Switching power supply input voltage detection and power supply control circuit and method

The invention relates to the technical field of switching power supply chip control, and particularly discloses a switching power supply input voltage detection and power supply control circuit and method.The control circuit comprises a high-voltage switch, a current switching unit, a sampling and holding unit, two comparison units and an AND logic unit; one end of the current switching unit is connected with the high-voltage pin through the high-voltage switch, the other end of the current switching unit is connected with the power supply pin and the first comparison unit, the current switching unit comprises two current sources which are connected in parallel and a current limiting switch, and the current limiting switch is connected to one current source in series; the sampling and holding unit is respectively connected with the high-voltage pin, the current limiting switch and the second comparison unit, the two comparison units are both connected with the AND logic unit, and the AND logic unit is also co