JP2001035335A - Relay failure detecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive relay failure detecting device even when the difference in input voltage levels of two input signals is small. SOLUTION: A differential amplifying circuit 12 amplifies the difference between an input signal S1 and an output signal SOUT. An A/D converter 13 detects its difference (VIN), and a CPU 14 compares the detected value (VIN) with threshold (VLL, VLH) determined beforehand according to the switching state of a relay to determine if the relay has a failure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a relay inspection apparatus, and more particularly, to a relay inspection apparatus that functions as a changeover switch for switching and outputting two input signals according to a control signal.

[0002]

2. Description of the Related Art In a conventional relay fault detecting apparatus for detecting a fault in a relay which switches between two input signals in which the voltage level of one input signal is higher than the level of the other input signal, two input signals and The failure of the relay is determined by comparing the three voltage levels of the output signal after the relay switching.

[0003]

However, in this method, when the difference voltage between two input signals input to the relay is small, three signals (two input signals) are required to detect the failure of the relay. In order to detect the voltage level of the output signal of the relay), it is necessary to use expensive elements and components such as an A / D converter and a multiplexer with high accuracy, and as a result, the inspection circuit becomes expensive. Had become.

SUMMARY OF THE INVENTION Accordingly, the present invention has been made in view of the above problems, and has as its object to provide an apparatus capable of detecting a relay failure at low cost even when the difference between the voltage levels of two input signals is small. Is to do.

[0005]

According to the present invention, there is provided a relay fault detecting apparatus for detecting a difference between an output voltage level of a relay and one of two input signals. Means for comparing the difference value with a predetermined value, wherein a failure of the relay is determined according to a selection state of the input signal based on the comparison result.

[0006]

Embodiments of the present invention will be described. The present invention, in a preferred embodiment thereof, amplifies a differential voltage between an input signal S1 and an output signal SOUT in a differential amplifier circuit (12) having a differential input between an input signal S1 to the relay and an output signal SOUT of the relay. Then, the difference value (VIN) is converted into a digital code by the A / D converter (13), and the CPU (14) determines in advance the detected value (VIN) and the switching state (transition state) of the relay in advance. By comparing the determined threshold value (VLL, VLH), it is determined whether the relay is faulty or normal.

[0007]

Embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing the configuration of one embodiment of the present invention. Referring to FIG. 1, one embodiment of the present invention includes a relay 11 to be inspected, a differential amplifier 12, an A / D converter 13, a CPU 14, a memory 15, and a ROM (read only memory) 16. And

[0008] The relay 11 is connected to the first input signal S1 and the second input signal S1.
, And switches these input signals in accordance with the control signal SEL from the CPU 14, and outputs the selected input signal to the output terminal SOUT. At this time, the voltage level of the second input signal S2 is always higher than the voltage level of the first input signal S1. FIG.
FIG. 3 is a diagram illustrating a voltage range of a first input signal S1 and a second input signal S2 according to an embodiment of the present invention. That is, the second
Are set higher than the voltage range of the first input signal S1, and the voltage ranges do not overlap with each other.

The differential amplifier circuit 12 has a first input signal S1
Alternatively, the difference between the voltage of the second input signal S2 and the voltage of the output signal SOUT is amplified and output. FIG. 1 shows an example in which the first input signal S1 is input to the non-inverting input terminal (+) of the differential amplifier circuit 12.

In the ROM 16, the CPU 14 stores the relay 11
Is stored.

The CPU 14 is provided with a switching control signal SEL.
To control the switching of the relay 11,
According to the program stored in the ROM 16, the voltage amplified by the differential amplifier 12 is input as an input signal voltage VIN converted into a digital signal via the A / D converter 13, and the input signal voltage VIN and the memory 15 are input. Is compared with the threshold values VLL and VLH stored in advance in order to determine whether or not the relay has failed. Differential amplifier 12
Is set to output a predetermined value (offset value) V0 (for example, 2.5 V) when the voltage difference between the first input signal S1 and the output signal SOUT is zero. When the voltage difference between the first input signal S1 and the output signal SOUT is zero, the predetermined value V0 is equivalent to the offset (V0) in the A / D converter 13 when the differential amplifier 12 outputs 0V. May be output.

FIG. 3 is a diagram showing the voltage level V0 of the voltage value VIN output from the differential amplifier 12 when the threshold values VLL and VLH and the voltage difference between the first input signal S1 and the output signal SOUT are zero. is there.

As shown in FIG. 3, the threshold value VLL is set to a value smaller than V0 by ΔV (for example, 0.3 V).
The threshold value VLH is set to a value larger than V0 by ΔV.

FIG. 4 is a flow chart for explaining the operation of the relay failure detecting device shown in FIG. With reference to FIG. 1 and FIG. 4, an operation of the CPU 14 for determining a failure of a relay will be described.

First, in step 101, the CPU 14 determines whether to perform the processing in step 102 or the processing in step 106 according to the current value of the relay switching signal (selection signal) SEL.

