Power supplies and measuring equipment

Abstract

To provide a low-cost power supply device which offers superior radiation resistance and is easy to operate, and to provide a measurement device comprising the same.SOLUTION: A power supply device provided herein comprises a power supply circuit with operational amplifiers made of semiconductors with bandgaps greater than that of silicon, the power supply circuit being configured to output desired voltages. An output of each operational amplifier is designed to be equal to or less than a radiation-induced saturation region upper limit corresponding to an output value of the operational amplifier at the time when deterioration due to radiation irradiation converges.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a power supply device for use in a radiation environment and a measuring instrument that utilizes the power supply device. [Background technology]

[0002] In environments exposed to radiation, such as nuclear power plants, there is a need to measure a variety of things, including temperature, water levels, radiation, etc. However, it is difficult to use measuring instruments, especially in high radiation environments, because the semiconductor elements contained in the electronic circuits of measuring instruments deteriorate due to the ionization effect of radiation (hereinafter referred to as "radiation deterioration").

[0003] One of the causes of failure of these measuring instruments due to radiation is failure of the power supply circuit, which contains semiconductor elements. Radiation degradation of op-amps (short for operational amplifier), which are generally used as amplifiers in power supply circuits, reduces the output of the power supply circuit, causing the performance of the measuring instruments to deteriorate. In general, to prevent attenuation of the power output, the power supply circuit is placed near the measuring instruments or built into the measuring instruments. In addition, since op-amps amplify according to the potential difference between the input terminals using a differential amplifier circuit composed of at least two transistors, degradation of individual transistors makes the performance of the op-amp prone to deterioration (failure).

[0004] As a method for ensuring that electronic circuits having semiconductor elements operate normally in a radiation environment, a method is known in which semiconductor elements using silicon carbide (SiC) are irradiated with radiation in advance, and then incorporated into the actual device once the degradation has ceased, as disclosed in Patent Document 1. This method can improve radiation resistance, but there are concerns that the method uses a radiation source and therefore requires complicated management and is costly. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2020-43187 A Summary of the Invention [Problem to be solved by the invention]

[0006] To address the problem of radiation degradation of the semiconductor elements that make up the power supply circuit mentioned above, the inventors of the present application have significantly improved the radiation resistance of the power supply circuit by using a high bandgap semiconductor such as SiC instead of the conventional silicon semiconductor for the operational amplifier, which is the component part of the power supply circuit that is most vulnerable to radiation.

[0007] However, even with this measure, if the cumulative dose of radiation irradiated in advance to the semiconductor element is on the order of kGy to MGy, the semiconductor element (electronic circuit) may still be degraded by radiation. Therefore, it is necessary to reduce the effects of radiation degradation of electronic circuits even in high radiation environments, but as mentioned above, measures that involve prior irradiation with radiation are costly and require complicated management.

[0008] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a power supply device and a measuring instrument which are excellent in radiation resistance, easy to operate, and low in cost. [Means for solving the problem]

[0009] In order to solve the above problems, a power supply device according to one aspect of the present invention includes a power supply circuit having an operational amplifier made of a semiconductor having a band gap larger than that of silicon, and outputting a predetermined voltage, the output of the operational amplifier being set to be equal to or lower than an upper limit of a radiation-induced saturation region, the upper limit of the radiation-induced saturation region being the output value of the operational amplifier at the point in time when degradation of the operational amplifier due to exposure to radiation has converged.

[0010] A measuring instrument according to one aspect of the present invention includes the power supply device described above, and a measuring section that performs measurements using a predetermined voltage output by a power supply circuit of the power supply device. Effect of the Invention

[0011] According to at least one aspect of the present invention, it is possible to provide a power supply device and a measuring instrument that are excellent in radiation resistance, easy to operate, and low cost. Problems, configurations and effects other than those described above will become apparent from the following description of the embodiments. [Brief description of the drawings]

