Robust Nonlinear Current Sensorless Control of the Boost Converter with Constant Power Load

The boost converter feeding a constant power load (CPL) is a non-minimum phase system that is prone to the destabilizing effects of the negative incremental resistance of the CPL and presents a major challenge in the design of stabilizing controllers. A PWM-based current-sensorless robust sliding mode controller is developed that requires only the measurement of the output voltage. An extended state observer is developed to estimate a lumped uncertainty signal that comprises the uncertain load power and the input voltage, the converter parasitics, the component uncertainties and the estimation of the derivative of the output voltage needed in the implementation of the controller. A linear sliding surface is used to derive the controller, which is simple in its design and yet exhibits excellent features in terms of robustness to external disturbances, parameter uncertainties, and parasitics despite the absence of the inductor’s current feedback. The robustness of the controller is validated by computer simulations.

Non-inverting buck-boost DC-DC converter based on constant inductor current control

The hysteresis control combined with PWM control non-inverting buck-boost was proposed to improve the light load efficiency and power density.The constant inductor current control(CICC)was established to mitigate the dependence on the external components and device variation and make smooth transition between hysteresis control loop and pulse width modulation(PWM)control loop.The small signal model was deduced for the buck and boost operation mode.The inductor current slope control(ICSC)was proposed to implement the automatic mode transition between buck and boost mode in one switching cycle.The results show that the converter prototype has good dynamic response capability,achieving 94%efficiency and 95%peak efficiency at full 10 A load current.

Dynamics and stabilization of peak current-mode controlled buck converter with constant current load

The discrete iterative map model of peak current-mode controlled buck converter with constant current load（CCL）,containing the output voltage feedback and ramp compensation, is established in this paper. Based on this model the complex dynamics of this converter is investigated by analyzing bifurcation diagrams and the Lyapunov exponent spectrum. The effects of ramp compensation and output voltage feedback on the stability of the converter are investigated. Experimental results verify the simulation and theoretical analysis. The stability boundary and chaos boundary are obtained under the theoretical conditions of period-doubling bifurcation and border collision. It is found that there are four operation regions in the peak current-mode controlled buck converter with CCL due to period-doubling bifurcation and border-collision bifurcation. Research results indicate that ramp compensation can extend the stable operation range and transfer the operating mode, and output voltage feedback can eventually eliminate the coexisting fast-slow scale instability.

Low voltage substrate current： a monitor for interface states generation in ultra-thin oxide n-MOSFETs under constant voltage stresses

The low voltage substrate current （Ib） has been studied based on generation kinetics and used as a monitor of interface states （Nit） generation for ultra-thin oxide n-MOSFETs under constant voltage stress. It is found that the low voltage Ib is formed by electrons tunnelling through interface states, and the variations of Ib（△Ib） are proportional to variations of Nit （△Nit）. The Nit energy distributions were determined by differentiating Nit（Vg）. The results have been compared with that measured by using gate diode technique.

An improved analysis method of constant-current charge/discharge curves and its application to nickel hydroxide electrode

The derivative of charge and discharge curves (d t /d E vs E plot) can be used to describe the charge and discharge process more exactly. The d t /d E ? 獷 plots of nickel hydroxide electrode at different charge/discharge rates and intermittent discharge experiment are discussed. Though the d t /d E ? 獷 plot is affected by many factors, it clearly has intrinsic relation with the nature of active material such as conductivity and thermodynamic potential of active material, which changes with the state of charge. The d t /d E—E plot can also be applied to other electrochemical active materials, especially to those having several phases during charge or discharge.

Constant Ripple Current Control for Switching DC-DC Converter

The adapted DC-DC converters should be smaller in size and have a small output current ripple to meet the increasing demand for low voltages with high performance and high density micro processors for several microelectronic load applications. This paper proposes a DC-DC converter using variable on-time and variable switching frequency control enhanced constant ripple current control and reduced magnetic components. The proposed converter is realized by making the turn-offtime proportional to the on-time of the converter, according to the input and output voltage, thereby reducing the corresponding current ripple on output voltage in the continuous conduction mode. A Buck DC-DC converter using the proposed control strategy is analyzed in detail, along with some experimental results to show the performance and effectiveness of this converter.

