JPH0614768B2 - Charge amount display circuit - Google Patents

Description

TECHNICAL FIELD The present invention relates to a charge amount display circuit, and more particularly to a circuit suitable for displaying the charge state of a secondary battery incorporated in a small electric device.

[Conventional technology]

Conventionally, a display circuit of this type is generally one that displays whether or not charging is performed exclusively by turning on a light emitting diode in conjunction with the start of charging.

In addition, an attempt has been made to provide a display corresponding to the count value, which is equipped with an up-down counter and regards the period when the secondary battery is separated from the main unit as the charging period, and counting up the counter during that period. There is. (See, for example, JP-A-56-94934).

[Problems to be Solved by the Invention]

However, if you only display the charging status like the former, it is obvious from the fact that the device is set in the outlet, so it only serves as an alarm to prevent overcharging, and as a charging display. It's not very necessary.

On the other hand, in the latter method of displaying the amount of charge using a counter, the charge state can be known over time, but since the charge period is determined artificially, the cumulative error of the counter accumulates and the accurate charge It is difficult to display the quantity.

The present invention has been made in view of the above problems,
It is an object of the present invention to provide a charge amount display circuit that can accurately display the charge amount with a relatively simple configuration.

It is another object of the present invention to provide a charge amount display circuit capable of displaying a capacity appropriately corresponding to the current charge capacity even when the charge characteristics of the battery change due to repeated charging.

[Means for Solving the Problems]

The charge amount display circuit according to the present invention, as shown in the schematic configuration of FIG. 2, outputs a pulse signal corresponding to the period of application of the charge voltage to the battery 6, and outputs the pulse signal generator 15
And a storage unit 21 that sequentially accumulates and stores the number of input pulses of the pulse signal, and a display unit 22 that displays the stored value in the storage unit 21 in correspondence with the magnitude of the stored value.

Further, the integrated value stored in the storage unit 21 is calculated by the battery 6
This is performed after the terminal voltage of exceeds the set value of the initial charging voltage.

[Action]

With the above configuration, when it is confirmed that the charging voltage is applied to the battery 6 and the charging is actually started by detecting the output of the charging circuit 11 by the charging timing detection unit 19, for example, the charging voltage A pulse signal is generated from the pulse signal generator 15 according to the application timing.

On the other hand, in the storage unit 21, when the above-mentioned pulse signal is input, the number of pulses of the pulse signal is sequentially integrated, so that the value corresponding to the current charge amount of the battery 6 is stored in the storage unit 21 and the display unit 22 is displayed.

The accumulated value stored in the storage unit 21 is detected, for example, by the voltage detection unit 18, and is not performed until it is confirmed that the terminal voltage of the battery 6 exceeds the charging initial voltage set value. By performing the above, even if the charging characteristics of the battery change due to repeated charging and discharging, integration is performed starting from a fixed reference time point, and the cumulative error is controlled.

This initial charging voltage setting value is, for example, about 1.0 V for a single nickel-cadmium battery, and the charging efficiency is high because the charging flow, that is, most of the input energy is spent converting the active material into a form that is easily charged. Is low, and the amount of input energy itself in this region is unlikely to be discharge energy. Therefore, the amount of input energy is not integrated as a stored value for accuracy.

〔Example〕

Hereinafter, an example in which the present invention is applied to the electric shaver 1 shown in FIG. 1 is shown, but the present invention is not limited to this, and can be applied to a charging circuit in various rechargeable small electric devices such as a tape winder and a flashlight in substantially the same manner. Of course.

The electric razor 1 embodying the present invention is provided with an outer blade 3 on the upper part of a main body case 2 in a detachable manner, and an inner blade 4 is inscribed in the outer blade 3 so as to be reciprocally movable. A motor 5 for reciprocating the inner blade and a battery 6 for supplying electric power to the motor 5 are housed inside.

The battery 6 is a secondary battery that can withstand multiple charging / discharging operations, such as a nickel-cadmium battery. In this embodiment, an AA battery with a battery capacity of about 500 mAh is used, and the lower portion of the main body case 2 is used. The charging unit 7 is provided in the battery so that the battery 6 can be directly charged from the commercial AC power source.

