DC-to-DC converter and converting method of discontinuous conduction mode

A DC-to-DC converting method of discontinuous conduction mode, comprising:

• making an inductor output an inductor current according to a DC input signal under an energy-storage state;
• making the inductor output the inductor current according to the DC input signal and a DC output signal under an energy-release state;
• determining whether the inductor current reaches a current threshold during the energy-release state and generate a current detection signal accordingly in which the current threshold is above zero;
• and
• if the inductor current reaches the current threshold, making a freewheel switch be conductive to form a current loop with the inductor so that the inductor current is allowed to circle in the current loop and the inductor current is maintained under an idle state.

A DC-to-DC converter of discontinuous conduction mode, comprising:

• a signal input end operable to receive a DC input signal;
• an output circuit operable to output a DC output signal;
• an inductor including an inductor input end coupled to the signal input end and an inductor output end coupled to the output circuit, operable to output an inductor current according to the DC input signal under an energy-storage state, output the inductor current according to the DC input signal and the DC output signal under an energy-release state, and maintain the inductor current under an idle state;
• a freewheel switch, coupled to the inductor input and output ends, operable to be conductive under the idle state and nonconductive under the energy-storage and energy-release states according to a freewheel control signal so that the freewheel switch and the inductor are operable to form a current loop under the idle state;
• a current sensing circuit operable to determine whether the inductor current reaches a current threshold and thereby generate a current detection signal in which the current threshold is above zero;
• and
• a control circuit, coupled to the signal output circuit, the freewheel switch and the current sensing circuit, operable to generate the freewheel control signal according to the current detection signal and control the change of states from one of the energy-storage state, the energy-release state and the idle state to another.