The mobile phone with the emergency charger can emergencyly charge the power-off mobile phone in the absence of power supply, ensuring that the mobile phone information is continuous and unimpeded. The charger is characterized by an imported PWM switching power supply chip lM3578 for DC/DC boost, the input voltage can be as low as 2V, the output current can reach more than 200mA, and the use of two 5th rechargeable batteries can work satisfactorily.
Working principle: mobile phone with emergency charger circuit. As shown in the drawing. The core device IC1 used is a single-chip PWM switch controller, which contains four functions: oscillator, reference voltage, error amplification and driving transistor. The external circuit is connected to the capacitors C1—C6, the resistors R1 to R6, the inductors L1 and L2, and the power switch BG1 to form a DC/DC boost circuit. The IC13 pin is connected to C2 to determine the oscillation frequency of about 50 kHz. The C3, R3 and C4 switch functions in the connected state. The collector (6-pin) of the drive tube is connected to the output voltage through R6 and LED1. In order to increase the driving capacity, but must add L2 and C6 to prevent the output and input from causing parasitic oscillations and the emitter (5 feet) connected to the power switch BG1, add the sampling resistor R5 and connect to the 7 pin of IC1 to control the maximum operating current. The working process of the circuit is as follows: the working voltage Vi is turned on, the switch controller IC1 starts to work, and the output square wave signal is amplified by the BG1 through the energy storage inductor L1. When BG1 is turned on, L1 stores energy; when BG1 is turned off, L1 passes the boost. Diode D1 discharges electrical energy, thus obtaining a boost voltage that is several times greater than Vi on capacitor C5. The voltage is sampled through the resistors R1 and R2 and sent to the inverting terminal of the error amplifier, that is, the 1 pin, so that the output voltage remains stable; the other is fed into the collector of the IC1 internal driving tube, that is, the 6 pin, to increase the injection current of BG1, wherein LED1 For charging instructions.
Component selection: IC1 model is LM3578, double in-line, available on the market. BG1 model D882, TO-126 package, select tube with β greater than 100. The L1 market is available. If self-made L1, take φ12mm high-frequency magnetic ring, use φ0.15 color line to wear about 60T, which can be measured by the inductance meter about 330μH, and the other inductor L2 is color code inductance, which is very cheap on the market. In addition to the C6 capacitor, the capacitors are CBB type, and the resistors have no special requirements. D1 is a boost diode, which uses a Schottky diode, model lN5817-5822, and its forward voltage drop is VF=0.2V.
Use: After the assembly is completed, you can access 2 No. 5 rechargeable batteries, and the capacity is greater than 1600mAh to work normally. The output can be equipped with a dedicated power plug for the mobile phone, which can be removed from the old charger. Connect directly to your phone. When charging, LED1 flashes to indicate that it is charging.
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