A power converter having a feedback voltage adjusting mechanism for a negative voltage is provided. Input terminals of an operational amplifier are respectively connected to a zero voltage and a first terminal of a first resistor. A second terminal of the first resistor is connected to a second terminal of a low-side switch. A first current source is connected to an output terminal of the operational amplifier and a first terminal of a second resistor. A second terminal of the second resistor is connected to the first terminal of the first resistor. The first current source outputs a first current according to a signal output by the operational amplifier. A second current source outputs a second current being m times the first current and is connected to a first terminal of a third resistor. A voltage of the first terminal of the third resistor is a feedback voltage.