Disclosed are bias voltage generating circuits and methods for a switching power supply. In one embodiment, a switching power supply can include: (i) a driver circuit configured to receive a bias voltage, and to drive a switch in a power stage of the switching power supply; (ii) where a ratio of an output voltage of the switching power supply to an expected bias voltage of the driver circuit is configured as a proportionality coefficient; (iii) a bias voltage generating circuit configured to generate the bias voltage for the driver circuit based on a first voltage; and (iv) an H-shaped inductor coupled to an input of the bias voltage generating circuit, where the first voltage is configured to be generated based on a number of turns of the H-shaped inductor and the proportionality coefficient.