The charging section 7 is provided with a plug blade 9 at the lower end of the main body case 2 so that the plug blade 9 can be retracted and retracted, and as shown in FIG. 3, the commercial AC voltage input from the plug blade 9 is supplied to a predetermined charging voltage by a charging circuit 11 including an inverter circuit. Convert to. Further, on the output side of the charging circuit 11, a battery 6 and a switching unit 12 that regulates the energization state of the battery 6 are connected in series.

The switching unit 12 is a switching transistor, and its base end is connected to the cathode side of a light emitting diode 16 provided on the front surface 8 of the main body case 2 for displaying the charging time. Therefore, when a commercial AC voltage is applied to the charging circuit 11 to turn on the light emitting diode 16, the switching unit 12 is turned on in conjunction with that, the battery 6 is connected to the charging circuit 11 and charging is started. .

Both ends of the battery 6 are a DC-DC converter 17 that supplies a predetermined DC voltage to the electronic circuit described below, and a terminal voltage of the battery 6 is lowered to, for example, 1.0 V or less and the battery 6 runs out of capacity. Upon detection, the reset signal r is generated to connect to all circuits, particularly the voltage detection unit 18 for returning the count value of the storage unit 21 to the initial state. Further, both ends of the battery 6 are connected to both ends of the motor 5 via a main switch 13 arranged in the center of the front surface of the main body case 2, and the battery 6 is energized from the battery 6 in conjunction with the on / off operation of the main switch 13. The state is regulated.

Further, the charge period of the battery 6, the drive period of the motor 5, and the stop period of the electric razor 1 are detected, and the amount of charge in the battery 6 is displayed on the display circuit 14.

The display circuit 14 can control the generation rate and the generation timing of the pulse output from the pulse signal generation unit 15 by the detection signals output from the charge timing detection unit 19 and the discharge timing detection unit 20, and generate the pulse during charging. The number of outputs of the battery 6 is added and stored in the storage unit 21, and conversely, at the time of charging, the stored value in the storage unit 21 is subtracted at a rate proportional to the load current I, so that the battery 6 is always stored in the storage unit 21. Is stored as a numerical value proportional to the current charge amount, and the count value in the storage unit 21 is appropriately output to the display unit 22 so that the current value of the charge amount can be displayed.

That is, the secondary battery 6 of this type usually has a terminal voltage of 1.
The amount of charging current is set so that the battery will be fully charged in about 8 hours after the voltage drops to 0 V or less and the capacity is completely exhausted. On the other hand, when discharging is performed with the motor 5 of the electric razor 1 as a load, the capacity of the battery 6 is exhausted by continuous driving for about 40 minutes, depending on the discharge current value. Furthermore, even when the motor 5 is stopped, the capacity of the battery 6 gradually decreases due to the maintenance current of the circuit.

Therefore, the storage unit 21 is configured by an up-down counter, the terminal voltage of the battery 6 is compared with the charging initial voltage set value by the voltage detection unit 18, and the storage unit 21 is held while the terminal voltage is below this set value. A reset signal r is sent to the storage unit 21 to keep the count value of the storage unit 21 at the initial value "0".

Here, at the time of charging, the signal output from the charging time detection unit 19 is input to the control terminal of the storage unit 21 to make the storage unit 21 an up counter, and the charging is completed when the pulse count number in the storage unit 21 is 8 hours. The generation rate of the charging pulse output from the pulse signal generator 15 is set so that the set value is reached.

On the other hand, while the electric razor 1 is in use, that is, while the battery 6 is being discharged, the output signal s from the charge timing detection unit 19 is inverted, and the storage unit 21 is a down counter contrary to the above.
Here, by arranging the frequency dividing unit 28 having a variable frequency dividing ratio between the pulse signal generating unit 15 and the storage unit 21 and changing the frequency dividing ratio of the frequency dividing ratio 28 in accordance with the discharge current amount, During the charging period, the total number of pulses accumulated and stored in the counter 21 is subtracted by a variable discharge pulse having a higher frequency than during charging and corresponding to the load current, and the charge currently stored in the battery 6 is charged. A value proportional to the quantity is constantly stored in the storage unit 21. Therefore, by displaying the stored value on the predetermined display unit 22, the current capacity of the battery 6 can be continuously grasped.

