手机充电器（Mobile phone charger）.docVIP

手机充电器（Mobile phone charger） The mobile phone charger is a charging device configured for charging the mobile phone. In fact, the mobile phone charger is a charging system composed of a voltage stabilizing power supply and a control circuit, such as voltage limiting, constant current and time limitation. The most common contact with users is the purchase of mobile phones with the original charger, as well as the purchase of their own travel charger. The principle of mobile phone charger The mobile phone charger circuit is mainly composed of oscillation circuit, charging circuit and voltage stabilizing protection circuit. The input voltage is AC220V, 50 / 60Hz and 40mA, the output voltage is DC4.2V, and the output current is between 150mA and 180mA. 1. oscillating circuit The circuit mainly consists of triode VT2 and switch transformer T1. After switching on the power supply, the AC 220V is rectified by diode VD2 half wave to form a DC voltage of about 100V. The voltage is added to the C pole of the triode VT2 by the 1 primary winding of the switch transformer T, and at the same time, the voltage provides a positive bias voltage through the B pole of the starting resistance R4 to VT2, so that the VT2 is conducted. At this point, the triode VT2 and switching transformer T1 composed of intermittent oscillation circuit began to work, the switch transformer T 1-1 primary winding current through. Due to the positive feedback, the voltage induced by the 1-2 winding of the transformer T is added to the B pole of the VT2 through the feedback resistor R1 and the capacitance C1, so that the B pole VT2 current of the triode is increased, and the current is rapidly entered into the saturated zone. As the voltage across the capacitor C1 rising, VT1 B voltage gradually reduced, the triode VT2 gradually withdraw from the saturated zone, the collector current begins to decrease, the magnetic flux generated 1-1 primary winding of the transformer in T began to decrease. In transformer