How to understand the holding current and tripping current of a resettable fuse

In modern electronic equipment, the resettable fuse (Polyfuse) is an important overcurrent protection component and is widely used in various circuits. Understanding the holding current and tripping current of a resettable fuse is of great significance for the correct selection and use of this component and ensuring the safe operation of the equipment. This article will focus on the topic of "holding current and tripping current of self-restoring fuses" to analyze related concepts and their applications in detail.

Resettable fuses, also known as polymer fuses, are overcurrent protection components based on polymer materials. When the current exceeds the set value, the polymer material inside the fuse will heat up rapidly, causingresistanceSignificant increase, thereby limiting the flow of current and protecting the circuit from damage. After the fault current is eliminated, the polymer cools, the resistance returns to a lower level, and the fuse automatically returns to the conducting state without replacement.

Hold Current refers to the maximum current value that a resettable fuse can continue to carry under normal operating conditions. Below this current value, the fuse will not trigger the protection mechanism and maintain a low resistance state to ensure normal operation of the circuit. When selecting a fuse, the holding current should be higher than the normal operating current of the circuit to avoid false triggering of the protection.

Trip Current, also known as trigger current, means that when the current exceeds this value, the material inside the fuse heats up rapidly and the resistance rises sharply, thereby limiting the flow of current and playing a protective role. Trip current is usually higher than holding current and is a key parameter for fuse protection circuits.

There is a certain gap between the holding current and the tripping current to ensure that the fuse will not malfunction during normal operation and can quickly protect the circuit in the event of abnormal overcurrent.一般情况下，跳闸电流约为保持电流的1.5到2倍，具体数值视产品型号和规格而定。

When selecting a self-restoring fuse, the holding current and tripping current need to be reasonably determined based on the actual operating current of the circuit and the maximum possible overcurrent condition. The holding current should be slightly higher than the normal operating current, and the trip current should be lower than the maximum overcurrent the circuit may withstand. In addition, factors such as voltage level, response time and size need to be considered.

Compared with traditional blowout fuses, resettable fuses do not need to be replaced, reducing maintenance costs. Its fast response characteristics and automatic recovery capabilities improve the reliability and safety of the circuit. It is widely used in USB interface, battery protection, power adapter and other fields.

Some users tend to confuse holding current and tripping current, mistakenly believing that the larger the holding current, the better. In fact, too high a holding current may cause protection failure, while too low a holding current may cause malfunction. Understanding the difference between the two will help you to properly select and use resettable fuses.

The holding current and tripping current of the resettable fuse are its core parameters, which directly affect the safety protection effect of the circuit. The holding current represents the maximum carrying current during normal operation, and the tripping current is the starting point of the protection action. Proper understanding and application of these two parameters can help improve the safety and reliability of electronic equipment. During the selection and design process, it is recommended to combine the specific circuit requirements and comprehensively consider the holding current and tripping current to ensure that the resettable fuse can exert the best protection effect.