Showing papers on "Small-signal model published in 2004"

Current distribution control design for paralleled DC/DC converters using sliding-mode control

Abstract: This paper shows the analysis and design of a parallel-connected converter system using sliding mode control techniques. The design is particularised for a system that consists of N boost converters and a current feedback loop based on a proportional-integral compensator of the output voltage error. The paper emphasises the advantages of the sliding-mode control over the classic design method based on small-signal models, thus providing an effective and robust means of controlling nonlinear multi-input converters. The design is based on the Utkin conditions, which permit us to know the regions under which a sliding mode exists. This fact allows us to design the compensator and to introduce some modifications in the control loop that avoids input-current overshoots during the system startup. Simple design expressions are obtained and verified with simulation and experimental results, thus showing the improvements achieved with the proposed modifications.

A new design method for PI-like fuzzy logic controllers for DC-to-DC converters

Abstract: This paper proposes a novel design procedure of Pi-like fuzzy logic controller (FLC) for DC-DC converters that integrates linear control techniques with fuzzy logic. The design procedure allows the small signal model of the converter and linear control design techniques to be used in the initial stages of FLC design. This simplifies the small signal design and the stability assessment of the FLC. By exploiting the fuzzy logic structure of the controller, heuristic knowledge is incorporated in the design, resulting in a nonlinear controller with improved performance over linear PI controllers.

Straightforward determination of small-signal model parameters for bulk RF-MOSFETs

Abstract: An analytical methodology to extract MOSFET's extrinsic and intrinsic small-signal parameters is presented in this paper to perform accurate simulations at high-frequencies. In contrast to previously reported approaches, the one proposed here allows the direct and simple extraction of the gate, substrate, and bias dependent source and drain resistances from measured S-parameters. Excellent agreement between simulated and experimental data up to 27 GHz for a 0.18 /spl mu/m channel-length MOSFET validates this fast and accurate methodology.

D-Q models for resonant converters

Abstract: A systematic modeling method for resonant converters is proposed. This method develops low frequency D-Q models for resonant converters. For a given resonant tank, its orthogonal counterpart is constructed. By combining these two orthogonal tanks, a complex circuit is obtained. The complex circuit is then expressed into a D-Q form circuit. Every variable in the D-Q circuit can be treated as a rotating vector with its envelope modulated by a low frequency function. By removing high frequency terms, the low frequency D-Q model of the resonant converter is derived. This D-Q model has a DC operating point and can predict large signal transitions of the resonant converter with little computation. By perturbing the D-Q model around its DC operating point, equivalent circuits for the small signal models are derived. As an example, the series-parallel resonant DC/DC converter is analyzed by the proposed method. Startup process by the D-Q model agrees with the PSPICE simulation results very well. From the equivalent circuits of the small signal model, transfer functions of input-to-output, control-to-output are obtained as well as the output impedance. They are all verified by SIMPLIS simulation. This modeling technique is applicable to any resonant converter and need little computation.

Study on state-space averaging method for theodolite PWM servo control system

Abstract: The state-space averaging method is presented for the design of PWM (pulse width modulation)-controlled DC motor used in the electro-optical theodolite servo system, especially, using the bipolar DC servomotor with the full bridge main circuit, the transfer functions between the output angular velocity /spl omega/ and the duty ratio of PWM d and the input voltage Vs are proposed, the small signal model of PWM DC servomotor is also analyzed. Based on the model, the simulation and actual experimental results are verified. Moreover, the capability and effectiveness of the ideas used in other controlled mode motor are also significant.

Characterization and modeling of InGaP HBT low-frequency oscillations

Abstract: Audio and near-audio frequency oscillations of InGaP heterojunction bipolar transistors (HBT) devices at room temperature have been observed in an environment typical of high-frequency S-parameter device characterization systems. The oscillations are attributed to sufficient phase shift of the low-frequency thermal impedance in combination with a reactive input impedance resulting in system instability. The oscillations are demonstrated through transient circuit simulations using vertical bipolar intercompany models and predicted using a simple small-signal model.

An asymmetrical half bridge DC-DC converter: close loop design in frequency domain

Abstract: In this paper, the small signal model analysis of an asymmetrical half-bridge DC-DC converter (AHBC) operating in the continuous conduction mode (CCM) is presented. The influence of the non-ideal components to the system performance is discussed. Based on the small signal model, the close loop feedback is designed in the frequency domain for a PI controller and a lead-lag controller. The design criteria for the close loop feedback are described and a clear design process for the feedback compensator is presented. How to achieve the optimum bandwidth and phase margin under the influence of the complicated system structure is investigated. The close loop system load dynamic response from a 12 V/4 A experiment circuit is obtained.

