JP2003032902A - Battery voltage detection circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a means of recognizing, even the consuming degree of battery voltage for a user to do with an inexpensive and simple circuit configuration formed with only one reference voltage installed. SOLUTION: This battery voltage detection circuit 1 permits voltage distributed to two, a resistor 6 and a resistor 7 to be charged into a capacitor 5. The charged voltage is applied to a non-inverting input terminal of a comparator IC10. Reference voltage is generated by a resistor 8 and a constant-voltage diode 9 and is applied to the non-reverse input terminal of the comparator IC10. The comparator IC10 outputs LOW to turn on a light-emitting diode LED12, when comparison voltage is lower than the reference voltage and outputs HIGH to turn off the light-emitting diode LED12, when it is higher.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery voltage detection circuit for displaying the state of a battery voltage as a power source in a device using a battery as a power source.

[0002]

2. Description of the Related Art Conventionally, in a device using a battery as a power source, in order to check the exhaustion state of the battery voltage, the reference voltage and the battery voltage are compared using a comparator IC. Generally, if it is low, it is judged as NG and displayed.

However, in such a determination, it is not possible to display the degree of consumption of the battery voltage. Therefore, in order to display the consumption level, a method has been adopted in which a plurality of reference voltages are provided to compare with the battery voltage and the consumption level of the battery voltage is displayed in stages. In addition, a battery voltage may be converted from an analog value to a digital value (A / D conversion) using a microcomputer (CPU), and continuous display may be performed by a liquid crystal display or the like.

[0004]

However, the method of displaying the consumption level of the battery voltage by providing a plurality of reference voltages has a complicated circuit configuration. Moreover, the method using a microcomputer has been an expensive device.

An object of the present invention is to provide means for allowing a user to recognize the degree of consumption of battery voltage with an inexpensive and simple circuit configuration in which only one reference voltage is provided.

[0006]

In order to solve the above problems, the present invention has the following features. In the following description of the means, the configuration corresponding to the embodiment will be illustrated by writing in parentheses. The reference numerals and the like correspond to the reference numerals in the drawings described later.

According to the first aspect of the invention, a charging unit (for example, the capacitor 5 in FIG. 1) for charging the voltage of the battery and a reference voltage generating unit for generating the reference voltage (for example, the resistor 8 and the constant voltage in FIG. 1). A diode 9), a comparison unit (for example, the comparator IC10 in FIG. 1) that compares the charging voltage of the charging unit and the reference voltage generated by the reference voltage generation unit, and a result output from the comparison unit. An output unit for turning on or off the light (for example, the light emitting diode LED of FIG. 1
12) and are provided.

According to the first aspect of the present invention, the battery voltage as the power source is charged, the charging voltage is compared with the reference voltage, the light is turned on when the charging voltage is lower than the reference voltage, and the light is turned off when the charging voltage becomes higher. . Therefore, with an inexpensive and simple circuit configuration,
The user can recognize the degree of consumption of the battery voltage based on the length of time the light is turned on.

According to a second aspect of the present invention, in the first aspect of the invention, the output section outputs or mutes sound according to the result output from the comparison section.

According to the second aspect of the invention, when the charging voltage is lower than the reference voltage, a sound is output, and when the charging voltage is higher, the sound is muted. Therefore, the user can recognize the consumption level of the battery voltage based on the length of the sound with an inexpensive and simple circuit configuration.

According to a third aspect of the present invention, in the first aspect of the invention, the output section turns on or off the light in accordance with the result output from the comparison section, and at the same time outputs or silences the sound. Is characterized by.

According to the third aspect of the present invention, when the charging voltage is lower than the reference voltage, the light is turned on and the sound is output at the same time, and when the charging voltage is higher, the light is turned off and the sound is turned off at the same time. Therefore, the user can grasp the consumption level of the battery voltage visually and auditorily with an inexpensive and simple circuit configuration.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings. First, the configuration will be described.

FIG. 1 is a circuit diagram showing the functional configuration of the battery voltage detection circuit 1. As shown in FIG. 1, the battery voltage detection circuit 1 includes a battery 2, a main switch 3, a diode 4, a capacitor 5, a resistor 6, a resistor 7, a resistor 8, a constant voltage diode 9, a comparator IC 10, a resistor 11, and a light emitting diode LED12. It is configured with. The battery voltage detection circuit 1 is built in a device 100 (not shown).

The battery 2 is the power source of the device 100. The battery voltage of the battery 2 is divided by the resistors 6 and 7, and is connected to the non-inverting input terminal of the comparator IC 10 as the comparison voltage Vin. The main switch 3 is connected to the battery 2 in series. The contact on the OFF side is connected to GND. The diode 4 is connected in parallel with the resistor 6 in reverse bias, and forms a discharge circuit for the capacitor 5 when the main switch 3 is OFF. As a result, the charging circuit is reset.

The capacitor 5 is connected in parallel with the resistor 7 and forms a charging circuit via the resistor 6. The capacitor 5 is charged toward the voltage obtained by dividing the battery voltage of the battery 2 into the ratio of the resistance 6 and the resistance 7, and the charging voltage is the comparison voltage Vin.
Is input to the non-inverting input terminal of the comparator IC10. The maximum charging voltage Vcmax of the capacitor 5 is Vc when the battery voltage is E, the resistor 6 is R6, and the resistor 7 is R7.
It is represented by the formula max = E * R7 / (R6 + R7).

The resistor 6 and the resistor 7 are connected in series, and the battery 2
The battery voltage of is divided into a ratio of resistance 6 and resistance 7. The divided voltage is charged by the capacitor 5.

The resistor 8 is connected in series with the constant voltage diode 9 to generate the reference voltage Vref. Reference voltage Vre
f is connected to the inverting input terminal of the comparator IC10.

The comparator IC10 compares the reference voltage Vref applied to the inverting input terminal with the comparison voltage Vin applied to the non-inverting input terminal and outputs the result. In the comparator IC10, the comparison voltage Vin is the reference voltage Vre.
LOW is output when it is lower than f, and HIGH when it is higher than f.
Is output.

The resistor 11 is connected in series with the light emitting diode LED12. The light emitting diode LED12 is
Connected to the battery 2 via the resistor 11 and connected to the comparator IC
It is turned on when the output of 10 is LOW, and turned off when it is HIGH.

Next, the operation will be described. Battery voltage detection circuit 1
The operation will be described with reference to the flowchart of FIG.

When the switch is pressed to operate the device 100 and the main switch 3 is turned on (step S1; Y), the battery voltage E is applied to the battery 2, and the battery voltage E is applied to the capacitor 5 as the resistor 6. The voltage divided by the ratio of the resistor 7 is charged (step S2). Then, the charging voltage of the capacitor 5 is set to the comparator I as the comparison voltage Vin.
It is applied to the non-inverting input terminal of C10 (step S
3).

On the other hand, the reference voltage Vref is generated by the resistor 8 and the constant voltage diode 9 (step S4), and the reference voltage Vref is applied to the inverting input terminal of the comparator IC10 (step S5). And the comparator IC
When the comparison voltage Vin is smaller than the reference voltage Vref (step S6; Y), 10 outputs LOW (step S7) and turns on the light emitting diode LED12 (step S8). When the comparison voltage Vin is higher than the reference voltage Vref (step S6; N), the comparator IC
10 outputs HIGH (step S9), and turns off the light emitting diode LED12 (step S10). As long as the main switch 3 is ON (step S1
1; N), steps S2 to S10 are repeatedly executed.

When the switch of the apparatus 100 is turned off and the main switch 3 is turned off (step S11;
Y), the charge of the capacitor 5 is discharged through the diode 4 and the charging circuit is reset (step S12),
The battery voltage detection process ends.

FIG. 3 is a graph showing changes in the charging voltage (comparative voltage) Vin of the capacitor 5 with time. The charging time of the capacitor 5 is determined by the resistor 6 and the time constant of the capacitor 5. In FIG. 3, when the battery voltage E is sufficiently high, the charging curve of the capacitor 5 becomes as shown by A, and the time when the comparison voltage Vin reaches the reference voltage Vref is T1. That is, since the comparison voltage Vin is smaller than the reference voltage Vref at first after turning on the main switch 3, the light emitting diode LED12 is turned on. When the time T1 has elapsed, the comparison voltage Vin is equal to the reference voltage Vref.
Since it becomes larger, the light emitting diode LED12 is turned off.

