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Abstract: Switching power supplies utilizing isolated dc-dc converter are seeing increased use to power today’s consumer electronics and home appliances. However, for all the benefits of dc-dc converters such as efficiency, problems still exist with their use. One issue relates to leakage inductance of transformer used in the isolated dc-dc converters, which is often seen as one of the major contributors to degradation in performance. Leakage inductance’s role in circuit losses, changes in load regulation, and noise created by the given converter has been widely known. However, its direct impact on the operating duty cycle of the converter has not been investigated. This paper aims to examine the impact of leakage inductance to duty cycle in two popular isolated topologies, namely the single-switch forward and the flyback converters. The study used computer simulation to observe the effect of worsening the leakage inductance through transformer’s coupling coefficient. Results from computer simulation reveal a nearly linear relationship between leakage inductance and duty cycle. Under the given simulation parameters, the change in duty cycle reaches as much as 12.8% for the single-switch forward converter and 6.8% for the flyback converter.

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