A power supply circuit with a plurality of stages (120, 150) for converting a first voltage to a second voltage where the first voltage is greater than the second voltage, wherein each stage (120, 150) of the power supply circuit comprises: a first circuit block (1, 2, 3, 4) configured to provide a start-up power to a second circuit block; the second circuit block configured to generate a Pulse-Width-Modulation signal that controls a pulse duration of a transistor (109, 159) connected to a primary winding (112, 162) of a transformer, the transistor (109, 159) configured to cause a current to flow from an input of the stage (120, 150) through the transistor (109, 159) and the primary winding (112, 162); a third circuit block (108, 158) configured to activate or deactivate the transistor (109, 159) based on the PWM signal; a fourth circuit block configured to reset a magnetic flux in the transformer to a zero state when the transistor (109, 159) is deactivated; and a fifth circuit block comprising a transformer feedback winding (111, 161) coupled to the second control block, the fifth circuit block configured to maintain an output of the stage (120, 150) below a predetermined value by adjusting a voltage across the transformer; characterised in that the first circuit block (1, 2, 3, 4) comprises: a first diode (104, 154) electrically connected with a first terminal to a resistor (102, 152) and a first capacitor (103, 165), wherein the resistor (102, 152) and the first capacitor (103, 165) are connected to an input of the stage (120, 150); and a second diode (105,155) electrically connected with a first terminal to a second terminal of the first diode (104, 154) and a second capacitor (106, 156) and with a second terminal to the fifth circuit block, wherein the first diode (104, 154) and the second diode (105, 155) are configured to maintain a voltage across a third capacitor (115, Cfdb) included in the fifth circuit block greater than a voltage across the first capacitor (103, 165) when a power supply in the stage (120, 150) is above a predetermined threshold. a first circuit block (1, 2, 3, 4) configured to provide a start-up power to a second circuit block; the second circuit block configured to generate a Pulse-Width-Modulation signal that controls a pulse duration of a transistor (109, 159) connected to a primary winding (112, 162) of a transformer, the transistor (109, 159) configured to cause a current to flow from an input of the stage (120, 150) through the transistor (109, 159) and the primary winding (112, 162); a third circuit block (108, 158) configured to activate or deactivate the transistor (109, 159) based on the PWM signal; a fourth circuit block configured to reset a magnetic flux in the transformer to a zero state when the transistor (109, 159) is deactivated; and a fifth circuit block comprising a transformer feedback winding (111, 161) coupled to the second control block, the fifth circuit block configured to maintain an output of the stage (120, 150) below a predetermined value by adjusting a voltage across the transformer; characterised in that the first circuit block (1, 2, 3, 4) comprises: a first diode (104, 154) electrically connected with a first terminal to a resistor (102, 152) and a first capacitor (103, 165), wherein the resistor (102, 152) and the first capacitor (103, 165) are connected to an input of the stage (120, 150); and a second diode (105,155) electrically connected with a first terminal to a second terminal of the first diode (104, 154) and a second capacitor (106, 156) and with a second terminal to the fifth circuit block, wherein the first diode (104, 154) and the second diode (105, 155) are configured to maintain a voltage across a third capacitor (115, Cfdb) included in the fifth circuit block greater than a voltage across the first capacitor (103, 165) when a power supply in the stage (120, 150) is above a predetermined threshold. a first diode (104, 154) electrically connected with a first terminal to a resistor (102, 152) and a first capacitor (103, 165), wherein the resistor (102, 152) and the first capacitor (103, 165) are connected to an input of the stage (120, 150); and a second diode (105,155) electrically connected with a first terminal to a second terminal of the first diode (104, 154) and a second capacitor (106, 156) and with a second terminal to the fifth circuit block, wherein the first diode (104, 154) and the second diode (105, 155) are configured to maintain a voltage across a third capacitor (115, Cfdb) included in the fifth circuit block greater than a voltage across the first capacitor (103, 165) when a power supply in the stage (120, 150) is above a predetermined threshold.