Switching power supply is a way to convert 220V AC power into low-voltage DC power. It is different from traditional power frequency transformers. The power supply that uses this switching voltage conversion technology is called switching power supply.

There is a "middleman" between the output of the power module and the load. He is-a section of PCB traces. Long and narrow traces indicate that its equivalent resistance is greater. The equivalent resistance means that in the working circuit connected in series with the load, it can play the role of voltage division, so that the voltage across the load is less than the output voltage of the module. In addition, poor solder joint contact, line oxidation or corrosion are all likely to cause an increase in equivalent resistance.