JPH05207670A - Storage battery charging circuit - Google Patents

Abstract

PURPOSE:To realize a storage battery charging circuit having a structure for automatically selectively discharging and charging to prevent a memory effect of a battery. CONSTITUTION:Mounting of a battery pack 5 is detected by a detection signal B from a 3V detector 62, and a pulse C for avoiding a chattering state is generated by a one-shot multivibrator 63. A detection signal A from a 5V detector 61 which detects whether the pack 5 should be once discharged or not at the timing of the pulse C is latched by a flip-flop 64 thereby accurately automatically selecting discharging necessary in the case of a shallow charging state. As a result, a memory effect can be easily prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a storage battery charging circuit, and more particularly, to a storage battery charging circuit for charging a storage battery having a memory effect such as a NiCd battery, and an improvement for eliminating the inconvenience caused by the memory effect. ..

[0002]

2. Description of the Related Art NiCd batteries are widely used in electronic devices such as so-called camera-integrated VTRs because the flat portion in discharge voltage characteristics is stable. The usage pattern is, for example, in a camera-integrated VTR, it is used by being attached to the main body as a detachable storage battery unit (so-called battery pack) separate from the main body and supplying power to the main body to consume. It is attached to a charger separate from and charged.

As described above, the NiCd battery is widely used as a secondary battery because of its excellent characteristics.
It has a so-called memory effect and also has a drawback that the battery capacity gradually decreases when shallow discharge and charge are repeated. However, this decrease in the battery capacity is not definite, and it means that the battery capacity is restored once it is completely discharged. The change in battery capacity depending on the previous charging / discharging state is also called the memory effect.

However, in a normal use method, battery characteristics are not prioritized until the device becomes inoperable due to complete discharge. If such a method is used, the operation of the device is stopped at an undesired time, and a shooting opportunity is missed. For this reason, when used normally, there is a disadvantage that the battery capacity is lowered due to the memory effect and the operating time of the device is shortened.

In order to eliminate this memory effect, it is clear from the characteristics that the storage battery may be completely discharged before charging, and as a countermeasure, a discharge circuit is provided in the storage battery charger to discharge and charge the battery. The method of doing is being adopted. FIG. 5 shows a block diagram of such a conventional charging circuit. Here, 1 is a power supply circuit of the charger main body, 2 is a charge controller for selecting charging and discharging, 3 is a switch circuit for performing charging, 4 is a discharging circuit for performing discharging, and 5 is detachable from the charger. Battery pack.

When charging and discharging the battery pack 5 with this charger, first, general household power is supplied to the power supply circuit 1.
To charge this charger into operation. Then, the battery pack 5 is attached to the charger. Next, although not shown in the figure, an operation switch or the like is operated to select discharge. In response to this operation, the charge controller 2 sends a selection signal to the discharge circuit 4, and the discharge circuit 4 discharges. As a result, the electric power remaining in the battery pack 5 is discharged.

[0007] After that, in consideration of the time and the time when the battery will be completely discharged, another operating switch or the like not shown in the figure is operated to select charging. In response to this operation, the charge controller 2 stops sending the selection signal to the discharge circuit 4 and sends the selection signal to the switch circuit 3. As a result, the battery pack 5 is charged from the power supply circuit 1 via the switch circuit 3. In this way, the memory effect can be prevented by providing the discharging function in addition to the charging function.

[0008]

However, in the charger having the conventional structure, it is inconvenient because the user needs to operate the switch of the charger or the like to select the charging / discharging as described above.
In addition, since it is necessary for the user to determine whether or not the battery has been completely discharged by measuring the time or the like, the user tends to discharge the battery for an unnecessarily long time for safety, which is inefficient.

Further, if the charger is connected to an outlet or the like and is not supplied with electric power, the charge controller cannot operate during this period, so that neither charging nor discharging can be performed, resulting in high efficiency of use. bad. An object of the present invention is to solve the above-mentioned problems of the prior art, and to realize a storage battery charging circuit configured to automatically select and execute discharging and charging for preventing a memory effect of a battery. Especially.

