In the current smart phone market, fast charging is no longer a new word, and high-power fast charging is gradually becoming popular.
Xiaomi, OPPO, vivo, and Huawei have all realized wired fast charging with a power of more than 60W, which can be fully charged in about half an hour. The mobile phone is fully charged and goodbye to the long wait. Starting in mid-2020, high-power fast charging of more than 100W entered the market, shortening the charging time to more than ten minutes. With the advent of high-power wireless fast charging, fast charging is no longer forced to be bound to cables.
Xiaomi is one of the manufacturers that have made the most efforts to promote the advancement of charging technology in recent years. The higher charging efficiency 33W fast charge, single cell 5000mAh battery, 67W fast charge down to 1000 yuan mobile phone, the first batch of 120W wired fast charge, the first 67W wireless fast charging, all appear on the Xiaomi mobile phone products we can buy. Regardless of domestic and international, the charging experience of this manufacturer has always been at the forefront.
Now, Xiaomi has brought 200W wired fast charging and 120W wireless fast charging, which can charge the display power of the mobile phone from 0% to 100% in 8 minutes and 15 minutes, respectively. After another big improvement, what efforts did Xiaomi make? How to ensure safety and experience? When will it be officially launched? Lei Technology and Xiaomi charging technology R&D engineers conducted an in-depth interview, and the answer gradually surfaced.
I want speed and safety
We have been advocating the safe use of electricity, which is closely related to our lives and property. The increase from 120W to 200W and compression from 15 minutes to 8 minutes seems to be just a digital change, but in order to ensure good heat dissipation performance and electrical stability, there is a complete set of chargers, cables, ports, motherboards, and batteries behind it. System changes.
The engineer confidently stated that this set of 200W charging technology developed by Xiaomi is definitely safe.
First, it has undergone a long R&D cycle for verification. The entire system from the charger to the mobile phone motherboard has up to 40 active safety protection measures, involving temperature, voltage, current, and protocols. Secondly, there is an independent MCU on the main board to control the charging status, and the fast charging will be cut off quickly if an abnormality occurs. The interface introduces corrosion-resistant rhodium-ruthenium alloy, and there is also an over-temperature protection detection circuit.
Xiaomi has also customized a new type of graphene-based design battery with a discharge rate of 10C for 200W fast charging. For the first time, it uses fast ion ring anode graphite to realize the characteristics of protecting the battery’s safe and fast charging. In order to achieve the Xiaomi 11 Pro-level thin and light body, the customized chemical system has been optimized on the pole piece to achieve a balance between energy density and volume and weight. There are other technical means to supplement the mobile phone.
As for the durability of this battery, engineers said that it has more stable positive and negative electrodes, the electrolyte is also specially designed, and the material protection is “extreme.” At present, it has 80% life after 800 cycles, so it has good endurance after long-term use. The research and development team is still improving production technology and mobile phone power consumption algorithms to further improve battery life.
It’s not just the motherboard that changes on the side of the phone. This time, Xiaomi used three parallel charge pumps scattered on the main board and small board to achieve a balance of charging efficiency and heat dissipation. The underlying algorithm was optimized accordingly, coupled with the use of the entire heat dissipation system, the standard charging speed can reach about 10 to 15 minutes. The 200W somatosensory temperature will remain at a level equivalent to 120W, except for faster and no other changes.
Going up to the cable and interface, the standard charging cable for 200W charging has been upgraded from the previous 120W 6A specification to 10A, and at the same time it has a lower resistance and is not easy to generate heat. The rhodium ruthenium plating used in the Type-C interface is safe, and the current specification has been increased from the previous 10A to 15A, and the anti-wear and anti-oxidation performance has been improved. In other words, it can maintain a better experience after long-term use.
The power has nearly doubled, but the volume of Xiaomi’s 200W fast charging charger has not changed significantly. This is also inseparable from the gallium nitride technology that has been popular in high-end mobile phone chargers in the past two years: the internal switching frequency of the charger is higher than 120W At the same time, the size of the energy storage device can be much smaller, and the winding transformer is replaced with a smaller planar transformer, which improves the efficiency and makes room for heat dissipation.
Will high-power mobile phone chargers trip the more restrictive school dormitories? Regarding this slightly nonsensical but indeed related to student user experience, the engineers also gave a “reassurance”: the peak power of the charger is 200W, which does not reach the 2000W threshold set by most schools for tripping, and the charging speed is fast and rarely takes longer. Time takes up too much power.
When will 200W charging, which requires both safety and speed, officially enter the market? The engineer said frankly that he can look forward to it. The previous 120W went through the process of first exposure in February 2019 and listing in August 2020. It took about a year or so. I believe that 200W will not make consumers wait too long.
Not just the charging technology itself
In areas other than charging technology, we have also seen a series of investments made by Xiaomi to improve the charging speed and experience of mobile phones.
