Variable Capacitor Switching for Stable Plasma Impedance Matching
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Solution Overview
Problem
Conventional impedance adjustment devices face instability issues when changing capacitance values, leading to excessive deviations from target values, which can result in unstable load states and inefficient impedance matching.
Innovation Solution
The impedance adjustment device employs a variable capacitor unit with a changing unit that adjusts capacitance values through a relay capacitance value, allowing for sequential switching of semiconductor switches across multiple groups to minimize excess capacitance and maintain stable load states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If multiple semiconductor switches are switched on or off simultaneously to change capacitance value, then the capacitance value can be changed quickly, but the capacitance value may exceed the target value causing load state instability
Solution Approach 1:
The plurality of semiconductor switches are divided into multiple groups, and switching operations are performed sequentially for each group rather than simultaneously. This segmentation of the switching process allows control over the capacitance change trajectory, preventing excessive deviation from the target capacitance value while maintaining relatively fast overall switching speed.
Solution Approach 2:
The switching operations are performed in a predetermined sequence that has been designed in advance to minimize capacitance value overshoot. By planning the switching sequence beforehand, the system ensures that capacitance values transition smoothly toward the target value without excessive oscillation or deviation, thereby maintaining load state stability.
2Manufacturing precision
If semiconductor switches are switched sequentially in multiple groups, then the capacitance value stays close to the target value, but the switching time increases
Solution Approach 1:
The switching sequence is optimized to perform only the necessary switching operations in each group to achieve the target capacitance value efficiently. By carefully selecting which switches to operate in each group and in what order, the system achieves precise capacitance control without unnecessary delays, balancing precision with time efficiency.
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 approach effectively reduces the amount of excess capacitance, preventing the load state from becoming unstable and ensuring efficient impedance matching by gradually adjusting capacitance values to the target, thereby minimizing reflection coefficient changes.
Implementation Method 1
The capacitance value of the variable capacitor unit is changed by switching on or off separately a plurality of semiconductor switches included in the variable capacitor unit
Implementation Method 2
When the semiconductor switch is ON, the impedance of the semiconductor switch is very low. When the semiconductor switch is OFF, the impedance of the semiconductor switch is very high
Data Source
AI summary
An impedance adjustment device includes a variable capacitor unit. A microcomputer changes the capacitance value of the variable capacitor unit by switching on or off PIN diodes included in n capacitor circuits separately. Thus, the impedance on the plasma generator side when viewed from a high frequency power supply is adjusted. When changing the capacitance value of the variable capacitor unit to a target capacitance value, the microcomputer changes the capacitance value to a relay capacitance value different from the target capacitance value. The microcomputer changes the capacitance value to the target capacitance value after the capacitance value is changed to the relay capacitance value.