Quasi-resonant Flyback Research Articles

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

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.

Analysis, design and performance evaluation of an LED driver with unity power factor and constant-current primary sensing regulation

This work focuses on an isolated offline driver to power LED lamps, realized with a high-power-factor quasi-resonant (Hi-PF QR) flyback converter with peak current mode control and employing constant-current primary-sensing regulation (CC-PSR). The converter is controlled with a recently introduced control technique that enables this kind of converter to ideally draw a sinusoidal current from the input source and, at the same time, to accurately regulate the dc output current using only quantities available on the primary side. The resulting absence of an optocoupler or other means crossing the isolation barrier to close a feedback loop not only reduces size and cost of the driver but also brings greater safety and reliability. The analysis addresses those factors inherent in the control method that affect the shape of the input current that have not been covered in the existing literature. The aim is to set up some design guidelines to minimize the Total Harmonic Distortion (THD) of the input current. The experimental work shows that using this technique enables the design of an LED driver for wide range mains (90 to 264 Vac) that achieves output current regulation better than ±2%, power factor close to unity and THD of the input current <10% over the input voltage range and over a 2:1 range of the output voltage.

Inner Supply Data Transmission in Quasi-Resonant Flyback Converters for Li-Ion Battery Applications Using Multiplexing Mode

This paper proposes data transmission method between primary and secondary of the flyback converter without additional communication circuit while simultaneously transferring power. In some application such as a battery charger, the data exchanges between the primary and secondary sides are necessary. In the conventional system, an additional line or wireless communication modules is used for data exchanges, thereby increasing the system and connector size. The proposed system, in comparison, does not use additional signal transceiver but instead exchanges data by simply alternating operation mode of the flyback converter, thus adding communication function while not increasing the volume of the terminal and overall system. The waveform of transformer voltage is used to count the number of resonant pulses, which is used for decoding and encoding the data packet. Bidirectional communication between primary and secondary sides is possible while power is transferred to the output using an appropriate communication protocol. This paper proposes data transmission method for both single output and the multioutput cases. Also, both half-duplex and full-duplex communication using the proposed method is explained. The experimental results are presented to verify the performance of the proposed communication method.

Development of a modular single-phase grid-tie inverter system for fuel-cell power generation

To enhance the conversion efficiency and electrical reliability of the low-voltage fuel-cell (FC) power generation system, this paper proposes a modular single-phase grid-tie inverter system equipped with a power management and remote monitoring interface. In this system, each single power module is composed of three single-stage quasi-resonant (QR) flyback current-source inverters that are connected in parallel, and all the power modules are connected in parallel to achieve flexible power scaling and load sharing. The proposed grid-tie inverter system possesses a power management unit (PMU) and can be integrated with a home energy management system (HEMS). An experiment was conducted to verify the feasibility of the proposed concept, in which five power modules were assembled to form a 1-kW high-efficiency grid-tie inverter system, which was modulated through the PMU. The results showed satisfactory load-sharing characteristics between the parallel-connected power modules. The peak efficiency for each power module and the overall power generation system are about 94.5 and 90%, respectively. The proposed system exhibits flexible power scaling, load sharing, and high reliability.

A High-Switching-Frequency Flyback Converter in Resonant Mode

The demand of miniaturization of power systems has accelerated the research on high-switching-frequency power converters. A flyback converter in resonant mode that features low switching losses, less transformer losses, and low switching noise at high switching frequency is investigated in this paper as an alternative to a conventional quasi-resonant (QR) flyback topology to increase power density. In order to find a compromise between magnet size, electromagnetic interference (EMI), and efficiency, the concept utilizes the resonant behavior between transformer leakage inductance and snubber capacitor to achieve near-zero-voltage switching at both turn-on and turn-off of the primary switch, low core loss due to a continuous transformer magnetizing current, and reduced EMI due to low di / dt and dv / dt values. Meanwhile, the concept uses the regenerative snubber to recycle the transformer leakage energy with two snubber diodes and one snubber capacitor. The proposed concept has been validated on a 340-kHz 65-W prototype. Compared to the conventional QR flyback converter operating at the same switching frequency, the proposed concept has 2% efficiency improvement and better EMI performance.

A Study on the New Active Clamp Snubber Applied Quasi Resonant Flyback Converter

In this paper, active clamp snubber method was proposed to reduce effectively the switching surge voltage of the conventional quasi resonant(QR) flyback converter. The usefulness and practicality of the proposed method in QR flyback converter were verified through steady state analysis and its experimental results. The performance of the proposed circuit was compared with the RCD snubber method. It was verified from the experimental results that the switch peak voltage of the proposed method was limited below 5% while the switch peak voltage of the RCD snubber was continuously increasing accordingly with the load current. Furthermore, this new active clamp snubber method could be applied to QR flyback and its power conversion efficiency was superior to the RCD snubber one.