Field-induced phase transitions in chiral smectic liquid crystals studied by the constant current method

In ferroelectric liquid crystals, phase transitions can be induced by an electric field. The current constant method allows these transition to be quickly localized and thus the（E, T） phase diagram of the studied product can be obtained.In this work, we make a slight modification to the measurement principles based on this method. This modification allows the characteristic parameters of ferroelectric liquid crystal to be quantitatively measured. The use of a current square signal highlights a phenomenon of ferroelectric hysteresis with remnant polarization at null field, which points out an effect of memory in this compound.

Multi-stage constant current charging strategy considering SOC intervals and voltage thresholds

Conventional multi-stage constant current charging strategies often use higher multiples of current to charge the battery in pursuit of shorter charging times.However,this leads to an increase in battery temperature,while shortening the charging time.This in turn affects the safety of the charging process.Furthermore,the higher charging currents are not ideal for shortening the charging time in the later stages of charging.To solve the aforementioned problems,in this study,a multi-stage constant current charging strategy is presented.This strategy can shorten the battery charging time by using the increase in battery temperature during the charging process as a constraint,using a genetic algorithm to calculate the charging current value,and investigating the phased approach to charging.Finally,the charging strategy is experimentally validated at different ambient temperatures and different initial SOCs.The experimental results show that the charging strategy proposed in this paper not only reduces the amount of calculations,but also reduces the temperature rise by up to 46.4%and charging time by up to 4.2%under different operating conditions.

Numerical Solution of MHD Convection and Mass Transfer Flow of Viscous Incompressible Fluid about an Inclined Plate with Hall Current and Constant Heat Flux

The present numerically study investigates the influence of the Hall current and constant heat flux on the Magneto hydrodynamic (MHD) natural convection boundary layer viscous incompressible fluid flow in the manifestation of transverse magnetic field near an inclined vertical permeable flat plate. It is assumed that the induced magnetic field is negligible compared with the imposed magnetic field. The governing boundary layer equations have been transferred into non-similar model by implementing similarity approaches. The physical dimensionless parameter has been set up into the model as Prandtl number, Eckert number, Magnetic parameter, Schmidt number, local Grashof number and local modified Grashof number. The numerical method of Nactsheim-Swigert shooting iteration technique together with Runge-Kutta six order iteration scheme has been used to solve the system of governing non-similar equations. The physical effects of the various parameters on dimensionless primary velocity profile, secondary velocity profile, and temperature and concentration profile are discussed graphically. Moreover, the local skin friction coefficient, the local Nusselt number and Sherwood number are shown in tabular form for various values of the parameters.

A Novel Over-Current Protection Technique Applied to Peak-Current Type DC-DC Converter

The change of the over-current protection point of the power switches, caused by slope compensation, is analyzed in detail. It is discovered that the peak current protecting value increases as the duty cycle decreases. As a result, the safety operation of the switches is damaged greatly. A novel solution to improve over-current protection with constant peak current limitation is proposed by inducing synchronous slope compensation into the current limit function instead of the original constant voltage. The design principle and method of the protection circuit based on a UC3846 PWM controller for the interleaved dual-forward converter is presented. Experimental results are given to verify the analysis.

An Adaptive Response Compensation Technique for the Constant-Current Hot-Wire Anemometer

