【文章內(nèi)容簡介】 ts of this cost is increasingly move to the low output power side, the switching power supply provides a broad space for development. The direction of its development is the highfrequency switching power supply, high frequency switching power supply miniaturization, and switching power supply into a wider range of application areas, especially in hightech fields, and promote the miniaturization of hightech products, light of. In addition, the development and application of the switching power supply in terms of energy conservation, resource conservation and environmental protection are of great significance. classification Modern switching power supply, there are two: one is the DC switching power supply。 the other is the AC switching power supply. Introduces only DC switching power supply and its function is poor power quality of the original ecopower (coarse) such as mains power or battery power, converted to meet the equipment requirements of highquality DC voltage (Varitronix) . The core of the DC switching power supply DC / DC converter. DC switching power supply classification is dependent on the classification of DC / DC converter. In other words, the classification of the classification of the DC switching power supply and DC/DC converter is the classification of essentially the same, the DC / DC converter is basically a classification of the DC switching power supply. DC /DC converter between the input and output electrical isolation can be divided into two categories: one is isolated called isolated DC/DC converter。 the other is not isolated as nonisolated DC / DC converter. 12 Isolated DC / DC converter can also be classified by the number of active power devices. The single tube of DC / DC converter Forward (Forward), Feedback (Feedback) two. The doublebarreled doublebarreled DC/ DC converter Forward (Double Transistor Forward Converter), twintube feedback (Double Transistor Feedback Converter), PushPull (Push the Pull Converter) and halfbridge (HalfBridge Converter) four. Four DC / DC converter is the fullbridge DC / DC converter (FullBridge Converter). Nonisolated DC / DC converter, according to the number of active power devices can be divided into singletube, double pipe, and four three categories. Single tube to a total of six of the DC / DC converter, stepdown (Buck) DC / DC converter, stepup (Boost) DC / DC converters, DC / DC converter, boost buck (Buck Boost) device of Cuk the DC / DC converter, the Zeta DC / DC converter and SEPIC, the DC / DC converter. DC / DC converters, the Buck and Boost type DC / DC converter is the basic buckboost of Cuk, Zeta, SEPIC, type DC / DC converter is derived from a single tube in this six. The twintube cascaded doublebarreled boost (buckboost) DC / DC converter DC / DC converter. Four DC / DC converter is used, the fullbridge DC / DC converter (FullBridge Converter). Isolated DC / DC converter input and output electrical isolation is usually transformer to achieve the function of the transformer has a transformer, so conducive to the expansion of the converter output range of applications, but also easy to achieve different voltage output , or a variety of the same voltage output. Power switch voltage and current rating, the converter39。s output power is usually proportional to the number of switch. The more the number of switch, the greater the output power of the DC / DC converter, four type than the two output power is twice as large, singletube output power of only four 1/4. A bination of nonisolated converters and isolated converters can be a single converter does not have their own characteristics. Energy transmission points, oneway transmission and twoway transmission of two DC / DC converter. DC / DC converter with bidirectional transmission function, either side of the transmission power from the power of lateral load power from the loadlateral side of the 13 transmission power. DC / DC converter can be divided into selfexcited and separately controlled. With the positive feedback signal converter to switch to selfsustaining periodic switching converter, called selfexcited converter, such as the the Luo Yeer (Royer,) converter is a typical pushpull selfoscillating converter. Controlled DC / DC converter switching device control signal is generated by specialized external control circuit. the switching power supply. People in the field of switching power supply technology side of the development of power electronic devices, while the development of the switching inverter technology, the two promote each other to promote the switching power supply annual growth rate of more than two digits toward the light, small, thin, lownoise, high reliability, the direction of development of antijamming. Switching power supply can be divided into AC / DC and DC / DC two categories, AC / AC DC / AC, such as inverters, DC / DC converter is now modular design technology and production processes at home and abroad have already matured and standardization, and has been recognized by the user, but AC / DC modular, its own characteristics make the modular process, encounter more plex technology and manufacturing process. Hereinafter to illustrate the structure and characteristics of the two types of switching power supply. Selfexcited: no external signal source can be selfoscillation, pletely selfexcited to see it as feedback oscillation circuit of a transformer. Separate excitation: entirely dependent on external sustain oscillations, excited used widely in practical applications. According to the excitation signal structure classification。 can be divided into pulsewidthmodulated and pulse 14 amplitude modulated two pulse width modulated control the width of the signal