JP3068598B1 - Amplifier failure detection circuit and its failure detection method - Google Patents

Abstract

Abstract: PROBLEM TO BE SOLVED: To surely detect a failure of an amplifier. SOLUTION: A phase converter 5 converts the phase of a pilot signal into a predetermined value to be a reference pilot signal, a level converter 11 converts a level of the pilot signal amplified by an amplifier 6, and a combiner 12 After synthesizing the reference pilot signal and the pilot signal from the level converter 11, the level detector 13 detects a failure of the amplifier 6 based on the level of the synthesized pilot signal output from the synthesizer 12. .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an amplifier fault detecting circuit suitable for detecting a fault in an amplifier and a fault detecting method thereof.

[0002]

2. Description of the Related Art An example of a conventional amplifier failure detection circuit is shown in FIG.

The amplifier failure detection circuit includes a synthesizer 2, a pilot signal generation circuit 3, an amplifier 6, a distributor 7, filters 8, 9, a level detection circuit 13, and an alarm detection circuit 14.
It has.

[0004] An input signal supplied from an input terminal 1 and a pilot signal output from a pilot signal generating circuit 3 are combined by a combiner 2. The signal synthesized by the synthesizer 2 is amplified by the amplifier 6 and then split by the splitter 7.

On the other hand, only the input signal is passed by the filter 8 and output from the output terminal 10. On the other side, only the pilot signal is passed by the filter 9 and input to the level detection circuit 13.

[0006] The level detection circuit 13 monitors the level of the input pilot signal to monitor the abnormality of the amplifier 6. If there is an abnormality, the alarm detection circuit 14 performs an alarm operation.

[0007]

By the way, in the above-described conventional amplifier failure detecting circuit, for example, the pilot signal generating circuit 3 is provided even though the amplifier 6 is operating normally.
There is a case where the level of the pilot signal is lowered for some reason.

In such a case, although the amplifier 6 is operating normally, the level detection circuit 13 erroneously detects that the amplifier 6 is faulty.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide an amplifier failure detection circuit and a failure detection method capable of reliably detecting an amplifier failure. It is.

[0010]

An amplifier failure detection circuit according to the present invention is an amplifier failure detection circuit for detecting a failure of an amplifier by detecting a level of a pilot signal output from a pilot signal generation circuit. Oh , pie
A phase converter that inverts the phase of the lot signal by 180 ° to use as a reference pilot signal, a level converter that converts the level of the pilot signal amplified by the amplifier, and a reference pilot signal and a pilot signal from the level converter. A synthesizer that performs synthesis, and a synthesis pyro output from the synthesizer
A detection circuit for detecting the cut signal, and a detected DC voltage.
And an OP amplifier that compares the reference voltage
And, characterized in that it comprises a level detection circuit for detecting a level fault of the amplifier by the output composite pilot signals from the combiner. The detection circuit may include a detection diode, and a detection resistor and a detection capacitor connected in parallel to the detection diode. A reference voltage and a first hysteresis resistor are connected to one end of the OP amplifier. A second hysteresis resistor is connected between the output terminal of the OP amplifier and the reference voltage and the first hysteresis resistor. A resistor can be connected. In the amplifier failure detection method according to the fourth aspect, by detecting the level of a pilot signal output from a pilot signal generation circuit,
An amplifier failure detecting method for detecting a failure of an amplifier, comprising: a first step of inverting a phase of a pilot signal by 180 ° to be a reference pilot signal; and a second step of converting a level of the pilot signal amplified by the amplifier. Process and
A third step of combining the reference pilot signal and the pilot signal whose level has been converted, a step of detecting the combined pilot signal, and a step of comparing the detected DC voltage with the reference voltage , Which detects the failure of the amplifier based on the level of the synthesized pilot signal.
And a step of: In the amplifier failure detection circuit and the failure detection method according to the present invention, the phase converter converts the phase of the pilot signal to a predetermined value to be a reference pilot signal, and the level converter converts the pilot signal amplified by the amplifier. Transform levels,
After synthesizing the reference pilot signal and the pilot signal from the level converter by the synthesizer, the failure of the amplifier is detected by the level detection circuit based on the level of the synthesized pilot signal output from the synthesizer.

[0011]

Embodiments of the present invention will be described below. Note that, in the drawings described below, parts common to FIG. 9 are denoted by the same reference numerals.

(First Embodiment) FIG. 1 is a block diagram showing a first embodiment of an amplifier failure detection circuit according to the present invention, and FIG. 2 is a circuit diagram showing details of the level detection circuit of FIG. FIG. 3 is a circuit diagram showing details of the alarm detection circuit of FIG. 1, and FIGS. 4 to 6 are diagrams for explaining the operation of the amplifier failure detection circuit of FIG.

