 power supply input voltage detection circuit, the power supply converting an input voltage to an output voltage by a transformer which includes a primary winding and asecondary winding, wherein the primary winding is coupled to a power switch, which receives a switching signal to adjust the output voltage, the power switch being coupled to a sensing circuit, when the power switch turns ON, the sensing circuitgenerates a current sense signal according to current through the primary winding, the input voltage detection circuit comprising: a rising time detection circuit, which 