Showing papers on "Flyback converter published in 2020"

Synthesis of Integrated Multiport DC–DC Converters With Reduced Switches

Abstract: With the increasing demand of different voltage levels in industrial applications, multiport dc–dc converters have been widely employed owing to their low-cost merits. Aiming to provide more multiport topologies so that engineers can select out a preferred one for the specified application, this article proposes a novel principle to systematically implement topology derivation by replacing switches in original converters with pulsating current source cells. This principle is simple and effective, with which multiple new integrated multiport converters having a low number of switches are easily evolved. The advantage of reduced switches is very beneficial for the low-power applications with relatively less switches since the overall cost can be effectively improved. And in order to achieve a comprehensive understanding of the proposed converters, an example single-input dual-output converter that integrates the asymmetrical half-bridge flyback converter with the buck converter is analyzed in detail. It operates similarly with the two separate converters, but with favorable advantages of reduced switches and improved switching operation. Finally, an experimental prototype is built to verify the theoretical analysis.

Analysis and Optimal Design of High-Frequency and High-Efficiency Asymmetrical Half-Bridge Flyback Converters

Abstract: The asymmetrical half-bridge (AHB) flyback converter is capable to achieve zero voltage switching and has lower voltage stress compared to the active clamp flyback converter. This topology gives much margin for components selection and transformer turns ratio design. It is well adapted to voltage step-down applications. However, the optimal design for AHB flyback converter taking current dip effect causing by components parasitic capacitances, and each component effect to power loss into consideration has never been explored. This article gives detailed operation and mathematical analyses of this effect. The optimal design procedure with the consideration of each circuit parameter is presented in this article. The transformer benefits low power loss from interleaving winding layout. A 56 W/inch3 1 MHz 65 W prototype with 100–250 V input is built to verify the feasibility of the converter. Experimental results show the peak efficiency 96.5% is achieved with 127 V input and the whole system efficiency under the entire input voltage range is above 93%.

A Hybrid Modulation Method for Single-Stage Soft-Switching Inverter Based on Series Resonant Converter

Abstract: Pseudo-dc-link inverters are promising due to the single-stage configuration. The inverters can be isolated by high-frequency transformers, which also provide the freedom of step-up/down through winding turns ratio. Conventionally, a pseudo-dc-link inverter is based upon a pulsewidth modulation converter like flyback converter, but the accompanying switching losses can degrade efficiency and overall system performance. Alternatively, resonant converters (e.g., series resonant converter) seem to fit the need as they typically display soft-switching characteristics. However, the relevant research results are scarce because of two main reasons: high resonant current and limited soft-switching range. To overcome the difficulties, a hybrid modulation method is proposed in this article for a pseudo-dc-link inverter based on series resonant converter. In high-line region, the inverter operates with variable-frequency modulation, which leads to zero-voltage switching and relatively low-resonant current. In low-line region, the inverter operates with a short-pulse density modulation so that switching losses are greatly curtailed without excessive resonant current. The merits in both regions together contribute toward the high efficiency of the inverter. This article presents the operational principle of the proposed modulation as well as a comparison with other modulation methods. In addition, a 400 V–230 V ac, 2-kW prototype was built to verify the proposed modulation and the peak efficiency reaches 98.0%.

A Modified Asymmetrical Half-Bridge Flyback Converter for Step-Down AC–DC Applications

Abstract: This article presents a modified asymmetrical half-bridge flyback converter (AHBFC) to fulfill the single-stage step-down ac-dc universal input voltage application. This topology is obtained from the integration of a buck-type power factor correction, an auxiliary energy buffer, and a conventional AHBFC. By sharing common switches and utilizing transformer's leakage inductor, the single-stage circuit can achieve both high power factor (PF) and low total harmonic distortion with the simple constant on-time control while regulating the dc output voltage. In addition, it is able to operate in universal input voltage with low dc link voltage and low output voltage. Moreover, the zero voltage switching and the zero current switching features of the power switches can also be achieved. Detailed analyses and design procedures of the proposed converter are given and verified by the experimental results. Finally, the comparison with reported circuit topologies and power loss analyses verified by experimental results are presented to provide the insight of practical design.

