CONTROL METHOD AND CONTROL CIRCUIT FOR BUCK CONVERTER

The present invention relates to the technical field of switch power supplies. Disclosed are a control method and control circuit for a BUCK converter. The control method is mainly used for solving the problem of a low efficiency in a DCM operating mode due to it being difficult for a main power switch tube to achieve a ZVS caused by the insufficiency of a negative current provided by a power inductor in the DCM operating mode. The control method is mainly implemented by means of a digital control scheme. The method comprises: an inductor current sampling circuit detecting a zero-crossing signal of a current of an inductor, and sending the zero-crossing signal to a DSP; the DSP receiving the zero-crossing signal, and performing counting; when a count value n ≥ 2, the DSP sending a synchronous rectifier tube switching-on signal, such that a synchronous rectifier tube is switched on; an output capacitor reversely charging a power inductor, such that a negative current of the inductor is increased; and when the