JPH0578252B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a charge amount display circuit, and particularly to a circuit suitable for displaying a display corresponding to the discharge state of a secondary battery built in a small electric device.

[Prior Art] Conventionally, this type of display circuit is capable of displaying a display corresponding to the current capacity of the battery by A/D converting the amount of discharge current and integrating the digitized amount of current. is known (for example, see Japanese Unexamined Patent Publication No. 56-28476).

[Problem to be solved by the invention] However, in the case of the method of digitally integrating the amount of current discharged with respect to the current capacity,
If drastic changes in load current cannot be avoided,
The larger the fluctuation, the larger the maximum value for integration needs to be set, and for electrical equipment such as electric shavers that have frequent load fluctuations and frequent starts and stops, the memory capacity required increases.
The problem was that the configuration was complicated.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a charge amount display circuit that can accurately display capacity regardless of fluctuations in discharge current amount while maintaining a relatively simple configuration. shall be.

[Means for Solving the Problems] The charge amount display circuit according to the present invention, as shown in its schematic configuration in FIG. The signal generator 15 divides the pulse signal output from the pulse signal generator 15 according to a frequency division ratio set in multiple stages corresponding to the amount of discharge current of the battery 6 to obtain a predetermined pulse rate. A frequency dividing unit 28 that forms a discharge pulse, a storage unit 21 that sequentially integrates and stores the number of input discharge pulses, and a display unit 22 that displays the remaining charge amount in correspondence with the magnitude of the stored value in the storage unit 21. It is equipped with

The frequency division ratio at each stage that is changed in the frequency dividing section 28 described above is determined by approximating the discharge characteristic indicating the relationship between the discharge current amount of the battery 6 and the discharge connection time in a stepwise manner, as illustrated in FIG. 5, for example. It is set according to the value.

[Function] With the above-described configuration, the pulse signal with a constant frequency outputted from the pulse signal generating section 15 in accordance with the discharge timing of the battery 6 is divided into a rate corresponding to the amount of load current in the frequency dividing section 28. As a result, a value corresponding to the accumulated value is displayed on the display section 22. As a result, a display corresponding to the current capacity of the battery 6 is displayed. It will be done.

Here, when the magnitude of the load current fluctuates, the frequency division ratio of the frequency dividing section 28 changes stepwise in response to this fluctuation, but this frequency division ratio approximates, for example, the discharge characteristics of the battery 6 in a stepwise manner. Since it is set in advance in correspondence with the processed value, the integrated value in the storage unit 21 is corrected in accordance with the rate of decrease in battery capacity, and the capacity is displayed in accordance with the current capacity.

[Example] An example in which the present invention is implemented in the electric shaver 1 shown in FIG. 1 will be shown below, but the present invention is not limited to this, but substantially the same can be applied to charging circuits in various small rechargeable electric devices such as deep winders and flashlights. Of course, it can be implemented.

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

The battery 6 is a nickel cadmium battery,
This is a secondary battery that can withstand charging and discharging multiple times, and in this embodiment, an AA battery with a battery capacity of about 500 mAh is used, and a charging section 7 is provided at the bottom of the main body case 2, and a commercial AC power supply is used. The battery 6 can be charged directly from the battery 6.

The charging part 7 has a plug blade 9 at the bottom end of the main body case 2.
As shown in FIG. 3, a charging circuit 11 including an inverter circuit converts the commercial AC voltage input from the plug blade 9 into a predetermined charging voltage. Further, on the output side of the charging circuit 11, a battery 6 and a switching unit 1 for regulating the timing of energization of the battery 6 are provided.
2 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 face 8 of the main body case 2 for displaying charging time. Therefore, when a commercial AC voltage is applied to the charging circuit 11 and the diode 16 is turned on, the switching unit 12 is turned on in conjunction with this, and the battery 6 is connected to the charging circuit 11 to start charging. There is.

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 detected,
Generates a reset signal r to reset all circuits, especially the memory section 2.
Voltage detection unit 18 that returns the count value of 1 to the initial state
Connect with. Furthermore, both ends of the battery 6 are connected to both ends of the motor 5 via a main switch 13 placed in the center of the front of the main body case 2, and power is supplied from the battery 6 to the motor 5 in conjunction with the on/off operation of the main switch 13. The timing is regulated.

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

The display circuit 14 displays the generation rate and timing of the pulses output from the pulse signal generator 15.
It can be controlled by the detection signals output from the charging timing detection section 19 and the discharging timing detection section 20, and the number of output pulses generated is stored in the storage section 21 during charging.
By adding and storing the value in the storage unit 21 and subtracting it at a rate proportional to the load current I during discharging, the value stored in the storage unit 21 is always kept proportional to the current charge amount of the battery 6. The calculated value in the storage section 21 is outputted to the display section 22 as appropriate, so that the current value of the charge amount can be displayed.

