Variable Impedance Switching for Dual-Voltage Plasma Matching
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Solution Overview
Problem
Existing impedance adjustment devices in power supply systems fail to maintain zero reflection coefficient when alternately outputting AC voltages of different amplitudes, resulting in persistent reflected waves that reduce efficiency in power supply to loads.
Innovation Solution
An impedance adjustment device with a variable impedance circuit that adjusts its impedance based on calculated average values of reflection coefficients for each AC voltage, switching between target values to minimize reflection coefficients for both AC voltages, using a series of capacitor and switch circuits connected in parallel to efficiently manage impedance changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single target impedance value is used for both AC voltages, then the device complexity is reduced, but the reflection coefficient cannot be minimized for both voltages simultaneously
Solution Approach 1:
The patent applies dynamics by switching the impedance target value dynamically based on which AC voltage is currently output. The control unit selects between a first target impedance value (when first AC voltage is output) and a second target impedance value (when second AC voltage is output), allowing the system to adapt to different voltage conditions and minimize reflection coefficients for both cases.
Solution Approach 2:
The patent changes the impedance parameter based on the output voltage condition. By calculating different target impedance values for different AC voltage amplitudes and switching between them, the system optimizes power transfer efficiency for each voltage condition while managing the complexity of having multiple impedance settings.
2Loss of energy
If impedance adjustment is performed for each AC voltage separately, then the reflection coefficient is minimized, but the switching time between impedance values increases
Solution Approach 1:
The patent applies preliminary action by pre-calculating both target impedance values in advance. The control unit determines the first and second target impedance values before switching is needed, allowing for rapid switching between impedance settings without requiring real-time calculation during voltage transitions, thus minimizing switching time.
3Speed
If a fast calculation circuit is used to calculate target impedance values, then the impedance adjustment speed is improved, but the device complexity and cost increase
Solution Approach 1:
The patent applies this principle by using a simple, low-cost calculation circuit that computes target impedance values. Rather than investing in expensive high-speed calculation hardware, the system uses a basic calculation approach that is sufficient for the application requirements, reducing device complexity and cost while maintaining acceptable performance.
Data Source
AI summary
A high frequency power supply alternately outputs a first AC voltage and a second AC voltage to a plasma generator. The amplitudes of the first AC voltage and the second AC voltage are different from each other. An impedance adjustment device is disposed in midway of the transmission line of the first AC voltage and the second AC voltage. When the AC voltage output from the high frequency power supply is switched to a first AC voltage, a microcomputer changes the capacitance of a variable capacitor circuit to a first target value. When the AC voltage output from the high frequency power supply is switched to a second AC voltage, the microcomputer changes the capacitance of the variable capacitor circuit to a second target value.