Switching power supply is a method of converting 220V AC mains power into low-voltage DC power, which is different from traditional power frequency transformers. Generally, a power supply that uses this switching voltage conversion technology is called a switching power supply.

There is a "middleman" between the output of the power module and the load, which is a section of PCB wiring. The longer and narrower the wiring, the greater its equivalent resistance. The meaning of equivalent resistance is that in the working circuit of the load connected in series, it can play a voltage divider role, resulting in a voltage difference between the two ends of the load less than the output voltage of the module.

In addition, poor contact of solder joints, line oxidation or corrosion can easily lead to an increase in equivalent resistance.