P-I-N diode switch
Solid state switches use the same voltage and power supply as the RF amplifier. This simplifies circuit design and reduces input power requirements.
Vanek, C. S.↗
SEARCH · Engineering Papers
Results for “SWITCHING CIRCUIT”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Inductive storage for quasi-steady MPD thrusters
Experiments in which a quasi-steady MPD thruster is driven by a large inductor demonstrate the feasibility of using inductive energy storage to couple an intermittent high power plasma thruster to a lower power steady state supply, such as a thermionic converter. Switching between inductor charging and MPD thrusting phases of the current cycle occurs smoothly, with the voltage spike generated during switching sufficient to initiate the arc discharge in the thruster without an auxiliary starting circuit. Further, the current waveforms delivered by the inductor are of a shape suitable for the quasi-steady thrusting process, and they agree with analytical estimates, indicating that the interaction between the thruster impedance and the inductive source is dynamically stable.
Clark, K. E.↗
Digital Control of Analog Detector
Reference level required to set switching point of analog comparator at desired level determined and set by computer controlled circuit.
Brown, J.↗
Physics and design of advanced IR bolometers and photoconductors
The state-of-the-art in photoconductors and bolometers is reviewed, centering on the materials development and concepts of extrinsic Si and Ge devices. It is suggested that in the field of 2-D detector arrays the hybrid circuits containing a photoconductor or a photodiode array, bonded with In solder to a switched MOS readout device with up to 60 x 60 elements, will produce superior performance. Other systems discussed include charge-coupled devices, developed for visible-light imaging and adapted to IR imaging, and charge-injection devices, a monolithic combination of a standard photoconductor and a metal-insulator-semiconductor capacitor. Finally, it is pointed out that a nonequilibrium theory of bolometer noise demonstrates the possibility of reducing the traditionally accepted noise limits by 60 percent for Johnson noise and 30 percent for the noise from phonons in the thermal link of the bolometer.
Haller, E. E.↗
Transformerless dc-Isolated Converter
Efficient voltage converter employs capacitive instead of transformer coupling to provide dc isolation. Offers buck/boost operation, minimal filtering, and low parts count, with possible application in photovoltaic power inverters, power supplies and battery charges. In photovoltaic inverter circuit with transformerless converter, Q2, Q3, Q4, and Q5 form line-commutated inverter. Switching losses and stresses nil because switching performed when current is zero.
Rippel, Wally E.↗
Improved Thermal-Switch Disks Protect Batteries
Improved thermal-switch disks help protect electrical batteries against high currents like those due to short circuits or high demands for power in circuits supplied by batteries. Protects batteries against excessive temperatures. Centered by insulating fiberglass washer. Contains conductive polymer that undergoes abrupt increase in electrical resistance when excessive current raises its temperature above specific point. After cooling, polymer reverts to low resistance. Disks reusable.
Darcy, Eric↗
Passive high-power-density grid interface device
A hybrid switched capacitor power converter for high-power applications is provided. The converter has a transistor-switched input-stage boost converter followed by a capacitor-and-diode ladder circuit. The converter is adapted to produce an output voltage of at least 5 kV at a power level of at least 0.5 kW. The ladder circuit includes one or more multi-stage rails.
Brocato, Robert W.↗
Understanding of self-terminating pulse generation using silicon controlled rectifier and RC load
Recently a silicon controlled rectifier (SCR)-based circuit that generates self-terminating voltage pulses was employed for the detection of light and ionizing radiation in pulse mode. The circuit consisted of a SCR connected in series with a RC load and DC bias. In this paper, we report the investigation of the physics underlying the pulsing mechanism of the SCR-based. It was found that during the switching of SCR, the voltage across the capacitor increased beyond that of the DC bias, thus generating a reverse current in the circuit, which helped to turn the SCR off. The pulsing was found to be sustainable only for a specific range of RC values depending on the SCR’s intrinsic turn-on/off times. The findings of this work will help to design optimum SCR based circuits for pulse mode detection of light and ionizing radiation without external amplification circuitry.
36 MATERIALS SCIENCE↗
Equivalent circuit for VO{sub 2} phase change material film in reconfigurable frequency selective surfaces
We developed equivalent circuits of phase change materials based on vanadium dioxide (VO{sub 2}) thin films. These circuits are used to model VO{sub 2} thin films for reconfigurable frequency selective surfaces (FSSs). This is important as it provides a way for designing complex structures. A reconfigurable FSS filter using VO{sub 2} ON/OFF switches is designed demonstrating −60 dB isolation between the states. This filter is used to provide the transmission and reflection responses of the FSS in the frequency range of 0.1–0.6 THz. The comparison between equivalent circuit and full-wave simulation shows excellent agreement.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Ultranarrow linewidth, magnetically switched, long pulse, xenon chloride laser
A spectral linewidth of less than 70 fm and diffraction-limited beam divergence have been obtained from a long-pulse, electric-discharge xenon chloride laser with intracavity Fabry-Perot etalons. A gain duration of 100 ns provided for multipass operation of the etalons, significantly improving both contrast and finesse. The electrical-discharge circuit required to produce this long gain duration was comprised of a pulse-forming network, a saturable-inductor magnetic switch, and a tapered constant-impedance interface transmission line.
