Principles and Characteristics of Switching Power Supply Protection Circuits
With the development of science and technology, the relationship between power electronic equipment and people's work and life is becoming increasingly close, and electronic equipment cannot do without reliable power sources. Therefore, DC switching power supplies are playing an increasingly important role and have successively entered various fields of electronic and electrical equipment. DC switching power supplies have been widely used in program-controlled switches, communication, electronic detection equipment power supplies, control equipment power supplies, etc. At the same time, with the development of many high-tech technologies, including high-frequency switching technology, soft switching technology, power factor correction technology, synchronous rectification technology, intelligent technology, surface installation technology, etc., switching power supply technology is constantly advancing, providing a wide range of development space for DC switching power supplies. However, due to the complexity of the control circuit in switch mode power supplies, transistors and integrated devices have poor resistance to electrical and thermal shocks, which causes great inconvenience to users during use. In order to protect the switching power supply itself and the load, based on the principles and characteristics of DC switching power supply, overheat protection, overcurrent protection, overvoltage protection, and soft start protection circuits have been designed.
The principle and characteristics of switch mode power supply
working principle
A DC switching power supply consists of an input part, a power conversion part, an output part, and a control part. The power conversion part is the core of the switching power supply, which performs high-frequency chopping on unstable DC and completes the required conversion function for output. It is mainly composed of a switching transistor and a high-frequency transformer. Figure 1 shows the schematic and equivalent schematic diagram of a DC switching power supply, which consists of a full wave rectifier, a switching tube V, an excitation signal, a freewheeling diode Vp, an energy storage inductor, and a filtering capacitor C. In fact, the core part of a DC switching power supply is a DC transformer
feature
In order to meet the needs of users, major switch mode power supply manufacturers at home and abroad are committed to synchronously developing new highly intelligent components, especially by improving the losses of secondary rectification devices and increasing technology in power ferrite (Mn Zn) materials to improve high magnetic performance at high frequencies and high magnetic flux densities. At the same time, the application of SMT technology has made significant progress in switch mode power supplies, arranging components on both sides of the circuit board to ensure their lightweight, small, and thin design. Therefore, the development trend of DC switching power supplies is high frequency, high reliability, low power consumption, low noise, anti-interference, and modularization.
