Reducing the minimum output power of soft-switching inverter arc welding power supplies

The full-bridge zero-voltage and zero-current switching inverter, which can adjust the output power by keeping the duty-cycle of lagging arm constant, changing the duty-cycle of leading arm, is a common circuit topology of soft-switching inverter arc welding power supplies. However, the output power still remains a certain value when the duty-cycle of leading arm decreases to zero. The working-mode of soft-switching inverter and the waveforms of major parameters with the condition of duty-cycle of leading arm being zero are studied in this paper. U-1 characteristic experiments prove that the minimum output power of soft-switching circuit, which depends on the charged voltage of capacitors in parallel with leading arm, can be decreased by reducing the duty-cycle of lagging arm. By switching working-modes between half-bridge and full-bridge, the output power can swing from zero to the power rating.

LIMITATION OF SOFT-SWITCHING TECHNIQUE IN AC/DC POWER CONVERTER'S EFFICIENCY IMPROVEMENT

Soft-switching techniques are attractive to unity-power-factor AC/DC converter in the view of the size reduction and EMI suppression. A soft-switched boost PFC converter has been studied based on its topology analysis, PSIM simulation and circuit experiment. A special limitation of soft-switching techniques has been found in their AC/DC applications.

RESEARCH & DESIGN OF 60 kW SOFT-SWITCHING PLASMA CONVERTER

A novel 60 kW plasma converter with full range soft-switch by utilizing magnetizing inductance, leakage inductance and distributed inductance is introduced. The current injection phase-shifting technique is introduced into the research of soft-switching plasma converter successfully. The magnetic bias of transformer and the protection of switching parts are solved. The tests state that the power supply has excellent characteristics and higher efficiency and can meet the demand of large power plasma process well.

Soft-switching SiC power electronic conversion for distributed energy resources and storage applications

Power electronic conversion plays an important role in flexible AC or DC transmission and distribution systems,integration of renewable energy resources,and energy storage systems to enhance efficiency,controllability,stability,and reliability of the grid.The efficiency and reliability of power electronic conversion are critical to power system applications.One way to enhance the efficiency and reliability of power electronic conversion is soft-switching technology.This paper introduces a generic zero-voltage-switching(ZVS)technique based on silicon carbide(Si C)power device.Using the proposed ZVS technique,all semiconductor switching devices in a power converter can realize ZVS operations.Next,the applications of the ZVS technique in different power electronic conversion systems such as photovoltaic inverters,wind power systems,energy storage systems and flexible AC transmission system devices are discussed.Finally,as an example,the operation performance and efficiency improvement of a Si C metal-oxide-semiconductor field-effect transistor(MOSFET)ZVS back-to-back converter are discussed.

Multi-mode controller IC for soft-switched flyback converter with high efficiency over the entire load range

This paper presents a multi-mode control scheme for a soft-switched flyback converter to achieve high efficiency and excellent load regulation over the entire load range. At heavy load, critical conduction mode with valley switching (CCMVS) is employed to realize soft switching so as to reduce turn-on loss of power switch as well as conducted electromagnetic interference (EMI). At light load, the converter operates in discontinuous conduction mode (DCM) with valley switching and adaptive off-time control (AOT) to limit the switching frequency range and maintain load regulation. At extremely light load or in standby mode, burst mode operation is adopted to provide low power consumption through reducing both switching frequency and static power dissipation of the controller. The multi-mode control is implemented by an oscillator whose pulse duration is adjusted by output feedback. An accurate valley switching control circuit guarantees the minimum turn-on voltage drop of power switch. The pro-totype of the controller IC was fabricated in a 1.5-μm BiCMOS process and applied to a 310 V/20 V, 90 W flyback DC/DC converter circuitry. Experimental results showed that all expected functions were realized successfully. The flyback converter achieved a high efficiency of over 80% from full load down to 2.5 W, with the maximum reaching 88.8%, while the total power consumption in standby mode was about 300 mW.

Analysis of Soft-Switched High Frequency AC-AC Converter for Induction Motor Drive

The systematic mathematical analysis of the high frequency soft-switched AC-AC converter is proposed for variable frequency induction machine load in this paper. Both PWM and square-wave modes of operation have been considered. The frequency relation and phase unbalance problem due to discrete time integral half-cycle switching has been discussed in the beginning. Then, generalized Fourier series have been derived for output voltage, output current and supply current in two modes.The analytical results help to understand tbe converter characteristics, design optimally a convertermachine system of arbitrary capacity considering the various trade-off parameters.

Selection of Carrier Waveforms for PWM Inverter

In this paper the influence of different carrier waveforms upon the output characteristics of PWM inverter is described in detail. When a triangular carrier waveform is used in hard-switching PWM inverters, harmonics exist in the neighborhood of the output frequency of the inverter output voltage and current due to the dead time. The triangular carrier waveform used in soft-switching PWM inverter will cause difficulties in controlling resonance-trigger time, higher loss in the resonant circuit, and less utilization of the DC bus voltage. If a sawtooth carrier is used in hard-switching PWM inverter, there will be severe distortion in the current waveform. When sawtooth carriers with alternate positive and negative slopes are used in soft-switching PWM inverters, the resonance-trigger time is easy to control, and distortion in the output voltage and current caused by the dead time will not appear.

Zero-voltage switching converter absorbing parasitic parameters for super high frequency induction heating

This paper presents a novel mega-Hz-level super high frequency zero-voltage soft-switching converter for induction heating power supplies. The prominent advantage of this topology is that it can absorb both inductive and capacitive parasitic components in the converter. The switch devices operate in a zero-voltage soft-switching mode. Consequently, the high voltage and high current spikes caused by parasitic inductors or capacitors oscillation do not occur in this circuit, and the high power loss caused by high frequency switching can be greatly reduced. A large value inductor is adopted between the input capacitor and the switches, thus, this novel converter shares the benefits of both voltage-type and current-type circuits simultaneously, and there are no needs of dead time between two switches. The working principles in different modes are introduced. Results of simulation and experiments operated at around 1 MHz frequency verify the validity of parasitic components absorption and show that this convener is competent for super high frequency applications.

