Conventional Flyback Converter Research Articles

An Elimination Scheme of Long and Short Periods for Flyback Converter

For small size, low cost, and wide power range, the constant current (CC) control scheme suitable for both discontinuous conduction mode and continuous conduction mode (CCM) is prevalent in low and medium power applications. However long and short periods (LSP) emerge due to the inner control relationship of conventional flyback converter especially in CCM. An adaptive over current protection (OCP) control scheme is adopted to eliminate LSP. A threshold regulator and a calibrated protector are used to correct the OCP threshold dynamically in the proposed OCP circuit. To verify the feasibility and performance, the proposed scheme has been implemented in 0.18lm BCD process. The experimental results show that the LSP is eliminated and deviation of the CC is within ±1.04% under different input and load conditions.

Active-clamped flyback DC-DC converter in an 800V application: Design notes and control aspects

Abstract This paper presents findings for active-clamped flyback (ACF) DC-DC converter 57 W used as an auxiliary power-supply of a wireless inductive-charging system 800 V. Measurements of magnetizing and leakage inductances for three transformers demonstrated how big differences between them could be depending on chosen vendor. Comparison of simulated and measured Bode plots showed that, even when those plots were not matched, one could design a compensator that ensures stable operation. Evaluation of cross-regulation when output with low power (9.62 % of total) was regulated showed that such approach was feasible too. The switching frequency vs output-power and drain-source voltage of switch vs output-power graphs are presented for the first time. Comparison of bandwidth, phase-margin and gain-margin vsinput-power, between the ACF and conventional flyback converter were discussed too. Those quantities were changeable with load and input-voltage as expected. The conventional flyback converter in DCM has higher bandwidth than the ACF which resulted in lower phase- and gain-margins. That showed that it cannot have the same compensator as an ACF.

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

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 “ <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">maximum-efficiency vs. magnetizing-inductance</i> ” graph showed that extremes are reached for 400 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{H}$ </tex-math></inline-formula> . It was based on four transformers with manually-optimized resonant-tanks. Measurements of “ <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">circulating-power losses vs. input-voltage</i> ” 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.

Bidirectional Current-Fed CLLC Resonant Converter Employing Asymmetric PWM

A power systems of wearable application requires high power conversion efficiency and bidirectional power flows to obtain the compatibility with various power sources and loads. The conventional flyback converter has a simple structure and bidirectional power conversion capability. However, it shows poor power conversion efficiency caused by hard-switching operation, high DC offset current on the transformer, snubber losses, and large peak current. In this paper, a current-fed CLLC resonant converter is proposed to obtain the high power conversion efficiency and the bidirectional power conversion capability. The soft-switching operation, zero DC-offset current, and small peak current can induce high power conversion efficiency. The asymmetric pulse width modulation (APWM) regulates the bidirectional power flows and the output voltage. The design methodology of the proposed converter is analyzed by introducing its operational principles. The performance of the proposed converter is experimentally verified with a 20 W prototype.

Ripple-Free Input Current Flyback Converter Using a Simple Passive Circuit

This article proposes a new ripple canceling circuit (RCC) to eliminate the pulsating input current of the conventional flyback converter (CFC). The ripple canceling procedure occurs by two capacitors, one transformer, and a winding, which is added to the CFC transformer core. Besides, the proposed RCC acts as a passive snubber to reduce voltage spikes on the power switch of the converter. In comparison to the similar existing topologies, the proposed RCC does not employ additional semiconductors, and a lower number of magnetic components are used. The proposed RCC is verified by simulation and experimental results. The results show that using the proposed RCC, the input current ripple is reduced to 6% with the minimum power losses.

철도역사용 LED 유도등에 적용되는 플라이백 컨버터 역률개선에 관한 연구

In this paper, a simple method to improve the power factor of the conventional LED exit light with a flyback converter was proposed. Conventional flyback converters are applied to LED exit lights, which are constant loads, and 4.8[V] batteries are connected in parallel at the output stage. Therefore, by adding a passive filter between the rectifier circuit part and the primary side of the transformer, it is possible to minimize the change of the conventional circuit and improve the power factor. As a result of changing the duty ratio of the flyback main switching device from 25% to 56%, the power factor showed a high result from 95.5% to 98.3%.

