JP7436324B2 - Radiation-resistant circuit and self-diagnosis method for radiation-resistant circuit - Google Patents

Description

The present invention relates to a radiation-resistant circuit and a self-diagnosis method for a radiation-resistant circuit.

2. Description of the Related Art Nuclear power plants, for example, are examples of systems in which it is necessary to maintain circuit devices in a radiation environment.
In a nuclear power plant, many measuring devices (measuring devices, measuring instruments) are installed to monitor the inside of the plant or facility. The semiconductor circuits that make up these measurement devices may be degraded by radiation.
To deal with the possibility that this semiconductor circuit will deteriorate due to radiation, we have changed from Si semiconductors that use conventional Si (silicon) in the semiconductor circuit section to high bandgap materials such as SiC (silicon carbide). The use of semiconductors greatly improves the radiation resistance of semiconductor circuits.
However, even with this measure, when the cumulative dose of radiation is on the order of kGy to MGy, there is a possibility that the semiconductor circuit will be deteriorated by the radiation.
Therefore, a means to confirm the soundness of the semiconductor circuit is required.

For example, Patent Document 1 is related to such technology.
The [Summary] of Patent Document 1 states, ``[Objective] The present invention is capable of identifying the location where a transmission abnormality occurs through self-diagnosis, and aims to improve reliability and maintainability as well as system operation rate. [Configuration] This is a transmission device that outputs transmission data from the transmission controller 12 of the data terminal device 10A to another data terminal device 10B, and inputs data sent from the other device from the reception terminal of the transmission controller 12. A diagnostic means 11 that performs an abnormality diagnosis based on the data sent to another data terminal device 10B and returned data, and a test means 11 that is provided in front of the receiving terminal of the transmission controller 12, and the data sent from the other data terminal device 10B are used as test data. If the data detecting means 13 determines that the data is test data, the data detected by the data detecting means 13, which is provided before the transmission terminal of the transmission controller 12, detects the data sent from another data terminal device 10B. and a return means 14 for returning the data to the data terminal device 10B.'', which discloses a technology for a transmission device with a self-diagnosis function.

Japanese Patent Application Publication No. 7-253995

In the above-mentioned Patent Document 1, a means is provided for transmitting test data to a circuit to be diagnosed and performing an abnormality diagnosis based on the returned data.
However, in situations where there is a diagnostic target in a radiation environment, there is a problem (problem) that providing an additional diagnostic section (diagnostic circuit) to the device to be diagnosed may increase the risk of failure due to radiation. .

The present invention was devised in view of the above-mentioned problems, and provides a radiation-resistant circuit that has excellent environmental performance such as radiation resistance and diagnoses deterioration due to radiation, and a self-diagnosis method for the radiation-resistant circuit. That is the task (purpose).

In order to solve the above problems, the present invention was configured as follows.
That is, the radiation-resistant circuit of the present invention is installed in a radiation area, and includes an analog switch circuit configured with a parallel circuit of pMOS and nMOS, and generates a pilot signal, which is a known signal, and connects the first terminal of the analog switch circuit. and the pilot signal installed in a non-radiation area, which passes through the analog switch circuit and is output from the second terminal of the analog switch circuit, performs signal processing related to radiation deterioration. and a signal processing unit installed in a non-radiation area, and based on the output of the signal processing unit, diagnose the state of deterioration of the analog switch circuit due to radiation and the state of deterioration of the self-device including the analog switch circuit. and a self-diagnosis unit for determining the characteristics of the pMOS and the nMOS caused by the occurrence of deterioration of the pMOS in the pMOS, which deteriorates earlier than the nMOS due to the radiation irradiation. The method is characterized in that signal distortion caused in the pilot signal passing through the analog switch circuit by the difference is processed and outputted .

Further, other means will be explained in the detailed description.

According to the present invention, it is possible to provide a radiation-resistant circuit that has excellent environmental resistance performance such as radiation resistance and that diagnoses deterioration due to radiation, and a self-diagnosis method for the radiation-resistant circuit.

1 is a diagram showing a configuration example of a radiation-resistant circuit according to a first embodiment of the present invention. FIG. It is a figure showing the example of composition of the radiation resistant circuit concerning a 2nd embodiment of the present invention. It is a figure showing the example of composition of the radiation resistant circuit concerning a 3rd embodiment of the present invention. It is a figure showing the example of composition of the radiation resistant circuit concerning a 4th embodiment of the present invention. It is a figure which shows the circuit structure of the pilot signal generation part in the 1st modification of 4th Embodiment of this invention. It is a figure which shows the circuit structure of the pilot signal generation part in the 2nd modification of 4th Embodiment of this invention. FIG. 7 is a diagram illustrating an example in which a pilot signal generation section in a radiation-resistant circuit according to a fifth embodiment of the present invention is configured with a bandgap reference circuit. FIG. 12 is a diagram showing an example of a multiplexer circuit using a plurality of analog switch circuits in a radiation-resistant circuit according to a sixth embodiment of the present invention. FIG. 7 is a diagram showing a truth table of output signals for control signals of a decoder circuit in a multiplexer circuit in a radiation-resistant circuit according to a sixth embodiment of the present invention. FIG. 7 is a diagram showing a logical expression table for configuring a logic circuit that selects one of the analog switch circuits in response to a control signal of a decoder circuit in a multiplexer circuit in a radiation-resistant circuit according to a sixth embodiment of the present invention. . FIG. 12 is a diagram showing another configuration example of a multiplexer circuit in a radiation-resistant circuit according to a modification of the sixth embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, modes for carrying out the present invention (hereinafter referred to as "embodiments") will be described with reference to the drawings as appropriate.
However, the present invention is not limited to the following embodiments and modified examples, but can be combined with a plurality of embodiments and modified examples, or can be arbitrarily modified without departing from the technical idea of the present invention.
In addition, in this specification, the same members are given the same reference numerals, and redundant explanations will be omitted. For convenience of illustration, the contents of the illustrations may be changed from the actual configuration without departing from the spirit of the present invention.

≪First embodiment≫
The configuration of the radiation-resistant circuit according to the first embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing a configuration example of a radiation-resistant circuit according to a first embodiment of the present invention. Note that the following explanation is mainly about the radiation-resistant circuit, but also serves as a description of a self-diagnosis method for the radiation-resistant circuit.
Furthermore, radiation will be explained using γ rays as an example.

In FIG. 1, the radiation-resistant circuit 11 includes an analog switch circuit 101, a pilot signal generation section 102, a signal processing section 103, and a self-diagnosis section 104.

The analog switch circuit 101 includes a pMOS 111, which is a p-type MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor), and an nMOS 112, which is an n-type MOSFET, connected in parallel. Note that the pMOS 111 and the nMOS 112 are configured using, for example, SiC (silicon carbide), which is a semiconductor with a wider (higher) band gap than Si.

