Response of tantalum capacitors to fast transient overvoltages

Report describes tests used to determine minimum time for capacitors to fail due to overvoltage and maximum amount of overvoltage that capacitors could sustain without permanent damage

Charge and spin dynamics in interacting quantum dots

The transient response of a quantum dot with strong Coulomb interaction to a fast change in the gate potential, as well as the stationary ac-response to a slow harmonic variation of the gate potential are computed by means of a real-time diagrammatic expansion in the tunnel-coupling strength. We find that after a fast switching, the relaxation of charge and spin are governed by a single time constant each, which differ from each other due to Coulomb repulsion. We compare the response to a step potential with the $RC$ time extracted from the ac response.Comment: 5 pages, 3 figures, published versio

STEPPING INDUCTOR FOR FAST TRANSIENT RESPONSE OF SWITCHING CONVERTER

A fast transient response converter is disclosed which makes use of stepping inductor in a switching converter to speed up output voltage response under fast transient condition. The inductive element in a switching converter is replaced by two series or parallel inductive elements, one of which has a smaller value of inductance than the other. During the fast transient period, the inductor with larger inductance value will be shorted to a voltage source. The total inductance will be greatly reduced and thus allows rapid current change during the transient change.published_or_final_versio

STEPPING INDUCTOR FOR FAST TRANSIENT RESPONSE OF SWITCHING CONVERTER

A fast transient response converter is disclosed which makes use of stepping inductor in a switching converter to speed up output voltage response under fast transient condition. The inductive element in a switching converter is replaced by two series or parallel inductive elements, one of which has a smaller value of inductance than the other. During the fast transient period, the inductor with larger inductance value will be shorted to a voltage source. The total inductance will be greatly reduced and thus allows rapid current change during the transient change.published_or_final_versio

Zero overshoot and fast transient response using a fuzzy logic controller

In some industrial process control systems it is desirable not to allow an overshoot beyond the setpoint or a threshold, this could be a safety constraint or the requirement of the system. This paper outlines our work in designing a fuzzy PID controller to achieve a step-response with zero overshoot while improving the output transient response. Our designed fuzzy PID controller is applied to stable, marginally stable and unstable systems and their step responses are compared with a tuned conventional PID controller. A comparative case study shows that the proposed fuzzy controller is highly effective and outperforms the PID controller in achieving a zero overshoot response and enhancing the output transient response

Rotor response for transient unbalance changes in a nonlinear simulation

Transient unbalance shifts were determined not to excite a rotor instability in the high pressure turbomachinery of the Space Shuttle Main Engine using the current rotor dynamic models. Sudden unbalance changes of relatively small magnitudes during fast-speed ramps showed stable nonsynchronous motion depending on the resultant unbalance distribution at subsequent high speed dwells. Transient moment unbalance may initiate a limit cycle subsynchronous response that shortly decays, but a persistent subsynchronous with large amplitudes was never achieved. These limit cycle subsynchronous amplitudes appear to be minimized with lower unbalance magnitudes, which indicates improved rotor balancing would sustain synchronous motion only. The transient unbalance phenomenon was determined to be an explanation for synchronous response shifts often observed during engine tests

Eroding ribbon thermocouples: impulse response and transient heat flux analysis

We have investigated a particular type of fast-response surface thermocouple to determine if it is appropriate to use a one dimensional transient heat conduction model to derive the transient surface heat flux from the measurements of surface temperature. With these sensors, low thermal inertia thermocouple junctions are formed near the surface by abrasive wear. Using laser excitation, we obtained the impulse response of these commercially available devices. The response of particular sensors can vary if new junctions are created by abrasive wear. Furthermore, the response of these sensors was found to deviate substantially from the one dimensional model and varied from sensor to sensor. The impulse response was simulated with greater fidelity using a two dimensional finite element model, but three dimensional effects also appear to be significant. The impact of these variations on the derived heat flux is assessed for the case of measurements in an internal combustion engine. When the measured impulse response is used to derive the surface heat flux, the apparent reversal of heat flux during the expansion stroke does not occur

STUDY OF FULLY-INTEGRATED LOW-DROPOUT REGULATORS

Department of Electrical EngineeringThis thesis focuses on the introduction of fully-integrated low-dropout regulators (LDOs). Recently, for the mobile and internet-of-things applications, the level of integration is getting higher. LDOs get popular in integrated circuit design including functions such as reducing switching ripples from high-efficiency regulators, cancelling spurs from other loads, and giving different supply voltages to loads. In accordance with load applications, choosing proper LDOs is important. LDOs can be classified by the types of power MOSEFT, the topologies of error amplifier, and the locations of dominant pole. Analog loads such as voltage-controlled oscillators and analog-to-digital converters need LDOs that have high power-supply-rejection-ratio (PSRR), high accuracy, and low noise. Digital loads such as DRAM and CPU need fast transient response, a wide range of load current providable LDOs. As an example, we present the design procedure of a fully-integrated LDO that obtains the desired PSRR. In analog LDOs, we discuss advanced techniques such as local positive feedback loop and zero path that can improve stability and PSRR performance. In digital LDOs, the techniques to improve transient response are introduced. In analog-digital hybrid LDOs, to achieve both fast transient and high PSRR performance in a fully-integrated chip, how to optimally combine analog and digital LDOs is considered based on the characteristics of each LDO type. The future work is extracted from the considerations and limitations of conventional techniques.clos