Revolutionising GaN power electronics

QPT Limited is the first company to create the technologies required to enable GaN to operate well over the current limitations of 100kHz right up to 20 MHz in high power, high voltage applications that use hard switching, such as motor drive systems for HVAC, robotics, etc. This disruptive technology opens up this important section of the GaN market that no one else currently has solutions to address.

The importance of GaN transistors for next-generation power electronics is due to their ability to operate at ultrahigh frequencies for switching on and off. A slow transition wastes energy because, during the switching time when the transistor is neither on nor off, it dissipates huge amounts of power, resulting in energy losses and overheating issues. The higher the switching speed, the less time is spent in transition, and the less energy is lost. GaN can quickly transition from on to off at 1-2ns instead of 20-50ns for Si and SiC transistors.

However, in high voltage, high power applications, there is a practical limit of 100kHz for GaN, beyond which the issues of overheating and RF interference become too great. The current solution is to throttle GaN back to sub 100kHz, which means that the performance is like Silicon Carbide, and there are no benefits to using GaN as it is not running at high switching speeds or frequencies where it delivers power savings.

Rob Gwynne, QPT's founder and CEO, explained, "Power engineers are focused on being an expert in one field and have developed skills and design approaches that work at 10-100Khz switching, which is where Si and SiC transistors operate. I was able to look at the problem as an RF engineer and create a solution that enables the GaN transistors to be run at their full potential of up to 20 MHz with nanosecond switching to deliver better operational precision without RF interference issues or overheating and, thus, for the first time, deliver their promised efficiencies."

The company has integrated its technology breakthroughs into two modules so that it can be easily implemented by customers with minimal effort and changes to existing designs. The qGaN module contains a 650V GaN transistor with the company's qDrive, which is the world's fastest, most accurate, highest resolution, low jitter Isolated GaN Transistor Gate Drive. The second module is qSensor, which combines the company's ZEST and qSense technologies. It provides the sensing and control that enables the GaN to be driven at super-high frequencies for the first time.

In addition, QPT has developed its WisperGaN construction system that includes a reference design for how the modules and the ancillary electronics can be assembled in a Faraday cage so there are no heating or RF issues. The resulting solution unlocks the ability of GaN to operate at ultrahigh frequencies and provides up 80% reduction in power usage compared to existing solutions that have to operate at much lower frequencies.

The first qGaN module (Q650V15A-M01) will handle 15A RMS current driving 380V three-phase motors. The roadmap will have qGaN modules to handle various different power loads to suit different application area requirements. Together with the other of the company's technology modules, turnkey solutions can be readily assembled according to the reference design. The reference design is a drop-in replacement for the power stage of existing VFDs without needing specialist expertise in EMC or thermal cooling.

"The rest of the existing system, such as the microprocessor and software stack, stay the same," explained Rob Gwynne. "This makes upgrading a genuine plug-and-play solution with the benefits of needing less power so it effectively pays for itself in weeks. In addition, there are further savings as the new BOM is less than existing solutions as it does not require external filters. Companies who want to upgrade from their current silicon solutions to be more power efficient can leapfrog over the hassle of developing a SiC solution in-house and simply use our unleashed GaN solution. Combining the VFD power saving of around 80% with the motor usage gives around 10% reduction in overall power usage, which increases in applications where the motor is frequently at low speeds where the current solutions are inefficient."

The company estimates that the high voltage, high power application markets where its new technology can provide significant power savings has a Total Addressable Market (TAM) of $365 billion. A key segment of that is HVAC and especially heat pumps that are being deployed exponentially around the world, so the TAM will continue to increase. Rob Gwynne, concluded, "Electric motors account for 45% of global electricity usage, and our technology can make them more efficient, and that means less carbon dioxide emissions which help combat climate changes."