Various protection circuit designs for internal devices of DC switching power supplies
DC switching power supply internal devices of various protection circuit design with the development of science and technology, power electronic equipment and people's work, life is increasingly close, and electronic equipment are inseparable from a reliable power supply, so the DC switching power supply began to play an increasingly important role, and one after another into a variety of electronic, electrical equipment, program-controlled switches, communications, electronic testing equipment power supply, power control equipment, etc. have been widely used DC switching power supply [1.3]. DC switching power supply has been widely used [1-3]. At the same time, with many high-tech, including high-frequency switching technology, soft-switching technology, power factor correction technology, synchronous rectification technology, intelligent technology, surface mounting technology and other technology development, switching power supply technology is constantly innovating, which provides a wide range of DC switching power supply development space. However, due to the complexity of the control circuit in the switching power supply, the transistors and integrated devices have poor ability to withstand electric and thermal shocks, which brings great inconvenience to the users in the process of using. In order to protect the switching power supply itself and the safety of the load, according to the principle and characteristics of the DC switching power supply, the design of overheating protection, overcurrent protection, overvoltage protection and soft-start protection circuit.
2 Principle and characteristics of switching power supply
Working Principle Principle of operation
DC switching power supply consists of input part, power conversion part, output part and control part. The power conversion part is the core of the switching power supply, which carries out high-frequency chopping on the non-stable DC and completes the conversion function required for the output. It is mainly composed of switching transistors and high-frequency transformers. Figure 1 draws the schematic and equivalent block diagram of the DC switching power supply, which is composed of a full-wave rectifier, a switching tube V, an excitation signal, a current-renewal diode Vp, an energy-storage inductor and a filtering capacitor C. In fact, the core part of the DC switching power supply is a DC transformer.
2.2 Features
In order to adapt to the needs of users, the major domestic and foreign switching power supply manufacturers are committed to the simultaneous development of new highly intelligent components, especially by improving the loss of the secondary rectifier parts, and increase scientific and technological innovation in power ferrite (Mn-Zn) materials to improve the high magnetic properties obtained at high frequencies and large flux density, while the application of SMT technology has made significant progress in switching power supplies, the Components are arranged on both sides of the board to ensure that the switching power supply is 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 the existence of more serious switching interference, adapt to harsh environments and sudden failure of the ability to be weak. Due to the domestic microelectronics technology, capacitive resistance device production technology and magnetic material technology and some technologically advanced countries there is still a certain gap, so the production of DC switching power supply technical difficulties, maintenance trouble and high cost.
