Search results

This paper aims to overcome the limitations of low efficiency, low power density and strong electromagnetic interference (EMI) of the existing pulsed melt inert gas (MIG) welding power supply. So a novel and simplified implementation of digital high-power pulsed MIG welding power supply with LLC resonant converter is proposed in this work.

A simple parallel full-bridge LLC resonant converter structure is used to design the digital power supply with high welding current, low arc voltage, high open-circuit voltage and a wide range of arc loads, by effectively exploiting the variable load and high-power applications of LLC resonant converter.

The efficiency of each converter can reach up to 92.3%, under the rated operating condition. Notably, with proposed scheme, a short-circuit current mutation of 300 A can stabilize at 60 A within 8 ms. Furthermore, the pulsed MIG welding test shows that a stable welding process with 280 A peak current can be realized and a well-formed weld bead can be obtained, thereby verifying the feasibility of LLC resonant converter for pulsed MIG welding power supply.

The high efficiency, high power density and weak EMI of LLC resonant converter are conducive to the further optimization of pulsed MIG welding power supply. Consequently, a high performance welding power supply is implemented by taking adequate advantages of LLC resonant converter, which can provide equipment support for exploring better pulsed MIG welding processes.

This study aims to regarding the application of traditional pulse frequency modulation control full-bridge LLC resonant converters in wide output voltage fields such as on-board chargers, there are issues with wide frequency adjustment ranges and low conversion efficiency.

To address these issues, this paper proposes a fixed-frequency pulse width modulation (PWM) control strategy for a full-bridge LLC resonant converter, which adjusts the gain by adjusting the duty cycle of the switches. In the full-bridge LLC converter, the two switches of the lower bridge arm are controlled by a fixed-frequency and fixed duty cycle, with their switching frequency equal to the resonant frequency, whereas the two switches of the upper bridge arm are controlled by a fixed-frequency PWM to adjust the output voltage. The operation modes of the converter are analyzed in detail, and a mathematical model of the converter is established. The gain characteristics of the converter under the fixed-frequency PWM control strategy are deeply analyzed, and the conditions for implementing zero-voltage switching (ZVS) soft switching in the converter are also analyzed in detail. The use of fixed-frequency PWM control simplifies the design of resonant parameters, and the fixed-frequency control is conducive to the design of magnetic components.

According to the fixed-frequency PWM control strategy proposed in this paper, the correctness of the control strategy is verified through simulation and the development and testing of a 500-W experimental prototype. Test results show that the primary side switches of the converter achieve ZVS and the secondary side rectifier diodes achieve zero-current switching, effectively reducing the switching losses of the converter. In addition, the control strategy reduces the reactive circulating current of the converter, and the peak efficiency of the experimental prototype can reach 95.2%.

The feasibility of the fixed-frequency PWM control strategy was verified through experiments, which has significant implications for improving the efficiency of the converter and simplifying the design of resonant parameters and magnetic components in wide output voltage fields such as on-board chargers.

This paper aims to present an 8 kW LLC resonant converter designed for plasma power supply with higher efficiency and lighter structure. It presents how to solve the problems of large volume and weight, low performance and low efficiency of traditional plasma power supply.

At present, conventional silicon (Si) power devices’ switching performance is close to the theoretical limit determined by its material properties; the next-generation silicon carbide (SiC) power devices with outstanding advantages can be used to optimal design. This 8 kW LLC resonant converter prototype with silicon carbide (SiC) power devices with a modulated switching frequency ranges from 100  to 400 kHz.

The experimental results show that the topology, switching loss, rectifier loss, transformer loss and drive circuit of the full-bridge LLC silicon carbide (SiC) plasma power supply can be optimized.

Due to the selected research object (plasma power supply), this study may have limited universality. The authors encourage the study of high frequency resonant converters for other applications such as argon arc welding.

This study provides a practical application for users to improve the quality of plasma welding.

The experimental results show that the full-bridge LLC silicon carbide (SiC) plasma power supply is preferred in operation under conditions of high frequency and high voltage. And its efficiency can reach 98%, making it lighter, more compact and more efficient than previous designs.

This paper aims to solve the problems of large hard switching loss and unclear resonant parameter design in the existing inverter power supply topology.

This paper proposes a simple and reliable two-stage isolated inverter composed of series quasi-resonant push-pull and external freewheeling diode full-bridge inverter. The power supply topology is analyzed, the topology mode is analyzed, the mathematical model of the converter is established and the DC gain of the converter is deduced. The relationship between the load and the output gain of the resonant tank is presented, a new resonant parameter design method is proposed, and the parameter design of the resonant element of the converter is clarified.

The resonant components of the converter are designed according to the proposed resonant parameter design method, and the correctness of the method is verified by simulation and the development and testing of a 500 W experimental prototype. After experimental tests, the peak efficiency of the experimental prototype can reach 94%. Because the experimental prototype achieves soft switching, the heat generation of the switch is greatly reduced, so the heavy heat sink is removed, and the volume is reduced by about 30% compared with the traditional power supply, and the total harmonic distortion of the output voltage is about 2%.

The feasibility of the scheme is verified by experiments, which is of great significance for improving the efficiency of the inverter power supply and parameter optimization.

This paper aims to better design the resonant tank parameters for LLC resonant converter. And, it is found that under heavy load, the voltage gain is affected by junction capacitors of the primary side switching and the parasitic parameters of the secondary side diodes converted to the primary side, which will cause the voltage gain decreased when the switching frequency decreased.

This paper proposes an optimization parameters design method to solve this problem, which was based on impedance model considering the parasitic parameters of switching devices and diodes.

