Glenn Scott Claydon

High-efficiency, high-density MHz magnetic components for low profile converters

A highly efficient (99.5%) transformer and resonant inductor with very high power density (1500 W/in/sup 3/) and low profile (height 40) of small gaps to reduce the effect of fringing fields. The high-frequency loss measurements for such highly efficient inductors requires a special ring down measurement set-up which is also described. >

High efficiency, high density MHz magnetic components for a low profile converter

A highly efficient (99.5%) transformer and resonant inductor with very high power density (1500 W/in/sup 3/) and low profile (height<0.4 in) are described. The design of these components is based on a tradeoff study which establishes the optimum operating frequency to be around 1 MHz. The transformer utilizes highly efficient thin flex circuit windings. The windings are novel folded copper patterns, eliminating the need for vias and resulting in very low DC resistance. The winding arrangements have a high degree of interleaving between the primary and secondary windings, resulting in very low AC conductor losses due to skin and proximity effect. The core is a low profile design with very low core losses. The resonant inductor, instead of using low permeability material, uses highly efficient high permeability material. The desired low permeability is then achieved by introducing a large number (>40) of small gaps to reduce the effect of fringing fields. The high-frequency loss measurements for such highly efficient inductors require a special ring down measurement setup.<<ETX>>

Development of air-coupled ultrasound transducers for nondestructive evaluation

We report the development of air-coupled ultrasound transducers for noncontact nondestructive evaluation applications. Air-coupled ultrasound is an attractive inspection technique for materials or structures that are not suitable for contact or immersion ultrasound inspections. However, due to large acoustic impedance mismatch between air and materials in the system, tremendous acoustic power losses exist. To overcome this problem, the efficiency of the ultrasound transducers needs to be improved. We have developed large-gap capacitive micromachined ultrasound transducers (CMUTs) that have high transduction efficiency in air. The CMUT has a patterned dielectric insulation layer that supports large acoustic output but eliminates dielectric breakdown or charging failures. Acoustic tests showed that the CMUTs had significantly higher transduction efficiency than the state-of-the-art commercial transducers. This indicates improvement of air-coupled CMUTs is achievable and may lead to wide use of CMUTs for air inspections.

Micro-Electromechanical-System (MEMS) based switches for power applications

A new system for switching electrical power using Micro-Electromechanical-Systems (MEMS) is presented. The heart of the system utilizes custom designed MEMS switching device arrays that are able to conduct current more efficiently and can open orders of magnitude faster than traditional macroscopic mechanical relays. Up to now, MEMS switches have been recognized for their ability to switch very quickly due to their low mass, but have only been used to carry and switch very low currents at extremely low voltage. However, recent developments have enabled suppression of the arc that normally occurs when the MEMS switch is opened while current is flowing. The combination of the arc suppression with the MEMS switch arrays designed for this purpose enables a breakthrough increase in current and voltage handling capability. The resultant technology has been scaled to handle many Amps of current and switch 100s of volts. Such current and voltage handling capability delivers improved energy efficiency and the capacity to handle fault current levels that are encountered in typical AC or DC power systems. Fault current interruption takes place in less than 10 microseconds, almost regardless of the prospective fault current magnitude. The properties of the MEMS switch arrays allow the switching mechanism to operate at temperatures in excess of 200 deg. C. The switches also have a vibration tolerance in excess of 1000G. The combination of fast MEMS switching speed, optimized current and voltage handling capacity of the switch arrays, the arc suppression circuitry and optimized sensing and control enable a single sensing, control and switching system to operate in a small fraction of a millisecond. This paper will present the basic physics of the MEMS switches together with recent advances that enable the technology. Some illustrative examples of the ways the devices may be used to provide protection and control within electrical systems will also be presented.

