Power conversion circuit and control method thereof that switches between pulse-width modulation mode and pulse-frequency modulation mode

Abstract

A power conversion circuit includes a transformer, a resonant capacitor, a resonant inductor, a high-side transistor, a low-side transistor, and a control circuit. The transformer includes a primary coil and a secondary coil. The primary coil, the resonant capacitor, and the resonant inductor are connected in series between a switch node and a ground. The high-side transistor provides an input voltage to a switch node based on the high-side driving signal. The low-side transistor couples the switch node to the ground based on the low-side transistor. The control circuit operates in a pulse frequency modulation mode to generate the high-side transistor and the low-side transistor with a switch frequency. When the switch frequency exceeds the first threshold, the control circuit switches from the pulse frequency modulation mode to the pulse width modulation mode.

Dependencies are inferred from the claim text.