887 research outputs found
Methods for Determining Blood Flow Through Intact Vessels of Experimental Animals Under Conditions of Gravitational Stress and in Extra-terrestrial Space Capsules Final Report, 1 Nov. 1960 - 31 Dec. 1964
Electromagnetic blood flow meter to determine blood flow through intact vessels of test animals in gravitational stress and in extraterrestrial space capsule
Efficiency Improvement of LDO Output Based Linear Regulator With Supercapacitor Energy Recovery – A versatile new technique with an example of a 5V to 1.5V version
Supercapacitors are used in various industrial applications and the supercapacitors technology is gradually progressing into a mature state. Common applications of supercapacitors are in electric vehicles, hybrid electric vehicles, uninterruptible power supply (UPS) and in portable devices such as cellular phones and laptops. The capacitance values range from fractional Farads to few thousand Farads and their continuos DC voltage ratings are from 2V to 6V. At University of Waikato, a team works on using supercapacitors for improving the efficiency of linear voltage regulators. In particular, this patented technique aims at combining off the shelfs LDO ICs and a supercapacitor array for improving end to end efficiency of linear regulator. My work is aimed at developing the theoretical background and designing prototype circuitry for a voltage regulator for the case of unregulated input supply is more than 3 times of the minimum input voltage requirement of the LDO which is applicable for a 5V to 1.5V regulator. Experimental results are indicated with future suggestions for improvement
Süsteemi arhitektuur ning komponentide valimine ESTCube-2 toitealamsüsteemi jaoks
This thesis is focused on the architecture of the electrical power system (EPS) and implementations of the various subsystems within the EPS for ESTCube-2 nanosatellite. The main goals are to establish a high level system architecture compatible with the rest of the satellite and investigate solutions for the battery management and protection (BMPS) and the voltage conversion and power distribution systems (VCPDS).
In this work, an overview is given of the ESTCube-2 mission and the satellite’s architecture. Based on the satellite architecture, requirements are set for the EPS subsystems to be investigated. For the BMPS, two hot-swap controller based solutions are investigated, prototyped and tested. For the VCPDS, two load switch designs are evaluated, six different voltage converters are characterized and solutions for the power distribution system are proposed. Based on the testing results, recommendations are made for the final implementation
DESIGN OF ONCHIP LOW DROPOUT (LDO) REGULATOR FOR POWER MANAGEMENT APPLICATION
A low dropout regulator is proposed in this paper. The regulator is designed with classic five pack model to decrease the number of devices and make the design compact and also reduce the power consumption. The system is designed and simulated in cadence virtuoso environment under 180nm technology node. Three models of LDO is proposed in this paper, with all having same error amplifier but with small variations. The advantages and disadvantages of each model will be discussed in the paper. The LDOs have linear characteristic over a good input range. It has good transient response to load variation.Â
Modularizing the LDO to optimize performance based on application design constraints
This thesis aims to construct a modular low-dropout regulator that gives designers more freedom in building a highly efficient regulator that meets application demands. This modular design is able to separate DC regulation and high-frequency supply rejection while not compromising on either of the two. Flexibility is a key requirement during both design and post-design. The proposed regulator is able to achieve all the required goals with full spectrum power supply rejection. By splitting the pass device, this design is able to achieve the best of both internal pole dominant and external pole dominant linear regulators
Fast high--voltage amplifiers for driving electro-optic modulators
We describe five high-voltage (60 to 550V peak to peak), high-speed (1-300ns
rise time; 1.3-300MHz bandwidth) linear amplifiers for driving capacitive or
resistive loads such as electro-optic modulators. The amplifiers use bipolar
transistors in various topologies. Two use electron tubes to overcome the speed
limitations of high-voltage semiconductors. All amplifiers have been built.