Pacala, T. J.↗
Temperature-Dependent Characterization, Modeling, and Switching Speed-Limitation Analysis of Third-Generation 10-kV SiC MOSFET
The temperature-dependent characteristics of the third-generation 10-kV/20-A SiC MOSFET including the static characteristics and switching performance are carried out in this paper. The steady-state characteristics, including saturation current, output characteristics, antiparallel diode, and parasitic capacitance, are tested. Here, a double pulse test platform is constructed including a circuit breaker and gate drive with >10-kV insulation and also a hotplate under the device under test for temperature-dependent characterization during switching transients. The switching performance is tested under various load currents and gate resistances at a 7-kV dc-link voltage from 25 to 125 C and compared with previous 10-kV MOSFETs. A simple behavioral model with its parameter extraction method is proposed to predict the temperature-dependent characteristics of the 10-kV SiC MOSFET. The switching speed limitations, including the reverse recovery of SiC MOSFET's body diode, overvoltage caused by stray inductance, crosstalk, heat sink, and electromagnetic interference to the control are discussed based on simulations and experimental results.
10-kV silicon carbide (SiC) metal–oxide–semiconduc↗
Biasable, Balanced, Fundamental Submillimeter Monolithic Membrane Mixer
This device is a biasable, submillimeter-wave, balanced mixer fabricated using JPL s monolithic membrane process a simplified version of planar membrane technology. The primary target application is instrumentation used for analysis of atmospheric constituents, pressure, temperature, winds, and other physical and chemical properties of the atmospheres of planets and comets. Other applications include high-sensitivity gas detection and analysis. This innovation uses a balanced configuration of two diodes allowing the radio frequency (RF) signal and local oscillator (LO) inputs to be separated. This removes the need for external diplexers that are inherently narrowband, bulky, and require mechanical tuning to change frequency. Additionally, this mixer uses DC bias-ability to improve its performance and versatility. In order to solve problems relating to circuit size, the GaAs membrane process was created. As much of the circuitry as possible is fabricated on-chip, making the circuit monolithic. The remainder of the circuitry is precision-machined into a waveguide block that holds the GaAs circuit. The most critical alignments are performed using micron-scale semiconductor technology, enabling wide bandwidth and high operating frequencies. The balanced mixer gets superior performance with less than 2 mW of LO power. This can be provided by a simple two-stage multiplier chain following an amplifier at around 90 GHz. Further, the diodes are arranged so that they can be biased. Biasing pushes the diodes closer to their switching voltage, so that less LO power is required to switch the diodes on and off. In the photo, the diodes are at the right end of the circuit. The LO comes from the waveguide at the right into a reduced-height section containing the diodes. Because the diodes are in series to the LO signal, they are both turned on and off simultaneously once per LO cycle. Conversely, the RF signal is picked up from the RF waveguide by the probe at the left, and flows rightward to the diodes. Because the RF is in a quasi- TEM (suspended, microstrip-like) mode, it impinges on the diodes in an anti-parallel mode that does not couple to the waveguide mode. This isolates the LO and RF signals. This operation is similar to a cross-bar mixer used at low frequencies, except the RF signal enters through the back-short end of the waveguide rather than through the side. The RF probe also conveys the down-converted intermediate frequency (IF) signal out to an off-chip circuit board through a simple LC low-pass filter to the left as indicated. The bias is brought to the diodes through a bypass capacitor at the top.
Siegel, Peter↗
Monolithic Microwave Integrated Circuit (MMIC) technology for space communications applications
Future communications satellites are likely to use gallium arsenide (GaAs) monolithic microwave integrated-circuit (MMIC) technology in most, if not all, communications payload subsystems. Multiple-scanning-beam antenna systems are expected to use GaAs MMICs to increase functional capability, to reduce volume, weight, and cost, and to greatly improve system reliability. RF and IF matrix switch technology based on GaAs MMICs is also being developed for these reasons. MMIC technology, including gigabit-rate GaAs digital integrated circuits, offers substantial advantages in power consumption and weight over silicon technologies for high-throughput, on-board baseband processor systems. For the more distant future pseudomorphic indium gallium arsenide (InGaAs) and other advanced III-V materials offer the possibility of MMIC subsystems well up into the millimeter wavelength region. All of these technology elements are in NASA's MMIC program. Their status is reviewed.
