JPH1151721A - Storing circuit of integrated value at the tiem of momentary service interruption time - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a circuit which steadily stores integrated values at the time of the momentary service interruption of power. SOLUTION: An IC 71 for monitoring power supply voltage detects the voltage drop of 5 V power due to the momentary service interruption of an a.c. power source 11 and outputs an interruption signal to a microcomputer 8, and the microcomputer 8 starts the writing of integrated values to an E<2> PROM 10. When the 5 V power further drops to a predetermined voltage, an IC 72 for monitoring power supply voltage detects it and resets the microcomputer 8. The 5 V power is held by a condenser 15 so as to complete the writing of integrated values by the time of the reset. In addition, when the 5 V power is risen, the IC 71 releases an interruption signal after the time determined by the capacity of a condenser 74, and then the IC 72 releases a reset signal after the time determined by the capacity of a condenser 75. By this, it is possible to store integrated values steadily even if the momentary service interruption of the a.c. power source 11 continuously occurs.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to the preservation of integrated values at the time of momentary power failure of an electromagnetic flow meter or the like using Faraday's law that a voltage proportional to the speed of a conductive fluid is induced when passing through a magnetic field. .

[0002]

2. Description of the Related Art FIG. 3 is an overall configuration diagram of an electromagnetic flow meter. In FIG. 3, 1 is a detection unit, 2 is an AC amplifier, 3 is an excitation circuit, 4 is a stabilized power supply circuit, 5 is a power transformer, 6
Is an A / D converter, 8 is a microcomputer, 9 is an output circuit, 10 is an E ² PROM, 11 is an AC power supply, 12 is a constant voltage detection circuit, 16 is an exciting coil, 17 is an electrode, and 18 is a measurement tube. . An alternating current is applied from the exciting circuit 3 to the exciting coil 16 provided in the measuring tube 18 to generate an alternating magnetic field, and a voltage proportional to the speed of the conductive fluid flowing in the measuring tube 18 is picked up by the electrode 17. This signal is amplified by the AC amplifier 2, converted to a digital signal by the A / D converter 6, processed by the microcomputer 8, and a flow rate signal per unit time or an integrated flow rate signal is output from the output circuit 9. The set values such as the measurement range necessary for the operation are stored in the E ² PROM 10 and read and used by the microcomputer 8 as needed.

FIG. 4 is a diagram showing a configuration around a conventional power supply detection circuit extracted from FIG. In FIG. 4, the constant voltage detection circuit 12 constantly monitors a digital 5V power supply generated by the stabilized power supply circuit 4 and used by the microcomputer 8 and the like, and the 5V power supply drops to 4.3V due to an instantaneous power failure or the like. When this happens, this is detected and a reset signal for resetting the microcomputer 8 is output.

[0004]

As described above, the electromagnetic flow meter is a flow meter for measuring a flow rate per unit time or an integrated flow rate. In the related art, in the flow measurement by integration, when a momentary power failure occurs in the supplied AC power supply, the microcomputer is reset, that is, the integrated value during measurement is set to zero.

Accordingly, it is an object of the present invention to provide a circuit for stably storing an integrated value when a momentary power failure occurs in a supplied AC power supply.

[0006]

In order to solve the above problems, the present invention provides a microcomputer having a function of integrating input signals, an E ² PROM for storing the integrated signals, and a supply AC power supply. wherein said integration processing signals detected a drop in the internal power supply voltage due to instantaneous power failure of the E ²
A power supply detection circuit for generating a non-maskable interrupt signal for causing the processing to be stored in PROM to said microcomputer, the integrated processed signal the E ² PRO
And a power supply voltage holding circuit for holding the internal power supply voltage at or above a predetermined voltage until writing to M is completed. This allows the integrated value up to the instantaneous power failure to be stored in the E ² PROM while the internal power supply voltage is reduced to the operable voltage level of the digital circuit including the microcomputer by the power supply voltage holding circuit during the momentary power failure of the supplied AC power supply. And the integrated value written after the power supply is restored is read out from the E ² PROM,
The integration process can be continued.

Further, the above-described integrated value storage circuit for instantaneous power failure has a function of releasing the non-maskable interrupt signal after a predetermined time has elapsed after turning on the power, and releasing the reset signal of the microcomputer after a predetermined time has elapsed. The power supply detection circuit provided. As a result, when a momentary power failure occurs again a plurality of times successively before the predetermined time elapses after the momentary power failure recovers once, the integrated value due to the first momentary power failure is saved to the E ² PROM. Is performed, the non-maskable interrupt signal and the reset signal are not released even by a plurality of momentary power failures thereafter, so that the microcomputer is not interrupted and reset, and the digital The reliability of the stored integrated value can be secured by stabilizing the operation of the circuit.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram showing an embodiment of the integrated value storage circuit at the momentary power failure of the present invention. In FIG.
13 is a power supply voltage holding circuit, 14 is a diode, 15 is a capacitor, 7 is a power supply detection circuit, 71 and 72 are power supply voltage monitoring ICs, 73 is an OR circuit, and 74 and 75 are capacitors. 4 and the same reference numerals are used. The difference from FIG. 4 is that a power supply voltage holding circuit 13 is provided between the power supply transformer 5 and the stabilized power supply circuit 4 and the configuration of the power supply detection circuit 7 is different.

