A power supply circuit , comprising: a first regulator configured to generate a first output signal (VOUT1) according to an input signal (VIN), wherein a voltage value of the first output signal (VOUT1) starts increasing when the input signal (VIN) is equal to a first voltage threshold value (VTH1) in a power-on stage (P_ON) and the voltage value of the first output signal (VOUT1) starts deceasing when the input signal (VIN) is equal to the first voltage threshold value (VTH1) in a power-off stage (P_OFF); and a second regulator configured to be enabled according to the first output signal (VOUT1) to generate a second output signal (VOUT2) according to the input signal (VIN) when the first output voltage increases to a third voltage threshold value (VTH3), and wherein a voltage value of the second output signal (VOUT2) decreases according to the input signal (VIN) and a second voltage threshold value (VTH2) at the power-off stage (P_OFF), wherein the second voltage threshold value (VTH2) is greater than the first voltage threshold value (VTH1), wherein a maximum voltage value of the first output signal (VOUT1) is less than a maximum voltage value of the second output signal (VOUT2), wherein the second regulator is controlled to stop operating and the voltage value of the second output signal (VOUT2) is pulled down through a series connection of a transistor (M1) and a resistor (R1) if a voltage value of the input signal (VIN) is equal to or less than the second voltage threshold value (VTH2) in the power-off stage (P_OFF), wherein the second voltage threshold value (VTH2) is an under voltage lockout voltage of the second regulator . a first regulator configured to generate a first output signal (VOUT1) according to an input signal (VIN), wherein a voltage value of the first output signal (VOUT1) starts increasing when the input signal (VIN) is equal to a first voltage threshold value (VTH1) in a power-on stage (P_ON) and the voltage value of the first output signal (VOUT1) starts deceasing when the input signal (VIN) is equal to the first voltage threshold value (VTH1) in a power-off stage (P_OFF); and a second regulator configured to be enabled according to the first output signal (VOUT1) to generate a second output signal (VOUT2) according to the input signal (VIN) when the first output voltage increases to a third voltage threshold value (VTH3), and wherein a voltage value of the second output signal (VOUT2) decreases according to the input signal (VIN) and a second voltage threshold value (VTH2) at the power-off stage (P_OFF), wherein the second voltage threshold value (VTH2) is greater than the first voltage threshold value (VTH1), wherein a maximum voltage value of the first output signal (VOUT1) is less than a maximum voltage value of the second output signal (VOUT2), wherein the second regulator is controlled to stop operating and the voltage value of the second output signal (VOUT2) is pulled down through a series connection of a transistor (M1) and a resistor (R1) if a voltage value of the input signal (VIN) is equal to or less than the second voltage threshold value (VTH2) in the power-off stage (P_OFF), wherein the second voltage threshold value (VTH2) is an under voltage lockout voltage of the second regulator . <EOS>