657 research outputs found
SIMO DC-DC Converter for Automotive Audio Amplifier
No full textModern auto industry is ubiquitously deploying electronic systems for several applications like control, infotainment and security among others in the vehicles. Automotive infotainment is a key segment for the growth of automotive electronics as the vehicles, both light and heavy, require radio, video, navigation-assistance and telematics systems for both entertainment and networking.
Like any battery-operated systems, the automotive infotainment systems are required to provide high efficiency. One major constituent of in-vehicle infotainment being the radio, improving the overall efficiency of a car radio system is emphasized by the industry. In the state-of-the-art, the automotive audio amplifiers severely lack efficiency offering <40% in the mute condition. This research targets to improve the overall efficiency of an audio amplifier in a car radio by power supplying efficiently.
A Single Inductor Multiple Output dc-dc converter is explored as a supply voltage generator for an automotive audio amplifier in a car radio. The presence of line and load fluctuations, together with wide range of operating temperatures, in the automotive environment pose major challenge to the voltage regulation. A systematic feasibility study and analysis of specifications brought out the equivalence between the target SIMO converter and a non-inverting buck-boost SISO converter. Based on the equivalence, equilibrium and small signal models for the SIMO converter are developed. A voltage-mode, error-based controller is designed to control the dynamics of the converter. A novel power switching stage is conceived to generate the supplies required in a multi-channel class-D power amplifier. The switch
configuration is critical due the absence of a well-defined reference to one of the regulated outputs and the effect of package parasitics at high switching frequencies. The converter is charged synchronously and discharged quasi-synchronously to the loads. The switches are configured and driven optimally based on extensive simulations in the presence of package models to suppress the switching noise. In order to reduce the EM interference in the AM band of interest, the SIMO converter is switched at permissible high frequencies based on the EMI mask.
The automotive-class SIMO dc-dc converter is designed and integrated with a state-of-the-art class-D audio amplifier using 110nm BCD process technology offered by STMicroelectronics. The SIMO converter provides a battery tracking boost and a ground referred buck outputs for driving the class-D power stage. A unique feature of the converter is the generation of a floating voltage across half battery to supply the DSP core of the amplifier. The converter starts-up as boost converter alone followed entering boost-assisted SIMO converter mode. The active area occupied is 2.5mm2. The switching frequency is 2-2.4MHz. The converter has a load capability to drive up to 4 channels of a class-D power stage with peak efficiency of 86% and peak output power of 2.8W. The ripple voltage on the regulated outputs is below 25mV. The SIMO converter is able to sustain the automotive battery crank and dump conditions across the battery variation range of 4.5-27V. A line regulation of 6.3-16.2mV/V and a load regulation of 0.16mV/mA are provided by the SIMO converter. In the presence of wide range of battery variations, the SIMO converter incorporates all the necessary protections circuits and under/over voltage interrupts through I2C communication.Modern auto industry is ubiquitously deploying electronic systems for several applications like control, infotainment and security among others in the vehicles. Automotive infotainment is a key segment for the growth of automotive electronics as the vehicles, both light and heavy, require radio, video, navigation-assistance and telematics systems for both entertainment and networking.
Like any battery-operated systems, the automotive infotainment systems are required to provide high efficiency. One major constituent of in-vehicle infotainment being the radio, improving the overall efficiency of a car radio system is emphasized by the industry. In the state-of-the-art, the automotive audio amplifiers severely lack efficiency offering <40% in the mute condition. This research targets to improve the overall efficiency of an audio amplifier in a car radio by power supplying efficiently.
