JP2000295787A - Battery failure detecting circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent shortening of operation life of a battery even when a battery voltage is searched. SOLUTION: A current is applied with a switch circuit 8 to the predetermined time resistor 4 in order to generate a voltage drop to search a voltage of a battery 3 while the power supply 1 is in the on state. A voltage due to the voltage drop generated in the resistor 4 is compared with the predetermined reference voltage with a comparator 5 and when the voltage due to the voltage drop is less than the reference voltage, an alarm is issued. An output of the comparator 5 is held with a holding unit 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery abnormality detection circuit, and more particularly to a battery abnormality detection circuit for a backup battery that supplies power instead of a normally used power supply when the power supply is off.

[0002]

2. Description of the Related Art Conventionally, this type of battery abnormality detection circuit detects an abnormality in a backup battery that supplies power to a load instead of this power supply when a normally used power supply for supplying power to the load is off. Used to detect.

Referring to FIG. 4, which is a circuit diagram of the conventional battery abnormality detection circuit, the conventional battery abnormality detection circuit includes a normally used power supply 1 (for example, 5 V) for supplying power to a load 2 in an on state, Battery 3 (for example, from 2.3 V to 3.3 V) that supplies power to load 2 when power supply 1 is off
V) and the battery 3 connected in parallel with the battery 3.
And a resistor 4 for generating a voltage drop for checking the voltage of the battery 3 by constantly flowing a current, a voltage due to the voltage drop generated in the resistor 4 and a predetermined reference voltage (a voltage obtained by dividing the voltage of the power supply 1 For example, when the load 2 is a non-volatile memory such as a CMOS memory, the resistance 4 is compared with a voltage (for example, 2.3 V) slightly higher than a memory holding limit voltage (for example, 2 V) to back up this memory. And a comparator 5 for outputting an alarm when the voltage caused by the voltage drop generated in the step (c) is lower than the reference voltage.

[0004]

In the above-mentioned conventional battery abnormality detection circuit, the current is always passed through the resistor connected in parallel with the battery and generating a voltage drop for checking the voltage of the battery. Since the current flows through the resistor even when the voltage of the battery is not checked, there is a problem that the life of the battery is short.

An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art, and it is possible to check the voltage of a battery without constantly supplying current to the resistor which generates a voltage drop for checking the voltage of the battery. Another object of the present invention is to provide a battery abnormality detection circuit that does not shorten the battery life.

[0006]

A first battery abnormality detection circuit according to the present invention examines a battery for supplying power to a load when power is turned off, and a voltage of the battery connected in parallel with the battery when a current flows. A switch circuit for causing a current to flow through the resistor for a predetermined time to generate a voltage drop for checking the voltage of the battery while the power supply is on; and A comparator that compares a voltage caused by a voltage drop generated in the resistor with a predetermined reference voltage and outputs an alarm when a voltage caused by the voltage drop generated in the resistor is less than the reference voltage, and holds an output of the comparator. Holding part to be
It is provided with.

A second battery abnormality detection circuit according to the present invention generates a battery for supplying power to a load when a power supply is turned off, and a voltage drop for checking the voltage of the battery when a current flows by connecting the battery in parallel. A switch circuit configured to form a circuit with the battery and the resistor for a predetermined time when a power-on signal indicating that the power is turned on and to flow a current through the resistor, A comparator that compares a voltage due to the voltage drop generated by the resistor with a predetermined reference voltage and outputs an alarm when a voltage due to the voltage drop generated by the resistor is less than the reference voltage; and holds an output of the comparator. And a holding unit that performs the operation.

The third battery abnormality detecting circuit according to the present invention comprises:
A battery for supplying power to the load when the power is off, a resistor connected in parallel with the battery and generating a voltage drop for checking the voltage of the battery when a current flows, and a current flowing through the resistor during the period when the power is on A switch circuit that forms a circuit with the battery and the resistor for a predetermined period of time when receiving an instruction signal for flowing the current so that a current flows through the resistor, and a voltage generated by a voltage drop generated by the resistor. A comparator for comparing with a predetermined reference voltage and outputting an alarm when a voltage due to a voltage drop generated by the resistor is lower than the reference voltage; and a holding unit for holding an output of the comparator. Have been.

[0009]

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a circuit diagram showing one embodiment of a battery abnormality detection circuit according to the present invention.

The embodiment shown in FIG. 1 includes a battery 3 for supplying power to a load 2 when a power supply 1 is turned off,
And a resistor 4 that generates a voltage drop for checking the voltage of the battery 3 when a current flows and a voltage drop for checking the voltage of the battery 3 while the power supply 1 is on. A switch circuit 8 for allowing a current to flow through the resistor 4 for a predetermined time (for example, 1 ms);
And a predetermined reference voltage (a voltage obtained by dividing the voltage of the power supply 1. For example, when the load 2 is a non-volatile memory such as a CMOS memory, the memory holding limit is used to back up this memory. A comparator 5 that compares a voltage (for example, 2.3 V) slightly higher than the voltage (for example, 2 V) and outputs an alarm when the voltage due to the voltage drop generated in the resistor 4 is less than the reference voltage.
And a holding unit 7 for holding the output of the comparator 5.

