Investigation of SEPIC converter in critical DCM

SEPIC converter operated in critical discontinuous conduction mode or boundary conduction mode (BCM) is investigated. In this paper, switch turn on is initiated when the output diode current falls to zero, when the output diode turns off, difference between the inductor currents flows through, switch parasitic capacitance and voltage across the switch drops, which ensures Zero voltage switching (ZVS). ZVS improved the efficiency. While turn-off switching process is established when the peak transistor current reaches the threshold level set by the controller output. This paper explains operating principles of BCM mode and design of power components. Prototype is designed and experimental results are provided.