2 research outputs found
Design of Power Management Integrated Circuits and High-Performance ADCs
A battery-powered system has widely expanded its applications to implantable medical devices
(IMDs) and portable electronic devices. Since portable devices or IMDs operate in the
energy-constrained environment, their low-power operations in combination with efficiently sourcing
energy to them are key problems to extend device life. This research proposes novel circuit
techniques for two essential functions of a power receiving unit (PRU) in the energy-constrained
environment, which are power management and signal processing.
The first part of this dissertation discusses power management integrated circuits for a PRU.
From a power management perspective, the most critical two circuit blocks are a front-end rectifier
and a battery charger. The front-end CMOS active rectifier converts transmitted AC power into
DC power. High power conversion efficiency (PCE) is required to reduce power loss during the
power transfer, and high voltage conversion ratio (VCR) is required for the rectifier to enable low-voltage
operations. The proposed 13.56-MHz CMOS active rectifier presents low-power circuit
techniques for comparators and controllers to reduce increasing power loss of an active diode with
offset/delay calibration. It is implemented with 5-V devices of a 0.35 µm CMOS process to support
high voltage. A peak PCE of 89.0%, a peak VCR of 90.1%, and a maximum output power of 126.7
mW are measured for 200Ω loading.
The linear battery charger stores the converted DC power into a battery. Since even small
power saving can be enough to run the low-power PRU, a battery charger with low IvQ is desirable.
The presented battery charger is based on a single amplifier for regulation and the charging
phase transition from the constant-current (CC) phase to the constant-voltage (CV) phase. The
proposed unified amplifier is based on stacked differential pairs which share the bias current. Its
current-steering property removes multiple amplifiers for regulation and the CC-CV transition, and
achieves high unity-gain loop bandwidth for fast regulation. The charger with the maximum charging
current of 25 mA is implemented in 0.35 µm CMOS. A peak charger efficiency of 94% and
average charger efficiency of 88% are achieved with an 80-mAh Li-ion polymer battery.
The second part of this dissertation focuses on analog-to-digital converters (ADCs). From a
signal processing perspective, an ADC is one of the most important circuit blocks in the PRU.
Hence, an energy-efficient ADC is essential in the energy-constrained environment. A pipelined successive
approximation register (SAR) ADC has good energy efficiency in a design space of
moderate-to-high speeds and resolutions. Process-Voltage-Temperature variations of a dynamic
amplifier in the pipelined-SAR ADC is a key design issue. This research presents two dynamic
amplifier architectures for temperature compensation. One is based on a voltage-to-time converter
(VTC) and a time-to-voltage converter (TVC), and the other is based on a temperature-dependent
common-mode detector. The former amplifier is adopted in a 13-bit 10-50 MS/s subranging
pipelined-SAR ADC fabricated in 0.13-µm CMOS. The ADC can operate under the power supply
voltage of 0.8-1.2 V. Figure-of-Merits (FoMs) of 4-11.3 fJ/conversion-step are achieved. The latter
amplifier is also implemented in 0.13-µm CMOS, consuming 0.11 mW at 50 MS/s. Its measured
gain variation is 2.1% across the temperature range of -20°C to 85 °C
Proposal of Wireless Charging Method and Architecture to Increase Range in Electric Vehicles
Indiana University-Purdue University Indianapolis (IUPUI)Electric vehicles (EVs) face a major issue before becoming the norm of society, that is, their lack of range when it comes to long trips. Fast charging stations are a good step forward to help make it simpler for EVs, but it is still not as convenient when compared to vehicles with an internal combustion engine (ICE). Plenty of infrastructure changes have been proposed in the literature attempting to tackle this issue, but they typically tend to be either an expensive solution or a difficult practical implementation.
This dissertation presents two solutions to help increase the range of EVs: a novel wireless charging method and a multi-motor architecture for EVs. The first proposed solution involves the ability for EVs to charge while en route from another vehicle, which will be referred to from here on as vehicle-to-vehicle recharging (VVR). The aim of this system is to bring an innovative way for EVs to charge their battery without getting off route on a highway. The electric vehicle can request such a service from a designated charger vehicle on demand and receive electric power wirelessly while en route. The vehicles that provide energy (charger vehicles) through wireless power transfer (WPT) only need to be semi-autonomous in order to ``engage'' or ``disengage'' during a trip. Also, a novel method for wireless power transfer will be presented, where the emitter (TX) or receiver (RX) pads can change angles to improve the efficiency of power transmission. This type of WPT system would be suitable for the VVR system presented in this dissertation, along with other applications.
The second solution presented here will be an architecture for EVs with three or more different electric motors to help prolong the state of charge (SOC) of the battery. The key here is to use motors with different high efficiency regions. The proposed control algorithm optimizes the use of the motors on-board to keep them running in their most efficient regions. With this architecture, the powertrain would see a combined efficiency map that incorporates the best operating points of the motors. Therefore, the proposed architecture will allow the EV to operate with a higher range for a given battery capacity.
The state-of-the-art is divided into four subsections relevant to the proposed solutions and where most of the innovations to reduce the burden of charging EVs can be found: (1) infrastructure changes, (2) device level innovations, (3) autonomous vehicles, and (4) electric vehicle architectures. The infrastructure changes highlight some of the proposed systems that aim to help EVs become a convenient solution to the public. Device level innovations covers some of the literature on technology that addresses EVs in terms of WPT. The autonomous vehicle subsection covers the importance of such technology in terms of safety and reliability, that could be implemented on the VVR system. Finally, the EV architectures covers the current typologies used in EVs. Furthermore, modeling, analysis, and simulation is presented to validate the feasibility of the proposed VVR system, the WPT system, and the multi-motor architecture for EVs