Power supply is an important component of LED lighting. Considering the power supply’s lifespan didn’t match LED’s long lifespan by the electrolytic capacitor’s own feature,we propose a step-down transformer topology structure of active ripple compensation based on BUCK circuit. This topology took full advantage of the characteristics of switching power supplies and linear power supplies to replace the traditional electrolytic capacitor filter with the auxiliary active circuitry compensation inductor ripple current. We analyzed the structure and the operation principle of the new topology and confirmed the validity of the new topology. The theoretical analysis and experimental results show that using the topological structure of active ripple compensation can completely compensate inductance’s ripple current,so that the circuit output is DC.