Intelligent Fuzzy Based High Gain Non-Isolated Converter for DC Micro-Grids

Renewable electricity options, such as fuel cells, solar photovoltaic,and batteries, are being integrated, which has made DC micro-grids famous.For DC micro-grid systems, a multi input interleaved non-isolated dc-dcconverter is suggested by the use of coupled inductor techniques. Since itcompensates for mismatches in photovoltaic devices and allows for separateand continuous power flow from these sources. The proposed converter hasthe benefits of high gain, a low ripple in the output voltage, minimal stressvoltage across the power semiconductor devices, a low ripple in inductorcurrent, high power density, and high efficiency. Soft-switching techniquesare used to realize that the reverse recovery issue of the diodes is moderated, the leakage energy is reused, and no new scheme is appropriated. Toreduce conduction losses, minimum voltage rating MOSFETs with a low ONresistance can be utilized. The converter can supply the required power fromthe load in the absence of one or two resources. Furthermore, due to the highgain of boosting voltage, the converter works in an Adaptive Neuro-FuzzyInference System (ANFIS). The operation principle, steady-state analysis ofthe proposed converter, is given and simulated utilizing MATLAB/Simulinksimulation software.

A digital controlled alternating electromagnetic stirring generator based on dual inverter structure

A digital controlled alternating electromagnetic stirring generator is proposed in this paper. The main circuit of the generator makes use of dual inverter structure among which the former inverter uses full bridge zero voltage switching topology and the latter inverter uses full bridge inverter circuit. To improve the dynamic response performance, the inverting frequency of the former inverter is as high us 100 kHz. The Cortex-M3 kernel based ARM microcontroller LM3S818 is adopted as the cybernetics core of the digital control system to achieve accurate, stable and flexible control of the generator. All the PWM signals for the former and latter inverters are generated by the LM3S818 directly. The constant current characteristic of the former inverter is obtained through current close-loop feedback control, and can ensure the operation safety when the output current waveform is at zero crossing point. Both simulation and experiment results show that the proposed generator is with such advantages as wide soft-switching range, perfect control accuracy and flexible waveform modulation, and can fulfill the requirements of electromagnetic stirring process.

Digital control system for pulsed MIG welding power based on STM32

Digital control system for pulsed MIG welding power based on STM32 is set up with 32-bit STM32FlO3ZET6 directing against the pulse waveform modulation of pulsed MIG welding. High-frequency inverter and medium-low frequency pulse waveform modulation of pulsed MIG welding are realized by using the integrated PWM module within STM32 to generate PWM signals of phase-shifted full-bridge soft-switching and constant-current control of output current is achieved by means of anti-windup PI control algorithm to improve the stability and reliability of control system. Experimental results demonstrate that the designed digital control system based on STM32 can achieve pegrect pulsed MIG welding technique with stable welding process and good weld appearance, fully demonstrating the advantages of digital control based on STM32.

Modeling and Analysis of Submerged Arc Weld Power Supply Based on Double Closed-Loop Control

According to the soft-switching pulsed SAW (Submerged arc weld) weld power supply based on the double closed-loop constant current control mode, a small signal mathematic model of main circuit of soft-switching SAW inverter was established by applying the method of three-terminal switching device modeling method, and the math-ematic model of double closed-loop phase-shift control system circuit was established by applying the method of state-space averaging method. Dynamic performance of the inverter was analyzed on base of the established math-ematic model, and the tested wave of dynamic performance was shown by experimentation. Research and experimentation show that relation between structure of the power source circuit and dynamic performance of the controlling system can be announced by the established mathematic model, which provides development of power supply and optimized design of controlling parameter with theoretical guidance.

Study of Multi-Function Micro-Plasma Spraying Technology

A multi-functional micro-arc plasma spraying system was developed according to aerodynamics and plasma spray theory. The soft switch IGBT （Insulated Gate Bipolar Transistor） invert technique, micro-computer control technique, convergent-divergent nozzle structure and axial powder feeding techniques have been adopted in the design of the micro-arc plasma spraying system. It is not only characterized by a small volume, a light weight, highly accurate control, high deposition efficiency and high reliability, but also has multi-functions in plasma spraying, welding and quenching. The experimental results showed that the system can produce a supersonic flame at a low power, spray Al2O3 particles at an average speed up to 430 m/s, and make nanostructured AT13 coatings with an average bonding strength of 42.7 MPa. Compared to conventional 9M plasma spraying with a higher power, the coatings with almost the same properties as those by conventional plasma spray can be deposited by multi-functional micro-arc plasma spraying with a lower power plasma arc due to an improved power supply design, spray gun structure and powder feeding method. Moreover, this system is suitable for working with thin parts and undertaking on site repairs, and as a result, the application of plasma spraying will be greatly extended.

A zero-voltage zero-current soft switching DC/DC converter

A novel three-level zero-voltage zero-current switching(ZVZCS)DC/DC converter is proposed in this paper.A tapped-inductor is used to replace the normal out-put filter inductor,so that the circulating current in the zero-state can be reset to zero.The reset voltage and the re-set time can be set conveniently just by simply changing the winding ratio of the tapped inductor.The converter achieves a zero-current tuning off for inner switching,and a zero-voltage tuning on for outer switching.No circulating current exists in the zero state,so that the loss in the on-state is reduced,and the efficiency can be improved.The experimental results verify that the ZVZCS has low voltage stress,zero-voltage and zero-current switching.