It should be noted that in a normal charging circuit, only the above-described charging and motor driving may be a problem, but in the present embodiment, since the value stored in the storage unit 21 is held even when the motor 5 is stopped, it is not so much. But it is consuming current. Therefore, in order to correct the current, a self-discharge pulse that is output at an extremely long time interval is generated during the non-use period of the electric shaver 1, and the stored value in the storage unit 21 is subtracted by this pulse.

The above-mentioned configuration will be described with reference to more specific numerical values. The pulse signal generator 15 includes three sets of pulse generators 23, 24 and 25 for charging, main discharging and self-discharging and a pulse switching unit 27. Each pulse generator 23.24.
A pulse signal of the generation rate individually set for each 25 is selectively sent to the frequency dividing unit 28 by the pulse switching unit 27.

The pulse switching unit 27 is configured by combining, for example, a plurality of logic gate circuits, and the charge timing signal s extracted from the charge timing detection unit 19 by shaping the waveform of the output of the charging circuit 11 and the like will be described later. The zero rotation detection signal f, which is output from the motor rotation speed detection unit 31 and indicates that the motor 5 is stopped, is connected and switched. That is,
When both the charge timing signal s and the zero rotation detection signal f are “1”, the charging pulse generator 23 is selected, and when both are “0”, the discharge pulse generator 24 is selected, and the zero rotation detection signal is further selected. If only one is “1”, the self-discharge pulse generator 25 is selected and connected to the frequency dividing unit 28.

The frequency divider 28 includes a first frequency divider 29 configured by a 4-stage binary counter and a second frequency divider 30 configured by a 6-stage binary counter in series, and includes a first frequency divider. pulse signal input to 29, the second frequency divider 30 output side of the generation rate is up to 1/2 ^10, i.e. retrieved in 1 frequency-divided 1024 minutes.

Further, when the up / down counter of the storage unit 21 used as a memory of the charge amount is configured by 8 steps of binary numbers, the maximum count number is 2 ⁸ -1, that is, 255. Here, when the upper 4 bits of the storage unit 21 become "1", that is, when 240 pulses are counted, a full charge is displayed,
Further, in order to stop charging after counting the 255th pulse, since 8 hours = 2.8 × 10 ⁴ seconds, the pulse rate of the charging pulse output from the charging pulse generator 23. P ₁ is P ₁ = 2.8 × 10 ⁴ /(255×1024)=0.1 seconds, which is 1 every 0.1 seconds from the charging pulse generator 23.
It can be seen that the counter of the storage unit 21 becomes an 8-hour timer by generating the pulse.

On the other hand, a DC motor using a permanent magnet for the field is often used as the motor 5 for this kind of small electric equipment, and as a result, as shown in FIG. The load power supply I supplied to the motor 5 during driving increases as the power supply I increases. Furthermore, the load current I
The increase in the load current I appears as a decrease in the rotation speed n of the motor. Therefore, the increase in the load current I can be indirectly determined by detecting the increase or decrease in the rotation speed n of the motor. Further, an increase in the load current I leads to a decrease in the continuous driveable time of the motor 5 from the fully charged state. However, if the capacities of the battery 6 and the motor 5 are set, the motor rotation speed n and The relationship with the continuous drive possible time of the motor 6 is obtained.

The curve shown by the solid line in FIG. 5 shows an example of such a relationship, and the broken line shows the curve approximated by a stepwise straight line. From this result, the rotation speed n of the motor 5
Is detected by the motor rotation speed detection unit 31, and the frequency division ratio of the frequency division unit 28 is changed stepwise according to the detection value of the rotation speed detection unit 31, so that the output end of the frequency division unit 28 The main discharge pulse whose pulse rate changes in a manner similar to the increase / decrease of the load current I is obtained, and the stored value in the storage unit 21 is subtracted with the main discharge pulse to obtain the load current I
The value in the storage unit 21 can be reduced at a rate according to.

The discharge timing detection unit 20 detects the leakage magnetic flux generated from the armature during rotation of the motor 5 or the magnetic flux change caused by a magnet (not shown) integrally attached to the rotating shaft of the motor 5 after the detection coil 32 detects the leakage magnetic flux. By waveform-shaping the detection signal with the Schmitt trigger 33, a rotation pulse a having a pulse rate proportional to the rotation speed n of the motor 5 is formed as shown in FIG.

