JPH0797892B2 - Charge amount display circuit - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention 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.

[0002]

2. Description of the Related Art Heretofore, a display circuit of this type has generally been a display circuit for indicating whether or not charging is performed exclusively by turning on a light emitting diode in association with the start of charging.
An attempt has also been made to continuously display the charge amount using an up / down counter (for example, Japanese Patent Laid-Open No. Sho 56-56).
94934).

[0003]

However, if only the charging time is displayed, it is obvious at a glance that the device is set in the outlet, so it only plays the role of an alarm to prevent overcharging. , It is not so much needed as a charge indicator. On the other hand, by simply adding and subtracting the count value of the counter according to the charging and discharging,
Accumulation of errors makes it difficult to perform accurate capacity display.

The present invention has been made in view of the above problems, and provides a charge amount display circuit that maintains accurate charge amount display with a relatively simple structure and suppresses power consumption as much as possible. The purpose is to provide.

[0005]

Charge level display circuit according to the present invention, in order to solve the problems], as shown the schematic configuration in FIG. 1, the battery
The charging timing signal s corresponding to the charging timing is generated.
The power timing detection means and
And a no-load state detecting means for generating a no-load signal f,
When both the charging timing signal s and the no-load signal f are present
The charging pulse signal corresponding to the amount of charge in the pond is set to the above charging time.
Discharge of load when there is no signal s and no load signal f
The main discharge pulse signal corresponding to the amount
Self-discharge amount when there is no load and there is no load signal f
Pulse signals that generate self-discharge pulse signals corresponding to
Signal generation means and reset when the terminal voltage of the battery falls below the set value.
Reset signal generating means for generating a reset signal r, and
Resets the integrated value corresponding to the input of set signal r
The input value of the above charging pulse signal
Main discharge pulse signal or self-discharge pulse while adding
Storage means for subtracting the integrated value in response to signal input
And a display corresponding to the integrated value in the storage means.
Display means .

Further, the display on the display means is
No charge timing signal s is generated, but no load signal f is generated.
It is characterized in that it is stopped when

[0007]

With the above-described structure, during normal load driving, the stored value in the storage means is stored at a relatively fast rate .
Subtract with the discharge pulse signal . Here, even if the load driving is stopped, the battery self-discharges or the charged amount is gradually decreased to maintain the minimum function of the device. Therefore, the slow rate corresponding to this self-discharge
With the self-discharge pulse signal of the pulse rate, the self -discharge amount is corrected by continuing to subtract the stored value in the storage means even when the device is not used.

Further, when this self-discharging starts, no load is applied.
The state detection means detects the inoperative state of the load and
If the power timing detection means detects that charging is not in progress, the display means
The display at is forcibly stopped .

[0009]

EXAMPLE An example in which the present invention is applied to the electric shaver 1 shown in FIG. 2 will be shown below, but the present invention is not limited to this, and a tape winder,
Of course, the same can be applied to a charging circuit in various rechargeable small electric devices such as a flashlight.

The electric shaver 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. A motor 5 for reciprocating the inner blade 4 and a battery 6 for supplying electric power to the motor 5 are housed inside the case 2.

The battery 6 is a secondary battery such as a nickel-cadmium battery that can withstand charging and discharging a plurality of times. In this embodiment, an AA battery having a battery capacity of about 500 mAh is used and a main body case is used. A charging unit 7 is provided below the battery 2, so that the battery 6 can be directly charged from a 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 it can be retracted and retracted. As shown in FIG. 3, a commercial AC voltage input from the plug blade 9 is supplied to a predetermined charging circuit 11 including an inverter circuit. Convert to charging voltage. Further charging circuit 1
The output side of 1 is connected in series with a battery 6 and a switching unit 12 that controls the timing of energization of the battery 6.

The switching section 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 timing. Therefore, the charging circuit 1
When the commercial AC voltage is applied to 1 and the diode 16 is turned on, 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.

