5V-USB charger kit production steps, with circuit diagram

describe:

USB charger kit, also known as MP3/MP4 charger, inputAC160-240V, 50/60Hz, rated output: DC 5V 250mA (label sticker is 500mA, if you want to output more current for a long time, please replace Q1 with 13003). MP3 and MP4 are popular all over the country. However, chargers, which are daily necessities, have a high failure rate and are easily damaged because they are directly connected to 220V high voltage. Especially after buying immature products, it is really hard to understand. . Finally, entrusted by the school teacher, we contacted a mature mass-produced charger kit and now share it with the majority of electronic enthusiasts.

The following is a schematic diagram of the circuit drawn against the real thing: (There are many ways to install components on the circuit board. Please refer to the schematic diagram and the actual picture for installation. Some component holes on the PCB board do not need to be installed, and some components need to be installed in other places. component holes, please pay attention to this!)

Note: In order to simplify the circuit and achieve learning purposes, a 1-ohm resistor F1 is used as a fuse in the figure, and a diode D1 is used to complete the rectification function. After the power is turned on, C1 will have a DC voltage of about 300V, which provides current to the base of Q1 through R2. The emitter of Q1 has an R1 current detection resistor R1. After the base of Q1 is powered, it will pass through T1's (3, 4 ) generates a collector current and simultaneously generates an induced voltage on (5, 6) (1, 2) of T1. These two secondary insulated coils have the same number of turns, in which the output of T1 (1, 2) is rectified by D7 , C5 filters and supplies power to the load through the USB socket; among them, T1 (5, 6) is rectified by D6 and filtered by C2, and then passes through IC 1 (actually a 4.3V voltage regulator tube) and Q2 to form a sampling comparison circuit to detect the output voltage; where T1 (5, 6), C3, and R4 also form the positive feedback circuit of the Q1 transistor, allowing Q1 to work in high-frequency oscillation and continuously supply power to the T1 (3, 4) switch. When the output voltage rises due to any reason such as the load becomes lighter or the power supply voltage becomes high, the sampling comparison between T1 (5, 6) and IC1 causes Q2 to turn on, the base current of Q1 decreases, the collector current decreases, and the load capacity becomes smaller. , thus causing the output voltage to decrease; when the output voltage decreases, Q2 will cut off again after sampling, the load capacity of Q1 becomes stronger, and the output voltage will increase again; this plays an automatic voltage stabilizing role.

Although this circuit has few components, it is also designed with overcurrent, overload and short circuit protection. When the load is overloaded or short-circuited, the collector current of Q1 increases greatly, and the emitter resistor R1 of Q1 will produce a higher voltage drop. The high voltage generated by this overload or short-circuit will pass through R3, causing Q2 to saturate and conduct, thus allowing Q1 Cutoff stops output to prevent overload damage. Therefore, changing the size of R1 can change the load capacity. If the output current is required to be small, for example, only 5V100MA needs to be output, the resistance of R1 can be changed to a larger value. Of course, if you need to output 5V500MA, you need to make R1 appropriately smaller. Note: Changing R1 to a smaller value will increase the possibility of burning out Q1. If high current output is required, it is recommended to replace 13003 or 13007 medium and high power tubes.

What are the functions of C4, R5 and D5? The T1 transformer is an inductive component, and Q1 works in a switching state. When Q1 is turned off, a very high voltage will be induced at the collector. This voltage may be as high as more than 1000 volts, which will cause Q1 to breakdown and damage. Now there are high-speed switching tubes. D5, this voltage can charge C4 and absorb this high voltage. After C4 is charged, it can be discharged through R5 immediately, so that Q1 will not be damaged by the high voltage breakdown of the collector . Therefore, if these three components are switched or damaged, Q1 It is very dangerous and can be damaged every second.

After receiving the goods, everyone should first familiarize themselves with the circuit schematic diagram, analyze the principles, then measure each component, and finally assemble it carefully.

Installation Precautions:

Before installation, please do not rush to start. You should first consult the relevant technical information and this instruction, and then compare it with the schematic diagram to understand the printed circuit board and component list, distinguish each component, understand the characteristics, functions, and functions of each component, and check the number of components at the same time. .

Note: Z1, D2, D3, D4, and IC1 are not equipped for this assembly. The circuit board is designed to be multi-purpose. This kit only uses half-wave rectifier and only one 1N4007 rectifier. Please do not install other diodes by yourself. Just refer to the sample in the picture and make it. The sample has been tested and is OK. Friends who have done it in the factory will know that the factory produces according to the sample.

Insert the components correctly, install them smoothly from low to high, small to large, and the polarity must comply with the regulations. For manual installation, components should be installed in batches. On this board, first resistor→diode→transistor→capacitor→transformer→USB socket

1. Do not install Q1 and Q2 incorrectly. Q1 should use a tube with switching characteristics with a withstand voltage of more than 500V. Q2 can withstand a few dozen volts. Q2 is suitable for choosing a tube with good amplification characteristics. The pin arrangement of these two tubes May vary, please refer to measurement.

2. Please do not install IC1 and D6 incorrectly. They are also glass-encapsulated diodes. One is a 4.3V Zener diode and the other is an ordinary diode. IC 1 is just a symbol on the PCB board. The diode only occupies two PCB component holes. .

3. Please install 1N4007, FR107 and 1N5819 correctly. 1N4007 is a low-frequency diode, FR107 is a high-frequency and high-voltage diode, and 1N5819 is a low-voltage and high-frequency Schottky diode. They cannot be installed in the wrong position. (Substitution relationship: FR107 can replace 1N4007, but not vice versa; 1N5819 cannot be replaced by other diodes. The turn-on voltage of 1N5819 is very low, equivalent to the turn-on voltage of a germanium tube. Therefore, the low-voltage rectification efficiency is very high. If Be sure to use other diodes instead, otherwise the output power will be reduced, the heat will be severe, and the efficiency will become lower.)

Remember: FR104(7) is a high-frequency output rectifier diode, and 1N4007 is a power rectifier diode.

Power on and test the circuit board:

After carefully checking that the circuit board is installed correctly, when you want to energize the test board, you can directly solder a 220V plug wire on the PCB board. For safety reasons, please first connect a 10W incandescent bulb in series with the power supply to prevent short circuit or wrong connection. Pay attention to safety. Also, components may burn out accidentally. If they burn out, you need to buy another one. If the installation is correct, you can use a multimeter to measure the USB

Pin 1 and pin 4 should have a voltage output of 5V, and the power indicator light is on, confirm that the circuit board is assembled correctly.