【正文】 lso easy to achieve different voltage output , or a variety of the same voltage output. Power switch voltage and current rating, the converter39。 can be divided into pulsewidthmodulated and pulse amplitude modulated two pulse width modulated control the width of the signal is frequency, pulse amplitude modulation control signal amplitude between the same effect are the oscillation frequency to maintain within a certain range to achieve the effect of voltage stability. The winding of the transformer can generally be divided into three types, one group is involved in the oscillation of the primary winding, a group of sustained oscillations in the feedback winding, there is a group of load winding. Such as Shanghai is used in household appliances art technological production of switching power supply, 220V AC bridge rectifier, changing to about 300V DC filter added to the collector of the switch into the transformer for high frequency oscillation, the feedback winding feedback to the base to maintain the circuit oscillating load winding induction signal, the DC voltage by the rectifier, filter, regulator to provide power to the load. Load winding to provide power at the same time, take up the ability to voltage stability, the principle is the voltage output circuit connected to a voltage sampling device to monitor the output voltage changes, and timely feedback to the oscillator circuit to adjust the oscillation frequency, so as to achieve stable voltage purposes, in order to avoid the interference of the circuit, the feedback voltage back to the oscillator circuit with optocoupler isolation. technology developments The highfrequency switching power supply is the direction of its development, highfrequency switching power supply miniaturization, and switching power supply into the broader field of application, especially in hightech fields, and promote the development and advancement of the switching power supply, an annual more than twodigit growth rate toward the light, small, thin, low noise, high reliability, the direction of the antijamming. Switching power supply can be divided into AC / DC and DC / DC two categories, the DC / DC converter is now modular design technology and production processes at home and abroad have already matured and standardized, and has been recognized by the user, but modular AC / DC, because of its own characteristics makes the modular process, encounter more plex technology and manufacturing process. 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. The switching power supply applications in power electronic devices as diodes, IGBT and MOSFET. SCR switching power supply input rectifier circuit and soft start circuit, a small amount of applications, the GTR drive difficult, low switching frequency, gradually replace the IGBT and MOSFET. Direction of development of the switching power supply is a highfrequency, high reliability, low power, low noise, jamming and modular. Small, thin, and the key technology is the high frequency switching power supply light, so foreign major switching power supply manufacturers have mitted to synchronize the development of new intelligent ponents, in particular, is to improve the secondary rectifier loss, and the power of iron Oxygen (Mn? Zn) materials to increase scientific and technological innovation in order to improve the magic properties of high frequency and large magic flux density (Bs), and capacitor miniaturization is a key technology. SMT technology allows the switching power supply has made considerable progress, the arrangement of the ponents in the circuit board on both sides, to ensure that the light of the switching power supply, a small, thin. Highfrequency switching power supply is bound to the traditional PWM switching technology innovation, realization of ZVS, ZCS softswitching technology has bee the mainstream technology of the switching power supply, and a substantial increase in the efficiency of the switching power supply. Indicators for high reliability, switching power supply manufacturers in the United States by reducing the operating current, reducing the junction temperature and other measures to reduce the stress of the device, greatly improve the reliability of products. Modularity is the overall trend of switching power supply, distributed power systems can be posed of modular power supply, can be designed to N +1 redundant power system, and the parallel capacity expansion. For this shorting of the switching power supply running noise, separate the pursuit of high frequency noise will also increase, while the use of part of the resonant converter circuit technology to achieve high frequency, in theory, but also reduce noise, but some The practical application of the resonant converter technology, there are still technical problems, it is still a lot of work in this field, so that the technology to be practical. Power electronics technology innovation, switching power supply industry has broad prospects for development. To accelerate the pace of development of the switching power supply industry in China, it must take the road of technological innovation, out of joint production and research development path with Chinese characteristics and contribute to the rapid development of China39。s electronic information industry power mode. Bipolar transistor made of 100kHz, 500kHz power MOSFET made, though already the practical switching power supply is currently available on the market, but its frequency to be further improved. To improve the switching frequency, it is necessary to reduce the switching losses, and to reduce the switching losses, the need for highspeed swit