At both ends of the battery 6, a DC-DC converter 17 for supplying a predetermined DC voltage to the electronic circuit described below, and the terminal voltage of the battery 6 are lowered to, for example, 1.0 V or less so that the battery 6 is completely discharged. When it is detected, the reset signal r is generated and all circuits are connected, especially the voltage detection unit 18 for returning the count value of the storage unit 21 to the initial state. Furthermore, 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,
The timing of energization from the battery 6 to the motor 5 is regulated in conjunction with the on / off operation of the main switch 13.

Further, the charging timing of the battery 6, the driving timing of the motor 5 and the stopping timing of the electric razor 1 are respectively detected, and the charge amount in the battery 6 is displayed on the display circuit 14.

FIG. 1 shows an outline of the display circuit 14, in which the generation rate and the generation timing of the pulse output from the pulse signal generation section 15 are determined by the charging timing detection section 1.
9 and the detection signal output from the discharge timing detection unit 20, the number of output pulses generated is added and stored in the storage unit 21 during charging, and conversely, the stored value in the storage unit 21 is stored during discharging. By subtracting at a rate proportional to the load current I, it is always stored in the storage unit 21 as a numerical value proportional to the current capacity of the battery 6, and the storage unit 2
The integrated value within 1 is appropriately output to the display unit 22 so that the current value of the charge amount can be displayed.

That is, in the secondary battery 6 of this type, the amount of charging current is normally set so that the terminal voltage drops to 1.0 V or less and the capacity is completely exhausted and the battery is fully charged in about 8 hours. To be done. 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. Further, even when the motor 5 is stopped, the capacity of the battery 6 gradually decreases due to the maintenance current of the circuit and self-discharge.

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

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 storage unit 2
The generation rate of the charging pulse output from the pulse signal generator 15 is set so that the pulse count number in 1 reaches the set value in 8 hours.

On the other hand, when the electric razor 1 is used, that is, when the battery 6 is discharged, the output signal s from the charge timing detection section 19 is inverted, and the storage section 21 becomes a down counter contrary to the above. Here, the pulse signal generation unit 15 and the storage unit 21
By arranging the frequency dividing unit 28 having a variable frequency dividing ratio between them and changing the frequency dividing ratio of the frequency dividing unit 28 in accordance with the discharge current amount,
The total number of pulses accumulated at the time of charging and stored in the counter 21 is subtracted by a variable discharge pulse having a frequency higher than that at the time of charging and corresponding to the amount of load current, and the amount of charge currently stored in the battery 6 is subtracted. A value proportional to is constantly stored in the storage unit 21. Therefore, the stored value is displayed on the predetermined display unit 2.
By displaying in 2, the current capacity of the battery 6 can be continuously grasped.

In the normal charging circuit, it is sufficient to consider only the above charging and motor driving, but in this embodiment, the value stored in the storage unit 21 is held even when the motor 5 is stopped. , It consumes a little current.
Therefore, in order to correct the current, a self-discharge pulse that is output at an extremely long time interval is generated when the electric shaver 1 is not used, and the stored value in the storage unit 21 is subtracted by this pulse, and a display is performed during that period. The display of the section 22 is forcibly stopped.

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

The pulse switching section 27 is constructed by combining a plurality of logic gate circuits, for example, and the charge timing detecting section 1 is formed by shaping the waveform of the output of the charging circuit 11.
The charging timing signal s extracted from 9 and the application of the zero rotation detection signal f output from the motor rotation speed detection unit 31 to be described later and indicating the stop time of the motor 5 are switched in association with each other. That is, when both the charging timing signal s and the zero rotation detection signal f are "1", the charging pulse generator 23 is selected,
When both are "0", the main discharge pulse generator 24 is selected, and when only the zero rotation detection signal is "1", the self-discharge pulse generator 25 is selected and connected to the frequency divider 28. It

The frequency divider 28 is provided with a first frequency divider 29 composed of a four-stage binary counter and a second frequency divider 30 composed of a six-stage binary counter, which are connected in series. The pulse signal input to the frequency divider 29 has a maximum generation rate of 1/2 ¹⁰ at the output side of the second frequency divider 30, that is, 1/1024.
It is divided and taken out.

