A new integrated high step‐up quasi‐resonant flyback‐forward converter

• Published in: International journal of circuit theory and applications Vol. 46; no. 10; pp. 1899 - 1916
• Main Authors: Salehi Dobakhshari, S., Taheri, M., Banaiemoghadam, Amin, Milimonfared, J., Fathi, S.H.
• Format: Journal Article
• Language: English
• Published: Bognor Regis Wiley Subscription Services, Inc 01.10.2018
• Subjects: Converters; Diodes; Electric potential; flyback‐forward converter; high step‐up converter; High voltages; PWM controlled quasi‐resonant converter; soft switching; Switches; Switching; Transformers; Voltage gain
• ISSN: 0098-9886; 1097-007X
• DOI: 10.1002/cta.2486

Summary This study presents a new high step‐up, high efficiency, flyback‐forward converter. The proposed converter employs 2 transformers, operating in flyback and forward modes at different intervals, to achieve the high voltage gain. In favor of high power density, transformers have been installed on 1 core. Furthermore, all switches are turned on under zero voltage switching condition, and all diodes are turned off under zero current switching condition. Also, the proposed converter utilizes resonant operation that leads to a reduction in switching loss, turning the converter to a highly efficient one. A 150‐W prototype has been implemented to verify the theoretical analysis, and a complete analysis has been done to investigate the effect of transformers integration. In this study, 2 flyback‐forward converters are implemented on 1 core in order to increase power density of the converter (Figure A). Furthermore, resonant mode operation has been adopted so as to reduce switching loss. As shown in Figure (B), switches turn‐off current (TOC) has been reduced efficiently. A comparison between conventional PWM and resonant mode has been presented in Figures (C) and (D). It can be clearly observed that TOC for the main switch has been almost halved. A thorough discussion has been conducted in the paper that confirms the claims.