The direction of development of modern power electronics technology, from low-frequency technology to deal with the problem of traditional power electronics, to high-frequency technology to deal with the problem of modern power electronics direction change. In the application of power electronics technology and a variety of power systems, switching power supply technology are in the core position.

　　From 1955 the United States Royer (GH.Roger) invented self-excited oscillation push-pull transistor single transformer DC converter, is the realization of high-frequency conversion control circuit of the beginning of the switching power supply technology has become an indispensable power supply in the rapid development of the electronic information industry.

　　What makes switching power supply technology the core of modern power electronics technology? Its success relies only on its miniaturization and electronic equipment to facilitate the installation?

　　What is a switching power supply

　　Switching power supply is the abbreviation of switching regulated power supply, which generally refers to AC (alternating current) - DC (direct current) exchanger with AC voltage input and DC voltage output. The power switching tube inside the switching power supply works in the high-frequency switching state, and consumes very low energy itself, and the power supply efficiency can be up to 75% to 90%, which is twice as high as that of an ordinary linear regulated power supply.

　　What is the difference between switching power supply and linear power supply?

　　Simply put, the voltage regulation of linear power supply can be regarded as adjusting the resistance value, which is equivalent to adjusting the sliding varistor to make the voltage change, while the switching power supply is to make the voltage change by adjusting the frequency of the switch. At the same time, switching power supply and linear power supply, the cost of both with the increase in output power and growth, but the two growth rate is different.

　　Linear power supply cost at a certain output power point, but higher than the switching power supply.

　　Therefore, with the development of power electronics technology and innovation, so that the switching power supply technology continues to break through and innovation, this a cost problem, but let the switching power supply technology to the low output power end of the move, for the switching power supply provides a wide range of development space.

　　The working principle of switching power supply

　　Switching power supply is the use of modern electric power technology, control the switching transistor turn on and off time ratio, maintain a stable output voltage of a kind of power supply switching power supply by pulse width modulation (PWM) control (gold-oxygen half-field effect transistor) composition.

　　Switching power supply is composed of the main circuit, control circuit, detection circuit, auxiliary circuit four parts. Switching power supply, as the name suggests, is equivalent to a door here, one door allows the current to pass through, and the other door stops the current from passing through. So what is a door?

　　XED-15A12VWT internal structure diagram

　　Switching power supply some use silicon controlled, some use switching tube, these are relying on the base electrode, (switching tube) control pole (silicon controlled) coupled with a pulse signal to complete the conduction and cut-off, so that the electronic switching device is constantly 'on' and 'off', so that the electronic switching device to pulse modulation of the input voltage, thus realizing DC/AC, DC/DC voltage conversion, as well as adjustable output voltage and automatic voltage stabilization.

　　Advantages of switching power supply

　　Power electronic equipment and people's work, life is increasingly close relationship, and electronic equipment are inseparable from a reliable power supply, into the 80s after the computer fully realized switching power supply, to the 90s switching power supply successively into a variety of electronic and electrical fields.

　　Between the short ten years, switching power supply technology to rapidly occupy the core position of power electronic equipment, is it only because of the small size of the switching power supply?

　　In fact, the schematic diagram from the switching power supply can be understood: it does not use the bulky industrial frequency transformer, at the same time because the adjustment tube on the dissipation of power is greatly reduced, thus eliminating the need for larger heat sinks. This makes the switching power supply smaller and lighter. However, the biggest advantage of switching power supply is - small power consumption and high efficiency. In the switching power supply circuit, the transistor in the excitation signal, it constantly repeats the 'on' 'as of' switching state, the conversion speed is extremely fast, the frequency is only in the 50HZ, so that the power supply efficiency is greatly improved.

　　In fact, the switching power supply voltage stabilization range is wide. The output voltage from the switching power supply is the duty cycle of the excitation signal to regulate, the input signal signal voltage change can be compensated by frequency modulation or widening. In this way, in the industrial frequency grid voltage changes are large, it can still ensure a more stable output voltage.

　　Therefore, switching power supply technology quickly become a part of the power electronic equipment, not without reason.

Attention:

　　Switching power supply operating frequency is basically working at 50kHz, is a linear regulated power supply 1000 times, which makes the rectifier filtering efficiency almost also increased by 1000 times; even with half-wave rectification with capacitor filtering, the efficiency is also increased by 500 times. In the same ripple output voltage, the use of switching power supply, the capacity of the filter capacitor is only linear regulated power supply filter capacitor 1/500 ~ 1/1000.