Hard macrocells for DC/DC converter in automotive embedded mechatronic systems

A novel configurable DC/DC converter architecture, to be integrated as hard macrocell in automotive embedded systems, is proposed in the paper. It aims at realizing an intelligent voltage regulator. With respect to the state of the art, the challenge is the integration into an automotive-qualified chip of several advanced features like dithering of switching frequency, nested control loops with both current and voltage feedback, asynchronous hysteretic control for low power mode, slope control of the power FET gate driver, and diagnostic block against out-of-range current or voltage or temperature conditions. Moreover, the converter macrocell can be connected to the in-vehicle digital network, exchanging with the main vehicle control unit status/diagnostic flags and commands. The proposed design can be configured to work both in step-up and step-down modes, to face a very wide operating input voltage range from 2.5 to 60 V and absolute range from −0.3 to 70 V. The main target is regulating all voltages required in the emerging hybrid/electric vehicles where, besides the conventional 12 V DC bus, also a 48 V DC bus is present. The proposed design supports also digital configurability of the output regulated voltage, through a programmable divider, and of the coefficients of the proportional-integrative controller inside the nested control loops. Fabricated in 0.35 μm CMOS technology, experimental measurements prove that the IC can operate in harsh automotive environments since it meets stringent requirements in terms of electrostatic discharge (ESD) protection, operating temperature range, out-of-range current, or voltage condition

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

Design and fabrication of a long-life Stirling cycle cooler for space application. Phase 3: Prototype model

A second-generation, Stirling-cycle cryocooler (cryogenic refrigerator) for space applications, with a cooling capacity of 5 watts at 65 K, was recently completed. The refrigerator, called the Prototype Model, was designed with a goal of 5 year life with no degradation in cooling performance. The free displacer and free piston of the refrigerator are driven directly by moving-magnet linear motors with the moving elements supported by active magnetic bearings. The use of clearance seals and the absence of outgassing material in the working volume of the refrigerator enable long-life operation with no deterioration in performance. Fiber-optic sensors detect the radial position of the shafts and provide a control signal for the magnetic bearings. The frequency, phase, stroke, and offset of the compressor and expander are controlled by signals from precision linear position sensors (LVDTs). The vibration generated by the compressor and expander is cancelled by an active counter balance which also uses a moving-magnet linear motor and magnetic bearings. The driving signal for the counter balance is derived from the compressor and expander position sensors which have wide bandwidth for suppression of harmonic vibrations. The efficiency of the three active members, which operate in a resonant mode, is enhanced by a magnetic spring in the expander and by gas springs in the compressor and counterbalance. The cooling was achieved with a total motor input power of 139 watts. The magnetic-bearing stiffness was significantly increased from the first-generation cooler to accommodate shuttle launch vibrations

Space station common module network topology and hardware development

Conceptual space station common module power management and distribution (SSM/PMAD) network layouts and detailed network evaluations were developed. Individual pieces of hardware to be developed for the SSM/PMAD test bed were identified. A technology assessment was developed to identify pieces of equipment requiring development effort. Equipment lists were developed from the previously selected network schematics. Additionally, functional requirements for the network equipment as well as other requirements which affected the suitability of specific items for use on the Space Station Program were identified. Assembly requirements were derived based on the SSM/PMAD developed requirements and on the selected SSM/PMAD network concepts. Basic requirements and simplified design block diagrams are included. DC remote power controllers were successfully integrated into the DC Marshall Space Flight Center breadboard. Two DC remote power controller (RPC) boards experienced mechanical failure of UES 706 stud-mounted diodes during mechanical installation of the boards into the system. These broken diodes caused input to output shorting of the RPC's. The UES 706 diodes were replaced on these RPC's which eliminated the problem. The DC RPC's as existing in the present breadboard configuration do not provide ground fault protection because the RPC was designed to only switch the hot side current. If ground fault protection were to be implemented, it would be necessary to design the system so the RPC switched both the hot and the return sides of power

