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The best EOS solution for mobile phone charging terminal VBUS and Vbattery2019/12/04

 

In the modern era, mobile phones are the most frequently used electronics in the world. Quality and performance are especially important to the user experience for its large usage. Under the popularization of smart phones, frequent charging has become a habit of users. In addition, most mobile phones now have a fast charging function, which is easy to cause EOS damage during high-power charging process and results in internal damage for normal usage then seriously affecting user experience.

 

Mobile phone charging technology needs

In recent years, the development of mobile phones has grown by leaps and bounds, richer applications, larger screens, higher resolution, and more powerful performance have made it play an increasingly important role in communication functions, social, working and entertainment fields. When facing such multi tasks, the endurance of battery for most smart phone has become a problem.

 

With its integration, nondetachable battery and poor battery technology, fast charging technology came into being. This will shorten charging time greatly and effectively enhances user experience.

 

Fast charging technology categories

At present, the mainstream fast charging technology includes QC charger, USB-PD and various mobile phone manufacturers fast charging technology, such as Huawei Supercharge, VIVO dual engine fast charge, OPPO VOOC and Xiaomi Super Turbo. Regardless of the fast charging technology, the principle is to increase the charging voltage or current to increase the charging power to achieve the fast charging function.

  

OPPO SuperVOOC flash charge VOOC3.0 uses low voltage and high current + new constant voltage charging algorithm and 3C cell and VFC fast charging algorithm. The 3C battery current carrying capacity is improved by 100%, VFC algorithm improves trickle charge. The concept of dual cell series connection enables charging power up to 50W.

  

Huawei Super Charge utilizes charge pump technology. The 40W super charge technology breaks the limitation of Type-C 5A by using the charge pump, and sends the power into the mobile phone through the 4A channel. After entering Type-C, the charging voltage is reduced to about 5V by the charge pump and current is boosted from 4A to 8A, and the battery is charged through this principle which achieves a 5V/8A low-voltage, high-current solution.

 

EOS hazard of mobile phone charging terminal

No matter which fast charging technology, its power is constantly increasing, from 18W to 50W, and the charger output voltage is increased from 5V to 9V/10V/12V or even higher. There are a large number of mobile phone users around the world. Due to the complicated and diverse charging environment, the general 5V/1A conventional charging is extremely vulnerable to EOS damage. In addition, the replacement charger and the charging wire in market are difficult for identification. Many of the power grid voltages in developing country have occasional unstable factors which makes EOS generation during the charging process. While the high-power fast charging process involves high-voltage, high-current and more device modules, EOS fluctuations are likely to be larger and more frequent. If the mobile phone charging terminal does not have an effective EOS protection solution, the back-end PMU, OVP and other ICs may be damaged and cause malfunction to mobile phones.

 

EOS protection solution of charging terminal

Since establishment of AMAZING Microelectronic Corp., we have hundreds of patents in the EOS/ESD field, focusing on EOS/ESD protection our technology has been approved by major manufacturers. The EOS protection of the charging terminal meets testing requirements of major mobile phone manufacturers. The highest protection standard reaches EOS 450V (8/20μs, 2ohm). As shown in figure 1 (a) which is a simplified diagram of charging port circuit of mobile phone. For the Vbus protection solution, TVS1 can be added to DC in (close to the interface, at the front end of OVP), and the Vbattery protection scheme adds TVS2 to the PMU positive pole and at the PMU side. To apply the characteristics of the DC high-voltage output while avoiding the low-voltage pulse damaging TVS, OVP which can withstand and absorb DC energy is used. Therefore, the first level TVS1 (as shown in figure 1 (b)) provides over Ipp 100A ROS protection by using 15V or 18V Surge TVS: AZ4715-01F/AZ4718-01F. The TVS2 uses the 5V Surge TVS: AZ3205-01F to provide Ipp 100A EOS protection as a second level of protection to absorb back-end EOS residual voltage. Practical and effective two-level TVS protection will greatly reduce repair rate of the mobile phone charging terminal and improve the quality of mobile phones.

 

EOS application solution overview

For the charging terminal of the mobile phone, our EOS protection scheme combines the charging principle of the mobile phone, and does not affect the normal charging function and signal transmission. It can cope with frequent plugging and charging as well as complicated use environment to protect mobile phones from EOS damage, and greatly reduce mobile phone failure. TVS and OVP form a protection combination for DC and AC interference, they are the mainstream EOS protection solution for the mobile phone industry.

  

  

 

Figure 1 (a): Simplified diagram of charging port circuit of mobile phone, (b) TVS model and specification list.

 

 

 

 

 

Reference:

【1】    Huawei Technology Forum: Analyze Huawei Fast Charge Technology, 2019

 

【2】    OPPO official account: Explanation of OPPO flash charge technology concept, 2018

 

 

 

 

 

 

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