Versatile Optochemical Quantification with Optical Mouse

There is an ever increasing need for simple, low-cost instruments for ubiquitous medical and environmental measurements in conjunction with networks and Internet-of-things. This work demonstrates that the optical mouse, one of the most common optoelectronic computer peripherals, can be used for chemical quantification. Particularly, we explore the feasibility of using the preassembled optical platform of mouse for oxygen and pH quantification. The image sensor and the light-emitting diode (LED) serve as photodetector and excitation/illumination light source, respectively, while the preinstalled microoptics (e.g., lens and waveguide) provide a fixed optical arrangement convenient for sample analysis. This novel, cost-effective approach demonstrates the potential application of optical mouse for bioanalytical devices in conjunction with commercial sensor strips or simple microfluidic elements. This is one viable option for seamless integration of bioanalytical capability into existing personal computers and associate networks without significant additional hardware

Analysis and Optimization of the Two-Phase Series Capacitor Buck DC-DC Converter

Current sharing schemes for conventional multi-phase converters are based on sensing each phase current to deliver the current information to their controllers. In conventional buck converters, this fact may require a preset current sharing ratio at the expense of efficiency, which eventually requires a larger sensing circuit to achieve the sensing accuracy of each phase. Introducing the concept of automatic current sharing is one of the solutions to tackle this issue. Automatic current sharing (Current Sharing Mechanism CSM) is an advanced way to distribute heat generation in multi-phase switching topologies at full load. A two-phase series capacitor buck converter (2-pscB) was introduced to power laptops as low-voltage and high-current Voltage Regulator Modules (VRMs) as well as non-isolated Point-of-Load (PoL) converters. The current sharing concept is the main feature of this 2-pscB topology, where series capacitor voltage is used to achieve current sharing without the need for a phase current sensing circuit or complicated control loop. In this work, a complete state-space average model for the series capacitance buck switching regulators is linearized to develop a robust controller satisfying the stability and converter performance specifications. The presented averaging model includes the simplest model of the regulator’s parameters and only the main parasitic components. Both, an improved derivation of the main design parameters and a novel design methodology of MOSFETs isolated gate driver circuit are proposed and verified. Different high voltage input 2-pscB power density dc-dc converters are successfully investigated to examine the capability of current sharing at a higher voltage level and its impact on efficiency. Another novel approach of eGaN gate driver circuitry is designed with a Current-Mode Controller CMC using one current path to minimize propagation delays and reduce phases parasitic components, which helps enhance overall performance. 110V/12V/6A experimental prototype converter of Si MOSFETs was designed, its current sharing characteristics were experimentally tested and verified. Since eGaN technologies have attracted great attention in power electronics applications due to their capabilities and efficient energy conversion, another design, and analysis of a sensor-less eGaN-based 48V/5V 2-pscB buck switching converters were verified, and their current sharing characteristics were predicted by the state-space modeling technique. A theoretical comparison is conducted between conventional buck converter and 2-pscB. The results show the following characteristics of 2-pscB topology: a small inductor current ripple, low switching loss, inherited current sharing mechanism, duty cycle flexibility, and filter component size reduction. In a word, new modeling methods of various 2-pscB control schemes are proposed and broadly studied. This dissertation simulates most of these methods to provide the designers with a better comprehensive view of the 2-pscB converter topology

A High-Input Voltage Two-Phase Series-Capacitor DC-DC Buck Converter

A high-input voltage 2-phase series-capacitor (2-pscB) DC-DC buck converter is theoretically analyzed, designed, and implemented. A new design approach for an automatic current sharing scheme was presented for a 2-phase series-capacitor synchronous buck converter. The series-capacitor voltage is used to achieve current sharing between phases without a current sensing circuit or external control loop as each phase inductor charges and discharges the series capacitor to maintain its average capacitor voltage constant. A novel isolated gate driver circuit to accommodate an energy storage capacitor is proposed to deliver isolated gate voltages to the switching transistors. An I2 control scheme that uses only one feedback path control for the four gate drivers is proposed to enable higher voltage conversion. An experimental 110-12 V 6 A load prototype converter was designed, and its current sharing characteristics were experimentally verified

Optical Mouse as pH Analyzer

Optical sensor for chemical analysis is a growing technology since it offers many advantages. The goal of this research is to achieve pH sensing using low-cost optoelectronics devices such as optical mouse, which consist of photodetector, light source and pre-installed optics. Colorimetric pH measurements were done with the optical mouse utilizing commercial pH test strips. All images were taken with an built-in image sensor of optical mice and several factors for image acquisition such as optical filter, light source and gray scale image analysis were evaluated. pH evaluation with spectrophotometer was also conducted and compared with data obtained with mice in a pH range between 2-12 providing reliable results

Versatile Optochemical Quantification with Optical Mouse

There is an ever increasing need for simple, low-cost instruments for ubiquitous medical and environmental measurements in conjunction with networks and Internet-of-things. This work demonstrates that the optical mouse, one of the most common optoelectronic computer peripherals, can be used for chemical quantification. Particularly, we explore the feasibility of using the preassembled optical platform of mouse for oxygen and pH quantification. The image sensor and the light-emitting diode (LED) serve as photodetector and excitation/illumination light source, respectively, while the preinstalled microoptics (e.g., lens and waveguide) provide a fixed optical arrangement convenient for sample analysis. This novel, cost-effective approach demonstrates the potential application of optical mouse for bioanalytical devices in conjunction with commercial sensor strips or simple microfluidic elements. This is one viable option for seamless integration of bioanalytical capability into existing personal computers and associate networks without significant additional hardware

Electrical and thermal characterization of (250 °C) SiC power module integrated with LTCC-based isolated gate driver

The high-voltage SiC MOSFET power modules enable high-frequency and high-efficiency power conversion. The parasitic inductances induced by traditional packages of this device technology significantly deteriorate device switching performance, especially in high-temperature applications. In this paper, a novel low-cost discrete SMD component gate driver embedded in a SiC MOSFET power module is introduced. A newly integrated packaging structure has been introduced and proved to be efficient in reducing package-related turn-on loss and turn-off parasitic ringing. However, the gate propagation delay and optocoupler on-chip weak output signal in such a structure become limitations for further pushing the operating frequency and the output current level for high-efficiency power conversion. The electrical characterization of low-temperature co-fired ceramic (LTCC) gate drivers is covered. Furthermore, a 1200 V/120A SiC MOSFET phase-leg power module utilizing high-temperature packaging technologies has been developed. The static characteristics, switching performance, and thermal behavior of the fabricated power module are fully evaluated under operating temperature variations of up to 250 °C