![]() ![]() SiC appears to be the favorite for on-board chargers (OBCs). Superjunction MOSFETs are gradually being replaced by both GaN and SiC.SiC operates at higher voltages than GaN.SiC can also handle more current than GaN. SiC devices can switch at higher frequencies (100 kHz or higher, versus 20 kHz), thereby reducing the size and cost of any inductors or transformers while increasing efficiency. In many applications, these older devices are gradually being replaced by GaN and SiC transistors.įor example, IGBTs are being replaced by SiC devices in many applications. ![]() WBG transistor competitionīoth GaN and SiC devices compete with other well-established semiconductors, specifically Si LDMOS MOSFETs, superjunction MOSFETs, and IGBTs. SiC MOSFETs are generally more costly than other alternatives, but their high-voltage, high-current capabilities make them well-suited to automotive power circuits. However, special gate drive ICs have been developed to meet this need. In addition, SiC devices need a –3- to –5-V gate drive for switching to the “off” state. Standard Si MOSFETs require a gate of less than 10 V for full conduction. SiC devices need 18 to 20 V of gate drive voltage to turn on the device with a low on-resistance. One key disadvantage is that they require a higher gate drive voltage than other MOSFETs, although this is changing as designs improve. In addition, the on-resistance of SiC devices is much lower than that of silicon MOSFETs, making them more efficient in all switching power applications. Maximum drain-source voltage is up to about 1,800 V with a current capability to 100 A. These devices can switch at frequencies as high as 1 MHz at voltage and current levels much higher than silicon MOSFETs. SiC transistors are natural e-mode MOSFETs. However, because of their high voltage (up to 1,000 V), high temperature, and fast switching, they have also been incorporated into a variety of switch-mode power supply applications such as DC/DC converters, inverters, and battery chargers. Some of the primary use cases are cellular base station power amplifiers, military radar, satellite transmitters, and general RF amplification. ![]() GaN devices are widely used in wireless equipment as power amplifiers at frequencies up to 100 GHz. They can switch at frequencies up to 10 MHz and up to tens of kilowatts. The first was a cascode of two FET devices ( Figure 2) now, standard e-mode GaN devices are available. ![]() Gate input signals control the channel conduction and turn the device on and off.īecause normally “off” enhancement-mode (e-mode) devices are preferred in switching applications, this led to the development of e-mode GaN devices. Known as a pseudomorphic high-electron–mobility transistor (pHEMT), d-mode FETs are naturally “on” devices with no gate control input, a natural conduction channel exists. The nature of the materials led to the development of a depletion-mode (d-mode) field-effect transistor (FET). GaN transistors found an early niche in the radio-frequency (RF) power field. Lower conduction resistance with minimum power dissipation and greater efficiency.High-voltage capability with devices for 650, 900, and 1,200 V.The key takeaways for GaN and SiC devices are these advantages: GaN and SiC transistors are becoming readily available to address the challenges of automotive electrical equipment. This unique combination of characteristics makes these devices attractive for some of the most demanding circuits used in automotive applications, especially hybrid electric vehicles (HEVs) and EVs. Lower on-resistance means they dissipate less power, thereby promoting efficiency. WBG transistors also switch faster and can operate at higher frequencies than silicon. Figure 2: A two-die two-FET cascode circuit converts GaN transistors into normally “off” devices, enabling the enhancement mode of operation that is standard in high-power switching circuits. ![]()
0 Comments
Leave a Reply. |
Details
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |