JPH01143986A - Battery life detection circuit - Google Patents

Abstract

PURPOSE:To accurately measure the life of a battery by changing oscillation frequency in accordance with a current value flowing out from a battery and counting and integrating the frequency to measure the current value flowing from the battery. CONSTITUTION:When a current value flowing out from the battery 1 is changed, voltage impressed to both the ends of a resistor 6 is changed and a voltage value 5a-2a and then a voltage value 8a-8b are changed, so that frequency appearing on the output 9a of a VF converter circuit 9 is also changed. Since the counting speed of a counter circuit 10 is changed, counting corresponding to the current value flowing out from the battery 1 is executed. An output 10a from the circuit 10 is applied to a digital comparator 12, and when a digital value 13a set up by a preset circuit 13 coincides with the output 10a, the circuit 12 outputs a coincidence signal to the output 12a. An alarm circuit 14 is driven by using the coincidence signal to output an alarm signal. Consequently, the life of the battery 1 can be accurately measured and the device can be prevented from generating malfunction.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a circuit that can accurately detect the battery life of a battery (primary battery).

[Conventional technology]

FIG. 3 is an example of a conventional circuit for detecting battery life. In the figure, 1 is a primary battery such as a non-rechargeable lithium battery, 2 is a load circuit, and 3 is a power supply circuit. During normal operation, current is supplied from this power supply circuit 3 to the load circuit 2 by closing the switch 4. Reference numeral 4 denotes a switch, and when the switch is open, power is supplied from the battery 1 through a diode 5 and a resistor 6 to stop the load circuit 2 and maintain the necessary holding state. 5 is a diode, power supply circuit 3
It serves to prevent backflow from the battery 1 to the battery 1. 7 is a voltmeter that measures the battery voltage across the battery 1 to detect battery life.

Next, the operation will be explained. The load circuit 2 is supplied with current by the primary battery 1 when the switch 4 is open, but
When the switch 4 is in the closed state, current is supplied from the power supply circuit 3. When the switch 4 is in the open state, the current of the battery 1 flows through the diode 5 and the resistor 6, and the required state of the load circuit 2 is maintained, and the energy of the battery 1 is consumed. When the energy of this battery decreases, the voltage across the battery decreases, but by measuring this voltage with the voltmeter 7, the lifespan of the battery can be detected. At this time, the limit voltage v1 at which the load circuit 2 maintains the holding state is determined as the specified voltage, and when the voltage on the voltmeter 7 reaches the specified voltage v1, it is determined that the battery life has expired and an alarm is issued with a buzzer or the like. In some cases, it may be configured as follows.

[Problem that the invention seeks to solve]

Conventional battery life detection circuits detect the battery life by measuring both ends of the battery, but this method has the following drawbacks.

[a) Most lithium batteries maintain a constant voltage until the end of their lifespan, but as they approach the end of their lifespan, the voltage drops rapidly. For this reason, when the battery is nearing the end of its life and the end of its life is detected, it takes a very short time from the time when the battery detects the specified voltage, which indicates the end of its life, to the voltage v2, which makes it impossible to maintain the load circuit's holding state. Therefore, even if the battery life is detected and the battery life is notified by a buzzer or the like, the warning is too late.

Furthermore, for the above reasons, it is impossible to notify the margin until the end of the service life.

(b) Also, as shown in FIG. 4, the power supply voltage varies greatly depending on the ambient temperature. On the other hand, since it is necessary to guarantee the holding operation of the load circuit 2 within a certain temperature range, it is necessary to set the specified voltage V to a low value, which also has the disadvantage that the time from alarm to malfunction becomes shorter and shorter. be.

(C) For the reasons mentioned above, if a malfunction causes serious problems, the battery is often replaced as it approaches the end of its lifespan, which also has the disadvantage that the battery cannot be used effectively.

This invention was made in order to solve the problems of the conventional ones as described above, and aims to provide a battery life detection circuit that can accurately measure the battery life and also detect the margin until the battery life is reached. This is the purpose.

[Means for solving problems]

The battery life detection circuit according to the present invention detects the battery life by measuring the value of current flowing out from the battery and integrating the amount of current flowing out.

