Bipolar Pulsed Power Supply Arc Current Control
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Solution Overview
Problem
Bipolar pulsed power supplies face challenges in limiting current increases during arcing, leading to splashes and particles, and preventing overvoltage during polarity reversal, which can induce further arcing in plasma processing applications.
Innovation Solution
A bipolar pulsed power supply with an output characteristics switching circuit that initially provides constant-voltage characteristics and then switches to constant-current characteristics during arcing, using an inductor and additional switching elements to control current rise and prevent overvoltage, while maintaining high durability and reducing switching losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If an inductor of small inductance value is provided to suppress current increase during arcing, then the circuit remains responsive and switching losses are reduced, but the current cannot be suppressed efficiently and overcurrent flows rapidly
Solution Approach 1:
The patent applies dynamics by making the inductance value changeable during operation. The inductor's inductance is dynamically adjusted based on the operating state: during normal operation, a smaller inductance value is used to maintain responsiveness and reduce switching losses; during arcing conditions, the inductance value is increased to effectively suppress current rise. This dynamic adjustment resolves the contradiction between response speed and current suppression efficiency.
2Ease of operation
If the output from DC power supply source has constant-voltage characteristics, then the power supply is simple to control, but at the time of arcing the capacitance rapidly discharges to the output side and current increases rapidly
Solution Approach 1:
The patent transforms the static constant-voltage output into a dynamic output that can switch between constant-voltage and constant-current characteristics. During normal operation, the output maintains constant-voltage characteristics for simple control. When arcing is detected, the output dynamically switches to constant-current characteristics, which naturally limits the rate of current rise during arcing events, thereby resolving the contradiction between control simplicity and arc current suppression.
3Reliability
If an inductor of larger inductance value is provided to limit current increase during arcing, then the current rise is suppressed, but overvoltage occurs at the time of polarity reversal which may induce arcing
Solution Approach 1:
The patent resolves this contradiction by dynamically adjusting the inductance value based on the operational phase. During arcing conditions, a larger inductance value is used to suppress current rise. During polarity reversal, the inductance value is reduced or bypassed to prevent overvoltage induction. This dynamic adjustment allows the system to benefit from current suppression when needed while avoiding the harmful overvoltage effect during polarity reversal.
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
Effectively limits current increases during arcing, suppresses the occurrence of splashes and particles, and prevents overvoltage during polarity reversal, enhancing the stability and efficiency of plasma processing by maintaining a controlled current rise and reducing the risk of arcing.
Implementation Method 1
an inductor which restricts the increase in current at the time of occurrence of arcing
Implementation Method 2
the output and the plasma (load) are coupled together so that the capacitance will rapidly be discharged to the output side
Data Source
AI summary
A bipolar pulsed power supply is provided in which, while effectively restricting the rise in current at the time of arcing which directly leads to the generation of splashes and particles, the occurrence of overvoltage at the time of polarity reversal is prevented. The power supply has a bridge circuit constituted by switching elements SW1 through SW4 connected to positive and negative DC outputs from a DC power supply source. The operation of the switching elements is controlled to output in a bipolar pulsed mode at a predetermined frequency to a pair of electrodes which come into contact with a plasma. There is provided an output-characteristics-switching circuit which switches the output such that, when outputting to the electrodes, the output to the electrodes has initially constant-voltage characteristics and subsequent output to the electrodes has constant-current characteristics.