Voltage drop

About: Voltage drop is a research topic. Over the lifetime, 15877 publications have been published within this topic receiving 119122 citations.

An investigation of surface states at a silicon/silicon oxide interface employing metal-oxide-silicon diodes

Abstract: A new solid-state device, the M-O-S diode, of which an oxidized silicon surface is an integral part, is introduced, and a theory for its operation in the absence of surface states is obtained. The capacitance of this device may be considerably more voltage sensitive than that of a p-n junction. The existence of surface states with non-zero relaxation times is introduced into the theoretical model. It is shown that the states may increase the capacitance of the device, as well as affect the proportion of applied voltage which appears across the silicon. A small-signal equivalent circuit is derived which includes the effect of the surface states. It is also shown that a comparison of the theoretical capacitance vs. voltage curve without states and a measured high-frequency capacitance vs. voltage curve may be used to obtain the distribution of all states, regardless of their time constants. Results are given of measurements and calculations on two M-O-S diodes having different surface treatments before oxidation. Both surfaces have a total density of about 3 × 10 12 states/cm 2 . In both cases, the distribution of states is continuous and has its highest peak about 100 mV above E F (0), the position of the Fermi level at the silicon surface if there is no voltage drop across the silicon The time constants of the states extend from 10 −8 sec to longer than 10 −2 sec. There is a tendency for states located at deeper energy levels to have longer time constants, but some of the states in the high density of states above E F (0) have long time constants. The distribution of time constants with energy level is somewhat different for the two surfaces. A comparison is made between the distribution of states obtained here with the distribution reported by others working in the field. The results are similar in density and location of the peaks of the distribution reported here, but differ in that some other sources report a discrete distribution.

A New Battery/UltraCapacitor Hybrid Energy Storage System for Electric, Hybrid, and Plug-In Hybrid Electric Vehicles

Abstract: In this paper, a new battery/ultracapacitor hybrid energy storage system (HESS) is proposed for electric drive vehicles including electric, hybrid electric, and plug-in hybrid electric vehicles. Compared to the conventional HESS design, which uses a larger dc/dc converter to interface between the ultracapacitor and the battery/dc link to satisfy the real-time peak power demands, the proposed design uses a much smaller dc/dc converter working as a controlled energy pump to maintain the voltage of the ultracapacitor at a value higher than the battery voltage for the most city driving conditions. The battery will only provide power directly when the ultracapacitor voltage drops below the battery voltage. Therefore, a relatively constant load profile is created for the battery. In addition, the battery is not used to directly harvest energy from the regenerative braking; thus, the battery is isolated from frequent charges, which will increase the life of the battery. Simulation and experimental results are presented to verify the proposed system.

Robust Droop Controller for Accurate Proportional Load Sharing Among Inverters Operated in Parallel

Abstract: In this paper, the inherent limitations of the conventional droop control scheme are revealed. It has been proven that parallel-operated inverters should have the same per-unit impedance in order for them to share the load accurately in proportion to their power ratings when the conventional droop control scheme is adopted. The droop controllers should also generate the same voltage set-point for the inverters. Both conditions are difficult to meet in practice, which results in errors in proportional load sharing. An improved droop controller is then proposed to achieve accurate proportional load sharing without meeting these two requirements and to reduce the load voltage drop due to the load effect and the droop effect. The load voltage can be maintained within the desired range around the rated value. The strategy is robust against numerical errors, disturbances, noises, feeder impedance, parameter drifts and component mismatches. The only sharing error, which is quantified in this paper, comes from the error in measuring the load voltage. When there are errors in the voltage measured, a fundamental tradeoff between the voltage drop and the sharing accuracy appears. It has also been explained that, in order to avoid errors in power sharing, the global settings of the rated voltage and frequency should be accurate. Experimental results are provided to verify the analysis and design.

Influence of Electrical Potential Distribution, Charge Transport, and Recombination on the Photopotential and Photocurrent Conversion Efficiency of Dye-Sensitized Nanocrystalline TiO2 Solar Cells: A Study by Electrical Impedance and Optical Modulation Techniques

Abstract: The role of electrical potential, charge transport, and recombination in determining the photopotential and photocurrent conversion efficiency (IPCE) of dye-sensitized nanocrystalline solar cells was studied. Electrostatic arguments and electrical impedance spectroscopy (EIS) are used to obtain information on the electrical and electrochemical potential distribution in the cell. It is shown that on the macroscopic level, no significant electrical potential drop exists within the porous TiO2 when it contacts the electrolyte and that the electrical potential drop at the transparent conducting oxide substrate (TCO)/TiO2 interface occurs over a narrow region, one or two layers of TiO2. Analyses of EIS and other data indicate that both the photopotential of the cell and the decrease of the electrical potential drop across the TCO/TiO2 interface are caused by the buildup of photoinjected electrons in the TiO2 film. The time constants for the recombination and collection of the photoinjected electrons are measur...

Digital wireless position sensor

Abstract: A method is provided for tracking an object, including positioning a radio frequency (RF) driver to radiate an RF driving field toward the object, and fixing to the object a wireless transponder that includes a power coil and at least one sensor coil. The method also includes receiving the RF driving field using the power coil and storing electrical energy derived therefrom. A plurality of field generators are driven to generate electromagnetic fields at respective frequencies in a vicinity of the object that induce a voltage drop across the at least one sensor coil. A digital output signal is generated at the wireless transponder indicative of the voltage drop across the sensor coil, and the generation of the digital output signal is powered using the stored electrical energy. The digital output signal is transmitted from the wireless transponder using the power coil, and the transmission of the digital output signal is powered using the stored electrical energy. The digital output signal is received and processed to determine coordinates of the object.