A control signal 1 is input to the gate electrode 1001 of the pMOS 111.
A control signal 2 is input to the gate electrode 1002 of the nMOS 112.
The analog switch circuit 101 is made conductive (ON) or cut off (OFF) by the control signal 1 and the control signal 2. Note that when the analog switch circuit 101 is turned on (ON), the control signal 1 is set to a low potential (negative potential, L), the control signal 2 is set to a high potential (positive potential, H), and the pMOS 111 and nMOS 112 are connected together. Make it conductive (ON).
When the analog switch circuit 101 is cut off (OFF), the control signal 1 is set to a high potential (positive potential, H), the control signal 2 is set to a low potential (negative potential, L), and the pMOS 111 and nMOS 112 are connected together. Shut off (OFF).

The output signal (electrical signal) of the pilot signal generation section 102 is input to the first terminal 1003 of the analog switch circuit 101 . Note that the pilot signal of the pilot signal generation section 102 is a known signal (for example, a fixed DC voltage). A specific example of the configuration of the pilot signal generation section will be described later with reference to FIGS. 4A, 4B, 4C, 5, etc.

A second terminal 1004 of the analog switch circuit 101 is connected to an input section of the signal processing section 103 via a cable 1010. That is, the output signal (electrical signal) of the pilot signal generation section 102 is input to the signal processing section 103 via the analog switch circuit 101 and the cable 1010.
The signal output from the signal processing section 103 is input to the self-diagnosis section 104.

The analog switch circuit 101 and the pilot signal generation section 102 are installed in a radiation region where the dose of radiation is high. For example, it is installed inside a primary containment vessel (PCV) of a nuclear power plant.
The signal processing unit 103 and the self-diagnosis unit 104 are installed in a non-radiation area (or a low radiation area) where the radiation dose is low.
A boundary 2001 is a boundary between a radiation area and a non-radiation area, and corresponds to, for example, a wall of a containment vessel (PCV) of a nuclear power plant. This wall is provided with a penetration portion (penetration) for pulling out the cable 1010 to the outside of the containment vessel (PCV).

The pilot signal generation unit 102 and analog switch circuit 101 installed in a radiation area may be affected by radiation.
Therefore, as described above, the semiconductor elements of the pMOS 111 and nMOS 112 constituting the analog switch circuit 101 are made of, for example, SiC, which is not easily affected by radiation.
Pilot signal generation section 102 may be covered with a shield such as lead. Radiation shields such as lead reduce the amount of radiation irradiated.
Note that the circuit or signal source that generates the control signal 1 and the control signal 2 may be provided in a non-radiation area, or may be provided in the decoder circuit 120 (Fig. 6A), it may be provided in the radiation area.

<Influence of radiation on analog switch circuit 101>
In the configuration shown in FIG. 1, as described above, the analog switch circuit 101 is in an environment where it is irradiated with radiation, so the semiconductor elements of the pMOS 111 and nMOS 112 that make up the analog switch circuit 101 are subject to deterioration due to radiation. There is.
This radiation-induced deterioration is more pronounced as the bandgap of the semiconductor is lower. Therefore, pMOS and nMOS semiconductor devices using Si (silicon), which has a relatively low bandgap, are susceptible to deterioration due to radiation.
In order to reduce this radiation-induced deterioration, SiC (silicon carbide), which has a semiconductor band gap higher than that of Si, is used for the pMOS 111 and nMOS 112 in FIG.
However, even in the pMOS 111 and nMOS 112 that use SiC with a relatively high band gap, there is a possibility that deterioration due to radiation may occur.

In pMOS 111 and nMOS 112 using SiC, if radiation continues to be irradiated, pMOS (111) deteriorates before nMOS (112). Specifically, leakage current increases due to the ionization effect of radiation.
When the pMOS 111 deteriorates in this way, distortion (drift) occurs in the pilot signal that has passed through the analog switch circuit 101 due to the difference in characteristics between the nMOS 112 and the pMOS 111. By receiving this distortion at the signal processing section 103 and diagnosing it at the self-diagnosis section 104, the degree of deterioration of the analog switch circuit 101 can be evaluated.
Note that, as described above, the signal processing section 103 and the self-diagnosis section 104 are installed in a non-radiation area. Therefore, the signal processing section 103 and the self-diagnosis section 104 are not affected by radiation.

Since the analog switch circuit 101 is installed in a radiation area as described above, it is desirable that the influence of radiation be small. Therefore, the pMOS 111 and nMOS 112 that constitute the analog switch circuit 101 are constructed using SiC, which has excellent radiation resistance.
However, even if SiC is used for the pMOS 111 and the nMOS 112, a certain degree of deterioration as a semiconductor element progresses due to the influence of radiation. As described above, in SiC, pMOS deteriorates faster than nMOS due to radiation.
In this way, the electrical characteristics of the analog switch circuit 101 change when the pMOS 111 and nMOS 112 deteriorate due to radiation.

Pilot signal generation section 102 generates a signal of a predetermined potential and inputs it to first terminal 1003 of analog switch circuit 101 .
The analog switch circuit 101 transmits this input signal of a predetermined potential and outputs it to the second terminal 1004.
The predetermined signal output to the second terminal 1004 of the analog switch circuit 101 is input to the signal processing unit 103 via the cable 1010, as described above.

The signal processing section 103 performs signal processing on the input signal of the pilot signal generation section 102 through the analog switch circuit 101 having a pMOS 111 and an nMOS 112.
As described above, in the analog switch circuit 101, the pMOS 111 deteriorates faster than the nMOS 112 due to radiation. This radiation degradation has different effects on the current flowing through the pMOS 111 and the current flowing through the nMOS 112.
The signal processing unit 103 performs signal processing on the current flowing through these pMOS 111 and the current flowing through nMOS 112. That is, signal processing related to radiation deterioration of the analog switch circuit 101 is performed based on changes in the current flowing through the pMOS 111 and the current flowing through the nMOS 112.

The self-diagnosis section 104 performs a self-diagnosis regarding radiation deterioration of the radiation-resistant circuit 11 based on the signal from the signal processing section 103 .
Specifically, the self-diagnosis unit 104 analyzes the deterioration status of the analog switch circuit 101 and further the radiation deterioration of the radiation-resistant circuit 11 itself, based on the result of signal processing related to radiation deterioration by the signal processing unit 103. A self-diagnosis of the radiation-resistant circuit 11 is performed.

<Summary of the first embodiment>
The radiation-resistant circuit 11 includes an analog switch circuit 101, a pilot signal generation section 102, a signal processing section 103, and a self-diagnosis section 104.
The analog switch circuit 101 is installed in a radiation area where the dose of radiation is high, for example, inside a containment vessel (PCV) of a nuclear power plant. The signal processing unit 103 and the self-diagnosis unit 104 are installed in a non-radiation area (or a low radiation area) where the radiation dose is low.

The semiconductor elements of pMOS 111 and nMOS 112 that constitute analog switch circuit 101 are constructed based on SiC, which is not easily affected by radiation. However, even if SiC is used for the pMOS 111 and the nMOS 112, a certain degree of deterioration as a semiconductor element progresses due to the influence of radiation. The electrical characteristics of the analog switch circuit 101 change when the pMOS 111 and nMOS 112 deteriorate due to radiation. Note that pMOS deteriorates faster than nMOS due to radiation.
Therefore, the signal processing unit 103 performs signal processing related to radiation deterioration of the analog switch circuit 101 based on changes in the input signal. The self-diagnosis section 104 performs a self-diagnosis regarding radiation deterioration of the radiation-resistant circuit 11 based on the signal from the signal processing section 103 .

