Digital control system of cold cathode ray machine based on high frequency inverter and pulse modulation

Abstract

The application relates to the technical field of ray detection, and particularly discloses a cold cathode ray machine digital control system based on high-frequency inversion and pulse modulation, which specifically comprises a master control module and a calculation module, a high-frequency high-voltage inversion and modulation module, a pulse driving and field emission control module, a precision sensing and acquisition module, a safety interlocking and state monitoring module, and a man-machine interface and communication module. The application first proposes a closed-loop control scheme of high-frequency inversion, pulse modulation and cathode state, solves the problem of the independent operation of traditional system power supply, control and emitter, and realizes cross-module collaborative optimization.

Description

Technical Field

[0001] This invention relates to the field of X-ray detection technology, and more particularly to a control system for portable X-ray detection equipment, specifically a digital control system for a cold cathode X-ray machine based on high-frequency inverter and pulse modulation. Background Technology

[0002] Traditional portable cold cathode X-ray machines typically employ silicon-based IGBTs or MOSFETs in their high-voltage power supplies, using power frequency or intermediate frequency inverter topologies. Limited by the switching losses and frequency characteristics of semiconductor devices, their operating frequencies are usually below 50kHz, resulting in bulky transformers and filter components, and power density that struggles to exceed 1kW / kg, severely restricting the equipment's lightweight and portability. Furthermore, existing control systems largely rely on analog circuits or fixed-parameter digital PWM regulation, offering narrow adjustment ranges for pulse width and repetition frequency, and lacking adaptability to the cold cathode field emission characteristics. This rigid control mode leads to three core defects: first, transient instability in cathode electron emission causes X-ray dose rate drift, resulting in image grayscale distortion; second, thermal diffusion of the electron beam focus under wide-pulse operation limits spatial resolution to below 3LP / mm, failing to meet the requirements for detecting fine structures; and third, cathode lifespan is significantly shortened due to continuous overcurrent impacts. In addition, the high-voltage closed-loop response delay of existing power supply topologies exceeds 100μs, making pulse-level real-time control impossible, further exacerbating the uncontrollability of output energy. Although recent research has attempted to introduce digital control chips, the algorithms used have only achieved open-loop pulse width modulation, failing to establish a multi-parameter collaborative mechanism with cathode state and dose feedback, and further failing to resolve the core contradiction of deep integration between high-frequency and digital technologies. Therefore, there is an urgent need for a control system that integrates wide-bandgap semiconductor high-frequency inverter technology with intelligent adaptive pulse modulation, breaking through the technical bottlenecks of power density, resolution, and reliability through topological innovation and algorithmic synergy. Summary of the Invention

[0003] To address the challenge of deep integration of high-frequency and digital technologies in existing portable X-ray inspection devices, this application provides a digital control system for a cold cathode X-ray machine based on high-frequency inverter and pulse modulation. The system features revolutionary technological innovations primarily in intelligent pulse modulation and control, and in high-frequency, digital, and semiconductor-based high-voltage power supplies, as detailed below:

[0004] First, in terms of intelligent pulse modulation and control, an algorithm was developed to adjust the pulse frequency, width, and amplitude in real time based on the target material thickness and density, solving the problem of dynamic pulse parameter adjustment. Second, by acquiring dose feedback in real time and controlling the pulse output in a closed loop, the precise and constant dose for each exposure is ensured, unaffected by power supply fluctuations or temperature, thus solving the problem of adaptive dose control. Furthermore, this invention employs wide-bandgap semiconductor devices such as GaN / SiC to achieve a high-voltage power supply with a switching frequency in the MHz range. This significantly reduces the size and weight of transformers and filter components, improving power density and response speed. A high-speed digital signal processor is used to achieve precise closed-loop control of the high voltage, improving stability and anti-interference capabilities, and facilitating remote parameter configuration and updates.

