Development, application and example illustration of power devices

As global energy becomes increasingly scarce, energy conservation and power saving are imminent. Power conversion is an important part of energy conservation and power saving. In the process of power conversion, energy loss during conversion is an important factor affecting energy conservation and power saving, and has always been the focus of people's attention. Silicon power semiconductor devices have gone through the development process from bipolar transistors, thyristors, to power MOSFETs and the insulated gate field effect transistors (IGBTs) that are very popular today, which has made great progress in energy conservation and power saving in power electronics.

1. SiC power components have their unique advantages.

For SiC, it is a cost-effective high-power high-temperature semiconductor device and a basic element used in microelectronics technology. SiC is a wide bandgap semiconductor material, which has many advantages over Si in applications. Due to its wide bandgap, the operating temperature of SiC devices can be as high as 600°C, while the maximum operating temperature of Si devices is limited to 175°C. The high-temperature working capability of SiC devices reduces the requirements for the system thermal budget. In addition, SiC devices also have high thermal conductivity, high breakdown electric field strength, high saturation drift rate, high thermal stability and chemical inertness, and their breakdown electric field strength is higher than that of similar Si devices. It can be said that with the development of technology, the development prospects of SiC are very bright!

2. Application Status of SiC Devices for Power Components

With the development of high-frequency and high-power modern power electronics technology, potential problems of switching devices in applications are becoming more and more prominent. The voltage and current overshoots caused by the switching process affect the working efficiency and reliability of the inverter. In order to solve the above problems, measures such as overcurrent protection, heat dissipation and line inductance reduction are actively adopted. Snubber circuits and soft switching technologies have also been widely studied and have made rapid progress. The use of power components can well solve the above problems.

Insulated gate bipolar transistor IGBT is a new type of power electronic device, which combines the advantages of GTR and MOSFET, easy control, fast switching speed, high operating frequency, and large safe working area. With the continuous improvement of voltage and current levels, IGBT has become an ideal power switching device for high-power switching power supplies, variable frequency speed regulation, active filters and other devices, and has been widely used in power electronic devices.

SiC devices have great application potential in high temperature, high frequency, high power, high voltage optoelectronics and radiation resistance.

1 Application of SiC devices in high temperature environments

In aerospace and automotive equipment, electronic devices often have to work at high temperatures, such as aircraft engines, car engines, spacecraft performing missions near the sun, and high-temperature equipment in satellites. Using common Si or GaAs devices, because they cannot work at very high temperatures, these devices must be placed in a low-temperature environment. There are two ways to deal with this: one is to place these devices away from high temperatures, and then connect them to the devices to be controlled through leads and connectors; the other is to place these devices in a cooling box and then place them in a high-temperature environment. Obviously, both methods will add additional equipment, increase the quality of the system, reduce the space available for the system, and make the system less reliable. If you use devices that can work at high temperatures directly, these problems can be eliminated. SIC devices can work directly in 3M-Y without cooling the high-temperature environment.

2 Microwave Applications of SiC Devices

In addition to being able to operate at high temperatures, SiC devices also have many excellent microwave properties.

Critical aviation radio equipment relies on the ability of front-end RF receivers to detect and amplify useful signals and filter out interfering signals. As the radio wave spectrum becomes increasingly crowded, the failure of navigation and positioning aviation equipment caused by RF interference poses an increasing threat to flight safety. The use of SiC semiconductor devices will greatly enhance the anti-interference ability of RF receiver circuits. Compared with Si mixers, SiC mixers successfully reduce RF interference in Si receiver circuits to one-tenth of the original.

3 Application of SiC Intelligent Power Devices in Power Systems

Advanced SiC power electronics can improve the efficiency and reliability of utility power systems. Currently, the power required at any one time should be about 20% more than the actual power consumed. This excess power storage is to ensure that power services are stable and reliable. So as not to be affected by daily load changes and local faults. Combining smart power devices with power arrays can greatly reduce the required power storage margin because these circuits can detect and immediately compensate for local electrical pulses. The power storage margin can be reduced by at least 5%, which will greatly save energy. The same smart power technology can also increase the power that can be transmitted by existing spokes by about 50%.

3. Effect of Temperature on Power MOSFET Transmission Characteristics

During the process of turning on the MOSFET, RDS (ON) transforms from the negative temperature coefficient region to the positive temperature coefficient region; during the process of turning off the MOSFET, RDS (ON) transitions from the positive temperature coefficient region to the negative temperature coefficient region. The voltage-dividing effect of the equivalent gate and source resistances in series with the MOSFET and the influence of the gate capacitance cause the VGS voltage of the cell unit to be inconsistent, which leads to inconsistent currents of each cell unit, resulting in local overheating damage during the process of turning on and off. Turning on and off the MOSFET quickly can reduce the accumulation of local energy and prevent local overheating and damage of the cell unit. If the turning on speed is too slow, the area close to the gate pin is prone to local overheating damage. If the turning off speed is too slow, the area far from the gate pin is prone to local overheating damage.

4. Typical Examples of SiC Power Components

SiC power modules are used in both switching loss and surge voltage. Compared with common Si IGBT modules, they can reduce switching loss by up to 92%. As shown in the following figure, we can find the unique application of SiC power modules based on the curve.

The following figure is a typical application example of a power module - a motor with a built-in module. We know that the motor of the existing system is separated from the power control device, just like the connection between the power control device such as the inverter and the motor shown in the picture. The problems they will encounter are large loss, large size, and high noise. Even this power control device cannot withstand the high temperature of the motor, and it is difficult to make the size fine. But when we use the module built into the motor, it can work at high temperatures and the size can be very small. Small size, low power consumption and low noise are the future development direction and focus.

V. Conclusion

Through the above examples, we have a certain degree of understanding of SiC power components. As SiC power components have developed rapidly in the past few years, the bulk growth and epitaxial growth technology of SiC wafers can be used in commercial production of SiC wafers. By improving and optimizing the design of devices and circuits, the super performance of SiC materials can be brought into play. With the continuous maturity of SiC material growth and device manufacturing technology, more and more SiC electronic products will enter the application field.