JP2003215177A - Electronic equipment having function for detecting service interruption and restoration - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electronic equipment that monitores service restoration at a low electric power consumption. <P>SOLUTION: In this electronic equipment provided with a power source circuit 3, a back-up electric power source 5, and a service interruption and restoration detecting circuit 1 comprising a micro computer 11 having an input terminal T112 for A/D conversion, an interruption terminal T111, a function for monitoring service interruption and restoration in a power source circuit, an operation mode changing function for switching an operation for the micro computer between a usual operation mode and a low power consumption mode, and a function for controlling an operation for the electronic equipment, a service interruption and restoration detecting signal for indicating whether the power source circuit 3 is under the service interruption or the service restoration is supplied to a terminal T113, an output voltage of the power source circuit 3 is supplied to the terminal T111, shifting to the low power consumption mode is conducted when the service interruption and restoration detecting signal indicates the service interruption, and restoration to the usual operation mode is conducted when the service restoration of the power source to the terminal T111 is detected. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic device using a microcomputer having an A / D conversion function such as an electronic watt-hour meter, and more particularly, it consumes a low power consumption for recovery monitoring operation by battery backup at the time of power failure. The present invention relates to an electronic device having a power recovery and restoration detection function that is performed with electric power.

[0002]

2. Description of the Related Art In electronic equipment such as an electronic watt hour meter which is backed up by a battery in the event of a power failure,
A power failure detection and power recovery detection are performed by a power failure and power recovery detection method configured by hardware as shown in FIG. 8 and a power failure and power recovery detection method by software having a microcomputer as shown in FIG.

An electronic device equipped with a power failure / recovery detection means consisting of the hardware shown in FIG. 8 is composed of a power failure / recovery detection circuit 1, a power supply circuit 3, a backup power supply 5, and an electronic device body 7. .

The power recovery / recovery voltage detection circuit 1 comprises a power recovery / recovery voltage detection circuit 12 including a resistor 121 and a resistor 122 connected in series.
And a hysteresis comparator 15 in which the output of the recovery voltage detection circuit 12 is supplied to one input terminal and the output of a reference voltage circuit 17 described later is supplied to the other terminal, and one is connected to the recovery voltage detection circuit 12. The other is a resistor 161 and a resistor 1 connected to the power failure detection signal T73 of the electronic device 7.
The power failure detection / recovery detection signal circuit 16 including 62 and the constant voltage diode 163, and the reference voltage circuit 17 including the resistor 171 and the constant voltage diode 172 connected in series.

The power supply circuit 3 has a transformer 31 whose primary side is connected to a commercial power source, a rectifier 32 connected to the secondary side of the transformer 31, and a secondary side of the transformer 31 connected in parallel. The smoothing capacitor 33 and the output connected to the smoothing capacitor in parallel are the backup power supply circuit 5 and the reverse current blocking diode 3.
5 and a backflow prevention diode 35 connected to the non-backup power supply terminal T71 of the electronic device.

The backup power source 5 comprises a power storage means 51 such as a primary battery, a backflow blocking diode 52, and a backflow blocking diode 53, and the output is supplied to the backup power terminal T72 of the electronic device 7. It

Such a hysteresis comparator 15
The electronic device using the power recovery / restoration voltage detection means using the circuit requires the hysteresis comparator 15 and the power recovery / restoration detection signal circuit 16.

As shown in FIG. 9, an electronic device equipped with a power failure / recovery detecting means for detecting a power failure or power recovery by a power failure / recovery detection method using software with a built-in microcomputer,
The power failure detection circuit 1 includes a power supply circuit 3, a backup power supply 5, and an electronic device body 7.

The recovery / recovery voltage detection circuit 1 is a recovery / recovery voltage detection circuit 1
2 output is input to A / D input terminal T112
It is composed of a microcomputer 11 having a conversion function, and a recovery voltage detection circuit 12 including a resistor 121 and a resistor 122 connected in series.

