Various protection circuit settings for internal devices of DC switching power supply
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 is inseparable from a reliable power supply. Therefore, DC switching power supplies have begun to play an increasingly important role, and have entered various Various electronic and electrical equipment fields, program-controlled switches, communications, electronic testing equipment power supply, control equipment power supply, etc. have widely used DC switching power supply [1-3]. 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 mount technology and other technologies, switching power supply technology is constantly innovating, which is the foundation for DC switching. The power supply provides a wide range of development space. However, due to the complex control circuit in the switching power supply, the ability of transistors and integrated devices to withstand electrical and thermal shocks is poor, which brings great inconvenience to users during use. In order to protect the safety of the switching power supply itself and the load, according to the principle and characteristics of the DC switching power supply, the overheat protection, overcurrent protection, overvoltage protection and soft start protection circuits are designed.
The principle and characteristics of switching power supply
working principle
DC switching power supply is composed of input part, power conversion part, output part and control part. The power conversion part is the core of the switching power supply, which performs high-frequency chopping on the unsteady DC and completes the conversion function required for the output. It is mainly composed of switching transistors and high frequency transformers. Figure 1 shows the schematic diagram and equivalent functional block diagram of a DC switching power supply, which is composed of a full-wave rectifier, a switching tube V, an excitation signal, a freewheeling diode Vp, an energy storage inductor and a filter capacitor C. In fact, the core part of a DC switching power supply is a DC transformer.
features
In order to meet the needs of users, major switching power supply manufacturers at home and abroad are committed to synchronously developing new high-intelligence components, especially by improving the loss of the secondary rectification device, and on the power ferrite (Mn-Zn) material Increase scientific and technological innovation to improve the high magnetic performance obtained at high frequency and large magnetic flux density. At the same time, the application of SMT technology has made great progress in switching power supplies. Components are arranged on both sides of the circuit board to ensure the switching power supply. Light, small and thin. Therefore, the development trend of DC switching power supply is high frequency, high reliability, low consumption, low noise, anti-interference and modularization.
The disadvantage of DC switching power supply is that there is relatively serious switching interference, and the ability to adapt to harsh environments and sudden failures is weak. Due to the gap between domestic microelectronics technology, production technology of resistive capacitor devices and magnetic material technology and some technologically advanced countries, the production technology of DC switching power supply is difficult, maintenance troublesome and costly.