Cost-effective “Global Pass” charger
As mentioned above, Xiaomi uses a large number of new charger components to achieve 200W charging, but engineers believe that it can still be “more cost-effective”: the entire set of technologies are all independent research and development, and the early development stage carries out cost control from BOM selection to materials. Automation is being implemented from process to process, which can control costs and improve consistency. At present, the automation rate has reached 85% and the target for this year is 90%.
The global market is an important part of Xiaomi’s sales growth. Therefore, it has made better international standards compatibility and supports 100V~240V wide voltage. The matching charging head of Xiaomi 11 has passed certification in more than 30 countries. Of course, there are different in different regions. Plug shape. The engineer proudly stated that Xiaomi has provided a 20V gear starting from the 33W version, so that the notebook can also be supplemented with a mobile phone charger.
Another value lies in the compatibility between different brands. Although it is not the most mainstream C to C fast charging but a modification of the USB-A interface, Xiaomi also supports PD, PPS, these general protocols, which can turn on 18W or higher fast charging, but For safety, the power of third-party products will be controlled. The converged fast charging agreement promoted by the state has progressed on May 28, and the fast charging compatibility of mobile phones will be better in the future.
200W is far from the end
Xiaomi has no less investment in wireless fast charging than wired fast charging. This 120W wireless fast charging uses a new multi-strand winding for the wireless coil, and also optimizes the nanocrystalline shielding material, and continues the 67W wireless charging time The introduction of Xiaomi’s unique 30V architecture improves efficiency. However, the recently published drafts of wireless charging regulations have begun to make people worry about whether technological progress will be limited.
Engineers believe that it is a good thing that wireless charging technology is standardized, which can urge third-party accessories to improve quality, improve safety and user experience. At the same time, the draft is still being solicited at this stage. The Ministry of Industry and Information Technology is communicating with companies such as Xiaomi and Huawei to discuss what kind of power is a more suitable upper limit. After the policy is implemented, Xiaomi will comply with the requirements.
Based on the opinions of many companies in the industry, all parties believe that no more than 200W is the upper limit standard for wireless charging technology. The engineer personally said that compared to limiting the total power, limiting the radiation amount of wireless charging equipment is a more effective means of achieving safety and other purposes. From the engineer’s point of view, the exploration of technology will not stop.
Back to wired fast charging, the technical upper limit is being refreshed again. In the past May, USB-IF released a draft technical specification for PD fast charging that can reach 240W power. Therefore, including chips, batteries and chargers, data cables, and interfaces, there are more prospects for mobile phone charging to explore. Engineers also believe that the cell phone battery rate is expected to be more than 10C.
All wireless phones are coming?
When it comes to Xiaomi’s technology investment, the engineer is quite proud. Charging-related teams have been spread across Xiaomi’s four R&D centers in Beijing, Shanghai, Nanjing, and Shenzhen, involving the heat dissipation of the motherboard baseband battery structure, etc. In mid-2017, the teams were selected to form an expert group and then began to work hard in 2018. The wireless charging has made the most progress. From MIX2S’s 7.5W to today’s 80W and 120W.
He also said that Xiaomi has made a lot of technical reserves to “fight the future.” The air charging demonstrated before is a very cutting-edge technology. Xiaomi has achieved a technical demo at this stage, and its complexity is not comparable to the current wireless charging. Engineers believe that there needs to be an ecosystem that can be wirelessly charged anytime and anywhere, so that wireless charging can replace wired, but in the next one or two years, there may be officially listed mobile phones without charging ports.
The popularization of fast charging becomes a new direction for the industry
Charge pumps, dual cells, gallium nitride… The advancement of charging technology is actually not less than that of other parts of the mobile phone, and it can even be said that a revolution has been quietly completed. Brushing your teeth and washing your face, a light meal, or even a game of time can fill the large-capacity battery and greatly alleviate the battery life anxiety caused by the high-intensity use of the mobile phone. It is still a technological advancement that every ordinary person can enjoy.
Xiaomi has gone further, but from the actual products, other manufacturers may achieve a similar experience within a few months, and the whole industry seems to be back on the same starting line. Next is the time to test endurance. How to provide fast charging of mobile phones to the public in a continuous, stable and equal manner will be an important link in the competitiveness of the entire product line of each brand.
Redmi Note 10 Pro puts 67W fast charge and 5000mAh battery directly from the high-end to the thousand-yuan level, which means that charging and battery technology must be advanced on the premise of not taking up more of the total cost. Grasping the balance will become another parallel way for manufacturers to explore the limit. In 2021, Xiaomi mobile phones will take into account the charging experience while being thin and light, which has made many people have a deep understanding.
After the charging time enters within ten minutes, how fast can the wired charging of the mobile phone be? How can wireless charging bring about an improvement beyond speed? We can wait for more good shows to be staged.
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