Interleaved Landsman Converter Fed EV Battery Charger With Power Factor Correction

Abstract: In this paper, an electric vehicle (EV) battery charger with interleaved Landsman converter (ILC) followed by a flyback converter, is designed and evaluated for improved power quality (PQ) charging of battery. A built-in wave-shaping is obtained at the charger front-end due to improved PQ characteristics of ILC. This PFC converter consists of two Landsman converter cells, which are designed in discontinuous conduction mode (DCM) to share the input and output currents. The current sharing at input results into lower input current ripple as well as peak current stress through the switch, is reduced. This, further improves the input current harmonics profile. Moreover, the reduced output voltage ripple gives reduced rms current in the output capacitor. A phase shift PWM scheme (PSPWM) is used for ILC and the duty cycle for the switches is selected below 50%. This allows the ripple cancellation at line and load sides. The interleaving at PFC stage as well as DCM based design ensures a low cost charging solution as compared to the conventional Landsman converter (CLC) based chargers in this power range. However, the flyback converter provides the current control during the charging of the battery in constant current (CC) and constant voltage (CV) regions. The harmonics spectrum of mains current follows the recommended PQ regulations over a range of varying line voltages and loadings.

A Digital Control Scheme for PSR Flyback Converter in CCM and DCM

Abstract: Due to the simple structure and low cost, the primary-side-regulation (PSR) flyback converter is widely used in small power applications. As the output voltage is sampled from auxiliary winding in PSR flyback converter, some sampling error exists, especially when continuous conduction mode (CCM) is introduced for higher power. To improve the constant voltage accuracy, a novel digital controlled sampling strategy is proposed. This scheme uses a digital ramp sampling method to sample output voltage in both discontinuous conduction mode (DCM) and CCM, and proposes a voltage adjustment strategy to adjust sampling errors in CCM without weakening the stability in the load-switch process. Finally, the experimental results validate the presented scheme and show that the output voltage error is less than 0.6% in a 20-V, 5-A PSR flyback prototype.

An Active and Passive Hybrid Battery Equalization Strategy Used in Group and between Groups

Abstract: Active battery equalization and passive battery equalization are two important methods which can solve the inconsistency of battery cells in lithium battery groups. In this paper, a new hybrid battery equalization strategy combinfigureing the active equalizing method with a passive equalizing method is proposed. Among them, the implementation of the active equalizing method uses the bidirectional Flyback converter and Forward converter. This hybrid equalizing strategy adopts the concept of hierarchical equilibrium: it can be divided into two layers, the top layer is the equalization between groups, and the bottom layer is the equalization of group. There are three active equilibrium strategies and one passive equilibrium strategy. For verification purposes, a series of experiments were conducted in MATLAB 2018b/Simulink platform. The simulation and experiment results show that this hybrid battery equalizing method is efficient and feasible.

Novel voltage equalisation circuit of the lithium battery pack based on bidirectional flyback converter

Abstract: Lithium batteries have become the main power source for new energy vehicles due to their high energy density and low self-discharge rate. In actual use of series battery packs, due to battery internal resistance, self-discharge rate and other factors, inconsistencies between the individual cells inevitably exist. Such inconsistencies will reduce the energy utilisation rate and service life of the battery pack, and even endanger its battery system safety. To improve the inconsistency of series battery packs, this study innovatively proposes an equalisation method based on a flyback converter. The residual power of a single cell is used as an index of inconsistency. A simple and reliable flyback converter is used to achieve balanced energy in the entire group, which make the energy is transferred between any batteries. Compared with the traditional equalisation topology, the equalisation topology proposed in this study reduces the number of components and reduces the volume of the equalisation system. Moreover, the primary side of the energy transfer only needs a set of control signals, which reduces the control difficulty. A series of equalisation experiments were performed using 12 series of battery cells. The results show the effectiveness of the proposed new equalisation method.

