How GaN is revolutionising power supply design

Evolution of power supply design: from Si to GaN

The best way to understand the impact of GaN within power supply design is to directly compare the technology to its predecessor, silicon. Doing so highlights several key differences and improvements that are contributing to this revolution in design:

Efficiency

GaN transistors have significantly lower switching and conduction losses compared to traditional silicon transistors. This means that higher overall efficiency can be achieved, particularly at high frequencies or in high power applications.

Comparatively, silicon power supplies typically have higher losses, especially as the frequency increases. This can limit efficiency, particularly in compact designs where thermal management is challenging, snowballing challenges.

Form factor

The high efficiency and switching speed of GaN devices allow for smaller passive components, such as inductors or capacitors, and significantly reduced cooling requirements. This means that power supplies can be designed in far more compact ways, whilst also being generally lighter.

Silicon-based designs will almost always require larger heatsinks and magnetic components to manage the additional heat generated and maintain consistent performance. This results in significantly bulkier and heavier power supplies.

Thermal management

Owing to the reduced losses that GaN provides, far less heat is generated by GaN-based power supplies. These power supplies can operate at higher temperatures without the need for extensive cooling systems. This benefits the power supply in many ways, not just for its thermal performance, improving reliability and form factor.

Meanwhile, the higher losses in silicon devices lead to greater heat production, necessitating more robust thermal management solutions, which can increase size and complexity.

Switching speed

GaN transistors can switch much faster than silicon transistors, often in the range of several MHz. This capability reduces the size of passive components and improves transient response.

Silicon transistors on the other hand have slower switching speeds, which limits their performance in high-frequency applications and increases the size of passive components by some margin.

Reliability and longevity

The improved thermal performance and reduced electrical stress in GaN devices enhance their reliability and lifespan, making them suitable for high-performance and harsh environment applications.

While silicon technology is mature and well-understood, it generally has a lower reliability and shorter lifespan in high-power, high-frequency applications due to greater thermal and electrical stress.

Overcoming GaN’s teething problems

Despite the plethora of advantages GaN offers for power supplies, like all new technologies, there are teething problems that must be overcome to make the most of its potential and facilitate broader adoption.

For starters, thermal management is both a positive and a challenge for GaN. Whilst there is less heat generated overall in GaN-based power supplies, the heat that is generated is more concentrated. The high-power densities mean that these devices can still pose thermal management challenges.

Electromagnetic interference (EMI) is another significant challenge in GaN power supplies due to high switching frequencies and fast transients, which generate more high-frequency harmonics and noise. These can lead to conducted and radiated EMI, affecting both the power supply and nearby electronics. The physical layout, including minimising parasitic elements, becomes crucial to controlling EMI. Compliance with EMI standards often requires additional filtering, shielding, and careful grounding. Techniques such as optimising PCB layout, incorporating EMI filters, and using soft switching methods are employed to mitigate these issues, though they may add to the design's complexity and cost.

Finally, there are the cost and reliability concerns to address, something that will only come with time. Although GaN devices can offer improved reliability, there is still limited long-term data on their performance in various environments. Ensuring the robustness of GaN devices under different conditions, such as extreme temperatures and electrical stresses, is essential for critical applications and something that is being actively proven today. GaN devices are generally more expensive than silicon-based counterparts. The higher cost is due to the complexity of the manufacturing process and lower production volumes. As the technology matures and production scales up, costs have been consistently decreasing, but price remains a barrier for some applications.

Conclusion

In conclusion, Gallium Nitride (GaN) is poised to revolutionise power supply design, offering significant advantages over traditional silicon-based systems. The superior efficiency, compact form factor, improved thermal management, and faster switching speeds of GaN devices enable the development of more efficient, reliable, and compact power supplies. However, the adoption of GaN technology is not without challenges, including the management of concentrated heat, electromagnetic interference, and the current cost and reliability considerations. As these issues are addressed, GaN's potential will be fully realised, paving the way for broader adoption across various industries and applications, and marking a significant shift in the future of power supply design.