Novel Frequency Swapping Technique for Conducted Electromagnetic Interference Suppression in Power Converter Applications

Quasi-resonant flyback (QRF) converters have been widely applied as the main circuit topology in power converters because of their low cost and high efficiency. Conventional QRF converters tend to generate higher average conducted electromagnetic interference (EMI) in the low-frequency domain due to the switching noise generated by power switches, resulting in the fact they can exceed the EMI standards of the European Standard 55022 Class-B emission requirements. The presented paper develops a novel frequency swapping control method that spreads spectral energy to reduce the amplitude of sub-harmonics, thereby lowering average conducted EMI in the low-frequency domain. The proposed method is implemented in a control chip, which requires no extra circuit components and adds zero cost. The proposed control method is verified using a 24 W QRF converter. Experimental results reveals that conducted EMI has been reduced by approximately 13.24 dBμV at 498 kHz compared with a control method without the novel frequency swapping technique. Thus, the proposed method can effectively improve the flyback system to easily meet the CISPR 22/EN55022 standards.

광범위 입력전압을 갖는 준공진형 플라이백 파워서플라이의 연구

One of the many problems besetting the converter designer is being able to design a switching power supply that can operate in the range of very wide input voltage. Specially, in an emergency diesel generator system, the AVR(Automatic Voltage Regulator) is a regulator which regulates the output voltage of the generator at a nominal constant voltage level. In addition, the AVR must be operated in very wide input voltage. Therefore, a power supply for the AVR must be operated at the very wide input voltage range. In this paper, a quasi-resonant flyback power supply with very wide input voltage range is proposed. Also, the performance of the proposed power supply is demonstrated through experiments.

Single Power-Conversion LED Backlight Driving System With High Power Factor Control

A single power-conversion LED backlight driving system with high power factor control is proposed. The proposed converter is composed of a full-bridge diode rectifier and a quasi-resonant flyback converter. The proposed converter provides a simple structure, a low cost, and high power factor of 0.988 by using the novel control algorithm without the PFC circuit. To achieve good controllability, the novel control algorithm is transformed by adding a nominal value predetermined to relax its control burden. Detailed analysis and experimental results for a 90-W prototype are discussed.

Design Considerations for Dual-Output Quasi-Resonant Flyback LED Driver With Current-Sharing Transformer

In this paper, a quasi-resonant (QR) flyback dual-output LED driver with current-sharing transformer (CST) is analyzed thoroughly. Although the CST is utilized to balance the currents in two LED strings, from the theoretical analysis, it shows that the parasitic capacitance of CST and its magnetizing inductance have a significant effect on the output current deviation and diode's voltage stress. In order to achieve the optimal current sharing ability between two outputs with minimum auxiliary components, a design guideline for the CST in QR flyback is proposed according to the theoretical analysis. A 100-W dual-output dc-dc prototype is built up to verify the theoretical analysis.

Design of Dimmable Quasi-Resonant Fly Back LED Driver Based on OZ9992

The paper designs a 30W dimmable constant current LED driver. It is designed by O2Micros OZ9992 control chip, and it use quasi-resonant flyback topology. It can achieve zero voltage to reduce switching losses. The LED driver has higher efficiency and can provide a stable current for LED lamps. It has good dimming performance, and is easy to operate. It is suitable for home, hotel and other occasions, and has broad application prospects.

Quasi-Resonant Flyback DC/DC Converter Using GaN Power Transistors

Quasi-resonant flyback converter is realized with the aim to demonstrate the topology feasibility using the normally-on switching behaviour of the gallium nitride (GaN) power transistor. Reference converters utilize GaN and silicon-based MOSET as the switching devices to compare the electric characteristics, and power losses. Quasi-resonant technology offers reduced turn-on losses, resulting in increased efficiency and lower device temperature. The turn-on losses dominate the power losses as the switching frequency of the power supply increases. The combined advantages of gate charge and on-resistance for GaN in the 60 watt reference converter leads to improve the turn-off conduction loss. GaN based power converter provides up to 7.02% improved efficiency over silicon based MOSFETs. The converter performance improvement opens the possibility of fully exploiting the wide advantages of GaN transistors in power electronic application.

