■ Benefits of GaN in Various Applications

Today, the biggest challenge for the power electronics industry is the need to constantly pursue the goals of securing price competitiveness and reducing product size while satisfying the growing demands for improved efficiency and power performance.

The introduction of gallium nitride (GaN) technology, a relatively new wide-bandgap compound, is moving in that direction, and usage is rapidly increasing as commercialization expands.

High Electron Mobility Transistor (HEMT) devices that outperform silicon devices in terms of Performance Index (FOM), On-Resistance RDS(on), and Total Gate Charge (QG) are GaN-based and provide high drain-source voltage capacity, zero reverse recovery charge, and very low intrinsic capacitance.

The first and most widely used application of GaN technology was power conversion. GaN provides leading solutions that improve efficiency to meet even stringent energy requirements. Thanks to the ability to operate at higher switching frequencies, power density is higher, which ultimately leads to a reduction in the overall size and weight of the system and even lower costs.

Size and power efficiency are also important in electronic motor design. Minimizing conduction and switching losses in the drive unit is key to reducing energy waste.

As silicon technology reaches theoretical limits for power density, breakdown voltage, and switching frequency, it is becoming increasingly difficult to improve the performance of motor drivers using conventional silicon MOSFETs and IGBTs. GaN transistors are a valid alternative to MOSFETs and IGBTs in high-voltage motor control applications due to their superior electrical characteristics.


■ The Driving Force of Next-Generation Motor Inverters

GaN is expected to provide significant advantages even in applications operating at low frequencies (up to 20 kHz). In the home appliance sector, motor-driven systems such as washing machines, refrigerators, air conditioners, and vacuum cleaners rely heavily on motor inverters to control speed, torque, and efficiency. Unlike industrial servo or precision motors, the physical size of these motors is generally fixed due to mechanical and functional constraints. Therefore, conventional methods of reducing the overall system size by shrinking the motor itself cannot be used. Instead, improvements must be made in the inverters and power electronic devices that drive these motors.

In this sense, it is necessary to point out that the superior advantages of GaN over conventional silicon transistors stem not from a single parameter, but from multiple parameters. This is the result of the combination of various aspects.

GaN possesses virtually negligible reverse recovery charge (Qrr) and low parasitic capacitance, allowing it to operate even with slightly higher voltage variations. While motor windings and insulation limit the maximum allowable voltage change rate, GaN's ability to operate at higher switching speeds enables designers to meticulously optimize switching edges.

In addition, dead time can be safely and significantly reduced without the risk of shoot-through defects. The time between high-side and low-side switching can be easily reduced to one-tenth. This makes it possible to improve inverter efficiency and reduce switching losses without compromising motor stability.

Surprisingly, the explanation of performance doesn't end here. In fact, all these 'minor' improvements combine to lead to the most significant achievement: the removal of the heatsink.

■ Elimination of the need for a heatsink

With power dispersion significantly reduced, designers can now reduce or eliminate bulky heatsinks at the inverter power stage. The number of steps in the assembly process is also reduced. Since there are no heatsinks, there are no screws or mounting joints, which prevents mechanical failures that can occur when the device is deployed in the field for extended periods. There is also notable potential here, as it enables reductions in service and warranty costs.

As a result, it has become possible to design smaller, lighter, and more cost-effective inverters, enabling better meeting of the demanding and highly competitive home appliance market.


Looking at the waveform, one can see how stable the GaN waveform is and how low the temperature is. In the example above, the typical RDS(on) of the device under test is 80 mΩ. The motor inverter operates at a switching frequency of 16 kHz, and the maximum voltage change is slightly lower than 10 V/ns.

Power levels of approximately 800W can be safely achieved without thermal runaway. The temperature rise Δt is less than 70°C, providing ample margin before reaching the maximum operating junction temperature (TJmax) of 150°C.

This amazing result was achieved without a heatsink, and the GaN is mounted on a standard 2-layer PCB for cooling.

■ STPOWER GaN Transistor

STPOWER GaN transistors are normally off p-GaN gate e-mode transistors with no reverse recovery charge. ST currently offers seven products with a 700V breakdown voltage (VDS) rating with typical on-resistance RDS(on) of 53mΩ to 270mΩ in DPAK, PowerFlat 8x8, and TO-LL packages.

The product portfolio is growing rapidly by adding various package, RDS(on), and breakdown voltage specifications.


Additional information can be found at https://www.st.com/en/power-transistors/powergan.html .


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