Cycle-by-cycle Reverse Current Limiting in Actively Clamped Flyback Converters with Noncomplementary Control

Actively-clamped flyback (ACF) converters were first introduced more than 30 years ago but were little used in industry for a long time. They have recently regained attention as a solution to the demand for higher power density AC-DC adapters/chargers for portable equipment such as laptops and tablet PCs. Noncomplementary control, an alternative to the traditional complementary control that emerged about a decade ago, has improved ACF's performance by reducing power loss caused by reverse current conduction during the off time of the main power switch. However, this new control has also introduced some issues related to converter operation in the case of a short circuit at the output. These issues have not been highlighted in the existing literature, but the technique proposed in this paper solves them with just a little extra complexity and requiring very few additional external parts.