A Bipolar ±13 mV Self-Starting and 85% Peak Efficiency DC/DC Converter for Thermoelectric Energy Harvesting

Abstract: This paper presents a novel converter for boosting the low-voltage output of thermoelectric energy harvesters to power standard electronic circuits. The converter can start up from a fully depleted state of the system off a bipolar ±13 mV input and can boost it to output voltages of up to 5 V. The converter comprises two transformers, one for each polarity that are multiplexed between an oscillator (used during startup) and a flyback converter (used during normal operation). To eliminate leakage currents in the input stage, the unused converter is completely turned off at startup and both converters are automatically shut off if the input power is found to be too low. Measurement results of the converter designed in a 180 nm CMOS process demonstrate a peak end-to-end conversion efficiency of 85% and nearly perfect impedance matching over the full input voltage range. This is the first time that a converter for ultra-low bipolar input voltages achieves the same performance as a unipolar converter.

A New Primary PWM Control Strategy for CCM Synchronous Rectification Flyback Converter

Abstract: A new primary PWM (pulsewidth modulation) control strategy for continuous conduction mode (CCM) synchronous rectification (SR) flyback converter is proposed in this letter. The PWM signal for the primary switch has been divided into two pulses in a switching period (dual-pulse PWM, DP-PWM). The first pulse is a fixed narrow pulse, which is used to turn off the SR, whereas the second pulse is a regulated pulse for output voltage regulation. With the proposed DP-PWM control scheme, the shoot-through currents exist on both the primary side and secondary side of the CCM SR flyback converter can be effectively reduced. Meanwhile, the efficiency has been improved obviously. Detailed theoretical analysis has been presented and verified by a 12 V/2.5 A CCM flyback experimental prototype.

A New CCM/DCM Hybrid-Mode Synchronous Rectification Flyback Converter

Abstract: A new continuous conduction mode (CCM)/discontinuous conduction mode (DCM) hybrid-mode synchronous rectification (SR) flyback converter is proposed in this paper. This converter is realized by adding a combined switch in parallel with the auxiliary winding of the flyback transformer. The added switch is controlled to conduct a short period before the primary switch turns on , which shorts the windings of the transformer. The drain-source voltage of SR arises rapidly to reach the turn- off threshold voltage inside SR controller and the SR is turned off before the primary switch conducts. In this way, the overlapped period existed in a conventional CCM SR flyback converter is eliminated. Meanwhile, the normal operation of SR flyback in DCM is not affected. Detailed theoretical analysis has been presented and verified by a $12\,\text{V}/ 2.5\,\text{A}$ CCM/DCM hybrid-mode flyback experimental prototype. The results prove that the efficiency of the proposed SR method in CCM can be improved compared with the conventional one.

The Novel Quasi-Resonant Flyback Converter With Autoregulated Structure for Parallel/Serial Input

Abstract: In this paper, a novel quasi-resonant flyback converter that mainly comprises two modules of flyback converters is proposed. A relay is connected in series to the input terminals of two transformers, and the transformer input structure is adjusted according to the input voltage to improve the conversion efficiency. In addition, a novel frequency-limiting quasi-resonant control strategy for solving the limitations of the conventional quasi-resonant control strategies is proposed, wherein the switching frequency is increased under light load conditions. Here, the current-mode pulsewidth modulation IC is used as the core controller. The operating principle and design parameters of the converter are analyzed and discussed in detail. The experimental results prove the feasibility of the proposed circuit.

A Capacitor-Free Control Scheme for a Primary-Side Controlled Flyback Converter

Abstract: A capacitor-free control scheme is presented for primary-side regulation (PSR) flyback converter to reduce cost and increase system reliability. Compared to conventional voltage compensation, the proposed converter using an error amplifier sampling scheme reduces zero and pole as load decreases, and thus, the stability of the system makes significant strides especially under light loads. The proposed controller provides high stability and fast load transient response even in capacitor-free scheme. Besides, a ramp voltage with reduced slope is allowed to pursue a wider output load range and further reduce switching frequency for lighter load. The proposed controller is implemented in 0.18- μ m 100-V BCD process and occupies a die size (with pads) of 1.3 × 1.2 mm2. The experimental results show that the deviations of output voltage are within ±0.35% under different inputs and loads while the peak power efficiency of 87.3% is achieved.

