JPH0447547B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Application) The present invention relates to a charging circuit for a battery that can be recharged repeatedly, and particularly to a device that is less likely to cause accidents during charging such as overcharging.

(Prior Art) Conventional charging circuits utilize the heat generated by the battery being charged at the end of charging, and stop charging upon detecting that a thermostat built into the battery is open. However, this method has the disadvantage of overcharging when the ambient temperature is low, and conversely, when the ambient temperature is high, the thermostat will open from the beginning and charging will not be possible, or even if it is possible, the charging will be insufficient. It was hot.

(Objective) An object of the present invention is to eliminate the drawbacks of the prior art as described above and to provide a suitable battery charging circuit that is not affected by ambient temperature.

(Summary) The present invention is characterized by an arithmetic device having a storage section and an arithmetic section, a period determined in advance by a signal from the arithmetic device, whose starting point is a predetermined positive voltage or higher, and whose end point is a predetermined positive voltage or more. means for generating a sawtooth wave that is less than a power supply voltage; a comparator circuit having one input terminal connected to the sawtooth wave generating means and the other input terminal connected to a battery to be charged; A constant current charging circuit is connected, and the data of the time from the starting point of the sawtooth wave until the output of the comparison circuit is reversed is stored in the storage section, and the data stored in the previous time and the current measurement are stored. After a predetermined time,
The point is that charging is stopped when the latter data shows a decreasing trend or becomes constant.

(Embodiment) FIG. 1 is a block diagram showing the principle of the present invention, and FIG. 2 is a timing chart of the main signals.

In FIG. 1, 1 is an arithmetic unit, 2 is a RAM,
3 is the CPU, 4 and 6 are the input section, 5 and 7 are the output circuits,
8 to 11 are terminals, 12 is a charging start switch, 13
14 is a constant current charging circuit, 14 is a comparator, 15 is a diode, 16 is a battery, 17 is a capacitor, 18 is a transistor, and 19 is a resistor.

Further, A to F in FIG. 2 indicate signals corresponding to points A to F in FIG. 1.

Next, the principle operation of the present invention will be explained.

When the charging start switch 12 is pressed at time _t1 , the CPU 3 is activated via the input section 4, and the signal at point B of the output terminal 9 of the output circuit 5 becomes high level. When the signal at point B becomes high, the constant current charging circuit 13 is turned on. At the same time, a signal having an oscillation waveform as shown in FIG. 2C is output from the terminal 11 via the output circuit 7.

This output is applied to the base of transistor 18. The collector of the transistor 18 is connected to the power supply V _CC
Since the capacitor 17 is connected to the midpoint of the resistor 19 and the capacitor 17, which are connected in series between the transistor 18 and GND, the capacitor 17 is discharged when the transistor 18 is on
It is charged when it is off. Therefore, the signal at point E becomes a sawtooth wave as shown in FIG. 2E. This sawtooth wave signal is applied to the positive input terminal of comparator 14.

On the other hand, diode 1 is connected to the negative input terminal of comparator 14.
A battery 16 is connected via 5, and this battery 16 is charged by a constant current charging circuit 13.
The comparator 14 compares the signal at point E and the signal at point F, and via its output terminal 10 and input section 6,
Send to CPU3.

As time passes from time _t1 , the comparator output changes as shown in FIG. 2D as the battery terminal voltage changes. In other words, the time τ from the origin of the sawtooth wave shown in FIG. 2E until the signal at point D is inverted gradually increases. This time τ reaches a maximum at the peak point of the terminal voltage of the battery 16 (time t ₂ ), and decreases thereafter. Therefore, the value of τ is stored in the memory, and if it decreases when compared with the next value, it is considered that charging is complete, and the signal level at point B is lowered.At the same time, the oscillation at point C is stopped, and the charging mode is started. escape from

Note that the reason why the terminal voltage of the battery 16 shows a voltage change that decreases after passing the peak point as shown in Figure 2 F is because the terminal voltage of a battery such as a Nikkad battery increases monotonically from the start of charging until the completion of charging. However, towards the end of charging, the internal temperature of the battery rises,
This is because the equalization internal resistance decreases.

Further, in the above embodiment, the oscillation frequency of the rectangular wave output from the output circuit 7 is set to 14 Hz according to a command from the CPU 3.

Next, a specific example of the principle of the present invention will be explained using FIG. 3. In this specific example, the eight captured data τ are averaged and compared with the average value of the previous eight data τ, and when the latter average value becomes smaller than the former, charging is completed. Furthermore, the data τ can be captured in four stages: 16 seconds, 32 seconds, 64 seconds, and 128 seconds. Here, it is assumed that data τ is taken in at intervals of 16 seconds.

Step S1...A determination is made as to whether or not the interval timer that determines the sampling time interval of the data τ has expired. If no, proceed to step S2; if yes, proceed to step S3.

Step S2...The timer is added.

Therefore, when step S1 becomes YES, it is the time for sampling the data τ. For example, in this specific example, 16 seconds have passed since the start.

Step S3...Charging data τ is taken in.

Step S3...Charging data is added.

Step S5...It is determined whether the number of additions of charging data is the eighth time. If no,
Proceed to step S6, if yes, proceed to step S6.
Proceed to S7.

Step S6...If the number of additions of the charging data is not the eighth time, the interval timer is started and the processes of steps S1 and S2 are performed again.

In this way, processing is performed until step S5 becomes YES, that is, until eight pieces of data at 16 second intervals are added. Once the 8 pieces of data have been added, the process advances to the next step S7.

Step S7...The sum of the previous eight data,
The size is compared with the sum of the eight pieces of data this time,
If the latter is equal to or larger than the former, proceed to step S8. Conversely, if the latter is smaller than the former, charging ends.

Step S8...Discard the previous sum of eight data and store the current sum of eight data. Then, it is used for comparison with the sum of the next eight pieces of data.

Next, a second specific example of the principle of the present invention will be explained with reference to FIG. In the first specific example described above, charging data was sampled at appropriate time intervals.

However, due to a power supply abnormality, such as a lightning surge or the activation of an inductive load, the voltage at point _F in FIG.
If the positive and negative pulses of a and b as shown in the V _F curve in Figure 4a are applied, and the positive and negative pulses of a and b happen to coincide with the data acquisition timing, the data will be stored in the memory area of the storage unit 2. In each case, abnormal data is input.

Therefore, the sum of the 8 pieces of data for the N-1st time is N
It is larger than the sum of the 8 pieces of data, N-1
Charging will stop when the Nth data is received. Also, even if there is no abnormality in a, when the Nth to N+1st data is received,
Since the Nth data is larger than the N+1st data, charging will be stopped.

As a countermeasure for this, if we discard the two maximum and minimum values out of the eight data and compare the sum of the remaining six data, we will get a monotonous increase as shown in Figure 4b. Charging continues. It goes without saying that this method is effective not only in case of power supply abnormality but also in case of abnormality due to other causes.

A method of discarding two of these eight data, the maximum value and the minimum value, and comparing the sum of the remaining six data will be explained with reference to FIG. FIG. 5 shows a step that replaces step S4 in FIG. Since the processing other than this step is the same as that in FIG. 3, the explanation will be omitted and only the step in FIG. 5 will be explained.

Step S41...It is determined whether the charging input data is the first one. If YES, proceed to the next step S42; if NO, proceed to step S43.

Step S42...The first input data is stored as the minimum data.

Step S43...If step S41 is NO,
Step S43 is entered, where it is determined whether the input data is the second one. If yes, proceed to step S44; if no, proceed to step S47.

Step S44...The second input data is compared with the minimum data stored in step S42. If the minimum data is smaller than the second input data, the process proceeds to step S45, and if it is larger, the process proceeds to step S46.

Step S45...The second input data is stored as the maximum data.

Step S46...The minimum data stored in step S42 is stored as the maximum data.

After step S46, the process of step S42 is performed again. Then, the second input data is stored as the minimum data.

Through the above steps, the first input data and the second input data are compared in size, and if the former is smaller than the latter, the first data is stored as the minimum data, and the second input data is stored as the maximum data. The second data is stored. Conversely, if the former is larger than the latter, the second data will be stored as the minimum data, and the first data will be stored as the maximum data.

Step S47...It is determined whether the third input data is larger than the maximum data. If yes, proceed to step S48; if no, proceed to step S50.

Step S48...The previous maximum data is deleted and the third input data is stored as the maximum data.

Step S49...The previous maximum data erased in step S48 is added.

Step S50...It is determined whether the input data is smaller than the minimum data. If yes, proceed to step S51; if no, proceed to step S49.

Step S51...Delete the previous minimum data and store the current input data as the minimum data.