<Effects of the first embodiment>
According to the radiation-resistant circuit of the first embodiment of the present invention, in the analog switch circuit composed of SiC pMOS and nMOS, distortion occurs in the pilot signal passed through the analog switch circuit due to the difference in characteristics between the pMOS and nMOS. By receiving this distortion in the signal processing section and diagnosing it in the self-diagnosis section, it is possible to evaluate the degree of deterioration of the analog switch circuit.
That is, according to the first embodiment of the present invention, it is possible to provide a radiation-resistant circuit that has excellent environmental resistance such as radiation resistance and that diagnoses deterioration due to radiation, and a self-diagnosis method for the radiation-resistant circuit.

≪Second embodiment≫
The configuration of a radiation-resistant circuit according to a second embodiment of the present invention will be described with reference to the drawings.
FIG. 2 is a diagram showing a configuration example of a radiation-resistant circuit according to a second embodiment of the present invention. Note that the following explanation is mainly about the radiation-resistant circuit, but it also serves as an explanation of its self-diagnosis method.

In FIG. 2, the radiation-resistant circuit 12 includes an analog switch circuit 101, a pilot signal generation section 102, a signal processing section 103, a self-diagnosis section 104, and a database section (DB) 105.
The radiation-resistant circuit 12 shown in FIG. 2 is different from the radiation-resistant circuit 11 shown in FIG. 1 in the database section (DB) 105. Other constituent elements are the same, so redundant explanation will be omitted.

The database unit 105 stores in advance, as a database, data on the effect of signal distortion on the pilot signal of the pilot signal generating unit 102 after passing through the analog switch circuit 101 on the amount of radiation irradiation.
Therefore, rather than calculating and determining the signal from the signal processing section 103 each time, the self-diagnosis section 104 can refer to the database (data) stored in advance in the database section 105 to quickly and accurately detect the analog switch. Deterioration of the circuit 101 can be diagnosed.

<Effects of the second embodiment>
According to the second embodiment of the present invention, by referring to the database (data) stored in advance in the database unit 105, deterioration of the analog switch circuit 101 can be diagnosed in a short time and with high accuracy.

≪Third embodiment≫
The configuration of a radiation-resistant circuit according to a third embodiment of the present invention will be described with reference to the drawings.
FIG. 3 is a diagram showing a configuration example of a radiation-resistant circuit according to a third embodiment of the present invention. Note that the following explanation is mainly about the radiation-resistant circuit, but it also serves as an explanation of its self-diagnosis method.

In FIG. 3, the radiation-resistant circuit 13 includes an analog switch circuit 101, a pilot signal generation section 102, a signal processing section 103, a self-diagnosis section 104, an alarm command section 106, and an alarm display section 107.
The radiation resistant circuit 15 shown in FIG. 3 is different from the radiation resistant circuit 11 shown in FIG. Other constituent elements are the same, so redundant explanation will be omitted.

In FIG. 3, when the self-diagnosis unit 104 detects a failure of the analog switch circuit 101 or a deterioration of the electrical characteristics, a first alarm command is sent from the signal processing unit 103 to the alarm display unit 107 via the alarm command unit 106. will be sent to.
Alternatively, a second alarm command is sent from the self-diagnosis section 104 to the alarm display section 107.
The first alarm command sent from the signal processing unit 103 via the alarm command unit 106 is an alarm for a serious situation such as when the analog switch circuit 101 breaks down.
Further, the second alarm command sent from the self-diagnosis unit 104 is an alarm corresponding to a situation such as when deterioration of the electrical characteristics of the analog switch circuit 101 is detected.

A clear situation such as a failure of the analog switch circuit 101 can be determined relatively easily at the signal processing section 103, so the alarm display section 107 can be notified via the alarm command section 106 without going through the self-diagnosis section 104. to issue an alarm (first alarm command).
In addition, in a situation where there is a slight change such as when deterioration of the electrical characteristics of the analog switch circuit 101 is detected, an alarm (second alarm command) is displayed on the alarm display section 107 after diagnosis by the self-diagnosis section 104. ).
When the alarm display section 107 receives the first alarm command or the second alarm command, it displays an abnormality (abnormality) of the analog switch. This display distinguishes between the case where the settings are made to simply display an abnormality (failure, abnormality), the first alarm command and the second alarm command, and, for example, detailed information is displayed for the second alarm command. You can also set it to

<Effects of the third embodiment>
According to the third embodiment of the present invention, it becomes easier for the user (maintenance person) to check the alarm display of the radiation-resistant circuit, so that equipment can be replaced appropriately. And the soundness of the equipment can be guaranteed.

≪Fourth embodiment≫
The configuration of a radiation-resistant circuit according to a fourth embodiment of the present invention will be described with reference to the drawings.
FIG. 4A is a diagram showing a configuration example of a radiation-resistant circuit according to a fourth embodiment of the present invention.
In FIG. 4A, the radiation-resistant circuit 14 includes an analog switch circuit 101, a battery 311, a signal processing section 103, and a self-diagnosis section 104.
The difference between the radiation-resistant circuit 14 shown in FIG. 4 and the radiation-resistant circuit 11 shown in FIG. 1 is that the pilot signal generation section 102 in FIG. That's true. Other constituent elements are the same, so redundant explanation will be omitted.

In FIG. 4A, as described above, the pilot signal generation section 102 in FIG. 1 (the pilot signal generation section 202 in FIG. 4) is configured with the battery 311.
The battery 311 has a negative pole connected to a ground (GND, earth) 322 and a positive pole connected as a signal line 321 to a first terminal of the input section of the analog switch circuit 101 .
If the battery 311 is a battery that outputs a stable predetermined fixed potential, it has the function of the pilot signal generation section 102 in FIG. 1.
Note that the battery 311 may be installed in a radiation environment or in a non-radiation area. However, if the battery 311 is installed near the analog switch circuit 101, the influence of noise will be reduced and a stable pilot signal can be supplied.
Furthermore, when the battery 311 is installed in a radiation environment, the amount of radiation irradiated to the battery 311 may be reduced by shielding with a radiation shielding material such as lead.

<Effects of the fourth embodiment>
According to the above configuration of the fourth embodiment, the pilot signal generation unit 202 is the battery 311, and there is no need to add any special circuit, so there is an effect that can be achieved with a relatively simple configuration.

《First modification of the fourth embodiment》
As mentioned above, as the fourth embodiment, an example is shown in which a battery is used in the pilot signal generation section, but an example in which a Zener diode is further used is shown in FIG. 4B as a first modification of the fourth embodiment. , will be explained next.

FIG. 4B is a diagram showing a circuit configuration of a pilot signal generation section in a first modification of the fourth embodiment of the present invention.
In FIG. 4B, the pilot signal generation section 302 includes a battery 411, a Zener diode 412, and a resistor 413.
The negative electrode of the battery 411 and the anode of the Zener diode 412 are connected to each other and to ground 422.
A resistor 413 is connected between the positive electrode of the battery 411 and the cathode of the Zener diode 412.
The cathode of the Zener diode 412 is connected to the output terminal 421 of the pilot signal generation section 302.
The output terminal 421 of the pilot signal generation section 302 is connected to the first terminal of the input section of the analog switch circuit 101 in FIG. 4A or FIG. 1.

