Here is the concept of mobile charger convert AC to DC and then also convert AC to DC back ( but it’s not that straight forward).

Concept of mobile charger

Mobile charger is a device or components assembled together to stores energy in a battery ( charging or recharging) by running an electric current through it, and a normal charger convert 220v AC to 5vDC.

Components used for construction

1. Diodes
2. Transistors
3. Transformer
4. LED
5. Capacitors
6. Auto coupling
7. Resistors.

Stages in the concept of mobile charger and the working principles

1. Stage 1. Is for the phase wire which are live L and neutral N.
2. stage 2. Is the resistor whose value is 260,000 ohm with resistor color code RED, BLUE, YELLOW AND GOLD, which serve as a fusible resistor that prevents damage from over loading.
3. Then 3rd stage is the bridge rectifier made by 4IN4007 and filter capacitor 450v, 2.2uf, this circuit convert AC to DC and also filter the current that entered the circuit.
4. 4th stage is the isolator circuit whose work is to convert DC back to high frequency AC 15 to 50kv and the component that dose this works are as follows : transistors (TS 8050) And (TI 3001) and 2mohms, 560ohms, 1kohms, 10ohms resistors, and also 4.7nf.
5. Stage 5. Is the AC to DC converting circuit which house the following components 50v, 2.2uf and fast switching diode 1N4148 which looks like zener diode.
6. Transformer which has three windings which are :primary ,secondary and auxiliary winding wrapped around the coil it is used to step down the voltage, the auxiliary winding us used to run the isolating circuit.
7. Stage 7. Is the schlocky diode IN5819.
8. Stage 8. Is a capacitor 10v, 470uf to convert AC to DC.
9. Stage 9. Is a LED for indication.
10. Stage 10. Is a feedback circuit that consists of auto coupling PCA 17C and 4.2v zener diode which is used for transmitting signal without a contact inside it, on the right side, we have infrared LED and on the left is the photo transistor turning it ON.
11. Stage 11. Is a 102nf capacitor used for safety purposes which is connected between primary and secondary ground to stop electromagnetic in the fields.

Working principles of Concept of mobile charger

Working it the input of 220v, 50Hz AC which will enter into the bridge rectifier whose work is to convert AC to fluctuating DC which feds into the capacitor to form a pure DC which enters the circuit and pass through 92m ohms Resistor and then enter into the base of T1(T31001) and turns it ON, because of the resistor it’s partially turns and due to the partially turning ON of the transistor, low current pass through the primary winding of the transformer.
This is induced voltage in the auxiliary winding, and the induced voltage now charger the 4.7nf capacitor and the capacitor fully turns ON the transistor and as the transistor is now fully ON it allow it allows current to flow through itself.
And it then turns ON the transistor T2(TS 8050) and these shot the base of T1 and turns it OFF, as the T1 turns OFF the flow of current in T2 is cut OFF. now the current flows to the base of T1 and the cycle repeats and these happen at 15 to 50kv which is thousand time faster than the rectifier circuit.
Hence, the rectifier circuit will stop and at the same time, the voltage from the auxiliary winding turns the diode ON which helps to charge the capacitor and flows to the auto coupling, these diode and capacitor convert AC from the auxiliary coil to DC for the auto coupling.
The coil also induced in the secondary winding and it’s converted to DC by schlocky diode and filter capacitor and it’s indicate by the LED.
but if the voltage is more than 5v. Hence, we have feedback circuit as it reaches 4.2v the zener diode turns ON and allow current to flow to the auto coupling and it also Drops the voltage by 4.2v, hence, the LED on the auto coupling dose not turns ON, the LED Required 0.8v to turn ON. when the voltage reaches more than voltage 5v it turns ON the LED of the auto coupling. The live of the LED turns ON the photo transistor of the auto coupling allowing the current to flow through the T2, this turns ON the transistor T2, this turns ON transistor T2 shorten the first and stop the flow of current in the primary winding.
Also, the voltage in the secondary side of the transformer drops below 5v turning OFF the zener diode and auto coupling and the circuit continue to run normal.

Question : why the circuit converts AC to DC?.
Answer : this is because for the normal power supply which has 50Hz, the size of transformer and capacitor are large and they can not be mounted in a small charger. Hence, in a charger the 50Hz frequency is converted to 50k Hz. This reduces the size of the transformer and capacitor required in the circuit.
Note: to change the frequency to DC first we have to convert it to DC, then again back to AC.

Conclusion :

However, with this you now know how your mobile phone charger works.