That is, the amount of charging current for this type of secondary battery 6 is normally set so that the battery reaches a fully charged state in about 8 hours after the terminal voltage drops to 1.0 V or less and the battery is completely depleted. 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 about 40 minutes of continuous operation, although this varies depending on the discharge current value. Furthermore, even when the motor 5 is stopped, the battery 6 is damaged due to the circuit's maintenance current and self-discharge.
capacity will gradually decrease.

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 by the voltage detection section 18, and while the terminal voltage is lower than the set value, a reset is made in the storage section 21. A 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 use the storage section 21 as an up counter, and when the pulse count number in the storage section 21 reaches the set value in 8 hours. The generation rate of charging pulses output from the pulse signal generator 15 is set so that the charging pulses are outputted from the pulse signal generating section 15 so as to reach the following values.

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 generator 1
5 and the storage unit 21, and by changing the frequency division ratio of the frequency division unit 28 in accordance with the discharge current amount, the counter 21 is integrated at the time of charging. The total number of pulses stored in the battery 6 is subtracted by a variable discharge pulse whose frequency is higher than that during charging and corresponds to the amount of load current, and a value proportional to the amount of charge currently stored in the battery 6 is constantly stored in the memory. 2
1 is stored. Therefore, by displaying such stored values on the predetermined display section 22, the current capacity of the battery 6 can be continuously grasped.

In addition, in a normal charging circuit, only the above-mentioned charging and motor driving times are a problem, but in this embodiment, the value stored in the storage unit 21 is held even when the motor 5 is stopped, so there is a slight problem. Yes, but it consumes current. In order to correct this current, self-discharge pulses that are output at extremely long time intervals are generated when the electric shaver 1 is not in use, and this pulse subtracts the stored value in the storage unit 21. The display on the display unit 22 is forcibly stopped.

To explain the above configuration while illustrating more specific numerical values, the pulse signal generator 15 includes three sets of pulse generators 2 for charging, seed discharge, and self-discharge.
3, 24, 25 and a pulse switching section 27,
Pulse switching unit 2 outputs pulse signals at generation rates individually set for each pulse generator 23, 24, 25.
7, it is selectively sent to the frequency divider 28.

The pulse switching unit 27 is configured by combining a plurality of logic gate circuits, for example, and receives a charging timing signal s extracted from the charging timing detection unit 19 by waveform shaping the output of the charging circuit 11, and
A zero rotation detection signal f output from the motor rotation speed detection unit 31 to be described later and indicating when the motor 5 is stopped.
Switches in conjunction with the application of . 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, and when both are "0", the discharging pulse generator 24 is selected, and furthermore, when the zero rotation detection signal f is "1", the charging pulse generator 23 is selected. When only the detection signal is "1", the self-discharge pulse generator 25 is selected and connected to the frequency dividing section 28, respectively.

The frequency divider 28 includes in series 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. The pulse signal input to 29 is passed through the second frequency divider 30
On the output side, the generation rate is divided by a maximum of 1/2 ¹⁰ , that is, 1/1024, and extracted.

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 0 "1", that is, when 240 pulses have been counted, a full charge is displayed, and when the 255th pulse has been counted, charging is stopped. Since 8 hours = 2.8 x 10 ⁴ seconds, the pulse rate P ₁ of the charging pulse output from the charging pulse generator 23 is P ₁ = 2.8 x 10 ⁴ / (255 x 1024) = 0.1 seconds. By generating one pulse approximately every 0.1 seconds from the charging pulse generator 23, the storage unit 21
It can be seen that the counter is an 8-hour timer.

On the other hand, in this type of small electric equipment, a DC motor that uses a permanent magnet for the field is often used as the motor 5, and therefore, as shown in Fig. As T increases, the load current I supplied to the motor 5 during driving 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. Furthermore, an increase in the load current I will lead to a decrease in the continuous drive time of the motor 5 from a fully charged state, but if the capacities of the battery 6 and motor 5 are set,
In experiments or calculations using
The discharge duration until the voltage reaches the final voltage, that is, the continuous drive time of the motor 5 is determined. By determining this time for a plurality of motor rotational speeds n, the relationship between the motor rotational speed n and the continuously drivable time of the motor 5, which corresponds to the discharge characteristics of the battery 6, is determined.

