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IC: TNY255 (DIP8) (dual in-line 8 feet)
PCA817A optical isolation (DIP4) (dual in-line 4 feet)
TR: 2SC1815
DIODE: HER303 (3A200V)
IN4148
13V 1/2W Zener Diode
HER107 (1A1000V)
BRIDGE: 500MA/600V
C: 22UF/400V
470UF/25V*2
0.1UF SMD*2
4700PF/1KV
1000PF/2KV
R: 10OHM 1W
0.82OHM 1W
120KOHM 1W
47OHM 1/4W*3
220OHM 1/4W
Description:
1: Because the switching frequency is as high as 130Khz. Be sure to select high-frequency rectifiers such as HER303 (3A200V) and Schottky's 31DQ10 (3A100V). Do not use FR series diodes, which are not fast enough and may be damaged in a short time. A large waste tube with a large current capacity can also reduce a lot of losses because the junction pressure drop is reduced at a small current.
2: Regarding the switching transformer, the domestic EE16 high-frequency magnetic core is used here, and an air gap of 0.1 mm thin paper is added on each side of the iron core. It should be noted here that before the core is assembled, it is filled with epoxy glue, which will stabilize the structure and greatly reduce the audible noise. The number of turns of the coil does not have to be too accurate, but the turns are more accurate.
3: The external wires and exposed components of the necessary places lead the heat-shrinkable tube on the foot cover, which will play a good role in safety.
4: Simply change the component value to adapt to other battery charging needs, but the total output power is less than 10W.
5: Proper arrangement of the PCB, a 35mm * 58mm board is enough. Commercially available, some special power molded plastic cases can be found, and the final assembled charger is almost the same as the finished product. 