"24V DC Cooling Fan" distributed power distribution system can be divided into AC and DC distribution of two basic structures. Each structure may use different conversion module expansion both in depth and breadth, of course, the two structures may also penetrate each other. AC distributed power supply system by a plurality of AC-DC conversion modules, each circuit board or an AC-DC conversion has a module, the typical structure of the apparatus. Such "24V DC Cooling Fan" structure is more expensive, because each AC-DC conversion module requires its rectification and filtering electromagnetic interference suppression circuit, also means the AC power cord around the entire system, increasing the sensitivity of electromagnetic interference and safety issues . However, in some cases such a structure might be the right solution. For example, a telecommunications equipment manufacturer of telecommunications equipment to take advantage of this structure of a building housing the power supply. Each floor using an AC-DC module, power distribution structure. "24V DC Cooling Fan" This structure is also applied to a computer file server manufacturer .CPU board and every disk drives use an AC-DC power modules.