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.

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.

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.

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.

Broadband on-chip integrator based on silicon photonic phase-shifted Bragg grating

All-optical integrators are key devices for the realization of ultra-fast passive photonic networks, and, despite their broad applicability range(e.g., photonic bit counting, optical memory units, analogue computing, etc.), their realization in an integrated form is still a challenge. In this work, an all-optical integrator based on a silicon photonic phase-shifted Bragg grating is proposed and experimentally demonstrated, which shows a wide operation bandwidth of 750 GHz and integration time window of 9 ps. The integral operation for single pulse, inphase pulses, and π-shifted pulses with different delays has been successfully achieved.

Utilizing phase-shifted long-period fiber grating to suppress spectral broadening of a high-power fiber MOPA laser system

Suppressing nonlinear effects in high-power fiber lasers based on fiber gratings has become a hotspot.At present,research is mainly focused on suppressing stimulated Raman scattering in a high-power fiber laser.However,the suppression of spectral broadening,caused by self-phase modulation or four-wave mixing,is still a challenging attribute to the close distance between the broadened laser and signal laser.If using a traditional fiber grating with only one stopband to suppress the spectral broadening,the signal power will be stripped simultaneously.Confronting this challenge,we propose a novel method based on phase-shifted long-period fiber grating(PS-LPFG)to suppress spectral broadening in a high-power fiber master oscillator power amplifier(MOPA)laser system in this paper.A PS-LPFG is designed and fabricated on 10/130 passive fiber utilizing a point-by-point scanning technique.The resonant wavelength of the fabricated PS-LPFG is 1080 nm,the full width at half maximum of the passband is 5.48 nm,and stopband extinction exceeds 90%.To evaluate the performance of the PS-LPFG,the grating is inserted into the seed of a kilowattlevel continuous-wave MOPA system.Experiment results show that the 30 dB linewidth of the output spectrum is narrowed by approximately 37.97%,providing an effective and flexible way for optimizing the output linewidth of highpower fiber MOPA laser systems.

Tunable frequency-multiplying optoelectronic oscillator based on a dual-parallel Mach-Zehnder modulator incorporating a phase-shifted fiber Bragg grating

A tunable frequency-multiplying optoelectronic oscillator(OEO) based on a dual-parallel Mach-Zehnder modulator(DPMZM) is proposed and experimentally demonstrated. In the proposed system, the tunable fundamental microware signal is generated by a tunable optoelectronic oscillator incorporating a phase-shifted fiber Bragg grating(PS-FBG). By adjusting the DC bias of the DPMZM, the frequency-doubled microwave signal with a tunable frequency range from 11 GHz to 20 GHz and the frequency-quadrupled microwave signal with a tunable frequency range from 22.5 GHz to 26 GHz are generated. The phase noises of the fundamental, frequency-doubled and frequency-quadrupled signals at 10 k Hz offset frequency are-105.9 d Bc/Hz,-103.3 d Bc/Hz and-86.2 d Bc/Hz, respectively.

A new phase-shifted long-period fiber grating for simultaneous measurement of torsion and temperature

A novel phase-shifted long-period fiber grating(PS-LPFG)for the simultaneous measurement of torsion and temperature is described and experimentally demonstrated.The PS-LPFG is fabricated by inserting a pretwisted structure into the long-period fiber grating(LPFG)written in single-mode fiber(SMF).Experimental results show that the torsion sensitivities of the two dips are?0.114 nm/(rad/m)and?0.069 nm/(rad/m)in the clockwise direction,and?0.087 nm/(rad/m)and?0.048 nm/(rad/m)in the counterclockwise direction,respectively.The temperature sensitivities of the two dips are 0.057 nm/℃ and 0.051 nm/℃,respectively.The two dips of the PS-LPFG exhibit different responses to torsion and temperature.Simultaneous measurement of torsion and temperature can be implemented using a sensor.The feasibility and stabilization of simultaneous torsion and temperature measurement have been confirmed,and hence this novel PS-LPFG demonstrates potential for fiber sensing and engineering applications.

Laser Trimming for Adjustment of Grating Offset in Phase-Shifted Fiber Grating Coupler for All-Optical Switching Application

We theoretically investigated laser trimming to adjust grating offset in phase-shifted fiber grating coupler (FGC) for all-optical switching application. It was clarified that the trimming made the extinction ratio higher in all-optical FGC switch.

Photonic-assisted FSK signal generation based on carrier phase-shifted double sideband modulation

An approach to generate high-speed and wideband frequency shift keying(FSK)signals based on carrier phase-shifted double sideband(CPS-DSB)modulation is proposed and experimentally validated.The core part of the scheme is a pair of cascaded polarization-sensitive LiNbO_(3) Mach–Zehnder modulators and phase modulators,whose polarization directions of the principal axes are mutually orthogonal to each other.A proof-of-concept experiment is carried out,where a 0.5 Gb/s FSK signal with the carrier frequencies of 4 and 8 GHz and a 1 Gb/s FSK signal with the carrier frequencies of 8 and 16 GHz are generated successfully.

Study on the Characters of Phase-Shifted Fiber Bragg Grating in Asymmetric Perturbation and Its Application in Fiber Laser Acoustic Sensor

A n-phase-shifted fiber Bragg grating theoretical model is established, and the effects of an asymmetric and symmetrical perturbation field on a phase-shifted fiber Bragg grating are investigated in this paper. The trends of wavelength shifting caused by effective refraction index of phase shift grating in symmetric and asymmetric acoustic field are investigated in detail. Then, the fiber laser acoustic sensors packaged in asymmetric and symmetrical structures are designed and tested, respectively. The results show that the acoustic response of the wavelength of the distributed feedback （DFB） fiber laser （FL） in an asymmetric packaging structure is much more sensitive than in that in the symmetrical structure. The sensor packaged in the asymmetrical structure has a better low frequency （0Hz-500Hz） performance and a higher sensitivity than that in the symmetrical structure, and the sensitivity is improved about 15dB in average and 32.7dB in maximum. It provides a new method to improve the sensitivity of the fiber acoustic sensor.

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.

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.

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.

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.

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.

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.

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.

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.