Although there are so many fast charging technologies, there are only two mainstream ones. Currently, Qualcomm Quick Charge fast charging technology is mainly used for high voltage and low current. Qualcomm’s fast charging solution is integrated in the chip, so the high-voltage and low-current fast charging of QC is basically the use of Qualcomm processors. There are many low-voltage and high-current technologies, such as OPPO, HUAWEI, etc. What are the advantages of low voltage high current and high voltage low current?
Under the formula of P=UI, in order to increase the charging power P, one solution is to increase the voltage U, and the other solution is to increase the current I. In fact, whether it is high voltage and low current or low voltage and high current, it is all to increase the power. The 9V2A charging of the QC scheme adopted by Xiaomi, or the 5V5A charging of VOOC. However, both options have their advantages and disadvantages. Due to some physical characteristics in the charging process of lithium-ion polymer batteries, the advantage of VOOC’s low-voltage high-current fast charging solution is that the battery temperature rises during charging is small, and the temperature is better controlled. QC’s high-voltage and low-current fast charging solution will cause the temperature to rise a little faster in comparison.
Excessive temperature will have a certain impact on the life of lithium-ion polymer batteries used in smartphones, and there will also be certain safety risks. Internationally, there are requirements for the temperature of the battery during charging and discharging. When the temperature is too high or too low, the charging current needs to be reduced, and the discharge must be stopped when it exceeds 60 degrees Celsius. Therefore, Xiaomi Mi 6 using the high-voltage low-current fast charging solution can charge with the highest power when you turn off the battery to charge.
However, when the user lights up the screen during the charging process, does more operations or even plays games while charging, in order to avoid the hidden danger caused by the overheating of the mobile phone, the charging power will be actively reduced. Obviously, this is a self-protection system setting. Moreover, it is not just Xiaomi phones that have such settings. Samsung’s latest flagship S8, the same will have the following situation:
The charging current data of Samsung S8:
Off-screen charging: about 10W
Off-screen charging and calling: about 5.1W
Bright screen to play games: about 4.2W.
Power may vary with ambient temperature.
High voltage and low current go through two voltage conversions, one at the charging head and one at the interface. Low voltage and high current only need one voltage conversion. At the charging head, if you touch your charging head and mobile phone, you will find that the low voltage At high current, only the charging head is hot, and the mobile phone is not very hot, but both high voltage and low current are hot.
What is the difference between different fast charging technologies?
High-voltage and low-current charging
Relatively speaking, the body is hot during high-voltage and low-current charging, and when using the high-voltage fast charging solution, the charging current and voltage are often reduced when the screen of the mobile phone is on for safety reasons, reducing the charging power, so the current when the screen is on is bright. It will be slower, which is why most manufacturers do not support flash charging on the bright screen or flash charging while playing. However, the advantage of high-voltage fast charging is that it does not require much wire and has good compatibility. When your mobile phone is out of power or low in power, you can use a general high-power charging head for fast charging. The disadvantage is that if the mobile phone needs to be charged and the mobile phone is also turned on to play games or something, in order to reduce heat generation, the charging power will be reduced, and it cannot be charged so quickly at the same time.
Low-voltage and high-current
The low-voltage and high-current fast charging has good heat control, and the battery pressure is small, but the problem is that it is very troublesome, not universal, and additional costs are added. When you play your phone and play games while charging, you can also maintain the power of fast charging and replenish the power as soon as possible. But the downside is that you need to match a custom charging cable with an identification chip.
Different fast charging technologies have their own advantages and disadvantages. For consumers, fast charging with fast charging speed, low temperature and high efficiency is the best, and iQOO’s vivo Super FlashCharge provides an exploration direction. Low voltage and high current may be more popular in the future.