Showing papers on "Flyback transformer published in 2022"

New Modulation and Impact of Transformer Leakage Inductance on Current-Source Solid-State Transformer

Abstract: This article presents a novel modulation scheme for device voltage stress mitigation and comprehensive analysis of the impact of transformer leakage inductance in a current-source solid-state transformer (SST). Different from dual active bridge (DAB) SST, the operation of the current-source SST is similar to that of a flyback converter. The device bridge on only one side of the transformer is active to store energy into or release energy from the magnetizing inductance which acts as a current-source dc-link. Such flyback operations with reverse-blocking switches can lead to additional device voltage stress and incomplete zero-voltage switching (ZVS) on the current-source soft-switching solid-state transformer (S4T) under conventional modulation. A new modulation scheme is proposed to address this issue. Moreover, different from the DAB, the leakage inductance of the medium-frequency transformer (MFT) in the S4T is a parasitic element similar to that in a matrix SST and can cause additional device voltage stress. Though the resonant capacitors, originally added to achieve ZVS, can absorb and recycle the leakage energy in the S4T, these capacitors need to be increased with larger leakage inductances to limit the voltage stress. However, large resonant capacitors can result in more lost duty cycles and reduced efficiency. The impact of such leakage inductance on device voltage stress is analyzed comprehensively, which is critical to guide future research and design of the S4T. Experimental results from S4T prototypes for dc–dc, multiport ac–dc, and ac–ac conversion with 1:1 and 4:1 MFT comprehensively verify the proposed concepts. Finally, a case study of a three-phase ac–ac S4T over a power range from 1 to 100 kVA each module reveals that the MFT leakage inductance should be less than 1% of the magnetizing inductance for safe operation.

PV Microinverter Solution for High Voltage Gain and Soft Switching

Abstract: This article proposes a high-gain flyback-type microinverter for photovoltaic (PV) power generation. The proposed topology integrates a voltage-doubler circuit with the flyback converter to produce the high voltage conversion gain. The solution is effective to minimize the high demand of the winding turns ratio in the flyback transformer. Besides, an active-clamp circuit is employed in the primary side for the resonant operation. The solution reduces the voltage and current stress and supports zero voltage switching of the power switching. The stress reduction achieved by the resonant operation further minimizes the conduction loss of the converter. A prototype is constructed and tested to show the experimental performance, which verified the advantages of the proposed solution for PV microinverter applications.

New Modulation and Impact of Transformer Leakage Inductance on Current-Source Solid-State Transformer

Abstract: This article presents a novel modulation scheme for device voltage stress mitigation and comprehensive analysis of the impact of transformer leakage inductance in a current-source solid-state transformer (SST). Different from dual active bridge (DAB) SST, the operation of the current-source SST is similar to that of a flyback converter. The device bridge on only one side of the transformer is active to store energy into or release energy from the magnetizing inductance which acts as a current-source dc-link. Such flyback operations with reverse-blocking switches can lead to additional device voltage stress and incomplete zero-voltage switching (ZVS) on the current-source soft-switching solid-state transformer (S4T) under conventional modulation. A new modulation scheme is proposed to address this issue. Moreover, different from the DAB, the leakage inductance of the medium-frequency transformer (MFT) in the S4T is a parasitic element similar to that in a matrix SST and can cause additional device voltage stress. Though the resonant capacitors, originally added to achieve ZVS, can absorb and recycle the leakage energy in the S4T, these capacitors need to be increased with larger leakage inductances to limit the voltage stress. However, large resonant capacitors can result in more lost duty cycles and reduced efficiency. The impact of such leakage inductance on device voltage stress is analyzed comprehensively, which is critical to guide future research and design of the S4T. Experimental results from S4T prototypes for dc–dc, multiport ac–dc, and ac–ac conversion with 1:1 and 4:1 MFT comprehensively verify the proposed concepts. Finally, a case study of a three-phase ac–ac S4T over a power range from 1 to 100 kVA each module reveals that the MFT leakage inductance should be less than 1% of the magnetizing inductance for safe operation.