[0010]

In the structure of the storage battery charging circuit of the present invention which achieves the above object, the output voltage from the storage battery is compared with a first predetermined value, and the comparison result is used for discharging operation. A first detection circuit for outputting as a first detection signal indicating whether or not to perform, and an output voltage from the storage battery and a first detection circuit.
A second detection circuit that compares a second predetermined value that is smaller than the predetermined value of, and outputs the comparison result as a second detection signal that indicates whether or not the storage battery is mounted. , One shot that outputs a pulse when the second detection signal is continuously output for a predetermined time, and holds the value of the first detection signal at the timing of the pulse, and resets by a signal according to the first detection signal Flip-flops
These devices receive electric power from the storage battery, operate using the output voltage thereof as their own power supply voltage, and select discharge or charge of the storage battery according to the output value from the flip-flop.

[0011]

In the storage battery charging circuit of the present invention having such a configuration, the second detection circuit automatically detects the mounting of the storage battery, and the first detection circuit automatically detects the charging state of the mounted storage battery, The discharge and charge for preventing the memory effect of the above are automatically selected and executed. Therefore, the user does not need to operate a switch or the like to select charge / discharge, which is convenient. Further, whether or not the battery has been completely discharged can be automatically determined according to the output value of the flip-flop. Therefore, it is convenient because it does not bother the user, and it is efficient because it does not unnecessarily discharge for a long time.

Further, even when the charger is not connected to an outlet or the like, that is, when the power is not supplied, the detection circuit, the one-shot, the flip-flop, etc. can be operated by the power from the installed storage battery. Is possible. Of course, if the storage battery does not store any electric power, such an operation is impossible. However, in this case, the storage battery is originally in a completely discharged state, so that there is no inconvenience even if the storage battery is not discharged. Therefore, since the discharge can be performed even when the power is not supplied, the usable range is widened and the use efficiency is improved as compared with the conventional case.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A charger as an embodiment of a storage battery charging circuit of the present invention will be described below with reference to the block diagram of FIG. Here, 1 is a power supply circuit of the charger main body, 3 is a switch circuit for charging, 4 is a discharge circuit for discharging, and 5 is a battery pack that is attached to and detached from the charger. It is the same. further,
20 is a charge controller. Reference numeral 61 is a 5V detection circuit, 62 is a 3V detection circuit, 63 is a one-shot, and 64 is a flip-flop.
It is a circuit that operates even at low voltage below or below, for example,
It is composed of bipolar transistors.

The charge controller 20 has a structure similar to that of the conventional one, operates by receiving power supply from the power supply circuit 1, selects the switch circuit 3, and selects the battery pack 5.
Charge. However, the discharge is controlled indirectly by outputting the reset signal to the flip-flop 64 and inputting and monitoring the output value of the flip-flop 64 without directly outputting the selection signal to the discharge circuit 4. Has been improved.

The 5V detection circuit 61, which corresponds to the first detection circuit, is connected in series to divide the output voltage Vcc of the battery pack 5, for example, with a band-cap constant voltage generation circuit for giving a predetermined reference voltage. Resistance (not shown)
And a comparator that compares these voltages,
The output voltage Vcc of the battery pack 5 is, for example, 4.85V.
Detection signal A when larger (corresponds to the first detection signal)
"H" is output to. However, in order to prevent malfunction due to noise or the like, a hysteresis characteristic is provided to the comparator or the like, and when the voltage shifts to 4.52 V or less, "L" is output to the detection signal A.

The 3V detection circuit 62, which corresponds to the second detection circuit, has substantially the same configuration as that of the circuit 61, and when the output voltage Vcc of the battery pack 5 is higher than 2.80V, for example, the detection signal B (first (Corresponding to the detection signal of 2) is output. After all, in order to prevent malfunction due to noise or the like, the comparator or the like is provided with a slight hysteresis characteristic.
The time constant of the one-shot 63 is variable by an externally connected capacitor, but is normally set to about 200 ms, which is sufficiently longer than the chattering occurrence period of several ms or less, and the detection signal B is continuously output for that time or longer. Then, the pulse C is output for the first time.

