JPH04351430A - Charged amount indicating circuit - Google Patents

Abstract

PURPOSE:To realize accurate indication of current capacity of battery at the time of discharge and to suppress consumption of battery as low as possible. CONSTITUTION:A main discharge pulse signal and a self-discharge pulse signal are generated in response to the discharge timing and the discharge current amount of a battery 6 and these pulses are fed to a memory section 21. Number of input pulse signals is then subtracted from a value stored in the memory means 21 and a value is indicated at an indicating section 22 according to the stored value. Indication on the indicating section 22 is stopped forcibly only when the self-discharge pulses are being counted.

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 built into a small electric appliance.

0002

2. Description of the Related Art Conventionally, this type of display circuit has generally displayed only whether or not charging is being performed by lighting a light emitting diode in conjunction with the start of charging. Additionally, attempts have been made to display the amount of charge continuously using an up/down counter (for example,
(See Publication No. 94934).

0003

[Problem to be solved by the invention] However, if only the charging time is displayed, it will be obvious when the device is plugged into an outlet, so it will only serve as a warning to prevent overcharging. , it is not so necessary as a charging display. On the other hand, simply adding and subtracting the count value of the counter corresponding to charging and discharging is not enough.
Errors accumulate, making it difficult to accurately display capacity.

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 configuration and suppresses power consumption as much as possible. The purpose is to provide.

[0005]

[Means for Solving the Problems] A charge amount display circuit according to the present invention has a battery 6, as shown in its schematic configuration in FIG.
a storage section 21 for subtracting and storing the input number of pulse signals generated corresponding to the discharge state from the stored value when discharging; and a display corresponding to the magnitude of the stored value in the storage section 21. The display unit 22 is equipped with a display section 22 for performing the following operations.

Furthermore, the pulse signals counted in the storage unit 21 include pulse signals corresponding to main discharge during normal load driving, as well as pulse signals corresponding to self-discharge when the equipment is left unused. The present invention is characterized in that the display on the display section 22 is stopped when the self-discharge pulse signal is counted.

[0007]

[Operation] With the above-described configuration, during normal load driving, the stored value in the storage section 21 is subtracted at a relatively fast rate. Even if the load drive is stopped here, the battery 6 will self-discharge or the amount of charge will gradually decrease in order to maintain the minimum functionality of the device. Therefore, this self-discharge is corrected by continuing to subtract the stored value in the storage unit 21 even when the device is not in use, at a slow rate corresponding to this self-discharge.

Furthermore, at the same time, the display on the display section 22 is forcibly stopped to prevent power consumption and to indicate that the device is not in use.

[0009]

[Embodiment] An example in which the present invention is implemented in the electric shaver 1 shown in FIG. 2 will be shown below, but the present invention is not limited to this.
It goes without saying that the present invention can be implemented in substantially the same way for charging circuits in various small rechargeable electric devices such as flashlights.

An electric shaver 1 embodying the present invention is provided with an outer cutter 3 removably attached to the upper part of a main body case 2, an inner cutter 4 is disposed inwardly in the outer cutter 3 so as to be able to reciprocate, and Inside the case 2, a motor 5 for reciprocating the inner cutter 4 and a battery 6 for supplying power to the motor 5 are housed.

The battery 6 is a secondary battery such as a nickel-cadmium battery that can be charged and discharged multiple times. In this embodiment, an AA battery with a battery capacity of about 500mAh is used, and the main body case is A charging section 7 is disposed at the bottom of the battery 2, so that the battery 6 can be charged directly from a commercial AC power source.

The charging unit 7 has a plug blade 9 that can freely appear and retract from the lower end of the main body case 2, and as shown in FIG. Convert to charging voltage. Furthermore, charging circuit 1
A battery 6 and a switching unit 12 that regulates the timing of energizing the battery 6 are connected in series to the output side of the battery 1 .

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 face 8 of the main body case 2 for displaying charging time. Therefore, charging circuit 1
When the diode 16 is turned on by applying a commercial AC voltage to the battery 1, the switching section 12 is turned on in conjunction with this, and the battery 6 is connected to the charging circuit 11 to start charging.

