Preface（序）

It’s well known that modern industrial，agricultural developments and daily life of people rely heavily on the latest electronic development in the form of automation and information. With the safe and reliable working of electrical appliance and equipment， people are getting increasingly benefit with the ever-developing electronic and electrical products. Owing to the fact that the change of external environment and the deterioration of internal electronic and electrical component characteristics， electrical appliances and equipments should be designed with very good self protection ability， which can eliminate the faulty conditions and enhance the long term of the electronic and electrical appliances.

Nowadays， billion of electronic and electrical equipments are evolved everyday in both China domestic market and oversea markets， circuit protection are quietly contributing to helping the electronic and appliance to enhance their reliability. Inadequate， improper and ignored circuit protection will result the poor reliability， abnormal operation and increase maintenance cost and more seriously， safety issues.Thus， circuit protection is one of the importance aspects in an enterprise and design engineers should have equipped the right level of circuit protection knowledge.

Circuit protection is so important to a company making the electronic and electrical products. A lot of Chinese domestic manufacturers are paying high attention to this so that the design， manufacture， after-sales and maintenance will have a good reflection to the image of the manufacturer. However， some of the manufacturers are deliberately removing the required circuit protection components because of the cost consideration. They have to pay the price for improper product quality and reliability. In fact， the ultimate result is the tarnish of their image and the potential hazard of their devices.

Also， to the design engineers， technicians and senior managements of an enterprise， the circuit protection concept and knowledge is a necessary step to raise the overall quality of their products. In this IT world， the circuit protection concept， compared to the integrated circuits， computer and networking， is a bit “traditional”. The circuit protection knowledge is somewhat “fragmented” in which there is a lack of complete course or knowledge in that area so that some younger generation will find it difficult to learn from academic institutes. Some young designers have a good circuit design in the theoretical world， however， their design doesn’t work in the reality world. One of the reasons for this is the circuit protection is not yet well designed into the system.

This book shows a systematic way on the circuit protection techniques including ESD， surge， electrical transient and overcurrent threats， with detail discussion on the function and operational theory of the TVS， MOV， GDT， Fuse and PTC devices which is good for electronic and electrical equipment designers. To make this book for practical， it documents some of the live applications such as IPTV， STB， telecommunication network， mobile phones， LED lightings， automotive electronics and portable medical devices.

The authors of this book have extensive practical， design and circuit applications experience in circuit protection in different market segments. The content of this book will start from some simple idea to in-depth design real cases. And we believe that this book will provide lots of help to electronic and electrical designers. Last but not least， we hope the readers to enjoy reading this book and think about the tradeoff between long term reliability and cost consideration with the introduction of circuit protection.

TeddyTo

LittelfuseInc.

1thDec.2010