[0005] To achieve the above objectives, the technical solution adopted in this application is as follows:

[0006] This invention provides a digital control system for a cold cathode ray machine based on high-frequency inverter and pulse modulation, specifically including:

[0007] The main control and computing module is used to receive instructions from the human-machine interface and communication module and receive real-time data from the precision sensing and acquisition module and the safety interlock and status monitoring module. Specifically, it includes an MPU main processor for adaptive pulse parameter calculation, dose management, user interface, communication protocol stack management and data recording, a real-time coprocessor FPGA connected to the MPU main processor via a high-speed bus shared memory for executing millisecond / microsecond level real-time closed-loop control algorithms, pulse parameter calculation and safety logic processing, as well as high-speed memory RAM, non-volatile storage and precision clock source;

[0008] The high-frequency high-voltage inverter and modulation module includes a digital controller for receiving instructions from the main control and computing module and generating PWM / pulse control signals, a wide-bandgap semiconductor driver providing isolation protection, a wide-bandgap semiconductor power stage module for core power conversion, a high-frequency power transformer for boosting high-frequency, high-efficiency, and high-insulation-voltage signals, and a module for sampling the anode high voltage. Reduced proportionally to the low-pressure measurable range A multi-stage sampling resonant network module that performs filtering;

[0009] The pulse drive and field emission control module is used to provide high voltage for field emission to the cathode and anode of the X-ray machine. Specifically, it includes a module for receiving high-voltage pulses output from the high-frequency high-voltage inverter and modulation module. It also includes a pulse interface and logic unit for logic on / off control, providing precise and fast-response gate voltage. Or extract pressure The gate / extraction electrode control circuit for the cold cathode provides the DC bias potential of the cathode and the local feedback signal for stabilizing field emission. The cathode bias and stabilization circuit is used to measure the cathode emission current. The emission current sampling circuit and the instructions from the main control and computing module control the gate / extraction electrode drive circuit, and read the cathode emission current. A microcontroller logic unit that calculates launch stability indicators and communicates with the main control and computing modules in real time.

[0010] Precision sensing and acquisition module, including anode high voltage Drop to low pressure The high voltage divider, as well as the emission current sensor, dose rate sensor interface, temperature sensor interface, high-speed analog-to-digital converter, and signal conditioning and isolation;

[0011] The safety interlock and status monitoring module includes a safety logic controller that is connected to the precision sensing and acquisition module and executes hard safety logic independent of the main control and computing module based on the acquired information.

[0012] The human-machine interface and communication module includes a main processor interface for connecting to the main control and computing module, a wireless communication unit, a display unit, an input unit, a cloud platform interface, and an audio output interface.

[0013] Preferably, the adaptive pulse parameters , , The algorithm used for the calculation is as follows:

[0014]

[0015] in, The pulse amplitude set voltage value calculated in the kth control cycle is represented by V; This represents the desired transmit current value. This represents the average emission current measured during the kth control cycle, in amperes (A). , Represents proportional and integral gain; ∑ represents the control cycle time, in seconds; ∑ represents the integral of the error from the start to the current cycle k.

[0016]

[0017]

[0018] in, The duration of a single high-voltage pulse, measured in microseconds (µs) or nanoseconds (ns). It is the pulse width calibration coefficient, which is determined by the cathode characteristics; is the system reference resolution, is the actual required resolution, with the unit of LP / mm;

[0019] represents the repetition frequency of the pulse sequence, with the unit of Hz or kHz; is the frequency scaling factor, determined by the response speed of the high-voltage power supply, is the equivalent attenuation coefficient of the target material; is the equivalent attenuation coefficient of the detected material.

[0020] Preferably, the dose management adopts integral calculation to accumulate the dose and compares it with the target dose and then controls the exposure time or adjusts the pulse parameters to reach the target dose. The cumulative dose is calculated by integral as follows:

[0021]

[0022] is the feedback dose rate, unit: Gy / s.

