X-ray Tube Anode Current Control via Grid Feedback
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Solution Overview
Problem
Current cold cathode X-ray tube control systems require calibration and characterization of the anode current versus grid current, which is complex and prone to changes due to degradation, affecting the precision and stability of X-ray radiation.
Innovation Solution
A closed loop control circuit that uses a feedback signal proportional to the anode current to automatically regulate the grid current, eliminating the need for calibration and maintaining precise anode current control by isolating the grid control from the anode-cathode voltage, ensuring consistent X-ray photon emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If calibration and characterization of the anode current versus grid current curve is performed, then the anode current can be controlled, but the system becomes complex and requires periodic recalibration due to tube degradation
Solution Approach 1:
The patent implements a feedback mechanism where the grid current is automatically adjusted based on the measured anode current. The system continuously monitors the anode current and modifies the grid current to maintain the desired anode current level, eliminating the need for manual calibration curves and compensating for tube degradation automatically.
Solution Approach 2:
The control system performs self-calibration and self-adjustment by automatically compensating for tube degradation. The system monitors its own performance and adjusts the grid current accordingly, eliminating the need for external calibration procedures and periodic maintenance recalibrations.
2Reliability
If the grid current is manually controlled using calibration curves, then the anode current can be set, but periodic recalibration is required due to tube degradation
Solution Approach 1:
The feedback loop continuously monitors the anode current and automatically adjusts the grid current to compensate for tube degradation, ensuring stable radiation emission without requiring periodic recalibration and eliminating equipment stoppage time for maintenance.
Solution Approach 2:
The system proactively compensates for tube degradation by continuously adjusting the grid current before significant drift occurs, maintaining reliable radiation emission without requiring periodic intervention or recalibration procedures that would cause equipment stoppage.
3Measurement precision
If the anode current is controlled through grid voltage with exponential relationship, then the anode current can be regulated, but the control becomes very complicated
Solution Approach 1:
The feedback mechanism automatically handles the exponential relationship between grid voltage and anode current by continuously measuring the anode current and adjusting the grid voltage accordingly, simplifying the control process while maintaining precision without requiring complex control circuits.
Solution Approach 2:
The patent replaces complex manual control mechanisms with an automatic feedback-based electronic control system that handles the non-linear exponential relationship through continuous monitoring and adjustment, simplifying the overall control architecture while maintaining precise anode current regulation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution provides precise and stable X-ray radiation throughout the life of the X-ray tube without the need for periodic recalibrations, maintaining optimal precision and reducing equipment stoppage time in radiological applications.
Implementation Method 1
a feedback signal directly proportional to the anode current (IA) is used for the automatic regulation of the grid current (IG)
Implementation Method 2
Between the grid and the cathode, an electric field is applied that is high enough to extract the electrons, which are attracted and accelerated by the anode
Implementation Method 3
The electrons that impact the anode cause X-ray photons to be released that are emitted by the anode with an energy determined by the voltage applied between the anode and the cathode
Data Source
Figure 1
Figure 1a
Figure 2~3
AI summary
A circuit that aims to control directly the anode current of a cold cathode X-ray tube by means of a feedback signal proportional to the current of the anode itself (IA) by means of the automatic regulation of the grid current (IG) of the X-ray tube, the control being carried out by means of a closed loop comprising: - A closed loop control circuit (CLR1) that generates an amplified error signal (SMOD) that is the amplified difference between the signal proportional to the anode current (IA) and the demanded current of the anode (IDEM) - A Digital Sequencer circuit that converts the received signal into several digital control signals, - A grid current control circuit that receives the digital control signals from the Digital Sequencer circuit and comprises at least one set formed by an inverter (INV) and optionally a converter (DC-DC CONV) and - A voltage and current adapter transformer (TR), whose rectified output supplies the grid intensity (IG) necessary to obtain the requested anode intensity (IA). It avoids having to calibrate and/or characterize the curve of the anode current (IA) versus the grid current (IG), keeping the X-ray tube in perfect condition throughout its useful life.