[0012] [Figure 1] 1 is a diagram illustrating an example of the configuration of a power supply device according to a first embodiment of the present invention. [Diagram 2] 1 is a diagram showing an example of a usage environment of a power supply device according to a first embodiment of the present invention. [Diagram 3] FIG. 4 is a diagram showing a change in output range according to the radiation exposure dose of the operational amplifier according to the first embodiment of the present invention. [Figure 4] FIG. 6 is a diagram illustrating an example of the configuration of a power supply device according to a second embodiment of the present invention. [Diagram 5] FIG. 13 is a diagram illustrating an example of the configuration of a measuring device according to a third embodiment of the present invention. [Figure 6] FIG. 13 is a diagram illustrating an example of the configuration of a measuring device according to a fourth embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, examples of embodiments of the present invention will be described with reference to the accompanying drawings. In this specification and the accompanying drawings, components having substantially the same functions or configurations are designated by the same reference numerals, and duplicated descriptions will be omitted.

[0014] <First embodiment> First, a power supply device according to a first embodiment of the present invention will be described. FIG. 1 is a diagram showing an example of the configuration of a power supply device according to a first embodiment of the present invention. The illustrated power supply device 1 includes a power supply circuit 10 having a semiconductor amplifying element. The semiconductor amplifying element is an operational amplifier 11 made of a material (e.g., silicon carbide (SiC)) that has a larger band gap and is more radiation resistant than silicon. For example, a feedback resistor 12 that returns the output of the operational amplifier 11 to one of its input terminals (e.g., an inverting input terminal) is connected between the output terminal of the operational amplifier 11 and the input terminal. The other input terminal (e.g., a non-inverting input terminal) of the operational amplifier 11 is grounded. The positive and negative power supply terminals are not shown. The power supply circuit 10 receives power from an external source and outputs power to a measurement unit of a measuring device or the like.

[0015] 1 shows only a part of the power supply circuit 10. For example, the operational amplifier 11 is configured as an inverting amplifier circuit, but may be a non-inverting amplifier circuit.

[0016] Here, the environment in which the power supply device 1 is used will be described with reference to FIG. FIG. 2 is a diagram showing an example of an environment in which the power supply device 1 is used. The measuring instrument 30 has a built-in power supply device 1 (power supply circuit 10). As mentioned above, to prevent attenuation of the power output, the power supply circuit is placed near the measuring instrument or is built into the measuring instrument. FIG. 2 shows an example in which a power supply voltage of 24V is supplied from a master power source 20 (external power source) in a low radiation environment to a measuring instrument 30 used in a high radiation environment. In the measuring instrument 30, the power supply device 1 (power supply circuit 10) converts the 24V power supply voltage to ±4V and uses it as a driving power source for the operational amplifier 11. This voltage value is one example.

[0017] In this way, the measuring instrument 30 receives power from the external power source 20, and the power supply voltage is stepped down by the power supply unit 1 (power supply circuit 10) built into the measuring instrument 30 and used for measurement, thereby preventing attenuation of the power output of the power supply circuit 10.

[0018] Returning to the description of the power supply device 1 in FIG. 1, as shown in FIG. 3 described later, in this embodiment, the output of the operational amplifier 11 constituting the power supply circuit 10 is operated below the upper limit of the radiation-induced saturation region. The radiation-induced saturation region is a range below the output value at the point where the upper limit of the output value of the operational amplifier 11, which has a larger band gap than silicon, decreases due to radiation exposure and the decrease converges (saturates). In other words, the upper limit of the radiation-induced saturation region is the output value of the operational amplifier 11 at the point where the deterioration of the operational amplifier 11 due to radiation exposure converges. If the output of the operational amplifier 11 is within the range of the radiation-induced saturation region, the operational amplifier 11 can amplify the input linearly. This will be specifically described with reference to FIG. 3.

[0019] In this embodiment, the output of the operational amplifier 11 is set to be equal to or lower than the upper limit of the radiation-induced saturation region by adjusting the circuit elements (e.g., feedback resistor 12) constituting the power supply circuit 10 (FIG. 1). For example, a resistor (not shown) is connected to one input terminal (e.g., inverting input terminal) of the operational amplifier 11, and the magnitude of the amplification factor of the inverting amplifier circuit including the operational amplifier 11 and each resistor is determined by the ratio of the resistor (not shown) to the feedback resistor 12. Therefore, by adjusting the resistance value of the feedback resistor 12, the magnitude of the output voltage of the inverting amplifier circuit can be set. Even in the case of a non-inverting amplifier circuit, the idea of ​​adjusting the output voltage by the resistance value of the feedback resistor 12 is the same.

