NMOS-based total radiation dose sensing circuit and photoelectric encoder radiation compensation circuit

Abstract

The present invention proposes a sensing circuit based on the total radiation dose of NMOS and a radiation compensation circuit for a photoelectric encoder. The characteristics of increased NMOS transistor leakage current and less radiation damage to PMOS transistors in a nuclear radiation environment are used to construct a differential amplifier circuit to process the radiation leakage current of NMOS. The output voltage signal can effectively characterize the total dose level of ionizing radiation in a radiation environment. The voltage signal is sampled by an AD sampling chip controlled by an FPGA main control chip, and the main control outputs the total radiation dose information. At the same time, the voltage signal is directly compensated for the power supply current and the op amp input by the PMOS compensation circuit designed by the present invention. Compared with the prior art, it has the advantages of simple structure, high reliability, low power consumption and low cost, and does not require external anti-radiation reinforcement of the circuit.

Description

Technical Field

[0001] The invention relates to the technical field of nuclear radiation safety monitoring, and in particular to an NMOS total radiation dose sensing circuit and a photoelectric encoder radiation compensation circuit. Background Art

[0002] As the nuclear industry gradually matures, nuclear safety issues in nuclear power plants have begun to attract attention, and nuclear emergency rescue equipment and methods have become a hot topic of research. As an efficient and safe nuclear emergency and maintenance tool, nuclear environment operation robots can replace operators to work in radiation environments. The key to nuclear robot research is the radiation damage effect of circuit systems. Electronic components fail due to the total radiation dose effect, which ultimately causes the circuit system to shut down and fail to work. The radiation damage problem of circuit systems needs to be solved urgently.

[0003] The photoelectric encoder is an important circuit system of the robot's articulated arm. Radiation damage will seriously interfere with the robot's operation. Therefore, an efficient total ionizing radiation dose detection circuit and a circuit module that can compensate for the electrical signal of the photoelectric encoder's radiation damage are needed.

[0004] Existing solutions to the total radiation dose effect of circuit systems are mainly divided into three categories: one is to optimize semiconductor materials, use processes to change oxide impurities, oxide layer defects and oxide layer structure, or use different doping concentrations to improve radiation resistance. The second category is the radiation-resistant circuit and layout reinforcement design for integrated circuits. Due to the accumulation of radiation-induced trap charges in the oxide layer, the threshold voltage drifts and edge leakage current occurs. By modifying the circuit and device layout structure, the potential leakage current channel is cut off, and the impact of leakage current is reduced at the circuit design level. The above two types of circuit system radiation-resistant reinforcement design require a lot of resources to invest in research and are extremely costly. The third category is to improve the radiation resistance of the circuit system by performing radiation-resistant circuit reinforcement design. This method has stronger applicability. General circuit design and chip selection are to improve the passive anti-interference ability of the system, and also require circuit modules that can evaluate the current radiation dose and actively compensate for radiation damage. Summary of the invention

[0005] This patent proposes a sensing circuit based on NMOS total radiation dose and a photoelectric encoder radiation compensation circuit, which includes a PMOS bias circuit, an NMOS radiation sensing circuit, a differential amplifier circuit, an AD sampling circuit and an FPGA main control circuit.

[0006] The differential amplifier circuit includes a first operational amplifier, which is used to amplify the voltage value reduced due to radiation damage;

[0007] The PMOS bias circuit comprises a first PMOS transistor and a second PMOS transistor, wherein the drain and the gate of the first PMOS transistor are respectively connected to a high voltage and a low voltage, and the source of the second PMOS transistor is connected to a negative input terminal of the first operational amplifier;

[0008] The NMOS radiation sensing circuit comprises an NMOS tube, the source of which is connected to the positive input terminal of the first operational amplifier, and the NMOS tube is arranged in a nuclear radiation environment to obtain a voltage value of radiation damage;

[0009] The AD sampling circuit is connected to the differential amplifier circuit, samples the differentially amplified voltage value and transmits it to the FPGA main control circuit, and obtains the corresponding total radiation dose value after calculation and conversion.

