Forward-flyback Converter Research Articles

Synchronous rectification for two-transformer active-clamp forward-flyback converters to remove voltage spikes on secondary-side field-effect transistors

Synchronous rectification for two-transformer active-clamp forward-flyback converters to remove voltage spikes on secondary-side field-effect transistors

Reverse power transmission of two-transformer active clamp forward flyback converter

Reverse power transmission of two-transformer active clamp forward flyback converter

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

Abstract The performance of photovoltaic 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 photovoltaic modules by analyzing the influence of irradiance and temperature. A simulation model is developed using PLECS software to simulate the global maximum power of photovoltaic modules under different environmental conditions, and the results are compared with the calculated real maximum power. A power optimization scheme for photovoltaic 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 photovoltaic 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 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 traditional perturb and observe algorithm. The proposed scheme achieves a significant improvement in efficiency, with a 27.87% increase compared to the segment perturb and observe algorithm without current equalization.

Power equalization and optimization of photovoltaic module based on forward-flyback converter

This paper focuses on enhancing the energy extraction efficiency of photovoltaic (PV) modules through the use of a straightforward power converter and control algorithm. This research delves into the electrical characteristics of PV modules, explaining the concepts of global maximum power point, and local maximum power points. By integrating maximum power point tracking algorithms and differential power processing technology, an innovative scheme for power equalization and optimization of PV modules is introduced. The scheme is based on a single-switch multi-winding forward-flyback converter. Using the STP-340-72-Vfh-type PV module as a case study, a simulation model is developed with PLECS simulation software. The simulations cover 30 different irradiance scenarios. The findings illustrate the effectiveness of the proposed PV module power optimization system in achieving maximum power output under different irradiance conditions, achieving an average efficiency of 94.61%. This efficiency rate is 13.95% greater than that of existing global maximum power tracking schemes.

Dynamic Analysis of the Forward-Flyback Converter Considering the ESR of the Output Capacitor and Comparing it with the Flyback Converter

Dynamic Analysis of the Forward-Flyback Converter Considering the ESR of the Output Capacitor and Comparing it with the Flyback Converter

Power Optimization of Multi-Type Mixed-Connection Photovoltaic Generation System for Recreational Vehicles

The utilization of photovoltaic (PV) generation to charge storage batteries in recreational vehicles (RVs) is becoming increasingly prevalent. However, the performance of PV generation systems is hindered by the mismatch caused by different module types and varying environmental conditions. This discrepancy negatively impacts the output performance of PV modules, resulting in reduced system efficiency. To address this issue, this paper explored the series–parallel output characteristics of different types of PV modules and summarized the methods for configuring PV modules in a mixed-structure PV generation system for RV energy supplementation. Building upon this foundation, a novel equalization scheme based on extremum-seeking control (ESC) is introduced. The scheme initially employs a forward–flyback converter (FFC) to equalize the current among series-connected PV modules, followed by matching the voltage between parallel-connected PV module strings. Finally, the ESC is utilized to optimize the real-time output power of the PV generation system, thereby enhancing overall system efficiency. Through simulation experiments conducted on a PV generation system with four types of mixed-connection PV modules employing the PLECS simulation platform, simulated results demonstrate the effectiveness of the proposed scheme in improving PV module output performance and maximum power tracking efficiency. The simulation data reveal that the proposed scheme achieves an impressive average tracking efficiency of 99.15%, surpassing the efficiency of the global maximum power point tracking scheme based on an enhanced perturb and observe algorithm.

A High-Power-Density Active-Clamp Converter with Integrated Planar Transformer

This paper proposes an active-clamp forward-flyback (ACFF) converter with an integrated planar transformer for wide-input voltage and high-output current applications, such as low-voltage direct-current (LDC) converters in electric vehicles. An integrated planar transformer that consists of a forward-flyback transformer, single primary winding, and efficient structure of secondary windings is adopted for the proposed converter, and since this transformer is implemented with a common four-layer printed circuit board (PCB) winding, a high power density and low cost of the proposed converter can be achieved. In addition, due to the low leakage inductance induced by the planar transformer, a reduced commutation period can be achieved, and it is possible to increase the switching frequency resulting in low volume of transformer. Although the integrated planar transformer has relatively high conduction loss, the active-clamp topology can significantly reduce the conduction loss on switches compared with widely used full-bridge (FB) converters because it only utilizes two switches and shows the low circulating current. As a result, the proposed converter with an integrated planar transformer has strengths in high power density and cost competitiveness without degraded efficiency, and it is a very attractive topology for LDC converters and other applications that require wide-input voltage and high-output current.

