HOW TO PREVENT A POWER TRANSISTOR FROM OVERHEATING
In addition to meeting electrical requirements, a successful circuit design must meet thermal requirements. This insures that the circuit will not fail prematurely due to excessive temperature and that it will not excessively raise the temperature of neighboring circuits and cause them to fail. If thermal analysis is not included in the overall system design, the individual circuits may work properly on the bench but fail when they are placed together in an enclosure. This chapter shows a fast and simple way to estimate component temperatures. It also shows how to specify a heat sink that will keep the temperature of a device at a safe level. This technique will not give the precise results obtainable using sophisticated thermal modeling tools, but it will allow you to quickly make rough thermal estimates as you consider different approaches during the early phase of a design.
Most experienced engineers have seen good electrical designs get scrapped because they were thermally impractical, so it is common for them to ask candidates to solve simple heat transfer problems during interviews. This chapter will reinforce your intuitive understanding of heat transfer, show you how to apply it in the workplace, and show examples of problems typically asked during interviews.
We begin by reviewing steady-state heat transfer problems. Next, we show how to use data provided by manufacturers of electronic components and heat sinks to keep ...