The Desgin Of A AC/DC Switching Power Supply Control Chip

The switching power supply is used in all kinds of electronic products. Along withscience and technology are develop, the requirement of the switching power supply alsobecomes more and more high. Now, all kinds of high-tech products change to miniaturizationand portable, AC/DC converter, as a kind of the switching power supply, also needs becomesmall volume and high accuracy. In such an environment, the research of AC/DC converter isof great significance.This paper combines the company’s specific project and designs a AC/DC switch powermanagement chip which based on the primary side feedback technology. This paper firstlyintroduces the basic knowledge of AC/DC power control chip and primary side feedbacktechnology, the paper puts forward design objective. Then combined with the applicationcircuit diagram and system of chip, the paper introduces the working principle of chip system,and expounds two work modes of chip, constant voltage mode and constant current mode.Then, the paper analyzes and designs internal main circuit module, including Bandgap,Regulator, External triode base driver circuit, Oscillator, Auto-adapt peak current limitingcircuit and Cable_compensation circuit. Among them, Bandgap provides a reference voltageto the chip; Regulator will convert the reference voltage to work required voltage; Externaltriode base driver circuit can precisely control external transistor’s base current; In theoscillator circuit, it increases the primary inductance compensation circuit and improves theprecision of the constant current output; In the auto-adapt peak current limiting circuit, it usesan algorithm to fix the inductance coil peak current and improves the precision of the constantcurrent output; Cable_compensation circuit compensates for the internal reference voltage andimproves the precision of the constant voltage output. Finally, in Cadence, Hspice software, ituses huahong BCD350process to make a function simulation, the simulation results showthat various data is able to achieve the anticipated design objective, all kinds of protectionfunction can realize.