A bridgeless power factor improvement converter is configured with input terminals for an AC voltage, output terminals from for a DC output voltage, diodes, first through fourth switches, and coils. A control circuit selectively switches the first through fourth switches according to the AC voltage, a first dead time period (the third switch OFF/the fourth switch ON) in which the first and second switches are in a dead time including a zero-cross point from a positive period to a negative period, and a second dead time period (the third switch ON/the fourth switch OFF) in which the first and second switches are in the dead time including the zero-cross point from the negative period to the positive period. The control circuit maintains the third and fourth switches in the OFF state during a period other than the first and second dead periods.