The switch circuit 8 forms a circuit with the battery 3 and the resistor 4 for a predetermined time (for example, 1 ms) when receiving a power-on signal indicating that the power source 1 is turned on, and causes a current to flow through the resistor 4. Like that.

The holding unit 7 holds the output of the comparator 5 after a lapse of a predetermined time (for example, 0.5 ms) from when the switch circuit 8 receives a power-on signal indicating that the power supply 1 is turned on. ing.

The switch circuit 8 is connected to a pulse generator 10 that receives a power-on signal and generates a pulse signal having a predetermined width (for example, 1 ms), and is turned on for a pulse signal period to allow a current to flow through the resistor 4. And a switch unit 9.

FIG. 1 shows a load 2 such as a nonvolatile memory such as a CMOS memory, a normally used power supply 1 (for example, 5 V) for supplying power to the load 2 in an on state, and a power supply 1 when the power supply 1 is on. And a resistor for dividing the voltage of the power supply 1 to generate a reference voltage to be input to the comparator 5, and a switch circuit. 8
, And a delay unit 6 that delays the pulse signal (for example, 0.5 ms).

Next, the operation of the battery abnormality detecting circuit according to the present embodiment will be described in detail with reference to FIG.

FIG. 2 is a diagram showing an example of the operation timing according to the embodiment of the present invention. Each state of the detection result from the power supply 1 shown at the left end is shown with time on the horizontal axis. Here, the High state is hereinafter referred to as H, and the Low state is also referred to as Low.
The state is hereinafter described as L, respectively. The detection result in FIG. 2 indicates the content held in the holding unit 7, and is normal (L) at point A,
Each point indicates that an alarm (H) has occurred.

In FIG. 1, when the power supply 1 is turned on (H), a power-on signal (for example, a reset signal) generated by turning on the power supply 1 is supplied to a pulse generator 10 in the switch circuit 8.
And the pulse generator 10 generates a pulse signal having a predetermined width (for example, 1 ms). The pulse signal is input to the switch unit 9 and is turned on during the pulse signal period. That is, for example, the pulse signal is input to the base of the transistor and the transistor is turned on. The resistor 4 connected to the switch unit 9 forms a circuit with the battery 3, and a current flows through the resistor 4 by the battery 3. Comparator 5
The voltage caused by the voltage drop generated in the resistor 4 is compared with a predetermined reference voltage obtained by dividing the voltage of the power supply 1, and an alarm (H) is generated when the voltage caused by the voltage drop generated in the resistor 4 is less than the reference voltage. When the voltage due to the voltage drop generated in step 4 is higher than the reference voltage, the output is normal (L). Holder 7
Receives the pulse signal generated by the pulse generator 10 and delayed by the delay unit 6 and outputs the output of the comparator 5 (the battery 3
(Abnormal or abnormal detection result). The held content can be referred to as a detection result indicating whether the battery 3 is abnormal. Looking at the detection result, when the detection result is an alarm (H), a decrease in the voltage of the battery 3, a failure in mounting the battery 3, a failure in the battery 3, a poor contact between the battery 3 and the circuit, and the like occur. Then, an abnormality can be detected.

In the above description, when the switch circuit 8 receives the power-on signal indicating that the power source 1 has been turned on, a circuit is formed by the battery 3 and the resistor 4 for a predetermined time (for example, 1 ms) and the resistance is changed. 4, and the holding unit 7 sets the output of the comparator 5 to a predetermined time (for example, 0.5 ms) after the switch circuit 8 receives a power-on signal indicating that the power supply 1 is turned on. I try to hold. The switch circuit 8 includes a pulse generator 10 that receives a power-on signal and generates a pulse signal having a predetermined width (for example, 1 ms), and a switch unit 9 that is turned on for a pulse signal period to flow a current to the resistor 4. And is constituted by. However, the switch circuit 8 in FIG.
May be replaced with a switch circuit 11 shown in FIG. 3 showing a switch circuit using a register, and the following may be performed. That is, the switch circuit 11 is connected to the resistor 4 while the power supply 1 is on.
When a command signal for flowing a current is received, a circuit is formed by the battery 3 and the resistor 4 for a predetermined time (for example, 1 ms) so that a current flows through the resistor 4. Holds the output of the comparator 5 after a lapse of a predetermined time (for example, 0.5 ms) from when an instruction signal for flowing a current to the resistor 4 is received while the power supply 1 is on. Is an instruction signal for flowing a current to the resistor 4 while the power supply 1 is on, for example, “
A register section 12 for generating a pulse signal having a predetermined width (for example, 1 ms) when "1" is written by a signal for writing "1";
And a switch unit 9 configured to allow current to flow therethrough. This instruction signal (for example, a signal for writing “1”)
Is a signal from, for example, a microcomputer (not shown). Therefore, the switch section 9 is, for example, a transistor, and when a pulse signal is input to the base, the switch section 9 conducts (turns on), and the resistor 4 connected to the switch section 9 forms a circuit with the battery 3. A current flows through the resistor 4. The holding unit 7 receives the pulse signal generated by the register unit 12 and delayed by the delay unit 6, and holds the output of the comparator 5 (a detection result indicating that the battery 3 is abnormal or normal).

