The Xiaomi 12 family will bring many innovative new features in the screen, camera and now charging technology. A Surge is not a new name, Xiaomi's first SoC came out with this name, then its own secondary graphics chip and now a charge controller. But why is it a world first? This is why!
From the 2019 release of Xiaomi's first-generation fast charging models to the Xiaomi MIX 4 120W fast charging system, wired fast charging speeds have increased 7.4 times and wireless fast charging speeds have increased 12 times. With the included charger, it now takes only 15 minutes to fully charge. As a result, many users have completely changed their overnight charging habits to on-the-go charging. In a real sense, a qualitative change in the charging experience has been achieved.
To achieve this goal, Xiaomi has identified fast charging as an important strategic direction for 2019. It has established four large R&D centres and set up a TMG charging technical committee. In three years, it has equipped hundreds of millions of devices with fast charging systems and applied for more than 800 patents.
“At the beginning of the next decade, we need to ask ourselves whether the fast-charging system should continue to follow the speed of the times or whether it should take a new direction.”
120 W single cell solution, the biggest common divider of fast charging, battery life, lightness and thinness.
Fast charging is a systematic project that involves dimensions such as lifetime, safety and battery life. If you blindly follow a charging time limit, you will compromise on other aspects.
At present, smartphones with up to 120 W wired charging speeds all use a two-cell system. The price of high speed is a reduction in the phone's internal space utilisation: the space available for cells is swapped. More complex charging circuits and dual cells. With the same volume occupied by the structure, the capacity of a dual cell battery is about 4% less. In addition, a 2:1 chip is required to discharge the dual cell during discharge and its own conversion efficiency leads to an energy waste of 3-4%. A single-cell charging system can circumvent the above problems, but getting the charging power above 100 W is a huge challenge.
That's the goal of the Xiaomi Surge's second charging system: to achieve the best balance between battery life and charging performance, and a single-cell 120W wired second charge.
The Surging P1 fills the gap in the 120 W single-cell fast charger industry
In the older single-cell fast charging system, a series-parallel circuit of 5 different charging pumps is required to convert the 20V input voltage of a mobile phone to 5V chargeable voltage in the battery. The large number of charge pumps and the overall series construction will generate a lot of heat. In actual use, it is impossible to run at full power for long periods of time and even harder to achieve the 120W high power fast charging, which is unacceptable for Xiaomi.
To redesign the entire charging architecture, the function of the fast charging chip needs to be redefined. At the core of Xiaomi's 120 W Surge second charging is two Xiaomi proprietary smart charging chips: the Surge P1. They take the complex architecture of the traditional 5 charge pump and convert the high-voltage power input to the mobile phone into high current that can be charged more efficiently directly to the battery.
As the industry's first resonant charging chip, Surge P1 features an ultra-high efficiency 4:1 adaptive switching frequency architecture. Resonant topology efficiency reaches 97.5%, non-resonant topology efficiency 96.8% and heat loss is reduced by 30%.
Surge P1 itself undertakes a lot of conversion work. Conventional charge pumps only need two modes (transform, transfer), while the Surge P1 needs to support 1:1, 2:1 and 4:1 conversion modes and all modes. It must also support dual conduction, which means a total of 15 permutations and mode change control combinations - seven times more than conventional charge pumps. The first 1:1 mode makes charging a bright screen more efficient, the first 2:1 mode is compatible with multiple chargers, the first 4:1 supports 120W Surge second charge, and the reverse 1:2/1:4 mode is available Supports high-power reverse charging.
4:1 charging chip with the highest charging efficiency and heaviest design
The Surge P1 is also the 4:1 charging chip with Xiaomi's highest charging efficiency, achieving an ultra-high power density of 0.83 W/mm² and LDMOS achieves the industry-leading ultra-low RSP charge of 1.18 mΩmm². The Surge P1 chip requires three FLY capacitors with different voltage resistances. Each capacitor requires independent open-circuit and short-circuit protection circuitry, and each mode of operation requires tight regulation of the precharge voltage and a number of power supply tubes approaching two. And thanks to the topology design and functional complexity, each P1 booster must pass more than 2,500 tests before leaving the factory, a much higher number than a conventional charge pump.
“The chip has finally allowed us to greatly simplify the circuit, but the ultra-high efficiency of the Surge P1 means that heat generation is within the ideal range, it can maintain full power operation for longer periods and it supports wireless charging.”
The soon-to-be-released Xiaomi 12 Pro is the first smartphone equipped with Surge P1 technology to support 120W wired charging, 50W wireless charging and 10W wireless reverse charging. Thanks to its single-cell high-power design, it can withstand a full day of use.
On the road to fast charging, Xiaomi is already far ahead of other manufacturers, bringing fast charging technology to the forefront with its own in-house developed fast charging chips, a year ahead of the fast charging technology on its products. We'll have more good news to share with you at the press conference on 28 December, so stay tuned.