A Novel Synchronized Multiple Output DC-DC Converter Based on Hybrid Flyback-Cuk Topologies

Abstract: This paper proposes a new hybrid flyback-Cuk (HFC) converter. The new converter consists of a single switch, a single isolated input, and dual output based on flyback and Cuk topologies. The new HFC topology is proposed to reduce switching losses and improve the duty cycle range over which voltage can be stepped down, which would ultimately lead to an increase in efficiency. For step-down capability, the traditional single topologies (flyback or Cuk) require a less than 50% duty cycle. The low duty cycle of conventional converters leads to low operational efficiency. Therefore, the developed HFC can operate at a duty cycle of up to 85% for the same capability. The analysis, derivations, design, and simulation of the proposed HFC are thoroughly discussed for two different applications at two different power levels. The simulation results are obtained using MATLAB 2020a. The developed HFC’s efficiency as a function of the duty cycle is plotted, which reaches 89%, representing a significant efficiency improvement. The proposed converter can supply and absorb power simultaneously, giving it a significant edge over other converters. It is suitable for energy conversion and storage systems, such as renewable energy systems and electric vehicles (EV). To show the effectiveness and validate the new topology proposed, an EV along with battery energy storage (BES), is applied to charge (EV) and recharge (BES) simultaneously. The simulation results of 1.5 kW of HFC-PFC over the universal voltage range show that the proposed HFC can achieve a high power factor up to 97.5% at 260 Vrms. Moreover, the total harmonics distortion is measured between 36.25 and 27.69%. Thus, the results can achieve all required functions efficiently with minimum losses at a high range of duty cycles.

A Modulation Method for Capacitance Reduction in Active-Clamp Flyback-Based AC–DC Adapters

Abstract: Recent developments of fast-charging power delivery protocols are driving ac–dc adapters to 100-W power ranges. Conventional solutions in this power range employing a two-stage topology and a big twice-line frequency buffer capacitor are generally costly and bulky. This article presents a patent-pending modulation method for an active-clamp flyback converter, allowing for a single-stage adapter design with reduced capacitance requirements and higher efficiency. This is achieved by exploiting the inherent energy storage capability of the clamping capacitor while turning it into an active power buffer. No hardware modifications are needed, while all salient features of active-clamp flyback converter, i.e., soft switching and leakage recycling, are retained. Operating principles and detailed controller design are discussed, and a 100-W laboratory prototype is built. The prototype achieves 94% peak efficiency and up to 92% size reduction of the buffer capacitor. The experimental evaluation shows that the new single-stage solution enabled by the proposed modulation method is superior to the conventional two-stage and single-stage solutions in terms of cost, conversion efficiency, and power density.

Modular Single-Stage Three-Phase Flyback Differential Inverter for Medium/High-Power Grid Integrated Applications

Abstract: This paper proposes a single-stage three-phase modular flyback differential inverter (MFBDI) for medium/high power solar PV grid-integrated applications. The proposed inverter structure consists of parallel modules of flyback DC-DC converters based on the required power level. The MFBDI offers many features for renewable energy applications, such as reduced components, single-stage power processing, high-power density, voltage-boosting property, improved footprint, flexibility with modular extension capability, and galvanic isolation. The proposed inverter has been modelled, designed, and scaled up to the required application rating. A new mathematical model of the proposed MFBDI is presented and analyzed with a time-varying duty-cycle, wide-range of frequency variation, and power balancing in order to display its grid current harmonic orders for grid-tied applications. In addition, an LPF-based harmonic compensation strategy is used for second-order harmonic component (SOHC) compensation. With the help of the compensation technique, the grid current THD is reduced from 36% to 4.6% by diminishing the SOHC from 51% to 0.8%. Moreover, the SOHC compensation technique eliminates third-order harmonic components from the DC input current. In addition, a 15% parameters mismatch has been applied between the flyback parallel modules to confirm the modular operation of the proposed MFBDI under modules divergence. In addition, SiC MOSFETs are used for inverter switches implementation, which decrease the inverter switching losses at high-switching frequency. The proposed MFBDI is verified by using three flyback parallel modules/phase using PSIM/Simulink software, with a rating of 5 kW, 200 V, and 50 kHz switching frequency, as well as experimental environments.

