In our daily life and industrial production, electrical safety and circuit safety are very important things, so it is necessary for us to understand some knowledge about circuit protection devices.

Circuit protection components are widely used, and it is necessary to install circuit protection components wherever there is power, such as various household appliances, medical electronics, industrial equipment, and so on. Let's learn about several common circuit protection devices and their functions:

1. Discharge tube

Discharge tubes are often used in the first or first two stages of multistage protection circuits to discharge lightning transient overcurrent and limit overvoltage. Discharge tubes provide protection by limiting the voltage to a lower level. Discharge tubes are also divided into gas discharge tubes and solid discharge tubes. Gas discharge tubes are mainly composed of porcelain removal gas discharge tubes and glass gas discharge tubes, The selection of the type and model of discharge tubes in specific applications requires engineers to determine based on the protection level of the product's application port and relevant selection parameters.

2. Transient suppression diode

The avoiding state suppression diode can transform the high impedance between its two poles into a low impedance at a speed of 10 to the negative 12th power second, absorbing up to several kilowatts of surge power, keeping the voltage between the two poles at a predetermined value, effectively protecting precision components in electronic circuits from various surge pulses.

3. Varistor

Varistor is a voltage limiting protection device. In circuit protection, the nonlinear characteristics of the voltage sensitive anode are mainly utilized. When an overvoltage occurs between the two electrodes of the voltage sensitive anode, the varistor can clamp the voltage to a relatively fixed voltage value, thereby achieving protection for subsequent circuits.

4. Chip varistor

Patch varistors are mainly used to protect components and circuits from ESD generated in power supply, control, and signal lines.

5. PTC self recovery fuse

When a circuit operates normally, its resistance value is very small (voltage drop is very small). When an overcurrent occurs in the circuit and its temperature rises, the resistance value increases sharply by several orders of magnitude, reducing the current in the circuit below a safe value, thereby protecting subsequent circuits. After troubleshooting, the PPTC element quickly cools down and will return to its original low resistance state, allowing it to work again like a new PPTC element.

6. Inductance

The relationship between electromagnetism is believed to be clear to everyone. At the beginning of a circuit, when everything is still unstable, if there is a current flowing through the inductor, it will definitely generate an induced current that is opposite to the direction of the current (Faraday's law of electric collision and induction). After the circuit has been running for a period of time, everything is stable, and there is no change in the current. Therefore, electromagnetic induction will not generate current, and then it will be stable, There will be no sudden changes, thus ensuring the safety of the circuit. Just like a waterwheel, it initially rotated slowly due to resistance, but later gradually became peaceful. Inductance also has a function of supplying DC and impeding AC, which is rarely used.

7. Magnetic bead

Magnetic beads have a high resistivity and collision conductivity, which are equivalent to series connection of resistors and inductors. However, both the resistance and inductance values vary with frequency. They have better high-frequency filtering characteristics than ordinary electric and inductive devices, and exhibit resistance at high frequencies. Therefore, they can maintain a high impedance over a relatively wide frequency range, thereby improving the frequency modulation filtering effect, which has been used on Ethernet chips.

The above is the science popularization of the functions and types of circuit protection devices. Everyone must pay attention to the safety of using electricity in daily life and learn to use these circuit protection devices correctly!