Showing papers on "Switching time published in 1994"

Electromagnetic microrelays: Concepts and fundamental characteristics

Abstract: An electromagnetic microrelay is proposed as a practical application of microelectrochemical system (MEMS) technology and the basic performance of its key components is evaluated. The contact resistance and breakdown voltage of contact electrodes are measured for very small loads and gaps. The static and dynamic deflection of the contact springs is measured for very small movements. Based on these experimental results, design guidelines for key components are proposed. Two prototypes that partly use MEMS technology are produced and their switching performance is demonstrated. One prototype uses a flat microspring with a length and width of 0.3 mm; its switching speed is more than ten times that of a conventional relay. The other is a 2×2 matrix relay, with four self-latching switches; each switch has two stable positions, open and closed, and is driven by a current pulse. This component study and prototype development verify the suitability of MEMS technology for mechanical relays.

Singlemode optical switches based on SOI waveguides with large cross-section

Abstract: The realisation of a thermo-optical Mach-Zehnder interferometer switch based on SOI (silicon-on-insulator) material is reported. At a wavelength of 1.3 mu m, on-off ratios of 13 dB (TE) and 9 dB (TM) are achieved with a switching power of 150 mW. The measured rise time is 5 mu s.

Experimental investigation on high‐speed switching characteristics of a novel symmetric Mach–Zehnder all‐optical switch

Abstract: We report the experimental results of a novel symmetric Mach–Zehnder (SMZ) all‐optical switch. Although the switching is based on the band‐filling effect in the semiconductor waveguide, the switching speed is not restricted by the slow relaxation time. We obtain fully switched, nearly square modulation, which is characteristic of the SMZ all‐optical switch. We also achieve high‐speed switching; the full width at half‐maximum of the obtained wave form is 8 ps, which is only limited by the time resolution of the detection system.

Ferroelectric liquid‐crystalline elastomers

Abstract: Oriented liquid-crystalline (LC) elastomers (polar monodomains, concerning the direction of polarisation) have been prepared from polar monodomains of ferroelectric LC-polysiloxanes by a radical photocrosslinking process. Attempts to perform ferroelectric switching lead in these soft elastomers to an elastic stress which prohibits—for low voltages—a complete reorientation of the polar axis (ferroelectric switching). A ferroelectric switching can, however, be observed for high voltages. The loop of hysteresis of this switching is asymmetric concerning the zero point of the driving voltage. Piezoelectric measurements show that these elastomers combine an elastic memory for one polar state with enough flexibility to allow a reorientation of the polar axis.

256 × 256 liquid-crystal-on-silicon spatial light modulator.

Abstract: A 256 × 256 pixel spatial light modulator (SLM) is designed and constructed by the use of liquid-crystal-on-silicon technology. The device is a binary electrically addressed SLM with a measured zero-order contrast ratio of 70:1 and an imaged contrast ratio of 10:1. The pixel pitch is 21.6 μm, which gives an array size of 5.53 mm. The electronic load time is 43 μs, and the 10%–90% switching time of the liquid crystal is ~ 75–80 μs at room temperature, which implies a maximum frame rate of ~ 8.3 kHz. We discuss the design trade-offs that are intrinsic to this type of device and describe how the primary application for the device in an optical correlator influenced the final design.

An energy-efficient CMOS line driver using adiabatic switching

Abstract: Describes a custom CMOS line driver chip and a resonant power supply that can switch eight 100 pF loads at 1 MHz six times more efficiently than a conventional (CV/sup 2/) CMOS solution. The authors describe the adiabatic charging principle used, which allows a digital circuit designer to directly trade off switching time for increased energy efficiency. Emphasis is placed on evaluating the dissipation overhead for the whole system including the power supply. Measurements confirm the predicted dissipation decrease. >

Zero-current transition PWM converters

Abstract: A zero-current transition pulse-width modulated (ZCT-PWM) d.c.-d.c. converter allows minority-carrier semiconductor devices such as, for example, bipolar junction transistors (BJTs), insulated gate bipolar transistors (IGBTs), MOSFET controlled thyristors (MCTs), and gate turn-off thyristors (GTOs), to be used as switches for high-power, high frequency applications. The ZCT-PWM converter comprises a shunt resonant branch inserted into a conventional PWM converter circuit. The resonant branch comprises a resonant inductor (Lr), a resonant capacitor (Cr), an auxiliary switch (S1), and an auxiliary diode (D1). The resonant branch is only active during a relatively short switching time in order to create a zero-current switch condition for the main pulse-modulating switch (S) without substantially increasing voltage or current stresses.