Step S49...If no at step S50,
The input data this time is data that exists between the minimum data and maximum data that have already been registered, so this is added. Also, when this step S49 comes after step S51, the step
The previous minimum data erased in S51 is added.

According to the above procedure, two of the eight data, the maximum value and the minimum value, are discarded, and the remaining six data are added. Then, according to the same procedure as in FIG. 3, which is not shown in FIG. 5, when the sum of the previous six pieces of data becomes greater than the sum of the next six pieces of data, charging of the battery is assumed to have ended. Battery charging operations are stopped.

Next, the first embodiment of the present invention is shown in FIGS. 6 and 7.
This will be explained with a diagram. This embodiment differs from the principle of the present invention explained in FIG. 1 above in that a Zener diode 24 is substantially connected to the emitter of the transistor 18. Note that the resistors 20 and 21 are resistors for applying a bias voltage to the base of the transistor 18, and the diode 25 is for temperature compensation of the Zener diode 24. Also, 2
2 and 23 indicate resistors, and the other symbols indicate the same elements as in FIG. The parts not shown in Figure 6 are
Same as FIG. 1.

In this embodiment, some batteries have internal short circuits or disconnections, and charging can be quickly stopped in such a case. As shown in FIG. 6, when the Zener diode 24 is connected to the emitter of the transistor 18, the sawtooth wave generated at point E of one terminal of the capacitor 17 is as shown on the right end of FIG.
The voltage can be raised from 0 volts to V _L volts (where V _L is the Zener voltage of the Zener diode 24).

Therefore, in a short-circuited battery, the terminal voltage is less than V _L so that the comparator output does not reverse during the sawtooth engine. In this embodiment, the calculation section is configured to stop charging in such a case.

Also, set the end point of the sawtooth wave to be lower than the supply voltage V _CC
If the point V _H is set, if the charging start switch 12 is pressed with a disconnected battery or no battery inserted, the voltage at point F will be equal to V _CC and the output of the comparator 14 will also be generated during the sawtooth wave engine. There is no reversal. In this embodiment, the calculation section is configured to stop charging even in such a case.

However, when charging a fully discharged battery, the terminal voltage may not reach V _L after the start of charging. In this embodiment, the arithmetic unit is configured to continue charging during this constant engine _tS even if the comparator output is not inverted.

In addition, when charging an over-discharged battery, the
As shown in the V _B (battery charging voltage) curve, the terminal voltage of some engines may decrease after charging starts. Therefore, in this embodiment, the arithmetic device 1 is configured in this engine so as to continue charging even if the previous data becomes larger than the next data. The above engine is called an offset engine t ₀ , and t ₀
For example, 2 minutes, 4 minutes, 8 minutes and 16 minutes can be selected.

Next, a specific example of this embodiment will be explained with reference to FIG.

Step S51... Clear the charging area in the arithmetic unit.

Step S52...Starts the input prohibition timer.

Step S53...It is determined whether the input prohibition timer has expired. If no, proceed to step S54; if yes, proceed to step S54.
Proceed to S55.

Step S54...Add the timer.

Through steps S52 to S54, the process for the predetermined period _tS is performed, and the fully discharged battery is normally charged.

Step S55...When the input prohibition timer ends, the first data is input.

Step S56...It is determined whether the above data is data of an internally short-circuited battery. This is detected by the fact that the output of comparator 14 does not invert and is at a high level during the sawtooth period.

Step S57...It is determined whether the above data is data of a disconnected battery or a battery not inserted.
This is detected by the fact that the output of comparator 14 does not invert and is at a low level during the sawtooth period.

Step S58...1 is added to the error counter.

Step S59...It is determined whether the error count has become equal to 7 or not. If the value is equal to 7, it is assumed that the battery is short-circuited or disconnected, and charging is terminated. Note that here, the error count is set to 7, and when short circuit data or disconnection data is captured seven times in a row, it is determined that a short circuit or disconnection battery has occurred, but it is clear that this number is not limited to seven.

Step S60...If the data is not short circuit data or disconnection data, the count value of the error counter is cleared.

Step S61...It is determined whether the timer has reached the end of its time or is up. Initially, the timer is not in the start state, so the time is at the end or the time is up, and step S61
Then proceed to step S62.

Step S62... It is determined whether the charging data acquired in step S55 is the first time, and if it is the first time, the process advances to step S63. If it is the second time or more, proceed to step S65.

