In this paper, a new high step-up current-fed LLC resonant DC-DC converter with a center-tapped transformer is proposed. By selecting the switching frequency to be lower than, but near to, the series resonant frequency of the LLC resonant tank, soft-switching operation of all semiconductors, i.e., zero Voltage switching (ZVS) turn-on of power MOSFETs and zero current switching (ZCS) turn-off of diodes is achieved. This leads to lower electromagnetic interference (EMI) and lower switching losses and improves the converter efficiency. An interleaved structure is used at the primary side. Thus, input current Ripple is smaller, and its frequency is twice the switching frequency. Consequently, a smaller input filter is necessary in practice. The converter with 1.2 kW Output power and 760 V regulated Output Voltage with 80-200 V input Voltage variations is simulated. The Output Voltage is regulated by using asymmetric pulse width modulation (APWM) at 200 kHz switching frequency. Finally, a 700-W prototype has been implemented and experimental results are also presented to verify the simulation results.

Fluctuations and Ripples in Voltage or current of DC power systems cause different malfunctions in operation of equipments and systems which are supplied by low quality distribution power systems. Therefore Ripple reduction of Voltage or current in DC power systems is very important. In this paper a new method is proposed to reduce Ripple of DC Voltage in high power system using an active power noise cancellation filter (APNCF). In the proposed method a hybrid system including series and parallel active filters for Ripple reduction of load Voltage and source current is used. Simulation and experimental results show the performance of the proposed method in dynamic and static states.  

A novel ultra-high compliance, low power, very accurate and high Output impedance current Output stage (COS) with extremely high Output current drive capability is proposed in this paper. The principle of operation of this unique structure is discussed, its most important formulas are derived and its outstanding performance is verified by HSPICE simulation in TSMC 0.18mm CMOS, BSIM3, and Level49 technology.This deliberately composed structure utilizes a well combination (for a mutual auto control action) of negative and positive feedbacks to achieve ever demanded merits such as very low power of 150mW, ultra high ratio of 3000 for Output current over the bias current (which is selected to be 0.5mA) at low THD of -20dB and very high Output impedance of 5GWwith power supplies of ±0.5V when operating at class AB mode. Simulation results with ±0.5V power supply shows an absolute Output Voltage dynamic range of 0.9V which interestingly provides the highest yet reported Output Voltage compliance for Current mode building blocks implemented by regular CMOS technology. Full process, Voltage, and temperature variation (PVT) analysis of the circuit is also investigated in order to approve the well robustness of the structure. The transient stepwise response is also done to verify the proposed COS stability.

This paper presents a novel method for controlling torque and stator flux Ripples in DTC control of PMSM motor. In contrast to conventional duty ratio modulation methods which do not pay attention to stator flux condition, the proposed method controls both torque and stator flux RMS Ripples using minimization of a proper two variable (stator flux and torque) objective function. After realizing that, flux related machine specifications such as circular stator flux vector trajectory and current waveform quality will be developed. For this purpose, in addition to torque dynamics in any DTC control cycle, stator flux dynamics will be studied. Using this, the condition of both torque and stator flux at the end of an applied Voltage vector of inverter is predicted. Then, standard deviation of torque RMS Ripple and that of stator flux is studied in any control cycle and the normalized sum of these two deviations will be considered as the objective function. Finally, a proper switching instant during any control cycle is calculated for minimizing the objective function. The proposed method is validated by MATLAB simulation.

A multiphase sinusoidal oscillator (MSO) using dual Output Voltage differencing buffered amplifier (DO-VDBA) is presented in this paper which provides n equally spaced phase sinusoids of equal magnitudes. The proposed MSO topology is realized using the first order all pass network (APN). In the proposed structure the Output Voltages are made available at low impedance nodes which makes the proposed MSO easy for cascadability. Making the proposed structure a resistorless structure is a major challenge. The main benefits of the structure are easy integration and less power losses. The formulation of frequency and condition of oscillation is derived mathematically. The oscillation frequency can be tuned electronically, is an added advantage of the proposed MSO. The effect of device non-idealities is also discussed in the study. To assess the proposed MSO performance further Monte Carlo analysis was carried out. The workability of the proposed structure is verified through SPICE simulations for a three (n=3) and four (n=4) phases MSO, and the obtained simulated results are in close agreement with the theoretical values. The total harmonic distortion (THD) is found to be quite low.

Statement of Problem: The success rate of light composite restorative treatments is in close relation to the light intensity of the light curing units.Purpose: The purpose of this study was to evaluate the rate of light intensity of visible light curing units, before and after Voltage stabilizer application.Materials and Method: This study was performed on 82 light curing units in all clinics and dental offices of Yazd city. For evaluating light exit intensity, Hilux radiometer was used. At first, the light intensity was measured, and then by use of 220 V electrical Voltage stabilizer the light exit intensity was recorded. Results were analyzed using Pearson and Spearman tests.Results: Mean range of light intensity before and after Voltage stabilizer was 241.3 and 272.6 mW/cm2 respectively. There were statistically significant differences between before and after use of Voltage stabilizer (p<0.05). Considering the light intensity, 64.7% of the light curing units were suitable for optimum curing and 8.6% were in group that required increase light exposure time.21.9% did not completely cure the composites, and 4.8 % were in group with higher light intensity 2 (over 500 mW/Cm2).Conclusion: Light intensity Output of the curing units in dental clinics of Yazd city were less than expected, but by using Voltage stabilizer, the light intensity was significantly increased.