2 research outputs found
Efficient power management circuits for energy harvesting applications
Low power IoT devices are growing in numbers and by 2020 there will be more than 25 Billion of those in areas such as wearables, smart homes, remote surveillance, transportation and industrial systems, including many others. Many IoT electronics either will operate from stand-alone energy supply (e.g., battery) or be self-powered by harvesting from
ambient energy sources or have both options. Harvesting sustainable energy from ambient environment plays significant role in extending the operation lifetime of these devices and hence, lower the maintenance cost of the system, which in turn help make them integral to simpler systems. Both for battery-powered and harvesting capable systems, efficient power delivery unit remains an essential component for maximizing energy efficiency. The goal of this research is to investigate the challenges of energy delivery for low power electronics considering both energy harvesting as well as battery-powered conditions and to address those challenges. Different challenges of energy harvesting from low voltage energy sources based on the limitations of the sources, the type of the regulator used and the pattern of the load demands have been investigated. Different aspects of the each
challenges are further investigated to seek optimized solutions for both load specific and generalized applications. A voltage boost mechanism is chosen as the primary mechanism to investigate and to addressing those challenges, befitting the need for low power applications which often rely on battery voltage or on low voltage energy harvesting sources. Additionally, a multiple output buck regulator is also discussed. The challenges analyzed include very low voltage start up issues for an inductive boost regulator, cascading of boost regulator stages, and reduction of the number of external component through reusing those. Design techniques for very high conversion ratio, bias current reduction with autonomous
bias gating, battery-less cold start, component and power stage multiplexing for reconfigurable and multi-domain regulators are presented. Measurement results from several silicon prototypes are also presented.Ph.D
Low voltage autonomous buck-boost regulator for wide input energy harvesting
While high power buck-boost regulators have been extensively researched and
developed in the academia and industry, low power counterparts have only recently gained
momentum due to the advent of different battery powered and remote electronics. The
application life-time of such applications, e.g., remote surveillance electronics can be
extended tremendously by enabling energy autonomy. While battery powered electronics
last long but they must be replenished once the battery is depleted either by replacing the
battery or by retrieving the electronics and then recharging. Instead, energy harvesting from
available ambient sources on the spot will enable these electronics continuous operation
unboundedly, probably even beyond the lifetime of the electronics. Interestingly enough,
recent advancements in micro-scale energy transducers compliment these demand [1-13].
Micro-transducers producing energy from different ambient sources have been reported.
These transducers produce enough energy to support a wide range of operations of the
remote electronics concurrently. These transducers along with an additional storage
elements greatly increase the energy autonomy as well as guaranteed operation since
harvested energy can then be stored for future use when harvestable energy is temporarily
unavailable.
Recently several buck-boost regulators with low power and low input operating
voltage have been reported both from academia and industry [14-24]. Some of this work
focuses on increasing efficiency in the mid-load range (10mA-100mA), while some other
focuses on lowering input range. However, so far no one has reported a buck-boost
regulator operating with sub-200nW bias power while harvesting energy from sub-500mV input range. This work focuses on the development of a low voltage low bias current buckboost regulator to attain these goals.
In this work, complete design of a PFM mode buck-boost regulator has been
discussed in details. Basic topology of the regulator and working principle of the
implemented architecture along with the advantages of the specific topology over that of
the others have been discussed in short to provide an uninterrupted flow of idea. Later,
Transistor level design of the basic building blocks of the buck-boost regulator is discussed
in details with different design features and how those are attained through transistor level
implementation are discussed. Subsequently, the physical layout design technique and
considerations are discussed to inform the reader about the importance of the layout process
and to avoid pitfalls of design failure due to layout quality issues.
Measurement results are presented with the fabricated IC. Different
characterization profile of the IC have been discussed with measured data and capture
oscilloscope waveforms. Load regulation, line regulation, efficiency, start-up from low
voltage, regulation with line and load transient events are measured, presented and
discussed. Different characteristics of the prototype are compared with prior arts and are
presented in a comparison table. Die micrograph is also presented along with the different
issue of the IC testingM.S