Matching Items (5)
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- All Subjects: Audio amplifiers--Design and construction.
- All Subjects: Point-of-care
- Genre: Masters Thesis
- Creators: Ozev, Sule
- Creators: Chakraborty, Bijeta
- Creators: Peterson, Cory
- Member of: ASU Electronic Theses and Dissertations
- Resource Type: Text
Description
Efficiency of components is an ever increasing area of importance to portable applications, where a finite battery means finite operating time. Higher efficiency devices need to be designed that don't compromise on the performance that the consumer has come to expect. Class D amplifiers deliver on the goal of increased efficiency, but at the cost of distortion. Class AB amplifiers have low efficiency, but high linearity. By modulating the supply voltage of a Class AB amplifier to make a Class H amplifier, the efficiency can increase while still maintaining the Class AB level of linearity. A 92dB Power Supply Rejection Ratio (PSRR) Class AB amplifier and a Class H amplifier were designed in a 0.24um process for portable audio applications. Using a multiphase buck converter increased the efficiency of the Class H amplifier while still maintaining a fast response time to respond to audio frequencies. The Class H amplifier had an efficiency above the Class AB amplifier by 5-7% from 5-30mW of output power without affecting the total harmonic distortion (THD) at the design specifications. The Class H amplifier design met all design specifications and showed performance comparable to the designed Class AB amplifier across 1kHz-20kHz and 0.01mW-30mW. The Class H design was able to output 30mW into 16Ohms without any increase in THD. This design shows that Class H amplifiers merit more research into their potential for increasing efficiency of audio amplifiers and that even simple designs can give significant increases in efficiency without compromising linearity.
ContributorsPeterson, Cory (Author) / Bakkaloglu, Bertan (Thesis advisor) / Barnaby, Hugh (Committee member) / Kiaei, Sayfe (Committee member) / Arizona State University (Publisher)
Created2013
Description
Class D Amplifiers are widely used in portable systems such as mobile phones to achieve high efficiency. The demands of portable electronics for low power consumption to extend battery life and reduce heat dissipation mandate efficient, high-performance audio amplifiers. The high efficiency of Class D amplifiers (CDAs) makes them particularly attractive for portable applications. The Digital class D amplifier is an interesting solution to increase the efficiency of embedded systems. However, this solution is not good enough in terms of PWM stage linearity and power supply rejection. An efficient control is needed to correct the error sources in order to get a high fidelity sound quality in the whole audio range of frequencies. A fundamental analysis on various error sources due to non idealities in the power stage have been discussed here with key focus on Power supply perturbations driving the Power stage of a Class D Audio Amplifier. Two types of closed loop Digital Class D architecture for PSRR improvement have been proposed and modeled. Double sided uniform sampling modulation has been used. One of the architecture uses feedback around the power stage and the second architecture uses feedback into digital domain. Simulation & experimental results confirm that the closed loop PSRR & PS-IMD improve by around 30-40 dB and 25 dB respectively.
ContributorsChakraborty, Bijeta (Author) / Bakkaloglu, Bertan (Thesis advisor) / Garrity, Douglas (Committee member) / Ozev, Sule (Committee member) / Arizona State University (Publisher)
Created2012
Description
Point of Load (PoL) converters are important components to the power distribution system in computer power supplies as well as automotive, space, nuclear, and medical electronics. These converters often require high output current capability, low form factor, and high conversion ratios (step-down) without sacrificing converter efficiency. This work presents hybrid silicon/gallium nitride (CMOS/GaN) power converter architectures as a solution for high-current, small form-factor PoL converters. The presented topologies use discrete GaN power devices and CMOS integrated drivers and controller loop. The presented power converters operate in the tens of MHz range to reduce the form factor by reducing the size of the off-chip passive inductor and capacitor. Higher conversion ratio is achieved through a fast control loop and the use of GaN power devices that exhibit low parasitic gate capacitance and minimize pulse swallowing.
This work compares three discrete buck power converter architectures: single-stage, multi-phase with 2 phases, and stacked-interleaved, using components-off-the-shelf (COTS). Each of the implemented power converters achieves over 80% peak efficiency with switching speeds up-to 10MHz for high conversion ratio from 24V input to 5V output and maximum load current of 10A. The performance of the three architectures is compared in open loop and closed loop configurations with respect to efficiency, output voltage ripple, and power stage form factor.
