In the design of electronic circuits, it is often necessary to face a variety of situations that may lead to circuit damage, such as overvoltage, overcurrent, surge and so on. Transient changes in device load, such surges and voltage transients encountered by electrical devices during operation may cause device damage. At this time, the circuit protection element is required to provide adequate protection for the circuit.

● The importance of circuit protection

With the damage of today's more integrated circuit boards will cause a lot of unnecessary trouble, so protection measures are particularly important to prevent circuit damage.

For example, large instantaneous peak voltages generated at start and stop in on-board equipment require the use of overvoltage protection elements in the adapter of the accompanying product. For example, communication equipment is often troubled by surge, surge includes surge voltage and surge current, is a very fast rising speed, a very short duration of the peak pulse, can exceed the peak value of the device stability in an instant. This requires a combination of multiple voltage transients and surge protection devices to form a multistage protection circuit to ensure that nothing goes wrong.

Of course, in addition to preventing accidental damage to the circuit, it can be seen that the working voltage of the current semiconductor device IC is developing towards a lower and lower trend, and the protection of its circuit can also reduce the loss of energy consumption, reduce the occurrence of circuit heating, and extend the service life of the IC.

The development of integrated circuits has promoted the increasing diversification and complexity of electronic circuit products, followed by more situations that may harm the circuit, and circuit protection has become more and more important.

● Devices needed for different circuit protection

Overvoltage protection is one of the essential links in the circuit, which mainly uses the potential difference to achieve the effect of circuit protection. When the voltage in the circuit exceeds the specified value, the internal circuit structure of the overvoltage protection device will produce a certain potential difference with the circuit, so that the circuit can achieve protection through impedance change.

The internal current and voltage protection device of the overvoltage protection device will disconnect the circuit and prevent the current from further flowing to the protected appliance or equipment to achieve the effect of protecting the appliance or equipment. Typical overvoltage protection devices are varistor and transient suppressor TVS. Varistor can be said to be the most used overvoltage protection device, low cost, good effect and high cost performance. The ns response speed makes it capable of overvoltage protection in most cases.

For overcurrent problems, various types of fuse or eFuse schemes are usually used. Polymer fuses limit flow by increasing internal resistance and have restorable properties; The glass tube and the plate type are directly broken and switched on; eFuse can directly track and control current traffic.

Some electrostatic protection components are also involved in circuit protection, especially if ESD protection is not set in a highly integrated circuit, the high-voltage ESD impact generated by the interface connection will cause a large current peak directly into the integrated circuit, causing damage. To protect sensitive circuits from electrical overstress failures, ESD protection diodes should be connected to each signal line between the interface connector and the integrated circuit, with different interface speeds corresponding to different ESD diode capacitance values.

In short, with the development of electronic circuits to a higher degree of integration, the demand for circuit protection is also changing, and circuit protection components are also upgrading step by step with the development trend.