Switching power supply is a type of power supply that utilizes modern power electronics technology to control the time ratio of switching transistors on and off, maintaining stable output voltage and current. According to statistics from the internationally renowned research firm DATABEANS, the global switch mode power supply market maintained an average annual sales growth of about 15% from 2004 to 2010, reaching approximately $12 billion in sales in 2010.

The switch power supply industry in China started in the late 1970s and has now become the main producer and consumer of switch power supplies. According to relevant statistical data from UPS Applications magazine, since 2003, the Chinese power supply market has maintained an overall stable development trend. In 2008, the production of power products in China reached 31.63 million units, a year-on-year increase of 5.7%, and the sales revenue was 16.567 billion yuan, a year-on-year increase of 6.2%. With the continuous progress of science and technology, switch mode power supplies have entered a new stage of development. Technologies such as high-frequency, digitalization, and soft switching will also become the development trend of future switching power supplies.

1. High frequency technology

As the switching frequency increases, the volume of the switching converter also decreases, the power density is greatly improved, and the dynamic response is improved. The switching frequency of low-power DC/DC converters will increase to MHz. But with the continuous increase of switching frequency, new problems such as increased losses of switching and passive components, high-frequency parasitic parameters, and high-frequency EMI will also arise.

2. Digital technology

In traditional power electronics technology, the control part is designed and operates based on analog signals. At present, in the entire electronic analog circuit system, television, audio equipment, photo processing, communication, networks, etc. are gradually being digitized, and the last bastion without digitization is the power supply field. In recent years, the research momentum of digital power sources has not decreased, and the results are also increasing. The leading companies in power digitalization include Ericsson, TI, and Microchip.

3. Soft switching technology

In order to improve the conversion efficiency of converters, various soft switching technologies have been applied, representative of which are passive soft switching technology and active soft switching technology, mainly including zero voltage switching/zero current switching (ZVS/ZCS) resonance, quasi resonance, zero voltage/zero current pulse width modulation technology (ZVS/ZCS-PWM), and zero voltage/zero current transition pulse width modulation (ZVT/ZCT-PWM) technology. The use of soft switching technology can effectively reduce switching losses and stress, which helps to improve the conversion efficiency of converters.

4. Power Factor Correction Technology (PFC)

Due to the presence of rectifier components and filtering capacitors at the input end of the AC/DC converter circuit, the power factor of electronic devices powered by single-phase rectifier power supply is only 0.6-0.65 on the grid side (AC input end) during sinusoidal voltage input. By using PFC (Power Factor Correction) converters, the power factor on the grid side can be increased to 0.95-0.99, and the input current THD is less than 20%. It not only controls harmonic pollution in the power grid, but also improves the overall efficiency of the power supply. This technology is called active power factor correction (APFC) single-phase. APFC was developed earlier domestically and internationally, and the technology is relatively mature. At present, PFC technology is mainly divided into two categories: active PFC technology and passive PFC technology. Using PFC technology can improve the input power factor of AC/DC converters and reduce harmonic pollution to the power grid, but further research and development are needed.



5. Modular technology

Modularization has two meanings, one refers to the modularization of power devices, and the other refers to the modularization of power units. In recent years, some companies have also installed the drive protection circuit of switch mode power supplies into power modules, forming "intelligent" power modules (IPMs), which not only reduce the size of the entire machine, but also facilitate the design and manufacturing of the entire machine. In fact, due to the continuous increase in frequency, the influence of parasitic inductance and capacitance on the leads becomes more severe, causing greater electrical stress on the device (manifested as overvoltage, overcurrent, and burrs). In order to improve the reliability of the system, some manufacturers have developed "User specific" power modules (ASPM), which install all the hardware of a whole machine in the form of chips into one module. These modules undergo strict and reasonable design in terms of thermal, electrical, and mechanical aspects, achieving an optimized and perfect state. From this, it can be seen that the purpose of modularization is not only to facilitate use and reduce the size of the entire machine, but more importantly, to eliminate traditional wiring, minimize parasitic parameters, and thus minimize the electrical stress borne by the device, improving the reliability of the system.