Power Loss Analysis and a Control Strategy of an Active Cell Balancing System Based on a Bidirectional Flyback Converter

Abstract: This research proposes a power loss analysis and a control strategy of an active cell balancing system based on a bidirectional flyback converter. The system aims to achieve an energy storage application with cells connected in 6 series and 1 parrarel (6S1P) design. To reduce the structural complexity, Metal-Oxide-Semiconductor Field Effect Transistor (MOSFET) array commonly used in balancing system is replaced with the photovoltaic Metal-Oxide-Semiconductor (photoMOS) array. Power loss analysis is utilized for the system operating in the proper current to reach higher efficiency. The proposed loss models are divided into conduction loss, switching loss, and copper and core loss of the transformer. Besides, the models are used to estimate the loss of converter operating in different balance conditions to evaluate the system efficiency and verified by the implemented balancing circuit. By way of the loss models, the balancing current can be determined to reach higher efficiency of the proposed system. For further improvement of the balancing process, the system has also applied a control strategy to enhance the balancing performance that reduces 50% maximum voltage difference than traditional cell-to-pack architecture, and 47% balancing duration than traditional pack-to-cell architecture.

A Constant Current Digital Control Method for Primary-Side Regulation Active-Clamp Flyback Converter

Abstract: Active-clamp flyback converter is now widely used because higher efficiency is obtained with soft-switching technique. However, opto-coupler is always applied in the feedback loop to acquire the output signal. To avoid the non-linearity and temperature drift of the opto-coupler, a constant current digital control method with peak current control is proposed for primary-side regulation active-clamp (PSRAC) flyback in this paper. Considering the charge balance principle, the output current can be calculated and controlled with primary-side control and only one low speed digital to analogy converter (DAC), two comparators and a digital unit are required in discontinuous conduction modulation (DCM) mode. Based on the proposed method, constant output current is realized. The proposed control scheme was verified by a FPGA controlled 2.00-10.00V/2.00A ac-dc PSRAC flyback converter.

Modeling and simulation of an integrated octagonal planar transformer for RF systems

Abstract: The work presented in this paper concerns the modeling of an integrated transformer in monolithic technology for high frequencies containing coils of planar type and magnetic circuit made of several layers of materials. Circular, square, and polygonal shapes of the planar coils are the important difference regarding transformer topologies. In this work, we have chosen the stacked octagonal form of coils. The transformer will be integrated into a converter of type flyback. We have opted for the Wheeler method and the S-parameters for determining the geometrical and the electrical parameters. The electrical π model presented summarizes perfectly the various parasitic effects generated by stacked layers of different materials constituting the transformer. The electromagnetic simulation, by using COMSOL Multiphysics 4.3 software, illustrates the current density and the distribution of magnetic field lines. We have also used software PSIM 6.0, to validate the equivalent electrical circuit of the transformer in flyback converter.

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, the demagnetization time and the switching period. Based on the current prediction, a pulse width 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 modelling method based on the control and output variables cannot be used. And there is no stability analysis for these constant current (CC) controlled PSR flyback converters. In this paper, 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 above PWM mode and 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 1.92A.

Flyback Converter for Solid-State Lighting Applications with Partial Energy Processing

Abstract: The main contribution of this paper is to show a new AC/DC converter based on the rearrangement of the flyback converter. The proposed circuit only manages part of the energy and the rest is delivered directly from the source to the load. Therefore, with the new topology, the efficiency is increased, and the stress of the components is reduced. The rearrangement consist of the secondary of the flyback is placed in parallel with the load, and this arrangement is connected in series with the primary side and the rectified voltage source. The re-arranged flyback is only a reductive topology and with no magnetic isolation. It was studied as a power supply for LEDs. A low frequency averaged analysis (LFAA) was used to determine the behavior of the proposed circuit and an equivalent circuit much easier to analyze was obtained. To validate the theoretical analysis, a design methodology was developed for the re-arranged flyback converter. The designed circuit was implemented in a 10 W prototype. Experimental results showed that the converter has a THDi = 21.7% and a PF = 0.9686.