A New Technique for Improvement Differential Relay Performance in Power Transformers

Abstract: Transformer protection devices are often used to identify internal or external transformer problems and act to either prevent damage or unnecessarily disconnect power transformers. This study proposes a new differential element that combines harmonic restraint, security, and reliability with harmonic blocking speed to improve the relay performance in a power transformer. Under high load, a negative-sequence differential element adds more sensitivity for internal turn-to-turn failures. External fault detection monitoring enhances security in an external problem involving current transformer (CT) saturation. Furthermore, overcurrent elements may be configured to vary dynamically in operation is provided. This element enhances protection coordination for various operating conditions without requiring modifications to the transformer group settings. The balance of the paper discusses the use of an under-load tap changer using a time-synchronized phasor monitoring system to reduce loop current and losses in parallel transformer applications.

Revisiting the Partial Power Processing Concept: Case Study of a 5-kW 99.11% Efficient Flyback Converter-Based Battery Charger

Abstract: This article proposes an analytical methodology to evaluate the performance of the main partial power processing (PPP) architectures in terms of the improvements in the system’s conversion efficiency. This analysis considers the influence of the system’s voltage gain, the auxiliary dc/dc converter’s efficiency, and the possibility of bidirectional power flow. Herein, the key PPP architectures are, thus, modeled and benchmarked. The presented results attest to the series configuration as the most efficient PPP circuit solution, with no limits on the system voltage gain, contrary to the generalized results found in today’s literature. To assess these results and the significance of the proposed analysis, a well-known, simple, and cost-effective flyback topology has been designed and tested for a series PPP circuit solution able to effectively interface a 5-kW battery energy storage system (BESS) to a 700-V dc grid. A relatively high power conversion efficiency and compact hardware are achieved due to the reduced size requirements on the input and output filtering stages. Above all, while explaining the PPP concept, this study shows that even converter circuits known for their low power efficiency can be used to derive highly efficient systems. A design approach is, thus, provided to facilitate the design of the presented PPP circuit, and measurements are, finally, carried out to compare the obtained results with the expected ones derived from the developed analytical models.

Sliding-Mode Control of a Photovoltaic System Based on a Flyback Converter for Microinverter Applications

Abstract: A method to design a sliding-mode control of a photovoltaic system based on a flyback converter is proposed. First, the photovoltaic system is modeled to design the sliding-mode controller and to select the parameters of a maximum power point tracking algorithm. Then, the detailed design of the sliding-mode controller is presented, which includes the establishment of the sliding surface. The transversality, reachability, and equivalent control tests are also developed. Because the power extraction of the PV system is carried out through a P&O MPPT algorithm, the selection of the perturbation magnitude, the perturbation period, and the maximum switching frequency is integrated into the control design. Additionally, since the derivative of the MPPT output could prevent the achievement of the reachability test, a filter to limit that derivative is also integrated into the design process. The whole method is illustrated in an application example where the data of a BP585 PV module and a real flyback converter are used. Once the parameters were obtained, circuital simulations performed in PSIM validated the intended operation of a PV system composed of a PV module and a flyback converter, which is connected to a source that produces the perturbations of an AC grid.