[0020] The values ​​of resistance, etc. of the circuit elements are determined by conducting an experiment in which a power supply circuit having the same configuration as the power supply circuit 10 is irradiated with radiation. Alternatively, the values ​​of resistance, etc. of the circuit elements may be calculated by simulation. Basically, the input voltage (externally supplied power) of the operational amplifier 11 is constant, so this can be achieved by adjusting the values ​​of resistance, etc. of the necessary circuit elements.

[0021] By configuring the power supply circuit 10 in which the operational amplifier 11 is implemented in this way, the power supply circuit 10 becomes less susceptible to the effects of radiation deterioration. Therefore, the power supply circuit 10 can stably provide an accurate power supply voltage with a simple configuration even in a high radiation environment.

[0022] 3 is a diagram showing a change in the output range according to the radiation exposure dose of the operational amplifier 11. The horizontal axis of FIG.

[0023] In a semiconductor amplifying element such as the operational amplifier 11, for example, when an insulating layer is irradiated with radiation, electron-hole pairs are generated by the Compton effect, and fixed charges and interface states are formed at the interface between the insulating layer and the semiconductor. This effect causes fluctuations in the threshold voltage, degrading the characteristics of the semiconductor element.

[0024] In response to this, the inventors have changed the material of the operational amplifier 11 from Si (silicon), a conventional semiconductor element material, to SiC, a wide band gap semiconductor with excellent radiation resistance, thereby suppressing the generation of interface states due to radiation exposure and significantly improving the radiation resistance of the semiconductor element. Specifically, it has been confirmed that while conventional Si operational amplifiers (Si op amps) break down at several kGy, SiC operational amplifiers (SiC op amps) can normally perform their amplification function even at the order of MGy.

[0025] As described above, it has become clear that while SiC op amps can significantly reduce the effects of radiation, there is some effect on the offset voltage and output range (especially the upper output limit).

[0026] Regarding the first offset voltage, a fluctuation of several mV occurs when the SiC op-amp is irradiated with radiation from the initial value (0 Gy) to the order of MGy (X Gy in the figure). The output value at the time of the initial radiation exposure is usually the upper limit value An of the linear region. This is due to the effect of fixed charges and interface states formed at the interface between the insulating layer and the semiconductor, but in the case of a SiC op-amp, unlike a Si op-amp, the generation of interface states is extremely small, so the fluctuation is limited to a few mV. With a fluctuation of this magnitude, the output impact on the power supply circuit 10 is within the margin of error, and the impact on the entire circuit is also small.

[0027] On the other hand, with a Si op amp, even if the amount of radiation irradiated is only around 10 kGy, the offset voltage increases to the order of V, making it difficult for a power supply circuit using a Si op amp to operate normally.

[0028] Regarding the second output range, the output range of the SiC op-amp narrows, that is, the maximum output value (upper limit) becomes smaller, due to the effects of factors such as a decrease in throughput caused by the accumulation of fixed charge. This can also be said to mean that the maximum amplification factor of the SiC op-amp decreases. As shown in Figure 3, it was experimentally found that in the SiC op-amp, the maximum output gradually decreases and converges at a certain accumulated dose (XGy in Figure 3). This is thought to be due to the saturation of the fixed charge at the interface (no new accumulation).

[0029] The cumulative dose until convergence varies depending on the structure and manufacturing process of the SiC operational amplifier, but is generally between 10 kGy and 500 kGy. The maximum output value of the SiC operational amplifier at the time of convergence is defined as the upper limit value As of the radiation-induced saturation region. However, the cumulative dose until convergence is not limited to this range. In this embodiment, the operational amplifier 11 is operated within the range of the radiation-induced saturation region where the output characteristic of the operational amplifier 11 remains linear. In other words, the operational amplifier 11 is mounted on the power supply circuit within a range where the output of the operational amplifier 11 is not affected by radiation.

