The development direction of modern power electronics technology is a shift from traditional power electronics, which focuses on low-frequency technology to deal with problems, to modern power electronics, which focuses on high-frequency technology. In the application of power electronic technology and various power supply systems, switching power supply technology is at the core.

From the self-oscillation push-pull transistor single-transformer DC converter invented by GH.Roger in 1955 in the United States, it was the beginning of the realization of high-frequency conversion control circuits. Today, switching power supply technology has become indispensable in the rapid development of electronic information industry Power supply mode.

　　 Why does the switching power supply technology become the core position of modern power electronic technology? Its success only depends on its small size and easy installation with electronic equipment?

　　What is a switching power supply

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

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

　　 Simply put, the voltage regulation of the linear power supply can be regarded as the resistance value, which is equivalent to changing the voltage by adjusting the sliding rheostat, while the switching power supply changes the voltage by adjusting the switching frequency. At the same time, compared with the linear power supply, the cost of the switching power supply increases with the increase of the output power, but the growth rate of the two is different.

　　 The cost of a linear power supply is higher than a switching power supply at a certain output power point.

　　 Therefore, with the development and innovation of power electronics technology, continuous breakthroughs and innovations in switching power supply technology have made switching power supply technology continuous breakthroughs and innovations. This cost issue has instead moved switching power supply technology to the low output power end, providing a wide range of development space for switching power supplies.

　　The working principle of switching power supply

　　 Switching power supply is a power supply that uses modern power technology to control the time ratio of switching transistors on and off, and maintains a stable output voltage. Switching power supplies are composed of pulse width modulation (PWM) control (metal oxide half field effect transistors).

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

　　XED-15A12VWT internal structure diagram

Some switching power supplies use thyristors, and some use switching tubes. These rely on the base electrode and (switch tube) control electrode (SCR) to add a pulse signal to complete the conduction and cut-off, making the electronic switch constantly The ground'on' and'off' allow the electronic switching device to pulse modulate the input voltage, so as to realize DC/AC, DC/DC voltage conversion, as well as adjustable output voltage and automatic voltage stabilization.

　　The advantages of switching power supply

　　The relationship between power electronic equipment and people's work and life is getting closer, and electronic equipment is inseparable from a reliable power supply. After the 1980s, computers were fully realized as switching power supplies. By the 1990s, switching power supplies have entered various electronic and electrical fields.

　　In just ten years, switching power supply technology has quickly occupied the core position of power electronic equipment. Is this just because the switching power supply is small in size?

　　 In fact, it can be understood from the schematic diagram of the switching power supply: it does not use a bulky power frequency transformer, and at the same time, because the power dissipation on the regulator tube is greatly reduced, a larger heat sink is omitted. This makes the switching power supply smaller and lighter in weight. However, the biggest advantage of switching power supply is-low power consumption and high efficiency. In the switching power supply circuit, the transistor continuously repeats the switching state of "on" and "off" under the excitation of the excitation signal. The switching speed is extremely fast, and the frequency is only 50HZ, which greatly improves the efficiency of the power supply.

　　 In fact, the switching power supply has a wide range of voltage regulation. The output voltage from the switching power supply is adjusted by the duty cycle of the excitation signal, and the change of the input signal signal voltage can be compensated by frequency modulation or width modulation. In this way, when the power frequency grid voltage changes greatly, it can still ensure a relatively stable output voltage.

　　 Therefore, it is not unreasonable that switching power supply technology is rapidly becoming a part of power electronic equipment.

　　 Note:

The operating frequency of the switching power supply is basically 50kHz, which is 1000 times that of the linear stabilized power supply. This makes the filter efficiency after rectification almost 1000 times higher; even if the half-wave rectifier is added and the capacitor filter is added, the efficiency is also improved 500 times. Under the same ripple output voltage, when the switching power supply is used, the capacity of the filter capacitor is only 1/500~1/1000 of the filter capacitor in the linear stabilized power supply.