The amplifier failure detection circuit shown in FIG. 1 includes synthesizers 2 and 12, a pilot signal generation circuit 3, distributors 4 and 7,
Phase converter 5, amplifier 6, filters 8, 9, level converter 11, level detection circuit 13, and alarm detection circuit 14
It has.

The combiner 2 combines the input signal from the input terminal 1 and the pilot signal from the distributor 4. Pilot signal generation circuit 3 generates a pilot signal. As the frequency of this pilot signal, a frequency distant from the input signal is selected.

The distributor 4 distributes the pilot signal from the pilot signal generation circuit 3. In this case, the pilot signal to the phase converter 5 becomes a reference pilot signal.

The phase converter 5 sets the absolute delay time of a predetermined circuit to the same delay time by using a coaxial cable or the like. Further, by performing fine adjustment using a commercially available phase adjuster, the phase of the input reference pilot signal is converted so as to be inverted by 180 ° with respect to the pilot signal from the level converter 11.

The amplifier 6 amplifies the combined signal from the combiner 2 to a predetermined value and outputs it to the distributor 7. The distributor 7 outputs the amplified combined signal to the filter 8 on one side and to the filter 9 on the other side.

The filter 8 allows only the input signal of the synthesized signal to pass. The input signal that has passed is output from an output terminal 10 to an external circuit.

The filter 9 allows only the pilot signal of the synthesized signal to pass therethrough and outputs the signal to the level converter 11. Level converter 11 converts the level of the pilot signal so that it becomes the same level as the reference pilot signal output from phase converter 5, and outputs it to combiner 12.

The combiner 12 combines the reference pilot signal output from the phase converter 5 and the pilot signal output from the level converter 11, and outputs the combined pilot signal to the level detection circuit 13. Level detection circuit 1
3 detects the level of the combined pilot signal.

The alarm detection circuit 14 performs an alarm operation when the combined pilot signal detected by the level detection circuit 13 is abnormal.

FIG. 2 shows the details of the level detection circuit 13.

The level detection circuit 13 includes a detection diode 1
5, a detection resistor 16, a detection capacitor 17, an OP amplifier 18, and a reference voltage Vref19.

When the combined pilot signal is received, the detection diode 15, the detection resistor 16 and the detection capacitor 17
Is detected by a detection circuit composed of

The OP amplifier 18 compares the DC voltage detected by the diode detection with the reference voltage Vref 19,
If it is high, "L" is detected, and if it is low, an "H" level detection signal is output.

The level detection signal is output to the alarm detection circuit 14 shown in FIG.

That is, the alarm detection circuit 14 includes a light emitting diode 20 and a resistor 21.

The light emitting diode 20 is turned on or off according to the level detection signal, and performs an alarm operation. That is, when the level detection signal is “L”, the light is turned on, and when the level detection signal is “H”, the light is turned off. The resistor 21 is a protection resistor for the light emitting diode 20.

Next, the operation of the amplifier fault detecting circuit having such a configuration will be described with reference to FIGS.

First, the pilot signal output from the pilot signal generation circuit 3 of FIG. One of the divided signals is combined with the input signal by the combiner 2 and then input to the amplifier 6. The other of the divided signals is input to phase converter 5 as a reference pilot signal.

One of the synthesized signals amplified by the amplifier 6 is output to the filter 8 by the distributor 7 and the other is output to the filter 9. The filter 8 allows only the input signal of the synthesized signal to pass. The input signal that has passed is output from an output terminal 10 to an external circuit.

The filter 9 allows only the pilot signal of the synthesized signal to pass therethrough and outputs the signal to the level converter 11. Level converter 11 converts the level of the pilot signal so as to be the same level as the reference pilot signal output from phase converter 5. The converted pilot signal is input to combiner 12.

On the other hand, the reference pilot signal input to phase converter 5 is inverted by 180 ° in phase with respect to the pilot signal output from level converter 11. The adjustment of the 180 ° inversion in the phase converter 5 does not change over time if it is first performed once.

The phase-converted reference pilot signal is input to the combiner 12, where it is combined with the pilot signal. The synthesized pilot signal is output to the level detection circuit 13 and its level is detected.

Here, for example, the level of the reference pilot signal output from phase converter 5 is +4 dBm,
Assume that the characteristic impedance of the circuit is 50Ω. When converted to a high frequency voltage, it is 2VP-P (0.35VRMS).

Here, when the pilot signal generation circuit 3 and the amplifier 6 are operating normally, the pilot signal output from the level converter 11 is converted into a voltage of 2VP-P
Becomes Therefore, the pilot signal and the reference pilot signal have a relationship as shown in FIG. Then, the combined pilot signal combined by the combiner 12 becomes 0VP-P.

