SOFT-SWITCHING DUAL-FLYBACK DC-DC CONVERTER WITH IMPROVED EFFICIENCY AND  REDUCED OUTPUT RIPPLE CURRENT

 

Abstract

This paper presents a soft-switching dual- flyback DC-DC converter with improved efficiency and reduced output ripple current. Zero-voltage-switching (ZVS) technique and a dual-flyback module for reducing the number of snubber current paths are adopted to improve efficiency. For ZVS technique, a self-driven synchronous rectifier (SR) is used instead of an output diode. By turning the self-driven SR off after a short delay, a main switch is turned on under the ZVS condition. For reducing the number of snubber current paths, a dual- flyback module and a snubber diode are used. When the main switch is turned off, leakage inductance energy is absorbed by a snubber diode into an input source and a primary DC-bus capacitor. Then, this energy is reprocessed by the dual- flyback DC-DC module to secondary side. Hence, there is only one snubber current path. In addition, the proposed converter features a reduced output ripple current because of the continuous current. Consequently, the proposed converter can achieve high efficiency and reduced output ripple current. To verify the performance of the proposed converter, operating principles, steady-state analyses, and experimental results from a 340 to 24-V, 100-W prototype are presented.

EXISTING  SYSTEM:

To overcome these problems, two-switch pulse-width modulated (PWM) flyback converters are introduced. By using two clamping diodes, switch voltage is clamped to input voltage and leakage inductance energy is recycled to input source. In addition, to achieve ZVS turn-on of the switch, an additional lossless snubber circuit is adopted. Another solution for recycling the leakage inductance energy is using an active snubber circuit , a half-bridge flyback converter is presented for satisfying both switch voltage clamping and ZVS operation. In, an adaptive snubber circuit is introduced to extend the parasitic output capacitance of the switch, and the converter is operated in the critical conduction mode (CRM) for near-ZVS operation. The operation in CRM minimizes the turn-on switching loss of the switch because the MOSFET turn-on occurs exactly in the valley of the drain-source voltage oscillation between a transformer inductor and a parasitic output capacitor of the switch. Nevertheless, there is a small switching loss in the switch since it is not a full-ZVS operation. Therefore, various soft-switching techniques are introduced for high efficiency. In addition, a synchronous rectifier (SR) is also introduced instead of a diode for reducing the conduction loss. Normally, there are three different kinds of SR driving strategies—voltage-driving strategy, current-driving strategy, and MOSFET drain-source voltage detection. By replacing a diode with a SR, efficiency is improved because turn-on voltage drop across the SR is much lower than diode forward voltage drop.

CONCLUSION

In this paper, a soft-switching dual-flyback DC-DC  converter was proposed. By replacing the output diode with an SR, the conduction loss was minimized. The ZVS operation of the main switch was achieved by turning the self-driven SR off, after a short delay. In addition, the reprocessed transformer leakage inductance energy was maximized because there was only one snubber current path. Moreover, its output ripple current was reduced owing to the continuous current. Consequently, the proposed converter satisfied both the high efficiency and reduced output ripple current conditions.

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