[0010] Furthermore, the sensing circuit based on the total radiation dose of NMOS and the radiation compensation circuit of the photoelectric encoder further include an adaptive compensation circuit and a power supply circuit, wherein the adaptive compensation circuit includes an adaptive current compensation circuit for compensating the power consumption current required by the power supply circuit when the power consumption current of the chip increases due to the radiation effect;

[0011] The power supply circuit includes an LDO linear regulator;

[0012] The LDO linear regulator is the main power chip of the photoelectric encoder. The input end inputs the filtered external power supply, and the output end can output a stable power supply signal.

[0013] The adaptive current compensation circuit includes a fifth PMOS transistor;

[0014] The fifth PMOS transistor is connected to the differential amplifier circuit to obtain the amplified voltage value, and is also connected to the output end of the LDO linear regulator to output the compensation current.

[0015] Furthermore, the source of the fifth PMOS transistor is connected to the voltage signal after differential amplification, the gate is connected to a low voltage, and the drain is connected to the output end of the LDO chip;

[0016] The amplified voltage value obtained by the fifth PMOS transistor increases as the total radiation dose increases, and the fifth PMOS transistor gradually turns on and outputs a certain current, providing adaptive compensation for the output current of the LDO chip.

[0017] Furthermore, the NMOS total radiation dose based sensing circuit and the photoelectric encoder radiation compensation circuit further include an adaptive compensation circuit and an operational amplifier circuit, wherein the adaptive compensation circuit includes an adaptive voltage compensation circuit;

[0018] The adaptive voltage compensation circuit includes a fourth PMOS transistor, and the operational amplifier circuit includes a second operational amplifier;

[0019] The fourth PMOS transistor is connected to the differential amplifier circuit to obtain the amplified voltage value and input it into the positive input terminal of the second operational amplifier;

[0020] The second operational amplifier amplifies the weak photocurrent of the photoelectric encoder. The gain is reduced in a radiation environment. The compensation current is integrated with the photocurrent generated by the photodiode. The positive input voltage value is linearly increased. The reduction in radiation gain of the second operational amplifier and the increase in the positive input voltage are offset, thereby achieving a compensation effect on the operational amplifier gain.

[0021] Furthermore, the source of the fourth PMOS transistor is connected to a voltage signal representing a total radiation dose, the gate is connected to a low voltage, and the drain is connected to a positive input terminal of the second operational amplifier;

[0022] The positive input terminal of the second operational amplifier is connected to the photocurrent of the photodiode, and the negative input terminal is connected to the differential common mode current. The photocurrent is the current generated by the photodiode receiving the light signal of the grating code disk, and the differential common mode current is the dark current generated by the photodiode when it is not illuminated by light.

[0023] Furthermore, the NMOS tube is a plug-in replaceable structure.

[0024] The beneficial effects achieved by the present invention are:

[0025] The present invention utilizes the characteristics of increased NMOS transistor leakage current and less radiation damage to PMOS transistors in a nuclear radiation environment to construct a differential amplifier circuit to process the radiation leakage current of NMOS, and the output voltage signal can effectively characterize the total dose level of ionizing radiation in the radiation environment. The voltage signal is sampled by an AD sampling chip controlled by an FPGA main control chip, and the main control outputs the total radiation dose information. At the same time, the voltage signal is directly compensated for the power supply current and the op amp input by the PMOS compensation circuit designed by the present invention. Compared with the prior art, it has the advantages of simple structure, high reliability, low power consumption and low cost, and does not require external anti-radiation reinforcement of the circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The circuit connection logic structure block diagram of the present invention is shown;

[0027] Figure 2 The present invention shows a PMOS bias circuit, an NMOS radiation sensing circuit and a differential amplifier circuit;

[0028] Figure 3 The power supply circuit and the adaptive current compensation circuit of the present invention are shown;

[0029] Figure 4The operational amplifier circuit and the adaptive voltage compensation circuit of the present invention are shown. DETAILED DESCRIPTION

[0030] The technical solution of the present invention is described in more detail below in conjunction with the accompanying drawings. The present invention includes but is not limited to the following embodiments.

[0031] As attached Figure 1 As shown, a sensing circuit based on NMOS total radiation dose and a photoelectric encoder radiation compensation circuit provided by the present invention include a PMOS bias circuit, an NMOS radiation sensing circuit, a differential amplifier circuit, an AD sampling circuit, an FPGA main control circuit, an adaptive compensation circuit, a power supply circuit and an operational amplifier circuit.