A PSPICE-based design of DC-DC converter systems

Abstract: A new approach to using PSPICE in designing DC-DC converter systems is introduced in this paper In this new approach, the power stage and control loop design equations are programmed in PSPICE For this purpose, an option available in PSPICE called analog behavioral modeling (ABM) is used By doing so, the parameter of power stage and the component values of the error amplifier can be easily obtained by means of PSPICE DC analysis The methodology of development is presented in some detail A design example is included to demonstrate the effectiveness of the proposed approach In designing DC-DC converter systems

Resonant Transition Topologies For Push-Pull And Half-Bridge DC-DC Converters

Abstract: Switched mode power supplies (SMPS) are being extensively used in most power conversion processes. The analysis, design and modeling processes of hard-switched converters are mature, where the switching frequency was limited to a few 10's of kHz. The present direction of evolution m SMPS is towards higher efficiency and higher power density. These twin objectives demand high switching frequency and low overall losses. Soft switching results in practically zero switching losses and extends the switching frequency to 100's of kHz and beyond. This thesis presents novel variants of push-pull and half-bridge DC-DC converters with soft switching properties. The proposed topology uses two additional switches and two diodes. The additional switches introduce freewheeling intervals m the circuit and enable loss-less switching. Switch stress, control and small signal model are similar to hard-switched PWM converter. Synchronous rectifiers are used in the ZVS push-pull converter to achieve high efficiency. It is interesting to see that the drives for the synchronous rectifier device are practically the same as the additional switches. The contributions made in this thesis are 1) Idealized analysis and design methodology for the proposed converters. 2) Validation of the design through circuit simulation as well as prototypes - a 300kHz, 200W push-pull converter and a 300kHz, 640W half-bridge converter. 3) Closed loop control design for desired bandwidth and accuracy Verification of loop gain through network analyzer instrumental for the same The loop gain bandwidth achieved is about 30kHz for the push-pull converter and 20kHz for half-bridge converter. An appendix has been devoted to explain the use of network analyzer. Characterization of coil, transformer and capacitor are explained in detail. Measurement techniques for measuring the small signal parameters of power supply are also explained in the appendix.

Self-sustained oscillation series-parallel resonant converter with the high frequency effects: analysis, modeling, and design

Abstract: A more simple but accurate representation of the series-parallel resonant converter working under the self-sustained oscillation mode with the effect of transformer leakage inductance is presented. The detailed analysis allows the description of the steady state characteristics and the design optimization also enables the accurate derivation of the small signal model in order to predict the dynamic performance successfully. The averaged state space technique is employed to extract the small signal model together with the time domain analysis only used to calculate the boundary values. As a result, the analysis enjoys the simplicity of the state space averaging technique and the accuracy of the time domain analysis. Analytical and simulation results coincide with the outcomes of the experimental work to validate the superiority of the proposed work.

The Analysis of Parallel Operating Characteristics for DC-DC Converter Using the Parallel Operation Model

Abstract: Consideration for parallel operation in a high power system has been increased due to the advantages of parallel operation like as high productivity, simplicity of design, and redundancy of power. Based on the small signal model of DC-DC Converter, the simple and exact power stage model of parallel operation system is derived and the parallel operation system using current balance method for the uniform current distribution among the parallel operation system is proposed. Using Simulation programs, which consists of nonidentical Converter modules and changes the position of master and slave automatically, the current distribution error is kept within the limit in the parallel operation system. To verify the high performance of the proposed Converter system for parallel operation, the parallel operation test, which has 2 Converter modules of 1 kW, is accomplished. Also, the simulation result is good agreement with the experiment result in the transient and starting characteristics.

Direct extraction of small-signal model parameters for nanoscale MOSFETs

Abstract: A small-signal model of a nanoscale MOSFET becomes very important for designing RFICs and characterizing processes and devices. To extract parasitic resistances and inductances, a direct method presented in D. Lovelace et al. (1994) based on S-parameter measurements at zero bias is developed, but the assumption of zero transconductance (g/sub gm/) and output conductance (g/sub ds/) at external Vgs=0V is not valid in real MOSFETs. Thus, Z-parameter extraction equations as stated in D. Lovelace et al. (1994) result in significant error according to the selected frequency range. Another extraction method according to S. Lee (2003) using a linear regression of high-frequency data has been proposed to determine resistances and inductances, but much higher frequency data are required to apply for nanoscale MOSFETs, because of high g/sub m/ and g/sub ds/. In this paper, a direct method to extract resistances and inductances of nanoscale MOSFETs is proposed using a linear regression of high-frequency data at zero gate voltage.