Dual range flyback topology for high efficiency at dual voltage mains

This study introduces a dual range flyback converter, which overcomes low efficiency of the conventional flyback converter for universal mains voltages, i.e. 220 and 110 V AC mains. The topology comprises of reconfigurable primary power loops enabled by additional state switches. This combination allows the converter to run in parallel or series modes, enhancing the performance at 220 V AC high line or 110 V AC low line mains. It reduces the voltage rating of devices, supports two working points that operate in boundary conduction mode under fixed frequency and improves the utilisation of the devices. A 100 kHz, 60 W, 110 V AC or 220 V AC to 13 V DC converter has been designed and tested. The experimental results of the proposed converter have been compared against a conventional flyback converter. The results show a small improvement of performance at low voltage (110 V AC) and considerable performance improvement at high voltage (230 V AC): 0.6 and 2.3% efficiency improvement at full load, respectively.

Dual-Mode Resonant Flyback Single Power-Conversion Inverter

This article presents a dual-mode resonant flyback single power-conversion inverter with reduced number of power components. Unlike conventional flyback converters, it transfers power in a resonant manner during the first half of the switching period and in a linear way during the remaining half of the switching period. It operates in above resonance mode below the computed instantaneous power level, and in below resonance mode above this instantaneous power level. The secondary diodes of the resonant flyback converter are merged into two of the secondary-side switches in the proposed inverter configuration, which reduces the number of active-power components. The operation principle of the inverter is presented and analyzed. By using the dual-mode control strategy, the proposed converter achieves maximum efficiency of 94.3% with total harmonic distortion of 3.8%. Experimental results with a prototype 240-W inverter verify the performance.

Design and Implement Regulated DC-DC Interleaved Flyback Converter by Using Intelligent Controller in Airborne Application

This paper is designed, simulated and implemented DC-DC interleaved Flyback converter controlled by Arduino Uno which converts input voltage from battery 12 V to 180 V DC at 20 kHz for 120 W. Digital control design is done with the use of Arduino Uno microcontroller. Simulation carried out using MATLAB/Simulation. The objective of this paper is to design a DC converter that operates at low cost with high efficiency via improving Flyback converter topology. This occurs using interleaved Flyback converter. To obtain a regulated output voltage of the interleaved Flyback converter, closed-loop feedback with PI controller is employed (Proportional – Integral). The duty cycle is varied to control the output voltage and produced constant voltage under variation input voltage and load disturbance. The designed technique uses voltage mode control (VMC) to obtain a constant voltage under continuous conduction mode (CCM). To implement the interleaved Flyback converter with the PI controller, the microcontroller Arduino Uno is used. The Simulation and the practical results give a little output ripple voltage, current, and high efficiency 6% compared with conventional Flyback converter.

A Self-Oscillating Flyback Converter with Primary Feedback Control

Due to its simplicity and low component count, a self-oscillating flyback converter is an ideal topology for cost sensitive applications, such as mobile phone chargers and auxiliary power supplies. To regulate the output voltage, the conventional self-oscillating flyback converter employs a secondary feedback current mode control scheme whose major components include a TL431 error amplifier and optocoupler. These two components nonetheless contribute significantly to a total cost of the self-oscillating flyback converter. A further cost reduction can be achieved, if the error amplifier and optocoupler can be eliminated altogether. This paper proposes a self-oscillating flyback converter with primary feedback control. In the proposed converter, the error amplifier and optocoupler are replaced by a Zener diode, and the output voltage from the auxiliary winding is used as a feedback variable, instead of the actual output voltage from the secondary winding. In the paper, the operation of the proposed converter is described. The prototype converter operating from a 220 V AC main and producing an output of 24 V/0.5 A is fabricated and tested. Experimental results are presented to verify the converter performance as well as to validate the principle of operation.

A New Standby Structure Integrated With Boost PFC Converter for Server Power Supply

In the standby stage of a server power supply, the flyback converter has been widely used due to its simple structure and low cost. However, since the flyback converter suffers from high-voltage stress and a large transformer, it degrades the efficiency and power density of the server power supply. To relieve these drawbacks, this paper proposes a new standby structure where a flyback converter is integrated with a boost power-factor-correction (PFC) converter. The proposed standby structure can relieve the high-voltage stress and eliminate the large transformer of the conventional flyback converter because the primary side of the flyback converter is merged with the boost PFC converter. Thus, the proposed structure can achieve high efficiency and high power density in the standby stage. Furthermore, it can help the boost PFC converter achieve a soft switching operation, which results in a high-efficiency PFC stage. As a result, the proposed structure improves the overall efficiency and power density of the server power supply. The validity of the proposed structure is confirmed by a prototype with 100–240 Vrms ac input, 750-W PFC output, and 12-V/2-A standby output.