Additionally, this work presents an integrated CMOS gate driver solution in CMOS 0.35um technology. The CMOS integrated circuit (IC) includes the gate driver and the closed loop controller for directly driving a single-stage GaN architecture. The designed IC efficiently drives the GaN devices up to 20MHz switching speeds. The presented controller technique uses voltage mode control with an innovative cascode driver architecture to allow a 3.3V CMOS devices to effectively drive GaN devices that require 5V gate signal swing. Furthermore, the designed power converter is expected to operate under 400MRad of total dose, thus enabling its use in high-radiation environments for the large hadron collider at CERN and nuclear facilities.
This work compares three discrete buck power converter architectures: single-stage, multi-phase with 2 phases, and stacked-interleaved, using components-off-the-shelf (COTS). Each of the implemented power converters achieves over 80% peak efficiency with switching speeds up-to 10MHz for high conversion ratio from 24V input to 5V output and maximum load current of 10A. The performance of the three architectures is compared in open loop and closed loop configurations with respect to efficiency, output voltage ripple, and power stage form factor.
Additionally, this work presents an integrated CMOS gate driver solution in CMOS 0.35um technology. The CMOS integrated circuit (IC) includes the gate driver and the closed loop controller for directly driving a single-stage GaN architecture. The designed IC efficiently drives the GaN devices up to 20MHz switching speeds. The presented controller technique uses voltage mode control with an innovative cascode driver architecture to allow a 3.3V CMOS devices to effectively drive GaN devices that require 5V gate signal swing. Furthermore, the designed power converter is expected to operate under 400MRad of total dose, thus enabling its use in high-radiation environments for the large hadron collider at CERN and nuclear facilities.
ContributorsHegde, Ashwath (Author) / Kitchen, Jennifer (Thesis advisor) / Bakkaloglu, Bertan (Committee member) / Ozev, Sule (Committee member) / Arizona State University (Publisher)
Created2018
Description
Portable health diagnostic systems seek to perform medical grade diagnostics in non-ideal environments. This work details a robust fault tolerant portable health diagnostic design implemented in hardware, firmware and software for the detectionof HPV in low-income countries. The device under device under test (DUT) is a fluorescence based lateral flow assay (LFA) point-of-care (POC) device. This work’s contributions are: firmware and software development, calibration routine implementation, device performance characterization and a proposed method of in-software fault detection. Firmware was refactored from the original implementation of the POC fluorescence reader to expose an application programming interface (API) via USB. Companion software available for desktop environments (Windows, Mac and Linux) was created to interface with this firmware API and conduct macro level routines to request and receive fluorescence data while presenting a user-friendly interface to clinical technicians. Lastly, an environmental chamber was constructed to conduct sequential diagnostic reads in order to observe sensor drift and other deviations that might present themselves in real-world usage. The results from these evaluations show a standard deviation of less than 1% in fluorescence readings in nominal temperature environments (approx. 25C) suggesting that this system will have a favorable signal-to-noise (SNR) ratio in such a setting. In non-ideal over heated environments (≥38C), the evaluation results showed performance degradation with standard deviations as large as 15%.
ContributorsLue Sang, Christopher David (Author) / Blain Christen, Jennifer M (Thesis advisor) / Ozev, Sule (Committee member) / Goryll, Michael (Committee member) / Raupp, Gregory (Committee member) / Arizona State University (Publisher)
Created2022
Description
Point-of-Care diagnostics is one of the most popular fields of research in bio-medicine today because of its portability, speed of response, convenience and quality assurance. One of the most important steps in such a device is to prepare and purify the sample by extracting the nucleic acids, for which small spherical magnetic particles called magnetic beads are often used in laboratories. Even though magnetic beads have the ability to isolate DNA or RNA from bio-samples in their purified form, integrating these into a microfluidic point-of-need testing kit is still a bit of a challenge. In this thesis, the possibility of integrating paramagnetic beads instead of silica-coated dynabeads, has been evaluated with respect to a point-of-need SARS-CoV-2 virus testing kit. This project is a comparative study between five different sizes of carboxyl-coated paramagnetic beads with reference to silica-coated dynabeads, and how each of them behave in a microcapillary chip in presence of magnetic fields of different strengths. The diameters and velocities of the beads have been calculated using different types of microscopic imaging techniques. The washing and elution steps of an extraction process have been recreated using syringe pump, microcapillary channels and permanent magnets, based on which those parameters of the beads have been studied which are essential for extraction behaviour. The yield efficiency of the beads have also been analysed by using these to extract Salmon DNA. Overall, furthering this research will improve the sensitivity and specificity for any low-cost nucleic-acid based point-of-care testing device.
ContributorsBiswas, Shilpita (Author) / Christen, Jennifer B (Thesis advisor) / Ozev, Sule (Committee member) / Goryll, Michael (Committee member) / Arizona State University (Publisher)
Created2021