H.E.A.T. - Home Energy Automation Technology

The purpose of this project is to explore residential household climate control systems and develop a viable product concept that integrates any and all heating, ventilation, and air conditioning (HVAC) sources into an automated electronic control system. This project will incorporate a microcontroller-based modular system that provides multiple communication mediums to adapt to most household configurations. This system will utilize a web-based control server that implements efficient climate control algorithms, resulting in improved heating and cooling efficiency for residential and small-business consumers

A series-connected VSC for voltage regulation, balancing and harmonics mitigation

Word processed copy.Includes bibliographical references.Voltage sensitive electronic equipment, such as computers, process controllers, programmable logic controllers, adjustable speed drives and robotic devices is increasingly used in modern industrial processes. Industrial loads thus require a supply free of voltage disturbances such as voltage dips, swells, unbalances and harmonics. The effect of these disturbances may be as bad as a complete shut down of a production line, hence giving rise to the growing interest and need, for mitigation of such power quality problems. The objective of this thesis is to design and build a mitigation device to shield loads from these problems

Investigation of a GaN-Based Power Supply Topology Utilizing Solid State Transformer for Low Power Applications

Gallium nitride (GaN) power devices exhibit a much lower gate capacitance for a similar on-resistance than its silicon counterparts, making it highly desirable for high-frequency operation in switching converters, which leads to their significant benefits on power density, cost, and system volume. High-density switching converters are being realized with GaN power devices due to their high switching speeds that reduce the size of energy-storage circuit components. The purpose of this dissertation research is to investigate a new isolated GaN AC/DC switching converter based on solid-state transformer configuration with a totem-pole power factor corrector (PFC) front-end, a half-bridge series-resonant converter (SRC) for power conversion, and a current-doubler rectifier (CDR) at its output. A new equivalent circuit model for the converter is constructed consisting of a loss-free resistor model for the PFC rectifier with first harmonic approximation model for the SRC and the CDR. Then, state-space analysis is performed to derive the converter transfer function in order to design the controllers to yield sufficient phase margins. The converter offers the advantages of voltage regulation feature of the solid-state transformer, low harmonics and close-to-unity power factor of the PFC rectifier, soft-switching of the half-bridge SRC, reduced size of the high-frequency transformer, and smaller leakage inductance of the CDR which is used for low-voltage high-current applications as the CDR draws half of the load current in the transformer secondary side yielding less copper losses. A high-frequency nanocrystalline toroid transformer, based on a modified equation to determine its leakage inductance, is designed and fabricated to satisfy the performance specifications of the converter. A meticulously planned gate driving strategy together with a Kelvin-source return circuitry is used to mitigate Miller effects, minimize gate ringing, and minimize the parasitics of the pull-down and pull-up loops of the converter. A new programming method that combines MATLAB Simulink embedded coder with code composer studio for the TMS320F28335 digital signal processor (DSP) controller is developed and demonstrated. Finally, the GaN-based AC/DC converter is experimentally verified for a 120Vac to 48Vdc/60Vdc conversion operating at 100 kHz for various loadings

The ac power system testbed

The object of this program was to design, build, test, and deliver a high frequency (20 kHz) Power System Testbed which would electrically approximate a single, separable power channel of an IOC Space Station. That program is described, including the technical background, and the results are discussed showing that the major assumptions about the characteristics of this class of hardware (size, mass, efficiency, control, etc.) were substantially correct. This testbed equipment was completed and delivered and is being operated as part of the Space Station Power System Test Facility

A dimmable light-emitting diode (LED) driver with mag-amp postregulators for multistring applications

Current imbalance should be avoided when multiple LED strings are connected in parallel. In this paper, a dimmable LED driver with magnetic-amplifier postregulators for multistring applications is presented. Powered by a common master source, parallel LED strings are individually regulated by their corresponding adaptive slave sources for current balancing in this proposal. Without linear current regulators, the proposed driver offers relatively high efficiency. Its structure is simpler than multiconverter structures for red, blue, and green LED applications, and is particularly suitable for LEDs with wide parameter variations. The performance of the proposed driver is experimentally verified by a 16.5-W prototype with a load of three 5.5-W LED strings. © 2006 IEEE.published_or_final_versio