A single-stage quasi-resonant flyback converter using a synchronous rectifier

A single-stage quasi-resonant flyback converter using the synchronous rectifier (SR) is proposed for improving power factor and system efficiency. This converter operates at the critical conduction mode with the variable frequency (VF) control to reduce the switching loss of the primary switch. The bulk capacitor voltage can be independent of the output load and kept within a practical range for the universal line input. Therefore, the problem of high-voltage stress across the bulk capacitor is reduced. The proposed converter features relatively low bulk capacitor voltage in the universal line voltage and also complies with the Standard IEC 61000-3-2 Class D limits. Moreover, since it uses the voltage-driven SR, it achieves a high efficiency. The operational principle and theoretical analysis are presented. Experimental results for a 100 W (19 V/5.3 A) adapter at the VF were obtained to show the performance of the proposed converter.

An Adaptive Blanking Time Control Scheme for an Audible Noise-Free Quasi-Resonant Flyback Converter

The quasi-resonant (QR) control scheme is widely adopted in a Flyback converter to maximize its efficiency by reducing the switching loss. The switching frequency increases with decreasing load or increasing input voltage. In order to limit electromagnetic interference noise and improve light load efficiency, the maximum switching frequency should be limited. However, the maximum switching frequency limitation adopted in QR control will cause audible noise due to the frequency hopping phenomena at certain load and input condition, which is related to the intrinsic output characteristic of the control scheme. This paper presents a simple solution to eliminate the frequency hopping in the QR Flyback using an adaptive blanking time circuit. The proposed method changes the blanking time automatically to keep the output characteristic smooth that eliminates the audible noise in the transformer. The detailed operation principle and design considerations are presented. The experimental results from a 16 V/4 A prototype are provided to validate the effectiveness of the proposed solution.

Study on a Novel Single-Stage QR PFC Converter

A novel quasi-resonant single-stage single-switch PFC flyback converter is analyzed. By the additional winding, power factor correction can be achieved, and the topology can be simplified. The circuit can work in quasi-resonant mode, so the switching loss is reduced. By means of digital frequency reduction, the efficiency of the converter is improved further.

Single-Stage Quasi-Resonant Flyback Converter for a Cost-Effective PDP Sustain Power Module

A single-stage quasi-resonant flyback converter is proposed for a cost-effective plasma display panel (PDP) sustain power module. The proposed converter operates at the boundary of the continuous- and discontinuous-conduction modes to reduce the switching loss of the primary switch. The bulk capacitor voltage can be independent of the output load and maintained within a practical range for the universal line input. By integrating two power conversion stages into one, the proposed converter provides a simple structure and high efficiency for the PDP sustain power module. The operational principle and theoretical analysis are presented. A prototype converter was built and tested for a 32-in PDP, which requires 150-W (180-V/0.83-A) sustain power. The experimental results verify the feasibility of the proposed scheme.

Charge-Equalization Circuit for Series-Connected Batteries with Quasi-Resonant Flyback Converters

A charge equalization circuit for balance discharging in a series-connected battery bank is proposed in this paper. The circuit comprises several parallel-connected flyback converters which connect each unit battery in the bank to supply the electric load. The transformer leakage inductance and capacitances of MOSFETs are applied to fulfill the quasi-resonant zero voltage switching (ZVS), which consequently eliminates the voltage spikes and enhance the conversion efficiency. Design equations are derived and numerical analysis results are applied to evaluate the required values of the inductance and capacitance to realize ZVS performance. A battery bank with four series-connected lead-acid batteries is used to verify the proposed charge equalization circuit. The experimental results advocate the applicability of the proposal.

Half-wave quasi-resonant flyback converter using a GTO

Resonant power supplies incorporating an inverter in which the semiconductor switches maintain sinusoidal oscillation in an LC network can offer very high efficiencies. Furthermore, electromagnetic interference, radio frequency interference and mains borne pollution are much reduced compared with square wave switching. Unfortunately a higher voltage rated switch is required which is capable of the high frequencies required and low loss. The recently developed high speed Gate Turn-Off thyristor could provide a viable solution to the above requirements. This paper outlines the design and construction of a half-wave quasi-resonant flyback converter using a GTO at a nominal maximum operating frequency of 60 kHz. The power supply has an output of 500 watts at 60 volts. A full description is given of the circuit analysis, the design procedure used and results of a computer simulation of the prototype design using the computer simulation package PSPICE. Practical waveforms are given illustrating the operation of the circuit and emphasis is placed on the voltage and current of the switching device and the input current taken from the supply.

Computer simulation of a high-frequency zero-current switching quasi-resonant flyback converter

A computer-based analysis of a zero-current switching quasi-resonant flyback converter employing a gate turn-off (GTO) thyristor as the switching device is described. Included in this is a two-transistor computer model for the GTO. Practical results obtained from a laboratory model of a 10 W converter are compared with the simulated results. An analysis of a 1 kW off-line converter model is then presented and the practical aspects of implementing such a system are described.