Both ends of the battery 6 are connected to a DC-DC converter 17 that supplies a predetermined DC voltage to the electronic circuit described below, and a DC-DC converter 17 that supplies a predetermined DC voltage to the electronic circuit described below. When it is detected that , the reset signal r is generated to connect all the circuits, especially the voltage detection section 18 which returns the count value of the storage section 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 placed at the center of the front of the main body case 2.
In conjunction with the on/off operation of the main switch 13, the timing of energization from the battery 6 to the motor 5 is regulated.

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

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

In other words, the amount of charging current for this type of secondary battery 6 is normally set so that the terminal voltage drops to 1.0 V or less and the capacity is completely exhausted, so that the battery becomes fully charged in about 8 hours. be done. On the other hand, when discharging is performed using the motor 5 of the electric shaver 1 as a load, the capacity of the battery 6 is exhausted after approximately 40 minutes of continuous operation, although this varies 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 and self-discharge.

Therefore, the storage section 21 is configured with an up/down counter, and the terminal voltage of the battery 6 is compared with a set value in the voltage detection section 18, and while the terminal voltage is below the set value, the storage section 21 is configured with an up/down counter. A reset signal r is sent to maintain the count value in the storage section 21 at the initial value "0".

At the time of charging, the signal output from the charging time detection section 19 is inputted to the control terminal of the storage section 21 to turn the storage section 21 into an up counter, and the storage section 2
The generation rate of charging pulses 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 shaver 1 is used, that is, when the battery 6 is discharged, the output signal s from the charging time detection section 19 is inverted, and the storage section 21 becomes a down counter, contrary to the above. Here, the pulse signal generation section 15 and the storage section 21
By arranging a frequency dividing section 28 with a variable frequency division ratio in between, and changing the frequency division ratio of the frequency dividing section 28 in accordance with the amount of discharge current,
The total number of pulses accumulated during charging and stored in the counter 21 is subtracted by a variable discharge pulse that has a higher frequency than during charging and corresponds to the amount of load current, and calculates the amount of charge currently stored in the battery 6. A value proportional to is constantly stored in the storage unit 21. Therefore, such stored values are displayed on the predetermined display section 2.
By displaying the number 2, the current capacity of the battery 6 can be continuously grasped.

[0021] Note that in a normal charging circuit, only the above-described charging and motor driving times are a problem, but in this embodiment, the value stored in the storage unit 21 is retained even when the motor 5 is stopped. , consumes a small amount of current. In order to compensate for this current, self-discharge pulses are generated at extremely long time intervals when the electric shaver 1 is not in use, and the values stored in the memory section 21 are subtracted by these pulses. The display of section 22 is forcibly stopped.

To explain the above configuration with more specific numerical examples, the pulse signal generator 15 includes three sets of pulse generators 23 and 24 for charging, main discharge, and self-discharge.
25 and a pulse switching section 27, and the pulse switching section 27 selectively sends pulse signals at generation rates individually set for each pulse generator 23, 24, and 25 to the frequency dividing section 28.

The pulse switching unit 27 is configured by combining a plurality of logic gate circuits, for example, and performs waveform shaping on the output of the charging circuit 11 to change the charging timing detection unit 1.
The switching is performed in conjunction with the application of a charging timing signal s taken out from the motor 9 and a zero rotation detection signal f output from a motor rotation speed detection section 31 to be described later and indicating when the motor 5 is stopped. That is, when the charging timing signal s and the zero rotation detection signal f are both "1", the charging pulse generator 23 is selected,
If both are "0", the main discharge pulse generator 24 is selected, and if only the zero rotation detection signal is "1", the self-discharge pulse generator 25 is selected, and each is connected to the frequency dividing section 28. Ru.

The frequency divider 28 includes in series a first frequency divider 29 consisting of a four-stage binary counter and a second frequency divider 30 consisting of a six-stage binary counter. The pulse signal input to the frequency divider 29 is extracted at the output side of the second frequency divider 30 after its generation rate is divided by a maximum of 1/210, that is, 1/1024.