The motor rotation detection unit 31 samples the number of rotation pulses a for a set time and counts the rotation number counting unit 3
4 and a rotation speed determination unit 36 for determining the magnitude of the count number in the count unit 34, and output from the rotation speed determination unit 36 to the frequency division ratio conversion unit 37 combined with the first frequency divider 29. The converted signal is input to change the frequency division ratio of the first frequency divider 29.

The rotation speed counting section 34 includes a rotation speed counter 39 having a binary four-stage sampling function and a monostable multivibrator 40 for generating a gate signal b for setting the sampling period of the counter 39, and a self-discharge pulse. The self-discharge pulse c output from the generator 25 is applied to the differentiation circuit 4
Differentiate by 1 to generate a trigger signal d, which clears the counter 39 and regulates the generation timing of the gate signal b. That is, as shown in FIG. 6 (a), each time one self-discharge pulse c is output, the signal c is differentiated by the differentiating circuit 41 to generate the trigger signal d (see FIG. 6 (b)). ). Such a trigger signal d resets the content e of the rotation speed counter 39 as shown in FIG. 6 (f) and simultaneously activates the monostable multivibrator 40, and the counter 39 is generated by the gate signal b output from the monostable multivibrator 40. The gate of is opened and the pulse number of the rotation pulse a output from the discharge timing detection unit 20 is sampled.

In the present embodiment, a rotation number counter 39 having a binary four-stage structure is used so that the rotation pulse a corresponding to the sampling number in the range of "0 to 15" can be detected. Therefore, by appropriately selecting the pulse rate of the rotation pulse a output from the discharge timing detection unit 20 and the pulse width of the monostable multivibrator 40, the rotation speed counter shown in FIG. The count number e of 39 is "15" and "1" when it is 4,700 to 5,100 rotations.
4 ", 4300 to 4700 rpm," 13 ", 4300 rpm or less can be set to" 12 "or less. Further, assuming that the drivable time when the count number of the rotation speed counter 39 is “15” is “10”, the rotation speed counter 39 is
Since the drivable time decreases by 10% each time the number of counts in 1 decreases, the frequency division ratio of the first frequency divider 29, which is basically a binary four-stage hexadecimal, is calculated by the count of the rotation speed counter 39. When the number is "15", the discharge pulse having a pulse rate corresponding to the magnitude of the load current I is obtained by sequentially lowering the number in decimal notation and in the case of "14" as nine.

Further, the total count value “255” counted by the up / down counter of the storage unit 21 over 8 hours during the charging period.
However, the discharge pulse rate P ₂ may be set so that it becomes “0” in about 38 minutes at the time of discharging corresponding to the case where the first frequency divider 29 is switched to decimal. In this case, the pulse of the first frequency divider 29 is output to the storage unit 21 via the second frequency divider 30 of binary 6 stages (64 counts). The pulse rate P ₂ is P ₂ = 38 × 60 / (10 × 64 × 255) = 0.14 [sec], which is about 0.014 from the main discharge pulse generator 24.
It is understood that one pulse should be generated every second.

On the other hand, when the plug blade 9 is pulled out from the outlet and the charging of the battery 6 is stopped, the pulse switching unit 27 switches to the self-discharge pulse generator 25 side, and the self-discharge pulse c output from the pulse generator 25 is divided. The value stored in the storage unit 21 is subtracted by being applied to the storage unit 21 via the unit 28, and the decrease in the battery capacity due to the circuit holding current flowing during the device suspension period is corrected.

The decrease in the battery capacity due to such a current is such an amount that the charged amount becomes zero in about 2 months from the fully charged state. Therefore, the pulse rate P ₃ of the self-discharge pulse c is 5.2 × 10 ⁶ seconds for 2 months, so P ₃ = 5.2 × 10 ⁶ / (255 × 1024) = 20 [sec], which is the pulse for self-discharge. The generator 25 outputs a self-discharge pulse c every 20 seconds for one pulse.