Forward–Flyback Converter With Cockcroft–Walton Voltage Multiplier in DCM: Steady-State Analysis Considering the Parasitic Capacitances to Achieve the Optimal Valley-Switching Operation With 95.11% Efficiency at 3 kV/1.5 W

Nowadays, electrohydrodynamic (EHD) cooling systems are considered a good alternative to rotary fans and heatsinks from industrial electronic applications due to their robustness, high performance, and low weight. The EHD load tested along this article demands high voltage (3 kV) and very low current (500 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{A}$ </tex-math></inline-formula> ) to produce the corona discharge and the airflow. The forward–flyback converter with Cockcroft–Walton voltage multiplier (FFCWVM) is proposed in this article as a suitable topology to supply EHD loads. The parasitic capacitances are considered throughout the steady-state analysis, leading to new operating stages and allowing for a very accurate mathematical modeling of the main resonant intervals. Consequently, the impact of a slow voltage transition in the functioning of the circuit is analyzed and the optimal valley-switching operation is calculated analytically. Finally, the theoretical analysis is validated by means of simulations and experimental results, achieving a very high efficiency (95.11%) for such low output power (1.5 W).

Design of a High Efficiency High Step-Up/Step-Down Bidirectional Isolated DC–DC Converter

This paper presents a novel bidirectional DC–DC converter, equipped with a three-winding coupled inductor, that can be applied to high-voltage, bidirectional DC–DC energy conversion and meet battery charging and discharging requirements. The architecture consists of a semi-Z-source converter and a forward–flyback converter featuring a three-winding coupled inductor with an iron core. This proposed topology retains the current continuity characteristics of the low-voltage side, all switches possess the zero-voltage switching feature, and the switches on the low-voltage side in the step-down mode have a synchronous rectification function. A 500-W bidirectional converter is implemented to examine the practicality and feasibility of the proposed topology. The relatively streamlined design of the converter can greatly reduce production costs. In the step-up and step-down modes, the maximum energy conversion efficiencies are 95.74% and 96.13%, respectively.

Integrated boost‐forward‐flyback converter with high step‐up for green energy power‐conversion applications

An isolated high step-up converter is proposed for renewable energy sources with low voltages, such as photovoltaic (PV) cells of solar energy and fuel cells of hydrogen energy, to achieve high voltage levels for series-connection batteries and DC-bus voltage sources. The proposed integrated boost-forward-flyback converter (IBFFC) is achieved by integrating a boost converter, a forward-flyback converter and a voltage doubler. Moreover, an active-clamp function is employed to recycle the energy of leakage inductance. An 800 W-rated prototype has been implemented to verify the functionality of the presented converter; it offers an input voltage of 48 V and an output voltage of 400 V. In addition, the maximum efficiency is approximately 94%.

A Novel Bidirectional Isolated DC-DC Converter With High Voltage Gain and Wide Input Voltage

This article proposes a novel bidirectional isolated dc-dc converter with high voltage gain and wide input voltage, which can be applied to bidirectional power conversion systems. The proposed topology is composed of a bidirectional buck-boost converter and a forward-flyback converter; it has the advantage of higher voltage gain and has continuous current characteristic of the low-side port in step-up and step-down mode. In addition, the proposed topology also has the function of leakage inductance energy recovery, which can improve the efficiency of the converter, reduce the voltage surges on switches, and have the characteristics of zero voltage switching on certain switches. Finally, this paper implements a 500-W bidirectional dc-dc converter to verify the feasibility of the proposed topology. The low-side voltage of the proposed topology is 24, 48, and 55 V; the maximum efficiency in step-up mode are 94.2%, 95.6% and 96.9%, and the maximum efficiency are 92.6%, 94.2% and 94.5% in the step-down mode, respectively.

A New Single-Switch ZCS Flyback-Forward Converter with High Power Density

In this paper, a new zero current switching flyback-forward DC-DC converter is proposed. In the proposed converter to provide soft switching condition, an auxiliary circuit without any additional switch is used, which increases the efficiency. In this converter the switch is gated with PWM signal; therefore, the design and implementation of the control circuit is simple. The other advantages of the proposed converter are elimination of the core reset circuit and power transfer to the output in turn on and turn off switch that cause to increase power density. The experimental results verified the theoretical analysis and the efficiency of the proposed converter in full load is about 93%.

