Abstract: Proposes a topological structure of loss-free heavy current switching power supply based on DSP. For such power supply the input circuit is composed of a series capacitor-switch array and output circuit is composed of a parallel capacitor-switch array. DSP which has rapid run speed and high calculating precision is used as controller, the DSP outputs controllable pulse for on-off control of switch arrays as to change correspondingly the power supply output. Thus state averaging method is used to analyze the charging and discharging processes of the switching power supply. A simulation experiment was carried out to verify the regulation ability of the switching power supply which is featured with regulatable current output. Furthermore, the switching power supply has characteristics of low harmonic, small size, and low power loss.