The power supply circuit 3 has a transformer 31 whose primary side is connected to a commercial power source, a rectifier 32 connected to the secondary side of the transformer 31, and a secondary side of the transformer 31 connected in parallel. The smoothing capacitor 33 and the output connected to the smoothing capacitor in parallel are the backup power supply circuit 5 and the reverse current blocking diode 3.
5 and a backflow prevention diode 35 connected to the non-backup power supply terminal T71 of the electronic device.

The backup power supply 5 comprises a power storage means 51 such as a primary battery, a backflow blocking diode 52, and a backflow blocking diode 53, and the output is supplied to the backup power terminal T72 of the electronic device 7. It

As described above, in a device having a battery backup, the microcomputer is generally used in a low power consumption mode during a power failure, and then returned to the normal operation mode by power recovery. In this case, if there is a hardware power failure detection circuit, changes in the output signal can be caught by interrupts of the microcomputer and returned to the normal operation mode, but power failure is detected by the A / D conversion function and software built into the microcomputer. In that case, it is necessary to periodically operate the microcomputer with a timer or the like to check the power supply state by the A / D conversion function to detect power recovery.

The flow of the interval timer routine R4 for generating hysteresis in the microcomputer 11 in the relationship that the power failure level is smaller than the power recovery level will be described with reference to FIG. The microcomputer 11 has an A / D input terminal T11
The power failure / restoration detection signal input to 2 is A / D converted (S6
1), it is determined whether or not there is a power outage (S62). When there is no power outage, it is determined whether or not the A / D converted stop / recovery detection signal is below the power outage level (S63). When the power recovery / restoration detection signal converted from A / D is below the power failure level,
A power failure shift process is executed (S64), and a low power consumption mode is entered (S65).

If it is determined in step S62 that a power failure is occurring, it is determined whether the A / D converted stop / recovery detection signal is equal to or higher than the power recovery level (S66). When the power recovery / restoration detection signal converted from A / D is above the power recovery level,
Power recovery transition processing is executed (S67), and the interval timer routine is ended (S68).

If it is determined in step S63 that the A / D converted power failure / restoration detection signal is not lower than the power failure level, the interval timer routine is terminated (S68).

In step S66, when the A / D-converted power recovery / restoration detection signal is not higher than the power recovery level, the low power consumption mode is entered (S65).

In this way, hysteresis can be generated in the relationship of power failure level <power recovery level.

Comparing the costs for detecting the power failure and restoration, the number of parts is higher in the case of having a hardware circuit,
In the method using the A / D conversion function of the microcomputer, if the operation interval for detecting the power recovery is set to be short, a large capacity of the battery for backing up is required and the cost is increased.

From the viewpoint of the number of parts, the method of detecting power failure / recovery by the A / D conversion function of the microcomputer is more advantageous from the viewpoint of cost, but in order to suppress the power consumption at the time of backup, detection of power recovery is performed. Must be performed independently of the A / D conversion function.

[0020]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides an electronic device having a microcomputer having an A / D conversion function and having a power failure / restoration detection function for detecting power failure / restoration by software. In view of the above, it is an object of the present invention to provide an electronic device having a power failure recovery detection function capable of performing power recovery monitoring with low power consumption without increasing the capacity of a backup power supply.

[0021]

In order to solve the above-mentioned problems, the present invention uses a microcomputer having an A / D conversion function and uses the A / D conversion function to reduce the power consumption of the device power supply. In a device having a backup power supply that uses electric power, detection of power recovery is performed by connecting a power supply voltage that does not perform backup to a terminal that recovers from the low power consumption operation of the microcomputer, and recovers to normal operation.