[0023] Preferably, the multi-stage sampling resonant network module in the high-frequency high-voltage inversion and modulation module uses an LLC resonant converter to output voltage and is obtained by calculating through the following formula:

[0024]

[0025] is the output DC bus voltage, is the input DC voltage, unit: V; N represents the turns ratio of the transformer secondary / primary; M is the voltage gain, related to the switching frequency; Q is the quality factor; ; is the normalized frequency, ; is the resonant frequency,<00001​​​​​​​​​​​​​​​​​​

[0029]

[0030] in, This represents the duty cycle setting for the k-th cycle; This is the anode voltage feedback in the kth cycle, in V. , These represent the voltage loop proportional gain and integral gain, respectively. Represents the control period, in seconds (s).

[0031] Preferably, the gate / extraction electrode control circuit in the pulse drive and field emission control module controls the field emission current density. J The equation is as follows:

[0032]

[0033] in, J Represents the emission current density, unit: A / m 2 A represents the effective emission area constant, in A·m. -2 ·V -2 ; The field enhancement factor is represented by E, which represents the applied electric field strength, in V / m.

[0034] Beneficial effects:

[0035] 1. This invention proposes for the first time a closed-loop control scheme of "high-frequency inverter, pulse modulation and cathode state", which solves the problem of the separation of power supply, control and transmitter independent operation in traditional systems and realizes cross-module collaborative optimization.

[0036] 2. This invention optimizes the algorithm to reduce the corresponding delay from the traditional 100µs level to below 5µs, significantly speeding up the process and enabling pulse-level real-time control. At the same time, it also significantly improves the accuracy of current and voltage adjustment, enabling precise and stable dose output.

[0037] 3. Based on precise control of current, voltage, and dosage, this invention can further improve spatial and temporal resolution, further reduce the smallest detectable defect, and improve dynamic imaging capability from traditional static to real-time imaging. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 This is a system principle block diagram of the present invention. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0041] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0042] Example 1:

[0043] This invention provides a digital control system for a cold cathode ray machine based on high-frequency inverter and pulse modulation, specifically including:

[0044] The Master Control & Computation Module (MCC), referred to as such in the embodiments for ease of description and to avoid excessive length, is used to receive real-time instructions from the human-machine interface and communication module, as well as real-time data from the precision sensing and acquisition module and the safety interlocking and status monitoring module. Specifically, it includes an MPU main processor for adaptive pulse parameter calculation, dose management, user interface, communication protocol stack management, and data recording. This embodiment employs a high-performance multi-core ARM Cortex-A or RISC-VSoC running Linux or RTOS. It also includes a real-time coprocessor FPGA connected to the MPU main processor via a high-speed bus shared memory for executing millisecond / microsecond-level real-time closed-loop control algorithms, pulse parameter calculations, and safety logic processing. Although the real-time coprocessor FPGA is not the main processor MPU, its role is irreplaceable; it is the core of the entire system's information processing. Hardware-wise, it uses a high-speed FPGA or a real-time MCU with FPU / DSP, such as a Cortex-M7 / M4, to execute millisecond / microsecond-level real-time closed-loop control algorithms, pulse parameter calculations, and safety logic processing. It communicates with the MPU via a high-speed bus, such as PCIe or AXI, and shares memory. High-speed RAM, using traditional DDR3 / 4, and non-volatile storage using eMMC or pluggable SD cards, are used to store system configuration, calibration data, algorithm models, and operation logs. It also provides a precise clock source for system synchronization. Because this system is highly integrated, to facilitate understanding by those skilled in the art and to provide a more in-depth explanation of the invention, this embodiment will focus on functional modules as units, explaining their working principles and their roles in the overall system for better comprehension. From the perspective of the overall system's function, the MCC acts as the central brain, receiving HCI commands and real-time data from PSA / SISM. It undertakes a large amount of core computation, mainly including calculations based on the target dose. Target imaging characteristics, such as material attenuation coefficient or penetration power. Resolution Real-time feedback , Dynamic calculation of optimal pulse parameters , , It also includes providing setting values ​​to HFHI. and based on Perform closed-loop regulation and calculate the cumulative dose through integration. and target dose In contrast, exposure time can be controlled or pulse parameters adjusted to achieve the target dose.

