Charin, Chanuri
(2013)
Novel Soft Switching Isolated Dc-Dc Converters
Topologies.
Masters thesis, Universiti Sains Malaysia.
Abstract
DC-DC converters are widely used in many applications such as power
supplies, PV system, renewable energy systems and industrial applications. One of the
main problems in dc-dc converters is the switching loss which affects efficiency and
also the power density of the converter. To alleviate the switching loss problem this
thesis proposes novel soft switching PWM isolated dc-dc converters topologies. Three
topologies of dc-dc converters are presented in this thesis. These are half-bridge dc-dc
converter with auxiliary circuit, full-bridge dc-dc converter with multilevel inverter
leg and full-bridge dc-dc converter with auxiliary circuit. The proposed half bridge dcdc
converter with auxiliary circuit is designed and tested both with diode bridge
rectifier and centre-tapped transformer rectifier. The proposed converters are designed
and evaluated in term of soft switching. Soft switching operations are achieved by
charging and discharging process of the flying capacitor. In proposed topologies, all
the power switches operate under soft-switching conditions. Therefore, overall
switching loss of the power switches is greatly reduced. The output voltages of the
converters are varied by PWM control. The effectiveness of the new converters
topologies is evaluated both by simulation and experimental results of a laboratory
scale down prototype. The obtained experimental results are found in good agreement
with the simulation results. The proposed half-bridge dc-dc converter with auxiliary
circuit and centre-tapped transformer rectifier has highest efficiency among all the
proposed topologies. Its efficiency is 81% at the output power of 25W, so it is
considered best among all the proposed topologies.
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