Project introduction: 18650 boost 5V, maximum output current 800ma, enough in general application, use synchronous rectifier boost chip FP6276, output with LED indicator, with EN output control switch, this design is used to give me another open source project STC51 offline downloader is used for power supply. Circuit introduction: Red circle 1 is 18650 lithium battery mother seat and filter capacitor circuit. The red circle 2 is a 5V output EN output switch. When the four pins of the U1 chip are at high potential, they output 5V voltage, and when they are at low potential, the 5V output is turned off. Inside the red circle 3 is the boost power inductor. The red circle 4 is the feedback of the output voltage sampling due to the adjustment of the output voltage. The red circle 5 is the output indicator diode and the filter capacitor. The indicator diode is highlighted, so the current limiting resistance is relatively large.