Industry News

Circuit protection and electronic protection device purchasing knowledge

2020-05-19
With the development of science and technology, power/electronic products are increasingly diverse and complex, and the circuit structure and physical size of electronic products are becoming smaller and smaller. The selection of circuit protection and electronic protection devices may not seem like a high priority, but design should be started early to eliminate design problems and ensure the performance and reliability of your product.

Circuit protection is mainly to protect the components in the electronic circuit from damage in the case of overvoltage, overcurrent, surge, electromagnetic interference, etc. Circuit protection device is to provide protection for the product's circuit and chip, to ensure that in the case of abnormal circuit, the protected circuit of precision chips, components are not damaged. 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 the engineer select 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 you have made your decision, you can choose the appropriate circuit protector.

2. Decide what you want when a failure occurs. For example, you want to be able to tolerate failure situations at run time and remain operational during and after a failure situation. The failure condition is tolerated only at shutdown and then enters operation the next time the device is energized; Or provide protection to enable the device to fail safely and not be required to operate after the failure has ended? The circuit protection device you choose depends on the answer to these questions.

3. We need to make reasonable assumptions about what "normal" and "abnormal" operating conditions are. For example, if you cannot choose an overcurrent protection device operating under 6A, there is simply not enough margin to expect your design to work properly under 5.99999A. If your design consumes 6A current in normal operation, you must use an overcurrent protection device PTC self-restoring fuse operating at 8A or higher. Not only that, you must know the maximum operating voltage, maximum ambient temperature, failure voltage, failure current, and failure duration to make the right choice.

4. It is important to be aware that any protection is impossible to achieve 100%. If you design protection for a particular event, there is always the possibility that something more serious will happen. For example, the hazards described in the telecommunications lightning code are much less severe than direct lightning strikes, and it is possible to protect products against direct lightning strikes, but doing so is very expensive.

5. Circuit protection scheme should be planned at the beginning of circuit design. Although circuit protection device is much smaller than in the past, it is impossible to add circuit protection device without sufficient space after PCB design.

With the development of science and technology, power/electronic products are increasingly diverse and complex, and the circuit structure and physical size of electronic products are becoming smaller and smaller. The selection of circuit protection and electronic protection devices may not seem like a high priority, but design should be started early to eliminate design problems and ensure the performance and reliability of your product.