[0045] The High-Frequency High-Voltage Inverter & Modulation Module (HFHI, referred to as HFHI in the embodiments section) includes a digital controller (DCtrl) for receiving instructions from the main control and computing module and generating PWM / pulse control signals. This digital controller is a dedicated high-voltage control ASIC or high-speed MCU / FPGA that works closely with the FPGA of the MCC. It receives instructions from the MCC, including... , , , This is used to generate PWM / pulse control signals.

[0046] A wide-bandgap semiconductor driver (WGD) providing isolation protection is used in this embodiment, employing a high-speed, high-drive-capability SiCMOSFET or GaNHEMT gate driver. A wide-bandgap semiconductor power stage module (WGP) performing core power conversion is implemented using a full-bridge, half-bridge, or LLC resonant inverter topology based on SiCMOSFET or GaNHEMT. A high-frequency power transformer (HFT) for boosting high-frequency, high-efficiency, and high-insulation-voltage voltage is used, employing low-loss magnetic cores such as nanocrystalline, ferrite, and Litz wire wound cores; and a high-voltage anode is used for sampling. Reduced proportionally to the low-pressure measurable range The multi-stage sampling resonant network module, which performs filtering, specifically includes a filter using an LLC resonant topology / high-frequency rectifier filter circuit, a high-voltage sampling unit, and a primary current sampling unit; the high-voltage sampling unit uses a precision high-voltage divider resistor network to sample the anode high voltage. Reduced proportionally to the low-pressure measurable range The primary current sampling unit uses a combination of a current transformer (CT) or a low-inductance sampling resistor and an isolation amplifier to measure the primary current of the inverter. The main functions and working principle of HFHI include high-frequency inversion, rectification and filtering / resonant conversion, pulse modulation, and high-voltage closed-loop control; among them, the high-frequency inversion process is performed by DCtrl based on the target output voltage. The pulse parameters are used to generate a high-frequency PWM signal. WGD drives the WGP switch, and HFT boosts the primary low-voltage high-frequency AC to the secondary high-voltage high-frequency AC. The rectification and filtering / resonant conversion process involves the secondary high voltage being rectified and filtered, or directly obtaining a stable high voltage through a resonant network. The pulse modulation process involves DCtrl controlling the switching timing of WGP to modulate the stable high voltage to meet the requirements. , , Required high voltage pulse Sequence. For example, amplitude modulation is achieved by changing the PWM duty cycle or phase shift angle, and pulse width and frequency are controlled by switching timing. The high-voltage closed-loop control process includes reading via DCtrl. (represent = * ) and with By comparing and adjusting PWM parameters in real time, such as duty cycle D, switching frequency, or phase shift angle, the output voltage can be stabilized.