The solid line curve 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, the magnitude of the rotation speed n of the motor 5 is detected by the motor rotation speed detection section 31, and the frequency division ratio of the frequency division section 28 is changed in a stepwise manner according to the detected value of the rotation speed detection section 31. As a result, a main discharge pulse whose pulse rate changes approximately as the load current I increases or decreases is obtained from the output end of the frequency dividing section 28, and by subtracting the stored value in the storage section 21 using this main discharge pulse, By doing so, 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 detects leakage magnetic flux generated from the armature when the motor rotates, or changes in magnetic flux due to a magnet (not shown) integrally attached to the rotating shaft of the motor 5, using the detection coil 32, and then outputs the detection signal. By shaping the waveform using 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.
It is input to the motor rotation detection section 31.

The motor rotation detection section 31 includes a rotation speed counting section 34 that samples and counts the number of rotation pulses a for a set time, and a rotation speed determination section 36 that determines the size of the count in the counting section 34. , the conversion signal outputted from the rotation speed determination unit 36 is inputted to the frequency division ratio conversion unit 37 combined with the first frequency divider 29, and the frequency division ratio of the first 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. The self-discharge pulse c output from the generator 25 is differentiated by a differentiating circuit 41 to generate a trigger signal d, which is used to trigger the counter 39.
clearing and regulating the generation timing of 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 (sixth pulse c).
(see figure b). The trigger signal d resets the content e of the rotation number counter 39 as shown in FIG. is opened and the number of rotation pulses a output from the discharge timing detection section 20 is sampled.

In this embodiment, a four-stage binary number counter is used as the rotation number counter 39, 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 rotation pulse a output from the discharge timing detection section 20 and the pulse width of the monostable multivibrator 40, the rotation speed shown in FIG.
The count e of the revolution counter 39 is "15" at 5100 revolutions or more, "14" at 4700 to 5100 revolutions, and 4300 to 4700.
It can be set to "13" at rotation, and "12" or less at 4300 rpm or less. Here, further, the number of revolutions counter 3
If the drivable time is ``10'' when the count number of 9 is ``15'', the drivable time decreases by 10% each time the count number in the revolution counter 39 decreases by 1, so basically it is a binary value. The frequency division ratio of the first frequency divider 29, which is a four-stage hexadecimal number, is determined by the rotation number counter 39.
By sequentially decreasing the count number in decimal form when it is "15" and in 9 form when it is "14", a discharge pulse with a pulse rate corresponding to the magnitude of the load current I can be obtained.

Furthermore, the total count value "255" counted over 8 hours during the charging period by the up-down counter of the storage unit 21 becomes approximately 38 during the discharge corresponding to the case where the first frequency divider 29 is switched to decimal. The discharge pulse rate _P2 may be set so that the discharge pulse rate P2 becomes "0" over the course of several minutes. The pulse rate P ₂ is P ₂ =38×60/(10×64×255)=0.014 [sec], and the pulse rate from the main discharge pulse generator 24 is approximately
It turns out that it is sufficient to generate one pulse 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 frequency-divided. The voltage is applied to the storage unit 21 via the unit 28 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 the amount of charge drops to zero after about two months from a fully charged state. Therefore, the pulse rate P ₃ of the self-discharge pulse c is 5.2×10 ⁶ seconds for two months, so P ₃ = 5.2×10 ⁶ / (255×1024) = 20 [sec], and the self-discharge pulse is generated. Approximately 20 from vessel 25
A self-discharge pulse c is output at a rate of one pulse per second.

The zero rotation detection section 43 provided on the output side of the rotation number counter 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 has stopped. The zero signal f is input to the pulse switching section 27, and is switched to the self-discharge pulse generator 25 side in conjunction with the "0" signal of the charging timing signal s described above, and at the same time is inverted by the inverter 44. When the motor is stopped, the display unit 46 is turned off and the power consumption by the display unit 22 is suppressed.

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 the second four 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 lights 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 is further performed so that all 8 bits of the storage section 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 section 45 disappears. At this time, since the switching unit 12 for regulating the charging time 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 charging the battery 6. Prevent overcharging.