[Effect]

In this invention, battery life is detected by changing the oscillation frequency depending on the amount of current flowing out from the battery, counting this oscillation frequency, integrating the amount of current, and measuring the amount of battery consumption. In addition to issuing a warning with a necessary margin, it is also possible to detect the margin until the end of the life by reading the integrated value.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a battery life detection circuit according to an embodiment of the present invention. In the figure, 1 is a primary battery such as a non-rechargeable lithium battery, 2 is a load circuit, 3 is a power supply circuit during normal operation, and switch 4 Close the terminal and supply power. When the switch 4 is open, current flows from the battery 1 to the load circuit 2 through the diode 5 and the resistor 6. 8 is a DC amplification circuit which amplifies the voltage across both ends 5a and 2a of the resistor 6.

Further, 8a is a voltage obtained by amplifying the voltage at the resistor end 5a, and 8b is the voltage at the resistor end 2ai! Indicates the voltage obtained by amplifying the voltage. 9 is a VF converter circuit, which outputs voltages 8a and 8b of the DC amplifier circuit 8.
The oscillation frequency is changed according to the voltage difference between the two. 10 is a counter circuit, and the output terminal 9a of the VF converter circuit
Count the number of pulses of the oscillation waveform output.

Also, 11 is a comparator, and 1! When power is supplied from the source circuit 3 and the voltage at the resistor end 2a is higher than the battery voltage 1a, a command is issued to stop the operation of the counter 10, and conversely, when the voltage at the resistor end 2a is lower than the battery voltage 1a, a command is issued to stop the operation of the counter 10. A command to continue the operation of the counter 10 is issued.

12 is a digital comparator circuit; 13 is a preset circuit in which a count value corresponding to the battery life is preset; the digital comparator circuit 12 compares the set value with the output 10a from the counter 10; 14
is an alarm circuit which issues an alarm in response to a command 12 output from a comparator 12 when the output 10a from the counter 10 and the count set value become the same value. 5 is a parallel-to-serial conversion circuit composed of a microcomputer circuit, which outputs the status of the counter 10 to the outside so that the external circuit 16 can detect the status of the counter and know the battery consumption status. be.

Next, the operation will be explained.

During normal operation, load circuit 2 is connected to switch 4 from power supply circuit 3.
When the switch 4 is open, the load circuit 2 is supplied with power from the battery 1 to the diode 5. resistance 6
Power is supplied through the load circuit 2, which causes the load circuit 2 to stop operating and maintain the required state. The power to maintain this holding state is supplied from battery 1, and the current is passed from battery 1 to diode 5. It is supplied to the load circuit 2 through the resistor 6, and a potential difference is generated in the resistor 6.

On the other hand, when the switch 4 is in the closed state and power is supplied from the power supply circuit 3, a voltage higher than the battery voltage 1a is supplied to the resistor end 2a, so no current flows from the battery 1.

The voltages across the ends 2a and 5a of the resistor 6 are amplified by a DC amplifier circuit 8 and output to output ends 8a and 8b, respectively. Therefore, the voltage 5a-2a across the resistor 6 is amplified to 8a
-8b. This voltage is applied to the VF converter circuit 9, and a waveform of an oscillation frequency corresponding to this voltage difference is output to 9a. The manner in which this oscillation frequency changes is shown as a characteristic example in FIG. 2, where the frequency changes in accordance with the voltage difference. A counter circuit 10 counts the number of pulses at this frequency. Therefore, when the value of the current flowing out of the battery 1 changes, the voltage across the resistor 6 changes, and the voltage value of 5a-2a and eventually 3a-3b changes, so the frequency appearing at the output 9a of the VF converter circuit changes. Change. Therefore, the counting speed of the counter circuit 10 changes, so that counting can be performed in accordance with the value of the current flowing out from the battery 1.

On the other hand, when power is supplied from the power supply circuit 3, the potential of the resistor end 2a becomes higher than the battery voltage 1a, and no current flows from the battery. In the comparator 11, when the potential of the resistor end 2a is higher than the battery voltage 1a, a command to stop the counting function of the counter circuit 10 is issued from the output 11a, and the counting is stopped. That is, counting can be stopped when no current flows out of the battery. Conversely, when power is not supplied from the power supply circuit 3, the battery voltage 1a is higher than the voltage at the resistor end 2a, and the output 11a of the comparator 11 does not stop the operation of the counter circuit, but allows normal counting operation. I will do it.

An output 10a from this counter circuit 10 is applied to a digital comparator circuit 12. The digital comparator circuit 12 outputs 12 if the digital value 13a set by the preset circuit 13 and the output value 10a of the counter match.
This is a circuit that emits a coincidence signal to a. Therefore, if the count value 10a corresponding to the battery current amount matches the preset digital value 13a, a signal indicating the match is output to 12a. If the value is set to a value slightly smaller than the value corresponding to the specified capacity (amount of current that can flow out), a match signal will be output to the output terminal 12a before the amount of current corresponding to the specified capacity is completely consumed. By using this coincidence signal, the alarm circuit 14 can be activated to issue an alarm signal.