Novel adaptive tolerance band based PWM for field-oriented control of induction machines

Abstract: Two levels of an innovative adaptive switching pattern (ASP) for use in the control of induction machines are described. The ASP is based on a tolerance band control strategy resulting in nearly sinusoidal stator currents. The first level (ASP1) significantly increases the switching time thereby eliminating the very fast switching sometimes experienced. The second level (ASP2) reduces the number of double commutations by one or two orders of magnitude. The price for applying ASP is only a small, irregular, consequential increase in the current error. A rotating reference frame fixed to the rotor flux is applied. This makes ASP especially suitable for application in the field-oriented control of current controlled voltage source inverter (CC-VSI) fed induction motor drives. The theoretical background supported by conclusive simulation results illustrates clearly the significant benefits of ASP over the regular switching pattern often used. To complete the picture a short survey of the various techniques used in the speed control of induction machines is presented in the introduction. >

High speed, low power direct digital synthesizer

Abstract: A method and apparatus suitable for generating programmable digital sine waves which involves converting the output of a direct digital synthesizer or numerically controlled digital oscillator to a higher frequency with a multiplier-less structure that takes advantage of the properties of trigonometric identifies for sine and cosine. Sine waves are generated digitally using a phase accumulator which is clocked at one fundamental frequency. The phase accumulator input provides a control word which determines the intermediate frequency of the direct digital synthesizer output. Taking advantage of the periodicity of the phase accumulator operation, the outputs of the accumulator are utilized to address a read only memory ROM lookup table which produces in-phase and quadrature samples of the sine wave at the intermediate frequency. The in-phase and quadrature samples are then complemented (i.e. negated) to produce an additional set of in-phase and quadrature samples which are 180° out of phase from the original samples. Switching between these four possible outputs at a higher fundamental clock frequency results in the translation of the intermediate frequency output to a higher frequency.

An analytical a-Si:H TFT DC/capacitance model using an effective temperature approach for deriving a switching time model for an inverter circuit considering deep and tail states

Abstract: This paper presents an analytical a-Si:H DC/capacitance model using an effective temperature approach for deriving a switching time model for an inverter circuit considering deep and tail states. Using an effective temperature approach, the localized deep and tail states have been considered in the DC/capacitance model and the switching time model. As verified by the published data, the analytical DC/capacitance model provides an accurate prediction. Based on the analytical model, the threshold voltage of an a-Si:H TFT is proportional to the deep state density and the switching time of the TFT-inverter is dependent on the tail state density. >

A new adaptive driving technique for high current gate controlled devices

Abstract: MOSFETs and IGBTs devices are increasingly used in electronic circuits due to both the easy driving and the capability to handle high currents and voltages at high switching frequencies. This paper deals with a new driver circuit that allows optimisation of the switching speed, reduction of the energy losses during the switching time, and limiting of the electromagnetic interference (EMI). Firstly an analysis of voltage and current switching waveforms of gate insulated devices is performed. Hence, it is shown how to control voltage and current slopes independently by using a suitable adaptive driving technique based on a PLL approach. Such a technique has been adapted in order to correctly generate the gate signals regardless of the operating conditions. Finally, practical tests of the proposed driving circuit obtained using a single switch converter and IGBT devices are reported. >

A time dependent hydrodynamic device simulator SNU-2D with new discretization scheme and algorithm

Abstract: A two-dimensional device simulator SNU-2D based on the hydrodynamic model is developed for the simulation and analysis of submicron devices. The simulator has the capacity for both self-consistent steady-state and transient-state simulation. To obtain better convergence and numerical stability, we adopt an improved discretization scheme for the carrier energy flux equation and a new strategy for the transient simulation. In steady-state simulation the new discretization scheme shows a considerable improvement in convergence rate and numerical accuracy compared with the existing schemes. A transient simulation study is carried out on a deep submicron n-MOSFET used in the sense amplifier of SRAM cells to investigate the gate-switching characteristic. It is found that the behavior of carrier temperature is quasi-static during the switching time even for very fast switching speed, while the behavior of impact ionization under transient mode deviates from that under dc mode as the switching speed increases. >