Further, when the up / down counter of the storage unit 21 used as a memory of the charge amount is constituted 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, and when the counting of the 255th pulse is finished, charging is stopped. 8 hours = 2.8 × 10
^Since it is ⁴ seconds, the pulse rate P1 of the charging pulse output from the charging pulse generator 23 is P1 = 2.8 × 10
⁴ / (255 × 1024) = 0.1 [seconds], and by generating one pulse from the charging pulse generator 23 about every 0.1 seconds, the counter of the storage unit 21 becomes an 8-hour timer. I understand.

On the other hand, in this type of small electric equipment, the motor 5
A DC motor using a permanent magnet for the field is often used as a magnetic field. Therefore, as shown in FIG. 4, the load supplied to the motor 5 at the time of driving as the torque T increases due to the accumulation of hair dust. The current I increases. Further, such an increase in the load current I appears as a decrease in the motor rotation speed n. Therefore, by detecting the increase or decrease in the motor rotation speed n, the increase or decrease in the load current I can be indirectly known. The increase in the load current I leads to a decrease in the continuous driveable time of the motor 5 from the time of full charge, but the battery 6 and the motor 5
If the capacity is set, the relationship between the motor rotation speed n and the continuous drive possible time of the motor 6 can be obtained by experiment or calculation.

The curve shown by the solid line in FIG. 5 shows an example of this relationship, and the broken line shows the curve approximated by a stepwise straight line. From this result, the motor 5
The motor rotation speed detection unit 31 detects the magnitude of the rotation speed n of
By changing the frequency dividing ratio of the frequency dividing unit 28 stepwise according to the detection value of the rotation speed detecting unit 31, the pulse rate is approximated to the increase / decrease of the load current I from the output terminal of the frequency dividing unit 28. A changing main discharge pulse is obtained, and the stored value in the storage unit 21 is subtracted by using the main discharge pulse.
The value in the storage unit 21 can be reduced at a rate according to the load current I.

The discharge timing detection unit 20 detects, with the detection coil 32, a leakage magnetic flux generated from the armature when the motor 5 rotates or a magnetic flux change caused by a magnet (not shown) integrally attached to the rotation shaft of the motor 5. After this detection signal is waveform-shaped by the Schmitt trigger 33,
As shown in (d), a rotation pulse a having a pulse rate proportional to the rotation speed n of the motor 5 is formed and input to the motor rotation detector 31.

The motor rotation detecting section 31 includes a rotation number counting section 34 that samples and counts the number of rotation pulses a for a set time, and a rotation number determining section 36 that determines the magnitude of the count number in the counting section 34. Composed of the first
The conversion signal g output from the rotation speed determination unit 36 is input to the frequency division ratio conversion unit 37 combined with the frequency divider 29, and the first
The frequency division ratio of the frequency divider 29 is changed.

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. Self-discharge pulse c output from the discharge pulse generator 25
Is differentiated by a differentiating circuit 41 to generate a trigger signal d, and the signal d is used to clear the counter 39 and regulate the generation timing of the gate signal b. That is, as shown in FIG. 6A, every time one self-discharge pulse c is output, the signal c is differentiated by the differentiating circuit 41 to generate the trigger signal d (FIG. 6B).
reference). Such a trigger signal d resets the content e of the rotation speed counter 39 as shown in FIG. 6 (f) and at the same time operates the monostable multivibrator 40, and the gate signal b output from the monostable multivibrator 40 causes the counter 39 to operate. The gate is opened and the pulse number of the rotation pulse a output from the discharge timing detection unit 20 is sampled (see FIG. 6 (e)).

In the present embodiment, a rotation number counter 39 having a four-stage binary number 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 3 is rotated at the rotation speed shown in FIG.
The count number e of 9 is "15", "14" when 4700-5100 rotations, "13" when 4300-4700 rotations, 43
It can be set to be "12" or less at 00 rotations or less. Here, further, the count number of the rotation speed counter 39 is "15".
Assuming that the drivable time at this time is "10", the drivable time is reduced by 10% each time the count number in the rotation speed counter 39 decreases by one, so basically it is a binary four-stage hexadecimal number. The frequency division ratio of the 1-frequency divider 29 is calculated by the rotation speed counter 39.
When the count number of "15" is "15", the load current I
A discharge pulse having a pulse rate corresponding to the magnitude of is obtained.