In this way, by pulsing the continuous state at the beginning of the rise of the detection signal B with the one-shot 63,
The timing at which the chattering at the output voltage Vcc immediately after the battery pack 5 is attached and the output voltage Vcc becomes stable can be obtained as the pulse C. 200m above
The set value s is a time sufficiently longer than the chattering occurrence period of several ms or less. Also, one shot 6
Since the retriggerable one is adopted for 3 and the output of the detection signal B shorter than the set value is ignored, the influence of the fluctuation of the detection signal B during the chattering can be eliminated.

The flip-flop 64 is a D-type flip-flop and receives the detection signal A as a data input, the pulse C as a clock input, and the inverted signal of the detection signal A as a reset input. Then, the normal output signal D is output to the discharge circuit 4, and the normal output signal D is output.
Is "H", the discharge circuit 4 is turned on and the battery pack 5 is discharged. Further, since the flip-flop 64 is reset by the charge controller 20 as described above, not only the flip-flop 64 automatically operates but also the control from the charge controller 20 is followed.

Since the circuits 61 to 64 and the like use the output voltage Vcc from the battery pack 5 as their operating power source, even if the charge controller 20 cannot operate, at least the discharge is performed independently. It is possible. Further, since the non-inverted output signal D of the flip-flop 64 is also sent to the charge controller 20, the charge controller 20 is not discharged as long as power is supplied from the power supply circuit 1 and it is operable. At some times, the switch circuit 3 is selected and brought into conduction, whereby charging can be automatically performed.

The operation of the charging circuit having such a configuration will be classified into three types according to the charge level of the battery pack 5 and will be described below with reference to the waveform examples of FIGS. 2, 3 and 4, respectively. As described above, in the case of discharging with this charger, unlike the conventional case, the power supply to the power supply circuit 1 is not a necessary condition, and the power may be supplied by the time of charging. Therefore, it is further divided into cases depending on the timing of when the power is supplied.If the power is not supplied to the charger from the beginning of mounting, the charging start timing is simply delayed until the power supply timing. It is only given away. Therefore, a case where power is supplied to the charger and discharging and charging are automatically and continuously performed, which is a normal usage, will be described as an example.

First, FIG. 2 shows an example of the waveform of each signal when the charge level of the battery pack 5 is in the state where the output voltage is 0 to 2.8 V, that is, when the battery pack 5 is hardly charged. Corresponding signals and waveforms are given the same reference numerals to clearly indicate the corresponding relationship (the same applies hereinafter). In this case, when the battery pack 5 is attached to the charger, the output voltage Vcc of the battery pack 5 is small, so that chattering hardly occurs (see the waveform Vcc).

Therefore, when the battery pack 5 is simply attached to the charger, the detection signal A is "L" (refer to when the waveform A is attached), and the detection signal B is not output, so that the pulse C is not output (waveform). Refer to when C is attached). Therefore, the value of the flip-flop 64 is not set,
The output signal D remains "L". Therefore, in this case, discharging is not performed only by mounting the battery pack 5 on the charger.

When charging is performed via the switch 3 under the control of the charge controller 20, the output voltage Vcc of the battery pack 5 gradually rises (see the waveform Vcc). Then, the detection signal B is output when the voltage Vcc reaches 2.8 V, and 200 ms after that, the pulse C is output (see a in FIG. 2). In response to the pulse C, the flip-flop 64 inputs the value of the detection signal A as its value, but since the battery pack 5 is not charged to 4.85V in a short time of 200 ms, the detection signal A is at this timing. It is still "L", and the value of the output signal D from the flip-flop 64 remains "L" (see b in FIG. 2).

