How to select the best circuit protection device in the circuit

- Jul 20, 2017-

The circuit protection is the main protection in electronic circuit components subjected to overvoltage and overcurrent, surge, electromagnetic interference is not damaged, the circuit protection device is to provide protection for the circuit and chip products, to ensure that in the case of abnormal circuit, circuit protection chip components are not damaged, precision. Overvoltage, overcurrent, surge, electromagnetic interference, electrostatic discharge protection circuit has been the focus, therefore, the mainstream of circuit protection devices in the market but also to the lightning protection / overvoltage / overcurrent / ESD protection device etc, there is a common gas discharge tube, solid discharge tube, transient inhibition diode, varistors, self recovery fuse and ESD static diode etc.. How can the engineer select the best circuit protection device in the selection process?

Decide what you want when the fault occurs. For example, you want to be able to tolerate faults at run time and maintain operations during and after failures; only tolerate faults when they are off.

Once a device is powered into operation, or provides protection so that the device fails safely and does not need to be operational after the failure has been completed Your choice of circuit protection devices is dependent on the answers to these questions.

What is "normal" and "abnormal" operation, we need to make a reasonable assumption, for example, you can use a 6A under the action of overcurrent protection devices, and look forward to your design in the normal operation of the 5.99A, this is not a sufficient margin. If your design consumes 6A current in normal operation, you must select an over-current protection device, PTC self recovery fuse, operated at 8A or higher. Not only that, you have to know the maximum operating voltage, the maximum ambient temperature, and the fault voltage, fault current and fault duration to make the right choice.

It must be clear that any protection is not possible; 100%, if you design to protect a particular event, there are always more serious events that could happen. For example, the lightning specifications described in telecommunications are much less dangerous than direct lightning strikes, and it is possible to protect products against the hazards of direct lightning strikes, but this is very expensive.

At the beginning of the design, it is necessary to plan the circuit protection scheme. Although the circuit protection devices are much smaller than before, it is impossible to add circuit protection devices if there is not enough space after the design of the PCB.

With the development of science and technology, electrical / electronic products have become increasingly diversified and complex, the physical size of the circuit structure and the electronic products become more and more small, performed early in the design cycle becomes more and more important circuit protection design. The selection of circuit protection and electronic protection devices may not seem to be of high priority, but design should be started early to eliminate design problems and to ensure the performance and reliability of your products.

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