Applied Mechanics and Materials Vols. 764-765

Abstract: In this paper, we propose a side-peak cancellation scheme for unambiguous BOC signal tracking. We obtain partial correlations using a pulse model of a BOC signal, and then, we finally obtain an unambiguous correlation function based on the partial correlations. The proposed correlation function is confirmed from numerical results to provide an improved tracking performance over the conventional correlation functions.

Abstract: A single-stage DC uninterruptible power supply (UPS) is proposed in this paper. Basically, the proposed converter is an integration result of a power factor correction circuit with a dc-to-dc converter to achieve simple hardware circuit, high efficiency, and low cost for extra UPS function. Under normal operation, a novel two-switch SEPIC converter operates as an ac to dc converter with sinusoidal input current, unity power factor, and low ripple dc output voltage, and as a battery charger if a battery is added. Since both the input boost supply and the output supply can be controlled independently, a fast transient response can be maintained at both the input for active current wave shaping and at the output for good output regulation. When the ac source is in an outage condition, the proposed converter functions as a dc-to-dc buck-boost converter; therefore, the desired dc output voltage can be provided. Finally, some experimental results are presented for verification.

Abstract: The new digital control loop of the low-dropout regulator (LDO) is presented. It is composed of coarse tracking circuit and fine tracking circuit, and no external output capacitor is required to stabilize the control loop. The proposed method makes the quiescent current lower than conventional analog LDOs. The operational amplifier of the conventional LDO fails to operate at 0.7V, and the developed digital LDO in 0.18um CMOS achieved the 0.7V input voltage and 0.5V output voltage with 99.99% current efficiency and 2.6-μA quiescent current at 20mA load current. Therefore, the proposed DLDO is suitable for low power applications.

Abstract: Mobile wireless communication is the fastest growing segment of the communication industry. However, it is faced with the challenge of providing reliable high-speed communications due to channel impediments which change over time in unpredictable ways. To analyze the reliability and performance of real communication system, the Rayleigh fading channel is generally applied to simulate the real wireless communication. In this paper, we analyze and implement a flat Rayleigh fading channel based on the inverse discrete Fourier transform (IDFT). The simulation results of level crossing rate (LCR) and average fade duration (AFD) are shown in this paper.

Abstract: In this paper, a method for earth potential computation of layered soil structure is discussed. To calculate thermal field of the transformer with dc bias, simulation models using MAXWELL and COMSOL are proposed. Based on the electromagnetic analysis, electric power loss resulted in temperature rise is calculated. Under the case of normal operation of transformer, a research was carried out to compare the abnormal changes of temperature of transformer. It worked out that if there are different DC parts in transformer, the loss will increase with DC bias and the temperature of transformer core will also increase. If it is increasing continuously and no preventive measures are taken soon, the thermal aging of some parts in transformer will speed up and gradually affect the normal operation of transformer. The research lays the groundwork for further research of transformer DC bias and aging.

Abstract: We demonstrate a novel design of large-size device in AlGaN/GaN high-electron-mobility transistor (HEMT). Depletion mode (D-mode) HEMTs and enhancement mode (E-mode) HEMTs are fabricated in our research. The saturation current of D-mode HEMTs is over 6A. By using Cascode structure, the D-mode HEMT becomes a normally-off device efficiently, and the threshold voltage of it rises from-7V to 2V. By using BCB (Benzocyclobutene) as the passivation, the E-mode HEMT shows an excellent characteristic. Also, when the V_GS of the E-mode HEMT is over 9V, it still shows a good performance.

Abstract: For high-power applications such as electric motorcycles, batteries in series to provide the required voltage is fairly common. The 48V is 12V connected four cells in series for lead-acid batteries of electric motorcycles. After charging and discharging of lead-acid batteries several times, the voltages are often imbalance. Without proper protection, may cause an excessive discharge of lead-acid batteries for early damage. Therefore, lead-acid battery module requires a simple balance circuit to improve battery life in order to avoid over-voltage or under-voltage condition occurs. Energy balance circuit to improve lead-acid battery module matching problems, make the safety and cycle life of lead-acid batteries to improve. This research intends to complete balanced circuit design of lead-acid batteries.

Abstract: This work presents a hardware implementation of a simple microprocessor; then uses this microprocessor to design a PI controller for PMSM (Permanent Magnet Synchronous Motor) drives. In this paper, firstly, the mathematical model of PMSM drives is illustrated. Secondly, the architecture of a simple microprocessor based on RTL (Register Transfer Level) method is proposed and the VHDL (Very high speed IC Hardware Description Language) is adopted to describe the behavior of the simple microprocessor. Thirdly, a machine code of PI controller based on the proposed simple microprocessor is designed. Finally, a co-simulation by Simulink/ModelSim is applied and verified the performance of the microprocessor-based PI controller.

Abstract: The electromagnetic radiation emission model of motor drive System for electric vehicles (EVs) is presented in this paper. First, the radiation electromagnetic interference (EMI) mechanism of the motor drive system is analyzed and investigated by experiment. The radiation EMI mainly comes from the common mode current flowing along the three phase cable between the inverter and the motor. Secondly, the feasibility of the finite element method (FEM) is verified by calculating the wire electromagnetic field around and the radiation EMI model of the motor drive system is established using the FEM. The simulation and experimental results show that the proposed model is feasible.

Abstract: This paper proposed an improved bootstrapped type high-efficient charge pump circuit based on the Dickson charge pump in order to get a higher pumping efficiency. It is not only avoid the threshold voltage drop in conventional Dickson charge pump circuits but enable them to generate a higher output voltage. Simulation by HSPICE shows that for conventional Dickson charge pump, it convert the input low DC-voltage (V_in=1.5V) up to 3.8 times of it (V_OUT=5.77V), the pump efficiency was 76.93%. Our work, however, can convert the low input DC-voltage (V_in=1.5V) up near to 4.76 times of it (V_OUT=7.14V), the pump efficiency can reaches as high as 95.2%.