How to choose the best circuit protection devices in a circuit?

      Circuit protection mainly protects the components in electronic circuits from damage under conditions such as overvoltage, overcurrent, surges, and electromagnetic interference. Circuit protection devices provide protection for the circuits and chips of products, ensuring that the precision chips and components of the protected circuits are not damaged in case of abnormal circuit conditions. Overvoltage, overcurrent, surge, electromagnetic interference, electrostatic discharge, etc. have always been the key points of circuit protection. Therefore, the mainstream circuit protection devices in the market are mainly lightning protection/overvoltage/overcurrent/anti-static, etc. Common protection devices include gas discharge tubes, solid discharge tubes, transient suppression diodes, varistors, self-resetting fuses, and ESD electrostatic diodes, etc. How can engineers choose the best circuit protection devices when making a selection?

1. You need to know what kind of damage you want to prevent. Many times, design engineers will consult Shuokai Electronics about surge protection devices, but they don't know what kind of damage they want to avoid. Therefore, the first thing you must do is to determine that you want to prevent direct lightning strikes and secondary impacts (as described in the IEC61000-4-5 standard). It is still electrostatic discharge (as described in the IEC61000-4-2 standard). Once you make a decision, you can choose the appropriate circuit protection device.

2.Decide what outcome you want when a malfunction occurs. For instance, you hope to be able to tolerate failure situations during operation and maintain operation during and after the occurrence of failure situations; It only tolerates fault conditions when turned off and then enters operation when the device is powered on next time. Or provide protection to ensure the device fails 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.We need to make reasonable assumptions about what constitutes "normal" and "abnormal" operating conditions. For instance, you cannot choose an overcurrent protection device that operates at 6A and expect your design to function normally at 5.99995A. There is simply not enough margin for this.

If your design consumes 6A current during normal operation, you must choose an overcurrent protection device, a PTC self-resetting fuse, which operates at 8A or higher current.

Not only that, you must understand the maximum operating voltage, the highest 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 no protection can be 100% guaranteed. Even if you design protection for a specific event, there is always a possibility that some more serious events will occur.

For instance, the hazards described in the telecommunications lightning code are much milder than those caused by direct lightning strikes. It is possible to protect products from the damage caused by direct lightning strikes, but doing so is extremely expensive.

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

With the development of science and technology, power/electronic products are becoming increasingly diverse and complex. The physical dimensions of circuit structures and electronic products are getting smaller and smaller. Therefore, it is even more important to carry out circuit protection design in the early stage of the design cycle.

The selection of circuit protection and electronic protection devices may seem to be of low priority, but design should be initiated in the early stage to eliminate design issues and ensure the performance and reliability of your products.