Power efficiency improvement at light load for POL power supply employing two stage coupled inductor converter

This paper proposes a new two-stage converter with a coupling capacitor and a coupled inductor. In order to downsize the two-stage converter, two inductors are tightly coupled together. Circuit operation is described in detail. Steady state analysis is performed and confirmed by experiments. It is clarified that the proposed converter has advantages of larger voltage conversion ratio and higher power efficiency in light load region than a single-stage converter and a conventional two-stage converter. It is also clarified that turns ratio of the coupled inductor must be unity for the safety operation.