[0030] As described above, the power supply device according to the first embodiment includes a power supply circuit (power supply circuit 10) that has a semiconductor amplifying element made of a semiconductor having a band gap larger than that of silicon and outputs a predetermined voltage. The semiconductor amplifying element is an operational amplifier (operational amplifier 11), and the output of the operational amplifier is set to be equal to or lower than the upper limit of the radiation-induced saturation region. The upper limit of the radiation-induced saturation region is the output value of the operational amplifier at the point in time when degradation of the operational amplifier due to radiation exposure has converged.

[0031] According to the first embodiment having the above configuration, the output of the operational amplifier 11 made of a semiconductor having a larger band gap than silicon is set to be equal to or lower than the upper limit of the radiation-induced saturation region, so that the operational amplifier 11 can output linearly with respect to the input signal (input voltage). Therefore, the power supply circuit 10 can operate without being affected by deterioration of the operational amplifier 11 caused by radiation exposure, and can provide a normal output of the power supply device 1 even in a radiation environment. Furthermore, since there is no need to expose the operational amplifier 11 to radiation in advance, operation is simple and costs can be reduced.

[0032] Although silicon carbide (SiC) is used for the operational amplifier 11 as a semiconductor having a larger band gap than silicon, gallium nitride, diamond semiconductor, or the like may also be used.

[0033] Furthermore, the semiconductor element (transistor) having an amplifying function used in the operational amplifier 11 may be, for example, a semiconductor element having an amplifying function described in Patent Document 1. For example, as described in Patent Document 1, examples of semiconductors having a gate insulating film and a gate electrode include MOS field effect transistors and insulated gate bipolar transistors (IGBTs). Examples of semiconductors having an insulating film and an electrode layer include junction field effect transistors (JFETs) and bipolar transistors without an insulated gate. Examples of semiconductor elements having an electrode layer and an insulating layer include junction field effect transistors (JFETs) and bipolar transistors without an insulated gate.

[0034] <Second embodiment> The second embodiment is an example in which an amplifier circuit is provided on the output side (rear stage) of the operational amplifier 11 in the first embodiment to increase the voltage output from the operational amplifier 11.

[0035] FIG. 4 is a diagram showing an example of the configuration of a power supply device according to the second embodiment of the present invention. The illustrated power supply device 1 includes a power supply circuit 10A. The power supply circuit 10A has the same basic configuration as the power supply circuit 10 of the first embodiment. Furthermore, in the power supply circuit 10A, an amplifier circuit 15 is connected to an output terminal of an operational amplifier 11 via a resistor 17. The amplifier circuit 15 includes a transistor 16 as a semiconductor amplifier element. A current according to the output voltage of the operational amplifier 11 is supplied to the base of the transistor 16 included in the amplifier circuit 15 via the resistor 17. Here, the voltage amplification factor of the amplifier circuit 15 is set to a value greater than 1.

[0036] In the first embodiment described above, when the output voltage of the operational amplifier 11 is reduced to or below the upper limit of the radiation-induced saturation region, there is a trade-off in that while the radiation resistance performance is improved, the upper limit of the output value of the power supply circuit 10 is reduced.

[0037] Therefore, when an instrument (e.g., measuring instrument 30) using power supply circuit 10 requires a high power supply voltage, the performance of power supply device 1 may be insufficient in the first embodiment. For this reason, it is effective to provide amplifier circuit 15 with a voltage amplification factor > 1 on the output side (rear stage) of operational amplifier 11 as in the second embodiment. Resistor 17 is connected between amplifier circuit 15 and the output terminal of operational amplifier 11.

[0038] In the above configuration, a bipolar transistor made of Si, which is relatively resistant to radiation, is preferable as the amplifier circuit 15 provided on the output side (rear stage) of the operational amplifier 11, because it is less expensive. However, the amplifier circuit 15 may be a bipolar transistor made of a semiconductor (e.g., SiC) having a larger band gap than silicon, a MOS field effect transistor such as SiC, or a combination of these. Also, a transistor of another structure using a similar wide band gap semiconductor may be used.

