Embodiments of the present invention disclose a power supply conversion apparatus, where a control unit generates a corresponding control signal according to a received high level pulse width modulation signal, to control a first PMOS transistor Q3, a second PMOS transistor Q4, and a second NMOS transistor Q2 to be turned off successively, and then to make a first NMOS transistor Q1 conducted, which makes a voltage at a second end of a bootstrap capacitor to rise from ground potential to a PVDD, so that a voltage at a first end of the bootstrap capacitor rises to a PVDD+AVDD as the voltage at the second end rises, and a gate turn-on voltage of the first NMOS transistor Q1 reaches the PVDD+AVDD.