In a power supply voltage converting circuit using a charge pump circuit having a switch device (Nch MOS transistor Qn(12) and Pch MOS transistor Qp(12)) in an output unit, a first clamp circuit (13) diode-clamps a switching pulse voltage (control pulse voltage) for the switch device at the time of starting the power supply voltage converting circuit, and a second clamp circuit (16) clamps the switching pulse voltage at a ground level (negative side circuit power supply potential) on the basis of a clamp pulse obtained by using an output voltage Vout at the time of an end of the starting process. A sufficient driving voltage is thereby provided for the Pch MOS transistor Qp(12) in particular. Thus, a power supply voltage converting circuit that can obtain a high current capacity on a small-area circuit scale, a control method thereof, a display apparatus having the power supply voltage converting circuit as a power supply circuit, and a portable terminal having the display apparatus are provided.