A resonant inverter includes a first driver and a second driver for driving a first and second switching devices, respectively, a dead time generator for generating a first drive signal and a second drive signal respectively, a current-controlled oscillator for supplying, to the dead time generator, an output clock having a frequency determined based on a first current input to the current-controlled oscillator, and a current mirror for supplying the first current to the current-controlled oscillator in an amount proportional to a second current flowing through an external resistor. The current mirror includes a track/hold circuit, to supply the second current in an amount equal to an amount of the second current supplied before a variation in the amount of the second current, during a transition of an output signal between the first and second switching devices.