111 research outputs found
Supercapacitor assisted low dropout regulators (SCALDO) with reduced switches: A new approach to high efficiency VRM designs
No full textSupercapacitor assisted low dropout (SCALDO) regulator is a new approach to develop high efficiency DC-DC converters with supercapacitors used for energy recovery. One limitation in these topologies is that in some configurations a large number of low-speed switches are required. If the SCALDO technique is adapted to build voltage regulator modules (VRM), it is necessary to reduce number of switches combined with a high current capable LDO. A new topology-variation with less number of switches can be achieved by reconfiguring the original SCALDO and adding an extra LDO to the circuit. The paper presents a summary of some preliminary work, and experimental results for a 2.5V proof of concept-prototype
Supercapacitor-based linear converter for voltage regulator modules
No full textThis thesis investigates a linear converter technique suitable for microprocessor voltage regulator modules (VRMs). The original linear regulator is the patented supercapacitor assisted low-dropout regulator (SCALDO). A less complex, lower cost design was achieved by reducing the number of switches in the original SCALDO and adding a second low dropout regulator (LDO).
In the initial implementation of this reduced-switch SCALDO (RS-SCALDO), output regulation failed due to the presence of a parasitic body-diode in standard LDOs. The body-diode forms an unwanted discharge path to ground for the supercapacitor. In order to block this path, an application specific LDO that operates in the third quadrant of a MOSFET current-vs-voltage transfer function was investigated.
A 3.5-to-1.5 V RS-SCALDO was designed with a supercapacitor, two LDOs and two switches. Compared with the standard SCALDO approach, this new design halves the number of switches required. Discrete MOSFET-based high-current LDOs were developed and combined with a common feedback control circuit. Voltage identification (VID) capability was implemented using a digital potentiometer. Theoretically, when an LDO converts 3.5 V to 1.5 V a maximum efficiency of 1.5/3.5(~43%) can be achieved. According to the general theory of SCALDO, a single supercapacitor configuration can achieve nearly twice the linear regulator efficiency. The 3.5-to-1.5 V, 5 A RS-SCALDO achieved an approximate end-to-end efficiency of 80%, thus, agreeing with SCALDO general theory.
Large-signal analysis was used to model MOSFET non-linearities and predict the performance of LDOs, switches and the overall system. Matlab modeling predictions for body-diode behaviour were cross-checked via SPICE simulation; the results agreed with bench measurements.
RS-SCALDO regulators cycle at very low frequencies, usually in the range of millihertz to hertz. Therefore, electromagnetic interference emitted by high-frequency switched-mode VRMs is not an issue here. Compared to typical high-frequency VRMs, RS-SCALDO topology provides similar efficiencies with the high slew-rate and low noise output of a linear regulator. In generalized SCALDO configuration with n supercapacitors, a total of 3n+1 switches required; in contrast RS-SCALDO reduces the switch count to 2n. With the elimination of the body-diode parasitics, the technique can be extended to much higher currents
A review on single-phase, single-stage OBC topologies for EVs with 48 V powertrains
No full textInternational audienceElectric vehicles use for urban mobility are rising with the new generation of 48 V powertrain technology. However, the challenge is to select onboard charger (OBC) topologies with less complex, economically feasible, and highly efficient battery chargers for these electric vehicles (EVs). At present, traditional multi-stage converters are being used by compromising efficiency, volume, weight, and cost. Single-stage OBC topologies can be designed by combining a few functions of a muli-stage coverter with a reduced number of components. They are aiming to eliminate issues related to multi-stage converters. However, the stress on power devices of single-stage OBCs can lead to other issues such as the requirement of expensive high power devices, thermal control, etc. This paper reviews single-phase, single-stage OBC topologies feasible for EVs with 48 V powertrain technology. Especially the isolated bidirectional AC–DC converters are considered as to include the vehicle-to-grid (V2G) capability
Scenography of Heritage: An Urban think Tank
No full textAs a result of long time colonisation and trade, the city of Semarang in Indonesia has a large stock of built heritage that share a history with the Netherlands. The Dutch colonial buildings, left to decay have become a backdrop for tourists and feed into the 'insta culture' sweeping the current decade. At the same time the city suffers deeply from a neglected river, Kali Semarang, and lack of accessibility to water. How can we confront the current issues of water, waste and neglected built heritage? The idea that we are all connected, spatially, politically, environmentally and by memory and so on are confronted while finding solutions to empower the communities, and provide better access to a basic human right; water.Architecture, Urbanism and Building Sciences | Heritage & Architectur
Reduced‐switch SCALDO: an extra low‐frequency DC–DC converter technique for VRM applications
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Driving Progress in Science Education, Research, Policy, and Diplomacy: Exploring the Impact of the Sri Lankan Academy of Young Scientists
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A study on the challenges in GaN HEMT-based designs from component to board development level
No full textInternational audienceThis paper presents a study on a few main challenges in GaN-based designs from component to board development level. Transistors in parallel in a switch are more critical in designing power cells due to the high sensitivity to parasitic components in both power and gate control circuits. Further, the changes in switching behaviour on the discrepancies in device parameters are yet to be realized. In this study, both experimental and simulation based approaches are used for the verification of parasitic effects. The large signal modeling with LTSpice simulation is used for the prediction of effect due to parametric variation of devices in parallel
RaPCO asthma database
No full textThe data set of the Rajarata Pregnancy Cohort pertaining to the asthmatic pregnant women without comorbid cardiac conditions
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