Highly integrated switching power supply and control circuit

A control circuit for a switching power supply system, wherein the switching power supply system comprises a transformer, the transformer comprises a primary winding, a secondary winding and an auxiliary winding, and the control circuit comprises:

• a power switch transistor, configured to control disconnection and conduction of the primary winding of the transformer;
• a primary current sampling module, configured to sample a current of the primary winding to generate a sampling voltage;
• and
• a voltage stabilization control module, configured to turn on or turn off the power switch transistor according to an input voltage, an output voltage of the switching power supply system, and the sampling voltage;
• wherein the voltage stabilization control module comprises a resistance adjusting module, and the resistance adjusting module comprises:
• a second feedback resistor module, comprising an RC filter circuit and a plurality of lower feedback resistors connected in parallel, wherein each of the plurality of lower feedback resistors is controlled by a resistance control switch;
• and
• a decoding and encoding module, configured to receive a resistance control signal and output a switch control signal to a plurality of resistance control switches to turn on or off all or part of the plurality of resistance control switches.