The level detection circuit 13 compares the reference voltage Vref19 with a DC voltage obtained by diode detection of the combined pilot signal. Here, for example, when this DC voltage is 0 V, the reference voltage Vref1
Since the voltage is lower than 9, “H” is output. It is assumed that the value of the reference voltage Vref19 is set to 0.5V. Therefore, the alarm detection circuit 14 that has received the “H” synthesized pilot signal does not turn on the light emitting diode 20.

Next, it is assumed that pilot signal generating circuit 3 is operating normally and amplifier 6 has failed. In this case, the pilot signal output from level converter 11 is, for example, -2 dBm, that is, 1VP-P (0.178).
VRMS).

At this time, the pilot signal and the reference pilot signal have a relationship as shown in FIG. For this reason, the combined pilot signal combined by the combiner 12 becomes 1VP-P. In the level detection circuit 13, the reference voltage Vre
f19 is compared with a DC voltage obtained by diode detection of the combined pilot signal.

When the DC voltage is 1 V, for example, "L" is output because the voltage is higher than the reference voltage Vref19. Reference voltage Vre
It is assumed that the value of f19 is set to 0.5 V as described above. The alarm detection circuit 14 that has received the “L” level detection signal turns on the light emitting diode 20.

It is also assumed that the level of the pilot signal from pilot generation circuit 3 is lowered for some reason, although amplifier 6 is operating normally. In this case, it is assumed that, for example, the reference pilot signal output from phase converter 5 has been reduced to -2 dBm, that is, 1VP-P.

At this time, the pilot signal output from the level converter 11 also drops to 1VP-P. This is because the pilot signal input to the amplifier 6 has already dropped. Since the amplification of the amplifier 6 is constant and the gain of the entire circuit is constant, the level converter 1
This is because the pilot signal output from 1 also has the same decrease as the reference pilot signal.

Therefore, the relationship between the pilot signal and the reference pilot signal is as shown in FIG. The combined pilot signal combined by the combiner 12 is 0VP-P. The level detection circuit 13 compares the reference voltage Vref19 with a DC voltage obtained by diode detection of the combined pilot signal.

Here, if the DC voltage is 0 V, for example, "H" is output because the voltage is lower than the reference voltage Vref19. Reference voltage Vre
It is assumed that the value of f19 is set to 0.5 V as described above. The alarm detection circuit 14 that has received the “H” level detection signal does not turn on the light emitting diode 20.

As described above, in the first embodiment, when the amplifier 6 is operating normally, the level detection circuit 13 is set to “H” regardless of whether the pilot signal generation circuit 3 is normal or abnormal.
Is output. When the amplifier 6 fails, the level detection circuit 1 is activated regardless of whether the pilot signal generation circuit 3 is normal or abnormal.
3 outputs "L". Therefore, it is not possible to erroneously detect a failure of the amplifier 6 due to an abnormality of the pilot signal generation circuit 3.

(Second Embodiment) FIG. 7 is a circuit diagram showing a second embodiment of the amplifier failure detection circuit of the present invention, and FIG. 8 shows input / output voltage characteristics of the OP amplifier of FIG. FIG.

The level detection circuit 13 shown in FIG.
Hysteresis resistor 22 as hysteresis resistor of
And a hysteresis resistor 23 as a first hysteresis resistor.

That is, the reference terminal Vref 19 and the hysteresis resistor 23
Are connected in series. An output terminal of the OP amplifier 18;
Reference voltage Vref19 and hysteresis resistor 2
3, a hysteresis resistor 22 is connected.

By adding the hysteresis resistor 22 and the hysteresis resistor 23, a stable level detection signal can be output even if the combined pilot signal fluctuates for some reason. The technology for this hysteresis is described in "Point study, new edition, analog IC basics, Yoshio Shirato, Tokyo Denki University Press".

Next, a case where the level of the pilot signal is reduced due to the abnormal operation of the pilot signal generation circuit 3 in spite of the normal operation of the amplifier 6 will be described.

When the level of the pilot signal of pilot signal generating circuit 3 decreases, the combined pilot signal becomes 0VP-
It becomes P. In this case, similarly to the above, the reference voltage Vref19 is set to 0.5 V, and the reference voltage Vr19 is set.
ef19 is compared with a DC voltage obtained by diode detection of the combined pilot signal.

Here, for example, when the DC voltage is 0 V, "H" is output because the voltage is lower than the reference voltage Vref19. At this time, a voltage Vr is generated in the hysteresis resistor 23, and Vref + Vr
Is applied to the + terminal of the OP amplifier 18. O at this time
The input / output voltage characteristics of the P amplifier 18 are as shown in FIG.

