voltage changes from rising to falling, the deviation of the battery voltage within a predetermined period is taken, and after it has changed from positive to negative, it is determined whether or not the negative fluctuation has continued for a predetermined number of times. You may try to see. However, in this method, a slight fluctuation in the power supply voltage may cause erroneous detection. On the other hand, in the present embodiment, erroneous detection is unlikely to occur because the voltage variation is compared with the maximum voltage instead of within a predetermined period.

In the case of this embodiment, step S24 in FIG.
After the answer is YES, the maximum voltage extraction process of steps S18 to S20 may be executed. Further, the processing of FIG. 7 may be added. That is, a means for detecting a timing at which the battery voltage is changed from rising to falling after the battery voltage becomes a voltage obtained by adding a predetermined potential difference (ΔVS) to the battery voltage (V1) after a predetermined time (T1) has elapsed, is detected. It may consist of a plurality of means.

A step S72 detects the timing when the voltage variation ΔV within a predetermined period becomes a value obtained by subtracting a constant value from the maximum variation ΔVMAX. Here, if a constant value is set as an appropriate value for each rated voltage of the battery, step S72 can be set to be YES immediately before the timing when the battery voltage changes from rising to falling. Similarly, in step S74, the reversal timing of the battery voltage from rising to falling can be detected. The battery has a characteristic that the temperature rises suddenly after it is fully charged. If the thermostat is set to this temperature, step S7
4 can detect the full charge timing.

Further, step S76 is for observing the timing when the battery voltage VN becomes lower than the maximum voltage VPEAK by a predetermined value (ΔVC). Here, if the absolute value of ΔVC is set to a small value, the battery is fully charged. You can see that Steps S26 to S32 and S72, S74, S
The present invention may also be embodied by having one or more of 76 running.

[0027]

According to the present invention, since the full charge state is detected by comparison with the maximum voltage, the counter continues to step up against fluctuations in the power supply voltage, and the timing close to the full charge timing. Will stop charging.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing the principle and operation of the present invention in comparison with a conventional example.

FIG. 2 is a diagram showing a battery voltage during charging.

FIG. 3 is a system diagram of an embodiment.

FIG. 4 is a processing procedure diagram of the embodiment.

FIG. 5 is a diagram of another processing procedure of the embodiment.

FIG. 6 is a diagram for explaining the operation of the embodiment.

FIG. 7 is a diagram showing a modification of the embodiment.

[Explanation of symbols]

 Battery voltage detection device for each predetermined period 14: Voltage detection circuit 18: Microcomputer Processing procedure of step S16 of FIG. 5 Maximum voltage extraction / storage device 18: Microcomputer Processing procedure of steps S18 and S20 of FIG. 5 Counter 18: Microcomputer Processing of Steps S28 and S30 of FIG. 5 Charge Stop Device 6: Switch 18: Microcomputer Processing Procedure of Steps S32 and S34 of FIG.

Claims (2)

[Claims] 1. A device for charging a battery by supplying a charging current to the battery, the device detecting a battery voltage at every predetermined period during charging, and extracting and storing the maximum voltage among the detected battery voltages. And a counter for comparing the detected battery voltage with the maximum voltage and stepping when the former is equal to or smaller than the latter, and when the count value of the counter is equal to or more than a predetermined value,
And a device for stopping energization of a charging current. 2. The charging device according to claim 1, wherein the counter advances one step when a battery voltage equal to the maximum voltage is detected, and a battery voltage smaller than the maximum voltage is detected. A charging device characterized by sometimes stepping n (where n is an integer of 2 or more).