Power supply circuit and driving method for display panel

A power supply circuit includes a comparison circuit, a preset value setting circuit, a reset detecting circuit and a reset signal generating circuit. The comparison circuit compares a first and second voltage to output a comparing result. The first and second voltages correspond to a first and second preset value, respectively. When the comparison result shows that the second voltage is greater than the first voltage, the preset value setting circuit outputs the second preset value; otherwise it outputs a third preset value, which is greater than the first preset value. The reset detecting circuit determines whether the operation voltage of the power supply circuit drops to the preset value outputted by the preset value setting circuit, and outputs a control signal accordingly. The reset signal generating circuit determines whether to output a reset signal for resetting gate lines in a display panel based on the control signal.