After that, charging proceeds and the voltage Vcc is 4.85.
When the voltage reaches V, the detection signal A is output, but the pulse C
Is not output, the value of the output signal D from the flip-flop 64 is still "L" (c in FIG. 2).
reference). Then, charging is continued. Therefore,
When the battery pack 5 is almost uncharged, necessary charging is automatically performed immediately after mounting and thereafter without unnecessary discharging.

Next, FIG. 3 shows an example of the waveform of each signal when the charge level of the battery pack 5 is in the state of the output voltage of 2.8 to 4.85V, that is, in the state of being slightly charged. In this case, when the battery pack 5 is attached to the charger, chattering of a value corresponding to the output voltage Vcc of the battery pack 5 occurs (see d in FIG. 3). Then, the detection signal B is output, and 200 ms after that, the pulse C is output (see d in FIG. 3).

On the other hand, the detection signal A is "L" at this timing because the output voltage Vcc from the battery pack 5 is 4.85 V or less when the battery pack 5 is mounted on the charger (see mounting of waveform A). .. Therefore, in response to the pulse C, the flip-flop 64 inputs the value of the detection signal A as its value, but since the value of the flip-flop 64 is not set, its output signal D remains "L" (see FIG. 3). f)). Therefore, in this case as well, discharging is not performed only by mounting the battery pack 5 on the charger.

When charging is performed through the switch 3 under the control of the charge controller 20 which monitors that the value of the signal D is "L", the output voltage Vcc of the battery pack 5 gradually rises. (See waveform Vcc). Then, when the charging progresses and the voltage Vcc reaches 4.85V, the detection signal A is output, but the pulse C is not output. Therefore, the value of the output signal D from the flip-flop 64 does not change and "L". “(See g in FIG. 3). Then, charging is continued. Therefore, even when the battery pack 5 is in a slightly charged state, the necessary charging is automatically performed immediately after mounting and after that without unnecessary discharging.

Finally, FIG. 4 shows an example of the waveform of each signal when the charge level of the battery pack 5 is at an output voltage of 4.85 V or higher, that is, when the battery is shallowly charged or fully charged. In the case of NiCd battery,
Due to the stable output voltage (which is desirable for the purpose of use), it is difficult to determine whether the state of shallow charging or full charging is the output voltage Vcc. Therefore, in these cases, the discharge is once performed in the shallow discharge state on the safe side.

In this case, when the battery pack 5 is attached to the charger, chattering of a value corresponding to the output voltage Vcc of the battery pack 5 occurs (see h in FIG. 4). The detection signal B is output in small increments (for example, in a time width of several μs) in response to this chattering, but the pulse C is not output during the chattering occurrence period due to the action of the one-shot retriggerable (i in FIG. 4). reference). Then, from the output of the detection signal B when the chattering subsides, 20
After 0 ms has elapsed, pulse C is output (see j in FIG. 4).

On the other hand, when the battery pack 5 is attached to the charger and chattering is settled, the output voltage Vcc from the battery pack 5 quickly reaches 4.85 V or higher, so that the value of the detection signal A immediately becomes "H". (K in FIG. 4
reference). Therefore, when the flip-flop 64 receiving the pulse C inputs the value of the detection signal A as its value, the value of the flip-flop 64 is set at this timing, so that the output signal D thereof becomes "H" (FIG. 4). 1).

Therefore, in this case, when the battery pack 5 is mounted on the charger, the discharging circuit 4 which receives the signal H of "H" discharges the battery pack 5. Further, since the charge controller 20 monitors the signal D, the charge is not selected and the discharge is not hindered while the value of the signal D is "H". When such discharge is performed, the output voltage Vcc of the battery pack 5
Gradually falls (see waveform Vcc).

