Supercapacitor-based linear converter for voltage regulator modules
type: CreativeWork
description: This 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 issu…
abstract: This 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 issu…
author: Wickramasinghe, Thilini Chintha Prabha Kumari
keywords: DC-DC converter, Efficiency, Supercapacitors
license: https://researchcommons.waikato.ac.nz/bitstreams/518c78f3-1834-4399-afe3-4b65978b1003/download
date published: 2016
date modified: 2026-07-24T05:57:36Z
provider: University Waikato
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Waikato