As the battery voltage E decreases, the charging curve of the comparison voltage Vin of the capacitor 5 shifts as shown by B, and the light emitting diode LED12 lights up until time T2 elapses. When the battery is further consumed, the charging curve becomes like C, and the comparison voltage Vin of the capacitor 5 never exceeds the reference voltage Vref. Therefore, the light emitting diode LED12 maintains the lighting state.

As described above, according to the battery voltage detection circuit 1, when the switch of the device 100 is input and the main switch 3 is turned on, the battery voltage E is applied to the resistor 5 and the resistor 6 in the capacitor 5. The divided voltage is charged. Then, the charging voltage is applied to the non-inverting input terminal of the comparator IC10 as the comparison voltage Vin. On the other hand, the reference voltage Vref is generated by the resistor 8 and the constant voltage diode 9 and applied to the inverting input terminal of the comparator IC10. When the comparison voltage Vin is lower than the reference voltage Vref, the comparator IC10 outputs LOW and the light emitting diode L
The ED 12 is turned on, and when it becomes high, HIGH is output and the light emitting diode LED12 is turned off. That is, the light always turns on when the power is input, the light turns off in a shorter time as the battery voltage E is sufficiently high, and the light time increases as the battery voltage E decreases. When the battery voltage E becomes equal to or lower than the reference voltage, the lighting state is continued.

Therefore, the battery voltage detection circuit 1 has a simple and inexpensive circuit structure and reduces the consumption of the battery 2 by the light emitting diode LE.
It can be displayed as the length of the lighting time of D12.
Therefore, the user can recognize that if the lighting time of the light emitting diode LED12 becomes long when the switch of the device 100 is turned on, the battery replacement time is approaching. Further, if the reference voltage Vref is set as the limit voltage of the battery voltage E in the operation of the device 100, the light emitting diode LED12 continues to maintain the lighting state when the voltage becomes equal to or lower than the reference voltage Vref, so that the user can easily recognize the time of battery replacement. The malfunction of the device 100 can be prevented. Further, according to the battery voltage detection circuit 1, the power switch of the device 100 is turned on.
Since the battery voltage E is continuously checked during the above state, when the battery voltage E drops during use of the device 100, the light emitting diode LED12 lights up and the battery voltage E falls below the reference voltage. You can warn that it has become.

The description in the above embodiment is a preferred example of the battery voltage detection circuit 1 according to the present invention, and the present invention is not limited to this. For example, according to the above embodiment, the method of displaying the degree of battery consumption is indicated by the lighting time of the light emitting diode. However, a buzzer may be connected to warn the battery consumption based on the length of the sound. . Further, by connecting a light emitting diode and a buzzer in parallel, it is possible to display both the lighting time and the sound duration. As a result, it is possible to visually and audibly grasp the degree of battery consumption.

By inserting a load equivalent to the maximum load current of the device between the output of the comparator and the power supply, it is possible to check the battery voltage while the equivalent load current is flowing. In addition, the detailed configuration and detailed operation of the battery voltage detection circuit 1 can be appropriately changed without departing from the spirit of the present invention.

[0031]

According to the present invention, it is possible to provide a means by which the user can recognize the degree of consumption of the battery voltage with an inexpensive and simple circuit configuration in which only one reference voltage is provided.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a functional configuration of a battery voltage detection circuit 1 according to the present invention.

FIG. 2 is a flowchart showing the operation of the battery voltage detection circuit 1 of FIG.

FIG. 3 is a charging voltage (comparative voltage) V of the capacitor 5 in FIG.
7 is a graph showing changes in in with time of battery voltage E.

[Explanation of symbols]

1 Power supply voltage detection circuit 2 batteries 3 Main switch 4 diode 5 capacitors 6 resistance 7 resistance 8 resistance 9 Constant voltage diode 10 Comparator IC 11 resistance 12 Light emitting diode LED

Claims (3)

[Claims] 1. A charging unit for charging the voltage of a battery, a reference voltage generating unit for generating a reference voltage, and a comparing unit for comparing the charging voltage of the charging unit with the reference voltage generated by the reference voltage generating unit. A battery voltage detection circuit, comprising: an output unit that turns on or off light according to a result output from the comparison unit. 2. The battery voltage detection circuit according to claim 1, wherein the output section outputs or mutes sound according to the result output from the comparison section. 3. The battery voltage detection circuit according to claim 1, wherein the output section turns on or off the light according to the result output from the comparison section, and at the same time outputs or silences the sound.