1. It should be noted that in the early stages of understanding the normal working current of a product, it is often not particularly accurate. Because an electronic engineer often amplifies the parameters naturally and habitually when selecting device models, such as the actual measurement value being 0.42A, but habitually setting it at 0.5A, and may even consider it safe to perform some amplification, setting it at 0.8A. This is a common practice for electronic engineers when selecting self restoring fuses. 2. For some products, when the current is not constant, the maximum current of the product is often taken as the normal working current. Therefore, it is necessary to understand at this time: A. The current at which the product operates for a long time (usually); B. The duration of the maximum current; C. The frequency (time interval) of the maximum current repetition. When the maximum peak current of the product is not very large (less than twice), the duration is not ve
The network TV converter is a necessary equipment for watching network TV, which is increasingly favored by young people. However, due to the transmission of network signals through coaxial cables and long-distance communication, there are safety issues in applications such as installation wiring errors, short circuits, ESD damage, induced high voltage damage, lightning damage, etc. It is necessary to design overcurrent protection and overvoltage protection, To ensure the service life and reliability of network TV converter equipment. Among various protection circuits, the protection circuit with the least components, the lowest cost, and the highest reliability is the PTC self recovery fuse element and the circuit that PTC cooperates with varistors or TVS tubes. PTC self recovery fuse, also known as ten thousand fuse or self reset overcurrent protector, is also known as polymer polymer switch. In general, a PTC overcurrent protector can be combined with a varistor or TVS tube. C
Disinfection cabinets have been applied in public places such as hotels, restaurants, industrial canteens, Chinese and Western restaurants, and canteens of enterprises and institutions, and have gradually entered modern homes. Disinfection cabinets have gradually become an essential disinfection tool in daily life. While people value its practicality, its safety, reliability, and stability are also issues of concern. The disinfection methods for cupboards are mostly thermal infrared or ultraviolet. By driving infrared or ultraviolet emission tubes with high frequency and high voltage, this high-frequency and high voltage driving circuit is prone to burning out the driving transistor due to high current and temperature. This puts forward high requirements for the design of engineers. To ensure the reliability and safety of the circuit, it is necessary to design overcurrent and overheating protection circuits. Especially when there is no installed infrared emission tube or ultraviol
Rolling gate is a widely used door in modern factories and shops, which can not only automatically lift and manually switch, but also be remotely operated. The core of this type of door is to control the forward and reverse rotation of the small motor to achieve its function. The rolling gate is driven by a small motor, which not only often gets stuck and cannot move, but also causes the small motor to stall, overload, and burn out due to unstable voltage, high temperature, high humidity, and other reasons. So small motors must be designed with protective circuits to ensure their reliability and stability. There are various methods for protecting small motors. Previously, bimetallic temperature controllers were often used for protection. When the coil temperature of the small motor increased, the circuit would be disconnected, and when the temperature decreased, the circuit would be reconnected. If the power supply was not cut off, the motor would continue to be powered on and wo
Power transformers are commonly used components in electronic products and are widely used due to their simplicity and ease of manufacture. There are two types of transformers: step-up transformers and step-down transformers (excluding impedance transformers and line matching transformers). They are also called linear transformers because they increase or decrease the original AC voltage proportionally and output it to the load for power supply. In application, step-up transformers are mainly used in instruments and meters; For the power supply of electronic products, the majority are actually step-down transformers. Structurally, the transformer is composed of stacked silicon steel sheets and primary coils. The coil is mostly wound with enameled copper wire, and now it is also used with enameled aluminum wire. For step-down transformers, their characteristics are: the primary input is 220V, the secondary output is low-voltage, the secondary current is small, the secondary curren
Fingerprint door lock is a widely used door lock product in modern homes, factories, and enterprises. Its main functions include fingerprint recognition, storage, and opening and closing door locks. It is composed of fingerprint recognition and storage circuits, DSP data processing circuits, door opening and closing actuators, power circuits, and other components. Some door locks also require output signals to control the camera, open voice communication connections, and complete remote control functions. In this system, the power circuit, data transmission port circuit, and electromagnetic actuator of the control lock are prone to burning out the power circuit and DSP control system circuit due to unstable power supply voltage, lightning discharge, short circuit of installation wiring, etc. In severe cases, safety hazards such as burning out wires and causing wires to catch fire may occur. These interface points all require the design of ESD, overvoltage, overcurrent, and reverse