Further, according to the present invention, the microcomputer having the A / D conversion function is used to detect the power failure / recovery of the equipment power source.
In a device that has a backup power supply that operates in the low power consumption mode by the conversion function, connect the power supply voltage that is not backed up to the terminal that recovers from the low power consumption operation via a limiting resistor, and switch the input / output separately from this terminal. Also connect this terminal to this terminal, output a low voltage from another terminal while the power supply voltage that does not perform backup after a power failure is falling, and input another terminal after the power supply voltage that does not perform backup has dropped sufficiently. Switching, detection of power recovery after that, and return to normal operation.

Further, in order to solve the above problems, the present invention provides a power supply circuit for supplying a voltage to an electronic device and a microcomputer, a backup power supply for supplying a voltage to the microcomputer at the time of a power failure, and an A / D conversion input terminal. In an electronic device having a power failure / recovery detection function including a power failure / recovery detection circuit including a microcomputer having an interrupt terminal, the microcomputer has a power failure / recovery monitoring function for monitoring power failure and recovery of a power supply voltage, and a microcomputer It has an operation mode changing function for shifting the operation mode between the normal operation mode and the low power consumption mode, and a function for controlling the operation of the electronic device, and indicates whether the power supply circuit is in a power failure or a power supply. Supplying the power failure / restoration detection signal to the A / D conversion input terminal, supplying the output voltage of the power supply circuit to the interrupt terminal, and operating the microcomputer when the power failure / restoration detection signal indicates a power failure. Over de it is shifted to the low power consumption mode which is operated by electric power from a backup power supply, and so as to return the operation mode of the microcomputer to the normal operation mode upon detection of a restoration of power supply to the interrupt terminal.

Further, the present invention provides the electronic device having the above-mentioned power failure recovery function, wherein the microcomputer has an input / output switchable terminal capable of changing a terminal state to an output state or an input state, and the power supply circuit. An output state in which the output voltage of the input / output switchable terminal is supplied to the interrupt terminal and the input / output switchable terminal via a limiting resistor and the input / output switchable terminal outputs a low voltage when the power failure / restoration detection signal indicates a power failure. After that, the input / output switchable terminal is set to the input state to perform power recovery monitoring.

According to the present invention, in the electronic device having the function of detecting power failure and recovery, the microcomputer has an input / output switchable terminal capable of changing the state of the terminal to an output state or an input state, and the output of the power supply circuit. A voltage is supplied to the interrupt terminal and the input / output switchable terminal via a limiting resistor, and the input / output switchable terminal is set to an output state of outputting a low voltage when the power failure / restoration detection signal indicates a power failure, When the output voltage of the power supply circuit drops to a voltage at which an input through current does not occur at the interrupt terminal, the input / output switchable terminal is changed from the output state to the input state to perform power recovery monitoring.

According to the present invention, in the electronic device having the above-mentioned power failure / restoration detection function, the microcomputer can change the state of the terminal to an output state or an input state, and an input / output switchable terminal,
A second A / D conversion input terminal different from the A / D conversion input terminal is provided, and the power failure / restoration detection circuit is connected to an output of the power supply circuit that outputs a non-backup voltage detection signal. A backup voltage detection circuit is provided, the output voltage of the power supply circuit is supplied to the interrupt terminal and the input / output switchable terminal via a limiting resistor, and the non-backup voltage detection signal is input to the second A / D conversion input terminal. When the power failure / recovery detection signal indicates a power failure, the input / output switchable terminal is set to an output state that outputs a low voltage, and the output voltage of the power supply circuit is set to a voltage that does not cause an input through current at the interrupt terminal. When it is detected by the input of the second A / D conversion input terminal that the input / output switchable terminal is changed from the output state to the input state, power recovery monitoring is performed.

According to the present invention, in the above electronic device, when the interrupt terminal for recovering from the low power consumption operation is an input / output switchable terminal, the backup power supply voltage is restored while the power supply voltage not backed up after a power failure is falling. The terminal is switched to the output terminal to output a low voltage, and the terminal that restores the backup power supply voltage is switched to the input terminal after the power supply voltage that does not perform the backup has dropped sufficiently to return to the normal operation of power recovery detection.

