Applied Mechanics and Materials Vols. 284-287

Abstract: In this paper, we propose an efficient VLSI architecture for implementing the forward two-dimensional discrete wavelet transform (2D DWT), which is computed without utilizing the traditional method of rows-by-columns or columns-by-rows. On account of the relation form within the original data, we apply masks of different window sizes to the transform and design the architecture based on these different window masks. On the comparison of the computing time, the proposed architecture requires only N*N/4 clock cycles for an N*N image, while it takes N*N clock cycles for the traditional row-by-column/column-by-row 2D DWT. The proposed architecture has a better performance than other designs reported in the literature.

Abstract: Airborne panel series circuit modules are used to process and transform the information between the aircraft cockpit control panels and the avionics system. A kind of test system software design for the airborne panel series circuit modules using the PXI host system as the testing platform is introduced in this paper. The test system architecture, software design idea and realization method are also discussed. In order to test the airborne panel series circuit modules, whose all kinds of interface signals are needed to provide according to the circuit modules’ test requirements. The most important function of test system is to provide excitation signals to the tested object, while the response signals of the tested object is collected, so the test results can be formed by the test criterion. In the software design, the different test processes are used for the different test objects. The test work can be completed according to the test process, the test data and test results formed in the test can be saved to the database. In the test process, the connection between the test program and database is established. All test data and results are managed by the private database management system. The entire test system uses the top-down design methodology, and host computer adopts PXI system to control the tested modules. The test system has been well applied in project, and its stability and excellent performance have been proved in experimental work.

Abstract: Light emitting diodes (LEDs) have substituted for incandescent bulbs and fluorescent lamps gradually in the residential, industrial and commercial lighting applications. This paper proposes an active clamp forward converter with the sequential color display (SCD) control to drive red, green and blue (RGB) LED arrays. Both of the main switch and the auxiliary switch can turn on under zero voltage switching (ZVS), resulting in high system efficiency. RGB LED arrays are sequentially driven by the same converter, which can save components and reduce cost significantly. Besides, the pulse-width modulation (PWM) control is applied to achieve a large chromaticity variation. The operation principles of the proposed LED driver are addressed. Experimental results of a 100W laboratory prototype are used to verify the feasibility and validity of the theoretical predictions.

Abstract: This paper presents a systematic approach to developing turn-off snubber for an interleaving converter to smooth out switch turn-off transition. With the approach, the interleaving converter with two turn-off snubbers, which are formed by two L-C-D type snubbers, can be replaced by the one with turn-off snubber composed of a single-capacitor snubber. It can be used in the basic six interleaved converters, such as buck, boost, buck-boost, ‘cuk, zeta and sepic converters. In this research, the structure of the interleaved converter with the turn-off snubber can be conveniently simplified from the derived general configurations, reducing the complexity of circuit structure significantly. Measured results from a buck prototype converter have been verified to prove the feasibility of the derived turn-off snubber.

Abstract: Memristor is a nonlinear resistance with the ability of memory and its resistance depends on the amount of charge or magnetic flux. As a new circuit component, the memristor is not only expected to promote the evolution of electronic industry but also has huge potential application in many fields because of its small size, low energy consumption and be large scale integrated easily. In this paper according to the mathematical model of memristor based on a piecewise-linear function, the characteristics of memristor series-parallel connection circuit are analyzed by MATLAB and SPICE simulations. A series of simulation results show that the memristive series-parallel network is still a nonlinear element, the resistance value of memristor depends on the initial condition greatly and the electronic characteristics are more complex. It is also applied to the ladder signal generator which can be used in the controller circuit.

Abstract: Both the fuel cell and battery have timely dynamic response to the step-profile load input. The current overshoot followed by a voltage undershoot behavior happen the step-up load, particularly. These phenomena are closely related to mass transfer mechanisms such as the water/gas transport by the redistribution of membrane water content in the fuel cell and the charge double-layer effect in the battery. When the load demand is beyond the rated power of the fuel cell system, the battery immediately powers to the load with a transient discharging current especially in the step-profile load power. This study presents a new control strategy for hybrid fuel cell-battery power sources with transient and overshoot considered. The results show that the proposed hybrid fuel cell-battery power source not only acting as a power stabilizer but also dynamically satisfying the step-profile load demand.

Abstract: In this paper, a robust tracking fuzzy controller using time-varying sliding regime is proposed for UPS systems. The controller combines the merits of sliding regime control, fuzzy logic control. Time-varying sliding surface is used to ensure the existence of sliding regime from an initial state, while the conventional sliding surface can not achieve the robust performance against disturbances before the sliding regime occurs. Fuzzy technique is applied to select a dominated sliding surface when errors lie in the second and the fourth quadrants and shift a predetermined sliding surface when errors lie in the first and the third quadrants in order to achieve the propose of fast and robust tracking. Using the proposed method, the magnitude of the control input signals and undesirable chattering phenomenon are remarkable lessened and simultaneously improves the robustness of the UPS system. Simulation results are presented, showing a good dynamic performance of the proposed method.

Abstract: This paper proposes a novel high-step-up DC-DC power converter for high output-voltage applications from a low level of input voltage. The presented power converter is composed of a integrated boost-flyback converter with two output windings plus cascaded voltage doublers to boost up the 12 V input voltage to a high DC voltage level of 400 V. Description of the presented DC-DC power conversion circuit, and experimental results of a prototype converter for providing 40W output power with a 12V input DC voltage are demonstrated.

Abstract: In this study, a new clock and ramp generator circuit framework with a 0.9V low operational voltage is designed for the voltage-mode/current-mode-controlled power management integrated chip of a DC-DC converter. In conventional clock and ramp generator circuit with operational amplifiers, its operational voltage is limited to be over 1.5V because of the problem of a higher threshold voltage in the metal-oxide-semiconductor field-effect transistor (MOSFET). As a result, it can not work well for a pulse-width-modulation DC-DC converter when a below 1V low-voltage single-cell clean-energy power source is applied. This newly-design clock and ramp generator circuit framework without operational amplifiers is investigated to cope with the limitation of the threshold voltage in the MOSFET. Therefore, the corresponding chip size and power consumption can be reduced. Moreover, this circuit still has the functions of adjustable clock frequency and ramp slope. In addition, numerical simulations by the HSPICE software and experimental results by a real chip fabricated in the TSMC 1P6M 0.18µm CMOS process are given to verify the effectiveness of the proposed circuit to produce the clock and ramp waveforms.

Abstract: This paper proposes a high-efficiency voltage-mode class-D (VMCD) RF power amplifier (PA) for class-S transmitter, which includes additional multi-section bandpass filter (BPF). For an accurate analysis of class-S transmitter, the output signals of band pass delta sigma modulator (BPDSM) are described with probability distribution functions (PDF) versus pulse widths of quantized signals. Usually, the results show that magnitudes of sub-harmonic terms increases for high peak-to-average power ratio signal such as long term evolution (LTE) signal. For a high efficiency and appropriate linearity of class-S transmitter, we propose a VMCD PA utilizing a multi-section BPF. The proposed architecture effectively improves the linearity without deterioration the efficiency. For the LTE signal, the efficiency is 25.82% and adjacent channel power ratio (ACPR) is -52.44dBc when using a one-section BPF. By using the multi-section BPF, ACPR and efficiency have been improved up to 11.88dB and 13.44% respectively. The effectiveness of the proposed design is demonstrated for various input signals.