The phone chargers that we buy now are basically equipped with fast charging technology. In general, charging power grater than 10W (that is, 5V 2A) can be called fast charging.

Let’s briefly introduce the evolution of the charging technology of mobile phones.

At first, the battery capacity of mobile phones is not large, the defaulted 5V 0.5A of the USB interface can meet the charging needs. However, when smart phones came out, 0.5A could not fulfill the charging needs anymore. Hence an enhanced USB charging identification standard: BC 1.2 came out, which extended the charging current up to 5V 1.5A. However, by the year of 2013, the battery capacity of smart phones reached 3,000. At this time, even 5V 1.5A could not meet the demand, so the charging power expanded to 5V 2A again.

Tip 1
When you charge your phone, the charging current is controlled by the phone , not the charger. That is to say, the mobile phone will detect the load capacity of the charger automatically. Smart mobile phones will allow the chargers to load higher current, if the the charger’s charging power is high. This is the reason why we want to buy a high-power charger.

Let’s go back to the history of mobile phone chargers. In fact, 5V 2A is Qualcomm’s Quick Charge 1.0 technology. In order to prevent the chargers from being fully loaded, the smart phones usually limit the input current around 5V 1.8A.

We all know that the key to increasing the charging speed is to increase the charging power. Here is the formula:Power (W) = Current × Voltage, the charger first step down the commercial voltage to 5V output to the phone Micro USB interface, and then the internal circuit of the phone step down the 5V to 4.3V to charge the battery. There are two steps in the buck.

The voltage is fixed, that is 5V, so we have been studying how to increase the current. But there was a bottleneck when the charging power reached 5V 2A, the Micro USB interface and the charging cable could not bear the charging current. So Qualcomm proposed a high-voltage way, Quick Charge 2.0. We can improve the voltage from the charger to the USB interface, and this was indeed a very good idea. Increasing the voltage can increase the charging power without changing the current load of the cable. We don’t need to replace the interface and the cable, which greatly saves the cost.

Qualcomm designed two solutions on the Quick Charge 2.0 – Class A and Class B. The Class A has been used in mobile phones that can output three voltages which is 5V, 9V, and 12V. The Class B solution voltage was basically for tablets and notebooks that output four voltages which is 5V, 9V, 12V, and 20V.

Tip 2
When you charge your phone, the current is not always the same. The phone will ask the charger to work at full speed when your phone is in low battery state. This is called the peak. During this time, and the charging speed is very fast, but the power consumption and heat are also considerable.

Generally, when the quantity of electricity rushing to 60%~80%, the mobile phone will send a signal to the charger to reduce the current so as to protect the battery. During this time, the power consumption and the heat will drop significantly. That is, the turbulent charge that we often say.

Once again, the charging current is controlled by the mobile phone, the charger can only adapt to the needs of the mobile phone. It is stupid to say that the charging power is too high to damage the mobile phone if is under the same voltage.