The zero rotation detecting unit 43 provided on the output side of the rotation number counting unit 34 has a sampling number e in the rotation number counter 39 of "0", that is, "1" when the rotation of the motor 5 is stopped.
Output a signal. The zero signal f is applied to the pulse switching unit 2
7, the pulse generator is switched to the self-discharge pulse generator 25 side in conjunction with the "0" signal of the charging timing signal s, and at the same time, it is inverted by the inverter 44 to become "0", By inputting to the display drive unit 45, the display 46 is turned off while the motor is stopped, and the power consumption by the display unit 22 is suppressed.

The display drive unit 45 takes out the upper 4 bits of the storage unit 21 as a data signal, decodes the hexadecimal number displayed in the binary 4 digits, and displays it on the display unit 46. Display 46 is 4
The light emitting diodes 47 are arranged in the center of the front surface 8 of the main body case 2, and the number of emitted lights of the four light emitting diodes 47 is increased or decreased according to the stored value in the storage unit 21. For example, during the charging period, the number of lights is increased by one every two hours from the start of charging, and when the upper 4 bits in the storage unit 21 are all set to "1", all the four light emitting diodes 47 are turned on. The charge is displayed to indicate that the charging is completed, and further, the charging is continued and all 8 bits of the storage unit 21 become zero. At the same time, a carry signal is output, and the output signal for driving the light emitting diode from the display drive unit 45 disappears. At this time, since the switching unit 12 for regulating the state of charge of the secondary battery 6 is connected to the light emitting diode 16 for displaying the charging time, the switching unit 12 is turned off to forcibly stop the charging of the battery 6. Prevent overcharging.

Next, the flow of operation in the above configuration will be described with reference to FIGS. 7 and 8.

When charging is started at time t ₀ , it is determined in step 101 that charging has been started, and the counter of the storage unit 21 is switched to the up side (step 102).
The terminal voltage of the battery 6 gradually rises. However, if it is determined in step 103 that the terminal voltage of the battery 6 is lower than 1.0 V, the count value in the storage unit 21 is reset (step 104) and the initial value "0" is set.
Keep the state. Here, only when it is determined that the battery voltage exceeds 1.0 V at time t ₁ , the storage unit 21 starts counting the charging pulse with reference to the time t ₁ (step 105), and the count state is further changed. This is displayed by the light emitting diode 47 of the display unit 22 (step 106).

Here, when the charging is continued and about 8 hours have elapsed from the time t ₁ , all four light emitting diodes 47 for display are turned on to indicate that the battery 6 has reached full charge. Further, even if the charging state is continued, the output of the display unit 22 is cut off after a predetermined time elapses, the switching unit 12 is opened, and the overcharge of the battery 6 is prevented.

In time t _2, the same time remove the plug blades 9 from the outlet to stop the charging, charging in step 101 it is determined to have been stopped, the storage unit 21 is switched to the down side (step 107). At this time, the terminal voltage of the battery 6 is 1
If it is V or less, the count value of the storage unit 21 is reset in the same manner as described above (step 109), but if it is determined in step 108 that it is 1 V or more, step 110.
Then, it is determined whether the motor 5 is rotationally driven. At this time, if it is determined that neither charging nor motor driving is performed, the storage in the storage unit 21 is subtracted at a rate sufficiently lower than that at the time of discharging to correct the power consumption amount when the device is not used (step 111). . At the same time, in step 112, the light emission display on the display unit 22 is stopped, and the power consumption is suppressed to a necessary minimum such as storing the stored value in the storage unit 21.

Next, at time t ₃ , when the switch 13 is closed and the motor 5 is energized, the rotation of the motor 5 is stopped by the discharge timing detection unit 20.
Is output as a rotation pulse a. Further, the motor rotation detection unit 31 detects the motor rotation speed, that is, the value of the load current I from the sampling number e of the rotation pulse a (steps 113 to 115), and the first frequency divider 29 of the first frequency divider 29 is detected according to the magnitude of the current I. The frequency division rate is switched to either decimal or seventh (steps 116 to 119), the stored value in the counter 21 is subtracted at a rate according to the magnitude of the consumed current (step 120), and the subtracted state is displayed. It is displayed on the section 22 (step 121).

