Adaptive prediction in digitally controlled buck converter with fast load transient response

An adaptive prediction scheme based on linear extrapolation for digitally controlled voltage-mode buck-type switching converter is presented. A major drawback of conventional digitally controlled switching converters is bandwidth limitation due to the additional phase lag in the digital feedback control loop. By predicting the future error voltage, the ADC sampling time delay is compensated in order to achieve a higher bandwidth even with a modest sampling rate. Both simulation and measurement results show that the output voltage settling time of the digitally controlled buck converter is reduced by as much as 28% with the proposed adaptive prediction. The fastest settling time in response to a 600mA load transient is around 15μs, approaching the transient response of the state-of-the-art analog-based controller.published_or_final_versio

Scalability of Quasi-hysteretic FSM-based Digitally Controlled Single-inductor Dual-string Buck LED Driver To Multiple Strings

There has been growing interest in Single-Inductor Multiple-Output (SIMO) DC-DC converters due to its reduced cost and smaller form factor in comparison with using multiple single-output converters. An application for such a SIMO-based switching converter is to drive multiple LED strings in a multi-channel LED display. This paper proposes a quasi-hysteretic FSM-based digitally controlled Single-Inductor Dual-Output (SIDO) buck switching LED Driver operating in Discontinuous Conduction Mode (DCM) and extends it to drive multiple outputs. Based on the time-multiplexing control scheme in DCM, a theoretical upper limit of the total number of outputs in a SIMO buck switching LED driver for various backlight LED current values can be derived analytically. The advantages of the proposed SIMO LED driver include reducing the controller design complexity by eliminating loop compensation, driving more LED strings without limited by the maximum LED current rating, performing digital dimming with no additional switches required, and optimization of local bus voltage to compensate for variability of LED forward voltage (VF) in each individual LED string with smaller power loss. Loosely-binned LEDs with larger VF variation can therefore be used for reduced LED costs.postprin

Adaptive High-Bandwidth Digitally Controlled Buck Converter with Improved Line and Load Transient Response

Digitally controlled switching converter suffers from bandwidth limitation because of the additional phase delay in the digital feedback control loop. In order to overcome the bandwidth limitation without using a high sampling rate, this paper presents an adaptive third-order digital controller for regulating a voltage-mode buck converter with a modest 2x oversampling ratio. The phase lag due to the ADC conversion time delay is virtually compensated by providing an early estimation of the error voltage for the next sampling time instant, enabling a higher unity-gain bandwidth without compromising stability. An additional pair of low-frequency pole and zero in the third-order controller increases the low-frequency gain, resulting in faster settling time and smaller output voltage deviation during line transient. Both simulation and experimental results demonstrate that the proposed adaptive third-order controller reduces the settling time by 50% in response to a 1 V line transient and 30% in response to a 600 mA load transient, compared to the baseline static second-order controller. The fastest settling time is measured to be around 11.70 s, surpassing the transient performance of conventional digital controllers and approaching that of the state-of-the-art analog-based controllers.postprin

Annealing effects on the loss and birefringence of silicon oxynitride rectangular optical waveguides

Author name used in this publication: M. S. DemokanVersion of RecordPublishe

Integrated liquid crystal optical switch based on total internal reflection

Demokan, M. S.Version of RecordPublishe

Reset-sensing quasi-V2 single-inductor multiple-output buck converter with reduced cross-regulation

This paper proposes a reset-sensing quasi-V2 single-inductor multiple-output (SIMO) converter with minimal cross-regulation. The conventional quasi-V2 sensing scheme in SIMO converters suffers from serious cross-regulation which is primarily induced by the load differentiation with unbalanced loads. It is shown that the proposed reset-sensing quasi-V2 control scheme can significantly reduce cross-regulation by completely discharging the feed-forward sensing node to zero volts during the idle phase in Discontinuous Conduction Mode (DCM). The cross-regulation with the conventional quasi-V2 single-inductor dual-output (SIDO) converter for a load current step of 150 mA is experimentally verified to be more than 1.25 mV/mA. By employing the proposed quasi-V2 control method, the experimental results demonstrate that the cross-regulation for a load current step of 150 mA is significantly reduced to within 0.087 mV/mA. Hence, with the proposed scheme, a load transient in one output will have a minimal effect on the DC operating point of another output. This enables separate current control at each individually-driven output of a SIMO converter. © IEEE.published_or_final_versio

Rationale and design of the screening of pulmonary hypertension in systemic lupus erythematosus (SOPHIE) study

published_or_final_versio

An empirical model to determine the grain size of metal-induced lateral crystallized film

Thin-film transistors (TFTs) have been fabricated using the nickel-seeded metal-induced lateral crystallization (MILC), in which an amorphous silicon is crystallized to form a large grain polysilicon film. Single crystal SOI, solid phase crystallization (SPC), and MILC TFTs were fabricated and the carrier mobilities extracted. Different types of devices have different variations in electrical properties. An empirical model based on the presence of the grain boundaries is proposed to explain the experimental results. The experimental data was used to extract the model parameters and the number of grains and grain size present in the device channel. The results can be further used to optimize the crystallization process and the device design

Electron-beam double resist process to enhance bright field pattern resolution

Electron-beam direct write is a promising technique for deep submicron lithography. One of the common methods to define a bright field pattern for the gate electrode masking uses negative resist. However, the resolution of many popular negative resists is low compared to that of positive resists. A technique is demonstrated that takes advantage of positive resist, such as polymethylmethacrylate and converts it to a bright field masking step. The technique involves (1) using a negative resist coating on a positive resist pattern, (2) plasma etching the negative resist down to the top of the positive resist, (3) exposing large area with electrons or deep ultraviolet photons, and (4) developing the result with a ratio of methyl isobutyl ketone and isopropanol. The resulting bright field masking provides high-resolution dense line patterns, which are difficult to achieve using the common negative resists alone. (C) 2002 American Vacuum Society

Fabrication of gate-all-around transistors using metal induced lateral crystallization

Gate-all-around transistor (GAT) is demonstrated. The device can be fabricated on either a bulk silicon wafer or on the top of any device layers. The fabrication process used a new technique called metal-induced-lateral-crystallization (MILC) to recrystallize the amorphous silicon to form large silicon grain in the active area. Using this technique, the transistor performance is comparable to a SOI MOSFET. Compared with the single-gate thin film transistor (SGT) and solid phase crystallization (SPC) device, MILC GAT has lower subthreshold slope, lon er threshold voltage, higher transconductance and nearly double drive current. The impact of short channel length was investigated