High Power Factor Bridgeless Integrated Buck-Type PFC Converter With Wide Output Voltage Range

Abstract: Due to the input current dead zones, the buck power factor correction converter has to set a fixed output voltage for a tradeoff between the total harmonic distortion (THD ${_\mathit{i}}$ ) and efficiency. Thus, many converter-cell integrated buck-type converters have been proposed to eliminate the dead zones, which unfortunately deteriorate efficiency due to the extra components.This article proposes a group of bridgeless buck-type integrated topologies. Then, a dead-zone-free bridgeless buck-type topology with a wide output voltage range is targeted for further study. The studied converter operates in the buck+flyback mode and can automatically change to flyback mode when the dead zones occur, which only requires a simple control. Moreover, an integrated transformer based on an E-E core is investigated to reduce cost and volume. The bridgeless operation modes are introduced, followed by the PF and THD ${_\mathit{i}}$ analysis to optimize its performance. Prototypes are built and tested, which confirm the effectiveness of the converter and the integrated magnetic.

An Isolated Soft-Switched High-Power-Factor Rectifier Based on the Asymmetrical Half-Bridge Flyback Converter

Abstract: This article presents the analysis and design of a high-power-factor rectifier that integrates a discontinuous conduction mode operated Boost input cell with an asymmetrical half-bridge flyback converter (AHBFC). The particular connection of the dc–dc stage with the boost cell makes the dc link voltage decrease at light load, thus naturally limiting the switches’ voltage stress. A suitable design procedure is described that accounts for the resonant nature of the AHBFC, and allows to calculate all converter parameters to meet the design specifications and to achieve zero-voltage turn- on for the switches in any operating condition, considering both input voltage and load variations. The theoretical analysis is validated by experimental results taken on a $\mathbf {160\,}$ W rated prototype, working at the nominal switching frequency $\mathbf {f_{s}= 400\,}$ kHz, with a line voltage rms value ranging from $\mathbf {85\,}$ to $\mathbf {135\;{\mathrm V}}$ .

A Modular Multifunction Power Converter Based on a Multiwinding Flyback Transformer for EV Application

Abstract: In this article, a revolutionary and novel single-stage, multiport power conversion block is proposed. The power conversion concept is based on a bidirectional flyback converter with four-quadrant switches that permit us to seamlessly control the direction of the energy flow and to select which ports are active. This approach, denominated as multicell multiport bidirectional flyback (M2BF), can be used as a modular and a multifunction building block interfacing ac and dc sources and loads in complex conversion systems like the one we can encounter in electric vehicle (EV) applications. The multiport property is obtained due to the multiwinding flyback transformer that interfaces different sources and loads in a simple and effective way. We present and analyze this concept in detail, focusing on different operation modes it can provide (multiport dc–dc conversion, ac–dc conversion, vehicle-to-grid, grid-to-vehicle, and so on) and their possible implementation in the energy distribution network of an EV, where this unique multifunction multiport converter could bring an important breakthrough. The operating principles of the M2BF for different operating modes are described and analyzed, placing emphasis on the modularity of the proposed concept. The overall concept is evaluated and quantified using a gallium nitride (GaN)-based prototype achieving efficiencies higher than 91% that additionally validates the proposed idea experimentally. The presented analysis and experimental results clearly identify the advantages and limitations of the presented concept leaving no doubt about its usefulness to the future EV distribution network.

Modified PWM Scheme to Reduce Reverse Conduction Loss in GaN-Based Independently Controlled Multiple Output Flyback Converter

Abstract: The recently proposed independently controlled multiple output flyback converter (ICMOFC) scheme improves cross-regulation by utilizing gallium nitride (GaN) switches with negative gate turn-off voltage. The highly inefficient reverse conduction (RC) of negative gate biased GaN devices leads to significant RC loss in the existing ICMOFC scheme. To mitigate this problem, this letter proposes a new pulsewidth modulation (PWM) scheme. The RC loss reduction is achieved by reducing the RC duration and RC current. The effectiveness of the proposed PWM strategy is analytically and experimentally verified using a 40-W dual output flyback converter. The results demonstrate a peak efficiency improvement of 1.26% over the existing ICMOFC scheme. Furthermore, the scheme also achieves high power density (51 W/in$^{3}$) and excellent cross-regulation (0.2%).

