Discussion on Several Design Ideas of Mainstream Fast Charge Scheme

With the advent of the intelligent era, smart phones are indispensable in people's daily lives, but smart phones consume a lot of power, charging time is long and the batteries are lithium batteries. The battery is constantly charged and discharged, which will reduce the battery life. The battery life is a huge challenge. How to achieve fast battery charging is the key to solving the problem.
Keywords: fast charge fast charging technology


With the advent of the intelligent era, smart phones are indispensable in people's daily lives, but smart phones consume a lot of power, charging time is long and the batteries are lithium batteries. The battery is constantly charged and discharged, which will reduce the battery life. The battery's endurance has become a huge challenge. How to achieve fast charging of the battery has become the key to solving the problem. Since the French scientist Prandt invented the lead-acid battery for more than 100 years, the battery charging has been using a small current (about 0.1C). The constant current charging method limits the application of the battery due to the long charging time and low charging efficiency. In the mid-1960s, the American scientist Mamas proposed the basic law of battery fast charge - after Mas's law, the rapid charging of the battery began to receive great attention. For decades, people have charged the fast charging mode and stopped charging. The control method has carried out a lot of in-depth research and put forward a variety of practical methods.

(1) Continuous high current fast charging mode: Firstly, the mobile phone is quickly charged with continuous large current. When the battery voltage rises to the point where it is difficult to withstand the charging current, it is transferred to trickle charging until the battery is full.
(2) Charging current decrement fast charging mode: Usually also called charging current along the acceptable charging current curve fast charging mode, the charging curve is as shown.

The curve in the figure is the curve that Maast can accept the maximum charging current, and the broken line is the actual charging current curve. In the initial stage, in order to be as close as possible to the curve, first charge with a constant current close to the curve. When the battery can no longer accept such a large current, it will adjust the charging current to a relatively small value, and then use this constant The current is de-charged, and the cycle is repeated, along the curve that Maas can accept the maximum charging current until the battery is full. In principle, this charging method is relatively close to the maximum charging speed acceptable for the battery, but in practical applications at home and abroad, problems have arisen: First, this fast charging mechanism is difficult to design because of various types of batteries, The battery acceptable charging current curves vary from manufacturer to manufacturer, so it is difficult to be compatible. Second, this chemical material can easily cause polarization during charging, which is difficult to eliminate. , so the charging time is not as fast as ideal.

In recent years, mobile phone fast charging technology has been increasingly used and favored by mobile phone manufacturers. “Charging for five minutes, talking for two hours”, this classic line is the best slogan for fast charging. Now many of Android's flagship phones have fast charging technology, but Apple's mobile phone has not added this feature. However, some people worry that fast charging will damage the battery. So what is fast charging? Will fast charging damage the battery? Modern fast charging is a relatively general concept. It has three different implementation forms: (1) constant voltage, increasing current; (2) constant current, boosting voltage; (3) increasing voltage and current.

At present, there are two kinds of fast charging technologies in the true sense: one is flashing technology, and the other is Qualcomm's Quick Charge 2.0 technology. Both technologies require a combination of "charger and mobile phone" to achieve this, and the lack of one will affect the effect.

What is flashing technology?

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Flashing can be divided into two implementations: one is segmented charging current control. In short, in fact, when the battery power of the mobile phone is low, the charging is performed with a larger current. As the charging voltage increases, the charging current is gradually reduced. This is called segmented charge current control. This is like pouring water into the water polo. At the beginning, the water injection speed is fast, but the water polo is likely to blow up; the small water injection is safe but too slow. The solution is to start with a slow injection of water, then increase the water flow to accelerate, and then reduce the water flow when approaching the maximum capacity, which balances time and capacity. The other is the multi-line setting of the charging cable and the battery. The charging cable of the flash charging is expanded from the ordinary 4-pin or 5-pin to the 7-pin. For example, the speed is changed from two lanes to two lanes. In four lanes, the amount of charge will double in the same amount of time. This method effectively solves the problem of battery heating under continental current, but there will be compatibility problems, because the essence of the flash charge is mainly concentrated on the charger, so when using other chargers, the charging efficiency will be greatly reduced.

At the same time, if you use the flash charger to charge other mobile phones, because the mobile phone does not have the corresponding adaptation, the charging effect is just equivalent to the high current charging, and the effect is not good with the flash-fitted mobile phone. Therefore, the charger and the mobile phone can not be less. Qualcomm Quick Charge 2.0 fast charging, its core technology is to reduce the charging current by increasing the charger voltage, thereby reducing the power consumption on the charging line. There will be a corresponding step-down circuit on the mobile phone end, which will convert the high voltage and low current. It is a low pressure and high flow.
In essence, flash charging and Quick Charge 2.0 are the same, by supplying a large charging current to the mobile phone battery at the beginning of the battery, and gradually reducing the charging current as the battery voltage increases. The issue of time is an important issue that humans have always faced.

Constantly improving the efficiency of using time promotes human progress and development. From the "big brother" that only has the function of calling to the era of omnipotent smartphones, the functions of mobile phones have been greatly expanded and have also been greatly developed. Especially after entering the 4G era, the perfect mobile network and open source intelligent system have enabled the mobile phone application to obtain a round of explosive development and cover all aspects of life. Mobile entertainment includes listening to music, watching videos, playing games, online games, etc.; mobile interaction includes mobile Internet browsing news information, spatial information, Weibo, QQ, WeChat and other social chat software; mobile reading includes learning materials, mobile newspapers, Electronic fiction, etc. It can be said that mobile phone applications have become ubiquitous, involving the corners of life, and have become a must-have for generations of work and life.

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