When charged at time t ₅ where the charge amount display is integrated in the storage value of the time t ₅ rather than starting from scratch, thus always present charge amount is displayed continuously. Further, as a result of the actual current consumption being larger than the subtraction amount, if the terminal voltage of the battery 6 drops to 1.0 V or less despite the numerical value remaining in the counter 21, counting is performed in step 109. forcibly resets the value (time t ₇₎ to stop the display (step 122), it is to encourage charge to the user.

It should be noted that the display by the display unit 22 may be directly displayed by numbers using liquid crystal instead of the light emitting diode 47, or may be displayed more finely and continuously. Further, instead of or in addition to the visual display, it is possible to display the charged amount by sound. That is, when the charged amount approaches the set value during the charging period, the intermittent sound starts to be generated, and as the charging further progresses, the sound generation interval or frequency is changed so that the charged state can be audibly confirmed.

Furthermore, the pulse signal generator 15 may be a charging pulse generator only and dedicated to charging. In this case, it goes without saying that the frequency dividing section 28 is not particularly required. A pulse switching unit 27 including a plurality of pulse generators 23, 24, 25
Instead of switching and using, the frequency of one pulse generator may be changed according to the detection of the charge or discharge state. When the current change during the discharge period is small, it is not necessary to change the frequency division ratio of the first frequency divider 29 to correct it.

In addition, the display unit 22 does not always emit light during the charging and discharging periods, but a battery check switch is separately provided to display only when the switch is operated, so that the power consumption of the display unit 22 is minimized. be able to.

Further, it is of course possible to cause the display circuit 14 to perform the same operation by a program using a microprocessor. In this case, the charge, discharge and self-discharge pulses are
It is displayed in a binary number corresponding to the magnitude of the amount of current, and is added / subtracted directly to / from the stored value of the storage unit 21 every predetermined period.

〔The invention's effect〕

As described above, according to the present invention, the charging voltage is applied to the battery 6 to be charged to generate a pulse signal for charge display corresponding to a period in which charging is actually performed, and the number of pulses is calculated. Since the data is accumulated and stored, even if an accident such as a power failure occurs on the way, the pulse signal integration is interrupted during that period, and there is no erroneous memory, and the amount of charge is accurate The display is done.

Furthermore, after confirming that the terminal voltage of the battery 6 has exceeded the initial charging voltage setting value, by starting counting in the storage unit 21, even if the charging characteristics of the battery change due to repeated charging, It is possible to prevent erroneous memory by not counting the charging flow at the beginning of charging, and to display the capacity that corresponds appropriately to the charging capacity according to the actual life change.

[Brief description of drawings]

FIG. 1 is a perspective view of an electric shaver showing an example of implementing the present invention, FIG. 2 is a schematic view showing a basic configuration of the present invention, FIG. 3 is a block diagram showing a configuration of an electric circuit, and FIG. Is a graph showing the relationship between the motor speed and the load current, FIG. 5 is a graph showing the relationship between the motor speed and the drivable time, and FIG.
(a) to (g) are waveform charts for explaining the operation of the motor rotation speed detector, FIG. 7 is a flow chart for explaining the operation, and FIGS. 8 (a) and 8 (b) are the battery terminal voltage during charging and discharging. It is explanatory drawing which shows the relationship with the memory value of a memory | storage part. 5 ... Motor 6 ... Battery 11 ... Charging circuit 15 ... Pulse signal generator 18 ... Voltage detector 19 ... Charge timing detector 20 ... Discharge timing detector 21 ... Memory 22 ... Display 28: Frequency divider 31: Motor rotation speed detector

Continuation of the front page (56) References JP-A-52-153126 (JP, A) JP-A-56-94934 (JP, A) Actually developed JP-A-56-83948 (JP, U)

Claims (1)

[Claims] 1. A pulse signal generator (15) that outputs a pulse signal corresponding to a period of application of a charging voltage to a battery (6), and a storage unit (21) that sequentially accumulates and stores the number of input pulse signals.
And a display unit (22) for displaying the stored value in the storage unit (21) according to the magnitude of the stored value. The storage value in the storage unit (21) is calculated by calculating the terminal voltage of the battery 6 as the initial charging voltage. A charge amount display circuit, which is performed after the set value is exceeded.