[0032] The PMOS bias circuit includes two conducting PMOS transistors, and utilizes the strong radiation resistance of the PMOS to provide an original bias voltage for the drain of the NMOS transistor in the NMOS radiation sensing circuit.

[0033] The drain and gate of the first PMOS transistor are connected to a high voltage and a low voltage respectively, so that the PMOS transistor is in an on state to provide a fixed voltage and current to the source. The first PMOS source is connected to the NMOS radiation sensing circuit and then input to the positive input terminal of the operational amplifier of the differential amplifier circuit. The second PMOS source is directly connected to the negative input terminal of the operational amplifier through a resistor.

[0034] The NMOS radiation sensing circuit is composed of an NMOS tube and a resistor. It utilizes the radiation damage characteristics of the NMOS tube in the NMOS transistor radiation sensing array circuit. The interface trap charges and oxide traps generated under nuclear environment radiation cause the leakage current of the NMOS to increase. The increased leakage current will directly affect the voltage of the resistor connected to the drain, thereby reducing the resistor voltage.

[0035] The reduced voltage represents the total radiation damage dose to the NMOS transistor. This voltage value is input to the positive input of the differential amplifier circuit and forms a differential input with the negative input of the PMOS. The difference caused by radiation damage is amplified by the differential amplifier circuit and transmitted to the AD sampling circuit. The AD sampling chip performs sampling operations and transmits it to the FPGA main control chip. After calculation, the accurate cumulative radiation dose value can be obtained.

[0036] Those skilled in the art can select the model of NMOS and design NMOS to be plug-in type to effectively replace the vulnerable device. By modifying the input resistance of the operational amplifier, the total ionizing radiation dose level corresponding to the differential voltage can be conveniently controlled.

[0037] The adaptive compensation circuit is mainly composed of a PMOS transistor and a resistor, and receives a voltage value representing the radiation dose after being amplified by the differential amplifier circuit. This voltage is connected to the drain of the PMOS transistor.

[0038] As the NMOS transistor in the NMOS radiation sensing circuit is damaged by radiation and the leakage current increases, the voltage output by the differential amplifier circuit increases, and the source voltage of the PMOS transistor connected to this voltage increases. As the source voltage increases, the PMOS tube is turned on when the threshold voltage is exceeded, and the turned-on PMOS provides additional current compensation for the next stage. This current compensation is converted into voltage compensation after passing through the resistor, and the compensation value can be corrected by the gate voltage and resistor of the PMOS transistor.

[0039] The AD sampling circuit is mainly composed of an AD sampling chip and a sampling resistor. It can sample the differentially amplified voltage value and transmit it to the FPGA chip, and output the total radiation dose value after calculation and conversion.

[0040] The FPGA main control circuit is composed of an FPGA chip and external circuits such as a crystal oscillator. It interacts with the AD sampling chip and receives the sampled voltage value. After calculation and conversion, the corresponding total radiation dose value is obtained.

[0041] like Figure 2 As shown, taking the photoelectric encoder circuit as an example, the PMOS bias circuit, NMOS radiation sensing circuit and differential amplifier circuit provided by the present invention include the following structures:

[0042] The PMOS transistors Q1 and Q2 provide bias voltage and differential negative input terminal static voltage for the NMOS transistors respectively. The appropriate source and gate voltages are selected according to the specific model of the PMOS. The PMOS is less affected by radiation effects and can provide a reliable bias voltage in a radiation environment.

[0043] The role of NMOS transistor Q3 is to receive radiation damage effects and convert them into leakage current. As the total radiation dose increases, the leakage current is converted into an increase in the voltage of resistor R1 and outputs the voltage signal. Connecting the source of Q3 to the gate and grounding the drain achieves a stable biased on state and can pass the increase in leakage current to the next level;

[0044] Resistors R2, R3, R4, R5, and R6 are used to adjust the voltage and current;

[0045] The operational amplifier U1 amplifies the small voltage increase released by the NMOS transistor, performs signal processing, and transmits it to the next stage.

