A method for controlling a resonance-type power converter, - wherein the resonance-type power converter includes an inverter comprising a resonant circuit (L 0, C 0, C S) and a rectifier connected to the inverter and is configured to convert power of a DC power source and to output a DC voltage of a predetermined target voltage, - wherein the method comprises: - when a switching frequency ( f s) of a switching element included in the inverter satisfies a following formula f r 1 < f s ′ by controlling at least either one of a switching frequency ( f s) of the switching element or a duty ratio indicating an ON period of the switching element, securing a delay time (T d) greater than zero from a voltage (Vds) - at both ends of the switching element having reached zero voltage by resonance of the resonant circuit (L 0, C 0, C s) in an OFF state of the switching element until the switching element is turned on, and - turning on the switching element within the delay time (T d), - wherein when the switching frequency ( f s) satisfies a following formula, f r 1 < f s < f r 2 ′ output power of the resonance-type power converter is reduced by stabilizing the duty ratio and raising the switching frequency ( f s), and - wherein when the switching frequency ( f s) satisfies a following formula, f r 2 ≤ f s ′ the output power is reduced by stabilizing the switching frequency ( f s) and reducing the duty ratio, and - wherein, f r1 represents a resonance frequency of the resonant circuit (L 0, C 0, C s) in an ON state of the switching element, f r2 represents a resonance frequency of the resonant circuit (L 0, C 0, C s) in the OFF state of the switching element, and f s represents a switching frequency ( f s) of the switching element. - wherein the resonance-type power converter includes an inverter comprising a resonant circuit (L 0, C 0, C S) and a rectifier connected to the inverter and is configured to convert power of a DC power source and to output a DC voltage of a predetermined target voltage, - wherein the method comprises: - when a switching frequency ( f s) of a switching element included in the inverter satisfies a following formula f r 1 < f s ′ by controlling at least either one of a switching frequency ( f s) of the switching element or a duty ratio indicating an ON period of the switching element, securing a delay time (T d) greater than zero from a voltage (Vds) - at both ends of the switching element having reached zero voltage by resonance of the resonant circuit (L 0, C 0, C s) in an OFF state of the switching element until the switching element is turned on, and - turning on the switching element within the delay time (T d), - when a switching frequency ( f s) of a switching element included in the inverter satisfies a following formula f r 1 < f s ′ by controlling at least either one of a switching frequency ( f s) of the switching element or a duty ratio indicating an ON period of the switching element, securing a delay time (T d) greater than zero from a voltage (Vds) - at both ends of the switching element having reached zero voltage by resonance of the resonant circuit (L 0, C 0, C s) in an OFF state of the switching element until the switching element is turned on, and - turning on the switching element within the delay time (T d), - wherein when the switching frequency ( f s) satisfies a following formula, f r 1 < f s < f r 2 ′ output power of the resonance-type power converter is reduced by stabilizing the duty ratio and raising the switching frequency ( f s), and - wherein when the switching frequency ( f s) satisfies a following formula, f r 2 ≤ f s ′ the output power is reduced by stabilizing the switching frequency ( f s) and reducing the duty ratio, and - wherein, f r1 represents a resonance frequency of the resonant circuit (L 0, C 0, C s) in an ON state of the switching element, f r2 represents a resonance frequency of the resonant circuit (L 0, C 0, C s) in the OFF state of the switching element, and f s represents a switching frequency ( f s) of the switching element.