Research and Analysis on Innovation and Application Situation of Semiconductor Technology in China

10/29/2022 11:00:08 AM

The invention and application of semiconductor devices have profoundly changed the development process of human history in the past 50 years. In the 21st century, semiconductor devices are everywhere and have become the cornerstone of building an information society. At the same time, the role of power semiconductor in improving power conversion efficiency makes it the cornerstone of building a low-carbon society. The energy-saving effect of semiconductor technology is obvious. ENIAC, the world's first electronic computer with electron tubes, weighs 30 tons and consumes as much as 200kW. However, today's semiconductor computing equipment with the same function weighs only a few grams and consumes less than 1 W.. At the same time, power semiconductor plays a key role in the process of electric energy conversion, storage and transmission of solar photovoltaic and wind power generation devices. It can be seen that the utilization of renewable energy and the improvement of the efficiency of energy conversion devices are inseparable from the innovative application of semiconductor technology.

After years of development, silicon Si devices have changed the face of household appliances, and DC speed regulation technology has become the main technical measure to improve the efficiency of household air conditioners and other motors. It is noteworthy that the technological development of new devices, such as silicon carbide SiC, gallium nitride GaN and gallium oxide Ga2O3, will not only improve the power conversion efficiency by reducing the energy consumption of devices, but also promote the technical development of household appliances in terms of reducing the overall size and improving the heat resistance.

Improving the efficiency of energy utilization is a topic with wide implications. As far as household appliances are concerned, the narrow sense of improving efficiency is mainly to improve the energy utilization efficiency of household appliances during operation. At present, countries have basically supervised the energy utilization efficiency of household appliances, and energy efficiency labeling and energy efficiency rating system are common supervision methods. To improve the efficiency in a broad sense, we need to consider the energy consumption in the manufacturing process, the energy consumption of raw materials and the indirect energy efficiency in the operation process. The efficiency discussed in this paper is limited to the narrow scope, and only aims at the measures to improve the energy utilization efficiency by using technological progress, and will focus on the role of power semiconductors in improving the energy utilization efficiency of household appliances.

Material substitution of power semiconductor

Household electricity consumption accounts for about one-third of the total electricity consumption in American society. It is predicted that the number of American households will increase by 11% in the next 10 years, and thanks to power semiconductor technology, the electricity consumption of American households will only increase by 6%. A survey report points out that 6%~10% of all power applications in the United States are converted from AC to DC, and 3%~4% of the total power consumption in the United States is consumed inside the power supply because of the poor efficiency of the existing power supply; Improving product design, using microelectronic control devices and power semiconductors such as FET and diode to improve power efficiency can save 1%~2% of the total power consumption in the United States. This means that power semiconductor technology has the potential to save 3 billion to 6 billion dollars every year.

Nowadays, the development of power semiconductor technology is not only reflected in the increasingly widely used high-efficiency LED lighting appliances, but also in the field of high-power household appliances such as air conditioners, refrigerators, washing machines, electromagnetic stoves, etc., the application of power semiconductor has exceeded the scope of controller driving power supply. High-power power semiconductor drive technology has changed the original operation mode and energy conversion process of products, and the energy saving effect is remarkable. Improving the power conversion efficiency of household appliances and reducing standby energy consumption are widely used energy-saving measures at present. Semiconductor manufacturing enterprises, power conversion parts manufacturing enterprises and household appliances manufacturing enterprises are trying to make these losses smaller.

