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In this paper, a hybrid filter structure, which consisting of a passive and a shunt-connected DC active power filter, is proposed for a special high precision, low ripple and large power DC stable/pulse power supply. The main circuit configuration of DC active power filter and its basic concept for suppression harmonics are analyzed in detail. A novel control strategy of DC active power filter with detecting the output ripple voltage, i.e. the reference signal of the DC active power filter is obtained by detecting the output ripple voltage across the DC load, is presented. The advantage of the control approach is that, it is very easy to meet the requirements of low current ripple and fast response in DC stable/pulse power supply, whereas the precision of the circuit transducer and components is not need special request. To validate the proposed concept, a prototype of 12-pulse rectifier system and DC active power filter are manufactured and corresponding experiment investigation is done. Tested by a 120 kW practical industrial application stable/pulse power supply with the DC active power filter and adopting the control approach proposed, its output current ripple factor achieves 8.87×10-6 (peak to peak), in addition to others advantages include fast dynamic response, high efficiency and low cost.