Step S63...Start the offset timer.

Step S64...The offset timer is added.

Steps S55 to S61 are performed until the offset timer reaches the end of time or times out in step S61.
And the loop of step S64 is repeated. When the offset timer reaches the end, step S62
Since this is the second or more charging data input, the process advances to step S65.

Step S65... Charging data is processed. In this step, the same data processing as in the step surrounded by the broken line A in FIG. 3 is performed.

Step S66...The interval timer is started. This step is the same as step S6 in FIG.

In addition, in the step surrounded by the broken line B in FIG. 8, the charging is continued for a certain period t _S after the start of charging for a fully discharged battery even if the output of the comparator 14 is not reversed. Processing _tS is performed for a certain period of time.

In addition, in the step surrounded by a broken line C in FIG. 8, the offset period for an over-discharged battery is
t ₀ processing is being performed.

Next, the reason why the diode 25 is included in the circuit shown in FIG. 6 will be explained.

The voltage-temperature characteristics of the positive input side terminal of the comparator 14 mainly depend on the Zener diode 24.
ΔV _Z. On the other hand, when the battery 16 is viewed as a constant voltage source, the negative input side of the comparator 14 is a value obtained by dividing the change in voltage due to the temperature characteristics of the discharge prevention diode 15 by resistance -ΔV _D1 when the diode 25 is not connected.
{R ₂₂ /(R ₂₂ + R ₂₃ )}. Since this value is divided by resistance, it is a smaller value than that on the positive input side. Therefore, connect the diode 25 and -
The temperature characteristics of the negative input side of the comparator 14 were adjusted by adding ΔV _D2 . In other words, the diode 25 is connected for temperature compensation.

(Effects) According to the present invention, there are various effects as follows.

(1) It is possible to eliminate the drawbacks of the conventional technology such as overcharging when the ambient temperature is low and charging not being possible or insufficient when the ambient temperature is high.

(2) In the conventional technology, when a fully charged battery is charged, it takes time for the temperature to rise, resulting in overcharging, but with the present invention, charging can be stopped relatively quickly and the degree of overcharging can be reduced.

(3) Since there is no need to attach a thermostat to the battery, the number of thermostats can be reduced. For this reason,
The weight and cost of the battery can be reduced, and the size of the battery can also be reduced.

(4) Even if there is a momentary power failure, the battery can be charged normally.

(5) It is possible to charge a fully discharged battery or a partially discharged battery.

(6) Batteries with internal short circuits or disconnections can be detected early and charging can be stopped.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing the principle of the present invention, Figure 2 is a block diagram showing the principle of the present invention.
The figure is a time chart of the main parts of the signals in Figure 1, Figure 3 is a flowchart showing the function of the arithmetic unit in a specific example of the principle of the present invention, and Figure 4 is a time chart of the signals of the main parts in Figure 1. FIG. 5 is a flowchart showing the functions of the arithmetic unit that deals with the case shown in FIG. 4. FIG. 6 is a circuit diagram of the first embodiment of the present invention. , FIG. 7 is an explanatory diagram of the operation of FIG. 6, and FIG. 8 is a flowchart showing the functions of the arithmetic unit in the second embodiment. 1...Arithmetic unit, 2...RAM, 3...CPU,
4, 6... Input section, 5, 7... Output circuit, 13...
...Constant current charging circuit, 14...Comparator, 16...Battery, 24...Zena diode.

Claims (1)

[Claims] 1. An arithmetic device having a storage section and an arithmetic section, a cycle determined in advance by a signal from the arithmetic device, whose starting point is a predetermined positive voltage or higher, and whose end point is a power supply voltage. a comparator circuit having one input terminal connected to the sawtooth wave generating means and the other input terminal connected to a battery to be charged; The device is equipped with a constant current charging circuit that measures the data of the time from the starting point of the sawtooth wave until the output of the comparison circuit is reversed, stores it in the storage unit, and compares the previously stored data with the currently measured data. A battery charging circuit characterized in that the battery charging circuit is configured to compare data and stop charging when the latter data shows a decreasing trend or becomes constant after a predetermined time. 2. The battery charging circuit according to claim 1, wherein charging is stopped when the output of the comparison circuit does not reverse after a predetermined period of time has elapsed. 3. Charging is continued even if the previously stored data becomes larger than the currently measured data within a predetermined time after charging is started. Battery charging circuit as described.