Isolated MEMS Relay Circuit for High-Voltage Control
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Solution Overview
Problem
Existing MEMS relays face challenges in providing isolation between low voltage control and high voltage power sides while efficiently transferring control signals and power, leading to increased cost and size due to the use of isolated power supplies and optocouplers.
Innovation Solution
A MEMS relay circuit that includes a control circuit for electrical isolation, an auxiliary circuit to limit voltage across the MEMS switch, and a control circuit to manage switching events, utilizing a MEMS switch with a cantilevered beam and electrostatic actuation, along with a low-cost electronic architecture that operates in low current and high current modes to reduce power dissipation and enhance switch longevity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional isolated power supply and optocoupler are used to provide isolation between control side and power side, then electrical isolation and control signal transfer are achieved, but cost and device size increase
Solution Approach 1:
The patent combines the isolation barrier with the high-voltage switch into a single integrated device structure. The control circuit and power circuit share a common substrate with controlled impedance traces, eliminating the need for separate isolated power supplies and optocouplers. This integration maintains electrical isolation while reducing component count, cost, and overall device size.
Solution Approach 2:
The control circuit is designed to perform multiple functions: it generates control signals for the high-voltage switch, provides electrical isolation through controlled impedance traces, and interfaces with both low-voltage control inputs and high-voltage power outputs. This multi-functionality eliminates the need for separate dedicated isolation components.
2Strength
If electromechanical relays are used to control high power devices, then ability to withstand momentary overload and low on-state resistance are achieved, but size increases and switching speed decreases
Solution Approach 1:
The patent replaces the mechanical moving beam and contact structure of traditional electromechanical relays with a solid-state high-voltage switch. This substitution eliminates mechanical wear, increases switching speed, and maintains the ability to withstand overload conditions. The solid-state switch uses electronic field effects rather than mechanical motion to control current flow.
3Speed
If solid-state relays are used for switching, then fast switching speeds and no physical contacts are achieved, but leakage current increases and overload withstand capability decreases
Solution Approach 1:
The high-voltage switch employs a composite structure combining solid-state electronic components with protective circuitry. The switch integrates multiple semiconductor elements and isolation structures that enable it to achieve both fast switching characteristics of solid-state devices and the high overload withstand capability typically associated with mechanical contacts. The controlled impedance traces and isolation barrier provide additional protection against voltage spikes and overload conditions.
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 reliable electrical isolation, low leakage current, and efficient power transfer, reducing the cost and size of the MEMS relay circuit while ensuring reliable operation and longevity of the MEMS switch by limiting voltage and energy levels during switching events.
Implementation Method 1
a MEMS switch (24) having a first contact (26) and a conductive beam (28) positioned over the first contact (26) and movable between a first position, in which the conductive beam (28) is spaced from the first contact (26), and a second position, in which the conductive beam (28) contacts the first contact (26)
Data Source
Figure 1
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Figure 5
AI summary
A switching system includes a control circuit that receives On-Off signals indicative of a desired operating state of a switch. The control circuit includes an oscillator that generates a first electrical pulse responsive having a first signal characteristic or a second signal characteristic that is determined by the received On-Off signal, which may be related to a frequency or duty cycle of the pulse. A pulse transformer connected to the oscillator receives the first electrical pulse and outputs a second electrical pulse having the same one of the first signal characteristic and the second signal characteristic as the first electrical pulse. A pulse detection circuit in the control circuit receives the second electrical pulse, determines whether the second electrical pulse has the first signal characteristic or the second signal characteristic, and controls transmission of power and control signals to the switch based on this determination.