[0028]

BEST MODE FOR CARRYING OUT THE INVENTION An outline of the configuration of an electronic device having a power failure / restoration detection function according to the present invention will be described with reference to FIG.

As shown in FIG. 1, a power failure / recovery detection function that incorporates a microcomputer according to the present invention, such as an electronic watt hour meter, and performs power failure detection and power recovery detection by a software power failure recovery method. An electronic device equipped with
The power failure detection circuit 1 includes a power supply circuit 3, a backup power supply 5, and an electronic device body 7.

The power recovery / restoration detection circuit 1 comprises a microcomputer 11 having an A / D conversion function and having an interrupt terminal T111 and a first A / D input terminal T112, a resistor 121 and a resistor 122 connected in series, and a connection point. A is composed of the recovery voltage detection circuit 12 connected to the first A / D input terminal T112 of the microcomputer 11.

The power supply circuit 3 has a transformer 31 whose primary side is connected to a commercial power source, a rectifier 32 which is connected to the secondary side of the transformer 31, and a secondary side of the transformer 31 which is connected in parallel. The smoothing capacitor 33 and the output connected to the smoothing capacitor in parallel are the backup power supply circuit 5 and the reverse current blocking diode 3.
5 and a reverse voltage blocking diode 35 connected to the non-backup power supply terminal T71 of the electronic device and the interrupt terminal T111 of the microcomputer 11.

The backup power supply 5 is configured to have a power storage means 51 such as a primary battery, a backflow blocking diode 52, and a backflow blocking diode 53, and the output is supplied to the backup power terminal T72 of the electronic device 7. . The series circuit of the power storage means 51 and the reverse current element diode 52 is
It is connected in parallel to the constant voltage circuit 34 via the reverse current blocking diode 53, and is also connected to the AVcc terminal and Vcc terminal of the microcomputer 11, the GND terminal and the AGND terminal.

The interrupt terminal T111 of the microcomputer 11 is a terminal capable of returning to the normal mode when an interrupt occurs due to a signal change of the microcomputer 11. By connecting a power supply that does not perform backup to the interrupt terminal T111, an interrupt occurs at power recovery and returns to the normal mode. Therefore, the microcomputer is operated periodically to monitor power recovery and A / D conversion is performed. Power recovery can be detected without

However, in this connection as it is, the potential becomes an intermediate value during the voltage drop of the power supply which is not backed up immediately after the power failure, and the interrupt terminal T111 of the microcomputer 11 is shown in FIG.
The input through current shown by the solid line is generated. It is not uncommon for the load of the power supply that does not perform backup to operate at a low voltage of approximately the intermediate potential, and its falling speed may be on the order of several seconds, depending on the circuit. Therefore, even when the input through current is generated, it is generated in this order, and the current is supplied from the battery for backup, which consumes the battery significantly. If the internal impedance of the battery is high, the generation of the input shoot-through current for several seconds may cause a voltage drop and hinder the backup operation.

A second embodiment of the present invention which solves this problem will be described with reference to FIG. In this embodiment, the power supply 3 that does not perform backup via the reverse current blocking diode 35.
It is characterized in that the limiting resistor 13 is inserted between the interrupt terminal T111 and the interrupt terminal T111, and an input / output switchable terminal T113 capable of switching input / output is connected in parallel to the interrupt terminal T111. When the microcomputer 11 monitors the input of the recovery voltage detection circuit 12 and detects that the input voltage has become a predetermined value or less, the input / output switchable terminal T113 is
A low voltage is output until the voltage of the power supply 3 that does not perform backup drops to a voltage that does not generate input through current. By this, the interrupt terminal T111 via the limiting resistor 13
The voltage of the power source 3 supplied to the input / output switchable terminal T1
The voltage is the same as that of No. 13 and no input through current is generated. After a lapse of time for the voltage of the power supply 3 to drop to a voltage that does not generate input through current, the input / output switchable terminal T113
After switching to input, shift to low power consumption mode,
The power recovery can be monitored, the interrupt can detect the rising of the interrupt terminal T111, the power recovery can be detected, and the microcomputer can be returned to the normal mode.

