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

An apparatus comprising:

• a power factor correction stage configured to receive an alternating (AC) input voltage and to produce a direct current (DC) correction stage output signal over a power bus comprising a positive output node and a negative output node;
• a DC-to-DC conversion stage coupled to receive the DC correction stage output signal to produce a DC output power (Vu);
• a first capacitor C1 coupled in series with a second capacitor C2 between the positive output node and a negative output node, wherein a first central node is disposed between the first capacitor and the second capacitor;
• a first switching device coupled in parallel with the second capacitor;
• and
• an energy transfer unit coupled to the positive output node and the negative output node and to the first central node, the energy transfer unit being configured to control the first switching device to turn on and off to transfer energy between the first capacitor and the second capacitor,
• wherein a capacitance value of the first capacitor is greater than a capacitance value of the second capacitor;
• and
• when the AC input voltage is disconnected or not present, the energy transfer unit is configured to turn off the first switching device and increase a hold up time by transferring energy from the first capacitor to the second capacitor.