Abstract: Disclosed are a flyback switching power supply and a self-powered circuit and method therefor. The self-powered circuit includes: a charging capacitor configured to draw power from a primary coil and supply power to a switching power supply chip; a withstand voltage switch tube for acquiring a power supply voltage of the primary coil and outputting a charging voltage; a charging switch tube for controlling whether to charge the charging capacitor; an adjustment control tube for limiting the charging voltage of the charging capacitor; a voltage limiting control unit for controlling the conduction state of the adjustment control tube according to the charging voltage; a charging control unit preset with a charging requirement; and an inverter for acquiring the conduction switch signal and controlling the voltage limiting control unit or the charging control unit to be connected to the adjustment control tube according to the conduction switch signal.

Abstract: Disclosed are a switching power supply, a power replenishment circuit and a power replenishment method. The switching power supply replenishment circuit includes a control module configured to output a control signal for adjusting an output voltage of the switching power supply; a charging capacitor configured to store electric energy and power the control module; a withstand voltage switch tube configured to obtain a power supply voltage of the primary winding and output a charging voltage for charging the charging capacitor; a charging switch tube configured to control whether the charging capacitor is charged; a primary control loop configured to control whether the primary winding is turned on; a charging control unit configured to control whether the charging switch tube is turned on; the charging control unit including: a voltage sampling feedback device configured to detect a voltage signal of the auxiliary winding.

Abstract: The present application relates to a synchronous rectification sampling control circuit, method and chip. The control circuit includes a withstand voltage switch tube Q2, a power supply switch tube Q3, a positive phase power supply driving module, a detection control module, and a negative phase power supply module. The withstand voltage switch tube Q2 includes a withstand voltage source, a withstand voltage grid and a withstand voltage drain, in which the withstand voltage drain is configured to connect a secondary winding power supply circuit in a synchronous rectification circuit of a transformer to obtain a supply voltage and output a positive or negative sampling voltage at the withstand voltage source.

Abstract: The present application relates to a synchronous rectification sampling control circuit, method and chip. The control circuit includes a withstand voltage switch tube Q2, a power supply switch tube Q3, a positive phase power supply driving module, a detection control module, and a negative phase power supply module. The withstand voltage switch tube Q2 includes a withstand voltage source, a withstand voltage grid and a withstand voltage drain, in which the withstand voltage drain is configured to connect a secondary winding power supply circuit in a synchronous rectification circuit of a transformer to obtain a supply voltage and output a positive or negative sampling voltage at the withstand voltage source.