A power conversion device includes a power supply, a converter, a current detection circuit, and a control circuit. The power supply includes positive and negative terminals. The converter includes a primary side and a secondary side. The converter is configured to output a first current to a load. The primary side is electrically connected to the positive terminal and the negative terminal of the power supply in parallel. The secondary side is electrically connected to the positive terminal of the power supply and the load in series. The current detection circuit is coupled between the secondary side and the load, and is configured to detect the first current to output a current detection signal. The control circuit is coupled to the current detection circuit for outputting a control signal to the converter according to the current detection signal and a reference current signal.