Apparatus and method for limiting inrush current and extending hold-up time in an ac-dc power conversion apparatus

Abstract

An AC-DC power converter has a power factor correction stage that receives grid power and produces DC bus power. A DC-DC converter stage receives the DC bus power and produces a DC output power. Energy storage is provided by a larger capacitance value first capacitor and a smaller capacitance value second capacitor coupled in series across the DC bus power with a switching device coupled in parallel with the smaller second capacitor. During converter start-up, the switching device is turned off and inrush current is controlled by transferring energy from the second capacitor to the first capacitor. During operation the switching device is turned on and the first capacitor provides energy storage for the DC bus power. When grid power is disconnected, hold-up time is extended by turning the switching device off and transferring energy from the first capacitor to the second capacitor.