Switching power supplies use High frequency transformers The reason.

Switching power supplies use High Frequency Transformers The reason.

1, for safety, regardless of high frequency or low frequency, it is necessary to isolate the high voltage with a transformer.

2, high magnet transformer both from the material and copper wire are very economical, and small volume.

3, silicon steel sheet a material of low frequency transformer, large volume, not economic, only for low frequency pulse power isolation.

High frequency transformers

4, why not use the transformer isolation at the rectifier? Because you want to switch power supply both save material and compact, you can not use a large volume of low-frequency rectifier at the front of the frequency transformer, and because the high-frequency rectifier diode can not reach the switching tube, high-frequency transformer output tens of thousands of KHz high-frequency square wave.

5, the old cell phone charger with frequency transformer, only 500mA output, because the low frequency 50Hz can not make the secondary side of the coil induction greater electric field, you want to change the output power, the primary original coil diameter and the number of turns by the limitations, if the line thick, winding the number of turns less will make the transformer no-load hot, so only the switching tube to send out high-frequency oscillation and then the output of a compact high-frequency transformer, rectified and filtered by And then regulated, in order to output a safe low-voltage high current (such as 5V4A).