[0039] According to the power supply device (power supply circuit) of the second embodiment configured as described above, as in the first embodiment, the output of the operational amplifier 11 made of a semiconductor having a larger band gap than silicon is set to be equal to or lower than the upper limit of the radiation-induced saturation region, thereby making the operational amplifier 11 less susceptible to radiation degradation. Also, in this embodiment, by providing an amplifier circuit 15 having a voltage amplification factor of greater than 1 on the output side of the operational amplifier 11, it becomes possible to stably provide a normal power supply voltage with a wide output range even in a high radiation environment. Furthermore, since there is no need to irradiate the operational amplifier 11 in advance with radiation, operation is simple and costs are reduced.

[0040] <Third embodiment> The third embodiment is an example of a measuring device incorporating the power supply device 1. Here, the power supply device 1 of the first embodiment will be used for explanation, but the same applies to the power supply device 1 of the second embodiment.

[0041] FIG. 5 is a diagram showing an example of the configuration of a measuring device according to the third embodiment of the present invention. The measuring device 30 shown in the figure includes a measuring unit 31 and a power supply device 1 (power supply circuit 10) having a semiconductor amplifying element. The power supply device 1 outputs a power supply voltage to the measuring unit 31. The measuring unit 31 operates using power supplied from the power supply device 1 and outputs a measurement value.

[0042] In the above configuration, the measuring unit 31 may be any sensor that measures pressure, temperature, flow rate, water level, ultrasonic waves, etc. and uses a sensing method that requires the power output of the power supply circuit 10.

[0043] Furthermore, the sensor used in the measuring unit 31 preferably does not include electronic circuits, is made of analog circuits that are relatively more resistant to radiation than digital circuits, or is made of a wide band gap semiconductor such as SiC that has excellent radiation resistance.

[0044] According to the third embodiment configured as described above, as in the first and second embodiments, the output of the operational amplifier 11 made of a semiconductor having a larger band gap than silicon is set to be equal to or lower than the upper limit of the radiation-induced saturation region, so that the operational amplifier 11 can output linearly with respect to the input signal. Therefore, the power supply circuit can operate without being affected by deterioration of the operational amplifier 11 due to radiation exposure, and a normal output of the power supply device 1 can be provided even in a radiation environment. Therefore, the measuring device 30 using the output of this power supply device 1 can output an accurate measurement value even in a radiation environment. In addition, since there is no need to expose the operational amplifier 11 to radiation in advance, operation is simple and costs can be reduced.

[0045] <Fourth embodiment> The fourth embodiment is an example in which a signal processing unit is provided in a measuring device incorporating the power supply device 1 according to the third embodiment. Here, the power supply device 1 according to the first embodiment will be used for explanation, but the same applies to the power supply device 1 according to the second embodiment.

[0046] FIG. 6 is a diagram showing an example of the configuration of a measuring device according to the fourth embodiment of the present invention. The measuring device 30A shown in the figure includes a measuring unit 31, a signal processing unit 32, and a power supply device 1 (power supply circuit 10) having a semiconductor amplifying element. The power supply device 1 outputs a power supply voltage to the signal processing unit 32. The measuring unit 31 operates using power supplied through the signal processing unit 32, and outputs a measurement value.

[0047] In the above configuration, the signal processing unit 32 is provided to control the measuring unit 31, i.e., to process the output signal of the measuring unit 31. For example, if the measuring unit 31 is a pressure sensor, the measuring unit 31 detects pressure changes of gas or liquid by strain (resistance change) of a pressure-sensitive element, and generates an electric signal based on the amount of strain of the pressure-sensitive element. The signal processing unit 32 converts (signal processes) this electric signal to 4-20 mA or 1-5 V, etc., and outputs it.

[0048] The signal processing unit 32 is composed of an electronic circuit. For example, the signal processing unit 32 is desirably composed of an analog circuit that is relatively more resistant to radiation than a digital circuit, or a wide band gap semiconductor such as SiC that has excellent radiation resistance. Note that the signal processing unit 32 may not include an electronic circuit.

[0049] According to the fourth embodiment configured as described above, as in the first to third embodiments, the output of the operational amplifier 11 made of a semiconductor having a larger band gap than silicon is set to be equal to or lower than the upper limit of the radiation-induced saturation region, so that the operational amplifier 11 can output linearly with respect to the input signal. Therefore, the power supply circuit can operate without being affected by deterioration of the operational amplifier 11 due to radiation exposure, and can provide a normal output of the power supply device 1 even in a radiation environment. Then, the signal processing unit 32 processes the output signal of the measuring unit 31 using the output of the normal power supply device 1, so that the measuring device 30A can output an accurate measurement value. Furthermore, since there is no need to expose the operational amplifier 1 to radiation in advance, operation is simple and costs can be reduced.

