Switching power supply related issues

而不了了

Switching power supply related issues [Copy link]

 

I would like to ask the experts to help me look at the circuit I designed. I don't know much about circuits and I am not suitable for this field. But I have no choice but to enter the electronics industry.
I want to design a switching power supply that can provide 12V to power the 12V0.14A fan and the 12V10A cooling sheet at the back. These two pictures are the switching power supply I designed. Because I don't understand it very well, I don't know where it is right and where there is a problem. If there are experts who can see it, please help me give some advice, thank you!

gmchen

This is a huge problem.

In the first picture, 220V is rectified first and then transformed. It should be noted that direct current cannot be transformed by a transformer!

The rectified DC high voltage should be directly converted into the required 12V DC using a switching power supply.

maychang

At least the landlord needs to use an industrial frequency transformer to reduce the 220V AC to about 20V AC, rectify and filter it, and then use a Buck circuit to convert the 15-20V DC into 12V DC.

There are many modules on the market that can convert 220V AC into 12V DC with a power of up to 150W. It is better to buy them than to make them yourself.

maychang

The control chip used by the OP is UC3843, which can be powered by AC 220V rectifier and filter. The chip can directly drive high-voltage power MOS tube to act as a flyback converter. For typical application circuits, you can search the UC3843 chip manual.

maychang

Using UC3843, directly powered by 220V AC mains, this flyback switching power supply is much smaller in size, weight and cost than the power frequency transformer solution in the first post. But I guess the poster is still not able to handle the design of such a switching power supply, so I suggest the poster buy a ready-made one.