An adaptive response compensation technique has been proposed to compensate for the response lag of the constant-current hot-wire anemometer (CCA) by taking advantage of digital signal processing technology. First, we have developed a simple response compensation scheme based on a precise theoretical expression for the frequency response of the CCA (Kaifuku et al. 2010, 2011), and verified its effectiveness experimentally for hot-wires of 5 μm, 10 μm and 20 μm in diameter. Then, another novel technique based on a two-sensor probe technique—originally developed for the response compensation of fine-wire thermocouples (Tagawa and Ohta 1997;Tagawa et al. 1998)—has been proposed for estimating thermal time-constants of hot-wires to realize the in-situ response compensation of the CCA. To demonstrate the usefulness of the CCA, we have applied the response compensation schemes to multipoint velocity measure- ment of a turbulent wake flow formed behind a circular cylinder by using a CCA probe consisting of 16 hot-wires, which were driven simultaneously by a very simple constant-current circuit. As a result, the proposed response compensation techniques for the CCA work quite successfully and are capable of improving the response speed of the CCA to obtain reliable measurements comparable to those by the commercially-available constant-temperature hot-wire anemometer (CTA).

Pion Decay Constant and Masses of Light Quarks and In-medium Goldstone Bosons

Based on the fully dressed confining quark propagator, the pion decay constant fπ, local quark vacuum condensate, and the masses of light quarks and in-medlum Goldstone bosons are investigated. The pion decay constant fπ is predicted and compared with its value of experimental measurement. A great agreement is obtained. With the predicted fπ and values of Goldstone boson masses measured by experiments in free configuration the current masses of light quarks and the masses of in-medium Goldstone bosons are obtained.

STUDY OF HIGH-STABILITY CURRENT REGULATORS FOR CURRENT FROM 0.1A TO 8A

Improving the temperature stability and widening the constant current range are two important problems to be solved in the application of the current regulators. This paper introduces a modular approach for the design of the current regulator with a very wide current range. The test results show that their output current ranges from 0.1A to 8A, with its current temperature coefficient as low as 10-4/℃ to 10-5/℃ and limiting voltage lower than 0.4V.

Power optimization of photovoltaic modules under varying environmental conditions based on current equalization collaborating with constant voltage control

The performance of photovoltaic(PV)modules is affected by environmental factors such as irradiance and temperature,which can lead to a decrease in output performance or even damage.This study proposes an improved formula for calculating the real maximum power of PV modules by analysing the influence of irradiance and temperature.A simulation model is developed using PLECS software to simulate the global maximum power of PV modules under different environmental conditions and the results are compared with the calculated real maximum power.A power optimization scheme for PV modules is then proposed based on current equalization and constant voltage control.This scheme employs a single-switch multi-winding forward-flyback converter to equalize the mismatched currents between cell strings,thereby enhancing the output performance.Traditional proportional-integral controllers are utilized to achieve constant voltage control and obtain the real maximum power of PV modules.Simulation models are built in the PLECS simulation platform to evaluate the performance of a global maximum power point tracking scheme based on the traditional perturb-and-observe(TPO)algorithm with current equalization,a segment perturb-and-observe algorithm without current equalization,and the proposed power optimization scheme.The simulation results demonstrate that the proposed constant voltage control has greater efficiency than the TPO algorithm.The proposed scheme achieves a significant improvement in efficiency,with a 27.87%increase compared with the segment perturb-and-observe algorithm without current equalization.

Neural network prediction of the shunt current in resistance spot welding

An error back propagation （BP） neural network prediction model was established for the shunt current compensation in series resistance spot welding. The input variables for the neural network consist of the resistivity of the material, the thickness of workpiece and the spot spacing, and the shunt rate is outputted. A simplified calculation for the shunt rate was presented based on the feature of the constant-current resistance spot welding and the variation of the resistance in resistance spot welding process, and then the data generated by simplified calculation were used to train and adjust the neural network model. The neural network model proposed was used to predict the shunt rate in the spot welding of 20# mlid steel （in Chinese classification） （in 2. 0 mm thickness） and 10# mild steel （in 1.5 mm and 1.0 mm thickness）. The maximum relative prediction errors are, respectively, 2. 83%, 1.77% and 3.67%. Shunt current compensation experiments were peoCormed based on the neural network prediction model proposed to check the diameter difference of nuggets. Experimental results show that maximum nugget diameter deviation is less than 4% for both 10# and 20# mlid steels with spot spacing of 30 mm and 50 mm.