A Single Inductor Multiple Output dc-dc converter is explored as a supply voltage generator for an automotive audio amplifier in a car radio. The presence of line and load fluctuations, together with wide range of operating temperatures, in the automotive environment pose major challenge to the voltage regulation. A systematic feasibility study and analysis of specifications brought out the equivalence between the target SIMO converter and a non-inverting buck-boost SISO converter. Based on the equivalence, equilibrium and small signal models for the SIMO converter are developed. A voltage-mode, error-based controller is designed to control the dynamics of the converter. A novel power switching stage is conceived to generate the supplies required in a multi-channel class-D power amplifier. The switch
configuration is critical due the absence of a well-defined reference to one of the regulated outputs and the effect of package parasitics at high switching frequencies. The converter is charged synchronously and discharged quasi-synchronously to the loads. The switches are configured and driven optimally based on extensive simulations in the presence of package models to suppress the switching noise. In order to reduce the EM interference in the AM band of interest, the SIMO converter is switched at permissible high frequencies based on the EMI mask.
The automotive-class SIMO dc-dc converter is designed and integrated with a state-of-the-art class-D audio amplifier using 110nm BCD process technology offered by STMicroelectronics. The SIMO converter provides a battery tracking boost and a ground referred buck outputs for driving the class-D power stage. A unique feature of the converter is the generation of a floating voltage across half battery to supply the DSP core of the amplifier. The converter starts-up as boost converter alone followed entering boost-assisted SIMO converter mode. The active area occupied is 2.5mm2. The switching frequency is 2-2.4MHz. The converter has a load capability to drive up to 4 channels of a class-D power stage with peak efficiency of 86% and peak output power of 2.8W. The ripple voltage on the regulated outputs is below 25mV. The SIMO converter is able to sustain the automotive battery crank and dump conditions across the battery variation range of 4.5-27V. A line regulation of 6.3-16.2mV/V and a load regulation of 0.16mV/mA are provided by the SIMO converter. In the presence of wide range of battery variations, the SIMO converter incorporates all the necessary protections circuits and under/over voltage interrupts through I2C communication
Intrasellar tuberculoma presenting as pituitary apoplexy
No full textThe combination of apoplectic symptoms and a sellar mass most often points to a diagnosis of a pituitary adenoma. Sellar tuberculomas are not considered as a cause of 'pituitary apoplexy' and there has been no radiological documentation of haemorrhage associated with them. We report a 27 years old man who presented with 3 previous episodes of pituitary apoplexy. CT scan showed evidence of a sellar mass with haemorrhage. Transsphenoidal biopsy of the intrasellar mass was reported as 'tuberculoma'. The patient had marked reduction in the size of the lesion following antituberculous therapy with no recurrence of symptoms. Intrasellar tuberculomas must be considered as one of the differential diagnosis when patients present with a pituitary apoplexy
High cervical and lumbar canal stenosis of varied etiology: a case report
No full textDevelopmental stenosis without any significant spondylotic changes frequently occurs at C3 vertebra or below, and typically extends to C6-C7. However, high cervical focal canal stenosis is unusual. A case of cervical canal segmental stenosis at C2-3 level in addition to a developmental stenosis of the lumbar region, in a 45 year old male, has been presented in this article. The dynamics of the spinal canal in relation to the likely pathology of such conditions are reviewed. We speculate that focal segmental stenosis in the high cervical region may be due to a possible premature fusion of the neurocentral synchondrosis of the cartilage, or due to an abnormal rotary biomechanics which can result in facetal hypertrophy
High cervical and lumbar canal stenosis of varied etiology: a case report
No full textDevelopmental stenosis without any significant spondylotic changes frequently occurs at C3 vertebra or below, and typically extends to C6-C7. However, high cervical focal canal stenosis is unusual. A case of cervical canal segmental stenosis at C2-3 level in addition to a developmental stenosis of the lumbar region, in a 45 year old male, has been presented in this article. The dynamics of the spinal canal in relation to the likely pathology of such conditions are reviewed. We speculate that focal segmental stenosis in the high cervical region may be due to a possible premature fusion of the neurocentral synchondrosis of the cartilage, or due to an abnormal rotary biomechanics which can result in facetal hypertrophy