Flyback converter with a stepped air-gap transformer

ABSTRACTIn low power applications with isolation requirements (e.g. notebook adapters), the flyback converter is a commonly used converter topology. A key element of the flyback converter is its transformer. This paper introduces a flyback converter with a stepped air-gap transformer designed for a typical 65 W notebook adapter. Conventional flyback converters employ a transformer with a current independent (linear) magnetizing inductance. A stepped air-gap transformer, however, possesses a current dependent (nonlinear) magnetizing inductance. This current dependency can be influenced by the air-gap geometry. Thus, a stepped air-gap transformer offers the advantage of a greater design freedom. The use of a suitable designed stepped air-gap transformer enables an increase of the flyback converter efficiency. Measurements confirm a total loss reduction of up to 6.4%.Abbreviation DCM: Discontinuous conduction mode; BCM: Boundary conduction mode; FEM: Finite Element Method; rms: Root mean square; AC: Alternating current; DC: Direct current; EMC: Electromagnetic compatibility

Investigation of a Soft-Switching Flyback Converter With Full Secondary Side-Based Control

A conventional Flyback converter's controller is based on the primary side of the coupled inductor–requiring isolated coupling for both the output voltage measurement and for any synchronous rectification gate signal. A novel communication approach is proposed here, whereby the need for such signal coupling is eliminated by moving the controller to the secondary side and communicating back to the primary switch through the coupled inductor itself. This simultaneously allows direct access to the output voltage, reduced component count, synchronous rectification, and soft primary switch turn-on without optoisolator propagation delay or additional magnetic coupling. This paper presents a novel drain–source voltage sensing method that provides reliable turn-on signals for the primary switch along with the principles of the secondary-side control. Concept feasibility is proven using a 65 W demonstrator with a simple constant-on-time control scheme. The benefits, limitations, and suggested improvements are presented.

Improved Single-Stage AC-DC LED-Drive Flyback Converter using the Transformer-Coupled Lossless Snubber

This paper presents an improved single-stage ac-dc LED-drive flyback converter using the transformer-coupled lossless (TCL) snubber. The proposed converter is derived from the integration of a full-bridge diode rectifier and a conventional flyback converter with a simple TCL snubber. The TCL snubber circuit is composed of only two diodes, a capacitor, and a transformer-coupled auxiliary winding. The TCL snubber limits the surge voltage of the switch and regenerates the energy stored in the leakage inductance of the transformer. Also, the switch of the proposed converter is turned on at a minimum voltage using a formed resonant circuit. Thus, the proposed converter achieves high efficiency. The proposed converter utilizes only one general power factor correction (PFC) control IC as its controller and performs both PFC and output power regulation, simultaneously. Therefore, the proposed converter provides a simple structure and an economic implementation and achieves a high power factor without the need for any separate PFC circuit. In this paper, the operational principle of the proposed converter is explained in detail and the design guideline of the proposed converter is briefly shown. Experimental results for a 40-W prototype are shown to validate the performance of the proposed converter.

Cell Balancing Method in Flyback Converter without Cell Selection Switch of Multi-Winding Transformer

This paper presents a cell balancing method for a single switch flyback converter with a multi-winding transformer. The conventional method using a flyback converter with a multi-winding transformer is simple and easy to control, but the voltage of each secondary winding coil might be non-uniform because of the unequal effective turn-ratio. In particular, it is difficult to control the nonuniform effect using turn-ratios because secondary coil has a limited number of turns. The nonuniform secondary voltages disturb the cell balancing procedure and induce an unbalance in cell voltages. Individual cell control by adding a switch for each cell can reduce the undesirable effect. However, the circuit becomes bulky, resulting in additional loss. The proposed method here uses the conventional flyback converter with an adjustment made to the output filters of the cells, instead of the additional switch. The magnitude of voltage applied to a particular cell can be reduced or increased according to the adjusted filter and the selected switching frequency. An analysis of the conventional converter configuration and the filter design method reveals the possibility of adequate cell balancing control without any additional switch on the secondary side.