Here, during the period in which the input / output switchable terminal T113 outputs a low voltage, the power supply 3 that does not perform backup
It is also possible to use a value obtained by actually measuring the time required for the voltage to drop to a voltage at which an input through current does not occur.

The interval timer routine R3 when the non-backup voltage detection signal input is not confirmed will be described with reference to FIG.

The microcomputer 11 has a first A / D input terminal T1.
The power failure / recovery detection signal input to 12 is A / D converted (S4
1), it is determined whether the A / D conversion result is equal to or lower than the power failure level (S42). When the power failure / restoration detection signal exceeds the power failure level, the interval timer routine R3 is ended (S54). When the power failure detection signal is below the power failure level, execute the power failure transition processing including timer stop
Simultaneously with (S43), the input / output switchable terminal T113 is switched to the low voltage level output (S44), and the count of the drop of the non-backup voltage is started (S45). Next, the power recovery / restoration detection signal input to the first A / D input terminal T112 is A / D converted (S46), and it is determined whether the A / D conversion result is equal to or higher than the power recovery level (S47).

If the A / D conversion result is equal to or higher than the power recovery level in step S47, the input / output switchable terminal T113 is switched to input (S52), and power recovery transition processing including timer restart is executed ( (S53), the interval timer routine R3 is ended (S54).

If the A / D conversion result is less than the power recovery level in step S47, it is monitored whether or not the voltage drop count is finished (S48), and the process returns to step S46 until the voltage drop count is finished. , Continue counting non-backup voltage drop. When the voltage drop count is completed in step S48, the input / output switchable terminal T113 is switched from the low voltage output to the input (S49), the low power consumption mode is set, and the power recovery monitoring state is set (S50).

Interrupt terminal T111 while monitoring power recovery
If the voltage rises at the point, the recovery from the low power consumption mode to the normal state is set (S50), and the mode shifts to the low power consumption mode (S51).

As described above, the method of setting the low voltage output period of the input / output switchable terminal T113 is changed to the voltage of the power source 3 not backed up as shown in FIG.
There is a method of inputting to the second A / D input terminal T114 via the non-backup voltage detecting means 14 composed of a series circuit of 41 and a resistor 142, A / D converting it, and accurately detecting power failure / restoration. The interval timer routine R1 processing of the power recovery / restoration detection processing in the microcomputer 11 in this case will be described with reference to the chart of FIG.

The microcomputer 11 has a first A / D input terminal T1.
The power failure / recovery detection signal input to 12 is A / D converted (S
1), it is determined whether or not the A / D conversion result is equal to or lower than the power failure level (S2). When the power failure / restoration detection signal is lower than the power failure level, the power failure transition processing including the timer stop is executed (S3), and the input / output switchable terminal T113 is switched to the low voltage level output (S4). The non-backup voltage detection signal input to the input terminal T114 is A / D converted (S5).

Whether or not the input flow-through current is a non-backup voltage at which the value is sufficiently small is determined (S6). When the detected non-backup voltage is a sufficiently low voltage, the input flow-through current does not occur. The input / output switchable terminal T113 is switched from the low voltage output to the input (S7), the low power consumption mode is set, and the power recovery monitoring state is set.

Interrupt terminal T111 while monitoring power recovery
If the voltage rises at the point, the recovery from the low power consumption mode to the normal state is set (S8), and the mode shifts to the low power consumption mode (S9).

When the non-backup voltage is not sufficiently low in step S6, the power failure / restoration detection signal input to the first A / D input terminal T112 is A / D converted (S10), and A / D conversion is performed.
It is determined whether the D conversion result is equal to or higher than the power recovery level (S1
1). When the power recovery level is not reached, the process returns to step S5. When the power recovery detection signal is equal to or higher than the power recovery level, the input / output switchable terminal T113 is switched to the input (S12), the power recovery transition process including the timer restart is executed (S13), and the interval timer routine R1 is executed. It ends (S14).