Connolly, Denis J.↗
Monolithic transistor gate energy recovery system
Energy is recovered from an insulated gate semiconductor switch, such as a MOSFET, that is otherwise lost in the gate capacitance by producing a notch in the gate control voltage for an interval B following an interval A after initial application of a gate control voltage pulse for turning the switch on, and a notch for an interval C following termination of the gate control voltage pulse followed by interval D during which the switch is turned on again, where each interval is a period .DELTA.T given by ##EQU1## L.sub.s is the inductance (discrete and/or parasitic) in series with the gate electrode of the insulated gate semiconductor switch, and C.sub.in is the capacitance of that switch between its gate and source electrodes. The interval .DELTA.T may be provided directly by timing in a pulse forming circuit for the gate control voltage applied, or adaptively by sensing the gate voltage v.sub.g and comparing it with fixed progressively higher voltages v.sub.1, v.sub.2 and v.sub.3, where v.sub.2 is intermediate v.sub.1 and v.sub.3 which correspond to the lower and upper levels of v.sub.g as the switch is turned off and on.
Rippel, Wally E.↗
Novel High-Power Microwave Circulator Employing Circularly Polarized Waves
A novel four-port circulator is presented which uses an inline ferromagnetic element to allow for transmission or reflection depending on the sense of the incident circularly polarized wave. This configuration has been shown to reduce the dependency on ferrite anisotropy and support higher power, low rf loss, operation. An analytic analysis of this device is presented here alongside corroborating cold test data of the first prototype. High-power operation was performed at 2.856 GHz, with input power levels up to 8 MW for 3.5 μs in a pressurized nitrogen environment. The results from this research not only demonstrate ability to eliminate the use of greenhouse insulators, such as SF6, but also provide conceptual groundwork for a new class of ultrahigh power (50 MW+) nonreciprocal networks including circulators, isolators, phase shifters, and rf switches.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
A Sparse Tableau Formulation for Node-Breaker Representations in Security-Constrained Optimal Power Flow
Realistic representations of contingencies in AC optimal power flow (ACOPF) often challenge traditional bus-branch network models. Derived from nodal analysis, such approaches represent network constraints in terms of the familiar bus admittance matrix, Ybus. A fixed Ybus is unable to represent common circuit breaker actions such as bus splitting. Work-arounds for Ybus-based analysis typically rely on topology processing, switching between different Ybus matrices depending on breaker settings. In this paper, we propose a very general node-breaker approach, employing multi-port element models and using a sparse tableau formulation (STF) for network constraints. Instead of treating breaker action as altering network topology, and hence changing the structure of Kirchhoff’s voltage law (KVL) and Kirchhoff’s current law (KCL) equations, this approach represents a breaker’s position as impacting only constraints associated with a single component, thereby maintaining fixed structure in the KVL and KCL constraints. While larger numbers of variables are required, STF proves sparser than Ybus formulations. Numerical case studies herein demonstrate that STF provides computational efficiency comparable to a Ybus-based ACOPF at the scale of several hundred buses, and lower computational cost in an example of over one thousand buses.
Park, Byungkwon (ORCID:000000033189816X)↗
Integration of Ultrawide Bandgap Photoconducting Semiconductor Switches into High-Voltage, High-Current Pulser Systems
In this feasibility study we will evaluate the viability of integrating ultrawide bandgap (UWBG) photoconducting semiconductor switches (PCSS) in high-voltage pulser systems capable of driving low-impedance dynamic loads critical for next-generation accelerator and RF-source applications. The project consisted of developing modelling tools that would inform design of UWBG PCSS packages that could be mounted onto conventional circuit boards. Specifically, we are interested in evaluating the following through simulation software: (1) resistance to electrical breakdown (2) proximity effects due to high-frequency skin effect (3) transient behavior from switching (4) effective transmission of RF signals (5) thermal dynamics of the switch under operation (6) sensitivity to inhomogeneities in optical excitation of the material (7) cross-talk effects from parallel switching structures, and (8) susceptibility of system to damaged components. The project resulted in the development of a special-purpose circuit code that implements photoconductivity physics. This code was used to evaluate objectives 1-6 above, identifying a critical requirement associated with the need for fine control of dopant concentrations in the UWBG material to reach an optimal solution for voltage standoff and laser light responsivity requirements. In addition, we identified that the temperature dependence of the electrical conductivity of this material was typically not well-measured and developed a platform for measuring both the “dark” and “illuminated” conductivity on real physical switches in the lab to better inform our models.
24 POWER TRANSMISSION AND DISTRIBUTION↗
Magnetically switched power supply system for lasers
A laser power supply system is described in which separate pulses are utilized to avalanche ionize the gas within the laser and then produce a sustained discharge to cause the gas to emit light energy. A pulsed voltage source is used to charge a storage device such as a distributed capacitance. A transmission line or other suitable electrical conductor connects the storage device to the laser. A saturable inductor switch is coupled in the transmission line for containing the energy within the storage device until the voltage level across the storage device reaches a predetermined level, which level is less than that required to avalanche ionize the gas. An avalanche ionization pulse generating circuit is coupled to the laser for generating a high voltage pulse of sufficient amplitude to avalanche ionize the laser gas. Once the laser gas is avalanche ionized, the energy within the storage device is discharged through the saturable inductor switch into the laser to provide the sustained discharge. The avalanche ionization generating circuit may include a separate voltage source which is connected across the laser or may be in the form of a voltage multiplier circuit connected between the storage device and the laser.
Pacala, Thomas J.↗