Unleashing GaN’s full ability for high-speed switching
GaN transistors can switch at much faster speeds than
silicon or SiC making them much more efficient. However, GaN transistors
can overheat if driven at more than 100 kHz, and generate unacceptable
levels of EMI.
Rob Gwynne, CEO of QPT Ltd, explains how his company has solved these limitations to unleash GaN to work at up to 20 MHz and deliver its full potential.
Operating GaN FETs at under 100 kHz means that their performance is similar to silicon or SiC, which limits the benefits to using GaN in the first place. As GaN transistors can transition from on to off at 1-2ns instead of 20-50ns for Si and SiC transistors, there is potential for a huge improvement in efficiency.
The core of the problem is that the expertise of power engineers is in the 10 to 100 kHz region where Si and SiC currently operate. Go above this and RF issues start to become a problem which requires solving them with a different set of skills, i.e., those of an RF engineer, with a Faraday cage to block the EMI. The second issue is the huge amount of energy within a tiny slice of GaN, which if not handled correctly means that the transistor will rapidly overheat.
This can be seen in figure 1 that shows the increasing amount of waste energy being produced as losses as the operational frequency of SiC and normal GaN increases. By contrast, the green line of GaN with QPT’s technology shows hardly any increase in energy loss.