Circuit and buck converter

The utility model relates to a circuit and a buck converter. In an embodiment, a method for soft start SMPS includes: enabling an enable signal to take effect; disabling an output stage of the SMPS; measuring a feedback voltage of the SMPS after the enable signal takes effect; receiving a first reference voltage at the input reference node; comparing the measured feedback voltage with a first reference voltage; and when the measured feedback voltage is lower than the first reference voltage, outputting the feedback voltage. A feedback voltage is stored in a soft start capacitor, an output reference node is connected to the soft start capacitor, an output stage of the SMPS is enabled, a transistor of the output stage is switched to adjust the output voltage based on the feedback voltage anda second reference voltage at the output reference node, and a current is injected into the soft start capacitor. Thus, the SMPS power-on is realized under the condition of saving energy. 本申请涉及电路和降压转换器。在实施例中，用于软启动SMPS的方法包括：使