A brand new gallium nitride (GaN) resolution claims to take the know-how effectively over its present limitations of 100 kHz to facilitate exhausting switching at excessive voltages for motor drive programs serving functions resembling HVAC and robotics. Two new modules from QPT have employed an IP that allows GaN transistors in high-voltage, hard-switching functions to run at frequencies of as much as 20 MHz whereas offering ultrafast switching within the 1-2 ns vary versus 20-50 ns vary for GaN when constrained to beneath 100 kHz to keep away from heating and electromagnetic compatibility (EMC) points.
In contrast to silicon carbide (SiC), which can not run at converter speeds sooner than 100 kHz with out switching losses changing into unacceptable, GaN can change quick at 1-2 ns speeds and assist excessive converter speeds of 10’s of MHz. However the exceptionally troublesome EMC and thermal points should be resolved to attain this inherent GaN advantage.
The present options throttle again to sub-100 kHz frequencies to keep away from overheating and RF interference. In consequence, GaN’s efficiency is just like SiC because it can not run at excessive switching frequencies to ship energy financial savings. “There are large EMC points, and they’re costly to repair,” stated Rob Gwynne, QPT’s founder and CEO.
Nonetheless, the significance of GaN know-how primarily comes from its capability to function at ultra-high frequencies for switching on and off. In any other case, throughout the switching time, when the transistor is neither on nor off, it dissipates enormous quantities of energy, resulting in power losses and overheating points.
Determine 1 The three curves present losses of SiC and GaN gadgets at 500 kHz (above), losses at 1 MHz (center), and GaN losses at 2 MHz whereas operating exhausting switching (under). Supply: QPT
“When dv/dt is bigger than present remoted gate drivers can tolerate, your system will self-destruct, or you need to restrict dv/dt, thereby losing energy,” Gwynne added. “That’s how you find yourself with RF/microwave energy routing/matching points with interconnect.” Consequently, energy design engineers should change the filter and decoupling elements to function at microwave frequencies.
Subsequent, they have to make use of widespread mode and differential mode complicated microwave filters to resolve carried out emissions points. “We now have solved the extremely complicated issues of EMC, thermal management, and RF/microwave interconnect,” Gwynne stated. QPT’s resolution allows GaN transistors to run at their full potential of as much as 20 MHz with nanosecond switching and ship higher operational precision with out overheating or RF interference points.
Key utility: Motor drive
The important thing utility benefitting from GaN’s ultra-high frequencies for switching on and off might be management electronics for motor drives. Right here, excessive effectivity can play a significant position in saving power by way of pace controls for motors. “Electrical motors account for 45% of worldwide electrical energy utilization and our know-how could make them extra environment friendly and which means much less carbon dioxide emissions which helps fight local weather adjustments,” stated Gwynne.
That is the way it all works. Variable frequency drives (VFDs) in motor management function by chopping the incoming energy to create a frequency that may be modified to regulate the pace of the motor, and power is misplaced each time chopping happens. It’s essential to notice that the widespread notion amongst producers is that this power loss is minimal. Nonetheless, when producers quote an effectivity of 97%, it’s at full pace. So, when the pace drops, the effectivity drops considerably, a reality usually ignored by producers.
Determine 2 Here’s a comparability between a typical VFD effectivity dropping off dramatically as motor pace drops (under) and environment friendly motor management enabled by larger frequency GAN know-how (above). Supply: QPT
To cut back power wastage and increase effectivity, the chopping must be quick, transitioning from off to on or on to off as shortly as attainable. Subsequently, throughout the switching time, when the transistor is neither on nor off, power dissipation accounting for many of the power losses will be contained. It wastes little or no power chopping the DC into variable frequency AC to drive the motor throughout the entire vary of various speeds.
Two modules and a reference design
The primary module, qGaN, is constructed round a 650-V GaN transistor and the corporate’s qDrive low jitter remoted GaN transistor gate drive. The second module, qSensor, gives the sensing and management that allows the GaN to be pushed at tremendous excessive frequencies.
Determine 3 The qGaN module can deal with 15-A RMS present whereas driving 380-V three-phase motors. Supply: QPT
To offer design assist for these modules, QPT has developed the WisperGaN development system that features a reference design to point out engineers how the modules will be assembled in a Faraday cage in order that there aren’t any heating or RF points. In accordance with the corporate, it demonstrates as much as 80% discount in energy utilization in comparison with present options that function at a lot decrease frequencies.
QPT, primarily based in Cambridge, UK was based in 2020 as an unbiased energy electronics firm.
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