The Study Of TL431Reliability In Switch-Mode Power Supplies

TL431, which is produced by the company of Texas Instruments (TI), is a good thermal stability of three-terminal adjustable shunt. Because it has many advantages, such as, high stability, the diversification of links means, low price and so on. So it is widely included in precis switch power supply for Single Chip Micyoco (SCM) or the precision of linear regulated power supply. For many application, it can substitute for Zener diode, and also forms the comparator, supply voltage monitor, time delay circuit, precision constant current source circuit, etc. Today, electronic information industry at a high speed, the men pay more attention to the reliability and manufacturing costs of the electronic devices. In many similar electronic devices, TL431is always considered as the main selection of excellent quality and reasonable price devices. It is very important significance to study the reliability of TL431in the switching power supply.This thesis mainly investigates the reliability and production cost of TL431, designs the novel IC circuit and smaller layout in size of TL431. So it can be flexible in usage convenient, high dependability, even less expensive, and improves the yield for the manufacturer.This thesis is composed of five chapters. The first chapter is an introduction that introduces the relevant study of TL431device in the academic world, base design parameters of TL431device as well as the application in the switching power supply. The second chapter analyzes the principle and characteristic of the IC circuit in detail. Basing on the way of circuit module, it is analyzed and researched, especially, mainly studied the band gap reference circuit, figured out the value from the error sources(such as:base-emitter voltage spread and matching of transistor, tolerances and matching of resistor In order to solve these error sources and get high-precision components, the compact binary-weighted resistor trim schemes were used to compensate the error. The chip prober data is obtained before trimming and after and validate that the schemes is feasibility. The third chapter is about the layout of TL431. At the layout design, there adopts the2μm36V bipolar design technology and design the new layout of TL431, it deeply analysis the Electro Static Discharge (ESD), how it destroys the circuit and have designed the ESD protection circuit. The forth chapter introduce the Hospice software which is the electronic simulation software. The characteristics parameter of TL431device is simulated by the Hospice. Simulation results show that they meet the design requirements. The conclusion is given in the fifth chapters.