The principle of the charger

　　There are generally three types of mobile phone chargers, including travel chargers, dock chargers, and USB chargers. Do you know the principle of chargers? Follow the charger manufacturer to learn about it today!

　　   First, the charging principle of mobile phone chargers

　　In my country, the rated voltage value for civil use is 220V, and it is not possible to charge the mobile phone directly. The function of the mobile phone charger is to convert the 220V high-voltage pulse into low-voltage pulses, such as 5V, 9V, 12V, etc., and pass the rectifier and voltage regulator circuit. direct current. In other words, the main function of the mobile phone charging head is a charging solution that converts high-voltage alternating current into 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 inserted into the mobile phone charging port. The high current depends on the load state. As long as the phone is in ideal condition, the charger can provide more current. If the responsible power exceeds the charger's withstand current, the charger will always output the maximum current. This is because the charger is equipped with a protection circuit. If the current is too large, the protection mechanism will be automatically triggered to limit the current output and prevent dangerous factors. In other words, if a 50W super fast charge is used, if the mobile phone only supports 18W maximum charging, then The maximum charging power is theoretically only 18W.

　　   Second, the operation principle of the charger and lithium battery

　　  The charging target of mobile phone chargers is lithium batteries, which are composed of positive electrodes, negative electrodes, separators, and electrolytes. Its operating principle is that during the charging process of the lithium battery, the lithium ions in the positive electrode material are dissolved out and embedded in the modified graphite layer of the negative electrode. When the battery is discharged, lithium ions are deintercalated from the graphite layer and backfilled into the positive electrode cobalt lithium oxide layered structure through the separator. Lithium ions are rapidly intercalated and deintercalated from the positive and negative electrodes along with charging and discharging. Taking a 5V/4A charger as an example, when the charger charges a lithium battery, it can be divided into two steps. First, constant current charging, and then gradually increase the voltage when the current is stable. 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. In theory, the charging efficiency of a 5V/4A charger should be 20W, but it is found that the highest charging efficiency can only stay at around 17-18W. This is because 5.0V is not the actual voltage of the battery, but the sum of the battery voltage and the internal resistance consumption of the battery. , 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 should be slowly reduced through the constant voltage charging process, so that the actual voltage of the battery can be closer. 5.0V.

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Main circuit part (not including transformer design)