DC is polar, but most of the AC, such as charger with a USB output interface, the nameplate is DC, but no standard polarity, is this what polarity? Don't tell me to detect the polarity, there is nothing if not detected, the standard polarity, what is the default?
USB, a data transfer standard for peripheral buses, not only defines signal standards, but also defines mechanical standards1, standard USB:There are 4 terminals, 1 of which are power positive (the host side is 4.75 to 5.25V, the device end is 4.5.25V), and the 4 is power and signal ground;
As long as the USB interface is used, the polarity of the power supply has been determinedSince there is no need for the user to connect himself, it is not necessary to note the polarity on the plug (socket) of the USB interface
Mini USB:There are 5 terminals, 1 of which are power positive (4.5.25V), and 5 are power and signal groundSee?
