Ten important considerations for the development of switching power supply technology

　　In the 1960s, the advent of switching power supplies gradually replaced linear regulated power supplies and SCR phase-controlled power supplies. Over the past 40 years, switching power supply technology has developed and changed rapidly, and has experienced three development stages: power semiconductor devices, high frequency and soft switching technology, and integration technology of switching power supply systems.

　　Power semiconductor devices have developed from bipolar devices (BPT, SCR, GTO) to MOS devices (power MOSFET, IGBT, IGCT, etc.), making it possible for power electronic systems to achieve high frequency and significantly reduce conduction losses, circuits It's also simpler.

　　Since the 1980s, the development and research of high-frequency and soft-switching technologies have enabled power converters to have better performance, lighter weight, and smaller size. High frequency and soft switching technology have been one of the hot topics in the international power electronics community in the past 20 years.

　　In the mid-1990s, integrated power electronic systems and integrated power electronic module (IPEM) technology began to develop. It is one of the new issues that needs to be solved urgently in the international power electronics community today.

　　Focus 1: Power semiconductor device performance

　　In 1998, Infineon launched a cold mos tube, which adopts a super-junction structure, so it is also called super-junction power MOSFET. The operating voltage is 600V ~ 800V, the on-state resistance is almost reduced by an order of magnitude, and the switching speed is still maintained. It is a promising high-frequency power semiconductor device.

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

　　The technological progress of IGBT is actually a compromise between on-state voltage drop, fast switching and high withstand voltage capability. With different processes and structural forms, IGBT has the following types during its 20-year historical development: punch-through (PT) type, non-punch-through (NPT) type, soft punch-through (SPT) type, trench type and electric field cutoff (FS) type.

　　Silicon carbide SiC is an ideal material for power semiconductor device wafers. Its advantages are: forbidden bandwidth, high operating temperature (up to 600°C), good thermal stability, small on-state resistance, good thermal conductivity, extremely small leakage current, PN junction High voltage resistance, etc., is conducive to manufacturing high-frequency and high-power semiconductor devices that can withstand high temperatures.

　　It is foreseeable that silicon carbide will be the most likely new power semiconductor device material to be successfully applied in the 21st century.

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