The effectiveness of the proposed method is verified by impedance Bode plots and experimental results.

From the perspective of impedance modeling, this paper finds the reasons for the insufficient voltage regulation capability of LLC resonant converters under heavy load and finds solutions through analysis.

This study aims to solve the problem that under light-load conditions, the output voltage regulation capability is lost due to the fact that the voltage gain of the LLC resonant converter does not decrease with the increase of the switching frequency.

In this paper, the impedance model considering the parasitic parameters of the primary and secondary sides is calculated under light-load conditions, the limitations of the previous method are explained and a new circuit improvement is proposed.

In this paper, an improved circuit is proposed, and the impedance Bode plot is used to verify that the circuit can effectively improve the voltage gain problem under light-load conditions. Finally, the experimental results verify the effectiveness of the proposed circuit through comparison with traditional solutions and circuits.

In this paper, the impedance model considering the parasitic parameters of the primary and secondary sides is calculated, the limitations of the previous method are explained and a new circuit improvement is proposed. When compared with the previous method, the proposed circuit improvement can suppress the voltage gain increase that occurs when the switching frequency increases to a certain level.

The purpose of this paper is to study conducted electromagnetic interference (EMI) of the high-low voltage DC/DC converter based on GaN high-electron-mobility transistors (HEMTs) in electric vehicle, and design EMI filters to suppress the conducted EMI.

The conducted EMI propagation model is established through simulation and analysis studying the influences of parasitic parameters, operation mode, output power and near-field capacitive coupling effects on conducted EMI of the DC/DC converter and comparing the suppression effects of EMI filters with different topologies to select the best EMI filter.

It is shown that parasitic parameters, operation mode, output power and near-field capacitive coupling effects can affect the conducted EMI of the DC/DC converter, and EMI filters of the CLC topology can effectively suppress the conducted EMI below the limit of CISPR 25.

Analysis of conducted EMI and design of EMI filters greatly facilitate further explorations and studies on EMI problems of the high-low voltage DC/DC converter based on GaN HEMTs.

With the advancement of technology, size, cost, and losses of the switched mode power supply (SMPS) have been decreasing. However, due to the high frequency switching, design of magnetic drives and isolation circuits are becoming a crucial factor in SMPS. This paper presents design criteria, procedure and implementation of AC-DC half bridge (HB) converter with lower cost, smaller size and lower voltage stress on the power switch.

The HB converter is designed in a symmetrical mode with a series coupling capacitor. Isolated power supplies are used for the converter and control circuit. Further, a transformer based isolated gate driver is used to drive both MOSFETs. The control IC works in voltage control mode to regulate voltage by controlling the duty cycle of the MOSFETs.

Control characteristics and performance of the HB converter is simulated using the MATLAB software and prototype of 170 W HB converter is built to validate the analytical results under variable load current and source voltage. The power quality and variation of load voltage at 2 A, 5 A, 7 A are reported.

This paper presents the design of a low-cost HB converter in a symmetrical mode which saves the additional cost of symmetric correction circuit normally required in asymmetrical mode design. This paper also focuses on the selection of primary and secondary side switch, series coupling capacitor, commuting diode, isolated drive and charge equalizer resistor.

This paper aims to propose an integrated protection scheme for converters of a low-power, low-cost photovoltaic system. Power electronic converters use a variety of methods to limit overload and fault current. The use of insulated and non-insulated sensors along with additional circuits to detect and limit fault current can cause current to be limited or completely cut off before damage to semiconductor devices. In addition, fuses that have slower performance are used as backup for any type of protection.

First, all the candidate points for protection are investigated. In this paper, after examining the performance of glass fuses as linear resistors, they are used as a current feedback element. A simple, isolated and reliable circuit for fault detection at various points of the system has been proposed that can be implemented and operated in single shot or auto-reclose operating mode.

The experimental results of this circuit on a dc/dc converter and an H-bridge inverter show that it can cut off all instantaneous short circuit errors in less than 50 µs and prevent damage to the semiconductor switch.

In low-cost and low-power converters, it is usually not cost-effective to use complex and expensive devices. For this reason, these converters are more vulnerable to faults. On the other hand, in complex systems such as photovoltaics, several converters are used simultaneously in different parts, and the occurrence of a fault in each of them causes the whole system to fail.

This paper aims to review comprehensively the different voltage-boosting techniques and classifies according to their voltage gain, stress on the semiconductor devices, count of the total components and their prominent features. Hence, the focus is on non-isolated step-up converters. The converters categorized are analyzed according to their category with graphical representation.

Many converters have been reported in recent years in the literature to meet our power requirements from mill watts to megawatts. Fast growth in the generation of renewable energy in the past few years has promoted the selection of suitable converters that directly impact the behaviour of renewable energy systems. Step-up converters are a fast-emerging switching power converter in various power supply units. Researchers are more attracted to the derivation of novel topology with a high voltage gain, low voltage and current stress, high efficiency, low cost, etc.

A comparative study is done on critical metrics such as voltage gain, switch voltage stress and component count. Besides, the converters are also summarized based on their advantages and disadvantages. Furthermore, the areas that need to be explored in this field are identified and presented.

Types of analysis usually performed in dc converter and their needs with the areas need to be focused are not yet completely reviewed in most of the articles. This paper gives an eyesight on these topics. This paper will guide the researchers to derive and suggest a suitable topology for the chosen application. Moreover, it can be used as a handbook for studying the various topologies with their shortfalls, which will provide a way for researchers to focus.