High-voltage LED lighting has proven to be a viable replacement for previous technologies such as high-intensity discharge (HID) lighting. With the adoption of high-voltage LED lighting, many manufacturers rushed to production and implementation in a variety of applications. While there was a significant increase in light quality and power density, efficiency has become an important aspect to address. Also, early applications saw failure rates that were much higher than expected. The main challenge of high-voltage LED lighting is to continue to increase power density and efficiency as well as making it reliable and more affordable for future applications.
In this article, wide bandgap (GaN) technology will be covered and how it can address the efficiency and power density challenge for high-voltage LED lighting. This discussion will show how wide bandgap technology can be used to maximize the efficiency and power density, with a focus on the buck portion of the LED driver architecture shown in Figure 1. Wide bandgap (GaN) semiconductors can operate at higher switching frequencies compared to conventional semiconductors like silicon. Wide bandgap materials require a higher amount of energy to excite an electron to have it jump from the top of the valence band to the
bottom of the conduction band where it can be used in the circuit. Increasing the bandgap, therefore, has a large impact on a device (and allows a smaller die size to do the same job). Materials like Gallium Nitride (GaN) that have a larger bandgap can withstand stronger electric fields. Critical attributes that wide bandgap materials have are high free-electron velocities and higher electron field density. These key attributes make GaN switches up to 10 times faster and significantly smaller while at the same resistance and breakdown voltage as a similar silicon component. GaN is perfect for high-voltage LED applications, as these key attributes make it ideal for implementation into future lighting applications.
Figure 1: System architecture of a non-isolated high-power LED driver. (Image source: STMicroelectronics)
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