A Kind Of Ac/dc Switching Power Supply Control Chip Circuit Design And Layout

With the increasing high demand of energy-saving electronic devices in the social life, switching power supply with its small size and high efficiency is increasingly being used in a variety of power conversion occasions.This paper applied to design a type of chip which is used in the flyback power converter. There is a700V power MOSFET integrated in the chip, and the chip has a function of constant current and constant voltage outputting. By sampling the output voltage, the system can control the oscillator frequency to stabilize the output current; or according the feedback voltage, the system can decide the number of skip cycle of the power transistor gate signal to stabilize the output voltage. The chip has a function of inductance correction which could minimize the impact of inductance error; and the chip has the cable voltage drop compensation; it has frequency jitter to minimize the electromagnetic interference; its thermal shutdown feature could turn off the power transistor when the temperature is too high and protect the power transistor from being damaged; the chip could automatically restart when the peripheral circuit fails.The paper first introduces the main structure of the chip and its basic working principle. The circuit designing process and pre-simulation results of the reference, the oscillator, the over and under voltage, and the feedback are introduced in the paper. And the whole circuit is simulated. Secondly, the article introduces the tapeout process and the layout design process. The layout of the reference, the oscillator, the feedback, the inverters which drive the power transistor are given in the article. In the layout of the reference, because of the low precision of well resistance, some unused resistors are placed in the chip for unexpected using. We can choose series and parallel program of the resistors according to the error to minimize the resistance error’s interference. In the end, the placement, routing of the whole chip and the verification process are discussed.