First, the meaning of fast charge:
USB is widely used because it can power peripherals. USB was born in the mid-1990s, the original purpose is to external devices (such as keyboards, mice, printers, external drives, etc.)
Connect to your computer. As more and more portable devices are favored, they also need to be powered.
The ability to power from a data transfer connector gives USB a direct and significant advantage in the portable market. Before the first battery charging specification was promulgated in 2007, trying to charge the battery was essentially an adventure – the results were very unpredictable.
Until now, charging smart devices (including mobile phones, tablets, Bluetooth devices), etc., there is no unified mandatory standard introduced in the world, each manufacturer has its own definition, currently Apple, Samsung, and some of its domestic The Android machine is representative, and has its own defined charging specifications, which are incompatible with each other. With the increase of smart devices with large battery capacity, some devices have a capacitance capacity greater than 3000 mA/H, and some tablets have reached 10,000 mA/H or more. Mobile phones using Type-A and MicroA/B interfaces are limited by the USB 2.0 standard. The charging current is limited to 1.5A and the maximum current allowed by the interface is 1.8A. Each mobile phone manufacturer's custom data line can boost the current to 2A, but the loss will become very large when the current is greater than 2A. The charging efficiency is lowered and the charging time is prolonged.