The power factor corrector 111b may include circuitry to adjust a power factor of the DC power input from the first rectifier 111a and output a DC voltage. The power factor corrector 111b may minimize and/or reduce reactive power by correcting a phase and shape of the DC power input from the first rectifier 111a. The power factor corrector 111b may output the DC voltage through a capacitor (or smoothing capacitor) connected to an output terminal.

The inverter 111c may generate power transmitted to the wireless power receiving device 120 by converting the DC voltage input from the power factor corrector 111b into an AC voltage. In addition, the inverter 111c may include a power amplifier amplifying the generated voltage.

In FIG. 5A, the inverter 111c may include a vertical switch in the form of a half bridge. The vertical switch may include, for example, a switching transistor (e.g., a MOSFET). In this case, a duty ratio of the inverter 111c may be adjusted under the control of the first controller 117. The duty ratio may refer, for example, to a ratio between a turn-off period and a turn-on period of the switching transistor. For example, the duty ratio may be a turn-on period/turn-off period or a turn-on period/(turn-on period+turn-off period).