Mobile phone universal charger circuit diagram and working principle

　　Working principle: The circuit is mainly composed of an oscillation circuit, a charging circuit, a voltage stabilizing protection circuit, etc. Its input voltage is AC220V, 50/60Hz, 40mA, the output voltage is DC4.2V, and the output current is 150mA~180mA. Before charging, first connect the battery to be charged and see if the test indicator light on the charger panel is on. If it is on, it means the polarity is correct and you can turn on the power supply for charging; otherwise, it means the polarity of the battery and the output voltage of the charger are different. The polarity is reversed. At this time, you need to press the polarity conversion switch AN1 (test button).