Brown tumor in mandible as a first sign of vitamin D deficiency: A rare case report and review
No full textCentral giant cell granulomas (CGCGs) are uncommon but the most aggressive benign intraosseous tumors of jaws, with an unpredictable outcome. They account for less than 7% of all benign jaw lesions, with a female to male ratio of about 2:1. The classical "brown tumor" is commonly seen in the long bones, pelvis, and ribs. Facial bone involvement is rare and usually appears as solitary or multilocular soap bubble like radiolucencies. CGCGs are traditionally treated by both surgical and intralesional injection, with a variable recurrence rate. Here, we report a 12-year-old female patient with mandibular brown tumor as a first sign of secondary hyperthyroidism induced due to vitamin D deficiency and hypocalcemia
Impact of reactor environment on quenching heat transfer of accident tolerant fuel cladding
No full textThis electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Thesis: S.M., Massachusetts Institute of Technology, Department of Nuclear Science and Engineering, 2018Cataloged from student-submitted PDF version of thesis. Page 123 blank.Includes bibliographical references (pages 106-116).Development of accident tolerant fuels (ATF) for light water reactors (LWRs) came into focus for the nuclear engineering community after the accidents at Fukushima-Daiichi. The primary focus of the ATF program is to identify alternative fuel and cladding technologies that may provide enhanced safety, competitiveness, and economics. The new fuel design must also be compatible with present-day LWR design. For near-term applications, coatings on the nominal Zirconium-based cladding material and other metallic materials are being considered to improve the corrosion resistance and reduce the generation of hydrogen at high temperatures. Major ATF coating choices under consideration include chromium as a coating, iron-chromium-aluminum alloys (FeCrAl) as cladding and molybdenum as a coating, which have demonstrated better mechanical and oxidation behavior during the experimental testing.Thermal-fluids characteristics are pivotal for a robust testing of ATF concepts as the proposed candidates may have an entirely different thermal-hydraulic behavior when compared to Zircaloy-4. ATF coatings may display very different boiling characteristics as a result of different microstructures and surface characteristics. In the present work, transient boiling heat transfer during quenching of the candidate ATF claddings on vertical rodlets is studied experimentally. The candidate ATF material (chromium, FeCrAl, and molybdenum) are applied on Zircaloy-4 rodlets. The vertical solid rodlets are heated to temperatures up to 1000 °C and are quenched in a saturated pool of water at atmospheric pressure. The temperature variation during the quenching of rodlets was recorded insitu with synchronized visualization of boiling regimes over the test specimen using a high-speed video camera.The quench performance of the ATF coatings was analyzed based on the examination of various surface parameters such as wettability, roughness, emissivity and capillary wicking. In order to obtain a more realistic picture of the candidate performance during the emergency cooling reflood phase in a nuclear reactor, the coated rodlets are also oxidized in an autoclave before quenching. The performance of the candidate claddings is evaluated after oxidation and the surface characterized. It was observed from the post-test analysis that the surface characteristics and oxidation had a significant impact on the quench performance of ATF coatings, which varied between different coating materials. In order to better understand the thermal margins in a reactor specific environment, an analysis was performed on samples after exposing them to gamma rays. The gamma rays tend to change the surface wettability through a phenomenon called Radiation Induced Surface Activation.A Gammacell 220E irradiator that uses 12 cobalt-60 pencil sources, arranged axially in a sample chamber at MIT, was used to irradiated the samples. The results of water quenching and contact angle studies showed a higher Leidenfrost temperature and wettability in both samples exposed to gamma irradiation. The detailed microscopic analysis attributed the enhanced wettability to oxidation of the surface under gamma irradiation.by Arunkumar Seshadri.S.M.S.M. Massachusetts Institute of Technology, Department of Nuclear Science and Engineerin
Stability of n-Dimensional Additive Functional Equation in Generalized 2-Normed Space
No full textIn this paper, the author established the general solution and generalized Ulam-Hyers-Rassias stability of n-dimensional additive functional equatio
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