Mobile power supply is a power product that can be carried by individuals, can store electrical energy by themselves, and can charge mobile devices, especially handheld devices (such as mobile phones, tablet computers, etc.). Mobile power is usually used in occasions where there is no external power supply. Its main components include batteries that store electrical energy, charge management circuit, discharge management circuit, etc. Typical products are DC 5V input and DC 5V output. The product structure of mobile power is relatively simple, mainly composed of three parts: storage medium, circuit board and shell. Among them, there are two types of storage media: polymer batteries and lithium batteries. At present, most mobile power supplies use lithium batteries, and among them, 18650 batteries dominate. The output voltage of a single 18650 cell is between 2.7-4.2V and the capacity is 2600m Ah. In order to increase the storage capacity of the mobile power supply, the method of connecting multiple battery cells in parallel is usually used, so the nominal capacity of the mobile power supply is generally a multiple of 2600mAh. The working voltage range of the battery of electronic digital products is also 2.7-4.2V. In order to be able to charge it, there must be a boost circuit inside the mobile power supply to increase the output voltage to 5V before discharging. Correspondingly, the charging voltage (i.e. input voltage) of the mobile power supply is also 5V, and DC charging is carried out through an external power adapter or a computer USB port