Measured performance data is given for each.Comment: 9pages, 6figures, 6tables, to appear in Review of Scientific
Instrument
Designing an ultra low quiescent current buck switching regulator
Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2008.Includes bibliographical references (p. 119-120).The new buck regulator proposed in this thesis was designed to operate with only a few micro-amps of supply current during no load output conditions, while maintaining low output voltage ripple. The regulator also has high efficiency for current loads above an amp to make the converter useful in a variety of applications. The specifications will be achieved by implementing a control scheme similar to the one used in the LT3481 buck regulator. The converter will use burst mode, pulse frequency modulation, and pulse width modulation to achieve control over the entire load range. The capabilities of a full BiCMOS process technology will be taken advantage of to enable implementation of good control dynamics at low currents. This micropower buck regulator was designed, fabricated, and tested in silicon to measure its characteristics as compared to simulation and desired specifications.by John Underhill Gardner.M.Eng
An accurate, trimless, high PSRR, low-voltage, CMOS bandgap reference IC
Bandgap reference circuits are used in a host of analog, digital, and mixed-signal systems to establish an accurate voltage standard for the entire IC. The accuracy of the bandgap reference voltage under steady-state (dc) and transient (ac) conditions is critical to obtain high system performance. In this work, the impact of process, power-supply, load, and temperature variations and package stresses on the dc and ac accuracy of bandgap reference circuits has been analyzed. Based on this analysis, the a bandgap reference that
1. has high dc accuracy despite process and temperature variations and package stresses, without resorting to expensive trimming or noisy switching schemes,
2. has high dc and ac accuracy despite power-supply variations, without using large off-chip capacitors that increase bill-of-material costs,
3. has high dc and ac accuracy despite load variations, without resorting to error-inducing buffers,
4. is capable of producing a sub-bandgap reference voltage with a low power-supply, to enable it to operate in modern, battery-operated portable applications,
5. utilizes a standard CMOS process, to lower manufacturing costs, and
6. is integrated, to consume less board space
has been proposed.
The functionality of critical components of the system has been verified through prototypes after which the performance of the complete system has been evaluated by integrating all the individual components on an IC.
The proposed CMOS bandgap reference can withstand 5mA of load variations while generating a reference voltage of 890mV that is accurate with respect to temperature to the first order. It exhibits a trimless, dc 3-sigma accuracy performance of 0.84% over a temperature range of -40°C to 125°C and has a worst case ac power-supply ripple rejection (PSRR) performance of 30dB up to 50MHz using 60pF of on-chip capacitance. All the proposed techniques lead to the development of a CMOS bandgap reference that meets the low-cost, high-accuracy demands of state-of-the-art System-on-Chip environments.Ph.D.Committee Chair: Rincon-Mora, Gabriel; Committee Member: Ayazi, Farrokh; Committee Member: Bhatti, Pamela; Committee Member: Leach, W. Marshall; Committee Member: Morley, Thoma
Design of Analog CMOS Circuits for Batteryless Implantable Telemetry Systems
A wireless biomedical telemetry system is a device that collects biomedical signal measurements and transmits data through wireless RF communication. Testing medical treatments often involves experimentation on small laboratory animals, such as genetically modified mice and rats. Using batteries as a power source results in many practical issues, such as increased size of the implant and limited operating lifetime. Wireless power harvesting for implantable biomedical devices removes the need for batteries integrated into the implant. This will reduce device size and remove the need for surgical replacement due to battery depletion. Resonant inductive coupling achieves wireless power transfer in a manner modelled by a step down transformer. With this methodology, power harvesting for an implantable device is realized with the use of a large primary coil external to the subject, and a smaller secondary coil integrated into the implant. The signal received from the secondary coil must be regulated to provide a stable direct current (DC) power supply, which will be used to power the electronics in the implantable device. The focus of this work is on development of an electronic front-end for wireless powering of an implantable biomedical device. The energy harvesting front-end circuit is comprised of a rectifier, LDO regulator, and a temperature insensitive voltage reference. Physical design of the front-end circuit is developed in 0.13um CMOS technology with careful attention to analog layout issues. Post-layout simulation results are presented for each sub-block as well as the full front-end structure. The LDO regulator operates with supply voltages in the range of 1V to 1.5V with quiescent current of 10.5uA The complete power receiver front-end has a power conversion efficiency of up to 29%
Stability improvement of power system using UPFC
Occurrence of a fault in a power system causes transients. To stabilize the system, Power System Stabilizer (PSS) and Automatic Voltage Regulator (AVR) are used. Load flow analysis is done to analyze the transients introduced in the system due to the occurrence of faults. The Flexible Alternating Current Transmission (FACTS) devices such as UPFC are becoming important in suppressing power system oscillations and improving system damping. The UPFC is a solid-state device, which can be used to control the active and reactive power. This thesis considers a typical three- machine nine-bus system as a case study for investigating the performance of UPFC is achieving stability. By using a UPFC the oscillation introduced by the faults, the rotor angle and speed deviations can be damped out quickly than a system without a UPFC. The effectiveness of UPFC in suppressing power system oscillation is investigated by analyzing their oscillation in rotor angle and change in speed occurred in the three machine system considered in this work. A proportional integral (PI) controller has been employed for the UPFC. It is also shown that a UPFC can control independently the real and reactive power flow in a transmission line. A MATLAB simulation has been carried out to demonstrate the performance of the UPFC in achieving transient stability of the three-machine nine-bus system
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