Optical energy considerations for diode-clamped smart pixel optical receivers

Abstract: We calculate the switching time as a function of optical energy for a single-stage smart pixel receiver. We find that operating the receivers dynamically using modelocked pulses is the most energy-efficient method of operation. We also show that the receivers no longer operate with constant optical input energy, like the symmetric self electro-optic effect device (S-SEED), but rather the product of the required optical energy and the switching time is constant, as a result of the introduction of electrical voltage gain. >

Frequency synthesizer using noninteger division and phase selection

Abstract: A frequency synthesizer provides a synthesized signal. The synthesizer includes an oscillator that supplies a fast clock signal to a divider programmable by a digital data. The most significant bits of the digital data are provided to the programmable divider, and the least significant bits are provided to an accumulator that cooperates with the programmable divider to increment by one unit its division rank when the accumulator overflows. The synthesizer further includes a generator for generating n increasing delay phases of the synthesized signal; a comparator for comparing the content of the accumulator with n ranges of possible increasing values; and circuits for selecting, as the synthesized signal, the phase whose rank corresponds to the rank of the range within which the content of the accumulator is comprised.

Digital PLL frequency synthesizer

Abstract: A digital frequency synthesizer includes a digital-to-analog (1), a low pass filter (2), and a controllable oscillator (3), where the oscillator output is the synthesizer output. K number of RS flip-flops (101-108) produce error signals which are coupled to the DAC. The S inputs of the flip-flops come from a phase-splitter (8) which is driven by the more-significant bits unit of an accumulator (5) which is clocked by a reference frequency. The R inputs of the same flip-flops get input pulses from a pulse distributor (9) which is driven by the synthesizer output. The frequency resolution can be increased by adding a less-significant bits accumulator (15), coupled to the more-significant bits unit.

Physics and Electronic Model of Deformed Helix Ferroelectric Liquid Crystal Displays

Abstract: An electronic equivalent circuit is shown to completely describe both the electrical as well as the electrooptical properties of deformed helix ferroelectric (DHF) liquid crystal displays (LCDs). The static and the dynamic performance of DHF-LCDs are modeled using an equivalent circuit. The agreement between modeled gray-scale performance of DHF-LCDs and experiments is excellent. Several driving schemes derived from the equivalent circuit provide the full gray scale and render DHF-LCDs video-compatible at voltages below 13 V. Moreover, dc-free and thus ghost-image-free operation of DHF-LCDs is shown to be feasible with minimal loss of brightness. Capacitive coupling is shown to decrease the switching time of DHF-LCDs from 30 µs to 6 µs.

Automatic frequency control apparatus

Abstract: The preferred embodiment of the present invention encompasses an automatic frequency control system implemented in a radiotelephone (101). The radiotelephone (101) includes a frequency synthesizer. The frequency synthesizer uses a division ratio varied with time by a multi accumulator fractional N synthesizer (140) such that the effective division ratio may be varied by non-integer steps. The division ratio is programmed to realize the desired channel frequency, the desired modulation waveform, and any automatic frequency correction offset. An accurate clock is provided to the control logic (104) and the user interface (105) sections of the radiotelephone (101) using a second multiple accumulator fractional N division system (139). This second fractional N division system (139) is programmed based on the automatic frequency control programming of the first fractional N synthesizer (140). This lower frequency may then be multiplied in a phase locked loop to provide an accurate reference at a second reference frequency.

circuit for saving power consumption in standby state

Abstract: A circuit for saving power consumption in a TV/VCR set reduces the voltage induced into the secondary of a transformer when the set is in standby, when the monitor is off and when a programmed recording operation takes place. The circuit includes a power rectifying section for rectifying the voltage input from an electrical outlet, a switching section for causing the output of the power rectifying section to be induced into the secondary side of a transformer with the switching time of the switching section being controlled by the feedback of the output power from the secondary of the transformer, a secondary rectifying section for rectifying and smoothing the voltage induced in the secondary side of the transformer, a feedback section for feeding back the output voltage of the secondary rectifying section to the switching section, and a reference voltage detection control section for adjusting the feedback amount of the feedback section by comparing the output voltage of the secondary rectifying section with a reference voltage. The circuit further include a microprocessor for outputting high or low signals in accordance with the state of the TV/VCR set, a monitor power control section for controlling the supply of voltage from the secondary rectifying section to a horizontal oscillating voltage terminal of a monitor of the set under the control of the microprocessor during a state when the monitor is turned off, a standby state or a programmed recording, and a standby state power control section controlling the feedback amount of the feedback section by forcibly dropping the output voltage of the secondary side under the control of the microprocessor during a standby state.

