Research on Phase-Shifted Full-Bridge Circuit Based on Frequency and Phase-Shift Synthesis Modulation Strategy

The full-bridge converters usually use transformer leakage inductance and parallel resonant capacitors to achieve smooth current commutation and soft switching functions,which can easily cause problems such as energy leakage and significant duty cycle loss.This paper designs a novel full-bridge zero-current(FB-ZCS)converter with series resonant capacitors and proposes a frequency and phase-shift synthesis modulation(FPSSM)control strategy based on this topology.Compared with the traditional parallel resonant capacitor circuit,the passive components used are significantly reduced,the structure is simple,and there is only a slight energy loss.By controlling the charging time of the capacitor,it can be achieved without additional switches or auxiliary circuits.The automatic control of capacitor energy based on input current addresses the low efficiency of the traditional control strategies.This paper introduces its principle in detail and verifies it through simulation.Finally,an experimental prototype was built further to demonstrate the feasibility of the theory through experiments.The module can be applied to a photovoltaic DC collection system using input parallel output series(IPOS)cascade to provide a new topology for large-scale,long-distance DC transmission.

Research on the Intelligent Control Strategy of the Fuel Cell Phase-Shifting Full-Bridge Power Electronics DC-DC Converter

focus of all countries.As an effective new energy,the fuel cell has attracted the attention of scholars.However,due to the particularity of proton exchange membrane fuel cell(PEMFC),the performance of traditional PI controlled phase-shifted full-bridge power electronics DC-DC converter cannot meet the needs of practical application.In order to further improve the dynamic performance of the converter,this paper first introduces several main topologies of the current mainstream front-end DC-DC converter,and analyzes their performance in the fuel cell system.Then,the operation process of the phase-shifted fullbridge power electronics DC-DC converter is introduced,and the shortcomings of the traditional PI control are analyzed.Finally,a double closed-loop adaptive fuzzy PI controller is proposed,which is characterized by dynamically adjusting PI parameters according to different working states to complete the intelligent control of phase-shifted full-bridge DC-DC converter.The simulation results in MATLAB/Simulink show that the proposed algorithm has good a control effect.Compared with the traditional algorithm,the overshoot and stabilization time of the system are shorter.The algorithm can effectively suppress the fluctuation of the output current of the fuel cell converter,and is a very practical control method.

Soft-switching PWM boost full-bridge converter

This paper proposes a family of PWM modulation strategies for boostfull-bridge (FB) converters. The modulation strategies can be classified into two kinds according tothe turn-on sequence of the diagonal switches. The concept of leading switches and lagging switchesis introduced to realize soft-switching. According to the soft-switching realized by the leadingswitches and the lagging switches, two kinds of soft-switching techniques for PWM boost FBconverters yield: zero-current-switching (ZCS) and zero-current and zero-voltage-switching (ZCZVS).Simulation results verify the analysis.

Design considerations for the improved current-doubler-rectifier ZVS PWM full-bridge converter

The improved current-doubler-rectifier zero-voltage-switching PWM full-bridge converter (CDR ZVS PWM FB converter) achieves ZVS for the switches in a wide load range with the use of the energy stored in the output filter inductances, and the rectifier diodes commute naturally, therefore no oscillation and voltage spike occurs. The transformer needs no special manufacture method to limit the leakage inductance. The ZVS achievement and the design considerations for the output filter inductances and the blocking capacitor are discussed for the improved CDR ZVS PWM FB converter. A 540 W prototype converter is built in the lab to verify the operational principle and design considerations for the improved converter, the experimental results are also included.

Application research on ZVZCS full-bridge converter technique

Based on ZVZCS （zero voltage zero current switching） full bridge converter technique, a novel inverter welding power supply is designed, in which the secondary side of the transformer adopts passive clamping circuit to reduce voltage stress of rectifying components. This supply can realize power switches ZVS （zero voltage switching ） or ZCS （zero current switching） within a very wide range of load; Only through setting up blocking capacitor in the primary side of transformer, the power transformer＇s bias in the full-bridge converter is suppressed and the primary current can be reset easily. In addition, how to calculate the blocking capacitor and its influence to power supply performance are also subjects discussed in this paper.

Analyzing the Location of the Transmission Windows in Phase-shifted Fiber Grating

Using the matrix approach,we analyzed the relation between the location of the transmission in stop band and the phase shift,and discussed the problem of varying the bandwidth of the transmission window.These theoretical results in this paper have important significance for actual application of the phase-shifted fiber grating.