Derivation, Analysis, and Comparison of Nonisolated Single-Switch High Step-up Converters With Low Voltage Stress

This paper presents nonisolated single-switch high step-up converters with low voltage stress. Based on the conventional flyback converter, one single-switch high step-up converter is derived. The voltage stresses on the switch and diodes are limited by using a clamping diode and voltage doubler structure. Also, to further reduce the voltage stresses of them, another single-switch high step-up converter is proposed simply by using one additional capacitor and rearranging the components. Thus, lower voltage-rated switch and diodes can be used, which results in higher efficiency. The operational principle, analysis and design considerations of each converter are presented in this paper. The validity of this study is confirmed by the experimental results from 24 V input and 250 V/125 W output prototype.

Application of Dual Switch Flyback Converter in Three-Phase Photovoltaic Inverter

Auxiliary power of Three-phase photovoltaic inverter is supplied by solar cells with wide input ranging from 140V to 1000V.The conventional single-switch flyback converter exists too high voltage stress in power switch to be applied in this inverter. This paper presents a dual-switch flyback converter in which the voltage stress of each switch is slightly higher than the input voltage when switches turn off, at the same time , the leakage inductance energy is recycled back into the inputside; otherwise, this topology needs no snubber circuit, so it is much more efficient than single switch flyback. The dual switch flyback converter with seven outputs is successfully applied in 10KW three phase PV inverter.

A battery charge controller realized by a flyback converter with digital primary side regulation for mobile phones

A flyback converter with digital control designed and implemented for a lithium battery charging system is proposed in this study. As opposed to the requirement of both voltage and current feedbacks for a conventional flyback converter, this study proposes a converter structure that needs only one voltage feedback to stabilize converter output for implementing the designed battery charging techniques. This single feedback of voltage is made possible by so-called "primary side regulation (PSR)", which in hardware senses the output voltage using an auxiliary winding in the isolating transformer of the flyback converter that is operated in DC---DC discontinuous current mode. The adoption of PSR also enables the elimination of the opto-coupler that is often used in conventional converters for feedback signals. Another essential part of the converter is the proposition of a new a duty control method which regulate successfully the output current by only one feedback voltage signal. The proposed battery charging design consists of three consecutive modes, trickle current (TC), CC and CV. At TC and CC, a duty control method is adopted, which is able to regulate the output current by sensing only the output voltage. Both simulation and experimental results show a 7 % error deviated from targeted output current. As for CV, a proportional-integral controller is designed and implemented to regulate the output voltage. The overall experimental results show a favorable performance of the proposed charging method with proposed PSR-flyback converter.

A Novel Flyback-Based Input PFC Stage for Electronic Ballasts in Lighting Applications

This paper proposes an electronic driver for public lighting systems. The input stage is based on the integration of two flyback converters with different polarities, in order to avoid the use of the input diode bridge rectifying stage. The output stage is a boost converter with an output current control. The proposed circuit is introduced and analyzed, and a design example for a 50-W light-emitting diode lamp is presented. The most relevant simulation and experimental results are also shown, in order to validate the idea. A comparison in terms of efficiency for the input stage is carried out between the proposed topology and the conventional flyback converter, showing an efficiency enhancement in the proposed converter. However, the most important advantage of the proposed converter is outlined in the final part of this paper. This advantage comes from the avoidance of the input diode bridge, thus enabling the bidirectional power flow at the input stage. Therefore, the topology can be used to deliver energy into the power grid. In recent lighting applications, the use of micro renewable generators in lighting points has made the use of special electronics to handle the energy flows in the ballast necessary. The present topology is an alternative to standard bidirectional input stages.

Flyback-based high step-up converter with reduced power processing stages

This study proposes a non-isolated converter derived from the conventional flyback topology based on the concept of reduced power processing. The proposed converter has higher-voltage gain, improved efficiency and reduced component stresses owing to recycling of leakage energy and clamped power switch voltage when compared with the conventional flyback converter, and yet retains the advantages of circuit simplicity and low cost. A complete analysis including converter operation and its dc and ac characterisations are presented in the paper. Using a 60 W laboratory prototype operating at 100 kHz with 24 V input voltage and 200 V regulated output voltage, experimental evaluation of the efficiency improvement, steady-state and transient-response performance are presented to verify the effectiveness of the proposed converter.