Embodiments of the present invention relate generally to a switching device for selectively switching a current in a current path, and more particularly to switching devices based on micro-electromechanical systems (MEMS), an even more particularly to an array of MEMS-based switching modules as may be connected in a series circuit to achieve a desired voltage rating.
It is known to connect MEMS switches to form a switching array, such as series connected modules of parallel switches, and parallel connected modules of series switches. An array of switches may be needed because a single MEMS switch may not be capable of either conducting enough current, and/or holding off enough voltage, as may be required in a given switching application.
An important property of such switching arrays is the way in which each of the switches contributes to the overall voltage and current rating of the array. Ideally, the current rating of the array should be equal to the current rating of a single switch times the number of parallel branches of switches, for any number of parallel branches. Such an array would be said to be current scaleable. Current scaling has been achieved in practical switching arrays but voltage scaling has not.
In concept, the voltage rating of the array should be equal to the voltage rating of a single switch times the number of switches in series. However, achieving voltage scaling in practical switching arrays has presented difficulties. For instance, in known switching arrays for a given voltage rating of a switching module, it is not possible to continue to increment the number of switching modules that may be connected in series to achieve any desired voltage rating. This is due to the fact that the voltage rating of the circuitry in a respective switching module will eventually be exceeded due to relatively large voltage levels that can develop across the open switches. Thus, known switching arrays are limited in the number of switches that can be interconnected in series, and consequently lack the ability to provide voltage scalability.
Generally, aspects of the present invention fulfill the foregoing needs by providing in one example embodiment a system comprising at least one switching module. Other such modules may be used as building blocks of a switching array configured so that any number of modules can be connected in a series circuit to achieve a desired voltage rating (e.g., voltage scalability). The switching module includes switching circuitry comprising at least one micro-electromechanical system switch for selectively establishing a current path from an input line to an output line of the switch in response to a gate control signal applied to the switch. The switching module further includes control circuitry coupled to the switching circuitry to supply the gate control signal to the micro-electromechanical system switch, and power circuitry coupled to the control circuitry and the switching circuitry. The power circuitry provides an input terminal pair and an output terminal pair galvanically isolated from one another, wherein a module power input signal received through the input terminal pair is electrically referenced to the input line of the switch, and a module power output signal supplied through the output terminal pair is electrically referenced to the output line of the switch so that the module output power signal is unaffected by a voltage that develops across the input and output lines of the micro-electromechanical system switch when the switch is set to an open state.
The invention is explained in the following description in view of the drawings that show:
In accordance with embodiments of the present invention, structural and/or operational relationships, as may be used to provide voltage scalability (e.g., to meet a desired voltage rating) in a switching array based on micro-electromechanical systems (MEMS) switches are described herein. Presently, MEMS generally refer to micron-scale structures that for example can integrate a multiplicity of functionally distinct elements, e.g., mechanical elements, electromechanical elements, sensors, actuators, and electronics, on a common substrate through micro-fabrication technology. It is contemplated, however, that many techniques and structures presently available in MEMS devices will in just a few years be available via nanotechnology-based devices, e.g., structures that may be smaller than 100 nanometers in size. Accordingly, even though example embodiments described throughout this document may refer to MEMS-based switching devices, it is submitted that the inventive aspects of the present invention should be broadly construed and should not be limited to micron-sized devices.
In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of various embodiments of the present invention. However, those skilled in the art will understand that embodiments of the present invention may be practiced without these specific details, that the present invention is not limited to the depicted embodiments, and that the present invention may be practiced in a variety of alternative embodiments. In other instances, well known methods, procedures, and components have not been described in detail.
Furthermore, various operations may be described as multiple discrete steps performed in a manner that is helpful for understanding embodiments of the present invention. However, the order of description should not be construed as to imply that these operations need be performed in the order they are presented, nor that they are even order dependent. Moreover, repeated usage of the phrase “in one embodiment” does not necessarily refer to the same embodiment, although it may. Lastly, the terms “comprising”, “including”, “having”, and the like, as used in the present application, are intended to be synonymous unless otherwise indicated.
