A power conversion apparatus including a power converter, a first output port, a second output port, a load detection circuit and an output selection circuit is provided. The power converter generates a first and a second output voltages having different voltage specification. The first and the second output ports respectively provide the received output voltages to a back end. The load detection circuit is coupled with the power converter and the second output port and detects a load requirement of a load connected to the second output port to generate a load detection signal. The power converter generates a first switch control signal according to the load detection signal to control the output selection circuit, such that the output selection circuit provides one of the first and the second output voltages in response to the first switch control signal.