In FIG. 4B, as described above, the positive electrode of the battery 411 is connected to the cathode of the Zener diode 412 via the resistor 413, so the potential of the output terminal 421 is maintained at the predetermined Zener voltage of the Zener diode 412. It will be done.
Note that even if the current flowing from the output terminal 421 to the first terminal of the input section of the analog switch circuit 101 (FIG. 4A) changes, the voltage of the output terminal 421 is maintained at the predetermined Zener voltage of the Zener diode 412.
Further, even if the battery voltage of the battery 411 fluctuates within a predetermined voltage range, the voltage of the output terminal 421 is maintained at the predetermined Zener voltage of the Zener diode 412.
With the above configuration of FIG. 4B, the pilot signal generation section 302 can output the signal to the output terminal 421 of the pilot signal generation section 302 even if the battery voltage of the battery 411 changes or the current flowing through the analog switch circuit 101 (FIG. 4A) changes. Provides stable voltage.

<Effects of the first modification of the fourth embodiment>
According to the configuration of the first modification of the fourth embodiment, although the configuration is relatively simple, even if the battery voltage of the battery 411 fluctuates within a predetermined voltage range, the analog switch circuit 101 Even if the flowing current changes, there is an effect of supplying a stable voltage to the output terminal 421 of the pilot signal generation section 302.

《Second modification of the fourth embodiment》
As mentioned above, in the first modified example of the fourth embodiment, a circuit configuration example using a Zener diode was shown in the pilot signal generation section, but in a second modified example of the fourth embodiment, a Zener diode is further used. Another circuit configuration example will now be described with reference to FIG. 4C.

FIG. 4C is a diagram showing a circuit configuration of a pilot signal generation section in a second modification of the fourth embodiment of the present invention.
In FIG. 4C, the pilot signal generation section 402 includes a Zener diode 412, a resistor 413, and a capacitor 414. It also includes an input terminal 432, an output terminal 431, and a ground 422.
Zener diode 412 and capacitor 414 are connected in parallel. The anode of the Zener diode 412 is connected to ground 422, and the cathode of the Zener diode 412 is connected to the output terminal 431.

Resistor 413 is connected to input terminal 432 and the cathode of Zener diode 412.
An input voltage is applied between input terminal 432 and ground 422. This input voltage may vary within a predetermined voltage range and over a predetermined period of time. The input voltage is smoothed by a resistor 413 and a capacitor 414. Furthermore, a Zener diode 412 is connected to a connection point between the resistor 413 and the capacitor 414, that is, between the output terminal 431 and the ground 422. Therefore, the Zener voltage of the Zener diode 412 is maintained between the output terminal 431 and the ground 422.

With the above circuit configuration, even if the input voltage applied between the input terminal 432 and the ground 422 fluctuates within a predetermined voltage range, or the current flowing through the analog switch circuit 101 (FIG. 4A) changes, , the potential between the output terminal 431 and the ground 422 is stably maintained at a predetermined voltage (Zener voltage). That is, the output terminal 431 of the pilot signal generation section 402 outputs and supplies a stable voltage.

<Effects of the second modification of the fourth embodiment>
According to the configuration of the second modification of the fourth embodiment, a battery supplying a fixed voltage is not required.
Even if the input voltage fluctuates within a predetermined voltage range, or even if the current flowing through the analog switch circuit 101 changes, the effect of outputting and supplying a stable voltage to the output terminal 431 of the pilot signal generation section 402 is maintained. be.

≪Fifth embodiment≫
The configuration of a radiation-resistant circuit according to a fifth embodiment of the present invention will be described with reference to the drawings.
FIG. 5 is a diagram showing an example in which the pilot signal generation section in the radiation-resistant circuit according to the fifth embodiment of the present invention is configured with a bandgap reference circuit.

In FIG. 5, a bandgap reference circuit 502 shows a specific example of the configuration of the pilot signal generation section 102 in FIG. The configuration of the other radiation-resistant circuit (11) is the same as that in FIG. 1, so a duplicate explanation will be omitted.
A bandgap reference circuit 502 shown in FIG. 5 includes transistors Q1 and Q2, resistors R1, R2, and R3, and an operational amplifier circuit 510.

The base and collector of the transistor Q1 are short-circuited, and the transistor Q1 is so-called diode-connected.
Further, the collector of the transistor Q1 is connected to one end of the resistor R1. The emitter of transistor Q1 is connected to ground (GND). The other end of the resistor R1 is connected to the output terminal 230 (Vout) of the operational amplifier circuit 510.
A connection point between the collector of the transistor Q1 and the resistor R1 is connected to a non-inverting terminal of the operational amplifier circuit 510.

The base and collector of the transistor Q2 are short-circuited, and the transistor Q2 is so-called diode-connected.
Further, the collector of the transistor Q2 is connected to one end of the resistor R3 connected in series.
The emitter of transistor Q2 is connected to ground (GND). Resistor R3 and resistor R2 are connected in series. A connection point between the resistor R3 and the resistor R2, which is the other end of the resistor R3, is connected to the inverting terminal of the operational amplifier 510.
The other end of the resistor R2 is connected to the output terminal 230 of the operational amplifier circuit 510.

Since the bandgap reference circuit 502 having the above circuit configuration is a generally known circuit, detailed description thereof will be omitted. However, the outline is as follows.

In FIG. 5, the combination of a transistor Q1 whose base and collector are short-circuited and a resistor R1 intended to flow a constant current generates a voltage between the base and emitter of the transistor Q1 at their connection point. Note that this voltage is input to the non-inverting terminal of the operational amplifier circuit 510 as described above.
Further, due to the combination of the transistor Q1 whose base and collector are short-circuited, the resistor R2, and the resistor R3, a voltage proportional to the voltage between the base and emitter of the transistor Q2 is generated at the connection point between the resistors R2 and R3. Note that this voltage is input to the inverting terminal of the operational amplifier circuit 510 as described above.

With the above configuration, the voltage applied to the resistor R3 is the difference between the emitter base voltage of the transistor Q1 and the emitter base voltage of the transistor Q2. Furthermore, considering that the currents flowing through the resistors R2 and R3 are equal, the output voltage V _out of the operational amplifier circuit 510 is proportional to the emitter-base voltage V _BE1 of the transistor Q1 and the thermal voltage VT (proportionality constant K). It becomes the sum of KVT. That is,
V _out =V _BE1 +KVT...(Formula 1)
becomes. Note that the proportionality constant K is determined by the ratio of the resistance values of the resistor R1, the resistor R2, and the resistor R3.
Since V _BE1 and KVT in Equation 1 have positive and negative temperature coefficients, if the proportionality constant K is appropriately selected, a reference voltage circuit that is resistant to temperature changes can be provided.
Furthermore, since the V _BE1 mentioned above is a voltage value related to the bandgap voltage of a semiconductor such as silicon, the circuit shown in FIG. 5 is generally referred to as a "bandgap reference circuit."

