Plasma Power Supply Pulse Control for Impedance Fluctuation
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Solution Overview
Problem
Conventional high frequency power supply devices for plasma generation struggle to maintain constant output power due to fluctuations in the impedance of the plasma load during the on-state of the modulation pulse, leading to deviations from the set power value.
Innovation Solution
A power supply device using a pulse modulation system with an oscillation unit, modulation unit, level adjustment unit, power amplifier, output power detection unit, and a control unit that stores elapsed times and correction factors to adjust the level of the pulsed high frequency signal, ensuring the output power remains within the set value by correcting the level control signal based on detected output power values and set power values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional high frequency power supply devices are used for plasma generation, then the device can supply pulsed high frequency power to the plasma load, but the output power fluctuates due to impedance changes of the plasma load during the on-state of the modulation pulse
Solution Approach 1:
The patent implements a feedback control mechanism where the control unit continuously monitors the actual output power through the output power detection unit and compares it with the set power value. Based on the difference, the control unit adjusts the level adjustment circuit to compensate for power fluctuations caused by plasma load impedance changes, thereby maintaining stable output power throughout the pulse on-state.
Solution Approach 2:
The patent introduces dynamic correction by dividing the pulse on-state into multiple elapsed times and applying different correction factors to each time interval. The control unit dynamically adjusts the level control signal based on the current elapsed time and corresponding correction factor, allowing the system to adapt to changing plasma load conditions in real-time during the pulse duration.
2Stability of the object's composition
If the level adjustment circuit is controlled to maintain constant output power, then the output power remains stable, but the device complexity increases due to additional control mechanisms
Solution Approach 1:
The patent employs preliminary action by pre-storing correction factors in the storage unit before the actual power supply operation. These correction factors are prepared in advance for different elapsed times, allowing the control unit to quickly retrieve and apply appropriate corrections without complex real-time calculations, thus reducing the computational complexity of the control system.
Solution Approach 2:
The patent manages complexity by changing the control parameter from continuous real-time adjustment to discrete elapsed-time-based adjustment. The control unit switches between different correction factors based on the current elapsed time, transforming the complex continuous control problem into a simpler discrete parameter selection problem, thereby reducing the overall control system complexity.
Data Source
AI summary
A power supply device includes: an oscillation unit for outputting a high frequency signal; a modulation unit for outputting a pulsed high frequency signal; a level adjustment unit for adjusting and outputting a level of the pulsed high frequency signal; a power amplifier for amplifying a power outputted from the level adjustment unit; an output power detection unit for detecting an output power value from the power amplifier; and a control unit. The control unit corrects and outputs a level control signal for controlling the level of the pulsed high frequency signal based on a corresponding correction factor at each of elapsed times in an on state of the pulsed high frequency signal, and compares comparison values in a current pulse and a previous pulse to update the correction factor such that comparison result between the set power value and the output power value becomes smaller at each reflection coefficient.