Each module 14, 16 of the array (other than a first module 12) has respective input terminals (Line In, Power In, and Control In) connected to the respective output terminals (Line Out, Power Out and Control Out)) of a precedent (e.g., previous) module in the series circuit. For example, terminals Line Out, Power Out and Control Out of module 12 are connected to terminals Line In, Power In, and Control In of the next module in the series circuit (e.g., module 14). Similarly, the terminals Line Out, Power Out and Control Out of module 14 are connected to terminals Line In, Power In, and Control In of the next module in the series circuit (e.g., module 16).
When each switching module of the array is set to a closed switching state, a current (e.g., Iload) flows, for example, from a first module of the series array (e.g., switching module 12 in
Power and control may be applied to first module 12 of the series array from a power and control circuit 20 configured to provide appropriate power and control to first module 12. Power and control signals provided by circuit 20 are each electrically referenced to the respective terminal Line In of module 12. That is, circuit 20 supplies power to first module 12 of the series array by way of the input terminal labeled Power In at a suitable voltage level, which is electrically referenced to the input terminal labeled Line In. In case of a poly-phase system, such as a three-phase system the source of power could be provided through a respective resistor connected from the power supply to a respective one of the other phases of such a three phase system, or to neutral for a single phase system. Circuit 20 is also configured to selectively provide control as to whether each switching module should be set to an open state or to a closed state, and passes that information to first switching module 12 through the terminal labeled Control In.
When each switching module of the array is set to a respective open switching state, there is an open voltage that can develop across contacts 102 and 104 of a respective MEMS-based switching circuitry 106 (
The inventors of the present invention have innovatively recognized circuitry that is configured to transfer (e.g., propagate) power supplied at each terminal pair Power In and Line In to each terminal pair Power Out and Line Out unaffected by the voltage that develops in the open switching state across terminals Line In and Line Out.
Although in
The electrical power needs of each respective switching module are met by electrical power applied through input terminal Power In, referenced to input terminal Line In. For example, power may be supplied directly to power circuitry 108 (and control circuitry 110) through input terminal Power In. Power circuitry 108 is configured to provide output power through output terminal Power Out and this output power is appropriately adjusted (e.g., voltage level shifted) based on the amount of open voltage that develops across MEMS switching circuitry 106.
Control circuitry 110 may be configured to perform two basic functions. The first function is to perform any needed voltage level shifting between terminal Control In and the Gate Control signal applied to MEMS switching circuitry 106 to set a desired switching state, e.g., an open or a closed switching state. For switches whose gate control terminal is referenced to terminal Line In, this first function can be performed simply with just a line connection (e.g., through a wire) to pass the Gate Control signal to the respective gate control terminal. The second function is to provide an appropriate voltage level shifting of the module control signal to be passed to the next switching control module through terminal Control Out.
In operation, each switching module may be configured to perform the following example functions:
Monitoring a module control signal between Line In and Control In to control whether the MEMS-based switching circuitry (e.g., a plurality of parallel-connected switches) should be set to an open state or to a closed state.
Electrically referencing at least some of the circuitry in the respective switching module to Line In.
Applying a Gate Control signal to the respective MEMS-based switching circuitry therein referenced to Line In.
Obtaining its local power needs from Power In, referenced to Line In.
Using the open switch voltage, as may develop between Line In and Line Out of the MEMS-based switching circuitry, to provide an appropriate adjustment (e.g., voltage level shift) to the respective power and control signals, as such signals propagate from input to output to be supplied to the next switching module in the series. For example, the maximum (e.g., worst-case) voltage level shift may be required when the open switch voltage approximates the voltage rating of circuitry in the respective switching module.
Returning to
One example embodiment of grading network 30 is shown in
While various embodiments of the present invention have been shown and described herein, it is noted that such embodiments are provided by way of example only. Numerous variations, changes and substitutions may be made without departing from the invention herein. Accordingly, it is intended that the invention be limited only by the spirit and scope of the appended claims.
Number | Name | Date | Kind |
---|---|---|---|
7190092 | Ivanciw et al. | Mar 2007 | B2 |
7218499 | Martin et al. | May 2007 | B2 |