Synthesis of Hard and Soft Switching Skills of The MOSFET With the Flyback Converters

Abstract: In this paper, hard and soft switching synthesis and skills both are highlighted to ascertain the power loss modeling, power loss allocations, switching loss reductions and performance analysis of the Flyback converter used by silicon carbide (SiC) which is better than the normal silicon (Si) MOSFET. The SiC MOSFET are also beneficial for the high voltage and high switching frequency applications. The SiC semiconductors not only uses for high power density but gives also better performance in high operating switching frequency Flyback SMPS. SiC MOSFET also reduces the conduction loss due to lower value of its drain to source resistance and switching resistance both to improve the circuit efficiency and performance as well of the power converter while switching characteristics and performance study are exposed under a same tent and platform for practical applications

An Efficient MPPT Technique-Based Single-Stage Incremental Conductance for Integrated PV Systems Considering Flyback Central-Type PV Inverter

Abstract: Central-type photovoltaic (PV) inverters are used in most large-scale standalone and grid-tied PV applications due to the inverter’s high efficiency and low-cost per kW generated. The perturbation and observation (P&O) and incremental conductance (IncCond) have become the most common techniques for maximum power point tracking (MPPT) strategies of PV/wind generation systems. Typically, the MPPT technique is applied in a two-stage operation; the first stage tracks the MPP and boosts the PV voltage to a certain level that complies with grid voltage, whereas the second stage represents the inversion stage that ties the PV system to the grid. Therefore, these common configurations increase the system size and cost as well as reduce its overall footprint. As a result, this paper applies two IncCond MPPT techniques on a proposed single-stage three-phase differential-flyback inverter (DFI). In addition, the three-phase DFI is analyzed for grid current negative-sequence harmonic compensation (NSHC). The proposed system efficiently provides a MPPT of the PV system and voltage boosting property of the DC-AC inverter in a single-stage operation. Moreover, the MPPT technique has been applied through the DFI using the conventional and modified IncCond tracking strategies. Furthermore, the system is validated for the grid-tied operation with the negative-sequence harmonic compensation strategy using computer-based simulation and is tested under uniform, step-change, as well as fast-changing irradiance profiles. The average efficiencies of the proposed system, considering the conventional and modified IncCond MPPT techniques, are 94.16% and 96.4% with tracking responses of 0.062 and 0.035 s and maximum overshoot of 46.15% and 15.38%, respectively.

A MHz-Pulse-Transformer Isolated Gate Driver With Signal-Power Integrated Transmission for Medium-Voltage SiC MOSFETs

Abstract: The conventional isolated gate driver (GD) solution for the medium-voltage (MV) SiC mosfet separates the signal and power transmissions and requires a bulky GD power supply (GDPS). This article presents a signal-power integrated GD for MV SiC mosfet s with a compact footprint. The proposed GD transmits both the pulsewidth modulation (PWM) signal and GD power by 20-MHz modulated class-E resonant flyback converters, where the transmitted GD power can maintain constant within the full PWM duty-cycle range (i.e., 0%–100%). In addition, the PWM signal transmission of the proposed GD achieves a low total propagation delay time < 75 ns by utilizing the fast transient of 20-MHz RFCs and the edge-based envelope detector. A printed-circuit-board-based coreless transformer is integrated into the proposed GD to achieve an insulation voltage higher than 10 kV _RMS and a low coupling capacitance of 5.85 pF. The common-mode transient immunity of proposed GD is higher than 100 V/ns, which is beneficial to drive MV SiC mosfet s with high dv/dt . The proposed GD does not require additional GDPSs nor fiber-optics, which achieves a smaller size compared to conventional isolated GDs and is promising to be integrated into SiC mosfet module packages. Experimental results on 3.3 kV and 10 kV SiC mosfet s are provided to validate the effectiveness of the proposed GD.