Design of a digital linear controller for a single-phase UPF two-stage boost rectifier using the dSPACE tool of Matlab/Simulink

Abstract: This paper presents the performance of a linear control technique applied to an averaged model of a single-phase UPF two-stage boost rectifier This technique consists of applying the frequency-domain linear control theory on a small signal model of the converter It is then numerically downloaded on dSPACE hardware using the Matlab/Simulink tool, so that it could be applied on a real model of the converter The characteristics of the proposed control scheme are discussed and compared in both steady state and transient regimes (load and voltage disturbance)

Optimizing SiGe HBTs technology using small-signal and high frequency noise device's modeling

Abstract: The rapid expansion of SiGe technologies during the last decade essentially due to civil telecommunication's applications have led Si/SiGe based heterojunction bipolar transistors (HBTs) to excellent performance levels, allowing high frequency low noise circuit designs such as linear low noise amplifiers( RF noise) or also low-phase noise oscillators (LF noise) Among these technologies, the SiGe BiCMOS one integrates digital and RF functions on the same chip Fast improvements of the technological process have been performed thanks to large efforts allowed to characterization and modeling of the devices We have investigated on the influence of technological parameters such as Germanium profile, doping level and thickness of the base layer (5 different wafers) on the dynamic and high frequency noise performances to converge towards the optimum technological process (now available with the BiCMOS6G processed by ST microelectronics) We made use of scattering parameters [S] measurements on the devices to extract the electrical parameters of our small signal model The high frequency noise parameters based on the electrical model (with noise sources added to the junction, resistances) are simulated and compared with the measured noise parameters of the devices The four noise parameters (Fmin, Rn, and complex Topt) measurements have been performed from 1 GHz to 12 GHz, and the dynamic S parameters measurements have been realized in the 40 MHz-40 GHz range These models have been used to enable the identification of the limiting parameters on the dynamic performances and on the high frequency noise parameters

A novel direct parameter-extraction method for GaInP/GaAs HBTs small-signal model

Abstract: An accurate and broadband method for heterojunction bipolar transistors (HBTs) small-signal model parameters is presented in this article. This method differs from previous ones by extracting the equivalent-circuit parameters without using a special test structure or global numerical optimization techniques. The main advantage of this method is that a unique and physically meaningful set of intrinsic parameters is extracted from impedance and admittance representation of the measured S-parameters in the frequency range of 1–12 GHz under extracted-bias conditions. An equivalent circuit for the HBT under a forward-bias condition is proposed for extraction of access resistance and parasitic inductance. The method yields a deviation of less then 5% between the measured and modeled S-parameters. © 2004 Wiley Periodicals, Inc. Int J RF and Microwave CAE 14, 447–452, 2004.

A π Small-Signal Model of MEMS Series Switches Based on the Parameter- Extraction Method

Abstract: A novel π small-signal model of MEMS series switches is presented based on a parameter-extraction method, which can determine a fringing capacitance (C_f) in the end of each signal line as well as a contact resistance (R_c) For an on-state modeling, the average error of S₁₁ for the π model is 51% in the range of 5~35 GHz, whereas that of the conventional model of two-port series-impedance without C_f is 1672 % It is noted that the conventional model is not valid anymore for the on-state model and C_f should be taken into account The small-signal modeling by the proposed π model demonstrates the validity of the approach

A combined model for Si-based resonant interband tunneling diodes grown on SOI

Abstract: In this paper, we present a combined model which unites both the small and large signal models for resonant interband tunneling diodes (RITD) grown on silicon-on-insulator (SOI) substrates. In this combined model, the dependent current source, I/sub j/(V), is from the large signal model while R, and C/sub j/(V) are obtained from the small signal model. The combined model was then implemented using ADS software. A transient simulation was performed to simulate the response of the RITD with a serially connected 50 /spl mu/H inductor to a ramped voltage from 0 V to 1 V in 0.1 ms. The simulation results show strong oscillations when the diode is biased in its negative differential resistance region (NDR) during DC measurements, which would result in the commonly observed plateau in the NDR region, where the needle probe acts as an inductor.