Design of an ultra-low power DC-DC boost converter

• Main Author: Leung, Kah Wei
• Other Authors: Siek Liter
• Format: Final Year Project
• Language: English
• Published: 2014
• Subjects: DRNTU::Engineering
• Online Access: http://hdl.handle.net/10356/61304
• Institution: Nanyang Technological University

Ambient energy harvesting, also called as energy scavenging or power harvesting, is the process where usable energy is acquired from everyday environment. Ambient energy sources are now categorized as energy reservoirs as it allows portable or wireless systems to have self-sustaining capabilities and if possible, completely battery independent. However the voltage produced by ambient energy such as solar and thermal, are too low to charge up any energy storage devices. Therefore a Ultra-Low Power DC-DC boost converter is required to boost the voltage from energy harvester to power up applications or to charge energy storage devices. This report presents the design of several building blocks required for an ultra-low power DC-DC boost converter to have ultra-low power capability. A Maximum Power Point Transfer circuit that adopts the Perturb and Observe method was designed to improve the power efficiency transferred from the harvested energy to the DC-DC boost converter. The Maximum Power Point Tracking Circuit consists of a Switching Multiplier, Power Comparator and a variable pulse generator. Therefore the DC-DC boost converter will operate in Discontinuous conduction mode and employing Pulse frequency modulation and pulse width modulation to achieve sub-optimum Maximum Power Transfer. Current starved voltage controlled oscillator with Frequency divider was included in the design to further reduce power consumption of the DC-DC boost converter. The circuits were designed and simulated in Global Foundries 0.18um CMOS technology. The simulation results have shown that the Maximum Power Point Transfer circuit and the Current starved voltage controlled oscillator are able to minimize power consumption at clock frequency ranging from 2.5 KHz to 10 KHz and 1.8V supply voltage. The objective was met as the implemented circuit design could detect output power changes from the PV panel and adjust the duty ratio of the DC-DC boost converter accordingly to maximize power transfer from the PV panel to the DC-DC boost converter.