Note that the bandgap reference circuit 502 may be installed in a radiation environment or in a non-radiation area.
When the bandgap reference circuit 502 is installed in a radiation region, it is preferable to use a semiconductor element having a higher bandgap than Si, such as SiC, in order to increase radiation resistance. Furthermore, the amount of radiation irradiated may be reduced by shielding with lead or the like.
Note that when the bandgap reference circuit 502 is covered with a shielding material such as lead, it is also possible to use a Si semiconductor for the transistors Q1 and Q2 and the operational amplifier 510 in FIG.

As described above, the bandgap reference circuit 502 shown in FIG. 5 is a circuit that generates a predetermined voltage value using the bandgap voltage of a semiconductor material, and is an example of the configuration of the pilot signal generation section 102 in FIG. This shows that.
The output (Vout) of the output terminal 230 of the bandgap reference circuit 502 shown in FIG. Apply.

Note that in FIG. 5, the operational amplifier 510 is connected between Vcc as a power source and GND. The power supplies Vcc and GND have substantially the same meaning as the power supplies VDD and VSS of the multiplexer circuit 110 in FIG. 6A, which will be described later, and perform the same functions.
However, in order to ensure proper voltage differences for operation and to prevent noise from entering, separate power supply systems may be used. When the power supply system is used separately, it may be written separately as (Vcc, GND) or (VDD, VSS) as described above.

<Effects of the fifth embodiment>
By configuring the pilot signal generation section in the radiation-resistant circuit of the fifth embodiment with a bandgap reference circuit, a stable voltage can be supplied to the output terminal as the pilot signal generation section even against fluctuations in the supply voltage and changes in the environmental temperature. It has the effect of supplying

≪Sixth embodiment≫
The configuration of a radiation-resistant circuit according to a sixth embodiment of the present invention will be described with reference to FIGS. 6A, 6B, and 6C.
FIG. 6A is a diagram showing an example in which a multiplexer circuit 110 is configured using a plurality of analog switch circuits 101 shown in FIG. 1 in a radiation-resistant circuit according to a sixth embodiment of the present invention.

In FIG. 6A, the multiplexer circuit 110 includes a plurality of analog switch circuits (SW0, SW1, SW2, SW3) and a decoder circuit (DEC) 120. Further, an amplifying section 116 that amplifies the output (output signal D) of the multiplexer circuit 110 is provided outside the multiplexer circuit 110.
The analog switch circuits (SW0, SW1, SW2, SW3) in FIG. 6A each correspond to the analog switch circuit 101 in FIG. 1.
Note that the other configurations of the radiation-resistant circuit (11) are generally the same as those in FIG. 1, so redundant explanation will be omitted.

In FIG. 6A, four analog switch circuits SW0, SW1, SW2, and SW3 input signals S0, S1, S2, and S3 to their respective first terminals.
Signal S0 is an output signal of the pilot signal generation section (102). Further, the signals S1, S2, and S3 are signals of a measuring device installed inside a PCV (containment vessel of a nuclear power plant) or output signals of another pilot signal generation section.
Further, the second terminals of each of the analog switch circuits SW0, SW1, SW2, and SW3 are connected to each other and serve as output terminals of the multiplexer circuit 110. Output signal D is output from this output terminal.
Further, control signals A0 and A1 of the decoder circuit 120 are input.
Further, the multiplexer circuit 110 is supplied with a positive power supply VDD and a negative power supply VSS.

In FIG. 6A, the decoder circuit 120 includes four NAND circuits 140, 141, 142, 143 and six inverter circuits 130, 131, 150, 151, 152, 153.
The decoder circuit 120 receives control signals A0 and A1.
The control signal A0 is input to the first input terminal of each of the NAND circuits 141 and 143. Further, the control signal A0 is connected to an input terminal of the inverter circuit 130. The output terminal of the inverter circuit 130 is input to the first input terminal of each of the NAND circuits 140 and 142.
The control signal A1 is input to the second input terminal of each of the NAND circuits 142 and 143. Further, the control signal A1 is connected to an input terminal of the inverter circuit 131. The output terminal of the inverter circuit 131 is input to the second input terminal of each of the NAND circuits 140 and 141.

The output signal of the NAND circuit 140 is input to an inverter circuit 150. The output signal SW0I of the NAND circuit 140 and the output signal SW0h of the inverter circuit 150 are input to the gate of pMOS and the gate of nMOS, respectively, of analog switch circuit SW0.
The output signal SW0I and the output signal SW0h have an inverted relationship with each other due to the operation of the inverter circuit 150, so when the output signal SW0I of the NAND circuit 140 is at a low potential (negative potential, L, 0), the output signal of the inverter circuit 150 is When the signal SW0h becomes a high potential (positive potential, H, 1), the analog switch circuit SW0 becomes conductive (ON).
Note that the output signal SW0I of the NAND circuit 140 is at a low potential (negative potential, L, 0) when both the control signal A0 and the control signal A1 of the decoder circuit 120 are at a low potential (negative potential, L, 0). It is.

The output signal of the NAND circuit 141 is input to an inverter circuit 151. The output signal SW1I of the NAND circuit 141 and the output signal SW1h of the inverter circuit 151 are input to the pMOS gate and the nMOS gate, respectively, of the analog switch circuit SW1.
The output signal SW1I and the output signal SW1h have an inverted relationship with each other due to the operation of the inverter circuit 151, so when the output signal SW1I of the NAND circuit 141 is at a low potential (negative potential, L, 0), the output of the inverter circuit 151 is When the signal SW1h becomes a high potential (positive potential, H, 1), the analog switch circuit SW1 becomes conductive (ON).
Note that the output signal SW1I of the NAND circuit 141 has a low potential (negative potential, L, 0) because the control signal A0 of the decoder circuit 120 has a high potential (positive potential, H, 1), and the control signal A1 has a low potential (negative potential, L, 0). This is a case of low potential (negative potential, L, 0).

The output signal of the NAND circuit 142 is input to the inverter circuit 152. The output signal SW2I of the NAND circuit 142 and the output signal SW2h of the inverter circuit 152 are input to the pMOS gate and the nMOS gate, respectively, of the analog switch circuit SW2.
The output signal SW2I and the output signal SW2h have an inverted relationship with each other due to the operation of the inverter circuit 152, so when the output signal SW2I of the NAND circuit 142 is at a low potential (negative potential, L, 0), the output signal of the inverter circuit 152 is When the signal SW2h becomes a high potential (positive potential, H, 1), the analog switch circuit SW2 becomes conductive (ON).
Note that the output signal SW2I of the NAND circuit 142 has a low potential (negative potential, L, 0) because the control signal A0 of the decoder circuit 120 has a low potential (negative potential, L, 0) and the control signal A1 has a low potential (negative potential, L, 0). This is a case of high potential (positive potential, H, 1).