[0050] As described above, the power supply device of the present invention can be applied to measuring instruments that measure or monitor the state of an object, assuming use in a radiation environment. For example, the power supply device can be applied to pressure transmitters and image sensors as measuring instruments. Furthermore, the power supply device can be applied to systems and fields such as radiation utilization facilities in nuclear power plants, medical care, and space measurement.

[0051] The present invention is not limited to the above-described embodiments, and various other applications and modifications are possible without departing from the gist of the present invention as described in the claims. For example, the above-described embodiments are detailed and specific descriptions of the configurations of the power supply device and the measuring device in order to explain the present invention in an easy-to-understand manner, and are not necessarily limited to those including all of the components described. In addition, it is also possible to add, replace, or delete other components to a part of the configuration of each embodiment.

[0052] In addition, the above-mentioned configurations, functions, processing units, etc. may be realized in part or in whole by hardware, for example, by designing them as integrated circuits. As the hardware, a broad processor device such as an FPGA (Field Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit) may be used. [Explanation of symbols]

[0053] REFERENCE SIGNS LIST 1...power supply device, 10,10A...power supply circuit, 11...operational amplifier, 12...feedback resistor, 15...amplification circuit, 16...amplification element, 17...resistor, 20...original power supply (external power supply), 30,30A...measuring instrument, 31...measuring section, 32...signal processing section

Claims

1. a power supply circuit including an operational amplifier made of a semiconductor having a band gap larger than that of silicon, a resistor connected to an input terminal of the operational amplifier, and a feedback resistor connected between an output terminal and the input terminal of the operational amplifier, the power supply circuit outputting a predetermined voltage; By adjusting the resistance value of the feedback resistor, the output of the operational amplifier is set to be equal to or lower than the upper limit of a radiation-induced saturation region, and the upper limit of the radiation-induced saturation region is the output value of the operational amplifier at the time when degradation of the operational amplifier due to radiation exposure has converged. power supply.

2. An amplifier circuit having a voltage amplification factor of greater than 1 is provided on the output side of the operational amplifier.

2. The power supply device of claim 1.

3. The amplifier circuit is a bipolar transistor using the silicon, a bipolar transistor using the semiconductor having a band gap larger than that of silicon, a MOS type field effect transistor using the semiconductor, or a combination of these.

3. The power supply device of claim 2.

4. The semiconductor having a band gap larger than that of silicon is silicon carbide.

4. A power supply device according to claim 1.

5. a power supply circuit including an operational amplifier made of a semiconductor having a band gap larger than that of silicon, a resistor connected to an input terminal of the operational amplifier, and a feedback resistor connected between an output terminal and the input terminal of the operational amplifier, the power supply circuit outputting a predetermined voltage; a measurement unit that performs measurement using the predetermined voltage output by the power supply circuit, By adjusting the resistance value of the feedback resistor, the output of the operational amplifier is set to be equal to or lower than the upper limit of a radiation-induced saturation region, and the upper limit of the radiation-induced saturation region is the output value of the operational amplifier at the time when degradation of the operational amplifier due to radiation exposure has converged. Measuring equipment.

6. The measuring unit is a sensor that measures at least one of pressure, temperature, flow rate, water level, and ultrasonic waves.

6. The measuring instrument of claim 5.

7. The measurement unit does not include an electronic circuit, or is configured using an analog circuit or the semiconductor having a larger band gap than silicon.

6. The measuring instrument of claim 5.

8. a signal processing unit for processing an output signal of the measurement unit 6. The measuring instrument of claim 5.

9. The signal processing unit is composed of an electronic circuit, The electronic circuit is an analog circuit or is constructed using the semiconductor having a band gap larger than that of silicon.

9. The measuring instrument of claim 8.

10. The semiconductor having a band gap larger than that of silicon is silicon carbide. A measuring instrument according to any one of claims 5 to 9.

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