Next, the interrupt routine R2 at the interrupt terminal T111 when returning from the low power consumption mode will be described with reference to FIG. The microcomputer 11 performs A / D conversion on the power recovery / restoration detection signal input to the first A / D input terminal T112 (S21), and determines whether the A / D conversion result is equal to or higher than the power recovery level ( S22). When the power failure detection signal is above the power recovery level, the power recovery transition processing is executed (S
32), the interrupt routine R2 is ended (S33). When the power recovery / restoration detection signal does not reach the power recovery level in step S22, the input / output switchable terminal T113 is switched to the low voltage level output (S23), and the second A / D input terminal T
The non-backup voltage detection signal input to 114 is A /
D conversion is performed (S24).

It is determined whether or not the A / D converted non-backup voltage is sufficiently low (S25). If it is low, the input through current does not occur, so the input / output switchable terminal T113 is set to a low voltage. The output is switched to the input (S26), the low power consumption mode is set, and the power recovery monitoring state is set.

Interrupt terminal T111 while monitoring power recovery
If the voltage rises at the point, the recovery from the low power consumption mode to the normal state is set (S27), and the mode shifts to the low power consumption mode (S28).

If the non-backup voltage is not sufficiently low in step S25, the power failure / restoration detection signal input to the first A / D input terminal T112 is A / D converted (S29), and A / D conversion is performed.
It is determined whether the D conversion result is equal to or higher than the power recovery level (S3
0). If the power recovery level is not reached, step S24
Return to. When the power recovery detection signal is equal to or higher than the power recovery level, the input / output switchable terminal T113 is switched to the input (S31), the power recovery transition process including the timer restart is executed (S32), and the interrupt routine R2 ends. Do (S
33).

As described above, in the present invention, it is more certain to confirm the power recovery by the A / D conversion function after the microcomputer returns to the normal mode.

When the input through current value and its time are not a problem, power recovery monitoring can be performed with low power consumption even if the power failure recovery circuit shown in FIG. 1 is provided. Furthermore, as shown in FIGS. 3 and 4, it is also effective to use a method in which the fall time of the power supply that does not perform backup is set to a constant value by actual measurement in advance.

[0053]

According to the present invention, by using a microcomputer having an A / D conversion function, it is possible to detect power failure / restoration at low cost in a device that performs low power consumption operation by battery backup.

[Brief description of drawings]

FIG. 1 is a block diagram illustrating an outline of a configuration of an electronic device including a power failure / restoration detection circuit according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating an input through current of a C-MOS IC.

FIG. 3 is a block diagram illustrating an outline of a configuration of an electronic device including a power failure / restoration detection circuit according to a second embodiment of the present invention.

FIG. 4 is a flowchart illustrating processing of an interval timer routine of the microcomputer in FIG.

FIG. 5 is a block diagram illustrating an outline of a configuration of an electronic device including a power failure / restoration detection circuit according to a third embodiment of the present invention.

FIG. 6 is a flowchart illustrating processing of an interval timer routine of the microcomputer shown in FIG.

7 is a flowchart illustrating processing of an interrupt routine of the microcomputer shown in FIG.

FIG. 8 is a block diagram illustrating a configuration of an electronic device including a conventional power restoration / recovery detection circuit using a hysteresis comparator.

FIG. 9 is a block diagram illustrating the configuration of an electronic device having a power failure and power recovery detection function using a conventional microcomputer.

10 is a flowchart illustrating processing of an interval timer routine of the microcomputer shown in FIG.