Active-Clamp Flyback Converter as Auxiliary Power-Supply of an 800 V Inductive-Charging System for Electric Vehicles

Abstract: Investigation of active-clamped flyback (ACF) dc-dc converter 57W used as the auxiliary power-supply (APS) of an inductive-charging system (ICS) is presented. The ACF was supplied from variable-dc-link 800V which was challenge for its design. Anyway, some findings are applicable to any ACF. An overview of ACF control ICs is presented revealing that only two vendors have appropriate devices for ICS. The key-parts’ choice and suggestion of new features targeting ACF in this emerging-application are given. Striving for high switching-frequency in ICS is not needed due to large safety-distances of transformer. Measured “ maximum-efficiency vs. magnetizing-inductance ” graph showed that extremes are reached for 400 $\mu \text{H}$ . It was based on four transformers with manually-optimized resonant-tanks. Measurements of “ circulating-power losses vs. input-voltage ” are compared for several transformers. Those losses are in the range of few watts and increase with input-voltage. Measurements of “bandwidth, phase-margin and gain-margin vs. input-power”, for different input-voltages, are discussed. Those quantities were changeable with load and input-voltage as expected. The short-circuit behavior is analyzed showing that usage of the hybrid-clamp with multi-mode control-ICs is mandatory. Finally, comparison with conventional flyback and quasi-resonant flyback converters showed that both are ≈23% cheaper, occupy ≈11% less board-space, and have similar or higher efficiencies. The reason for such efficiency is that ACF circulating-power losses were high as well as dc-voltage-conversion-ratio. Although this is a drawback, for an APS the efficiency is not the key-parameter as long as there are no thermal problems. Moreover, as ACF converter is known for having less EMI-problems that could be the key-advantage for this application. But problem is not-enough electronic components on the market that are suitable for ICS.

Self-Operating Flyback Converter for Boosting Ultra-Low Voltage of Thermoelectric Power Generator for IoT Applications

Abstract: This article presents a novel self-operating flyback converter to boost the ultra-low voltage produced by thermoelectric power generator (TEG). The proposed converter uses dual transformer, one for low-voltage startup and other to extract power from TEG. The use of separate transformer provides high-voltage transfer ratio, reduces high series resistance loss, and brings down the input impedance of circuit. The copper wire wounds ferrite toroid core transformer provides very low series resistance and negligible core loss, which improves the circuit efficiency. This boost converter operates with an input voltage range of 22–300 mV and provides maximum output power of 0.073 – 147 ${\rm{mW}}$ correspondingly. The peak efficiency of 68% with output power of 1.32 ${\rm{mW}}$ (voltage ∼1.83 V) is achieved at an input voltage of 50 mV. For regulated output voltage, a feedback loop is used to keep output voltage constant during sudden voltage rise of TEG. The proposed circuit uses discrete components, ferrite toroid core, and PCB, which has lower cost than available energy harvester module, which uses energy harvesting ICs, discrete components, and tiny transformer. The lower startup voltage, higher output power, and voltage with high conversion efficiency of this boost converter maximize the applications potential of the TEG as a portable power source for Internet of Things (IoT) devices.

Lossless Snubber for GaN-Based Flyback Converter With Common Mode Noise Consideration

Abstract: The previous lossless snubber for flyback converters, although with a small number of components, simple control and high power conversion efficiency, has no consideration for electromagnetic interference (EMI). This paper proposes a lossless snubber converter with a novel drain voltage rising slew rate control for the main switch of the flyback converter. Compared to traditional topologies, the proposed snubber topology has two advantages: first, only an additional inductor is used. Second, the proposed method can reduce EMI emissions significantly. Finally, a prototype of the proposed snubber is built and verified with two existing similar snubbers.

