Based on the analysis of the characteristics of traditional switching power supply, a design of stabilized voltage switching power supply based on TL494 is proposed. The design improves the traditional BUCK circuit and alleviates the contradiction between efficiency and ripple. Two improvements are adopted in the design: switch tube instead of continuous current diode, and multiple filter capacitors in parallel instead of a single filter capacitor. Through testing, the ripple coefficient can be reduced to 1.6% when the power supply efficiency is more than 85%. In addition, the design also has the function of over-current protection and load identification.