Bidirectional Applications Research Articles

Avalanche Breakdown Energy in Silicon Carbide Junction Field Effect Transistors

The energy dissipation capabilities of a 1200 V, 0.1 cm2 JFET operating in blocking mode were investigated. These devices, which are used in bidirectional circuit breaker applications, can conduct a current of 13 A in forward-conduction mode, and typically block a voltage up to 1200 V in blocking mode. In this document, the blocking limits of the device were pushed slightly to the point where avalanche breakdown occurs. A high voltage pulse generator was designed and constructed to drive the JFET into this state and to monitor the dissipated energy. The devices were able to handle up to 18.14 mJ.

600-V Symmetrical Bi-Directional Power Switching Using SiC Vertical-Channel JFETs with Reliable Edge Termination

Numerous high-voltage applications require symmetrical bi-directional power flow control and protection circuitry. While mechanical contactors and circuit breakers provide bi-directional fault protection, they have slow actuation and suffer severe degradation during repeated fault isolation. The normally-on (N-ON) SiC vertical-channel Junction-Field-Effect-Transistor (VJFET) is an efficient solution for bi-directional circuit-breaker applications due to its low conduction/switching losses, +500°C operational capability, ON-state match of the no-fault operating mode of the system, efficient gate-drive operation under unipolar biasing, and majority carrier device scalability. Efficient 600-V/10-A symmetrical bi-directional power flow was demonstrated using 0.1-cm2 1200-V rated N-ON VJFETs with a gate driver applying 0-V and -34 V gate biases during the ON and OFF states, respectively. A self-aligned trenched guard-ring structure provides reliable edge termination.

Commuting Conversions vs. the Standard Conversions of the “Good” Connectives

Commuting conversions were introduced in the natural deduction calculus as ad hoc devices for the purpose of guaranteeing the subformula property in normal proofs. In a well known book, Jean-Yves Girard commented harshly on these conversions, saying that ‘one tends to think that natural deduction should be modified to correct such atrocities.’ We present an embedding of the intuitionistic predicate calculus into a second-order predicative system for which there is no need for commuting conversions. Furthermore, we show that the redex and the conversum of a commuting conversion of the original calculus translate into equivalent derivations by means of a series of bidirectional applications of standard conversions.

Comparative analysis of single-and Three-Phase Dual Active Bridge Bidirectional DC-DC Converters

Many modern power conversion systems require a bidirectional energy transfer capability as a central part of their system operation. Preferably, such systems should use a single high efficiency power electronic conversion system to reduce size, weight and cost. For higher power bidirectional conversion, the common topology proposed is a dual active bridge structure, where two DC-AC converters are coupled back-to-back through an AC inductor/transformer. Either single-phase or three-phase converters have been proposed for such a system, but to date no clear-cut basis for selecting between these two alternatives has been established. This paper presents a comparative evaluation of single-and three-phase back-to-back converters for use in a bidirectional power transfer applications. The paper considers these two alternatives from the perspective of operating performance and losses, and provides a basis for selecting between the two topologies in any particular operating context.

Integrated Heterojunction Bipolar Transistor Optically Injection-Locked Self-Oscillating Opto-Electronic Mixers for Bi-Directional Fiber-Fed Wireless Applications

A 30-GHz-band third harmonic optically injection-locked self-oscillating opto-electronic mixer is implemented with a 10-GHz InP heterojunction bipolar transistor monolithic microwave integrated circuit oscillator. The monolithic self-oscillating mixer can be optically injection locked in wide operating conditions and can perform efficient frequency up- and down-conversion with low-power optical local-oscillator signals. Using the mixer, bi-directional transmission of 32 quadrature amplitude modulation data in a 30-GHz fiber-fed wireless link is successfully demonstrated.

Integrating firewire peripheral interface with an ethernet custom network processor

Bandwidth demands on ubiquitous Ethernet have grown immensely, driven by the rapid expansion of real-time applications like audio/video streaming. In a related research, the authors designed a novel high-performance custom network processor chip using field programmable gate arrays (FPGAs). The main function of this chip (named SPEED) is to bypass the operating system processing of network protocol stack at the host computer by off-loading its networking functions to hardware. This simplification is not only required to fit in a hardware solution, but also it improves network performance. The novel chip utilizes the concept of Ethernet channels, where Ethernet frames are addressed in a multicast addressing scheme. In this article, we integrate the chip with a Firewire peripheral interface (FPI). A crucial function of the FPI design is to convert the IEEE 1394 isochronous traffic to the Ethernet frame format via two independent asynchronous write and read buffers. The FPI also manages the SPEED hardware interrupt signals in a bi-directional communication scheme. The goal of this research is to map isochronous Firewire packets into Ethernet frames by utilizing the SPEED Ethernet channel assignment capability. We used Verilog Hardware Description Language (HDL) to synthesize the FPI design. Since the FPI needs to support bi-directional communication, we also present a generic HDL model for bi-directional data sharing, which can be used in similar bi-directional applications. Initial performance measures show that the FPI consumes less that 0.15 W of power. Also we found that the synthesized design utilizes only 28% of the target chip resources. Hence it was possible to incorporate it with the SPEED design in the same FPGA chip. This low power consumption will lead to powering SPEED-FPI based network devices through the network cable and eliminate the process of regular electrical power outlet installations and maintenance. Thus, the SPEED-FPI system reduces the installation complexity, especially for large number of devices (e.g., surveillance cameras).

A valveless micropump for bidirectional applications

This paper describes a new valveless micropump for bidirectional use. The micropump was fabricated by bonding a fluidic channel and a membrane actuator. The fluidic channel was etched on a glass substrate and the membrane actuator was made on a silicon wafer. The membrane is actuated by a piezoelectric ceramic (PZT) plate so that the membrane generates blowing and suction flows successively along an oblique channel which is connected to the main channel. A blowing flow from an oblique channel into the main channel generates forward flow in downstream, while a suction flow generates the smaller reverse flow in downstream. Therefore, the overall flow in the main channel has a downstream flow and it can have a directional characteristic when two oblique channels are used. The performance of the micropump depends on the geometry of the fluidic channel, driving frequency and voltage of the actuator. The geometry of the micropump was optimized by numerical analysis and the performance test was done under various operating conditions. The maximum flow rate was 323μl/min and the maximum back pressure was 294Pa when the membrane actuator of 10mm×10mm was driven at 130Hz and 385V.

Transmission Error in Helical Synchronous Belt Drives in Bidirectional Operation. No Load.

Synchronous belt drives are often used in bidirectional applications such as priniting machines, high-performance machine tools and industrial robotics, and are required to provide high transmission and positioning accuracy. Helical synchronous belt drives, in comparison to conventional synchronous belt drives, are effective for reducing noise and transmission error over single pitches of the pulley. In the present study, the transmission error of a helical synchronous belt drive under installation tension was investigated both theoretically and experimentally for the case when the drive reverses direction. The computed transmission error agrees with the experimental results, confirming the applicability of the proposed theoretical analysis for transmission error. It is found that transmission error in this case is generated by a change in the contact state between the belt tooth flank and the pulley tooth flank, and axial displacement of the belt between the driving pulley and the driven pulley. By setting the installation tension as high as possible, the transmission error can be reduced and stabilized more quickly. In addition, when the outside diameters of both the driving and driven pulleys are equal, transmission error does not occur.