JPH09221142A - Electric source circuit with back-up battery and liquid container with indication function provided with the circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To retain a stable supply voltage, by providing a replenishing means to supply electric power from a back-up battery when the voltage of a solar cell has reached a lower level than the minimum value for driving, in an appliance like a vacuum bottle of which water temperature or water level is indicated by the electric power obtained from the solar cell. SOLUTION: When the illuminous intensity is larger than 100 Lx for instance in a water-temperature or water-level detection circuit equipped in a liquid container like a vacuum bottle, since the voltage supplied from a solar cell 6 is 2.5V or higher, a transister Tr2 is put off and a transister Tr1 is kept in the putoff state and hence, electric current does not flow from a back-up battery 7. But when the illuminous intensity gets lower than 100 Lx, the supply voltage from the solar cell gets lower than 2.5V, the transister Tr1 is put on and hence, current flows from the back-up battery 7 to resistances R3 , R2 . Accordingly, the transister Tr1 is put on and the electric power is supplied to the circuit from not only the solar cell but also the back-up battery 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solar cell drive circuit used for displaying the temperature and water level of water contained in a pot or a thermos bottle that does not require an external power source by the power supplied from the solar cell. It is a thing.

[0002]

2. Description of the Related Art Conventionally, in a thermos bottle or the like, the temperature and water level of the contained water can be displayed by using the electric power supplied from a battery or the like.
No. 1 gazette, (2) Jikken 2-43302 gazette, (3)
There is one disclosed in Japanese Utility Model Publication No. 4-43647.

In the above (1), the electrodes are arranged at the center and the outer periphery of the liquid container respectively, and the change in the electrostatic capacitance between the electrodes due to the difference in the water level is detected by the power supplied from the battery.
It is intended to turn on D.

The above-mentioned (2) is designed so that the solar cell is installed at the most convenient place for collecting light and the lead wire to the liquid quantity display portion can be made the shortest. The same as (1) above. The liquid amount is displayed based on the change in capacitance between the two electrodes.

The above (3) is also the same as the above (1) and (2).
The liquid amount is displayed based on the change in capacitance between the two electrodes. However, the liquid level is displayed by discharging the capacitor composed of both electrodes and counting the number of charge pulses while the terminal voltage drops to the reference voltage, and the battery is used as the power supply. .

[0006]

However, in the above (1), there is a problem that a separate battery is required, which requires time and effort for replacement and the like.

Further, in (2), since the supply voltage of the solar cell fluctuates due to the difference in ambient brightness, reliable display is impossible with the thermos, and it has not yet been put to practical use. Moreover, because the electric capacity of the solar cell is small,
Since it is necessary to prevent the IC circuit from being affected by external noise, the negative lead wire of the liquid volume display unit is grounded to the outer case. However, once the IC circuit malfunctions due to the influence of noise, there is a problem in that the display on the liquid volume display unit remains unchanged.

Further, in the above (3), since the water level is detected by discharging the capacitor composed of both electrodes, power consumption is large and a solar cell having a small electric capacity cannot be used. .

Therefore, the present invention makes it possible to effectively use the power supplied from the solar cell while maintaining a stable supply voltage, and a power supply circuit with a backup battery and a low supply voltage from the circuit. An object of the present invention is to provide a liquid container with a display function that can perform an appropriate display without causing a malfunction.

[0010]

In order to achieve the above object, the present invention provides a power supply circuit with a backup battery, a backup battery, a solar battery, and a drive circuit for driving the other circuits whose voltage value input from the solar battery is. And a power replenishing means for supplying electric power from the backup battery when the driving value is lower than the minimum required driving value. If the amount of light decreases and the supply voltage from the solar cell decreases,
The power from the backup battery is replenished by the power replenishing means.

It is preferable to include power supply stopping means for stopping the power supply from the backup battery when the voltage value input from the solar cell falls below a drive unnecessary value lower than the drive minimum value. In this case, if the amount of light is further reduced and the power supply is considered unnecessary, the power supply stopping means forcibly stops the power supply from the backup battery. As a result, the life of the backup battery can be further extended.