[0047] The Field Emission Driver & Control Module (FDEC), used in the embodiments section, provides high voltage for field emission to the cathode and anode of the X-ray machine. Specifically, it includes a module for receiving high-voltage pulses output from the high-frequency high-voltage inverter and modulation module. The pulse interface and logic unit (PIL) for logic on / off control provides precise and fast-response gate voltage. Or extract pressure The gate / extraction electrode control circuit for the cold cathode, abbreviated as GDC / EDC, provides the DC bias potential of the cathode and the local feedback signal for stabilizing field emission. The cathode bias and stabilization circuit, abbreviated as CBS, is used to measure the cathode emission current. The emission current sampling circuit and the instructions from the main control and computing module control the gate / extraction electrode drive circuit, and read the cathode emission current. The microcontroller logic unit (μCL) calculates launch stability parameters and communicates with the main control and computing modules in real time. Its working principle is briefly described as follows: High-voltage pulse application: The high-voltage pulse... Safe and precise application to the cold cathode structure (typically, the cathode is at a negative high voltage relative to the gate / anode). Gate / extraction electrode control: based on fine-tuning instructions from the MCC. Fine adjustment or This optimizes the electric field distribution and controls the emission current density and focal spot size. Emission current monitoring: High-precision, high-speed measurement of the cathode emission current for each pulse. Waveform, including amplitude, rise / fall time, and stability. Emission stability assessment: μCL real-time analysis of cathode emission current. If the waveform exceeds the system threshold, an alarm is set for the MCC. Rapid shutdown: The high-voltage pulse can be quickly cut off upon detecting unstable transmission or receiving a safety command. The path to the cathode or the clamping gate voltage.

[0048] The Precision Sensing & Acquisition Module (PSA), as used in the implementation section, includes the anode high voltage... Drop to low pressure The high-voltage divider, emission current sensor, dose rate sensor interface, temperature sensor interface, high-speed analog-to-digital converter, and signal conditioning and isolation are included. This part of the embodiment utilizes existing technology and mainly performs signal conversion: converting various physical quantities (high voltage, current, dose rate, temperature) into analog electrical signals through sensors. Precision conditioning: amplifying, filtering, and linearizing weak or high common-mode signals to make them conform to the ADC input range. Electrical isolation: providing safe isolation between the high-voltage / power section and the low-voltage digital control section to prevent ground loop interference and high-voltage intrusion. High-speed synchronous acquisition: the ADC synchronously digitizes all sensor signals at a high sampling rate under precise clock control; data transmission: transmitting the digitized data stream to the MCC in real time through a high-speed interface.

[0049] The Safety Interlock & Status Monitoring Module (SISM) is a security logic controller connected to the precision sensing and acquisition module. It executes hard safety logic independent of the main control and computing modules based on the acquired information. Specifically, the security logic controller includes a high-reliability PLC, a safety MCU, or dedicated safety relay logic, executing hard safety logic independent of the MCC. Safety input interfaces connect to all safety-related sensors: door interlock switches, emergency stop buttons, vacuum sensor relay outputs, over-temperature sensors, and dose accumulation over-limit signals. Safety output interfaces drive safety relays, contactors, and audible / visual alarms. A hardware watchdog monitors the operating status of the MCC and SLC, triggering a reset or safety shutdown if there is no response within a timeout period. A health monitoring sensor interface connects to vibration sensors and more precise temperature / humidity sensors. This part is merely a functional integration and does not involve algorithmic innovation; its working principle is not substantially different from existing technologies and will not be elaborated upon here.

[0050] The Human-Computer Interface & Communication Module (HCI, referred to as HCI in the implementation section) includes a main processor interface for connecting to the main control and computing modules, a wireless communication unit, a display unit, an input unit, a cloud platform interface, and an audio output interface. This part is also a functional integration; it does not involve any innovation in algorithms or structure, and its working principle is not substantially different from existing technologies, so it will not be elaborated upon here.

[0051] Example 2:

[0052] This embodiment provides a specific optimization algorithm based on Embodiment 1. It mainly includes the technical content that makes new and innovative contributions to the prior art in solving the problems of adaptability, high precision, and fast response. Specifically, it includes the adaptive pulse parameters. , , The algorithm used for the calculation is as follows:

[0053]

[0054] in, The pulse amplitude set voltage value calculated in the kth control cycle is represented by V; This represents the desired transmit current value. This represents the average emission current measured during the kth control cycle, in amperes (A). , Represents proportional and integral gain; ∑ represents the control cycle time, in seconds; ∑ represents the integral of the error from the start to the current cycle k.