Motor is the main power-consuming component of most white goods. Although the functions of speed control and variable torque control technology in improving motor efficiency have long been known and widely used in industrial fields, these technologies were difficult to be applied to household appliances with compact structure and relatively inconvenient maintenance before the appearance of power semiconductors. For example, a DC motor with speed regulation function uses a mechanical commutator before it is equipped with a semiconductor commutator, but the service life of the mechanical commutator is usually less than 1000h, which makes the driving power supply bulky and expensive. At the end of 1970s, Japanese enterprises applied power semiconductor technology to the speed control of air-conditioning refrigeration compressor, which basically realized 100,000 h maintenance-free of the whole machine, and at the same time greatly reduced the external size of the driving power supply, which could be placed inside the air conditioner, and the price was greatly reduced. In less than 10 years, the Japanese market has basically completed the transformation from fixed speed to variable frequency speed regulation. Although the frequency conversion power supply consumes about 10% of electric energy, the power consumption of residential air conditioning can be reduced by about 30% on average by using the variable speed and torque function of frequency conversion speed regulation during operation. At the same time, it can greatly improve the heating capacity under the winter heat pump operation mode, which also promotes the wide application of heat pump heating technology.

The technical development trend of power semiconductors, such as metal oxide semiconductor field effect transistor MOSFET, insulated gate bipolar transistor IGBT and diode, which play a switching role in frequency converters and transformers, is to change from the current mainstream Si semiconductor materials to compound semiconductor materials such as SiC and GaN, and make great progress in improving efficiency and reducing volume.

ISE, the Solar Energy System Research Institute of the Fraunhofer Association for the Promotion of Applied Research in Flawn, Germany, has improved the efficiency of the inverter supporting the solar photovoltaic power generation device to 98.5%, and the power loss of the new inverter is reduced by about 50% compared with the original similar inverter of this institution. In this mechanism, SiC devices are used instead of Si devices in the single-phase inverter with rated power of 5kW, which is the key to significantly improve the efficiency. These SiC devices are produced by Cree Company in the United States. In 2010, the company has solved the manufacturing process problem of the 6-inch diameter SiC backplane, and achieved mass production, which has created conditions for a significant reduction in the manufacturing cost of SiC devices.

The higher efficiency of new semiconductor devices is mainly due to the lower internal power consumption of the devices. Under the same circuit structure, the power consumption can be reduced by about 30% by changing the diode from Si material to SiC material. If the transistors are replaced at the same time, the power consumption can be reduced by about 50%. With the decrease of power consumption, the calorific value also decreases, thus realizing the energy saving of power conversion devices.

In addition to low power consumption, GaN and SiC also have characteristics suitable for miniaturization. First of all, devices made of the above two materials can realize high-speed switching several times that of Si elements, which greatly reduces the size of peripheral circuit components such as inductors, thus realizing the miniaturization of power conversion device circuits. Secondly, SiC and GaN components can also work in the high temperature environment above 200℃ which Si components can't adapt to, and the overall size of the cooling device of power conversion devices can be reduced under the same calorific value.

With the acceleration of industrialization of GaN and SiC power semiconductors, it is urgent to develop new peripheral circuits that make full use of their characteristics, such as driving circuit design that can realize high-speed operation and electromagnetic noise countermeasures based on high-frequency switching. In order to make these power semiconductors work in the high temperature environment over 200℃, in addition to using solder materials with high heat resistance and low price, high temperature resistant packaging materials are also needed in chip mounting. The progress of these peripheral circuit technologies is the key to exert the effectiveness of GaN and SiC devices.

Industrialization of silicon carbide devices

In October, 2010, mitsubishi electric Company announced that it would start selling household air conditioners with Schottky barrier diode SBD made of SiC as the driving power supply for DC speed-regulating compressors in the freezing year of 2011. This is the world's first household appliance using SiC power semiconductor, which marks the beginning of a new generation of power semiconductor industrialization represented by SiC in the household appliance industry.

The first batch of home air conditioners using SiC devices are mitsubishi electric Wufeng MoveEye series products, including MSZ-ZW281S with rated cooling capacity of 2.8kW and MSZ-ZW361S with rated cooling capacity of 3.6kW. According to the plan, Wufeng MoveEye series will cover the range of rated cooling capacity of 2.2 kW to 7.1 kW, and other models will gradually replace Si devices with SiC devices. Although the price of SiC devices is still high at present, mitsubishi electric did not reflect the cost change on the price of the whole machine, but absorbed the increased cost by making profits.