Modeling and Analysis of the Fractional-Order Flyback Converter in Continuous Conduction Mode by Caputo Fractional Calculus

Abstract: In order to obtain more realistic characteristics of the converter, a fractional-order inductor and capacitor are used in the modeling of power electronic converters. However, few researches focus on power electronic converters with a fractional-order mutual inductance. This paper introduces a fractional-order flyback converter with a fractional-order mutual inductance and a fractional-order capacitor. The equivalent circuit model of the fractional-order mutual inductance is derived. Then, the state-space average model of the fractional-order flyback converter in continuous conduction mode (CCM) are established. Moreover, direct current (DC) analysis and alternating current (AC) analysis are performed under the Caputo fractional definition. Theoretical analysis shows that the orders have an important influence on the ripple, the CCM operating condition and transfer functions. Finally, the results of circuit simulation and numerical calculation are compared to verify the correctness of the theoretical analysis and the validity of the model. The simulation results show that the fractional-order flyback converter exhibits smaller overshoot, shorter setting time and higher design freedom compared with the integer-order flyback converter.

Double boost-flyback converter

Abstract: A high-gain step-up non-isolated dc–dc converter is proposed in this study, named the double boost-flyback converter. The topology combines two conventional boost-flyback converters with input-parallel and floating-output connections. The new topology increases the static gain and reduces the input current ripple in relation to the conventional boost-flyback topology. The proposed converter has the potential to be used in low input voltage applications that require a high gain, such as systems powered by photovoltaic panels, fuel cells, electric vehicles, and low voltage batteries. This study provides details on the principle of operation, static gain, control strategy, design guide and experimental verification. A 1 kW prototype was designed and built for an input voltage of 48 V and an output voltage of 800 V, reaching a static gain of 16.67. The maximum efficiencies obtained were 94.6% at 70% of load and 93.9% at rated load.

Switching power supply device

Abstract: The invention discloses a switching power supply device. The switching power supply device comprises an asymmetric half-bridge flyback converter and a controller; and the asymmetric half-bridge flyback converter is used for converting an input voltage into an output voltage, and comprises a main switch, an auxiliary switch, a transformer and a one-way clamping network used for controlling a negative peak value of an excitation inductive current. A controller is used for controlling the main switch, the auxiliary switch and the one-way clamping network, so that the switching power supply deviceworks in a certain working state. The switching power supply device is characterized in that when the output load current is greater than or equal to a first load current set value, the controller enables the switching power supply device to work in an asymmetric half-bridge flyback mode; and when the output load current is smaller than the first load current set value, the controller enables theswitching power supply device to work in a clamping asymmetric half-bridge flyback mode. Under the condition that the advantages of full load and heavy load high efficiency of the switching power supply device are kept, the current effective value of the power device under light load and no load can be reduced, the light load efficiency is greatly improved, and the no-load loss is reduced.

Average Inductor Current Measure and Control Strategy for Multimode Primary-Side Flyback Converters

Abstract: Primary-side flyback converter (PSR) is widely used among small and medium power applications for its simplicity and cost effectiveness. However, it is hard to measure the current of secondary side due to the special structure characteristic of PSR. Conventionally, a peak current measurement strategy is adopted to measure the current of primary inductor. However, the sampling method is just for one conduction mode and is affected by the propagation delay between the control signal and actual turn- off instant of mosfet . Thus, a compensation circuit is needed to improve the accuracy, which leads to a large area and cost of the controller. In this work, a kind of average inductor current measure and control strategy for multimode is introduced. The average inductor current measurement strategy is based on the Miller stage to recognize the state of the mosfet, which eliminates the error caused by the mosfet . The average current of primary inductor is obtained and there is no need to estimate the rising slope and the peak value of the inductor current. To verify the feasibility of the proposed method, a controller for charging application is fabricated integrated with the proposed method. Hardware experimental results show that the control system can properly operate in multimode. The accuracy of constant output current is ±1% and the line regulation of the system is 1.6% under the input line voltage ranges from 85 to 265 Vac.