The output signal of the NAND circuit 143 is input to the inverter circuit 153. The output signal SW3I of the NAND circuit 143 and the output signal SW3h of the inverter circuit 153 are input to the pMOS gate and the nMOS gate, respectively, of the analog switch circuit SW3.
The output signal SW3I and the output signal SW3h have an inverted relationship with each other due to the operation of the inverter circuit 153, so when the output signal SW3I of the NAND circuit 143 is at a low potential (negative potential, L, 0), the output signal of the inverter circuit 153 is When the signal SW3h becomes a high potential (positive potential, H, 1), the analog switch circuit SW3 becomes conductive (ON).
Note that the output signal SW3I of the NAND circuit 143 is at a low potential (negative potential, L, 0) when both the control signal A0 and the control signal A1 of the decoder circuit 120 are at a high potential (positive potential, H, 1). It is.

In the above configuration, the decoder circuit 120 is configured such that when any one of the analog switch circuits SW0, SW1, SW2, and SW3 becomes conductive (ON), all the other analog switch circuits become non-conductive (OFF). It is configured.
Furthermore, the analog switch circuits SW0, SW1, SW2, and SW3 operate as analog circuits, and the decoder circuit 120 operates as a digital circuit. also operates stably.

FIG. 6B is a diagram showing a truth table of the output signal D for the control signals A0 and A1 of the decoder circuit 120 in the multiplexer circuit 110 shown in FIG. 6A in the radiation-resistant circuit according to the sixth embodiment of the present invention.
In FIG. 6B, symbols A0 and A1 indicate the control signal A0 and control signal A1, respectively, and symbol D indicates the output signal D of the multiplexer circuit 110.
Depending on the combination of 1 or 0 of the control signal A0 and the control signal A1, the output signal D is output as one of the input signals S0, S1, S2, and S3.

FIG. 6C shows analog switch circuits SW0, SW1, SW2, and SW3 in response to control signals A0 and A1 of the decoder circuit in the multiplexer circuit 110 shown in FIG. 6A in the radiation-resistant circuit according to the sixth embodiment of the present invention. FIG. 3 is a diagram showing a logical expression table for configuring a logic circuit that selects one of the two.
The logic configuration is shown in which one of the analog switch circuits SW0, SW1, SW2, and SW3 is selected in response to the control signals A0 and A1 by a combination of the logic of the NAND circuit and the inverter circuit shown in FIG. 6C.

As described above, with the configurations shown in FIGS. 6A, 6B, and 6C, the multiplexer circuit 110 allows the decoder circuit 120 based on the control signals A0, A1 to conduct ( ON), and one of the signals S0, S1, S2, and S3 is output from the multiplexer circuit 110 (output signal D).
Further, the output signal D from the multiplexer circuit 110 is amplified by the amplification section 116 and input to the signal processing section 103 (FIG. 1). Note that the amplifying section 116 is not an essential element. For example, a configuration may be adopted in which the signal detection sensitivity of the signal processing unit 103 is increased.
Regarding the operations after the signal processing unit 103, a description that overlaps with the description in FIG. 1 will be omitted.

As described above, in the configuration shown in FIG. 6A, the output (output signal ), it becomes possible to diagnose the deterioration of the analog switch circuit SW0 as shown in FIG. Furthermore, measurement signals from measurement equipment installed inside the PCV are input to the remaining input signals S1, S2, and S3.

It is known that if semiconductor devices have the same layout and the same manufacturing line, the degree of deterioration due to radiation will be closely correlated, so the diagnosis results for analog switch circuit SW0 will also be applied to analog switch circuits SW1, SW2, and SW3. Is possible.
This method makes it possible to guarantee the soundness of a circuit (multiplexer circuit 110) that uses analog switch circuits SW0, SW1, SW2, and SW3, such as multiplexer circuit 110.
With the above configuration, a radiation-resistant multiplexer circuit using SiC semiconductor elements is realized.

<Summary of the sixth embodiment>
In the radiation-resistant circuit according to the sixth embodiment, a multiplexer circuit 110 is configured using a plurality of analog switch circuits (SW0, SW1, SW2, SW3).
There are several measuring devices such as thermometers that do not have electronic circuits installed inside the PCV (containment vessel of a nuclear power plant), but the outputs of multiple measuring devices are connected to multiple analog switch circuits. When taking out a plurality of outputs of the analog switch circuit to the outside of the PCV, there is a limit to the number of penetrations in the wall of the PCV for pulling out the cables to the outside of the PCV.
Therefore, by adopting the configuration of the multiplexer circuit 110, the outputs of the plurality of analog switch circuits (SW0, SW1, SW2, SW3) are unified and taken out to the outside of the PCV. Using this single signal line, multi-point measurements of a plurality of measurement devices within the PCV are performed outside the PCV.

<Effects of the sixth embodiment>
A decoder circuit uses multiple analog switch circuits consisting of parallel circuit configurations of pMOS and nMOS and multiple control signals to process multiple signals from multiple measurement devices installed at multiple points within the PCV (nuclear power plant containment vessel). By using a multiplexer circuit equipped with a multiplexer circuit, the plurality of signals subjected to the multi-point measurement can be outputted to the outside of the PCV as one output.
The multiple signals measured at multiple points can be output as a single output and can be taken out through a cable from one penetration of the PCV wall, making it easy to ensure the PCV's radiation protection function. There is an effect.
Furthermore, since it can be taken out as a single cable to the outside from one penetration (penetrating part) of the PCV wall, it has the effect of reducing costs by reducing the number of cables.

Further, by reducing the number of cables described above, there is an effect that the decommissioning work of a nuclear power plant can be made more efficient.
Further, as described above, the multiplexer circuit has an analog switch circuit composed of a parallel circuit configuration of pMOS and nMOS, and has the effect of enabling advanced sensing under high radiation conditions using SiC technology that is resistant to radiation.
Further, it has the effect of enabling predictive diagnosis of the multiplexer circuit itself.
Furthermore, there is an effect that the efficiency of plant operation can be improved by high-level sensing within the PCV.

<<Modification of the sixth embodiment>>
The configuration of a multiplexer circuit in a radiation-resistant circuit according to a modification of the sixth embodiment of the present invention will be described with reference to FIG. 7.
FIG. 7 is a diagram showing another configuration example of a multiplexer circuit in a radiation-resistant circuit according to a modification of the sixth embodiment of the present invention.

In FIG. 7, a multiplexer circuit 110B as a modification of the sixth embodiment includes an analog switch switching circuit 170 in addition to the multiplexer circuit 110. Note that since the multiplexer circuit 110 has been explained with reference to FIG. 6, duplicate explanation will be omitted.
The analog switch switching circuit 170 receives the signal S3A and the signal S3B. A control signal A3 is input thereto, and the signal S3A and signal S3B are switched and outputted using the control signal A3.
The output signal from the analog switch switching circuit 170 is input to the multiplexer circuit 110 as a signal S3 of the multiplexer circuit 110.

In FIG. 7, a signal S3A is a measurement signal of a measuring device, and corresponds to the signal S3 in FIG. 6.
Furthermore, the signal S3B is a pilot signal generated by a pilot signal generation unit different from that of the signal S0.