In this way, it is possible to measure the amount of current flowing out from the battery and issue an alarm when a specified amount of current has flowed out.

Further, the parallel-to-serial conversion circuit 15 is a circuit for outputting the status of the counter 10 to the outside, and is composed of a microcomputer circuit, and the external circuit 16 can detect the status of the counter and know the battery consumption status. By performing calculations according to the counter output, it is possible to predict the lifespan of the battery.

As described above, according to this embodiment, the amount of battery consumption is measured by counting the current that actually flows out of the battery, so there is a margin depending on the amount of current that defines the battery life. A warning can be output.

Since the lifespan of a battery is determined by the amount of outflow current defined as the standard value of the battery, according to this embodiment, it is possible to detect the lifespan most reliably.

Further, according to this embodiment, it is also possible to easily grasp the consumption state of the battery.

In the above embodiment, a circuit including the comparator 11 was explained as an example, but the VF converter circuit 9
It is also possible to have the same function.

That is, when the voltage at the resistor end 2a increases and there is no outflow from the battery, the VF converter circuit outputs 3a-3b become negative values, so the VF converter output is eliminated and the counter circuit 10 stops counting. It is easily possible to do so.

Furthermore, the parallel-to-serial converter circuit 15 and the external circuit 16 for knowing the battery consumption status are not necessarily necessary, and even if these circuits are not available, it is sufficient to have the alarm function of the battery life alarm circuit. be.

Also, the preset circuit 13 is not necessarily necessary (even if the preset circuit 13 is not provided, it can be substituted by providing a circuit in the counter circuit 10 that sets the count start state of the counter circuit, Preset settings can also be omitted by adjusting the set value of the oscillation frequency.

In addition, the alarm circuit is not limited to a buzzer, etc., but an LCD
Various types of display such as two-color change display are possible.

Furthermore, the parallel-to-serial conversion circuit is a means to reduce the number of signal lines to the outside, and the parallel-to-serial conversion circuit may be omitted and the count output may be output as is. It is also possible to incorporate it into the life detection circuit.

When the battery life reaches the end and the battery is replaced, the count state of the counter circuit 10 may be set to the initial state (reset state), and this can be easily achieved by providing a switch or equivalent consideration to the battery replacement mechanism. It is possible.

Further, the DC amplifier circuit 10 is not necessarily required, and it is possible to configure the present circuit without it.

In addition, in the above embodiment, a resistor was used to detect the current value, but
It may be constructed with other elements (diodes, varistors, etc.), and the same effects as in the above embodiments can be achieved.

〔Effect of the invention〕

As described above, according to the battery life detection circuit according to the present invention, the battery life is detected by measuring the value of the current that actually flows out, so that it is possible to accurately measure the battery life. Since it is possible to detect the state of remaining battery, it is possible to prevent malfunction of the device and to make effective use of the battery.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a battery life detection circuit according to an embodiment of the present invention, FIG. 2 is a diagram showing an example of characteristics of a VF converter circuit,
FIG. 3 is a diagram showing a conventional battery life detection circuit, and FIG. 4 is a diagram showing the characteristics of battery voltage and battery life and the influence of temperature. In the figure, 1 is a battery, 2 is a load circuit, 3 is a power supply circuit,
4 is a switch, 5 is a diode, 6 is a resistor, 7 is a voltmeter, 8 is a VF converter circuit (frequency conversion circuit), 10 is a counter circuit, 11 is a comparator, 12 is a digital comparator circuit (-number circuit) , 13 is a preset circuit, 1
4 is an alarm circuit, 15 is a parallel-to-serial conversion circuit (battery remaining life calculation circuit), and 16 is an external circuit.

Claims (3)

[Claims] (1) A frequency conversion circuit that changes the oscillation frequency according to the current value flowing out from the battery and converts the current value into a frequency, and a counter circuit that measures the current value flowing out from the battery by counting and integrating the frequency. A battery life detection circuit characterized by comprising: (2) The device according to claim 1, further comprising a coincidence detection circuit that outputs a signal indicating that the battery life has come to an end when the output of the counter circuit reaches a predetermined count setting value. Battery life detection circuit. (3) The battery life according to claim 2, further comprising a battery life expectancy calculation circuit that outputs information on the battery life expectancy based on the output of the counter circuit and the count setting value corresponding to the battery life. Detection circuit.