In order to achieve the above object, the liquid container with a display function is driven by the power supplied from the power supply circuit with a backup battery according to claim 1 or 2, and based on the detection signal of the water level detection means. A water level display circuit for displaying the water level on the display unit, and the water level display circuit,
An oscillation circuit that outputs a pulse signal, and a latch circuit that causes the display unit to display the water level by inputting the detection signal of the water level detection means to a set terminal and inputting the pulse signal of the oscillation circuit to a reset terminal. It was equipped with.

In this liquid container, the power supply circuit with the backup battery automatically replenishes the power from the backup battery when the voltage supplied from the solar cell is not stable, so that the constant voltage is maintained and the display unit malfunctions. Does not occur. In particular, even if it is adversely affected by external noise, a pulse signal is input from the oscillator circuit to the reset terminal of the latch circuit to always reset it, so that the constant voltage is supplied from the power supply circuit with the backup battery. Therefore, it is possible to perform a stable display operation.

Furthermore, in order to achieve the above object, the liquid temperature in the liquid container is driven by the power supplied from the power supply circuit with the backup battery according to claim 1 or 2 and based on the detection signal of the temperature detecting means. Is displayed on the display unit, the temperature display circuit includes an oscillation circuit that outputs a pulse signal, a system reset IC that determines the liquid temperature based on the detection signal of the temperature detection unit, and the system reset. The output signal from the IC is input to the set terminal, and the pulse signal from the oscillation circuit is input to the reset terminal, thereby providing a latch circuit for displaying the temperature on the display unit.

Also in this liquid container, a constant voltage can be maintained by the power supply circuit with the backup battery and the latch circuit as in the above, so that no malfunction occurs in the display section. Further, by using the system reset IC as a voltage comparator, it is possible to configure a liquid temperature determination unit with low power consumption, and it is possible to further improve the effect of preventing malfunction in the display unit.

If the power supplied from the power supply circuit with the backup battery to the water temperature determination circuit is supplied through the Zener diode connected in parallel, the change in the backup battery electromotive force due to the change in room temperature can be reduced. The error in water temperature determination can be reduced.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings.

(First Embodiment) FIG. 1 shows a water level / water temperature detection circuit provided in a liquid container 11 equipped with a power supply circuit 1 according to the present invention. The circuit 2 includes an oscillation circuit 3, a one-shot multivibrator 4, and a water level determination circuit 5.

The power supply circuit 1 is provided with a solar battery 6 and a backup battery 7. A capacitor C is connected in parallel to the solar cell 6 so that the supply voltage is smoothed. The positive pole of the solar cell 6 is connected to the V of the one-shot multivibrator 4 via the diode D _1.
V _{OUT of the} system reset IC 9 described below via the _CC terminal, the collector of the first transistor Tr ₁ and the resistor R _11.
In addition to being connected to the terminal, it is connected to the base of the second transistor Tr ₂ which is a power replenishing means via the diode D ₂ and the resistor R ₁ . The negative electrode of the solar cell 6 is connected to the reference terminals of the respective display units 14 and 15 of the LCD 13 described below, the GND terminal of the one-shot multivibrator 4, and the GND terminal of the system reset IC 9 respectively. The emitter of the second transistor Tr ₂ is connected to the base of the first transistor Tr ₁ , while the resistor R ₃ and the backup battery 7 are connected in parallel between the emitter and the collector. The voltage supplied from the power supply circuit 1 to the water temperature determination circuit 5 is made constant by the resistor R ₄ and the Zener diode ZD.

The water temperature determination circuit 2 comprises a thermistor 8, a system reset IC 9 and a water temperature detection latch circuit 10a.

The thermistor 8 is arranged in the liquid container 11 (in FIG. 1, it is shown at a position apart from the liquid container 11 for the sake of simplicity), and one terminal is connected through resistors R ₄ and R ₅ . Is connected to the positive pole of the solar cell 1, and the other terminal is connected to the V _CC terminal of the system reset IC 9.
Here, the one whose output voltage becomes low when the liquid temperature becomes 70 ° C. or lower is used.