Then, the discharge progresses and the voltage Vcc becomes 4.52.
When V (this is 4.85V-hysteresis) is reached, the output of the detection signal A becomes "L" (see m in FIG. 4). Then, since the flip-flop 64 uses the inverted signal of the detection signal A as a reset input, the value of the output signal D from the flip-flop 64 becomes "L" (n in FIG. 4).
reference). In response to this, the discharge by the discharge circuit 4 ends. Then, when charging is performed through the switch 3 under the control of the charge controller 20 that monitors that the value of the signal D has become "L", the output voltage Vcc of the battery pack 5 gradually rises. (See waveform Vcc).

Then, charging proceeds and the voltage Vcc is 4.85.
When the voltage reaches V, the detection signal A is output, but the pulse C
Is not output, the value of the output signal D from the flip-flop 64 is still "L" (o in FIG. 4).
reference). Then, charging is continued. Therefore,
When the battery pack 5 is in a state of being shallowly charged or completely charged, the battery pack 5 is once discharged to a completely discharged state immediately after being mounted, and thereafter, necessary charging is automatically performed continuously.

The correspondence relationship between the value of each signal and "H" or "L" in this example is an example, and which of positive logic and negative logic is adopted is arbitrary. Further, the configuration of the above-described embodiment is sufficient as long as the circuit operates normally, but the connection of the battery pack 5 is due to mechanical contact, the order of turning on the power supply to the power supply circuit 1, the influence of the use environment, etc. Therefore, there is a high risk of malfunction of the circuit due to external noise or the like. To prevent such malfunction, for example,
By limiting the clock input of the flip-flop 64 by using the output of the flip-flop set by the signal D and reset by the signal B, it is preferable to prevent the discharge operation from being erroneously performed a plurality of times.

[0035]

As can be understood from the above description, in the storage battery charging circuit having the configuration of the present invention, when the output voltage Vcc of the battery pack 5 is 4.85 V or less, that is, complete discharge is performed to prevent the memory effect. In case of state,
Charging is automatically performed without wasteful discharge. When the output voltage Vcc of the battery pack 5 is 4.85 V or higher, that is, when the battery pack 5 is not completely discharged to prevent the memory effect, it is automatically discharged once and then continuously charged. Be seen.

Therefore, since the battery pack 5 is automatically processed in any state, it is said that the discharge / charge is selected by observing the time and the time when the battery pack 5 may be completely discharged or operating the operation switch or the like. A charger with the charging circuit of the present invention, which is not necessary, is convenient and efficient. As a result, the storage battery charging circuit having the configuration of the present invention has an effect that the memory effect of the battery can be easily prevented without being aware of it.

[Brief description of drawings]

FIG. 1 is a block diagram of a charger as an embodiment of a storage battery charging circuit having the configuration of the present invention.

FIG. 2 is a waveform diagram for explaining the operation of the circuit, particularly when the battery pack is hardly charged.

FIG. 3 is a waveform diagram for explaining the operation of the circuit, particularly when the battery pack is slightly charged.

FIG. 4 is a waveform diagram for explaining the operation of the circuit, particularly in the case where the battery pack is not yet completely discharged.

FIG. 5 is a block diagram of a conventional charging circuit.

[Explanation of symbols]

 1 Power Supply Circuit 2 Charge Controller 3 Switch Circuit 4 Discharge Circuit 5 Battery Pack 20 Charge Controller 61 5V Detection Circuit 62 3V Detection Circuit 63 One Shot 64 Flip Flop

Claims (1)

[Claims] 1. A first voltage indicating whether or not a discharge operation is performed by comparing an output voltage from a storage battery with a first predetermined value.
Of the output voltage from the storage battery and a second predetermined value smaller than the first predetermined value, and outputs the comparison result to the state in which the storage battery is mounted. A second detection circuit which outputs as a second detection signal indicating whether or not there is one, and a one-shot which outputs a pulse when the second detection signal is continuously output for a predetermined time,
A flip-flop which holds the value of the first detection signal at the timing of the pulse and is reset by a signal according to the first detection signal, which receives electric power from the storage battery and outputs its output voltage to its own power supply voltage. A storage battery charging circuit, which operates as a battery, and selects discharge and charge of the storage battery according to an output value from the flip-flop.