If the analog switch switching circuit 170 selects the signal S3A, the signal S3 (S3A) of the multiplexer circuit 110 in FIG. 7 becomes the measurement signal S3 (S3A) of the measuring instrument, and has the same function as the multiplexer circuit 110 in FIG. take action.
Further, if the analog switch switching circuit 170 selects the signal S3B, the signal S3 (S3B) of the multiplexer circuit 110 in FIG. 7 becomes a pilot signal (S3B) generated from a pilot signal generation section different from the signal S0. Therefore, pilot signals generated from different pilot signal generation units can be selected as the output of the multiplexer circuit 110B, and more accurate diagnosis of the effects of radiation is possible.

<Effects of the modification of the sixth embodiment>
The multiplexer circuit 110B as a modified example of the sixth embodiment includes an analog switch switching circuit 170, and allows selection of the pilot signal signal S3B generated from a pilot signal generation section different from the signal S0. The circuit 110B has a configuration that allows more accurate diagnosis of the effects of radiation.

≪Other embodiments≫
Note that the present invention is not limited to the embodiments described above, and includes various modifications. For example, the embodiments described above are described in detail in order to explain the present invention in an easy-to-understand manner, and the present invention is not necessarily limited to having all the configurations described. Further, it is possible to replace a part of the configuration of one embodiment with a part of the configuration of another embodiment, and furthermore, it is possible to add or add part or all of the configuration of another embodiment to the configuration of one embodiment. It is also possible to delete or replace.
Other embodiments and modifications will be further described below.

《About semiconductor elements》
In the first embodiment, a case has been described in which SiC is used for pMOS or nMOS as a semiconductor having a wider band gap than Si and stronger against radiation.
However, semiconductors that have a wider band gap than Si and are more resistant to radiation are not limited to SiC (silicon carbide). For example, semiconductors with a wide band gap include compound semiconductors such as GaAs (gallium arsenide), GaN (gallium nitride), AlP (aluminum phosphide), and InP (indium phosphide).

Note that SiC is a combination of group IV and group IV, and like Si, it is a group IV group, so when producing pMOS and nMOS, a trivalent (group V) semiconductor is used to form a p-type semiconductor and an n-type semiconductor, respectively. B (boron) and pentavalent (group III) P (phosphorus) are implanted as impurities.
Also, for example, GaAs is a group III-V combination. When Ga (gallium) is contained in a larger amount than As (arsenic), it becomes a p-type semiconductor, and when As is contained in a larger amount than Ga, it becomes an n-type semiconductor.
As described above, by using a semiconductor (including a compound semiconductor) that has a wider band gap than Si and is resistant to radiation, a pMOS or nMOS that is resistant to radiation can be formed.

《About MOSFET》
In the first embodiment, pMOS and nMOS were simply described as MOSFET. This MOSFET has the above-mentioned effects in a planar (horizontal) structure MOSFET, a trench (vertical) structure MOSFET, and even a superjunction MOSFET.

《Analog switch circuit》
In FIG. 1, the analog switch circuit 101 has been described as having a parallel circuit configuration of a pMOS 111 and an nMOS 112. However, the analog switch circuit 101 is not limited to this configuration.
As described above, since the pMOS 111 has a dominant influence on radiation, the analog switch circuit (101) may be configured with one pMOS 111.
The analog switch circuit 101 having a parallel circuit configuration of pMOS 111 and nMOS 112 has better electrical characteristics as an analog switch than the analog switch circuit (101) having only one pMOS 111. On the other hand, the analog switch circuit (101) having a configuration including a single pMOS 111 has higher sensitivity to the effects of radiation.
Furthermore, in general, when a pMOS and an nMOS have the same shape, the nMOS has a higher current driving ability, so the shape of the pMOS may be set to be relatively larger to compensate for this. In this case, the current drive capabilities of the pMOS and nMOS are balanced, and the shape of the pMOS is made relatively large, so the sensitivity to the effects of radiation is increased.

《About the generated signal of the pilot signal generation section》
In FIGS. 4A, 4B, and 5, the explanation has been made on the assumption that the potential of the output signal of the pilot signal generation section is a predetermined potential, and that the potential basically does not change.
However, the potential of the output signal of the pilot signal generation section is not limited to basically not changing.
For example, the output signal of the pilot signal generator shown in FIG. 1 is output as a periodic 1, 0 rectangular wave with a predetermined width. In this case, in the signal processing section 103 of FIG. 1, information on the influence of the analog switch circuit 101, particularly the pMOS 111, on radiation can be obtained for each of the two types of output signals of the pilot signal generation section. In other words, there is a possibility that more accurate detection can be performed using the two pieces of information.

《About the alarm display section》
In the third embodiment shown in FIG. 3, an alarm command unit 106 and an alarm display unit 107 are provided, and an alarm is displayed for abnormality (abnormality) in the radiation-resistant circuit 13 by a first alarm command or a second alarm command. The configuration displayed in section 107 has been explained.
However, the configuration for displaying alarms is not limited to the above configuration.
For example, the configuration may be simplified such that the alarm display unit 107 displays an abnormality in the radiation-resistant circuit 13 based on an alarm command from the self-diagnosis unit 104.
Furthermore, the alarm display section 107 may display not only a visual display but also a voice or acoustic warning. Further, the alarm display unit 107 may transmit an electrical signal related to the alarm to related facilities including a nuclear power plant.

《Multiplexer circuit》
In the multiplexer circuit 110 shown in FIG. 6A, a case has been described in which the number of analog switch circuits (SW0, SW1, SW2, SW3) made of nMOS and pMOS is four, but the number is not limited to four. The number may be five or more, or may be two or three.
Further, the configuration of the decoder circuit 120 is also changed depending on the number of analog switch circuits.
Further, in the decoder circuit 120 shown in FIG. 6A, an example is shown in which a NAND circuit and an inverter circuit are used, but a NOR circuit may also be used.

In addition, in the explanation of FIG. 6A, regarding the signals S0, S1, S2, and S3 input to each of the four analog switch circuits SW0, SW1, SW2, and SW3, the signal S0 is the output signal of the pilot signal generation section, Although the signals S1, S2, and S3 have been described as signals from measuring instruments, the present invention is not limited to this combination of signals. The output signal of the pilot signal generation section may be input to a circuit other than the analog switch circuit SW0.
Further, signals from a plurality of different pilot signal generators may be input to the multiplexer circuit 110.
Furthermore, the output signal of one pilot signal generation section may be input to the first terminals of a plurality of analog switch circuits.

Note that the control signals A0 and A1 in FIG. 6A may be taken into one cable from outside the PCV (containment vessel of a nuclear power plant).
Further, in FIG. 6A, the case where the amplifying section 116 is installed outside the multiplexer circuit 110 is shown, but it may be installed inside the multiplexer circuit 110.
In addition, in FIG. 7, it has been explained that the multiplexer circuit 110B is configured by including the analog switch switching circuit 170 outside the multiplexer circuit 110, but the analog switch switching circuit 170 is incorporated into the multiplexer circuit 110 as one chip. may be configured.

<SiC integrated circuits other than multiplexer circuits>
In FIG. 6A, an example has been described in which the multiplexer circuit 110 is provided with a plurality of analog switch circuits using pMOS and nMOS made of SiC.
However, the effects on the characteristics of the analog switch circuit using pMOS and nMOS made of SiC included in the sixth embodiment are not limited to the multiplexer circuit 110.
If an SiC integrated circuit is provided with an analog switch circuit using pMOS and nMOS made of SiC, and the deterioration of this analog switch circuit due to radiation is detected, the radiation deterioration of the SiC integrated circuit can be detected. It becomes possible to check the soundness.