The system reset IC 9 is originally an element for monitoring the input voltage to prevent malfunction of the microcomputer (for example, manufactured by MITSUMI ELECTRIC CO., LTD .; PST901).
1 etc. can be used. ). The internal configuration will be described. As shown in FIG. 2, two operational amplifiers 100a, 1a are provided.
00b and two transistors Tr ₁₀₁ and Tr ₁₀₂ . The negative input terminal of the operational amplifier 100a is V _CC
It is connected to the middle point of resistors R ₆ and R ₇ internally connected between the terminal and the GND terminal, and the positive input terminal is connected to the low voltage circuit 11. On the other hand, the output terminal of the operational amplifier 100a is connected to the base of the transistor Tr ₁₀₁ via a resistor R _8, and is connected to the negative input terminal of the operational amplifier 100b collector of the transistor Tr ₁₀₁ via a resistor R _9. The output terminal of the operational amplifier 100b is a resistor R
It is connected via ₁₀ to the base of the transistor Tr ₁₀₂ . The collector of the transistor Tr ₁₀₂ and the positive input terminal of the operational amplifier 100b are system reset ICs.
9 is connected to the output terminal V _OUT of the transistor Tr ₁₀₁ ,
The emitter of Tr ₁₀₂ is grounded.

System reset I having such a circuit configuration
The output terminal V _{OUT of} C9 is connected to the positive pole of the solar cell 6 via the resistor R ₁₁ , and the latch circuit 10a is connected.
Of the solar cell 6 is connected to the negative terminal of the solar cell 6. Further, as described above, since the V _CC terminal is connected to the thermistor 8 and the resistor R _5, and the combined resistance of the thermistor 8, the resistor R _5,
V due to the voltage division with the internal resistance of the system reset IC 9
_The voltage value input to the _CC pin is determined. Since the system reset IC 9 can detect the change in the input voltage with the voltage of 1.1V as the reference value,
The system reset IC 9 can be used as a normal voltage comparator, and due to its low power consumption, it can be used for displaying the liquid temperature of the solar cell 6.

The oscillating circuit 3 oscillates a pulse signal (rectangular wave) whose oscillation frequency is set to 100 Hz and an inverted pulse signal from the first output terminal a and the second output terminal b, respectively. This oscillation frequency is the same as the operating frequency when the LCD 13 is statically driven. This allows
A drive circuit dedicated to the LCD 13 is not required, and the number of parts can be reduced.

As shown in FIG. 3, the LCD 13 has a water temperature display portion 14 (a portion representing steam is lit or extinguished) indicating whether or not the temperature of contained water exceeds a predetermined temperature.
And a water level display unit 15 having two upper and lower display units 15a and 15b having a shape similar to that of the side view of the liquid container 11, and is provided on the upper front surface of the liquid container 11, for example. In the water level display parts 15a and 15b, when both are lit, the water level is half or more, when the lower display part 15b is lit, the water level is half or less, and neither is lit.
When the lower display unit 15b is turned off, the characters "hot water supply" printed on the display unit 15b can be recognized.

The one-shot multivibrator 4 has its input terminal connected to the second output terminal b of the oscillation circuit 3 and its output terminal connected to the reference electrode 16a provided on the bottom of the liquid container 11 for oscillation. Second output terminal b of circuit 3
The pulse signal synchronized with the on-edge of the pulse signal from is output.

The water level determination circuit 5 includes a reference electrode 16a provided at the bottom of the liquid container 11, a first measurement electrode 16b and a second measurement electrode 16c provided above and at the bottom, and a first water level detection. Latch circuit 10b, second water level detection latch circuit 1
0c.

The first and second water level detecting latch circuits 10b,
A so-called NOR latch is used as the liquid temperature detecting latch circuit 10a for 10c, and each output terminal has an LCD1.
The three water level display units 15 are connected to one terminal of each of the display units 15a and 15b. Further, the first measuring electrode 16b provided on the bottom of the liquid container 11 is connected to the set terminal S of the first water level detecting latch circuit 10b, and the set terminal S of the second water level detecting latch circuit 10c is connected to the intermediate portion. The provided second measurement electrode 16c is connected. Furthermore, the oscillator circuit 3 is connected to the reset terminal R of each latch circuit 10b, 10c.
The first output terminal a of is connected. Furthermore, the first
And second measuring electrodes 16b, 16c are connected respectively to the first, the negative pole of the solar cell 6 via a second resistor R _12, R _13.

