Circuit protection is mainly to protect the components in electronic circuits from being damaged by overvoltage, overcurrent, surge, electromagnetic interference, etc., while circuit protection devices provide protection for the circuit and chip of the product to ensure that the circuit appears Under abnormal conditions, the precision chips and components of the protected circuit will not be damaged.
Overvoltage, overcurrent, surge, electromagnetic interference, electrostatic discharge, etc. have always been the focus of circuit protection. Therefore, the mainstream circuit protection devices in the market are also mainly based on lightning protection/overvoltage/overcurrent/anti-static, etc., common Protection devices include ceramic gas discharge tubes, solid discharge tubes, transient suppression diodes, varistors, self-recovery fuses, and ESD electrostatic diodes. How can engineers choose the best circuit protection devices when selecting models?
1. You need to know what damage you want to prevent. Many times design engineers will consult Shuoke Electronics about surge protection devices, but they don’t know what damage they want to avoid. Therefore, you have to do The first thing is to determine whether to prevent direct lightning strikes, secondary shocks (as described in the IEC61000-4-5 standard), or electrostatic discharge (as described in the IEC61000-4-2 standard). Once a decision is made, you can choose the appropriate circuit protection device.
2. Decide what results you want when the failure situation occurs. For example, you want to be able to tolerate fault conditions during operation and maintain operation during and after the fault conditions occur; only tolerate the fault conditions during shutdown, and then under
The device enters operation when it is powered on; or provides protection to make the device fail safely and does not need to operate after the failure ends? The circuit protection device you choose depends on the answers to these questions.
3. Regarding the "normal" and "abnormal" operating conditions, we need to make reasonable assumptions. For example, you cannot choose an overcurrent protection device that operates at 6A, but expect your design to operate normally at 5.99999A. This simply does not have enough margin. If your design consumes 6A current under normal operating conditions, you must choose an overcurrent protection device PTC resettable fuse that operates at 8A or higher current. Not only that, you must understand the maximum operating voltage, the maximum ambient temperature, as well as the fault voltage, fault current and fault duration in order to make the right choice.
4. It must be clear that any protection is impossible to achieve 100%. If you design to protect a specific event, there may always be some more serious events. For example, the hazards described in the telecommunications lightning specifications are much less serious than direct lightning strikes. It is possible to protect products from the hazards caused by direct lightning strikes, but it is very expensive to do so.
5. The circuit protection scheme should be planned at the beginning of the design. Although the circuit protection devices are much smaller than in the past, after the PCB design is completed, it is impossible to add circuit protection devices if there is not enough space.
With the development of science and technology, power/electronic products are becoming increasingly diversified and complicated, and the circuit structure and physical size of electronic products have become smaller and smaller. Circuit protection design in the early stages of the design cycle becomes more important. The selection of circuit protection and electronic protection devices may seem low priority, but the design should be started in the early stage to eliminate design problems and ensure the performance and reliability of your products.
For more knowledge about gas discharge tubes for switching components, please pay attention to the official website of Ruilongyuan Electronics: www.ruilon.com
