Revolutionising GaN power electronics

Hayley Everett

Gallium Nitride (GaN) transistors can provide huge efficiency gains in high-power applications due to their ability to operate at ultrahigh frequencies for switching on and off. The higher the switching speed of a transistor, the less time is spent in transition and the less energy is lost. However, issues surrounding overheating and electronic interference at 100kHz and above have so far prevented GaN from realising its full potential.

To solve this conundrum, clean-tech company QPT has released a new set of patented technologies that allow GaN to operate at up to 20MHz for the first time without overheating or radiofrequency issues, therefore opening up a vast new application area for GaN. The firm specialises in creating technologies needed to enable GaN to operate at well over the current limitations of 100kHz right up to 20MHz in high power, high voltage applications that use hard switching, such as motor drive systems for HVAC and robotics.

“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 silicon (Si) and silicon carbide (SiC) transistors operate,” explains Rob Gwynne, QPT’s Founder and CEO. “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 20MHz with nanosecond switching to deliver better operational precision without RF interference issues or overheating and thus, for the first time, deliver their promised efficiencies.”

QPT has integrated its new technology breakthroughs into two modules so that it can be easily integrated by customers with little effort and changes to existing designs. The qGaN module contains a 650V GaN transistor with the company’s qDrive – which it claims is the fastest, most accurate, highest resolution low jitter isolated GaN transistor gate drive on the market. The second module is the qSensor, which combines the company’s Zest and qSense technologies, and provides the sensing and control capabilities that enable the GaN to be driven at super high frequencies.

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 together in a Faraday cage so that there are no heating or RF issues. Combined together, the technologies unlock the ability of GaN to now operate at ultra high frequencies and provide up to 80% reduction in power usage compared to existing solutions that have to operate at much lower frequencies.

In practice, the first qGaN module will handle 15A 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 QPT technology modules, turnkey solutions can be easily assembled according to the reference design, which is a drop-in replacement for the power stage of existing VFDs without the need for any specialist expertise in EMC or thermal cooling.

“The rest of the existing system such as the microprocessor and software stack stay the same,” continues 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. Combining the VFD power saving of around 80% with the motor usage gives around 20% reduction in overall power usage, which increases in applications where the motor is frequently at low speeds where the current solutions are inefficient.”

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