Circulating current suppression for ground tied variable frequency to constant frequency converter system in aircraft

This paper presents a solution to the circulating current fault of aircraft power supply.The DC-link type Variable Frequency to Constant Frequency(VFCF)converter system is the preferred scheme to feed the constant 400 Hz load in an aircraft with a variable frequency power supply.Due to the requirement of aircraft standards,both grounds of the rectification and inversion stage are tied to the metal frame of the aircraft.With such a tied ground,the DC bus voltage rises greatly,and a large circulating current appears in the casing as the ground,which leads to equipment failure and potential safety hazards.According to the existing methods of circulating current fault suppression,this paper analyzes the causes of the above faults and the harmonic components of circulating current and points out the limitations of the existing methods.Therefore,a Common-Mode(CM)choke-based method is proposed to provide a high impedance in the path of the CM circulating current.By doing so,the circulating current can be suppressed without the additional burden of the hardware and control algorithm,which is quite friendly for quality control of mass-production aircraft.Moreover,a simplified mathematic model of the VFCF converter system is derived to calculate the minimum inductance value reference of the CM choke,which saves the weight of passive devices to the greatest extent.Finally,simulation and experimental results are studied to verify the effectiveness of the proposed method.

A stepless-power-reconfigurable converter for a constant current underwater observatory

The conversion from constant current(CC)to constant voltage(CV)is one of the key technologies of CC underwater observatory systems.A shunt regulator with high stability and high reliability is usually used.Applications,however,are limited by high heat dissipation and low efficiency.In this paper,with an improved shunt regulation method,a novel concept of stepless power reconfiguration(SPR)for the CC/CV module is proposed.In cases with stable or slowly changing load,two modes of CC/CV conversion are proposed to reduce unnecessary power loss of the shunt regulator while being able to retain any operatorpreset power margin in the system:(1)the manual SPR(MSPR)method based on single-loop control method;(2)the automatic SPR(ASPR)method based on inner-outer loop control method.The efficiency of the system is analyzed.How to select some key parameters of the system is discussed.Experimental results show that MSPR and ASPR are both effective and practical methods to reduce heat dissipation and improve the efficiency of the CC/CV module,while the high stability of the shunt regulator remains.

Constant frequency operation of parallel resonant converter for constant-current constant-voltage battery charger applications

This paper proposes a design and control approach to parallel resonant converter(PRC) based battery chargers.The proposed approach is particularly suitable for the constant-current constant-voltage(CC-CV)charging method, which is the most commonly utilized one.Since the PRC is operated at two different frequencies for each CC and CV charging modes, this approach eliminates the need for complicated control techniques such as the frequency-control and phase-shift-control.The proposed method not only simplifies the design and implementation processes of the converter unit but also simplifies the design of output filter configuration and decreases the number of the required components for the control of the charger.The proposed method is confirmed by two experimental setups.The results show that the designed charger circuit ensured a very stable constant current in CC charging phase, where the charging current is fixed to 1.75 A.Although a voltage increase in CV phase is observed, the charger circuit is able to decrease the charging current to 0.5 A in CV phase, as depicted in battery data-sheet.The efficiency of the charger is figured out to be in the range of 86%-93% in the first setup, while it is found to be in the range of 78%-88% in the second setup,where a high frequency transformer is employed.

高性能Rail-to-Rail恒定跨导CMOS运算放大器

基于UMC的0.6μm BCD 2P2M工艺,探讨了一种高性能Rail-to-Rail恒定跨导CMOS运算放大器.该运算放大器的输入级采用互补差分对,其尾电流由共模输入信号来控制,以此来保证输入级的总跨导在整个共模范围内保持恒定.输出级采用ClassAB类控制电路,并且将其嵌入到求和电路中,以此减少控制电路电流源引起的噪声和失调.为了优化运算放大器低频增益、频率补偿、功耗及谐波失真,求和电路采用了浮动电流源来偏置.该运算放大器采用米勒补偿实现了18MHz的带宽,低频增益约为110dB,Rail-to-Rail引起的跨导变化约为15%,功耗约为10mW.