A single chip 1 MHz 500 V full/half bridge driver and primary side power supply controller HVIC capable of multiple modes of operation

A high-voltage IC (HVIC) capable of controlling and driving power FETs in both full- and half-bridge power circuits employing either pulse width modulation (PWM) or resonant circuit topologies is discussed. The IC also includes a voltage-controlled oscillator capable of varying pulse width and/or frequency, thus providing a means of resonant converter control. High-voltage isolation (500 V) and level shifting for upper-side FETs is achieved on-chip, and 1 MHz operation driving four NMOS with 1000 pF gates has been demonstrated. Several power supply control and housekeeping functions are included on the chip. A window comparator which detects and reconstructs isolated pulses from a secondary side control is also included on-chip, thus providing a means of communication between the primary and secondary sides of the power supply. The combination of 15 V control logic with both high-voltage and low-voltage drivers enables this HVIC to be a single-chip primary-side controller for a variety of power circuit topologies.<<ETX>>

Toward multifunctional optical integration: an adaptive lithographic method for patterning optical structures

A new method of interconnecting various optoelectronic components is discussed. Offset error up to 25 microns can be corrected to achieve single mode alignment accuracies. Several planar optical devices were photocomposed using the adaptive photolithographic method and these have been shown to perform with the desired characteristics.

Power switch system based on Microelectromechanical switch

A power switching system combining a MEMS (Microelectromechanical systems) switch and an arc suppression circuit has been developed. The system, using a single 3mm × 3mm MEMS switch die coupled with protection electronics, has been demonstrated to switch both resistive loads and inductive loads to a peak power of around 800W. The entire opening and closing operations are completed in a few microseconds, orders of magnitude faster than mechanical relays and nearly as fast as solid state devices. The MEMS switch is an array of microscale cantilevered relays that are electrostatically opened and closed in microseconds. A pulsed diode bridge protection circuitry is used in conjunction with the MEMS switch to open and close the energized contacts without damaging the contacting surface and without generating an arc. This MEMS based power switching system is scaled in both series and parallel to increase the switched voltage and current capability respectively. MEMS switch based power switching has the capability to enable both current limiting and arc free switching, characteristics that can significantly reduce dangerous downstream fault energy for AC and DC protection and distribution applications.

High-density multimode photonic backplane

The development of a photonic backplane for high-speed and high-bandwidth communications is presented. This hybrid, multimode, multi-channel backplane structure contains both electrical and optical interconnects, suitable for next-generation high-speed servers with terabit backplane capacity. Removable and all-passively aligned high density interconnects on this backplane are achieved by polymer based optical waveguides with integrated micro-optics and VCSEL arrays on conventional printed circuit boards. The fabrication of this photonic backplane requires few additional steps outside a traditional board-manufacturing environment and is largely compatible with existing processes.

Design rules for the fabrication of binary half-tone masks used for MEMS and photonic devices

Gray scale lithography is becoming a popular technique for producing three-dimensional structures needed in fabricating photonics and MEMS devices. The structures are printed using a variable transmission mask to yield the required continuous tone intensity during image formation. In binary half tone imaging (i.e., BHT), the transmission through the mask is adjusted by varying the open area of sub-patterns. Design rules, fabrication tradeoffs and a layout methodology employing a novel primitive cell to aid in constructing the BHT masks are discussed Simulation is leveraged to tie the BHT design with expected imaging results. The overall process is exercised by fabricating a specific grayscale design for use in a photonic application. The BHT mask approach to gray scale lithography is a viable method to fabricate three-dimensional images offering MEMS and photonics communities a cost effective alternative to gray scale masks which rely on specialty materials and films.

Integration of 50-GHz traveling-wave amplifier and polymer Mach-Zehnder device using flexible substrate technology

We present the results for a 50GHz drive amplifier for use with a Mach-Zehnder modulator. The MMIC device is packaged using a flexible substrate technology to obtain compact size and broadband performance. The packaged device exhibits well-matched transmission lines on the input and output, and large gain and bandwidth. The MMIC performance is directly related to performance of the drain bias circuit.