Semiconductor circuit and mos-dram

Abstract: PURPOSE:To speed up switching characteristics and the switching of sub- threshold current characteristics by enabling a switching means to switch the back gate bias potential of a MOS-FET to a first potential or a second potential. CONSTITUTION:FET Q1 and FETQ2 are allowed to achieve a sub-threshold current which is approximately equal to the conventional current when a potential Vpp which is higher than a power supply potential Vcc and a potential Vbb which is lower than a grounding potential Vss are applied to each back gate. Since the absolute value of a threshold potential becomes smaller when the power supply potential Vcc and the grounding potential Vss are applied to the back gate, a switching speed increases. Then, the sub-threshold current increases according to the ratio of time while a complementary MOS inverter 1 operates, but current increases only slightly when the operation time ratio is not large, thus increasing a switching speed.

High-performance single-mode fiber-optic switch.

Abstract: A piezoelectrically actuated four-port Mach-Zehnder switch with 30-micros switching time and 0.25-dB insertion loss is demonstrated at a wavelength of 1.3 microm. The worst-case cross talk is below -21 dB for an arbitrary input polarization. The process of fabricating the switch from commercial fiber couplers with length matching of the interferometer arms is described.

Reducing energy consumption of street lighting

Abstract: A process and switching device are disclosed for reducing energy consumption of street lighting networks, large lighting installations and the like that consist of several lighting appliances (7-9) having each at least one lamp (10-15). During a first time interval (T, T', T'') (total switching time), the networks or installations are connected to an energy source (1), and during a second predetermined time interval (t1+t2) within the total switching time (T-T'') the power of at least part of the lighting appliances (7, 9) is reduced. In order to dispense with supplementary control lines for reducing the power of the lighting appliances (7, 9), the lighting appliances (7, 9) are provided with a switching device (16, 17) that derives the corresponding switching signals from the total switching time (T) measured during a preceding period, for example the day before, taking into account the second predetermined time interval (t1+t2). Advantage is taken of the fact that the midway point between sunrise and sunset - which corresponds to half the total switching time (T/2) - is reached practically always at the same hour at a given degree of longitude. This hour, or an hour derived therefrom, is used as reference value To for determining corresponding switching signals.

High‐speed frequency‐switching synthesizer using fractional N phase‐locked loop

Abstract: A fractional N phase-locked loop frequency synthe sizer has been developed for small-size and low-power applications. It has fast frequency switching and low-phase noise. the fractional N-frequency synthesizer realizes fast switching by the high-frequency reference signal and by widening the loop bandwidth. However, when the bandwidth was widened, deterioration of phase noise is observed. Then the loop bandwidth which is necessary for fast frequency switching and which gives low-phase noise performance is determined. Based on these conditions, loop filter switching was studied which realized fast switching by widening the loop bandwidth and the low-phase noise performance by making the loop bandwidth narrow after the frequency switching. In the conventional filter switching, VCO control voltage fluctuates at the time of switching and the frequency switching time becomes longer. A new method is proposed which gives small switching fluctuation and which can shorten the frequency switching time. Finally, the synthesizer circuit in the 900-MHz band was fabricated and the lock-up time of 1.3 ms, the phase noise of -120 dBc/Hz at 50 kHz offset from carrier and spurious level of -83 dBc were obtained.

Method of programming a frequency synthesizer

Abstract: In order to program the output frequency of a synthesizer such as that of a two-way radio, first the reference oscillator is warped or tuned substantially to one limit of its tuning range. The "N" divisor of the synthesizer dividor is then selected to produce a loop output close to the desired loop output frequency. The reference oscillator is then tuned to provide the desired loop output frequency.

Field-effect-transistor self-electro-optic-effect-device (FET-SEED) electrically addressed differential modulator array

Abstract: We describe a 6 × 6 array of electrically addressed field-effect-transistor self-electro-optic-effect-device differential modulators in which each element has a single-stage amplifier to permit an input voltage of less than 1 V to control the output modulators, which can operate at as high as 10 V. The variations in the switching voltages across the array are less than ±70 mV, and the individual array elements are operated at as high as 2 Gbits/s. We also measure cross talk between adjacent elements within the array, measure the dependence of the switching time on the input voltage swing, and calculate the dependence of the switching time that is due to the photocurrent of the modulators.