Further, when the total count value "255" counted by the up / down counter of the storage unit 21 during the charging period for 8 hours corresponds to the case where the first frequency divider 29 is switched to decimal, at the time of discharging. , The discharge pulse rate P2 may be set so that it becomes "0" in about 38 minutes. The pulse rate P2 is P2 = 38 × 60 / (10 × 64 × 255) = 0.014 [sec], and the pulse rate for the main discharge pulse generator 24 is about 0.01.
It is understood that one pulse should be generated every 4 seconds.

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 the frequency divider 28
The stored value in the storage unit 21 is subtracted by being applied to the storage unit 21 via the, and the decrease in the battery capacity due to the circuit holding current flowing when the device is stopped is corrected.

The decrease in the battery capacity due to such a current is such that the charged amount becomes zero in about 2 months from the fully charged state. Therefore, the pulse rate P3 of the self-discharge pulse c
Since 2 months are 5.2 × 10 ⁶ seconds, P3 = 5.2 × 10 ⁶ / (255 × 1024) = 20 [seconds], and from the self-discharge pulse generator 25 about every 20 seconds. The self-discharge pulse c is output every 1 pulse.

The zero rotation detecting section 43 provided on the output side of the rotation number counting section 34 outputs a "1" signal when the sampling number e in the rotation number counter 39 is "0", that is, when the rotation of the motor 5 is stopped. Let The zero signal f is input to the pulse switching unit 27, and the charging timing signal s is "0".
The pulse generator is switched to the self-discharge pulse generator 25 side in conjunction with the signal, and at the same time, it is inverted by the inverter 44 and becomes "0", which is input to the display drive unit 45, thereby stopping the motor 5. At times, the display 46 is turned off to suppress the power consumption of the display unit 22.

The display drive section 45 takes out the upper 4 bits of the storage section 21 as a data signal, decodes the hexadecimal number displayed by the binary 4 digits, and displays it on the display 46. The display 46 is configured by arranging four light emitting diodes 47 in the center of the front surface 8 of the main body case 2, and increases or decreases the number of emitted lights of the four light emitting diodes 47 according to the stored value in the storage unit 21. . For example, at the time of charging, 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 four light emitting diodes 47 are turned on and charged. Is displayed, all the 8 bits of the storage unit 21 become zero and a carry signal is output at the same time, and the output signal for driving the light emitting diode from the display drive unit 45 disappears. At this time, the switching unit 12 for regulating the charging timing 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 and prevent overcharging.

Next, referring to FIGS. 7 and 8, the flow of operation in the above-mentioned configuration will be described. When charging is started at time t0, it is determined in step 101 that charging has started, the counter of the storage unit 21 is switched to the up side (step 102), and at the same time, the terminal voltage of the battery 6 gradually rises. However, when 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” state is maintained. .
Only when it is determined that the battery voltage exceeds 1.0 V at time t1, the storage unit 21 starts counting the charging pulse with reference to the time t1 (step 10).
5) Further, the count state is displayed on the light emitting diode 47 of the display unit 22 (step 106).

When the charging is continued for about 8 hours from the time t1, 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.

At time t2, the plug blade 9 is removed from the outlet to stop charging, and at the same time, it is determined in step 101 that charging has been stopped, and the storage unit 21 is switched to the down side (step 107). At this time, if the terminal voltage of the battery 6 is 1 V or less, the count value of the storage unit 21 is reset in the same manner as described above (step 109).
When it is determined in step 108 that the value is V or more, the process proceeds to step 110, and it is determined whether or not the motor 5 is rotationally driven. At this time, if it is determined that neither charging nor motor driving is performed, the stored value 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 t3, the switch 13 is closed and the motor 5 is energized, and the rotation of the motor 5 is taken out as the rotation pulse a by the discharge timing detection unit 20.
Further, the motor rotation speed 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 according to the magnitude of the current I. The frequency division ratio is switched to either decimal or hex (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 the display unit 22
Is displayed (step 121).

