5V-USB Charger Circuit Diagram, Detailed Production Procedures

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USB charger kit, also known as MP3/MP4 charger, input AC160-240V, 50/60Hz, rated output: DC 5V 250mA (label sticker is 500 mA, 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, but chargers used as daily necessities have the characteristics of high failure rate and easy damage because they are directly connected with 220V high voltage. Especially when they buy immature products, they are hard to read. Finally, entrusted by the school teachers, we have contacted a mature mass-produced charger suite, and now share it with the majority of electronic enthusiasts.

The following is the circuit schematic diagram drawn against the physical object: (There are many ways to install components on the circuit board, the installation should be in accordance with the schematic and physical drawings, some components on the pcb board should not be installed, and some components should be installed on other components, this point please note!) Explanation: In order to simplify the circuit and achieve the goal of learning, in the figure, the resistance F1 of 1 Euro acts as a fuse and a diode D1 acts as a rectifier. After switching on the power supply, C1 will have a DC voltage of about 300V, which will supply current to Q1 base through R2. The emitter of Q1 has a R 1 current detection resistance R 1. When Q1 base is electrified, collector current will be generated through (3, 4) of T1. At the same time, induction voltage will be generated on (5, 6) (1, 2) of T1. These two secondary insulated coils have the same number of coils. The output of T1 (1, 2) is rectified by D7. C5 filters and supplies power to the load through USB pedestal; T1 (5, 6) filters through D6 rectifier, C2 filter, IC1 (4.3V regulator) and Q2 constitute sampling comparison circuit to detect the output voltage; T1 (5, 6), C3, R4 also constitute positive feedback circuit of Q1 triode, which makes Q1 work in high frequency oscillation and continuously supplies power to T1 (3, 4) switch. When the output voltage rises due to any reason of lighter load or higher power supply voltage, the sampling comparison of T1 (5, 6) and IC1 leads to Q2 conduction, Q1 base current decreases, collector current decreases, and load capacity decreases, resulting in lower output voltage; when the output voltage decreases, Q2 sampling will be cut off, Q1 load capacity will become stronger, and output voltage will rise again. It can regulate the voltage automatically.

Although the circuit has few components, it also has the function of over-current, overload and short-circuit protection. When the load is overloaded or short-circuited, the collector current of Q1 increases dramatically, while the emitter resistance R1 of Q1 produces a higher voltage drop. The high voltage generated by overload or short-circuiting will pass through R3 to make Q2 saturated and turn off the output of Q1 to prevent overload damage. Therefore, the load capacity can be changed by changing the size of R1. If the output current is small, for example, only 5V100MA is needed, the resistance of R1 can be increased. Of course, if you need to output 5V500MA, you need to reduce R1 appropriately. Note: Reducing R1 will increase the possibility of burning Q1. If high current output is needed, it is recommended to replace 13003 and 13007 high power transistors.
What role does C4, R5 and D5 play? T1 transformer is an inductance element. Q1 works in the switching state. When Q1 is cut off, it will induce a high voltage at the collector. This voltage may be as high as 1000 volts, which will damage Q1 breakdown. Now there is a high-speed switch D5. This voltage can charge C4 and absorb this high voltage. After charging C4, it can discharge through R5 immediately, so Q1 will not break down due to the high voltage of the collector. Damaged, therefore, if the three components have switches or damaged, Q1 is very dangerous, minute by minute may be damaged.
After receiving the goods, we should first familiarize ourselves with the circuit schematic diagram, analyze the principle, then measure the components, and finally assemble them carefully.

Installation Notes:

Before installation, please do not rush to start. First consult the relevant technical information and this description, then compare the schematic diagram, understand the printed circuit board, component list, and distinguish the components, understand the characteristics, functions, and check the number of components.

Note: Z1, D2, D3, D4, IC1 are not equipped with this kind of assembly, the circuit board is designed for multi-purpose, this kit only uses half-wave rectifier, only a 1N4007 rectifier, please do not install other diodes yourself, refer to the model, the sample has been tested is OK, friends who have done in the factory know, the factory is produced according to the model.
Correct insertion of components, according to the smooth installation from low to high, from small to large, the polarity should comply with the requirements. For manual installation, components should be installed in batches. So the board first resistor diode transistor capacitor transformer USB seat 1, Q1, Q2 must not be misfitted. Q1 should choose the tube with switching characteristics over 500V, Q2 can withstand tens of volts. Q2 is suitable for selecting the tube with good amplification characteristics. The pin arrangement of these two kinds of tubes may be different from conventional ones. Please take the measurement as the standard.
2. IC1 and D6 should not be misfitted. They are also glass-encapsulated diodes. One is a 4.3V voltage stabilizer diode and the other is a common diode. IC1 is only a symbol on the PCB board, and the diode only occupies two PCB element holes.
3, 1N4007, FR107, 1N5819 please do not misfit, 1N4007 is a low-frequency diode, FR107 is a high-frequency high-voltage diode, 1N5819 is a low-voltage high-frequency Schottky diode, can not be misplaced. (Substitution relationship: FR107 can replace 1N4007, otherwise not; and 1N5819 can not be replaced by other diodes, 1N5819 can not be replaced by other diodes. The conduction voltage of 1N5819 is very low, which is equivalent to the conduction voltage of germanium tube. Therefore, low voltage rectification efficiency is very high. If other diodes must be replaced, the output power will be downloaded, the heating is serious and the efficiency will become low.) Remember: FR104 (7) is a high frequency output rectifier diode, and 1N4007 is the power supply rectifier diode.

Power-on test circuit board:

After carefully checking the installation of PCB, a 220V plug can be welded directly on PCB board when power test board is turned on. In order to be safe, please connect a 10W incandescent bulb in series with the power supply to prevent short circuit or wrong connection. Take care of safety. Also, components burn out carelessly and need to be bought again if they burn out. If the installation is correct, the multimeter can measure the voltage output of the USB1 foot and the 4 foot should be 5V, the power indicator light is on, confirm the assembly of the circuit board is correct.


read ()  •  Jun 28, 2019  •  Edit



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