Power conversion device and pre-charging method thereof

A pre-charging method of a power conversion device, comprising:

• pre-charging, by a pre-charging circuit of the power conversion device, a first flying capacitor of a power converter of the power conversion device during a power-on transient period of the power conversion device;
• sensing, by a sensing circuit of the power conversion device, a terminal voltage difference of the first flying capacitor to generate a sensing result to the pre-charging circuit;
• stopping, by the pre-charging circuit, the pre-charging of the first flying capacitor of the power converter based on the sensing result;
• and
• converting, by the power converter, a first direct current (DC) voltage into a second DC voltage for a load circuit during a normal operation period after the power-on transient period.

A power conversion device, comprising:

• a power converter converting an input voltage to an output voltage and comprising a flying capacitor;
• a sensing circuit coupled to the flying capacitor and sensing a voltage across the flying capacitor;
• and
• a pre-charging circuit coupled to the power converter, wherein when the voltage across the flying capacitor is less than a reference voltage, the pre-charging circuit charges the flying capacitor.