When charging is performed at time t5, the charge amount display does not start from zero but is integrated into the stored value at time t5, and therefore the current charge amount is continuously displayed. Further, as a result of the actual current consumption being larger than the subtraction amount, if the terminal voltage of the battery 6 has dropped to 1.0 V or less even though there are numerical values remaining in the storage unit 21, in step 109. The count value is forcibly reset (time t7), the display is stopped (step 122), and the user is prompted to charge.

A plurality of pulse generators 23, 24, 2
Instead of using the pulse switching unit 27 for switching and using 5, the frequency of one pulse generator may be changed according to the detection of charging or discharging timing.

Further, the pulse rate of the discharge pulse at the time of discharge may be changed by changing the oscillation frequency itself of the main discharge pulse generator 24 instead of changing the frequency division rate of the first frequency divider 29. Good.

Further, the display by the display unit 22 may be a numerical display directly using liquid crystal instead of the light emitting diode 47, or the display 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 charge amount approaches the set value during charging, the intermittent sound starts to be generated, and as the charging further progresses, the sound generation interval or frequency is changed so that the charging state can be audibly confirmed. Further, the display unit 22 does not always display a light emission at the time of charging and discharging, but a battery check switch is separately provided to display only when the switch is operated, so that the power consumption by the display unit 22 can be minimized. it can.

Furthermore, it is of course possible to cause the display circuit to operate in a similar manner by a program using a microprocessor. In this case, the charge, main discharge, and self-discharge pulses are displayed in binary numbers corresponding to the magnitude of the amount of current, and are added / subtracted directly to / from the stored value of the storage unit 21 every predetermined period.

[0046]

As described above, the present invention provides a no-load state detecting means.
And the charging time detection means detect the self-discharge time of the battery
Since it is configured to stop the display on the display means ,
The self-discharge time is accurately detected, and battery consumption is effectively suppressed.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a basic configuration of the present invention.

FIG. 2 is a perspective view showing an example in which the present invention is applied to an electric shaver.

FIG. 3 is a block diagram showing an overall configuration of an electric circuit.

FIG. 4 is a graph showing the relationship between motor rotation speed and load current.

FIG. 5 is a graph showing the relationship between the motor rotation speed and the drivable time.

FIG. 6 is a waveform diagram illustrating an operation of a motor rotation speed detection unit.

7 is a flowchart illustrating the operation of FIG.

FIG. 8 is an explanatory diagram showing a relationship between a terminal voltage of a battery and a stored value of a storage unit during charging / discharging.

[Explanation of symbols]

 5 Motor 6 Battery 11 Charging Circuit 15 Pulse Signal Generator 19 Charge Timing Detector 20 Discharge Timing Detector 21 Memory 22 Display 23 Charging Pulse Generator 24 Main Discharge Pulse Generator 25 Self-Discharging Pulse Generator 28 min Circumferential part 31 Motor rotation speed detection part

 ─────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-56-28476 (JP, A) JP-A-50-140220 (JP, A) Practical application Sho-53-164387 (JP, U)

Claims (1)

[Claims] 1. A charging time corresponding to a charging time for a battery
The charging timing detection means for generating the signal s, and the no-load signal f corresponding to the detection of the no-load state for the load.
A no-load condition detecting means for generating a conductive when the charging timing signal s and the no-load signal f are both
The charging pulse signal corresponding to the amount of charge in the pond is set to the above charging time.
Discharge of load when there is no signal s and no load signal f
The main discharge pulse signal corresponding to the amount
Self-discharge amount when there is no load and there is no load signal f
Pulse signals that generate self-discharge pulse signals corresponding to
Signal generation means and a reset signal r is issued when the terminal voltage of the battery falls below a set value.
Corresponding to the reset signal generating means and the input of the reset signal r.
The input of the above-mentioned charging pulse signal
While adding the values, main discharge pulse signal or self-discharge pulse
Comprising storage means for subtracting the accumulated value in response to the input of the pulse signal, and a table <br/> shows means for performing display corresponding to the integrated value within the storage means, display on the display means, Generation of the charging timing signal s
A charge amount display circuit characterized by being stopped when there is no load signal f generated .