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    Switched-resistor: A new family of sampled-data circuits

    , Article AEU - International Journal of Electronics and Communications ; Volume 63, Issue 5 , 2009 , Pages 366-373 ; 14348411 (ISSN) Sedighi, B ; Bakhtiar, M. S ; Sharif University of Technology
    This paper introduces "switched-resistor" circuits as a new family of current-mode sampled-data circuits with improved accuracy and linearity. Advantages of the switched-resistor circuits for high-speed and low-voltage applications are demonstrated. A switched-resistor biquad band-pass filter with a quality factor of 10 and clock frequency of 100 MHz, fabricated in a 0.18 μ m CMOS process, is also presented. The filter consumes 9 mW from 1.8 V supply. © 2008 Elsevier GmbH. All rights reserved  

    Analysis of Phase-Shifted Full-Bridge Based dc-dc Converter considering transformer parasitic elements in discontinuous current mode

    , Article PEDSTC 2014 - 5th Annual International Power Electronics, Drive Systems and Technologies Conference ; 2014 , p. 366-372 Aghaei, M ; Karimi, Y ; Kaboli, S ; Sharif University of Technology
    In high-voltage applications, due to the use of high-ratio step-up transformers, the value of parasitic capacitance of these transformers is large compared to the low-voltage transformers. Moreover In these applications it is prefered to use single-capacitor filters instead of filters with inductors. In this paper a simple electrical model for two-winding high frequency transformer considering all of the parasitic elements is presented. This model is used in a full-bridge based dc-dc converter with capacitive output filter controlled by phase-shifted method. The operation of this converter in DCM is analysed and its analytical relations in different time intervals is derived and confirmed by... 

    Design and Fabrication of Buck-Boost DC-DC Converter and Linear Regulator With Digitally-Tunable Output Voltage in 0.18µm-HV BCD CMOS Process

    , M.Sc. Thesis Sharif University of Technology Kargaran, Masoud (Author) ; Medi, Ali (Supervisor)
    In this project, an inverting Buck-Boost converter with two negative linear regulator is designed, implemented and measured in CMOS 0.18μm-HV BCD technology. Input voltage of Buck-Boost converter can vary from +15V to +28 and output voltage is digitally adjustable from -1V to -10V. Maximum output current of the converter is 300mA. A current mode controller and a lag compensator is used to control the converter. A high speed highside current sensor is designed and used in current mode controller. Sampled current of the current sensor is also used in a current limit circuitary to limit the maximum current of highside switch. Two negative linear regulators are placed at the output of the... 

    Modification of nanostructured anodized aluminum coatings by pulse current mode

    , Article Surface and Coatings Technology ; Volume 278 , 2015 , Pages 48-55 ; 02578972 (ISSN) Mohammadi, I ; Afshar, A ; Sharif University of Technology
    Elsevier  2015
    In this study, the effects of pulse current mode on corrosion resistance and mechanical properties of anodized coatings were explored. Thickness and hardness measurements, polarization and electrochemical impedance spectroscopy were employed to take mechanical and corrosion behaviors of the anodized coatings into consideration. Also, field-emission scanning electron microscopy (FE-SEM) was utilized to characterize the surface morphology of the coatings. It was shown that in short anodizing times, coating thickness is controlled by the heat concentrated on coating. Although at prolonged anodizing times, the coating thickness is affected by average current density. Hardness measurements showed... 

    A new low voltage, high PSRR, CMOS bandgap voltage reference

    , Article 2008 IEEE International SOC Conference, SOCC, Newport Beach, CA, 17 September 2008 through 20 September 2008 ; 2008 , Pages 345-348 ; 9781424425969 (ISBN) Ashrafi, S. F ; Atarodi, M ; Chahardori, M ; Sharif University of Technology
    A new low voltage bandgap reference (BGR) in CMOS technology, with high power supply rejection ratio (PSRR) is presented. The proposed circuit uses a regulated current mode structure and some feedback loops to reach a low voltage, low power and high PSRR voltage reference. The circuit was designed and simulated in 0.18um CMOS technology, with a power supply of 1.4 volt. The results show PSRR is 65dB at 1MHz and the output voltage variation versus temperature (-40 to 140) is less than 0.1%. This circuit shows robustness against process variation. ©2008 IEEE  

