JPH10160767A - Voltage drop detection circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a circuit for detecting voltage drop with respect to a plurality of decision levels without causing any cost increase. SOLUTION: A series circuit of a switch 2 and a resistor 4 and a series circuit of a switch 3 and a resistor 5 are connected in parallel with a voltage 1 to be measured. Furthermore, a resistor 6 is connected in series with the voltage 1 to be measured and a comparator 7 is connected across the resistor 6 in order to compare the potential at the opposite ends of the resistor 6. Current supply from the voltage 1 to be measured to the resistors 4, 5 is subjected to time sharing switching thus switching the voltage drop decision level for the voltage 1 to be measured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a voltage drop detecting circuit for detecting a voltage drop in a voltage to be measured.

[0002]

2. Description of the Related Art FIG. 3 is a circuit diagram showing a configuration example of a conventional voltage drop detection circuit. In this conventional example, as shown in FIG. 3, resistors 14 and 16 which are connected in series with the voltage under measurement 11 and divide the voltage under measurement 11 are compared with the potentials at both ends of the resistor 16, and the comparison result is output. And a comparator 17 which performs the operation.

The operation of detecting the voltage drop of the voltage to be measured in the voltage drop detection circuit configured as described above will be described below. First, when the measured voltage 11 is externally applied, the applied measured voltage is divided by the resistors 14 and 16, and the potentials at both ends of the resistor 16 are compared by the comparator 17. In the comparison by the comparator 17, when the potential difference between both ends of the resistor 16 becomes equal to or more than the set value in the comparator 17, the voltage to be measured 11
Is output from the comparator 17 as the measured voltage measurement result signal a, and when the potential difference between both ends of the resistor 16 becomes smaller than the set value in the comparator 17, the measured voltage decreases. A signal indicating that the voltage drop of 11 is a value exceeding a predetermined value is output from the comparator 17 as a measured voltage measurement result signal a.

[0004] Here, the resistance values of the resistors 14 and 16 and the set value of the comparator 17 are set in advance to values that can detect a desired amount of decrease in the voltage under measurement.

[0005]

In the prior art as described above, only one set value can be set in the comparator. Therefore, the amount of voltage drop of the voltage to be measured is equal to or smaller than a predetermined value. When detecting whether the value exceeds the value, there is a problem that the detection can be performed only for one determination level and cannot be detected for a plurality of predetermined values. For example, when it is detected that the voltage drop of the voltage to be measured is equal to or less than a predetermined value, the voltage drop amount of the voltage to be measured is further finely detected, or the voltage drop of the voltage to be measured exceeds the predetermined value. When the value is detected, it is not possible to further detect how much the measured voltage has dropped. Therefore, it is conceivable to detect the voltage drop of the voltage to be measured in detail by using a plurality of circuits. In that case, however, a plurality of expensive comparators must be provided, which causes a problem of increasing the cost. is there.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and detects a decrease in the voltage to be measured with respect to a plurality of judgment levels without increasing the cost. It is an object of the present invention to provide a voltage drop detection circuit that can perform the above-described operation.

[0007]

In order to achieve the above object, the present invention comprises a first and a second resistor connected in series with a voltage to be measured and dividing the voltage to be measured; A voltage drop detection circuit comprising: a voltage comparison circuit configured to compare the potentials at both ends of the resistor and compare the comparison result with a preset value to detect a voltage drop of the measured voltage. A plurality of the first resistors are provided so as to have different resistance values from each other and to be connected in parallel with the measured voltage, and a current is supplied to the first resistor by the measured voltage. It is characterized by having switching means for switching to division.

[0008] The switching means is a switch connected in series to each of the plurality of first resistors. In addition, the switching means includes a plurality of the first
And a photocoupler connected in series to each of the resistors.

(Operation) In the present invention configured as described above, the voltage to be measured is divided by the first and second resistors connected in series to the voltage to be measured, and The potentials at both ends of the resistor 2 are compared,
Further, the voltage drop of the measured voltage is detected by comparing the comparison result with a predetermined set value. However, the first resistors have different resistance values from each other, and Even if the voltage to be measured and the set value in the comparison means are the same, the switching means can supply current to each first resistor by the voltage to be measured, By switching to division, the potential difference between both ends of the second resistor is different, and the judgment level of the voltage drop with respect to the measured voltage is switched.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an embodiment of a voltage drop detection circuit according to the present invention, which is a circuit that detects two types of voltage drops for one voltage to be measured. As shown in FIG. 1, in this embodiment, a switch 2 and a resistor 4 as a first resistor connected in series and a switch 3 and a first switch as a switch connected in series are connected. A resistor 5, which is a resistor, is connected in parallel to the measured voltage 1, and a resistor 6, which is a second resistor, is connected in series to the measured voltage 1. To both ends of the resistor 6, a comparator 7 which is a comparing means for comparing potentials at both ends of the resistor 6 and outputting a comparison result is connected.

