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Share with you the top5 concerns of switching power supply technology

Date:2020-06-13 Hits:275
Share with you the top5 concerns of switching power supply technology

Switching power supply has always been a very popular technology in the electronics industry, and its development trend is a problem that everyone must always pay attention to, otherwise it will not be able to keep up with the development of technology. The Electronic Component Technology Network conducted a focus survey on the development of switching power supply technology and found the following ten popular concerns.

Focus One: Performance of Power Semiconductor Devices

In 1998, Infineon launched a cold mos tube, which uses a "super-junction" (Super-Junction) structure, so it is also known as a super junction power MOSFET. The operating voltage is 600V to 800V, the on-state resistance is almost reduced by an order of magnitude, and the characteristics of fast switching speed are still maintained. It is a promising high-frequency power semiconductor electronic device.

When the IGBT first appeared, the voltage and current ratings were only 600V, 25A. For a long period of time, the withstand voltage level is limited to 1200V ~ 1700V. After a long period of research and improvement, the voltage and current ratings of IGBT have reached 3300V/1200A and 4500V/1800A respectively, and the high-voltage IGBT single-chip withstand voltage has reached 6500V, the upper limit of the working frequency of general IGBT is 20kHz~40kHz, based on the PT structure, the IGBT manufactured by applying new technology can work at 150kHz (hard switching) and 300kHz (soft switching).

The technical progress of IGBT is actually a compromise between on-state voltage drop, fast switching and high withstand voltage capability. With the different processes and structural forms, in the 20-year history of IGBT development, there are the following types: punch-through (PT) type, non-punch-through (NPT) type, soft punch-through (SPT) type, trench type and electric field cut-off (FS) type.

Silicon carbide SiC is an ideal material for power semiconductor device wafers. Its advantages are: wide band gap, high operating temperature (up to 600°C), good thermal stability, small on-state resistance, good thermal conductivity, very small leakage current, PN The high junction withstand voltage is beneficial to the manufacture of high-power high-frequency semiconductor electronic components that are resistant to high temperatures.

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Concern 2: Power density of switching power supply
  Improving the power density of switching power supplies to make them smaller and lighter is the goal that people continue to strive for. The high frequency of power supply is one of the hotspots in the international power electronics research. The miniaturization and weight reduction of power supplies are particularly important for portable electronic devices (such as mobile phones, digital cameras, etc.). The specific methods for miniaturizing the switching power supply are:
   First, high frequency. In order to achieve high power density of the power supply, it is necessary to increase the operating frequency of the PWM converter, thereby reducing the volume and weight of the energy storage components in the circuit.
The second is the application of piezoelectric transformers. The application of piezoelectric transformers can make high-frequency power converters light, small, thin and high power density. Piezoelectric transformers use the unique "voltage-vibration" transformation and "vibration-voltage" transformation properties of piezoelectric ceramic materials to transfer energy. Its equivalent circuit is like a series-parallel resonant circuit, which is one of the research hotspots in the field of power conversion.
   The third is the use of new capacitors. In order to reduce the volume and weight of power electronic equipment, we must try to improve the performance of capacitors, increase energy density, and research and develop new capacitors suitable for power electronics and power supply systems. They require large capacitance and small and small ESR and small volume。
Focus Three: High Frequency Magnetic and Synchronous Rectification Technology
   A large number of magnetic components are used in the power supply system. The material, structure and performance of the high-frequency magnetic components are different from the power frequency magnetic components. There are many problems to be studied. The magnetic materials used for high-frequency magnetic components have the following requirements: low loss, good heat dissipation performance, and excellent magnetic performance. Magnetic materials suitable for megahertz frequencies have attracted attention, and nanocrystalline soft magnetic materials have also been developed and applied.
   After high frequency, in order to improve the efficiency of the switching power supply, it is necessary to develop and apply soft switching technology. It is a research hotspot in the international power industry in the past few decades.
   For low-voltage, high-current output soft-switching converters, the measure to further improve its efficiency is to try to reduce the on-state loss of the switch. For example, the synchronous rectification SR technology, that is, the reverse connection of the power MOS tube as the switching diode for rectification, instead of the Schottky diode (SBD), can reduce the tube voltage drop, thereby improving circuit efficiency.
Focus four: distributed power structure
The distributed power system is suitable for power supply of large workstations (such as image processing stations) composed of ultra-high-speed integrated circuits and large digital electronic switching systems. Its advantages are: modularization of DC/DC converter components; easy implementation of N+ 1 Power redundancy, easy to expand the load capacity; can reduce the current and voltage drop on the 48V bus; easy to achieve uniform heat distribution and convenient heat dissipation design;
   Now there are two types of structure of distributed power system, one is two-level structure, and the other is three-level structure.
Focus five: PFC converter
   Since the input end of the AC/DC conversion circuit has a rectifying element and a filter capacitor, when sinusoidal voltage is input, the electronic equipment powered by the single-phase rectified power supply, the power factor on the power grid side (AC input end) is only 0.6 to 0.65. Using PFC (power factor correction) converter, the grid-side power factor can be increased to 0.95 ~ 0.99, the input current THD is less than 10%. It not only treats the harmonic pollution of 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 has been developed earlier at home and abroad, and the technology is relatively mature. Although there are many types of topologies and control strategies for three-phase APFC, they still need to be researched and developed.
   General high power factor AC/DC switching power supply is composed of two-stage topology. For low-power AC/DC switching power supply, the two-stage topology structure has low overall efficiency and high cost.
If the input power factor is not particularly high, the PFC converter and the post-stage DC/DC converter are combined into a topology to form a single-stage high power factor AC/DC switching power supply. Only one main switching tube can be used. The power factor is corrected to more than 0.8, and the output DC voltage is adjustable. This topology is called a single-tube single-stage, that is, S4PFC converter.