This batch of air conditioners still use insulated gate bipolar transistor IGBT, and the Si diode is changed to SiC-SBD, which is only used for driving power supply of DC speed regulating compressor. From the point of view of energy saving, the power conversion loss of compressor driving power supply can be reduced by about 60% and the power consumption of air conditioner can be reduced by about 2% by using SiC-SBD. If it is necessary to further improve the power conversion efficiency and reduce the overall size of the driving power supply, it is necessary to change all other power semiconductors into SiC devices to realize the replacement of IGBT with SiCMOSFET. Mitsubishi electric's move aims to accelerate the development of SiC market, make the price of SiC devices enter a reasonable range as soon as possible, and strive to achieve the industrialization goal of SiCMOSFET in 2013~2014, so as to gain a competitive advantage in the power semiconductor market. Mitsubishi electric plans to replace all IGBT's with SiCMOSFET's, and SiC devices will be applied not only to the compressor driving power supply, but also to the power supply part of the main control panel. If all SiC devices are used, the overall size of the power electronic module of the main control board will be reduced to about 50% at present.

Mitsubishi electric has published a series of verification results of energy-saving prospects for power conversion devices with full SiC. The motor frequency converter with output power of 11kW was trial-produced by using SiC-SBD and SiCMOSFET. Compared with similar complete machines made of Si devices in mitsubishi electric, the power consumption was reduced by about 70%. At the same time, the volume of the trial-produced SiC inverter is smaller than that of the Si inverter, and the volume of the whole machine using SiC devices is only about 1/4 of that using Si devices. In addition, the power consumption of the SiC motor inverter with an output power of 3.7kW trial-produced in mitsubishi electric is about 54% lower than that of the Si motor inverter.

The verification results show that the energy-saving effect of SiC motor inverter with output power of 20kW is more significant. Compared with similar IGBT products made of ordinary Si, the power consumption of SiC motor inverter with rated output power of 20kW and switching frequency of 20kHz is reduced by about 90%. According to reports, this is to improve the switching speed of SiC devices by shortening the switching time, thus reducing power consumption. In order to accelerate the switching speed, the gate drive circuit needs to achieve high speed, improve the drive mode and reduce the parasitic inductance in the drive circuit, thus shortening the switching time to about 50%. At the same time, increasing the switching speed may lead to an increase in surge voltage, thus damaging SiC devices. In order to avoid this problem, the new product reduces the parasitic inductance in the circuit to suppress the surge voltage by improving the configuration and circuit wiring of SiC devices. Compared with the Si motor inverter with an output power of 20kW, the parasitic inductance of the SiC motor inverter is only 1/5~1/10 of the former.

In February, 2011, mitsubishi electric announced the successful development of a power semiconductor device with both transistors and diodes made of SiC-"all SiC" intelligent power module IPM. In addition to using SiC devices, IPM also embeds the overcurrent protection circuit together with the drive circuit in the module. In general, it is difficult to improve the current density and reduce the loss in power components, and IPM can achieve this win-win situation because of the use of SiC power components. Compared with IGBT made of Si devices, the current density of the new module is increased by about 3 times, and the power consumption of the inverter is reduced by about 70%. In addition, the volume of the new module is about half that of the original similar module.

Japan Electric Power Central Research Institute has successfully trial-produced an inverter using SiC diodes for the connection of distributed power systems. The rated output power of the inverter is 3.3kW, the output voltage is single-phase 200V, and the conversion efficiency is as high as 96.4%. It is the product with the highest energy conversion efficiency among similar power electronic conversion devices at present, and is mainly used for power regulation of household solar power generation systems and fuel cell systems. The inverter is composed of a chopper that regulates DC voltage and a single-phase inverter that converts DC to AC, and achieves high conversion efficiency by reducing the recovery current of diodes on the chopper circuit. Compared with the highest performance products using Si diodes, the power loss of the inverter is reduced by 15%. By increasing the switching frequency of chopper circuit, the volume of the device is reduced by 15%.

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