Therefore, the output of the OP amplifier 18 is not inverted unless the combined pilot signal becomes higher than this voltage.
That is, even if the synthesized pilot signal fluctuates for some reason, a stable level detection signal is output.

Next, a case where the amplifier 6 has failed while the pilot generation circuit 3 is operating normally will be described. In this case, the combined pilot signal is 1VP-P. The reference voltage Vref19 is compared with a DC voltage obtained by diode detection of the combined pilot signal. Here, for example, when the DC voltage is 1 V, "L" is output because the voltage is higher than the reference voltage Vref19.

At this time, Vr is applied to the hysteresis resistor 23.
Does not occur, and the reference voltage Vref19
Is applied to the + terminal of the OP amplifier 18. Therefore, the output is not inverted unless the combined pilot signal falls below this voltage. That is, even if the synthesized pilot signal fluctuates for some reason, a stable level detection signal is output.

As described above, in the second embodiment, the OP
A reference voltage Vref19 and a hysteresis resistor 23 are connected in series to the positive terminal of the
8, the hysteresis resistor 22 is connected between the reference voltage Vref19 and the hysteresis resistor 23, so that a stable level detection signal is output even if the synthesized pilot signal fluctuates for some reason. be able to.

[0057]

As described above, according to the amplifier failure detection circuit and the failure detection method according to the present invention, the phase of the pilot signal is converted into a predetermined value by the phase converter, and the reference pilot signal is obtained. After the level of the pilot signal amplified by the amplifier is converted and the reference pilot signal and the pilot signal from the level converter are synthesized by the synthesizer, the synthesized pilot output from the synthesizer is output by the level detection circuit. Since the failure of the amplifier is detected based on the signal level, the failure of the amplifier can be reliably detected.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of an amplifier failure detection circuit according to the present invention.

FIG. 2 is a circuit diagram showing details of a level detection circuit of FIG. 1;

FIG. 3 is a circuit diagram showing details of an alarm detection circuit of FIG. 1;

FIG. 4 is a diagram for explaining an operation of the amplifier failure detection circuit of FIG. 1;

FIG. 5 is a diagram for explaining an operation of the amplifier failure detection circuit of FIG. 1;

FIG. 6 is a diagram for explaining an operation of the amplifier failure detection circuit of FIG. 1;

FIG. 7 is a circuit diagram showing a second embodiment of the amplifier failure detection circuit according to the present invention.

FIG. 8 is a diagram showing input / output voltage characteristics of the OP amplifier in FIG. 7;

FIG. 9 is a block diagram showing an example of a conventional amplifier failure detection circuit.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 input terminal 2, 12 synthesizer 3 pilot signal generation circuit 4, 7 distributor 5 phase converter 6 amplifier 8, 9 filter 10 output terminal 11 level converter 13 level detection circuit 14 alarm detection circuit 15 detection diode 16 detection resistance 17 Detection Capacitor 18 OP Amplifier 19 Reference Voltage 20 Light Emitting Diode 21 Protective Resistance 22, 23 Hysteresis Resistance

Claims (4)

(57) [Claims] An amplifier failure detection circuit for detecting a failure of an amplifier by detecting a level of a pilot signal output from a pilot signal generation circuit, wherein the reference pilot signal is inverted by 180 ° a phase converter for the signal, a level converter for converting the level of the amplified pilot signal by the amplifier, and a combiner for synthesizing the pilot signal from the reference pilot signal and the level converter, the combined Of the synthesized pilot signal output from the
A detection circuit for performing a wave, and the detected DC voltage and a reference
And a level detection circuit for detecting a failure of the amplifier based on a level of a combined pilot signal output from the combiner. Wherein said detection circuit, detection diode and, claims, characterized in that it comprises a resistor and a detection capacitor for detection connected in parallel to the detection diode
Item 2. An amplifier failure detection circuit according to Item 1 . 3. The one end of the OP amplifier is connected to the reference voltage and a first hysteresis resistor. The output terminal of the OP amplifier is connected between the reference voltage and the first hysteresis resistor. 2. The amplifier failure detection circuit according to claim 1 , wherein a second hysteresis resistor is connected. 4. A method for detecting a failure of an amplifier by detecting a level of a pilot signal output from a pilot signal generation circuit, wherein the phase of the pilot signal is inverted by 180 ° to be a reference signal. A first step as a pilot signal, a second step of converting the level of the pilot signal amplified by the amplifier, and a third step of combining the reference pilot signal and the level-converted pilot signal. A step of detecting the synthesized pilot signal, and a step of comparing the detected DC voltage with a reference voltage, and detecting a failure of the amplifier based on a level of the synthesized synthesized pilot signal. And a fourth step of detecting a failure of the amplifier.