[0020]

As described above, according to the battery abnormality detection circuit of the present invention, a predetermined time is required for generating a voltage drop for checking the voltage of the battery while the power is on by the switch circuit. A current is caused to flow through the resistor (for example, 1 ms), that is, a current is caused to flow through the resistor for a width (for example, 1 ms) of a pulse signal generated in response to a power-on signal or an instruction signal for flowing the current through the resistor. The comparator outputs a detection result indicating whether the battery is abnormal or normal, which is a result of comparing and comparing the voltage due to the voltage drop generated in the resistor with a predetermined reference voltage (when the voltage due to the voltage drop is less than the reference voltage). Is output to the alarm), and the holding unit holds the output of the comparator.
During the period of detecting the abnormality / normality of the battery, the current from the battery flows through the resistor to consume the power of the battery. In this detection period, the width of one pulse signal (for example, 1
ms), battery power consumption can be minimized. Further, when the power is turned off or when a pulse signal is not generated, no current flows from the battery to the resistor and the power of the battery is not consumed, so that the life of the battery is not shortened. Further, since the holding unit holds the detection result indicating that the battery is abnormal or normal, the detection result can be confirmed at any time.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing one embodiment of a battery abnormality detection circuit of the present invention.

FIG. 2 is a diagram showing an example of operation timing according to the embodiment of the present invention.

FIG. 3 is a diagram illustrating a switch circuit using a register.

FIG. 4 is a circuit diagram of a conventional battery abnormality detection circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Power supply 2 Load 3 Battery 4 Resistance 5 Comparator 6 Delay part 7 Holding part 8 Switch circuit 9 Switch part 10 Pulse generation part 11 Switch circuit 12 Register part

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Takeshi Kudo 1-1-25 Shinurashima-cho, Kanagawa-ku, Yokohama-shi, Kanagawa Prefecture F-term in NEC Robot Engineering Co., Ltd. 5G003 DA03 DA13 EA06 5G015 FA08 GB06 HA15 JA06 JA19 JA34 JA53 5H030 AA04 AA08 AS20 FF44

Claims (7)

[Claims] 1. A battery for supplying power to a load when a power supply is turned off, a resistor connected in parallel with the battery and generating a voltage drop for checking a voltage of the battery when a current flows, and a period during which the power supply is on A switch circuit configured to cause a current to flow through the resistor for a predetermined time to generate a voltage drop for checking the voltage of the battery; anda voltage based on the voltage drop generated in the resistor and a predetermined reference voltage. A battery abnormality detection, comprising: a comparator that outputs an alarm when a voltage caused by a voltage drop generated in the resistor is less than the reference voltage; and a holding unit that holds an output of the comparator. circuit. 2. A battery for supplying power to a load when power is turned off, a resistor connected in parallel with the battery and generating a voltage drop for checking a voltage of the battery when a current flows, and wherein the power is turned on. A switch circuit that forms a circuit with the battery and the resistor for a predetermined period of time when receiving a power-on signal indicating that a current flows through the resistor; and A comparator that compares the voltage with a predetermined reference voltage and outputs an alarm when the voltage due to the voltage drop generated by the resistor is less than the reference voltage; anda holding unit that holds the output of the comparator. Characteristic battery abnormality detection circuit. 3. A battery for supplying power to a load when the power is off, a resistor connected in parallel with the battery and generating a voltage drop for checking a voltage of the battery when a current flows, and a period during which the power is on A switch circuit that forms a circuit with the battery and the resistor for a predetermined period of time when an instruction signal for flowing a current to the resistor is received so that a current flows to the resistor; and A comparator that compares the voltage due to the voltage drop with a predetermined reference voltage and outputs an alarm when the voltage due to the voltage drop generated by the resistor is less than the reference voltage; and a holding unit that holds the output of the comparator. A battery abnormality detection circuit, comprising: 4. The method according to claim 1, wherein the holding unit holds the output of the comparator after a predetermined time has elapsed from when the switch circuit receives the power-on signal indicating that the power is turned on. The battery abnormality detection circuit according to claim 2, wherein 5. The holding unit holds an output of the comparator after a predetermined time has elapsed from when the switch circuit receives the instruction signal for flowing a current to the resistor during the power-on period. 4. The battery abnormality detection circuit according to claim 3, wherein: 6. A switch circuit, wherein the switch circuit receives the power-on signal and generates a pulse signal having a predetermined width; and a switch unit which conducts during the pulse signal period and causes a current to flow through the resistor. The battery abnormality detection circuit according to claim 2, comprising: 7. The switch circuit is the instruction signal for flowing a current to the resistor when the power is turned on.
A register unit that generates a pulse signal having a predetermined width when “1” is written by a signal for writing “1”; and a switch unit that conducts during the pulse signal period and allows current to flow through the resistor. The battery abnormality detection circuit according to claim 3, wherein the battery abnormality detection circuit is provided.