Conventional Flyback Converter Research Articles

A New Standby Structure Using Multi-Output Full-Bridge Converter Integrating Flyback Converter

This paper presents a new standby structure where the standby flyback converter is integrated with the zero-voltage-switching multi-output full-bridge dc-dc converter. While the standby power is generated from the conventional flyback converter in standby mode, the auxiliary output of the multi-output full-bridge converter is used for the standby output in normal mode. The validity of this proposed structure is confirmed by the experimental results from 12 V/58 A for the dc-dc output and 5 V/3.2 A for the standby output prototype.

EMI Analysis and Evaluation of an Improved ZCT Flyback Converter

Switching power supplies are sources of noise for sensitive circuits. Converters should comply with electromagnetic compatibility (EMC) rules so that the electromagnetic interference (EMI) caused by switching cannot interfere with the normal operation of adjacent circuits and also the converter itself. The produced interference can be in the form of conduction or radiation. In this paper, some techniques are used in switching converters to suppress EMI with emphasis on the conduction form. EMI analysis and evaluation of a conventional flyback converter and a proposed zero-current transition (ZCT) flyback converter is achieved by simulation and experimental results. In addition to evaluating some EMI suppression techniques, the main objective of this paper is to improve EMI in the topology design stage. The operating modes of the improved ZCT flyback are discussed. In addition to the efficiency improvement, the amount of EMI reduction of this ZCT flyback and the effectiveness of some EMI reduction techniques are shown by practical implementation.

Analysis and implementation of an active-clamping zero-voltage turn-on switching/zero-current turn-off switching converter

A new isolated dc/dc converter with zero-voltage turn-on switching (ZVS) of power switches and zero-current turn-off switching (ZCS) of diodes is presented. In conventional flyback converters, the main drawbacks are high voltage stresses on power devices, large transformer size and serious reverse recovery current, which resulted in high voltage spikes across output diode. To solve these problems, a buck-boost type of active-clamp circuit is connected in parallel with the primary winding to clamp the voltage spike across the power switch, to recycle the energy stored in the leakage and magnetising inductances of the transformer and to realise the turn-on ZVS by utilising the leakage inductance and output capacitance of the switch. The leakage inductance and the resonant capacitance on the secondary side are resonant to allow the output diodes to turn off at ZCS. Thus, the switching losses and thermal stresses of switches and diodes are reduced, the output diode has no reverse recovery problem and voltage stresses of the output diodes are clamped to the output voltage. Experiments conducted on a laboratory prototype rated at 270 W are provided to verify the effectiveness of the proposed converter.

A novel current resonant ZVS-PWM half-bridge converter

A novel zero-voltage-switched pulse-width-modulated (ZVS-PWM) half-bridge converter that achieves ZVS for switches and zero-current switching (ZCS) for rectifier diodes is developed with low-voltage-stress half-bridge topology. This converter has excellent features that include highly efficient power conversion at high switching frequency and low noise. In this paper, the basic operation and ZVS and ZCS conditions are analyzed and verified experimentally. Predominant features at the points of efficiency and the noise are verified by the comparison with conventional current resonant ZVS-PWM flyback converter. © 1998 Scripta Technica, Electron Comm Jpn Pt 1, 82(4): 45–55, 1999