《About analog switch switching circuit》
In the description of the analog switch switching circuit 170 with reference to FIG. 7, the signal S3B was described as "a pilot signal generated and output from a pilot signal generation unit different from the signal S0." However, the signal S0 may be used as the signal S3B. In this case, since the influence of radiation on the pMOS and nMOS of two different analog switch circuits in the multiplexer circuit 110 is detected for the pilot signal of the same pilot signal generation section, the detection results can be compared. , the detection accuracy can also be grasped, which has the effect of increasing the reliability of detection.
Further, in FIG. 7, one analog switch switching circuit 170 is shown, but a plurality of analog switch switching circuits 170 may be provided.
Note that the control signals A0, A1, and A3 in FIG. 7 may be taken into one cable from outside the PCV (containment vessel of a nuclear power plant).

11, 12, 13, 14 Radiation-resistant circuit 101, SW0, SW1, SW2, SW3 Analog switch circuit 102, 202, 302, 402, 502 Pilot signal generation section 103 Signal processing section 104 Self-diagnosis section 105 Database section (DB)
106 Alarm command section 107 Alarm display section 110, 110B Multiplexer circuit 111 pMOS
112nMOS
116 Amplification section 120 Decoder circuit (DEC)
130, 131, 150, 151, 152, 153 Inverter circuit 140, 141, 142, 143 NAND circuit 170 Analog switch switching circuit 311, 411 Battery 412 Zener diode 413, R1, R2, R3 Resistor 414 Capacitor 502 Band gap reference circuit ( pilot signal generator)
510 Operational amplifier circuit 1003 First terminal (first terminal of analog switch circuit)
1004 2nd terminal (2nd terminal of analog switch circuit)
Q1, Q2 transistor

Claims (15)

An analog switch circuit installed in the radiation area and consisting of a parallel circuit of pMOS and nMOS,
a pilot signal generation unit that generates a pilot signal that is a known signal and inputs it to a first terminal of the analog switch circuit;
a signal processing unit that is installed in a non-radiation area and performs signal processing related to radiation deterioration based on the pilot signal that passes through the analog switch circuit and is output from a second terminal of the analog switch circuit;
a self-diagnosis unit installed in a non-radiation area and diagnosing the deterioration status of the analog switch circuit due to radiation and the deterioration status of a self-device including the analog switch circuit based on the output of the signal processing unit ; Prepare,
The signal processing section includes:
In the pMOS, which deteriorates earlier than the nMOS due to the radiation irradiation, a characteristic difference between the pMOS and the nMOS caused by the deterioration of the pMOS causes a difference in the pilot signal passing through the analog switch circuit. processing and outputting the distortion of the signal caused by the signal;
A radiation-resistant circuit characterized by: In claim 1,
The signal processing unit performs signal processing related to radiation deterioration of the analog switch circuit based on a change in the current flowing through the pMOS and the current flowing through the nMOS, which is caused by the radiation deterioration of the pMOS being faster than the nMOS. conduct
A radiation-resistant circuit characterized by: In claim 1,
The pMOS and the nMOS of the analog switch circuit are configured using a semiconductor having a band gap wider than a band gap of silicon.
A radiation-resistant circuit characterized by: In claim 3 ,
The pMOS and the nMOS of the analog switch circuit are configured with a semiconductor made of silicon carbide.
A radiation-resistant circuit characterized by: In claim 1,
The analog switch circuit and the pilot signal generation section are installed in a radiation area,
The signal processing unit and the self-diagnosis unit are installed in a non-radiation area.
A radiation-resistant circuit characterized by: In claim 1,
comprising a database unit that has in advance a database of signal distortion caused by a difference in deterioration between pMOS and nMOS in the analog switch circuit of the pilot signal of the pilot signal generation unit in response to radiation irradiation;
The self-diagnosis section refers to data in the database section when diagnosing the output signal of the signal processing section.
A radiation-resistant circuit characterized by: In claim 1,
The pilot signal generation section is configured with a bandgap reference circuit that outputs a signal corresponding to a semiconductor bandgap.
A radiation-resistant circuit characterized by: In claim 1,
The pilot signal generation unit is configured with a fixed voltage battery or a Zener diode.
A radiation-resistant circuit characterized by: In claim 5,
comprising an alarm display unit that displays an abnormality in the analog switch circuit installed in a radiation area,
The alarm display section displays an alarm in response to an alarm command from the signal processing section or the self-diagnosis section.
A radiation-resistant circuit characterized by: a multiplexer circuit installed in a radiation region and having an analog switch circuit configured of parallel circuits of pMOS and nMOS, and a decoder circuit for selecting the plurality of analog switch circuits;
a pilot signal generation unit that generates a pilot signal that is a known signal and inputs it to a first terminal of each of the plurality of analog switch circuits of the multiplexer circuit;
a signal processing unit that is installed in a non-radiation area and performs signal processing related to radiation deterioration based on the pilot signal that passes through the analog switch circuit and is output from each second terminal of the analog switch circuit;
a self-diagnosis unit installed in a non-radiation area and diagnosing the deterioration status of the analog switch circuit due to radiation and the deterioration status of a self-device including the analog switch circuit based on the output of the signal processing unit ; Prepare,
The multiplexer circuit inputs either the signal of the pilot signal generation unit or the signal of one or more measuring instruments to the first terminal of each of the plurality of analog switch circuits, and the second terminals of the analog switch circuits are connected to each other, and the signal of the second terminal of one analog switch circuit selected by the decoder circuit is output as the output of the multiplexer circuit,
The signal processing section includes:
In the pMOS, which deteriorates earlier than the nMOS due to the radiation irradiation, a characteristic difference between the pMOS and the nMOS caused by the deterioration of the pMOS causes a difference in the pilot signal passing through the analog switch circuit. processing and outputting the distortion of the signal caused by the signal;
A radiation-resistant circuit characterized by: In claim 10,
The signal of the pilot signal generation section is connected to one of the first terminals of the plurality of analog switch circuits of the multiplexer circuit.
A radiation-resistant circuit characterized by: In claim 10,
comprising an analog switch switching circuit capable of switching between a signal from the pilot signal generation unit and a measurement signal from the measurement device;
A radiation-resistant circuit characterized by: In claim 10,
The multiplexer circuit, the pilot signal generation unit, and the measurement device are installed in a radiation area,
The signal processing unit and the self-diagnosis unit are installed in a non-radiation area.
A radiation-resistant circuit characterized by: In claim 10,
a plurality of control signals controlling the decoder circuit of the multiplexer circuit are housed in one cable;
A radiation-resistant circuit characterized by: comprising the radiation-resistant circuit according to any one of claims 1 to 14,
A self-diagnosis method for a radiation-resistant circuit that diagnoses deterioration of the radiation-resistant circuit by detecting signal distortion caused by a difference in deterioration between the pMOS and nMOS installed in a radiation area.

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