Performance Comparison of Silicon- and Gallium-Nitride-Based MOSFETs for a Power-Efficient, DC-to-DC Flyback Converter

Abstract: : Gallium Nitride (GaN)-based devices offer many advantages over conventional electronic devices, such as lower input/output capacitances, a higher switching speed, and a compact size, resulting in higher-density power outputs and reduced switching losses. This research investigates the power and switching efficiency of GaN-based FET in an active-clamp, DC-to-DC flyback converter for step-down application (24 V to 7 V) and compares it with silicon (Si)- based devices in the same circuit topology. The operation is analyzed under various input conditions and output loads such as R, RC, RL, and RLC. The proposed topology can achieve a maximum power-conversion efficiency of 99.6% and can operate at higher frequency values above 1 MHz. The presented GaN-based flyback model can replace conventional Si-based switches in power applications which require high power-efficiency and switching speed in a compact device.

Adaptive Sliding-Mode Controller for Flyback-Based PV Systems Featuring Constant Switching Frequency

Abstract: This paper proposes a sliding-mode controller to ensure both the global stability and maximum power generation of a photovoltaic system based on a flyback converter. The controller is based on an adaptive sliding-surface, which is designed to impose a constant frequency to the switching converter, thus simplifying the selection of both the passive and active elements of the device. Moreover, the controller stability is analyzed using the transversality, reachability and equivalent control conditions. The solution also includes an auto-tuning process for the parameters of the perturb and observe algorithm, which are calculated to ensure the global stability of the sliding-mode controller, thus ensuring the PV system stability. Finally, the performance of the complete solution is verified using detailed circuital simulations of a realistic application case.

Zeta/Flyback Hybrid Converter for Solar Power Applications

Abstract: This paper presents a zeta/flyback hybrid converter with a PV array as its power source for an LED street light or digital signage application. When the PV array is used in a LED lighting system, it needs a battery charger and discharger. In order to increase the areas of application for different PV arrays, a zeta converter has been adopted as the battery charger. In addition, since a flyback converter has a simpler circuit, it is used as the battery discharger. Due to the leakage inductor of the transformer in the flyback converter, an active clamp circuit is used to recover the energy stored in leakage inductance. Zeta and flyback converters use switch integration techniques to form the proposed zeta/flyback hybrid converter. With this approach, the proposed system has less components, a lighter weight, a smaller size, and higher conversion efficiency. Finally, a prototype of the proposed hybrid converter with an output voltage of 12 V and output power of 50 W has been implemented to verify its feasibility. It is suitable for LED lighting system applications.

A Secondary-Resonance MHz Active-Clamp Flyback Converter With Partial Power Processing

Abstract: A 1 MHz active-clamp flyback converter for solar street-lighting applications, featuring a partial power processing, is proposed in this article. The secondary-side resonance between the output capacitor and transformer leakage inductor is utilized to reduce rms current and conduction losses. In comparison with the traditional light-emitting diode drivers based on full power converters (FPCs), the proposed approach that uses partial power converters (PPCs) can significantly improve the overall system efficiency by eliminating the redundant power handling process. The universal schemes are discussed and the optimal solution is eventually determined by the partial power ratio. The advantages of PPC compared with FPC in device stress, losses, and regulation capability are demonstrated by simulation. With GaN devices, a 100 W/1 MHz prototype was built to verify the analysis. The experimental results show that the proposed topology can reduce the power rating of the converter by up to about 80% while increasing the system efficiency by up to 95.8%.

Single Stage Active Power Factor Correction Circuit for Street LED Light with Battery Backup

Abstract: This paper proposes a single-stage active power factor correction circuit for street LED light with battery back-up. The buck–boost converter and flyback converter are combined to achieve optimal performance. The first part of the integrated LED driver, the buck–boost converter is used to adjust the power while operating in the discontinuous conduction operation. The second part of the driver, the flyback converter provides regulated voltage to the LEDs. The battery backup circuit charges the battery when ac input power is available and provides power to LED lamp when input power supply is not available. The proposed LED driver was designed for 100 W output power and tested by PSpice simulation. The simulation results obtained are given in the paper to demonstrates the functionality of the proposed LED driver system. The result show good operation and performance of proposed LED driver.

