How well do you know about your Fast-Charging phone?

1.The reason Fast-Charging spring up

With the development and popularization of smart phones, which penetrates into our life deeply, the way to improve battery life and shorten battery charging time has become an important goal among all the cellphone manufacturers. As the battery capacity can’t be expanded without limits, the quick charge technology emerges to save people’s time. However, do you really know what is quick charge? Let’s get through this with a simple explanation.

Working principle

There are 3 main quick charge technology, Qualcomm’s Quick Charge (2.0/3.0), OPPO’s VOOC charge and MediaTek PumpExpress.

According to the formula P (power) = U (voltage) X I (current), improving the power means shorten the charging time while the battery capacity is fixed. All the fast charging technology is based on implementing bigger voltages and currents while charging.

A. Qualcomm Quick Charge 2.0

Qualcomm Quick Charge technology is designed for Qualcomm Snapdragon processor terminal, which has been developed to the 3rd generation already.

Charging process:

The QC 2.0 charger connects with the cellphone by on-loading voltages on micro USB port (D+ and D-) , to adjusts the output voltage.

USB port


  1. Step 1. When connected the phone to charger via USB cable, the D+ and D- port will be short circuit by default through MOS, the phone will be charged normally at the moment (the voltage is 5V). If the phone support QC2.0, the HVDCP(high voltage dedicated charger port) on the android device will on-load 0.325V to D+ port lasting over 1.25s.
  2. Step 2. Lasting over 1.25s, the D+ and D- port will be disconnected and the D- voltage will drop.
  3. Step 3. After the device detected the D-voltage has dropped, the HVDCP can read the value in the file of /sys/class/power_supply/usb/voltage_max, if it’s 9000000Mv, then the voltage on D+ port will be set to 3.3V and D- will be 0.6V, then the output voltage will be adjusted to 9V. If not, the voltage of D+ will be set to 0.6V while the D- for 0V.
  4. Step 4. The charger will apply different Voltage to charge the device.

charging time

B. OPPO VOOC charge

The vooc charge technology shorten the charging time by the way of increasing the electric current, it can be described briefly with the picture below.

As we can see from the picture below, the OPPO Vooc charger cable is different from the normal USB charger cables, the charging interface port has been increased to 8 pins while the normal one only features 4-5 pins, which allows more currents passing.

vooc charging effeciency2

C. MTK Pump Express

Actually the working principle of MTK PE charging technology is almost the same as Qualcomm Quick Charge 2.0, the difference is that the MTK PE charging ‘handshake protocol’ is realized by regular VBUS current pulse between the phone and charger. And another difference is that the highest MTK PE charging voltage is 9 and there is one more voltage rank 7V within.


2. Does fast charging technology hurt battery?

The quick charge process can only work when both the cellphones and the charger support fast charging. On the current situation, the charging power are totally affordable within the range of battery capacity, generally speaking, since the ‘handshake protocol’ can act as a coordination between the charge adapter and the phone battery to adjust the voltage and current value. As long as you choose the original charging power adapter to charge for your phone there won’t be damages to your battery.

(PS:picture sources from internet)

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