JPS60119470A - Circuit for detecting abnormality in supply voltage - Google Patents

Abstract

PURPOSE:To detect even low voltages which are lower than the threshold level of a comparator, by detecting and displaying that a supply voltage is lower than the lowest operating voltage of the comparator. CONSTITUTION:The value of a constant-voltage diode 6 is set in such a way that the value of the voltage across the (+)-side input and (-)-side input of a comparator 5 becomes equal to the lowest operating voltage of a supply voltage. Therefore, when the supply voltage is lower than the lowest operating voltage, a display device 10 lights and informs an operator of the abnormal supply voltage. In the same way, by setting the value of another constant-voltage diode 13 to a prescribed value, another display device 15 lights when the supply voltage is higher than the highest operating voltage. On the other hand, since the set voltage of a constant-voltage diode 3 connected with a resistance 1 and display device 2 is higher than the operable voltage of the comparator 5, the display device 2 does not light when the supply voltage is ''0''V or lower than the operating voltage of the comparator 5.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a power supply voltage abnormality detection circuit in various electronic circuits.

(Prior art) Conventionally, in electronic circuits such as microcomputer systems, in order to detect abnormalities in the power supply voltage supplied to the circuit and notify the operator, multiple comparators are used to detect abnormal voltages at different levels, and LEDs It is common practice to turn on display devices such as

However, such conventional techniques have the disadvantage that abnormally low voltages below the rated voltage of the comparator cannot be detected.

(Purpose) The present invention was made in view of the drawbacks of the conventional example, and an object of the present invention is to provide a power supply voltage abnormality detection circuit that can detect even low voltages below the threshold level of the comparator. It is something to do.

(Structure) The structure of the present invention will be explained below based on the embodiment shown in FIG.

A power supply voltage is passed through a resistor 1, a display device 2 is connected, a cathode of a constant voltage diode 3 is connected, and an anode is grounded. The setting voltage of the constant voltage diode 3 is set to a value higher than the operating voltage of the comparator. With this circuit, the display device 2 is hardly lit when the power supply voltage is 0■ or lower than the operating voltage of the comparator. Therefore, the operator can know that the power supply voltage is O■ or abnormally low.

Also, from the power supply voltage, + of comparator 5 is connected through all resistors 4.
The side and the cathode side of the voltage regulator diode 6 are connected, and the anode side is grounded.

On the other hand, one side of the comparator 5 and the resistor 8 are connected through the resistor 7 from the power supply voltage. The other end of resistor 8 is grounded.

On the output side, the display device 1 is connected from the power supply voltage through the resistor 9.
0 and the other end to the output of comparator 5.

The comparator 5 turns the output side off when there are inputs on the + side > - pieces, and turns on the output side when there are inputs on the + side (manual inputs - pieces).

Further, the value of the constant voltage diode 6 is set so that the voltage values of the + side input and the one side input of the comparator 5 are equal when the power supply voltage is the lowest operating voltage.

With this circuit, when the power supply voltage is below the minimum operating voltage, the display device lights up to notify the operator of a power supply voltage abnormality.

On the other hand, from the power supply voltage, comparator 1 is connected through resistor 11.
Connect one side of 2 and the cathode side of the constant voltage diode 13,
Ground the anode side. The + side of the comparator 12 is connected to one side of the comparator 5, and is connected to the display device 15 through the resistor 14 from the % source voltage as the 0 output side, and the other end is connected to the output of the comparator 12. The value of the constant voltage diode 13 is set so that the value of the +· inputs of the comparator 12 and the value of one side input are equal when the power supply voltage is at the maximum operating voltage.

With this circuit, when the power supply voltage is higher than the maximum operating voltage, the display device 15 lights up to inform the operator of an abnormality in the power supply voltage.

As is clear from the above structure and operation, an abnormality in the power supply voltage can be detected by determining whether the display device R2 is not lit or whether one of the display devices 10.15 is lit.

FIG. 3 is a characteristic diagram showing the state of the display device at each voltage value.

In the figure, vl is the minimum voltage value for comparator operation,
V2 is the voltage value at the connection point between the resistor 4 and the voltage regulator diode 6, V
3 is the voltage value at the connection point of the resistor 11 and the voltage regulator diode 13;
4 indicates the voltage value at the connection point of the resistor 7.8, and 2 indicates the power supply voltage. Further, on the side thereof, the lighting states of the display devices 2, 10.15 corresponding to these (1) to (5) are shown, and furthermore, the normality/abnormality of this combination is shown.

As described above, if the display device 2 is off or any of the display devices 1.0.15 is lit, it is determined that there is an abnormality in the power supply voltage.

(Effects) As described above, according to the present invention, it is possible to accurately check power supply voltage abnormalities, especially low voltage abnormalities that cannot be detected even by a comparator, thereby significantly improving the reliability of electronic circuits.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of an abnormality detection circuit according to an embodiment of the present invention, and FIG. 2 is an explanatory diagram comparing the lighting state of the display device at each voltage level and the normal and abnormal states. 2.10.15...Display device, 5.12...
···comparator.

Claims (1)

[Claims] In an abnormality detection circuit that includes a plurality of comparators and lights up a display device corresponding to these comparators to detect abnormal voltage, a display device that further detects and displays a voltage where the power supply voltage is lower than the minimum voltage at which the comparator can operate. A power supply voltage abnormality detection circuit characterized by being provided with.