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

When charging starts at time _t0 , it is determined in step 101 that charging has started, and the counter in the storage section 21 is switched to the UP side (step 101).
102) At the same time, the terminal voltage of the battery 6 gradually increases. However, if it is determined in step 103 that the terminal voltage of battery 6 is below 1.0V,
The count value in the storage section 21 is reset (step 104) and remains at 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 (step
105), and further displays the count status on the light emitting diode 47 of the display section 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 display unit 2 will not display after a predetermined period of time has elapsed.
2 is cut off, 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 to stop charging, 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 in the storage section 21 is reset in the same way as described above (step 109), but if it is determined in step 108 that the terminal voltage is 1V or more, the process moves to step 110. , it is determined whether 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 that during discharging to correct the power consumption when the device is not in use (step 111). At the same time, step
At 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. Furthermore, the motor rotation detection section 31 detects rotation pulse a.
The motor rotation speed, that is, the value of the load current I, is detected from the sampling number e (steps 113 to 115),
Depending on the magnitude of the current I, the frequency division ratio of the first frequency divider 29 is switched between decimal and septadecimal (step
116 to 119), and subtracts the stored value in the counter 21 at a rate corresponding to the magnitude of current consumption (step
120), and the subtraction status is displayed on the display section 22 (step 121).

If charging is performed at time _t5 , the charge amount display will not start from zero, but will be subtracted from the stored value at time _t5 , and therefore the current charge amount will be continuously displayed. In addition, as a result of the actual current consumption being larger than the integrated value, the terminal voltage of the battery 6 is reduced even though the value remains in the counter 21.
If the voltage drops below 1.0V, the count value is forcibly reset at step 109 (time _t7 ), the display is stopped (step 122), and the user is prompted to charge the battery.

Note that the pulse rate of the discharge pulse during discharge may be changed by changing the oscillation frequency of the discharge pulse generator 24 itself instead of changing the frequency division ratio of the first frequency divider 29. In that case, a variable capacitance diode is used as the capacitor that regulates the oscillation frequency of the discharge pulse generator 24, and a voltage proportional to the motor rotation speed is generated from the discharge timing detection section 20, and the capacitance of the capacitor is directly changed by this voltage. If so, the frequency of the discharge pulse can be changed continuously.

Furthermore, instead of having a plurality of pulse generators 23, 24, 25 and switching them using the pulse switching section 27, the frequency of one pulse generator is changed according to the charging or discharging timing detection. It's okay.

Further, the display unit 22 may directly display numbers using a liquid crystal instead of a light emitting diode, 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, during charging, as the amount of charge approaches a set value, the interval or frequency of the intermittent sound is changed, making it possible to audibly confirm the state of charge. Furthermore, the display section 22 does not always display light during charging and discharging, but is provided with a separate switch for checking the battery, and is displayed only when the switch is operated, thereby minimizing power consumption by the display section 22. 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, discharging, and self-discharging pulses are displayed in binary numbers corresponding to the magnitude of the current amount, and are directly added to the stored value in the storage unit 21 at predetermined intervals.

[Effects of the Invention] As described above, the present invention includes a pulse signal generating section 15 that outputs a pulse signal of a constant frequency corresponding to the discharge timing of the battery 6, and a pulse signal output from the pulse signal generating section 15. , a frequency divider 28 that divides the frequency according to a frequency division ratio set in multiple stages corresponding to the discharge current amount of the battery 6 to form a discharge pulse at a predetermined pulse rate, and a frequency divider 28 that sequentially integrates the input number of discharge pulses. By including a storage unit 21 that stores the remaining charge amount and a display unit 22 that displays the remaining charge amount in correspondence with the magnitude of the stored value in the storage unit 21, it is possible to reduce the load current while maintaining a relatively simple configuration. The amount of charge is displayed in immediate response to large and frequent fluctuations.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an example of an electric shaver implementing the present invention, FIG. 2 is a schematic diagram showing the basic configuration of the present invention, and FIG. 3 is a block diagram showing the 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, and Fig. 6 a to g explain the operation of the motor rotation speed detection section. FIG. 7 is a flowchart explaining the operation, and FIGS. 8a and 8b are explanatory diagrams showing the relationship between the battery terminal voltage and the stored value in the storage unit during charging and discharging. 5...Motor, 6...Battery, 11...Charging circuit, 15...Pulse signal generation section, 19...Charging time detection section, 20...Discharge time detection section, 21...Storage section, 22...Display Part, 28... Frequency division part, 31...
...Motor rotation speed detection section.

Claims (1)

[Claims] 1. A pulse signal generator 15 that outputs a pulse signal of a constant frequency in accordance with the discharge timing of the battery 6; A frequency division unit 28 that divides the frequency according to a frequency division ratio set in multiple stages corresponding to the amount of discharge pulses to form discharge pulses at a predetermined pulse rate, and a storage unit that sequentially integrates and stores the input number of discharge pulses. 21; and a display section 22 that displays the remaining charge amount in correspondence with the magnitude of the stored value in the storage section 21.