    A compact mixer and DAC for implementation of a direct conversion OQPSK transmitter

    , Article 2007 IEEE Region 10 Conference, TENCON 2007, Taipei, 30 October 2007 through 2 November 2007 ; 2007 ; 1424412722 (ISBN); 9781424412723 (ISBN) Chahardori, M ; Mehrmanesh, S ; Zamanlooy, B ; Atarodi, M ; Sharif University of Technology
    A compact low power circuit for implementation of a direct conversion OQPSK modulator is proposed. The circuit consists of a digital to analog converter, a low pass filter and an up-converter mixer. By embedding these three blocks, the circuit performance is enhanced and the total power consumption is reduced. The mixer is designed base on a Gilbert cell with on chip inductor loads. Instead of transconductance transistors of Gilbert cell, a fully deferential current mode DAC is used and proficiently a low pass filter is embedded between them and therefore the linearity of total system is improved. All of circuits are designed based on 0.18 μm CMOS technology with a single 1.8 volt power... 

    A fully ZVS critical conduction mode boost PFC

    , Article IEEE Transactions on Power Electronics ; Volume 27, Issue 4 , October , 2012 , Pages 1958-1965 ; 08858993 (ISSN) Marvi, M ; Fotowat Ahmady, A ; Sharif University of Technology
    Boost converter operating in critical conduction mode is widely used in low-power power factor corrector because of its simplicity and low switching losses. The switching loss due to parasitic capacitor discharge at the on-time instant can also be reduced by a valley switching technique. In this paper, we introduce a new driver topology for the high-side switch in a synchronous boost converter operating in the critical conduction mode to obtain full zero-voltage switching. Using the proposed high-side driver topology, the conventional control circuit is sufficient to control the low-side switch, and no additional control circuit is required to adjust the timing of the switches. Finally, the... 

    A sub 1 v high PSRR CMOS bandgap voltage reference

    , Article Microelectronics Journal ; Volume 42, Issue 9 , 2011 , Pages 1057-1065 ; 00262692 (ISSN) Chahardori, M ; Atarodi, M ; Sharifkhani, M ; Sharif University of Technology
    A Bandgap circuit capable of generating a reference voltage of less than 1 V with high PSRR and low temperature sensitivity is proposed. High PSRR achieved by means of an improved current mode regulator which isolates the bandgap voltage from the variations and the noise of the power supply. A vigorous analytical approach is presented to provide a universal design guideline. The analysis unveils the sensitivity of the circuit characteristic to device parameters. The proposed circuit is fabricated in a 0.18μm CMOS technology and operates down to a supply voltage of 1.2 V. The circuit yields 20 ppm/°C of temperature coefficient in typical case and 50 ppm/°C of temperature coefficient in worst... 

    Global hybrid modeling and control of a buck converter: a novel concept

    , Article International Journal of Circuit Theory and Applications ; Volume 37, Issue 9 , 2009 , Pages 968-986 ; 00989886 (ISSN) Hejri, M ; Mokhtari, H ; Sharif University of Technology
    Several attempts have been made to design suitable controllers for DC-DC converters. However, these designs suffer from model inaccuracy or their inability to desirably function in both continuous and discontinuous current modes. This paper presents a novel switching scheme based on hybrid modeling to control a buck converter using mixed logical dynamical (MLD) methodologies. The proposed method is capable of globally controlling the converter in both continuous and discontinuous current modes of operation by considering all constraints in the physical plant such as maximum inductor current and capacitor voltage limits. Different loads and input voltage disturbances are simulated in MATLAB... 

    Hybrid predictive control of a DC-DC boost converter in both continuous and discontinuous current modes of operation

    , Article Optimal Control Applications and Methods ; Volume 32, Issue 3 , 2011 , Pages 270-284 ; 01432087 (ISSN) Hejri, M ; Mokhtari, H ; Sharif University of Technology
    Developing efficient and appropriate modeling and control techniques for DC-DC converters is of major importance in power electronics area and has attracted much attention from automatic control theory. Since DC-DC converters have a complex hybrid nature, recently several techniques based on hybrid modeling and control have been introduced. These techniques have shown better results as compared with conventional averaging-based schemes with limited modeling and control abilities. But the current works in this field have not considered all possible dynamics of the converters in both continuous and discontinuous current modes (CCM, DCM) of operations. These dynamics are results of controlled...