Furthermore, if the up/down counter of the storage section 21 used as a memory for the amount of charge is configured with eight binary stages, the maximum count will be 28-1, that is, 255. Here, when the upper 4 bits of the storage unit 21 become "1", that is, when 240 pulses have been counted, a full charge is displayed, and when the 255th pulse is counted, charging is stopped. 8 hours = 2.8 x 1
04 seconds, the pulse rate P1 of the charging pulse output from the charging pulse generator 23 is P1=2.8×
104/(255×1024)=0.1 [seconds],
It can be seen that by generating one pulse from the charging pulse generator 23 every approximately 0.1 seconds, the counter in the storage section 21 becomes an 8-hour timer.

On the other hand, this type of small electric equipment has a motor 5.
As shown in FIG. 4, as the torque T increases due to the accumulation of hair, etc., the load supplied to the motor 5 during driving increases. Current I increases. Furthermore, such an increase in load current I appears as a decrease in motor rotational speed n, and therefore, by detecting an increase or decrease in motor rotational speed n, an increase or decrease in load current I can be indirectly determined. Also, load current I
An increase in n will lead to a decrease in the continuous drive time of the motor 5 after full charge.However, if the capacity of the battery 6 and motor 5 is set, it can be determined by experiment or calculation that the motor rotation speed n and the continuous drive time of the motor 6 The relationship with drivable time is determined.

The solid curve shown in FIG. 5 shows an example of such a relationship, and the broken line approximates the curve with a stepped straight line. From this result, motor 5
The motor rotation speed detection unit 31 detects the magnitude of the rotation speed n,
By changing the frequency division ratio of the frequency dividing section 28 in a stepwise manner according to the detected value of the rotation speed detecting section 31, the pulse rate from the output terminal of the frequency dividing section 28 approximates the increase/decrease in the load current I. By obtaining a changing main discharge pulse and subtracting the stored value in the storage unit 21 using this main discharge pulse,
The value in the storage section 21 can be decreased at a rate according to the load current I.

The discharge timing detection unit 20 uses a detection coil 32 to detect leakage magnetic flux generated from the armature when the motor 5 rotates, or a change in magnetic flux caused by a magnet (not shown) integrally attached to the rotating shaft of the motor 5. Also, by waveform-shaping this detection signal with the Schmitt trigger 33, the result shown in Fig. 6 (
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 detection section 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 counted number in the counting section 34. 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 number counting section 34 includes a rotation number counter 39 having a four-stage binary sampling function, and a monostable multivibrator 40 that generates 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, which clears the counter 39 and regulates the generation timing of the gate signal b. That is, as shown in FIG. 6(a), 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. 6(b)).
reference). The trigger signal d resets the content e of the rotation number counter 39 as shown in FIG. The gate is opened and the number of rotation pulses a output from the discharge timing detection section 20 is sampled (see FIG. 6(e)).

In this embodiment, a four-stage binary number counter 39 is used, and is configured so that rotation pulses a corresponding to sampling numbers in the range of 0 to 15 can be detected. Therefore, by appropriately selecting the pulse rate of the rotational pulse a output from the discharge timing detection section 20 and the pulse width of the monostable multivibrator 40, the rotational speed counter 3 can be detected when the rotational speed shown in FIG.
The count number e of 9 is "15", "14" at 4700-5100 revolutions, "13" at 4300-4700 revolutions, 43
It can be set so that it becomes "12" or less at 00 revolutions or less. Furthermore, the count number of the rotation number counter 39 is "15".
If the drivable time is set to "10", the drivable time decreases by 10% each time the count number in the revolution counter 39 decreases by 1. 1 The frequency division rate of the frequency divider 29 is determined by the rotation number counter 39.
The load current I
A discharge pulse with a pulse rate corresponding to the magnitude of the discharge pulse can be obtained.

