The main purpose of circuit protection is to protect the components of electronic circuits from being damaged by overvoltage, overcurrent, surge, electromagnetic interference, etc. The circuit protection devices provide protection for the circuits and chips of the products, and ensure that the precision chips and components of the protected circuits are not damaged in the case of abnormal circuits. Over voltage, over current, surge, electromagnetic interference, such as electrostatic discharge is always the key point of the circuit protection, therefore, the market mainstream in lightning protection circuit protection device/over voltage/overcurrent/anti-static is given priority to, such as common protection devices are gas discharge tube, solid discharge tube, transient suppression diodes, varistor, static self recovery fuse and ESD diode, etc. How can engineers choose the best circuit protection device when selecting the type?

1. Do you want to know what you want to prevent the damage of many design engineers will consult pegatron kay electronic question about surge protection devices, but they don't know what I want to avoid causing damage, therefore, the first thing you have to do is to determine to prevent direct lightning, secondary impact (such as IEC61000-4-5 standard description), or electrostatic discharge (as described in IEC61000-4-2 standard). Once the decision is made, you can choose the appropriate circuit protection device.

2. Decide what you want when something goes wrong. For example, you want to be able to withstand a failure at run time and stay in operation during and after the failure; Only when the fault is turned off can the fault be tolerated, and then the next time the device is powered on, it goes into operation. Or provide protection to allow the device to fail safely and not need to operate after the failure is over? The circuit protection device you choose depends on the answer to these questions.

3. We need to make reasonable assumptions about what is "normal" and "abnormal" in the operation. For example, you cannot choose A over-current protection device that operates under 6A, and your design is expected to operate normally under 5.9999999 A, which is not enough margin. If your design consumes 6A current during normal operation, you must select a PTC self-recovery fuse that operates under 8A or higher current. In addition, you must understand the maximum operating voltage, maximum ambient temperature, and fault voltage, fault current, and fault duration before you can make the right choice.

4. It must be clear that no protection is possible to achieve 100%. If you design to protect a specific event, however, there will always be some more serious events. For example, the telecommunications lightning specification describes hazards much less severe than direct lightning strikes, and it is possible to protect products from direct lightning strikes, but it is expensive to do so.

5. Circuit protection plans should be planned at the beginning of the design. Although the circuit protection devices are much smaller than before, it is impossible to add circuit protection devices without sufficient space after the PCB design is completed.

With the development of science and technology, electric power/electronic products are becoming more and more diversified and complicated, and the physical size of the circuit structure and electronic products is becoming smaller and smaller. The selection of circuit protection and electronic protection devices may seem like a low priority, but design should start early to eliminate design problems and ensure the performance and reliability of your products.