There has been a continuous effort in increasing the switching frequency of power converters so as to reduce their size and cost and to increase efficiency. While increasing switching frequency can help in reducing losses in passive components (due to the reduced bulk), it has the opposite effect on losses in active components. The limitation of conventional switching devices based on Silicon as base material (such as IGBTs and MOSFETs) to operate efficiently at higher switching frequencies prompted the development of switching devices based on wider bandgap materials like SiC and GaN. These devices now allow operation of power conversion topologies at multiple hundreds of kHz compared to Si devices that were limited to operation at a few tens of kHz. Also, these devices are capable of operating at higher temperatures than Si devices, increasing the reliability in solar inverters that typically need to operate at higher ambient temperatures.

Nowadays, SiC MOSFET devices are available at comparable voltage withstand capability as Si IGBTs, allowing them to directly replace IGBTs in topologies like HERIC, TNPC and so forth, at the same time increasing switching frequencies tenfold. While GaN devices are currently not available in higher withstand voltage levels as IGBTs, multiple sources are available for 600-V to 700-V rated devices. As they are capable of switching at even higher frequencies than SiC devices, there is keen interest in multi-level topologies like NPC, ANPC, and so forth, that can accommodate these devices efficiently. Also, isolated DC/DC topologies like CLLLC and DAB can operate much more efficiently with GaN devices allowing operation at multiple hundreds of kHz.

While WBG semiconductor devices help in reducing the size and increasing efficiency of power converters, their fast switching operation introduces newer challenges like more critical layout, higher EMI (due to increased dv/dt), and more complex thermal management. The layout and package parasitics become more prominent with higher speed switching. This leads to higher integration as in the case on TI’s gate driver integrated GaN power device. To reduce parasitics, GaN switches are packaged as SMD devices, making their thermal management more difficult. More insights into addressing these challenges are available in TI’s Design considerations of GaN devices for improving power converter efficiency and density white paper.