In the water level / water temperature detection circuit having the above-mentioned configuration, the power supply is switched between the solar cell 6 alone and both the solar cell 6 and the backup battery 7 in the following manner, and
Water temperature and water level are detected.

(Switching of Battery) For example, when used in the daytime, if the brightness is 100 Lx or more, the supply voltage from the solar cell 6 is 2.5 V or more, so the second transistor Tr ₂ is turned off. It becomes a state. Thus, the voltage equal between the base and emitter of the first transistor Tr _1, the first transistor Tr ₁ is kept off, no current flows from the backup battery 7.

If the brightness is less than 100 Lx, such as when the room lighting is dark in the evening or at night, the voltage supplied from the solar cell 6 is less than the driving minimum value (for example, 2.5 V), and the second transistor Tr. ₂ is turned on. As a result, a current flows from the backup battery 7 to the resistors R ₃ and R ₂ , and the voltage drops at the resistor R ₃ . The first transistor Tr ₁ is turned on due to the decrease in the base voltage, and power is supplied to the circuit not only from the solar cell 6 but also from the backup battery 7.

As a result, the supply voltage from the power supply circuit 1 is always maintained constant regardless of the change in ambient brightness.
The drive state of the water level / water temperature detection circuit is stable, and a predetermined display can be appropriately performed on the LCD 13 without causing a malfunction.

(Detection of Water Temperature) The water temperature / water level detection circuit having the above-described configuration detects the water temperature as follows. That is, when hot water is poured into the liquid container 11 and the temperature exceeds a set temperature (for example, 70 ° C.), the electric resistance value of the thermistor 8 becomes low, and the combined resistance of the thermistor 8 and the resistor R ₅ and the system The voltage division with the internal resistance of the reset IC 9 becomes high and becomes 1.1 V or more, which is the reference voltage. As a result, the output from the system reset IC 9 goes high.

Then, when the temperature of the hot water contained in the liquid container 11 falls below the set temperature due to the passage of time or the like, the electric resistance value of the thermistor 8 rises, as shown in FIG. And system reset IC9 V _CC
The voltage input to the terminal drops. As a result, the input voltage becomes less than the reference voltage, and the system reset IC 9
The output from is low.

In the liquid temperature detecting latch circuit 10a, as shown in FIG. 5, when the output from the system reset IC 9 is high, 1 is generated by the pulse signal from the oscillation circuit 2 input to the reset terminal R. While being reset at a cycle of / 100 seconds, the output becomes high and the water temperature display portion 14 of the LCD 13 is turned on. When the liquid temperature drops and the output from the system reset IC 9 becomes low, the output from the output terminal becomes low and the water temperature display unit 14 is turned off.

(Detection of Water Level) If hot water is poured into the liquid container 11 and the water level is located above the first measuring electrode 16b, as shown in FIG.
Since the measurement electrode 16b and the second measurement electrode 16c are electrically connected, each water level detection latch circuit 10b, 10c.
The pulse signal from the one-shot multivibrator 4 is input to the set terminal of the. As a result, the LCD 13
Both the display units 15a and 15b of the water level display unit 15 are turned on.

When the water level decreases due to use, an insulating state is sequentially formed between the reference electrode 16a, the first measuring electrode 16b, and the second measuring electrode 16c, as shown in FIG. 6 (b).
As shown in, the first water level detection latch circuit 10b, the second
The pulse signal is no longer output in the order of the water level detection latch circuit 10c, and the corresponding portion of the LCD 13 is turned off. Thus, at present, the range of the water level in the liquid container 11, that is, more than half, less than half, or 400 cc
It is possible to determine whether or not the following.

In the first embodiment, only one system reset IC 9 is provided so that the liquid temperature can be displayed only in two steps, but the number can be further increased to display it in a plurality of steps. Alternatively, it may be used for detecting cold water.

Further, in the first embodiment, the first measuring electrode 16b, the second measuring electrode 16c and the water temperature detecting latch circuit 10a and the first water level detecting latch circuit 10b corresponding thereto are provided to control the water level. More than half, less than half, 400
Although it is possible to recognize in three modes of cc and below, the water level can be detected by further subdividing. However, in this case, the measurement electrode and the latch circuit are necessary for each water level desired to be detected.

