Charger principle

　　There are basically three types of mobile phone chargers, including travel chargers, docking chargers, and USB chargers. Nowadays, most smart phones are travel chargers. The charger is composed of a stable power supply plus necessary voltage limiting, constant current, and time limited control circuits. With the rapid development of smart phones, the output technical parameters of the chargers are also different. For example, the output of the original Apple charger is 5.0V/1A, and the output power is 5*1=5W. There are many technical parameters of the charging output power of the Android mobile phone charger. The maximum charging efficiency can reach 50W. However, the higher the output power, the higher the technical specifications and requirements. Nowadays, more and more mobile phone chargers have been damaged. Once damaged, it is forbidden to reconnect the power supply or charge the mobile phone. Preventing the charger failure from deepening can also ensure the safety of the mobile phone.

　　In our country, the rated voltage value for domestic use is 220V. It is not possible to directly charge the mobile phone. The function of the mobile phone charger is to convert 220V high-voltage pulses into low-voltage pulses, such as 5V, 9V, 12V, etc., and through rectification and voltage stabilization circuits, it will be stable Direct current. In other words, the main function of the mobile phone charging head is the charging scheme that converts high-voltage alternating current to low-voltage direct current.

　　If the charging head is directly connected to the socket, no current will be generated, and then the charger will run when it is plugged into the mobile phone charging port. The large current depends on the load status. As long as the mobile phone is in perfect condition, the charger can provide more current. If the responsible power exceeds the current on-line of the charger, the charger will always output the maximum current. This is because the charger is equipped with a protection circuit inside. If the current is too large, it will automatically trigger the protection mechanism to limit the current output to prevent dangerous factors. In other words, if you use a 50W super fast charge, if the phone only supports 18W maximum charging, then The maximum charging power is theoretically only 18W.

　　Second, the operating principle of the charger and lithium battery

　　The charging target of a mobile phone charger is a lithium battery, which is composed of a positive electrode, a negative electrode, a separator, and an electrolyte. The operating principle is that during the process of charging the lithium battery, the lithium ions in the positive electrode material are dissolved and embedded in the negative electrode modified graphite layer. When the battery is discharged, lithium ions will be deintercalated from the graphite layer and backfilled into the positive electrode cobalt lithium oxide layered structure through the separator. With charge and discharge, lithium ions will be quickly inserted and extracted on the positive and negative electrodes. Take a 5V/4A charger as an example. When the charger is charging a lithium battery, it can be divided into two steps. First, constant current charging. When the current stabilizes, then the voltage is slowly increased. When the voltage reaches 5V (ideal value), it changes to Constant voltage charging, when the voltage is constant, the current will slowly decay until it is less than the preset value. Theoretically speaking, the charging efficiency of a 5V/4A charger should be 20W, but through testing, it can only stay at about 17-18W. This is because 5.0V is not the actual battery voltage, but the sum of the battery voltage and battery internal resistance consumption. , If the current is large, the internal resistance consumption voltage will increase, so the actual charging voltage is more and more smaller than the technical parameter voltage, so the current must be slowly reduced through the constant voltage charging process, so that the actual battery voltage can be closer 5.0V.

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