An Energy-Based Analysis for High Voltage Low Power Flyback Converter Feeding Capacitive Load

Abstract: Generally, battery-fed capacitive loads are charged to high voltages in series of switching cycles with smaller fragments of energy delivered to the load in every cycle to ensure an efficient charging process. In high voltage low power (HVLP) flyback charging circuit, significant portion of input energy drawn from the source in a cycle is utilized by the effective parasitic capacitance of the HV transformer and semiconductor devices and circulated back to the source at the end of the cycle. This reduces the energy delivered to the load per cycle and hence the net energy delivered in the charging process. In this paper, an energy-based analysis and simplified energy-based model for HVLP charging circuits is derived. An energy-based approach is appropriate to describe and define the HVLP converter behavior in terms of load energy component and circulating energy component. The derived energy-based model is extended to obtain analytical closed-form expressions governing the essential parameters of the charging circuit. The proposed energy-based model and analytical formulation of essential parameters are experimentally validated on a 0–2.5 kV programmable high voltage charging circuit prototype fed from 12 V input battery source.

State Space Modeling and Stability Analysis of the Flyback Converter

Abstract: In this paper, state space and stability analysis are revalued to restructure with the published articles for the practical applications before implementation of the Flyback power converters. The design guidelines and optimizations are espoused in such a manner to heighten high power conversion ratio, transient response, tight regulations, compact dimension, robust reliability and high power density in the converter for the transportable applications

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

Abstract: 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.

Digitally controlled GaN-based MHz active clamp flyback converter with dynamic dead time optimisation for AC–DC adapter

Abstract: The active clamp flyback (ACF) converter utilising gallium nitride (GaN) devices with high-switching frequency and high efficiency is impressive in system miniaturisation for AC–DC adapters. Owing to poor reverse conduction of GaN devices, the improper dead time between two switches can cause large power consumption in high frequency. This study proposes a dynamic dead time optimisation technique for GaNs ideal zero-voltage switching (ZVS) to address the issue. It adjusts the clamp switch on time to avoid large reverse conduction voltage stress on the main switch in different loads conditions. In addition, a new control scheme for clamp switch is introduced for enhancing efficiency in light to medium load. These techniques are experimentally verified on a 45 W (20 V/2.25 A) prototype of an ACF converter with a field-programmable gate array. The controller enables the system to operate at 1 MHz and dynamically modulates the dead-time under universal input and full load. With the light load ZVS control scheme, the system can achieve a maximum efficiency of 94.12 and 80.23% in the worst case. The prototyped converter can achieve power density (exclude case and controller) of 18 W/in 3 .

Multitransformer Primary-Side Regulated Flyback Converter for Supplying Isolated IGBT and MOSFET Drivers

Abstract: This paper presents primary-side voltage regulated multitransformer quasi-resonant flyback converter (MTFC) for supplying isolated power switch drivers. The proposed topology offers distinct advantages over frequently used flyback converter possessing one high frequency transformer with isolated multiple outputs. Particularly, when a large number of separate dc supply units is required, then MTFC enables improved regular distribution of magnetic coupling between the common primary and the multiple secondary transformers’ windings providing a high degree of galvanic and electromagnetic isolation between multiple outputs. Primary side voltage regulation is based on the average output voltage estimation using auxiliary RDC circuit mounted across the primary windings. Operation principles of MTFC are enhanced with analytical study of cross regulation of multiple output voltages at unbalanced load conditions, indicating reduced voltage deviation of multiple outputs by applying the primary-side average voltage regulation. Experimental results of prototype 2-, 3-, and 6-transformer quasi-resonant flyback converters confirmed their cross regulation quality and application potential for independent multiple output supplies.