[0055]

[0056]

[0057] in, The duration of a single high-voltage pulse, measured in microseconds (µs) or nanoseconds (ns). It is the pulse width calibration coefficient, which is determined by the cathode characteristics; It is the system's baseline resolution. This refers to the actual required resolution, expressed in LP / mm.

[0058] Represents the repetition frequency of a pulse sequence, measured in Hz or kHz; It is a frequency scaling factor, determined by the response speed of the high-voltage power supply. It is the equivalent attenuation coefficient of the target material; It is the equivalent attenuation coefficient of the tested material.

[0059] In this embodiment, the dose management uses integral calculation of cumulative dose. and target dose The cumulative dose is then compared and controlled by adjusting the exposure time or pulse parameters to achieve the target dose. The integral is calculated as follows:

[0060]

[0061] is the feedback dose rate, unit: Gy / s.

[0062] Preferably, the multi-stage sampling resonant network module in the high-frequency high-voltage inversion and modulation module uses an LLC resonant converter to output voltage obtained by calculating through the following formula:

[0063]

[0064] is the output DC bus voltage, is the input DC voltage, unit: V; N represents the transformer secondary / primary turn ratio; M is the voltage gain, related to the switching frequency; Q is the quality factor; ; is the normalized frequency, ; is the resonant frequency, .

[0065] In this embodiment, the multi-stage sampling resonant network module in the high-frequency high-voltage inversion and modulation module uses a PWM duty cycle control model to calculate the output voltage :

[0066]

[0067] Among them, is the topology factor, when it is a full-bridge structure , N is the transformer secondary / primary turn ratio; represents the PWM signal duty cycle and satisfies 0 < D < 1; the digital PI control algorithm is as follows:

[0068]

[0069] Among them, represents the duty cycle setting in the k-th cycle; is the anode voltage feedback in the k-th cycle, unit: V; , respectively represent the voltage loop proportional and integral gains; represents the control cycle, unit: s.

[0070] In this embodiment, the gate / extraction electrode control circuit in the pulse drive and field emission control module controls the field emission current density J The equation of is as follows:

[0071]

[0072] Among them, J represents the emission current density, unit: A / m2 A represents the effective emission area constant, in A·m. -2 ·V -2 ; The field enhancement factor is represented by E, which represents the applied electric field strength, in V / m.

[0073] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A digital control system for a cold cathode ray machine based on high-frequency inverter and pulse modulation, characterized in that: include: The main control and computing module is used to receive instructions from the human-machine interface and communication module and receive real-time data from the precision sensing and acquisition module and the safety interlock and status monitoring module. Specifically, it includes an MPU main processor for adaptive pulse parameter calculation, dose management, user interface, communication protocol stack management and data recording, a real-time coprocessor FPGA connected to the MPU main processor via a high-speed bus shared memory for executing millisecond / microsecond level real-time closed-loop control algorithms, pulse parameter calculation and safety logic processing, as well as high-speed memory RAM, non-volatile storage and precision clock source; The high-frequency high-voltage inverter and modulation module includes a digital controller for receiving instructions from the main control and computing module and generating PWM / pulse control signals, a wide-bandgap semiconductor driver providing isolation protection, a wide-bandgap semiconductor power stage module for core power conversion, a high-frequency power transformer for boosting high-frequency, high-efficiency, and high-insulation-voltage signals, and a module for sampling the anode high voltage. Reduced proportionally to the low-pressure measurable range A multi-stage sampling resonant network module that performs filtering; The pulse drive and field emission control module is used to provide high voltage for field emission to the cathode and anode of the X-ray machine. Specifically, it includes a module for receiving high-voltage pulses output from the high-frequency high-voltage inverter and modulation module. It also includes a pulse interface and logic unit for logic on / off control, providing precise and fast-response gate voltage. Or extract pressure The gate / extraction electrode control circuit for the cold cathode provides the DC bias potential of the cathode and the local feedback signal for stabilizing field emission. The cathode bias and stabilization circuit is used to measure the cathode emission current. The emission current sampling circuit and the instructions from the main control and computing module control the gate / extraction electrode drive circuit, and read the cathode emission current. A microcontroller logic unit that calculates launch stability indicators and communicates with the main control and computing modules in real time. Precision sensing and acquisition module, including anode high voltage Drop to low pressure The high voltage divider, as well as the emission current sensor, dose rate sensor interface, temperature sensor interface, high-speed analog-to-digital converter, and signal conditioning and isolation; The safety interlock and status monitoring module includes a safety logic controller that is connected to the precision sensing and acquisition module and executes hard safety logic independent of the main control and computing module based on the acquired information.

