Attracting new switching power supply technology

Switching power supply has always been a very popular technology in the electronics industry, although its performance does not bring about the changes in our daily life to make a face-to-face change, and its development trend is one of the concerns of electronic designers and merchants , New products will inevitably lead to more business orders and customer spending. According to the market status and development of switching power supply, summed up the focus of the five design performance, the following one by one for your analysis.

One of the concerns: high frequency magnetic and synchronous rectification technology innovation

In the power system, we will use a large number of magnetic components, high-frequency magnetic components of the material, structure and performance are different from the power frequency magnetic components, there are many issues to be studied. And we have certain requirements on the performance of high-frequency magnetic components used in magnetic materials, including small loss, good thermal performance is the basic requirement, only to achieve such standards in order to achieve product optimization, magnetic properties will be superior. Magnetic materials suitable for MHz frequencies are a major concern for users and nanocrystalline soft magnetic materials have also been developed and applied.

And then with the high-frequency technology, to improve the efficiency of switching power supply is another technical problem, which requires our technical designers must develop and apply soft-switching technology. The research of this kind of soft switch technology has become the hot research point of the industry for many years, get more and more designers' attention.

We have seen such technologies as synchronous rectification SR technology, that is, the power MOSFET reverse connection as a rectifier diode, instead of Schottky diode (SBD). This design can reduce the tube voltage drop, thereby improving the circuit efficiency. This is what we are doing for low-voltage, high-current output soft-switching converters, and we find ways to reduce the on-state losses of the switches to further increase their efficiency.

Concerns two: switching power supply power density improvement

Improve the power density of the switching power supply, so that the miniaturization, lightweight, is one of the designer's concerns. Power supply miniaturization and weight reduction are particularly important for portable electronic devices such as mobile phones and digital cameras. Designers will reduce the power density of switching power supplies through three schemes.

The first solution is to achieve high frequency. In order to achieve a high power density of the power supply, it is necessary to increase the operating frequency of the PWM converter so as to reduce the volumetric weight of the energy storage components in the circuit.

The second solution is the use of new capacitors. To reduce the size and weight of power electronic equipment, we must try to improve the performance of the capacitor to improve the energy density, and research and development of new capacitors suitable for power electronics and power systems, requiring large capacitance, equivalent series resistance ESR small , So that the new capacitor size reduction.

The third option is the application of piezoelectric transformer improvements. The use of piezoelectric transformers enables high frequency power converters to achieve light, small, thin and high power densities. Piezoelectric transformers use the characteristic of "voltage-vibration" transformation and "vibration-voltage" transformation of piezoelectric ceramic material to transfer energy. The equivalent circuit is the same as a series-parallel resonant circuit, and the application of piezoelectric transformer is improved.

Concerns three: power semiconductor device performance

As early as the end of the last century, Infineon introduced the cold mos tube, which uses a "super-junction" structure (Super-Junction), also known as super-junction power MOSFET. Working voltage 600V ~ 800V, the on-state resistance is reduced by an order of magnitude, still keep the switching speed fast, is a promising high-frequency power semiconductor electronic devices.

Just in this very promising high-frequency power semiconductor electronic devices IGBT just appeared, the voltage and current ratings are only 600V, 25A. For a long period of time, the withstand voltage level is limited to 1200V ~ 1700V. After a long period of exploration and research and improvement, the voltage and current ratings of IGBTs have reached 3300V / 1200A and 4500V / 1800A, respectively. 6500V, the general operating frequency of the IGBT is limited to 20kHz ~ 40kHz. The IGBT based on the new technology of through-type (PT) structure can work at 150kHz (hard switching) and 300kHz (soft switching), greatly improving the application performance.

The IGBT technology we have seen is actually a compromise between on-state voltage drop, fast switching and high voltage capability. With the development of process and structure, IGBTs have been developed into PT type, NPT type, SPT type, trench type and FS type .

Silicon Carbide SiC is an ideal material for power semiconductor device chips. Its advantages are: forbidden bandwidth, high working temperature (up to 600 ℃), good thermal stability, small on-state resistance, good thermal conductivity, High pressure, is conducive to the manufacture of high-temperature high-frequency high-power semiconductor electronic components . It is not difficult for us to see that silicon carbide will be the most successful new type of power semiconductor device material in the 21st century. Its appearance will greatly improve our original product design performance.

Fourth concern: the distribution of power structure

Before talking about the distribution of power structure, let's talk about the distribution of power systems, power distribution systems are now there are two types of two-level structure and three types of two types. The distributed power system is suitable for use as a power supply for large workstations (such as image processing stations), large digital electronic switching systems and the like which are made up of ultra-high speed integrated circuits. It has the advantages of modularization of DC / DC converter components and easy implementation of N + 1 power Redundant, easy to expand the load capacity, can reduce the 48V bus current and voltage drop, easy to achieve uniform heat distribution, thermal design, transient response is good, online replacement failure module.

Five points of concern: PFC converter

AC / DC converter circuit input rectifier and filter capacitor, sinusoidal voltage input, single-phase rectifier power supply electronic equipment, grid side (AC input) power factor of only 0.6 ~ 0.65. With PFC (power factor correction) converters, the network side power factor can be increased to 0.95 ~ 0.99, the input current THD is less than 10%. It not only controls 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 developed earlier, the technology has been more mature; three-phase APFC topological types and control strategies Although there are many, but still need to continue research and development.

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