If the relay switching signal SEL has selected the first input signal S1, the process proceeds to step 102, while if the second input signal S2 has been selected, the process proceeds to step 102.
Move to step 106.

In step 102, the second input signal S2
It is determined whether to perform the processing of step 103 or the processing of step 105 in accordance with the state transition from the first input signal S1 to the second input signal S1.
If the state has transitioned from 2 to the first input signal S1, the process proceeds to step 105;
03 is performed.

In step 105, the CPU 14 executes A /
The voltage VIN (n−n) before switching input from the D converter 13
1) is compared with the threshold value VLH, and VIN (n−1) <V
If it is LH, the process proceeds to step 103, where VIN
If (n−1) ≧ VLH, it is determined that the relay has failed.

In step 103, the switched VIN (n) input from the A / D converter 13 is compared with the threshold value VLH. If VIN (n) ≦ VLH, the process proceeds to step 104, where VIN (n) If)> VLH, it is determined that the relay has failed.

In step 104, VIN (n) is compared with a threshold value VLL. If VIN (n) ≧ VLL, the relay is determined to be normal, and if VIN (n) <VLL, the relay is determined to be faulty.

In step 106, the first input signal S1
It is determined whether to perform the processing of step 107 or the processing of step 108 in accordance with the state transition from the first input signal S1 to the second input signal S2.
If the state has transitioned to the second input signal S2, the process proceeds to step 107; otherwise, the process proceeds to step 1
08 is performed.

In step 107, VIN (n
-1) is compared with the threshold value VLL, and VIN (n-1)> VL
If L, go to step 108, VIN (n-1) ≤
If it is VLL, it is determined that the relay has failed.

In step 108, VIN (n) input from the A / D converter 13 is compared with a threshold value VLL, and VI
If N (n) ≦ VLL, the relay is normal, VIN (n)
If> VLL, it is determined that a relay has failed.

[0024]

As described above, according to the present invention,
Depending on the control state of the relay, a difference value between one input signal and the output signal of the relay is compared with a predetermined threshold to detect a failure of the relay, so that a plurality of A / D converters can be used. Alternatively, a relay failure can be reliably detected with a simple and inexpensive circuit configuration without using a multiplexer.

[Brief description of the drawings]

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

FIG. 2 shows input signals S1 and S in one embodiment of the present invention.
FIG. 6 is a diagram illustrating an example of a voltage range of FIG.

FIG. 3 shows threshold values VLL and VL in one embodiment of the present invention.
FIG. 7 is a diagram illustrating a voltage level V0 of VIN when a voltage difference between H, a first input signal S1, and an output signal SOUT is zero.

FIG. 4 is a flowchart for explaining the operation of one embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 11 relay 12 differential amplifier 13 A / D converter 14 CPU 15 memory 16 ROM

Claims (4)

[Claims] 1. A means for detecting a difference voltage between a voltage level of one input signal of two input signals supplied to a relay to be inspected and an output voltage level of the relay; Means for comparing with a predetermined threshold value in accordance with the selection state of the input signal of the relay, wherein a failure of the relay is determined based on the comparison result. 2. A relay inspection apparatus for switching one of a first input signal and a second input signal respectively input to a first input terminal and a second input signal by a selection signal and outputting the selected signal to an output terminal. One of the first and second input signals is set to a higher voltage range than the other, and a difference voltage between one input signal voltage of the first or second input signal and an output voltage of the relay is obtained. Means for differentially amplifying, and determining a failure of the relay by comparing the differential voltage with a predetermined threshold value according to a state of selection of the first and second input signals in the relay. Means, comprising: a relay failure detection device. 3. A failure detection device for detecting a failure of a relay that switches between two input signals in which the voltage level of one input signal is always set higher than the voltage level of the other input signal, wherein the output of the relay is Means for detecting a difference between the voltage level and the voltage level of one of the two input signals; means for comparing the detected difference value with a predetermined value; Means for determining a relay failure in accordance with the selected state of the input signal based on the comparison result. 4. A first and a second input signal input to a first and a second input terminal, respectively, wherein the voltage level of the first input signal is equal to the voltage of the second input signal. The first and second input signals, which are set higher than the level,
In a fault detection device for a relay switch which switches according to an input selection signal and outputs the output signal to an output terminal, a differential amplifying means for differentially amplifying the first or second input signal and an output voltage level of the output terminal is provided. Wherein the differential amplifier outputs a predetermined voltage level when a difference between a voltage level of the selected first input signal or the second input signal and the output voltage level is zero, Means for storing a threshold value defining an upper limit and a lower limit of a range sandwiching a predetermined voltage level; and before switching the relay switch according to a transition state of switching the first and second input signals in the relay switch. Or, after switching, a value obtained by converting the output of the differential amplifying means into a digital signal is compared with the threshold value, and based on the comparison result, a relay is performed in accordance with a selection state of the input signal. Means for judging the failure of the relay.