Furthermore, the total count value "255" counted over 8 hours during the charging period by the up/down counter in the storage section 21 is calculated at the time of discharging corresponding to the case where the first frequency divider 29 is switched to decimal. , the discharge pulse rate P2 may be set so that it becomes "0" over about 38 minutes. The pulse rate P2 is as follows: P2=38×60/(10×64×255)=0.
0.014 [seconds], and it is understood that the main discharge pulse generator 24 should generate one pulse approximately every 0.014 seconds.

On the other hand, when the plug blade 9 is pulled out from the outlet to stop charging the battery 6, the pulse switching section 27 switches to the self-discharge pulse generator 25 side, and the self-discharge pulse c output from the pulse generator 25 is switched to the self-discharge pulse generator 25 side. is the frequency dividing section 28
The voltage is applied to the storage unit 21 through the subtracter, and the stored value in the storage unit 21 is subtracted, thereby correcting the decrease in battery capacity due to the circuit holding current that flows when the device is stopped.

The reduction in battery capacity due to such current is such that it takes about two months from a fully charged state until the amount of charge reaches zero. Therefore, the pulse rate P3 of the self-discharge pulse c
Since two months is 5.2 x 106 seconds, P3=
5.2×10 6 /(255×1024)=20 [seconds], and the self-discharge pulse generator 25 outputs a self-discharge pulse c at a rate of 1 pulse approximately every 20 seconds.

The zero rotation detection unit 43 provided on the output side of the rotation number counter 34 outputs a signal “1” when the sampling number e in the rotation number counter 39 is “0”, that is, when the rotation of the motor 5 has stopped. let This zero signal f is inputted to the pulse switching section 27, and the charge timing signal s described above is
The pulse generator is switched to the self-discharge pulse generator 25 side in conjunction with the 0'' 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, so that the motor 5 When the display unit 22 is stopped, the display unit 46 is turned off to suppress power consumption by the display unit 22.

The display driving section 45 takes out the upper four bits of the storage section 21 as a data signal, decodes the hexadecimal number displayed in four binary digits, and displays it on the display 46. The display device 46 is constructed by arranging four light emitting diodes 47 at the center of the front surface 8 of the main body case 2, and increases or decreases the number of light emitted from the four light emitting diodes 47 in accordance with the stored value in the storage section 21. . For example, during charging, the number of light emitting diodes 47 is increased by one every two hours from the start of charging, and when the upper 4 bits in the memory section 21 are all set to "1", all four light emitting diodes 47 are lit and charging starts. The completion of the display is displayed, and charging continues until all 8 bits of the storage section 21 become zero, at the same time a carry signal is output and all output signals for driving the light emitting diodes from the display drive section 45 disappear. At this time, the switching unit 12 for regulating the charging timing of the secondary battery 6
Since it is connected to the light emitting diode 16 for displaying charging time, the switching unit 12 is turned off to forcibly stop charging the battery 6 and prevent overcharging.

Next, the flow of operations in the above configuration will be explained with reference to FIGS. 7 and 8. When charging is started at time t0, it is determined in step 101 that charging has started, and at the same time the counter in the storage section 21 is switched to the up side (step 102), the terminal voltage of the battery 6 gradually increases. However, the terminal voltage of battery 6 is 1
．． If it is determined in step 103 that the voltage is below 0V, the count value in the storage unit 21 is reset (step 104) and maintains the initial value of "0". Here, only when it is determined that the battery voltage exceeds 1.0V at time t1, the storage unit 21 starts counting charging pulses using the time t1 as a reference (step 105).
), and further displays the count status on the light emitting diode 47 of the display unit 22 (step 106).

When charging continues for about 8 hours from time t1, all four display light emitting diodes 47 light up, indicating that the battery 6 has reached full charge. Even if the charging state is continued, the output of the display section 22 is cut off after a predetermined period of time has elapsed, the switching section 12 is opened, and overcharging of the battery 6 is prevented.

