① Pin (GND) : ground end of the power circuit and the control circuit.
② Foot (FB) : feedback input end. After sampling the output voltage of the switching power supply, add it to this end, compare and amplify it with the internal reference voltage in the error amplifier, and add the output error signal to the internal PWM latch to adjust the output voltage.
③ Pin (VIN) : Start voltage input end. By connecting a high-resistance resistor to the output of the bridge rectifier, the starter device enters operation and this voltage is sampled to produce line voltage compensation.
④ Foot (RI) : refer to the setting end. The internal oscillation frequency sets the pin, and the resistance value of the external resistor determines the operating frequency of the chip.
⑤ Foot (RT) : temperature detection end. The external thermistor constitutes the overheat protection circuit.
⑥ Foot (SENSE) : current detection end. The MOSFET drain source (S pole) is connected to form an overcurrent protection circuit.
⑦ Pin (VDD) : power end.
Pin 8 (GATE) : Drives the output end and directly drives the MOSFET gate (G pole).