[0046] like Figure 3As shown, taking an LDO linear voltage regulator chip as an example, the power supply circuit and the adaptive current compensation circuit of the present invention include the following structures:

[0047] The source of the PMOS transistor Q5 is connected to the voltage signal after differential amplification, the gate is connected to a low voltage, and the drain is connected to the output end of the LDO chip. As the total radiation dose increases, the input signal INPUT increases, and Q5 gradually turns on and outputs a certain current, providing adaptive compensation for the output current of the LDO chip.

[0048] LDO linear regulator U3 is the main power chip of the photoelectric encoder. The input terminal IN inputs the filtered external power supply, the output OUT can output a stable power signal, and ADJ is an adjustable port;

[0049] Resistors R11, R12, and R13 provide pull-up and voltage stabilization functions for the system;

[0050] In a radiation environment, the LDO chip is affected by the total radiation dose effect, resulting in output voltage offset and current value drop. In the actual operation of the circuit system, the total radiation dose effect will cause the power consumption current of most chips to increase, so the power supply circuit requires additional gain current to compensate for the power consumption current required by the circuit system. The compensation current of the compensation circuit enters the LDO output channel. This current can solve the problem of the circuit system being overloaded due to the increase in power consumption current in the circuit system in a radiation environment. It effectively improves the working time and working performance of the power supply chip in a radiation environment and improves the overall radiation resistance of the circuit system. The additional power consumption current generated by different circuits in a radiation environment is different. The circuit compensation current requirement can be matched by adjusting the peripheral resistance value of the operational amplifier in the differential amplifier circuit or adding a shunt resistor.

[0051] like Figure 4 As shown, the operational amplifier circuit and the adaptive voltage compensation circuit of the present invention include the following structures:

[0052] The source of the fourth PMOS transistor Q4 is connected to a voltage signal representing the total radiation dose, the gate is connected to a low voltage, and the drain is connected to the positive input terminal of the operational amplifier. The input signal INPUT increases with the increase of the total radiation dose, Q4 gradually turns on and outputs a certain current, the compensation current is integrated with the photocurrent of the photoelectric encoder and then converted into a voltage input to the operational amplifier through the resistor R8;

[0053] The second operational amplifier U2 amplifies the weak photocurrent of the photoelectric encoder. In a radiation environment, the gain is reduced and the amplification factor is weakened. The positive input and negative input of the second operational amplifier U2 are connected to the photocurrent and differential common-mode current of the photodiode respectively. The photocurrent is the current generated by the photodiode receiving the light signal of the grating code disk, and the common-mode current is the dark current generated by the photodiode when it is not illuminated by light. The amplitude of the positive input signal increases after the compensation voltage output by the adaptive compensation circuit, and the resistance calculation and adjustment can achieve balance to maintain effective performance;

[0054] Resistors R7, R8, R9, R10, and R11 provide the circuit with voltage conversion and amplification gain control functions;

[0055] The function of the operational amplifier circuit is to amplify the tiny photosensitive signal of the photoelectric encoder circuit system and perform signal processing on the sine and cosine voltages. Radiation damage to the operational amplifier will cause the gain to decrease, and the output photoelectric encoder signal waveform will be seriously affected. The adaptive compensation circuit inputs the compensation circuit to the positive input port of the operational amplifier chip, and the compensation current is integrated with the photocurrent generated by the photodiode. The negative input port of the operational amplifier is connected to the common-mode dark current of the photodiode and is not connected to the compensation current. The effect is that the positive input voltage value increases linearly, and the reduction in the radiation gain of the operational amplifier is offset by the increase in the positive input voltage, ultimately achieving a compensation effect on the gain of the operational amplifier.

[0056] The present invention utilizes the leakage current of NMOS transistors in radiation environment and the characteristics of PMOS transistors that are not easy to be damaged in radiation environment, and designs a differential amplifier circuit that represents the total radiation dose value. It does not need to consider the radiation resistance selection problem of NMOS transistors and PMOS transistors, and only needs to select the corresponding resistor and transistor chip bias voltage according to the model. As the total radiation dose increases, the voltage value converted by the leakage current increases, and the voltage can be adaptively input into the power supply circuit and the operational amplifier circuit without the need for conversion by the main control chip, effectively reducing the compensation delay and improving the real-time performance, and different conversion resistors can be set according to different use environments to adjust the compensation coefficient.