Full-Bridge Active-Clamp Forward-Flyback Converter with an Integrated Transformer for High-Performance and Low Cost Low-Voltage DC Converter of Vehicle Applications

This paper presents a full-bridge active-clamp forward-flyback (FBACFF) converter with an integrated transformer sharing a single primary winding. Compared to the conventional active-clamp-forward (ACF) converter, the proposed converter has low voltage stress on the primary switches due to its full-bridge active-clamp structure, which can leverage high performance Silicon- metal–oxide–semiconductor field-effect transistor (Si-MOSFET) of low voltage rating and low channel resistance. Integrating forward and flyback operations allows the proposed converter to have much lower primary root mean square (RMS) current than the conventional phase-shifted-full-bridge (PSFB) converter, while covering wide input/output voltage range with duty ratio over 0.5. The proposed integrated transformer reduces the transformer conduction loss and simplify the secondary structure of the proposed converter. As a result, the proposed converter has several advantages: (1) high heavy load efficiency, (2) wide input voltage range operation, (3) high power density with the integrated transformer, and (4) low cost. The proposed converter is a very promising candidate for applications with wide input voltage range and high power, such as the low-voltage DC (LDC) converter for eco-friendly vehicles.

Analysis and implementation of the Autotransformer Forward-Flyback converter applied to photovoltaic systems

The Distributed Maximum Power Point Tracking (DMPPT) architecture is employed to overcome the mismatching phenomena in grid-tied photovoltaic (PV) installations. In this kind of architecture, a DC-DC module integrated converter (MIC) manages each PV panel. Thanks to the DC-DC converters, the differences between PV panels do not influence others, maximizing the amount of harvested power. The MIC requirements to make this kind of solutions profitable are voltage step-down and step-up capability, low cost and high efficiency. This paper analyses the Autotransformer Forward-Flyback (AFF) converter. This converter is considered as a MIC candidate for fulfilling the requirements above. The study of the AFF converter includes the steady-state analysis and the small signal analysis in continuous conduction mode. The advantages of the AFF converter are the capability of voltage step-down and step-up; the simplicity since it only includes a single controlled switch; the use of an autotransformer; good dynamic performances and the soft switching characteristics in all the diodes. The paper includes a detailed AFF converter step-by-step design procedure, applied to 100 kW grid-tied PV installation, in which the effect of shadows has been considered. A 225 W AFF converter prototype validates the theoretical analyses, achieving an efficiency up to 94.5%.

Research on the PFC Mechanism of Forward-Flyback Converter

The forward-flyback converter is used in power factor correction to improve the performance of conventional forward PFC and flyback PFC converters. By analyzing the working principle of a single-transistor single-transformer forward-backward combined PFC converter in one power frequency cycle, it is pointed out that there are two working modes — flyback mode and forward flyback mode; through its PFC mechanism research. The relationship between the duty cycle of each operating mode when achieving unity power factor is obtained, and the duty cycle when operating in flyback mode is the maximum duty cycle within a power frequency cycle. Finally, the open-loop control model of the forward-flyback PFC converter is established by using MATLAB. The duty cycle is changed according to the specified rules and the PFC is implemented, which verifies the correctness of the theoretical analysis.

Design, modelling, and implementation of a modified double‐switch flyback‐forward converter for low power applications

This study proposes a modified double-switch flyback-forward (DSFF) converter for low-power applications with a reduced number of windings in its transformer. This circuit has resulted from the combination of the two-switch flyback and two-switch forward converters. It includes a simple transformer with one set of secondary side windings, and it is not necessary to design two separate sets of windings for the desired output voltage which is the main problem of other flyback-forward converters. An auxiliary winding has been designed for self-biasing, and consequently, it improves the overall efficiency in the no-load condition. Due to the modifications on the previously presented two-switch flyback-forward converter, the circuit model has changed. This study, first, analyses the operation of the proposed converter in detail, then it explains a method to design this converter in continuous inductor current mode. Also, a start-up voltage regulator circuit and a modified bootstrap gate driver will be investigated, and the DC and AC model of the converter will be presented. Experimental results validate the proposed DSFF converter. The tested circuit includes a DSFF converter, a pulse generator circuit, a start-up voltage regulator, and a modified bootstrap gate driver.

