Abstract: A buck-type DC-to-DC converter and a method of operating the same are provided. The converter includes: an active switch electrically connected to an input power source having an input voltage; a diode having two terminals electrically connected to the active switch and the input power source, respectively; a resonant circuit connected in parallel with the diode and including a capacitor and a resonant inductor connected in series with the capacitor; and an output inductor electrically connected to the resonant circuit and connected in series with a load electrically connected to the resonant circuit. The active switch and the diode are switched in an on-state or an off-state according to different working modes. The active switch is switched from the off-state to the on-state by a switching voltage less than the input voltage. The diode is switched from the on-state to the off-state by a switching current equal to zero.