Switching Experiments with a Mach-Zehnder-type All-Optical Device Based on the Band-Filling Nonlinearity in a GaAs Waveguide and Reduction in Its Relaxation Time

Abstract: We examine switching characteristics of an all-optical device in Mach-Zehnder configuration, that is based on the band-filling nonlinearity in a GaAs waveguide. Switching waveforms corresponding to π (full switching), 2π, and 2.7π have been obtained and they were compared with theoretical curves. Good agreement has been observed between experimental and theoretical results. The control light pulse energy required for full switching is estimated to be approximately 6 pJ. The switching speed of the above device is limited by the slow relaxation time of photogenerated carriers. In order to reduce the switch-off time determined by the carrier relaxation, we investigated a method which involves application of a DC electric field across the thin core layer of the waveguide in order to sweep photogenerated carriers away from the light-guiding region and effectively reduce the relaxation time. With this technique, the usual switching speed of approximately 1 ns was reduced to approximately 24 ps.

i Characterization of High Power IGBT's With Sinewave Current

Abstract: The IGBT's characteristics are examined in a sin- gle-pulse series resonant circuit under controlled temperature. The aim being to reach the highest possible switching frequency for IGBT's with ratings suitable for industrial use, it is found that both switching energy and on-state losses must be mea- sured, as on-state losses also vary with frequency. It is also found that IGBTs, though having the same datasheet rating, can have properties depending on the manufacturers philosophy giving them totally different behavior at high frequencies. The time needed for the conductivity modulation mechanism to get into action is crucial, giving advantages to devices from manu- facturers using low carrier lifetime and high bipolar emitter efficiency, such as Toshiba. The same datasheet ratings both in current, voltage and switching speed can be achieved with high carrier lifetime and low bipolar emitter efficiency, like Siemens devices, which in the resonant circuit will have their advantages under other modes of operation than Toshiba. ,

Sense amplifier with feedback and stabilization

Abstract: The present invention is a sense amplifier circuit for use with programmable logic devices, that provides improved switching time by actively limiting the voltage swing on the bit line which it is sensing, rather than passively sensing the voltage, and that employs feedback circuits to further improve switching time. Voltage reference control circuitry, comprising variable current limiters controlled by the potential of a supply of reference potential, can be added to improve noise immunity. The circuitry of the supply of reference potential is designed so that its sensitivity to fabrication variations is substantially similar to that of the sense amplifier and so that it adjusts the reference potential accordingly.

Fast and stable frequency switching employing a delayed self-duplex (DSD) light source

Abstract: A novel frequency-agile light source, the delayed self-duplex (DSD) light source, is constructed using a tunable DBR laser and an optical switch. The DSD light source overcomes the tuning speed limitation of the tunable laser, and also offers suppressed frequency drift due to the thermal effect by employing periodic laser tuning. For 160-GHz-spaced frequency switching, the 4-ns switching time and 2.2-GHz thermal frequency drift inherent to the DBR laser are reduced to 0.4 ns and 0.3 GHz, respectively. >

Development of a High-Speed Solenoid Valve

Abstract: Development of a solenoid which was used for the high-speed solenoidvalve with a 1 ms switching time is discussed in this paper.First, by using the mathematical model, we quantitatively studied the effects of design particu lars, such as the dimensions of the solenoids and the number of turns of coil, on the switching time. Next, we investigated the suitable and comprehensive conditions that would satisfy given specifications under the various limitations inherent in the solenoid valve's operation.Finally we manufactured the solenoid valves in accordance with the effective methods for performing fast switching, and evaluated their performance.

Operation Characteristics of a Side-Light-Injection Multiple-Quantum-Well Bistable Laser for All-Optical Switching

Abstract: An InGaAs/InAlAs side-light-injection multiple-quantum-well bistable laser for all-optical switching has been developed. It consists of one main bistable laser and two waveguides perpendicular to the main laser. Saturable absorption and gain quenching are used for set and reset operations. The voltages applied to the gain quenching and saturable absorption regions, which are located at the intersections of the main laser and the waveguide regions, are +1.00 and +0.29 V, respectively. As the input light intensity ( 1.55 µm range) increases, the turn-on and turn-off times decrease. The turn-on time is 200 ps when the input light peak intensity is 1 mW and the turn-off time is 2 ns when the input light peak intensity is 200 mW. The experimental results are supported by numerical simulation. Higher differential gain material is expected to enable faster switching speed.