A Scheme of a Resonant Forward-Flyback Converter With Suppressed Frequency Variation

This letter proposes a simple and low-cost scheme to soft switch an isolated converter. The new circuit merges resonant forward converters and flyback converters by using shared power transformers and primary switches. Specifically, the resonant forward mode operation fulfills soft-switching for the primary switches, and the flyback mode operation resets the transformers by directly delivering the energy to the output. This also allows us a lower ratio between the leakage inductance and the magnetizing inductance. Thus, the main attraction is that simpler structure is utilized to regulate the output voltage for a resonant converter with a constant switching frequency, and higher power efficiency is achievable by taking the full use of transformer magnetizing energy. Also, an input-series-output-parallel connection is utilized to further reduce the voltage stress on the primary side. In addition to detailed theoretical analysis, experimental results verify the feasibility and effectiveness of the proposed concept.

An Electrolytic Capacitor-Less High Power Factor LED Driver Based on a “One-and-a-Half Stage” Forward-Flyback Topology

A “one-and-a-half stage” forward-flyback converter for electrolytic capacitor-less light-emitting diode (LED) driver with high power factor (PF), high efficiency, low output ripple current, and long lifetime has been proposed and studied in this paper. The basic topology of the proposed topology is a single-switch forward-flyback converter for achieving high PF. In addition, a buck converter is inserted between the forward subconverter and the load for creating two paralleled power transfer paths. The most of input energy directly reaches the load through flyback subconverter, and only about 1/4 of total energy is transferred to the load through forward subconverter and buck converter. Therefore, the proposed topology is a “one-and-a-half stage” converter and can achieve higher efficiency than the traditional two-stage topologies. At the same time, power decoupling can be realized and the electrolytic capacitor can be eliminated. Optimal control scheme, detailed analysis, and design considerations for this improved converter are presented. Finally, an experimental prototype for 28 V/700 mA LED driver was built up to verify the theoretical analysis.

Study and Analysis of Flyback with Adding RC and CatchWinding Forward DC-DC Power Converter in CCM and DCM

The isolated DC-DC converters are completely separated between the input and the output terminals. However, the non-isolated DC-DC converters would share a common ground between the input and the output terminals. The isolated DC-DC converters can be used as a positive grounding or negative grounding. Furthermore, isolated converters have found wide application recently due to their advantage over non-isolated converters. In addition, electrical isolation of input and output ground connections is for safety. The voltage and current stress on switches can be minimized using transformers. Moreover, the first winding can be used to put in energy into the inductor; as a result, the inductor that could gradually increase the energy from the inductor to the load cannot be available for the other coil. The two significant topologies of the isolated DC-DC converters are flyback converter and catch-winding forward converter. Therefore, the main goal is to analyze and investigate the impact of change in switching frequency, duty ratio, load and the input voltage for every topology and to find the critical points for every topology by comparing the results with every figure done through this work [1].

An Asymmetric Half Bridge Forward-Flyback Hybrid DC/DC Converter

基于已有的有源钳位正反激DC/DC变换器，本文提出了一种新颖的不对称半桥正反激DC/DC变换器。将不对称半桥结构应用到有源嵌位正反激DC/DC变换器，继承了有源嵌位正反激DC/DC变换器高效率、高功率密度的特点，并将开关管电压应力大大减小。文章详细论述了该变换器的工作原理，给出了关键时序波形，并着重分析了稳态下的基本数量关系和软开关实现条件。在理论分析的基础上，使用saber进行仿真分析并制作了80 W实验样机，验证了该变换器理论分析的正确性。 Based on the existed active clamp forward-flyback hybrid DC/DC, a new asymmetric half bridge forward-flyback hybrid DC/DC converter is proposed in the paper. The asymmetrical half bridge structure is applied to active clamp forward-flyback converter, which inherits the characteristics of the active clamp forward-flyback converter with high efficiency and high power density, and the voltage stress of the switch is greatly reduced. In this paper, the operating principle of the converter is discussed in detail; the key time sequence is given; and realization conditions of soft switching and basic quantitative relationship in steady state are analyzed emphatically. Based on the theoretical analysis, saber is used to do simulation analysis and make an 80 W experimental prototype to validate the validity of theoretical analysis.