A Unified Modeling Approach to Tapped Inductor Converters Accounting for the Leakage Inductance Effects

Abstract: This article suggests a unified modeling approach to the analysis of tapped-inductor converters. The leakage inductance, inherent to coupled magnetic structures, and the associated snubber circuit effects were considered and incorporated into the suggested model. The proposed nonideal tapped inductor switcher model is formulated as an equivalent subgraph that can help to model most, if not all, converter topologies that comprise a two-winding tapped inductor. Both the continuous current mode and the discontinuous current mode were modeled. To validate the proposed approach, analysis of a Flyback converter with an RC snubber is presented. Theoretical prediction of the steady-state and small-signal behavior of the converters were confirmed by simulation and experimental results.

Using Your Beam Efficiently: Reducing Electron Dose in the STEM via Flyback Compensation

Abstract: Abstract In the scanning transmission electron microscope, fast-scanning and frame-averaging are two widely used approaches for reducing electron-beam damage and increasing image signal noise ratio which require no additional specialized hardware. Unfortunately, for scans with short pixel dwell-times (less than 5 μs), line flyback time represents an increasingly wasteful overhead. Although beam exposure during flyback causes damage while yielding no useful information, scan coil hysteresis means that eliminating it entirely leads to unacceptably distorted images. In this work, we reduce this flyback to an absolute minimum by calibrating and correcting for this hysteresis in postprocessing. Substantial improvements in dose efficiency can be realized (up to 20%), while crystallographic and spatial fidelity is maintained for displacement/strain measurement.

Stability Analysis of Constant Current-Controlled Primary-Side Regulation Flyback Converter

Abstract: In low power applications, primary-side regulation (PSR) flyback converter with discontinuous conduction modulation (DCM) mode is widely used to realize constant output current for its simple structure and low cost. In peak current control method, the output current can be predicted from the primary peak current, demagnetization time, and switching period. Based on the current prediction, a pulsewidth modulation (PWM) mode and a pulse frequency modulation (PFM) mode are used. However, as the output current cannot be sampled directly in PSR flyback converter, traditional small-signal modeling method based on the control and output variables cannot be used. Moreover, there is no stability analysis for these constant current (CC)-controlled PSR flyback converters. In this article, a discrete matrix analysis method is proposed to analyze the stability of CC-controlled PSR flyback converter. An iterative matrix of the control and output variable perturbations is obtained, and the stability can be acquired from the eigenvalues. Oscillation occurs in the above PWM mode, and a stable control is realized in PFM mode. An improved PWM mode is thus proposed and analyzed for stable control. The analysis is verified in a PSR flyback converter with 1.92 A.

Isolated Flying Capacitor Multilevel Converters

Abstract: This paper presents the topology known as the isolated flying capacitor multilevel flyback converter (FCMFC). The topology uses isolated flying capacitors (FC) for high-gain, DC-DC power conversion while maintaining primary-secondary isolation and improving the efficiency and capability of a standard flyback transformer circuit. Three converters have been developed and tested, one flyback as a control, a 3 level FCMFC, and a 4 level FCMFC to prove the gain and efficiency benefits of this new topology. The FCMFC prototypes achieve higher gain and efficiencies relative to a flyback design utilizing the same off-the-shelf transformer. The stress of the input and output switches is reduced because of the fractioning of the output voltage across multiple output stages, allowing future iterations to utilize lower-rated components. The operating parameters are 5V to 40V boosting for a 10W load at 250kHz. Utilizing the same semiconductor components, the flyback converter control prototype achieves 78% efficiency while the proposed FCMFC converters reach 85% and 82% efficiency, even with the added isolated power, gate drive, and bootstrap circuitry. The FCMFCs have a multiplying effect on the gain of the traditional flyback which also increases near the 90% duty cycle flyback threshold. Additional testing was done at light load and at 100kHz, 250kHz, 452kHz, and 500kHz.