(Second Embodiment) FIG. 7 shows a water level / water temperature detection circuit according to a second embodiment. The circuit according to the first embodiment is a power supply stopping means. The difference is that three transistors Tr ₃ are provided. That is, the base of the third transistor Tr ₃ is connected between the resistors R ₁₄ and R ₁₅ connected in parallel to the solar cell 6, and the collector is connected to the collector of the second transistor Tr ₂ via the resistor R _2. The emitter is connected to the negative pole of the solar cell 6.

In the water level / water temperature detection circuit, if the brightness is less than 20 Lx, such as when the room interior lighting is turned off at night, it is determined that it is not necessary to look at the LCD 13, and the display is not performed. I have to. That is, the supply voltage from the solar cell 6 is a drive unnecessary value (for example, 0.7
V) or higher, the third transistor Tr ₃ is turned on, and the first transistor Tr ₁ and the second transistor Tr ₂ have the same functions as those in the first embodiment,
If the supply voltage drops below the drive unnecessary value, the third
The transistor Tr ₃ is turned off, and the first transistor Tr ₁ and the second transistor Tr ₂ are forcibly turned off so that the power supply from the backup battery 7 can be stopped. Since the water temperature detection and the water level detection are the same as those in the first embodiment, their description will be omitted.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a water level / water temperature detection circuit including a battery switching power supply circuit according to a first embodiment.

FIG. 2 is a circuit diagram of the system reset IC shown in FIG.

FIG. 3 is a front view of the LCD shown in FIG.

FIG. 4 is a graph showing a relationship between inputs and outputs of the system reset IC of FIG.

5 is a graph showing the relationship between the input and output of the liquid temperature detection latch circuit of FIG. 1. FIG.

6 is a graph showing the relationship between the input and output of the water level detection latch circuit of FIG.

FIG. 7 is a circuit diagram of a water level / water temperature detection circuit including a battery switching type power supply circuit according to a second embodiment.

[Explanation of symbols]

 1 Power Supply Circuit 2 Water Temperature Judgment Circuit 3 Oscillation Circuit 5 Water Level Judgment Circuit 6 Solar Battery 7 Backup Battery 8 Thermistor 9 System Reset IC 10a Water Temperature Detection Latch Circuit 10a, 10b First and Second Water Detection Latch Circuit 11 Liquid Container 13 LCD 16a Reference electrode 16b, 16c First and second measurement electrodes

Claims (5)

[Claims] 1. A backup battery, a solar battery, and power supplied from the backup battery when a voltage value input from the solar battery falls below a driving minimum value required for driving other circuits. A power supply circuit with a backup battery, comprising: a replenishing means. 2. A power supply stopping means for stopping the power supply from the backup battery when the voltage value input to the base from the solar cell falls below a drive unnecessary value lower than the drive minimum value. The power supply circuit with a backup battery according to claim 1, wherein: 3. A water level display circuit, which is driven by the power supplied from the power supply circuit with a backup battery according to claim 1 or 2 and displays a water level on a display unit based on a detection signal of a water level detection means. A liquid container with a display function, wherein the water level display circuit has an oscillation circuit that outputs a pulse signal, a detection signal of the water level detection means is input to a set terminal, and a pulse signal of the oscillation circuit is input to a reset terminal. A liquid container with a display function, comprising a latch circuit for displaying the water level on the display unit. 4. A temperature that is driven by the power supplied from the power supply circuit with a backup battery according to claim 1 or 2 and that causes the display unit to display the liquid temperature in the liquid container based on the detection signal of the temperature detection means. A liquid container with a display function including a display circuit, wherein the temperature display circuit outputs an pulse signal, a system reset IC that determines a liquid temperature based on a detection signal from the temperature detection means, A latch circuit that causes the display unit to display a temperature by inputting an output signal from the system reset IC to a set terminal and a pulse signal from the oscillation circuit to a reset terminal is provided. Characteristic liquid container with display function. 5. The liquid container with a display function according to claim 3, wherein power supplied from the solar cell drive circuit to the water temperature determination circuit is supplied via a Zener diode connected in parallel.