Wireless power transmitter and method for wirelessly transmitting power

A wireless power transmitter comprising:

• a converter comprising switching elements forming a bridge circuit, wherein the converter is configured to output alternating current (AC) voltage comprising an amplitude determined according to an operating duty cycle of at least one switching element among the switching elements, and a frequency determined according to an operating frequency of the at least one switching element;
• a resonator comprising an inductor and a capacitor, and configured to receive the AC voltage to wirelessly transmit power;
• and
• a controller configured to output control signals controlling the switching elements so that the converter performs one of a first mode operation in which the operating duty cycle is fixed and the operating frequency is varied, and a second mode operation in which the operating frequency is fixed and the operating duty cycle is varied, in response to a change in the operating frequency,
• wherein the bridge circuit comprises half-bridge circuit comprising a first switch and a second switch connected to each other in series and alternately operated, and
• wherein the converter comprises
• an inductor comprising a first inductor terminal connected to a first source terminal of an input power source, and a second inductor terminal connected to a connection terminal between the first and second switches, and
• an output capacitor comprising a first output capacitor terminal connected to one terminal of the half-bridge circuit, and a second output capacitor terminal connected to a second source terminal of the input power source and another terminal of the half-bridge circuit.