SOFT SWITCHED SYNCHRONOUS RECTIFIER WITH PHASE-SHIFTED FULL BRIDGE CONVERTER AND ITS SMALL-SIGNAL ANALYSIS

By using the output inductors and body capacitances without adding any component compared with hard switching synchronous rectifier,the topology of a soft switched synchronous rectifier with phase-shifted full bridge zero voltage switching DC/DC converter is proposed. The converter efficiency is maximized due to soft switching of the full bridge MOSFETs and the synchronous MOSFETs, and also the low conduction loss of synchronous MOSFET. The operation principles of the circuit are analyzed in detail and the small-signal model is derived, also the converter dynamic characteristics are analyzed. Frequency responses of transfer functions under different values of transformer primary leakage inductance are discussed. The experimental results were obtained from a 400 V input and 100 A/12 V output DC/DC converter operating at 100 kHz. The results show that the converter efficiency is 2% higher in rated power than traditional diode rectifier.

The Implementation of a High Efficiency Full-Bridge Converter

A high efficiency full-bridge converter is investigated and implemented in this paper. The measured data result from the other converter implemented by IC UCC3895 is to compare with that of the previous converter. This full-bridge converter proposed and implemented converter can obtain about 96% power efficiency in conversion procedure when compared with that of 90%, which were ever published by the conventional techniques. Apart from, the L-C resonance circuits were developed and embedded into the popular PWM (pulse width modulation) power converter, which is referred as the soft-switching, so as to down sizing the volume of the IC which can totally reduces the power losses caused in the duration of a semi-con- ductor switching.

A New Phase-Shifted Cascade High Voltage Inverter

This paper presents a unique novel design of the phase-shifted cascade high voltage inverter. Thehigh voltage inverter utilizes fewer power switches and supplies a balance load. The usage of phase shifttransformer and phase shifting SPWM ensures that input and output harmonic wave content is low and outputvoltage change (du/dt) has a low rate, meeting all the requirements of the power authorities. The most out-standing feature is the energy saving with very fast cost recovery.

Adaptive Layout Partitioning for Dark Field Alternating Phase-Shift Mask Design

A new partitioning methodology is presented to accelerate 130nm and beyond large scale alternating phase shift mask(Alt PSM) design flow.This method deals with granularity self adaptively.Phase conflicts resolution approaches are described and strategies guaranteeing phase compatible during layout compaction are also discussed.An efficient CAD prototype for dark field Alt PSM based on these algorithms is implemented.The experimental results on several industry layouts show that the tool can successfully cope with the rapid growth of phase conflicts with good quality and satisfy lower resource consumption with different requirements of precision and speedup.

Phase-shift- and phase-fi ltering-based surfacewave suppression method

Aliased surface waves are caused by large-space sampling intervals in three- dimensional seismic exploration and most current surface-wave suppression methods fail to account for. Thus, we propose a surface-wave suppression method using phase-shift and phase-filtering, named the PSPF method, in which linear phase-shift is performed to solve the coupled problem of surface and reflected waves in the FKXKY domain and then used phase and FKXKY filtering to attenuate the surface-wave energy. Processing of model and field data suggest that the PSPF method can reduce the surface-wave energy while maintaining the low-frequency information of the reflected waves.

Nonlinear effect of the structured light profilometry in the phase-shifting method and error correction

Digital structured light （SL） profilometry is increasingly used in three-dimensional （3D） measurement technology. However, the nonlinearity of the off-the-shelf projectors and cameras seriously reduces the measurement accuracy. In this paper, first, we review the nonlinear effects of the projector-camera system in the phase-shifting structured light depth measurement method. We show that high order harmonic wave components lead to phase error in the phase-shifting method. Then a practical method based on frequency domain filtering is proposed for nonlinear error reduction. By using this method, the nonlinear calibration of the SL system is not required. Moreover, both the nonlinear effects of the projector and the camera can be effectively reduced. The simulations and experiments have verified our nonlinear correction method.

An encryption scheme based on phase-shifting digital holography and amplitude-phase disturbance

In this paper, we propose an encryption scheme based on phase-shifting digital interferometry. According to the original system framework, we add a random amplitude mask and replace the Fourier transform by the Fresnel transform. We develop a mathematical model and give a discrete formula based on the scheme, which makes it easy to implement the scheme in computer programming. The experimental results show that the improved system has a better performance in security than the original encryption method. Moreover, it demonstrates a good capability of anti-noise and anti-shear robustness.

DEFORMATION MEASUREMENT USING DUAL-FREQUENCY PROJECTION GRATING PHASE-SHIFT PROFILOMETRY

2π phase ambiguity problem is very important in phase measurement when a deformed object has a large out of plane displacement. The dual-frequency projection grating phaseshifting profilometry （PSP） can be used to solve such an issue. In the measurement, two properchosen frequency gratings are utilized to synthesize an equivalent wavelength grating which ensures the computed phase in a principal phase range. Thus, the error caused by the phase unwrapping process with the conventional phase reconstruct algorithm can be eliminated. Finally, experimental result of a specimen with large plastic deformation is given to prove that the proposed method is effective to handle the phase discontinuity.

