AC/DC Power Adapters using GaN (Gallium Nitride) — Desktop & Wall-Mount

This is a page explaining AC/DC Power Adapters — Desktop & Wall-Mount and switching power supplies equipped with GaN (Gallium Nitride) ICs, known as next-generation semiconductors. It is used in the USB-PD adapters developed by Unifive.

What are Next-Generation Semiconductor GaN AC/DC Power Adapters — Desktop & Wall-Mount?

What is GaN?

GaN PD-equipped USB AC/DC Power Adapters — Desktop & Wall-Mount, which are now commonly seen in retail stores, use a next-generation material called Gallium Nitride (GaN). GaN is a material gaining attention for its revolutionary impact in the field of power electronics. For decades, silicon-based MOSFETs (metal-oxide-semiconductor field-effect transistors) have played a crucial role in energy-to-electricity conversion and have become essential in modern life. However, improvements in conventional silicon MOSFETs and their power efficiency have approached theoretical limits, leaving little room for further enhancement with current technologies.

Moreover, in recent years, the demand for higher power density and efficiency has increased. Developed countries, aiming to prevent environmental degradation, have introduced regulations aligning with current trends. Silicon as a material has limitations in adapting to these environmentally conscious trends. GaN, on the other hand, is well suited to meet demands for improvements in efficiency, performance, and power density, making it a growing alternative as the core of next-generation power switching technology.

So, what is Gallium Nitride?

Gallium Nitride does not exist naturally. It is typically obtained as a by-product when refining aluminum from bauxite ore or producing zinc from sphalerite. This results in very low CO2 emissions during its extraction and purification. Over 300 tons of gallium are produced worldwide annually, with estimated reserves exceeding 1 million tons. As it is obtained as a by-product, its cost is relatively low—around 300 dollars per kilogram—about 1/200 the price of gold, which costs approximately 60,000 dollars per kilogram.

In addition to environmental benefits, GaN is a binary III/V direct transition semiconductor suitable for high-power transistors operating properly even at high temperatures.

History of GaN

Pure gallium has a melting point of only 30°C and can melt in the palm of your hand. It took another 65 years after its discovery to first synthesize gallium nitride. Until the 1960s, it was not possible to grow single-crystal GaN films. The melting point of the GaN compound is over 1,600°C, which is 200°C higher than silicon.

In 1972, LED technology based on magnesium-doped GaN was born. This was a breakthrough. Although initial commercial brightness was insufficient, it was the first LED capable of emitting blue-violet light.

Since the 1990s, GaN has been widely used in light-emitting diodes (LEDs). GaN emits blue light and is used in Blu-ray Disc readers. GaN is also utilized in semiconductor power devices, RF components, lasers, and photonics. In the future, it is expected to be used in sensor technologies as well.

In 2006, production began of enhancement-mode GaN transistors (also called GaN FETs), achieved by growing thin GaN films on AlN layers on standard silicon wafers using Metal-Organic Chemical Vapor Deposition (MOCVD). The AlN layer serves as a buffer between the substrate and GaN. This method enables GaN transistors to be produced in existing silicon fabs using nearly identical manufacturing processes. Utilizing familiar processes allows low-cost production similar to silicon and lowers the barriers to adopting compact transistors with significantly improved performance. For more detail, all semiconductors have what is called a bandgap—an energy range within a solid where no electron states can exist. Simply put, the bandgap determines how well a solid material conducts electricity. Silicon has a bandgap of 1.12 eV, while GaN has a wider gap of 3.4 eV. A wide bandgap means GaN can withstand higher voltages and temperatures than silicon MOSFETs.

This wide bandgap enables GaN to be applied to high-power and high-frequency optoelectronic devices. GaN functions at much higher voltages and temperatures than Gallium Arsenide (GaAs) transistors, making it ideal for power amplifiers in microwave and terahertz (ThZ) devices used for imaging and sensing.

Advantages of GaN

What benefits come from using GaN, a material that enables high-power and high-frequency applications in optoelectronics, in AC/DC Power Adapters — Desktop & Wall-Mount? Let us explain the advantages of incorporating GaN into AC/DC Power Adapters — Desktop & Wall-Mount.

GaN is frequently compared with silicon-based components. Currently, silicon-based MOSFETs are the standard and are widely used in power supplies for AC/DC conversion, DC/DC conversion, and motor control devices, with power ranging from a few tens of watts to hundreds or thousands of watts. Parameters such as packaging, on-resistance RDS, voltage rating, and switching speed have continually improved.

However, the performance of silicon-based semiconductors has neared theoretical limits despite decades of astounding advancements, leaving minimal room for further enhancements. In contrast, GaN-based power devices are high-electron-mobility transistors with higher critical electric field strength than silicon. This means GaN has a higher electric field strength than silicon, and when comparing components with the same on-resistance and breakdown voltage, GaN devices can be smaller than their silicon counterparts.

GaN FETs offer extremely fast switching speeds and excellent reverse recovery properties, which are essential for low loss and high efficiency. Currently, 600/650V GaN FETs are widely available on the market.

The advantages of using them in AC/DC Power Adapters — Desktop & Wall-Mount can be broadly summarized in the following three points.

Effect on Heat Generation

GaN materials have a wider bandgap, resulting in higher thermal conductivity than silicon. This enables GaN-based devices to operate at higher temperatures and be more efficiently cooled, helping AC adapters stay cooler and protected from thermal damage.

Miniaturization Through High Power Density

GaN parts enable higher switching frequencies and operating temperatures than silicon components. As a result, heat sinks can be made smaller, and components like fans for cooling or large magnetic components can be eliminated. Higher switching frequencies in GaN components also allow for smaller inductors and capacitors in power circuitry. This can lead to fewer embedded components and a more compact housing size for the AC/DC Power Adapters — Desktop & Wall-Mount.

Reduced Acoustic Noise and Wireless Power Transfer

Higher frequencies reduce acoustic noise in motor-driven applications. Additionally, high-frequency operation enables wireless power transfer at higher output levels, increasing spatial freedom and allowing a wider air gap between transmitters and receivers. This technology is currently being explored for electric vehicle charging systems.

GaN-Equipped AC/DC Power Adapters — Desktop & Wall-Mount Developed by Unifive

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