1, from the 3C specification standards, the domestic is basically according to the +/-10%, so 12V fluctuation range: 10. 8V ~ 13. 2V.
2, from the design point of view, basically will design the power supply output power supply a little higher, generally set at 12.2V, which is a very common voltage value.
Purpose: In order to connect the wires and the impedance of the copper skin of the voltage drop brought about by the design, so that the voltage to the IC is very close to 12V.
Expanded:
Switching power supply products are widely used in industrial automation control, military equipment, scientific research equipment, LED lighting, industrial control equipment, communication equipment, electric power equipment, instrumentation, medical equipment, semiconductor refrigeration and heating, air purifier, electronic refrigerator.
LCD monitors, LED lamps and lanterns, communication equipment, audio-visual products, security monitoring, LED light tape, computer chassis, digital products and instrumentation and other fields. Its function is to convert a bit of voltage, through different forms of architecture, into the voltage or current demanded by the user end.