2. Human-machine interface and communication module, including a main processor interface for connecting to the main control and computing module, a wireless communication unit, a display unit, an input unit, a cloud platform interface, and an audio output interface.

3. The digital control system for a cold cathode ray machine based on high-frequency inverter and pulse modulation according to claim 1, characterized in that: The adaptive pulse parameters , , The algorithm used for the calculation is as follows: in, The pulse amplitude set voltage value calculated in the kth control cycle is represented by V; This represents the desired transmit current value. This represents the average emission current measured during the kth control cycle, in amperes (A). , Represents proportional and integral gain; ∑ represents the control cycle time, in seconds; ∑ represents the integral of the error from the start to the current cycle k. in, The duration of a single high-voltage pulse, measured in microseconds (µs) or nanoseconds (ns). It is the pulse width calibration coefficient, which is determined by the cathode characteristics; It is the system's baseline resolution. This refers to the actual required resolution, expressed in LP / mm. Represents the repetition frequency of a pulse sequence, measured in Hz or kHz; It is a frequency scaling factor, determined by the response speed of the high-voltage power supply. It is the equivalent attenuation coefficient of the target material; It is the equivalent attenuation coefficient of the tested material.

4. The digital control system for a cold cathode ray machine based on high-frequency inverter and pulse modulation according to claim 1, characterized in that: The dose management uses an integral calculation to accumulate the dose. and target dose The cumulative dose is then compared and controlled by adjusting the exposure time or pulse parameters to achieve the target dose. The integral is calculated as follows: It is the feedback dose rate, in Gy / s.

5. The digital control system for a cold cathode ray machine based on high-frequency inverter and pulse modulation according to claim 1, characterized in that: The multi-stage sampling resonant network module in the high-frequency high-voltage inverter and modulation module uses an LLC resonant converter to output voltage. It is obtained by calculation using the following formula: It is the output DC bus voltage. It is the input DC voltage, in volts (V). N represents the secondary to primary turns ratio of the transformer; M is the voltage gain, which is related to the switching frequency; Q is the quality factor. ; It is the normalized frequency. ; It is the resonant frequency. .

6. The digital control system for a cold cathode ray machine based on high-frequency inverter and pulse modulation according to claim 1, characterized in that: The multi-stage sampling resonant network module in the high-frequency high-voltage inverter and modulation module uses a PWM duty cycle control model to calculate the output voltage. : in, As the topology factor, in a full-bridge structure N is the secondary / primary turns ratio of the transformer; The signal represents the duty cycle of the PWM signal and satisfies 0 < D < 1; the digital PI control algorithm is as follows: in, This represents the duty cycle setting for the k-th cycle; This is the anode voltage feedback in the kth cycle, in V. , These represent the voltage loop proportional gain and integral gain, respectively. Represents the control period, in seconds (s).

7. The digital control system for a cold cathode ray machine based on high-frequency inverter and pulse modulation according to claim 1, characterized in that: The gate / extractor control circuit in the pulse drive and field emission control module controls the field emission current density. J The equation is as follows: in, J Represents the emission current density, unit: A / m 2 A represents the effective emission area constant, in A·m. -2 ·V -2 ; The field enhancement factor is represented by E, which represents the applied electric field strength, in V / m.

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