DC/DC refers to a device that converts a DC power supply of a certain voltage level into a DC power supply of another voltage level. DC/DC is divided into two types according to the voltage level transformation relationship: boost power supply and buck power supply, and isolated power supply and non isolated power supply according to the input output relationship. For example, in mobile phone application circuits, it is often necessary to drive the LED of the flash module or the LED of the display backlight through a boost circuit, and it is usually possible to adjust the brightness of the LED according to the needs of different situations.