Abstract: AC/DC switching power supply is the main source of electrical system，its development trend is

large capacity，high power density，high efficiency，low power factor and low harmonic content. However，there are still some common problems with existing digital power supplies，including poor anti-interference ability，simple structure and function，and inability to meet the needs of power plants and substations and other related places. A design of half-bridge switching power supply based on chip control was described，and its main circuit was theoretically analyzed，and the circuits such as electromagnetic interference（EMI）rectifier filter circuit，PFC power factor correction circuit，and LLC half-bridge circuit were designed in detail. The experimental test results show that it with reasonable design serves as large capacity，high efficiency，high power factor and low ripple，which can fully meet the current market demand.

      Key words: high efficiency；power factor correction；half-bridge LLC；AC/DC converter；low ripple