Charging process of mobile phone
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Charging process of mobile phone
Lithium battery is very common in our life. Many electronic devices use lithium battery, such as mobile phones and drones. In fact, the power adapter is only responsible for converting the alternating current of the power grid into the low-voltage direct current that can be borne by electronic products such as mobile phones, and it is more common to convert AC220V into DC5V. Some power adapters supporting fast charging protocol can also be converted to higher DC voltage, such as 9V, 12V, 20V of Qualcomm qc2.0 / 3.0 protocol.
Mobile phones and other electronic products have special power management chips, which can control the charging process of lithium batteries.
At present, the most commonly used way of lithium battery charging is constant current and constant voltage charging. The charging process of lithium battery can be divided into four stages: 1-precharge; 2-constant current charging; 3-constant voltage charging; 4-stop charging.
1 precharge: when the battery voltage is relatively low (such as lower than 3.0V), due to the poor lithium ion activity inside the battery, it can only be charged with a small current (such as 200mA), otherwise it will cause certain damage to the battery.
Constant current charging: that is, the charging current is constant, that is, we often say CC mode. For constant current charging, we need to keep the current constant. Generally, the charging current is between 0.2c-1c. Pay attention not to exceed 1.5C, otherwise the battery will be damaged greatly. In this process, the voltage of the battery will continue to rise until the battery voltage reaches 4.2V and then enters the constant voltage charging stage. When the battery voltage rises to a certain degree (such as 3.0V), it starts to charge with a large current. In this stage, the charging current is large (generally the set maximum current, such as 2a), and the battery voltage rises rapidly.
3 constant voltage charging: when the battery voltage rises to the upper limit (such as 4.2V), it will be changed to constant voltage charging. In this stage, the charging voltage remains at a stable value, and the charging current gradually decreases.
4 stop charging: when the charging current decreases to a certain threshold (such as 200mA), the battery is considered to be full and the charging is over.
The above charging process is the charging process under the state of full discharge (over discharge) of lithium battery. In actual use, because over discharge will affect the performance of lithium battery to some extent, the power management chip inside the mobile phone and other electronic products has over discharge protection, and under non extreme circumstances, less over discharge occurs. Therefore, there is less precharge state in daily charging.