Abstract:Switching power supply with high efficiency and other characteristics of light are widely used in many fields, a huge market. This paper describes the classification of DC / DC converter main circuit analyzes the push-pull DC / DC converter is constituted, at the same time gives the internal structure of the SG3525 chip and pin functions, a detailed analysis of its features and works , with its design of a push-pull adjustable duty cycle DC / DC switching power supply. This paper presents the design method parameter calculation circuit and the main unit of the circuit, and the power performance test. Experiments show that the power supply with high efficiency, high voltage adjustment, output voltage stability and so : switching power supply; SG3525; Push-Pull DC / DC converter; PWM