FIG. 2 is a timing chart showing the operation of FIG. 1. A 5V power supply, which is a power supply of a digital circuit including a microcomputer, a non-maskable interrupt signal to the microcomputer (interrupt released at high level, interrupt generated at falling edge) And the operation of the reset signal to the microcomputer (the reset is released at a high level), and when the supplied AC power supply 11 is turned on and off, and when a momentary power failure occurs, it is indicated by ↓. The operation of the present invention will be described with reference to FIG.

First, when an instantaneous power failure occurs in a state where the supply AC power supply 11 is turned on and the circuit is operating normally, the voltage drop of the 5V power supply starts. The power supply voltage monitoring IC 71 detects this, and outputs a non-maskable interrupt signal (falling signal in the figure) to the microcomputer 8, and the microcomputer 8 starts writing the integrated value to the E ² PROM 10. During this time, the voltage of the 5 V power supply further decreases. When the voltage reaches a predetermined voltage, the power supply voltage monitoring IC 72 detects this and outputs a reset signal to the microcomputer 8. The time from the occurrence of the momentary power failure to the output of the reset signal is indicated by TW. It takes about several tens of milliseconds to write the integrated value to the E ² PROM 10, but the capacity of the capacitor 15 of the power supply voltage holding circuit 13 may be determined so that a reset signal is output after the writing is completed.

Next, the time when the supplied AC power supply 11 is turned on.
However, when the 5V power supply rises, T_PDPower supply after hours
The visual IC 71 cancels the non-maskable interrupt signal.
You. T _PDThe time is determined by the capacity of the capacitor 74
You. Further, an IC for monitoring the power supply voltage via the OR circuit 73
T by 72_RSTAfter a time, the reset signal is released. T
_{RS T}The time is determined by the capacity of the capacitor 75.

[0012] If the supplied AC power supply 11 is a power failure continuously blinking, i.e. when repeated that power outage again Shun within T _PD time after power recovery from the instantaneous power failure, the power supply voltage monitoring IC71 is a non-maskable interrupt signal It is not released, and therefore the reset signal is not released. Therefore, every time the microcomputer 8 continuously loses power, the integrated value is read out from the E ² PROM 10 at the time of power recovery and written into a calculation area of a memory (not shown). It is possible to prevent a situation in which the integrated value is written into the E ² PROM 10 due to the next momentary power failure.

[0013]

[Effect of the Invention] As described above, according to the present invention, it is possible to store write to E ² PROM integrated value at the time of instantaneous power failure, it is possible to continue the integration process reads the data at the time of power recovery . Also, when using a power supply of poor quality, such as large fluctuations in the power supply voltage, or when there is a risk of continuous power failure due to lightning, etc., the operation of digital circuits including microcomputers should be stabilized. can be achieved, it is possible to ensure the reliability of the integrated value written in the E ² PROM.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a timing chart showing the operation of FIG.

FIG. 3 is an overall configuration diagram of an electromagnetic flow meter.

FIG. 4 is a configuration diagram showing a conventional example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Detection part, 2 ... AC amplifier, 3 ... Excitation circuit, 4 ... Stabilized power supply circuit, 5 ... Power supply transformer, 6 ... A / D converter, 7
... power supply detection circuit, 8 ... microcomputer, 9 ... output circuit, 10 ... E ² PROM, 11 ... AC power source, 12 ... constant voltage detection circuit, 13 ... power supply voltage holding circuit, 14 ... diodes, 15 ... capacitor, 16 ... Excitation coil, 17 ... Electrode, 18 ... Measuring tube, 71, 72 ... Power supply voltage monitoring IC,
73 ... OR circuit, 74, 75 ... capacitors.

Claims (2)

[Claims] 1. A microcomputer having a function of multiplying an input signal, and an E for storing the multiplied signal.
² PROM and the said accumulation processing signals detected a drop in the internal power supply voltage due to instantaneous power failure of the supply alternating-current power supply E ² P
A power supply detection circuit for generating an interrupt signal (hereinafter referred to as a non-maskable interrupt signal) for causing the microcomputer to perform processing to be stored in the ROM; and a predetermined internal power supply voltage until the integrated signal is completely written into the E ² PROM. And a power supply voltage holding circuit for holding the power supply voltage at or above the voltage of the instantaneous power failure. 2. The integrated value storage circuit according to claim 1, wherein said non-maskable interrupt signal is released after a predetermined time has elapsed after power-on, and a reset signal of said microcomputer is generated after a predetermined time has elapsed. A momentary power failure integrated value storage circuit, characterized in that the power supply detection circuit has a function of canceling.