The principle is very simple, in fact, there is an MPU chip on the driver board, which is written in advance to control the duty cycle of the square wave output, in the specified time interval, each power supply, MPU chip output different duty cycle of the square wave, and drive the constant current circuit (or MOS tube) to achieve 3 or 5 gear transformation. The working principle of the flashlight is simple, that is, the battery → the lamp (now most of the LED lights)→ the switch three major structures