Switching regulator and control method thereof

A switching regulator, comprising:

• a power stage circuit, which is configured to operably control at least one power switch according to a pulse width modulation (PWM) signal, to switch an inductor coupled to a phase node, thus converting an input voltage to an output voltage;
• a control circuit, which is configured to operably generate the PWM signal according to an operation clock signal;
• and
• an operation clock signal generator circuit, which is configured to operably generate the operation clock signal, wherein the operation clock signal generator circuit includes:
• a time point option unit, which is configured to operably generate a time point option signal according to a phase node voltage of the phase node during a ringing period subsequent to a blanking period, to indicate at least one available turn-on time point, or which is configured to operably generate a lowest voltage time point signal according to the phase node voltage during a tolerance period, to indicate a lowest voltage time point;
• and
• a time point deciding unit, which is configured to operably decide the tolerance period according to a base clock signal and a tolerable frequency range and which is configured to operably select the available turn-on time point or the lowest voltage time point which occurs within the tolerance period to be a decided time point, so as to generate the operation clock signal;
• wherein the decided time point is a time point which corresponds to a lowest phase node voltage within the tolerance period or an ending time point of the tolerance period;
• wherein a beginning time point of the tolerance period is a time point obtained by counting a shortest tolerance period from a previous decided time point, wherein the shortest tolerance period corresponds to a highest frequency of the tolerable frequency range;
• wherein an ending time point of the tolerance period is a time point obtained by counting a longest tolerance period from a previous decided time point, wherein the longest tolerance period corresponds to a lowest frequency of the tolerable frequency range;
• wherein the ringing period occurs during a dead time when the switching regulator operates in a discontinuous conduction mode (DCM).