Disclosed are flip-chip package structures and methods for an integrated switching power supply. In one embodiment, a flip-chip package structure can include: (i) a die with an integrated switching power supply, where a first surface of the die includes first bumps with different polarities; (ii) a redistribution layer including redistribution layer units, each having a first surface to connect bumps with a same polarity from the first bumps, the redistribution layer having a second surface including second bumps to redistribute polarities; (iii) a lead frame having pins, where a first surface of the lead frame can connect bumps with a same polarity from the second bumps; and (iv) a flip-chip package configured to package the die, the redistribution layer, the first and second bumps, and the lead frame, where a second surface of the lead frame provides electrical connectivity between the integrated switching power supply and a PCB.