At time t2, when the plug blade 9 is removed from the outlet and charging is stopped, it is determined in step 101 that charging has been stopped, and the storage section 21 is switched to the down side (step 107). At this time, if the terminal voltage of the battery 6 is 1V or less, the count value of the storage section 21 is reset in the same manner as described above (step 109), but
If it is determined in step 108 that the voltage is equal to or greater than V, the process moves 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 being performed, the stored value in the storage unit 21 is subtracted at a rate sufficiently lower than when discharging, and the power consumption when the device is not in use is corrected (step 111). ). At the same time, in step 112, the light emitting display on the display section 22 is stopped, and power consumption is kept to the minimum necessary for saving the stored value in the storage section 21.

Next, at time t3, when the switch 13 is closed and the motor 5 is energized, the rotation of the motor 5 is detected by the discharge timing detection section 20 as a rotation pulse a. 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 detects the value of the load current I according to the magnitude of the current I. The frequency division ratio is switched to either decimal or septal (steps 116 to 119), and the value stored in the counter 21 is subtracted at a rate corresponding to the magnitude of current consumption (step 120), and the subtraction state is is the display section 22
(Step 121).

When charging is performed at time t5, the charge amount display does not start from zero, but is integrated with the stored value at time t5, and therefore the current charge amount is displayed continuously. In addition, if the actual current consumption is larger than the subtraction amount and the terminal voltage of the battery 6 drops to 1.0V or less even though the value remains in the storage unit 21, step 109 is performed. The count value is forcibly reset (time t7), the display is stopped (step 122), and the user is prompted to charge the battery.

Note that a plurality of pulse generators 23, 24, 2
5, and the pulse generator 27 switches the frequency of one pulse generator in accordance with the charging or discharging timing detection.

Furthermore, the pulse rate of the discharge pulse during discharge can be changed by changing the oscillation frequency itself of the main discharge pulse generator 24 instead of changing the frequency division ratio of the first frequency divider 29. good.

Furthermore, the display section 22 may directly display numbers using a liquid crystal instead of the light emitting diode 47, or may display more finely and continuously. Furthermore, in place of or in addition to the visual display, it is also possible to display the amount of charge audibly. That is, when the charging amount approaches a set value during charging, the intermittent sound starts to be generated, and as charging progresses, the interval or frequency of the sound is changed, so that the charging state can be confirmed audibly. Furthermore, the power consumption by the display section 22 can be minimized by providing a separate switch for battery checking and displaying the display only when the switch is operated, instead of displaying the display section 22 by constantly emitting light during charging and discharging. can.

Furthermore, it is of course possible to cause the display circuit described above to operate in a similar manner through a program using a microprocessor. In this case, the charging, main discharge, and self-discharge pulses are displayed as binary numbers corresponding to the magnitude of the current amount, and are directly added to or subtracted from the stored value in the storage unit 21 at predetermined intervals.

[0046]

[Effects of the Invention] As described above, the present invention provides, in addition to the main discharge,
Since it is configured to subtract and correct the stored value in response to self-discharge, the current capacity of the battery can be displayed more accurately. Furthermore, since the display on the display section 22 is forcibly stopped during correction due to self-discharge, consumption of the battery 6 is suppressed as much as possible.

[Brief explanation of drawings]

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

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

FIG. 3 is a block diagram showing the 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 motor rotation speed and drivable time.

FIG. 6 is a waveform diagram illustrating the operation of a motor rotation speed detection section.

FIG. 7 is a flowchart explaining the operation of FIG. 3;

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

[Explanation of symbols]

5 Motor 6 Batteries 11 Charging circuit 15 Pulse signal generation section 19 Charging time detection section 20 Discharge time detection section 21 Memory section 22 Display section 23 Charging pulse generator 24 Main discharge pulse generator 25 Self-discharge pulse generator 28 Frequency dividing section 31 Motor rotation speed detection section

Claims (1)

[Claims] [Claim 1] The main discharge and self-discharge pulse signals generated in accordance with the discharge timing and discharge current amount of the battery (6) and the number of inputs of both discharge pulse signals are subtracted from the stored values. A storage unit (21) for storing information, and a storage unit (21) for storing information.
) Display section (22
), the above-described self-discharge pulse storage unit (21)
A charge amount display circuit characterized in that the display on the display section (22) is stopped at the time of counting.