A DC-DC converter (500, 700), comprising: a controller (510, 710), configured to generate an up signal and a down signal according to an output signal (Vout) and a ripple signal (V_RIPP); a first switch, coupled between an input voltage and a first node, and controlled by the up signal; a second switch, coupled between the first node and a reference voltage, and controlled by the down signal; an inductor, coupled between the first node and an output node (Nout), configured to receive a first signal from the first node to generate the output signal at the output node; and a ripple signal generator (520, 720, 900), configured to generate the ripple signal, and reset the ripple signal every cycle to a specific voltage (V_spe); wherein the ripple signal generator (520, 720, 900) comprises two circuit groups (R7, C7, SW7, SW7'; R8, C8, SW8, SW8') and a control signal generator (910, 920, 930, 940), wherein further the two circuit groups are configured to generate the ripple signal (V_RIPP) and reset the ripple signal (V_RIPP) to the specific voltage in an interleaving manner, wherein the ripple signal generator (520, 720, 900) is configured to generate the ripple signal (V_RIPP) based on a signal capable of representing a signal at the first node or an inductor current of the inductor, and the control signal generator is configured to generate control signals (PH1, PH1B, PH2, PH2B) for control switches (SW7, SW7', SW8, SW8') in each of the two circuit groups, so that the first circuit group is configured to generate the ripple signal (V_RIPP) while the second circuit group is reset, and the second circuit group is configured to generate the ripple signal (V_RlPP) while the first circuit group is reset. a controller (510, 710), configured to generate an up signal and a down signal according to an output signal (Vout) and a ripple signal (V_RIPP); a first switch, coupled between an input voltage and a first node, and controlled by the up signal; a second switch, coupled between the first node and a reference voltage, and controlled by the down signal; an inductor, coupled between the first node and an output node (Nout), configured to receive a first signal from the first node to generate the output signal at the output node; and a ripple signal generator (520, 720, 900), configured to generate the ripple signal, and reset the ripple signal every cycle to a specific voltage (V_spe); wherein the ripple signal generator (520, 720, 900) comprises two circuit groups (R7, C7, SW7, SW7'; R8, C8, SW8, SW8') and a control signal generator (910, 920, 930, 940), wherein further the two circuit groups are configured to generate the ripple signal (V_RIPP) and reset the ripple signal (V_RIPP) to the specific voltage in an interleaving manner, wherein the ripple signal generator (520, 720, 900) is configured to generate the ripple signal (V_RIPP) based on a signal capable of representing a signal at the first node or an inductor current of the inductor, and the control signal generator is configured to generate control signals (PH1, PH1B, PH2, PH2B) for control switches (SW7, SW7', SW8, SW8') in each of the two circuit groups, so that the first circuit group is configured to generate the ripple signal (V_RIPP) while the second circuit group is reset, and the second circuit group is configured to generate the ripple signal (V_RlPP) while the first circuit group is reset.