Auxiliary Circuit for MEMS Relay Voltage Limiting
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Solution Overview
Problem
Conventional electromechanical relays are large and slow, while solid-state relays have high power dissipation and leakage current issues, and existing MEMS relays are complex and unreliable in voltage limiting.
Innovation Solution
A MEMS relay circuit with a MEMS switch, an auxiliary circuit comprising parallel MOSFETs, and a control circuit that selectively activates the auxiliary circuit to limit voltage across the MEMS switch, allowing efficient and reliable operation by diverting current to the auxiliary circuit during switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electromechanical relays are used to control high power devices, then the relay can withstand momentary overload and have low on-state resistance, but the relay becomes large in size and operates at relatively slow speeds
Solution Approach 1:
The invention divides the switching function into two separate components: a MEMS switch for high-voltage isolation and an auxiliary solid-state switch for current handling. This segmentation allows each component to be optimized for its specific function, with the MEMS switch providing fast, reliable switching and the auxiliary circuit managing the high current loads, thereby resolving the contradiction between switching speed and overload capability.
Solution Approach 2:
The auxiliary circuit acts as an intermediary between the MEMS switch and the high-power load. It provides a low-impedance current path that protects the MEMS switch from excessive current and voltage spikes, enabling the MEMS switch to operate reliably at high speeds without being directly exposed to the full stress of high-power conditions.
2Speed
If solid-state relays are used for fast switching, then switching speed is improved and there are no moving parts, but power dissipation and leakage current increase
Solution Approach 1:
The invention segments the power handling functions between the MEMS switch and the auxiliary circuit. The MEMS switch, with its near-zero on-state resistance, handles the high-voltage switching with minimal power loss, while the auxiliary circuit manages current routing. This segmentation eliminates the power dissipation problems inherent in solid-state relays by using a hybrid approach that combines the advantages of both mechanical and solid-state switching.
Solution Approach 2:
The invention replaces the purely mechanical electromechanical relay with a hybrid system that uses a MEMS (micro-electromechanical) switch combined with electronic control circuitry. This substitution maintains the low power dissipation and long life of solid-state devices while preserving the low on-state resistance and overload capability of mechanical contacts through the MEMS component.
3Volume of moving object
If MEMS relays are used to reduce size, then device size is reduced, but the structure becomes overly complex and voltage limiting reliability is insufficient
Solution Approach 1:
The invention segments the protective functions into a dedicated auxiliary circuit that is simpler and more reliable than complex MEMS structures. By separating the voltage limiting and current management functions into a distinct auxiliary circuit with solid-state components, the design achieves compact size without the excessive complexity that plagues fully integrated MEMS solutions.
Solution Approach 2:
The auxiliary circuit serves as an intermediary that simplifies the overall system architecture. Rather than making the MEMS switch itself complex to handle all protection functions, the auxiliary circuit provides a dedicated, simple interface that manages voltage and current, thereby reducing the complexity burden on the MEMS component and improving overall reliability.
4Volume of moving object
If MEMS relays are used for compact size, then size is reduced, but voltage across the movable switch is not adequately limited, resulting in unreliable operation
Solution Approach 1:
The auxiliary circuit acts as a protective intermediary between the MEMS switch and the high-voltage environment. It actively monitors and limits the voltage across the MEMS switch through its solid-state components, preventing voltage breakdown and ensuring reliable operation. This intermediary protection layer allows the compact MEMS design to operate reliably in high-voltage applications.
Solution Approach 2:
The auxiliary circuit provides beforehand protection by being pre-configured to limit voltage and current before they can damage the MEMS switch. The circuit is designed to activate automatically under stress conditions, cushioning the MEMS component from voltage spikes and current surges that would otherwise cause failure, thereby ensuring long-term reliability in a compact package.
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
The solution provides a compact, low-power, and long-lasting MEMS relay with reduced conduction losses and cost, ensuring reliable performance by limiting voltage across the MEMS switch during switching intervals.
Implementation Method 1
a resonant circuit connected between the first solid state switch and the second solid state switch
Data Source
AI summary
A switching system includes a MEMS switching circuit having a MEMS switch and a driver circuit. An auxiliary circuit is coupled in parallel with the MEMS switching circuit, the auxiliary circuit comprising first and second connections that connect the auxiliary circuit to the MEMS switching circuit on opposing sides of the MEMS switch, first and second solid state switches connected in parallel, and a resonant circuit connected between the first and second solid state switches. A control circuit controls selective switching of a load current towards the MEMS switching circuit and the auxiliary circuit by selectively activating the first and second solid state switches and the resonant circuit so as to limit a voltage across the MEMS switch by diverting at least a portion of the load current away from the MEMS switch to flow to the auxiliary circuit prior to the MEMS switch changing state.