Xiaomi explains how the Xiaomi Mi 9 20W wireless charging works

A few days ago, Chinese manufacturing giant, Xiaomi, release its latest flagship smartphone, Xiaomi Mi 9 which comes with a 20W wireless flash charging. This smartphone is the world's first smartphone to support up to 20W wireless flash charging. You can charge 40% in 30 minutes, and you can fill the entire phone in about an hour and a half. Xiaomi said that it achieved the first 20W wireless charging with same half-voltage direct charge solution as the wired fast charge by using charge pump technology.

Charge pump technology is a high-voltage charging and high-current solution. It is a DC-DC converter that uses capacitors as energy storage components for voltage conversion and conversion efficiency. The maximum output power of the Xiaomi Mi 9 20W wireless charging base is about 20W, allowing the mobile terminal to input at 15V/1.34A.

The intermediate stage uses 95% high-efficiency DC-DC (buck) to step down to 2x the battery voltage. It can also achieve 20mV fine voltage regulation to ensure the stability of the next-stage charge pump charging. According to the company, the intermediate conversion efficiency is as high as 97%-98%.

The 20W wireless fast charge of the Xiaomi Mi 9 is faster than the wired 18W charge of the Xiaomi Mi 8. Looking at three mainstream flagship charging, Xiaomi Mi 9 gives 100% charge in 90 minutes while Huawei Mate 20 Pro needs 124 minutes for a full charge while iPhone XS Max uses 257 minutes for a full charge.