Piezoelectric Actuator Drive Circuit for Fast Mass Flow Control
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Solution Overview
Problem
Current mass flow controller devices have slow actuation times due to peak current stresses on internal bond wires and high-current switch limitations, leading to inefficient control over gas flow in high-speed processes, and alternative solutions like high-speed pneumatics result in material waste and increased complexity.
Innovation Solution
A control system with a controller that selectively activates current switches to provide a variable current level to an actuator, allowing dynamic adjustment of current based on the actuator's position and required movement, enabling faster and more precise control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If peak current is increased to speed up charge transfer to the piezoelectric actuator, then actuation speed is improved, but bond wire stresses and switch component limitations worsen
Solution Approach 1:
The patent divides the single high-current path into multiple parallel current paths by adding redundant bond wires. This segmentation allows the total drive current to be distributed across multiple wires, reducing the stress on each individual bond wire while maintaining the ability to deliver high peak current for fast actuation.
Solution Approach 2:
The patent combines multiple current switches into a parallel configuration where multiple switches can operate simultaneously or sequentially. This merging of switches in parallel allows the system to deliver high peak current without overloading any single switch, as the current is shared across multiple components.
2Speed
If high-current switches are used to increase charge transfer rate, then actuation speed is improved, but component cost and size increase
Solution Approach 1:
The patent segments the high-current switching function across multiple smaller switches arranged in parallel. Each switch handles a portion of the total current, allowing the use of smaller, less expensive components while achieving the same overall current capability as a single large switch.
Solution Approach 2:
The patent changes the electrical parameters of the switching network by introducing multiple parallel paths with different current capacities. This allows optimization of individual switch specifications to match actual current requirements in each path, reducing overall component size and cost while maintaining fast charge transfer capability.
3Speed
If pneumatic actuation is used to achieve high-speed valve control, then actuation time is reduced, but material waste and system complexity increase
Solution Approach 1:
The patent replaces the pneumatic mechanical actuation system with an improved electrical actuation system using piezoelectric actuators and optimized drive circuits. This substitution eliminates the need for pneumatic venting and associated material waste while achieving comparable or better actuation speeds through electrical field control.
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 significantly reduces actuation times and improves control over gas flow, minimizing waste and operational complexity while maintaining cost-effectiveness.
Implementation Method 1
One particular type of actuator is a piezoelectric actuator, which is a nano-positioning device that deforms its shape in response to a stimulus of electrical charge
Data Source
AI summary
A process control apparatus including an actuator configured to effect changes in an industrial process, a power supply, a plurality of current switches coupled between the actuator and the power supply and a controller coupled to the plurality of current switches. The controller is configured to selectively close one or more of the plurality of current switches so as to provide a selectable level of current from the power supply to the actuator. In variations, a plurality of discharge switches are coupled to the actuator and the controller is configured to selectively close the discharge switches so as to provide a selectable level of charge to discharge from the actuator.