[0057] The present invention is not limited to the above-mentioned specific implementation modes. A person skilled in the art may implement the present invention in various other specific implementation modes according to the embodiments and the disclosure of the drawings. Therefore, any design that adopts the design structure and concept of the present invention and makes some simple transformations or changes shall fall within the scope of protection of the present invention.

Claims

1. A sensing circuit based on NMOS total radiation dose and a photoelectric encoder radiation compensation circuit, characterized in that: The sensing circuit based on the total radiation dose of NMOS and the radiation compensation circuit of the photoelectric encoder include a PMOS bias circuit, an NMOS radiation sensing circuit, a differential amplifier circuit, an AD sampling circuit and an FPGA main control circuit; The differential amplifier circuit includes a first operational amplifier, which is used to amplify the voltage value reduced due to radiation damage; The PMOS bias circuit comprises a first PMOS transistor and a second PMOS transistor, wherein the drain and the gate of the first PMOS transistor are respectively connected to a high voltage and a low voltage, and the source of the second PMOS transistor is connected to a negative input terminal of the first operational amplifier; The NMOS radiation sensing circuit comprises an NMOS tube, the source of which is connected to the positive input terminal of the first operational amplifier, and the NMOS tube is arranged in a nuclear radiation environment to obtain a voltage value of radiation damage; The AD sampling circuit is connected to the differential amplifier circuit, samples the differentially amplified voltage value and transmits it to the FPGA main control circuit, and obtains the corresponding total radiation dose value after calculation and conversion; The sensing circuit based on the total radiation dose of NMOS and the radiation compensation circuit of the photoelectric encoder include a power supply circuit, an adaptive compensation circuit and an operational amplifier circuit, and the adaptive compensation circuit includes an adaptive current compensation circuit and an adaptive voltage compensation circuit; The power supply circuit includes an LDO linear regulator; The LDO linear regulator is the main power chip of the photoelectric encoder. The input end inputs the filtered external power supply, and the output end can output a stable power supply signal. The adaptive current compensation circuit includes a fifth PMOS transistor; The fifth PMOS transistor is connected to the differential amplifier circuit to obtain the amplified voltage value, and is also connected to the output end of the LDO linear regulator to output the compensation current; The adaptive voltage compensation circuit includes a fourth PMOS transistor, and the operational amplifier circuit includes a second operational amplifier; The fourth PMOS transistor is connected to the differential amplifier circuit to obtain the amplified voltage value and input it into the positive input terminal of the second operational amplifier; The second operational amplifier amplifies the weak photocurrent of the photoelectric encoder, and its gain is reduced in a radiation environment. By integrating the compensation current with the photocurrent generated by the photodiode, the reduction in radiation gain of the second operational amplifier and the increase in the positive input voltage are offset, thereby achieving a compensation effect on the operational amplifier gain.

2. According to claim 1, the NMOS total radiation dose sensing circuit and the photoelectric encoder radiation compensation circuit are characterized in that: The source of the fifth PMOS transistor is connected to the voltage signal after differential amplification, the gate is connected to a low voltage, and the drain is connected to the output end of the LDO chip; The amplified voltage value obtained by the fifth PMOS transistor increases as the total radiation dose increases, and the fifth PMOS transistor gradually turns on and outputs a certain current, providing adaptive compensation for the output current of the LDO chip.

3. The sensing circuit based on NMOS total radiation dose and the photoelectric encoder radiation compensation circuit according to claim 1, characterized in that: The fourth PMOS transistor has a source connected to a voltage signal representing a total radiation dose, a gate connected to a low voltage, and a drain connected to a positive input terminal of the second operational amplifier; The positive input terminal of the second operational amplifier is connected to the photocurrent of the photodiode, and the negative input terminal is connected to the differential common mode current. The photocurrent is the current generated by the photodiode receiving the light signal of the grating code disk, and the differential common mode current is the dark current generated by the photodiode when it is not illuminated by light.

4. The sensing circuit based on NMOS total radiation dose and the photoelectric encoder radiation compensation circuit according to claim 1, characterized in that: The NMOS tube is a plug-in replaceable structure.

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