[Explanation of symbols]

1 Restoration voltage detection circuit 11 Microcomputer 12 Restoration voltage detection circuit 13 Limiting resistance 14 Non-backup voltage detection circuit 15 Hysteresis comparator 17 Reference voltage source 3 power supply circuit 31 transformer 32 rectifier 33 Smoothing capacitor 34 constant voltage circuit 35 Backflow prevention diode 5 Backup power supply 51 power storage means 52 Backflow prevention diode 53 Backflow prevention diode 7 Electronic device body T111 interrupt terminal T112 1st A / D conversion input terminal T113 I / O switchable terminal T114 Second input terminal for A / D conversion

Claims (5)

[Claims] 1. A power recovery circuit comprising a power supply circuit for supplying a voltage to an electronic device and a microcomputer, a backup power supply for supplying a voltage to the microcomputer in the event of a power failure, and a microcomputer having an A / D conversion input terminal and an interrupt terminal. In an electronic device having a power failure and power recovery detection function including a circuit, the microcomputer has a power failure and power recovery monitoring function for monitoring power failure and restoration of the power supply voltage, and the operation modes of the microcomputer are a normal operation mode and a low power consumption mode. And a function to change the operation mode of the electronic device and a function to control the operation of the electronic device, and a power failure recovery signal indicating whether the power supply circuit is in a power failure or a current is used for the A / D conversion. Supply to the input terminal, supply the output voltage of the power supply circuit to the interrupt terminal, and operate the microcomputer operation mode by the power from the backup power supply when the power failure / restoration detection signal indicates a power failure. That is shifted to the low power consumption mode, an electronic device having a Tomafuku electrostatic detection, characterized in that to return the operation mode of the microcomputer to the normal operation mode upon detection of a restoration of power supply to the interrupt terminal. 2. The microcomputer has an input / output switchable terminal capable of changing a terminal state to an output state or an input state, and outputs the output voltage of the power supply circuit to the interrupt terminal and the input / output through a limiting resistor. Supply the power to the switchable terminal and put the input / output switchable terminal in the output state to output a low voltage when the above-mentioned power failure / restoration detection signal indicates a power failure. The electronic device having the power failure / restoration detection function according to claim 1. 3. The microcomputer has an input / output switchable terminal capable of changing a terminal state to an output state or an input state, and outputs the output voltage of the power supply circuit to the interrupt terminal and the input / output through a limiting resistor. The output voltage of the power supply circuit is input to the interrupt terminal by supplying the switchable terminal to the output state in which the input / output switchable terminal outputs a low voltage when the power failure / restoration detection signal indicates a power failure. The power failure recovery detection function according to claim 1, wherein the input / output switchable terminal is changed from an output state to an input state to perform power recovery monitoring when the voltage is reduced to a voltage that does not cause a power failure. Electronics. 4. The input / output switchable terminal capable of changing a terminal state to an output state or an input state, and a second A / D conversion input terminal different from the A / D conversion input terminal. The power recovery circuit includes a non-backup voltage detection circuit connected to the output of the power supply circuit that outputs a non-backup voltage detection signal, and the output voltage of the power supply circuit is interrupted via a limiting resistor. Input to the terminal and input / output switchable terminal, the non-backup voltage detection signal is supplied to the second A / D conversion input terminal, and the input / output can be switched when the power failure / restoration detection signal indicates a power failure. The terminal is set to an output state for outputting a low voltage, and it is detected by the input of the second A / D conversion input terminal that the output voltage of the power supply circuit has dropped to a voltage at which an input through current does not occur at the interrupt terminal. Sometimes before The electronic device having a power failure / recovery detection function according to claim 1, wherein a recovery output monitoring is performed by changing a writing output switchable terminal from an output state to an input state. 5. When the interrupt terminal for recovering from the low power consumption operation is an input / output switchable terminal, a terminal for recovering the backup power supply voltage is switched to an output terminal while the power supply voltage not backed up after a power failure is falling. 3. A low voltage is output, and after the power supply voltage for which backup is not performed has dropped sufficiently, the terminal for restoring the backup power supply voltage is switched to the input terminal to restore normal operation for power recovery detection. Item 5. The electronic device according to any one of items 4.