The operation of detecting the voltage drop of the voltage to be measured in the voltage drop detection circuit configured as described above will be described below. The switches 2 and 3 are turned on in a time sharing manner. When the voltage under test 1 is applied from the outside while the switch 2 is conducting, the applied voltage under test is divided by the resistors 4 and 6, and the potentials at both ends of the resistor 6 are compared by the comparator 7. In the comparison by the comparator 7, when the potential difference between both ends of the resistor 6 becomes equal to or more than the set value in the comparator 7,
A signal indicating that the voltage drop of the voltage under measurement 1 is equal to or less than a predetermined value is output from the comparator 7 as a voltage measurement result signal a to be measured, and the potential difference between both ends of the resistor 6 is determined by the comparator 7.
Is smaller than the set value, a signal indicating that the voltage drop of the voltage under measurement 1 exceeds a predetermined value is output from the comparator 7 as the voltage measurement result signal a to be measured.

Thereafter, the switch 2 becomes non-conductive,
When the switch 3 is turned on, the measured voltage 1
Is applied, the applied voltage to be measured is divided by the resistors 5 and 6, and the potential at both ends of the resistor 6 is compared by the comparator 7. In the comparison by the comparator 7, when the potential difference between both ends of the resistor 6 is equal to or larger than the set value in the comparator 7, a signal indicating that the voltage drop of the voltage under measurement 1 is equal to or less than a predetermined value is set as the voltage measurement result signal a to be measured. 7 and a resistor 6
Is smaller than the value set in the comparator 7, a signal indicating that the voltage drop of the voltage under measurement 1 exceeds a predetermined value is output from the comparator 7 as a voltage measurement result signal a to be measured. Here, the resistance values of the resistors 4 to 6 and the set value in the comparator 7 are set in advance to values that can detect a desired amount of decrease in the voltage to be measured. By using a resistor having a different resistance value, the potential difference between both ends of the resistor 6 changes, and the judgment level of the voltage drop of the measured voltage 1 can be changed without changing the set value in the comparator 7.

Further, in this embodiment, since the current based on the voltage under measurement 1 flows only while the switch 2 or the switch 3 is conducting, the power of the voltage under measurement 1 is not consumed except during the voltage detection. Absent.

FIG. 2 is a diagram showing another embodiment of the voltage drop detecting circuit according to the present invention, in which the switch shown in FIG. 1 is replaced with a photocoupler. In this embodiment,
When the photocoupler control signals b and c are input in a time-division manner, the photocouplers 8 and 9 operate in a time-division manner, so that the photocouplers 8 and 9 operate in the same manner as the circuit shown in FIG. A voltage drop of the measurement voltage 1 is detected. In the circuits shown in FIGS. 1 and 2, if three or more switches or photocouplers are used, it is possible to detect a decrease in the voltage to be measured with respect to three or more types of determination levels.

[0015]

As described above, in the present invention,
A plurality of first resistors having different resistance values from each other and being connected in parallel to the voltage to be measured are provided, and current supply to each first resistor by the voltage to be measured is performed in a time-sharing manner. Since the switching means for switching is provided, even if the voltage to be measured and the set value in the comparing means are the same, if the current supply to each first resistor by the voltage to be measured is switched in a time sharing manner by the switching means, the second The potential difference between both ends of the resistor is different, and the judgment level of the voltage drop with respect to the measured voltage can be switched. Thus, the voltage drop of the voltage to be measured with respect to a plurality of determination levels can be detected by one comparing means, and a low price can be realized. Further, since the current based on the measured voltage flows only when the voltage drop is detected, it is possible to prevent wasteful power consumption of the measured voltage.

[Brief description of the drawings]

FIG. 1 is a diagram showing one embodiment of a voltage drop detection circuit of the present invention.

FIG. 2 is a diagram showing another embodiment of the voltage drop detection circuit of the present invention.

FIG. 3 is a circuit diagram illustrating a configuration example of a conventional voltage drop detection circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Measured voltage 2, 3 Switch 4-6 Resistance 7 Comparator 8, 9 Photocoupler a Measured voltage measurement result signal b, c Photocoupler control signal

Claims (3)

[Claims] A first resistor that is connected in series with the voltage to be measured and divides the voltage to be measured; and a potential at both ends of the second resistor is compared. A voltage drop detecting circuit having a comparing unit configured to detect a voltage drop of the voltage to be measured by comparing the set value with a set value; wherein the first resistors have different resistance values from each other, and Voltage drop detection, comprising: a plurality of switching means provided to be connected in parallel to the measured voltage, and switching a current supply to the first resistor by the measured voltage in a time sharing manner. circuit. 2. The voltage drop detection circuit according to claim 1, wherein said switching means is a switch connected in series to each of said plurality of first resistors. 3. The voltage drop detection circuit according to claim 1, wherein the switching means is a photocoupler connected in series to each of the plurality of first resistors. .