Phase-shifting digital holography in image reconstruction

A phase-shifting digital holography scheme developed to investigate internal defects in artworks is described. Phase-shifting is utilized to obtain a clear reconstructed object wave from a rough surface texture. A reverse-transform algorithm is employed to reconstruct the object wave on its original position of unknown distance or the imaging position from the object wave information on the holographic plane. To get the clearest reconstruction the exact registration of the unknown distance is determined by applying the intensity sum as the auto-focusing function, The spatial resolution of the reconstruction image is also investigated for a variety of affecting factors. Laboratory results of reconstruction images under deformation are presented.

Multiple-image encryption by two-step phase-shifting interferometry and spatial multiplexing of smooth compressed signal

A multiple-image encryption method based on two-step phase-shifting interferometry （PSI） and spatial multiplexing of a smooth compressed signal is proposed. In the encoding and encryption process, with the help of four index matrices to store original pixel positions, all the pixels of four secret images are firstly reordered in an ascending order; then, the four reordered images are transformed by five-order Haar wavelet transform and performed sparseness operation. After Arnold transform and pixels sampling operation, one combined image can be grouped with the aid of compressive sensing （CS） and spatial multiplexing techniques. Finally, putting the combined image at the input plane of the PSI encryption scheme, only two interferograms ciphertexts can be obtained. During the decoding and decryption, utilizing all the secret key groups and index matrices keys, all the original secret images can be successfully decrypted by a wave-front retrieval algorithm of two-step PSI, spatial de-multiplexing, inverse Arnold transform, inverse discrete wavelet transform, and pixels reordering operation.

Optimization of the seismic processing phase-shift plus finite-difference migration operator based on a hybrid genetic and simulated annealing algorithm

Although the phase-shift seismic processing method has characteristics of high accuracy, good stability, high efficiency, and high-dip imaging, it is not able to adapt to strong lateral velocity variation. To overcome this defect, a finite-difference method in the frequency-space domain is introduced in the migration process, because it can adapt to strong lateral velocity variation and the coefficient is optimized by a hybrid genetic and simulated annealing algorithm. The two measures improve the precision of the approximation dispersion equation. Thus, the imaging effect is improved for areas of high-dip structure and strong lateral velocity variation. The migration imaging of a 2-D SEG/EAGE salt dome model proves that a better imaging effect in these areas is achieved by optimized phase-shift migration operator plus a finite-difference method based on a hybrid genetic and simulated annealing algorithm. The method proposed in this paper is better than conventional methods in imaging of areas of high-dip angle and strong lateral velocity variation.

Effect of phase-shift angle on 12-pulse star connection transformer system

Based on the study of the harmonic suppression on DC side of the multi-pulse rectification system,a software platform is established in Matlab environment.The phase-shift angle is studied from the aspects of system stability and economy,analyzing the effects of phase-shift angle on the input-side line current,the output-side voltage ripple,the equivalent capacity of autotransformer and other auxiliary devices in 12-pulse rectifier system.The software platform can complete the analysis only by inputting the initial conditions,eliminating the derivation of the intermediate formula and reducing the complexity of the system analysis,and have good scalability.The simulation results show that the system can effectively analyze the influence of phase angle on 12-pulse star-connected transformer.

Two-step phase-shifting Fresnel incoherent correlation holography based on discrete wavelet transform

Fresnel incoherent correlation holography(FINCH)has the ability to generate three-dimensional images with a superresolution by using incoherent sources.However,there are unwanted direct current term and twin image in interferograms,so it is of great significance to find a method to eliminate them.Phase-shifting technology is a most widely used technique for this task,but its three-step phase-shifting is not suitable for the instantaneous measurement of dynamic objects,and the quality of reconstructed image with the traditional two-step phase-shifting is lower.In this paper,we present a method of enhancing the resolution through using a two-step phase-shifting technology based on the discrete wavelet transform.After two-step phase-shifting,the resulting hologram is a superposition of multiple forms.The frequency of the resulting hologram is decomposed into different levels through using discrete wavelet transform,then the image is reconstructed after retrieving the low frequency band.Various experiments have verified the effectiveness of this method.

Semiconductor optical amplifier used as regenerator for degraded differential phase-shift keying signals

Phase and amplitude regeneration are necessary for degraded differential phase-shift keying communication sys- tems. This paper proposes a regenerator based on semiconductor optical amplifier for differential phase-shift keying signals. The key regeneration mechanism is theoretically analysed. The effectiveness of semiconductor optical amplifier based regenerator is demonstrated by comparing the bit error rate and eye diagrams before and after regeneration for 40-Cbit/s differential phase-shift keying 1080-km transmission systems. The results show that regeneration effects are very well. Bit error rate is tess than 10-12 with the regenerator.