Four Medium Voltage Applications that Will be Innovated by Gallium Nitride in Electronic Design

    With the rapid development of technology, people‘s demand for power is also constantly increasing. In order to sustainably promote this development, renewable energy sources such as solar energy are increasingly being used for grid power supply. Similarly, in order to achieve faster data processing, big data storage, and artificial intelligence (AI), the demand for servers is also growing exponentially. Given these trends, designers face a significant challenge: how to achieve higher power within the same size while continuously improving design efficiency.    

    This challenge has driven the widespread application of gallium nitride (GaN) in high-voltage power supply design, as GaN has two major advantages:

    • Increase power density. The high switching frequency of GaN allows designers to use smaller passive components such as inductors and capacitors, thereby reducing the size of the circuit board.

    Improve efficiency. Compared to silicon design, GaN‘s excellent switching and conduction loss performance can reduce losses by more than 50%.

    In addition to the high-voltage GaN (rated value>=600V) already adopted in the industry, new medium voltage GaN solutions (rated value 80V-200V) are also increasingly popular, which can achieve higher power density and efficiency in power systems that were not supported by high-voltage GaN before.

    This article will elaborate on four major medium voltage application areas, which are gradually adopting GaN technology.
Application field 1: Solar energy
    Solar energy is the fastest growing renewable energy source, with a growth rate of 26% from 2021 to 2022. It is expected that solar energy utilization will develop at a compound annual growth rate of approximately 11.5% in the next seven to eight years. As the number of solar panels installed increases, people‘s demand for system efficiency and power density will also increase, as this is a technology that requires high space requirements. For solar panel subsystems, LMG2100R044 and LMG3100R017 devices help reduce system size by more than 40%.
    Solar energy is mainly achieved through two sub systems of solar panels: one is a boost stage followed by an inverter stage, which converts the DC voltage range into AC voltage (as shown in Figure 1); Another type is the step-down and step-up stages, where the power optimizer converts the constantly changing DC voltage into a common DC voltage level (using maximum power point tracking) for delivery to the series inverter (as shown in Figure 2).

Figure 1 Block Diagram of Micro Inverter

Figure 2 Power Optimizer Block Diagram

Application Area 2: Server
    Considering that we are still in the early stages of the artificial intelligence revolution, the demand for servers will grow exponentially in order to run complex machine learning algorithms and achieve storage of larger and more complex datasets. A high-density design that requires efficiency above 98% for each level will be able to meet these enhanced processing and storage requirements.
    As shown in Figure 3, the three main systems in server power applications can use GaN ranging from 100V to 200V:
    Power supply unit (PSU). The changes in open computing projects are increasing the popularity of 48V output; However, the losses (gate drive and overlap losses) required for 80V and 100V silicon solutions have significantly increased compared to previous solutions. GaN solutions such as LMG3100 help to minimize the aforementioned losses in inductor capacitor stage (LLC stage) secondary side synchronous rectifiers as much as possible.
    Intermediate Bus Converter (IBC). This system converts the intermediate voltage (48V) output by the PSU into a lower voltage, which is then transmitted to the server. With the popularity of 48V voltage levels, IBC helps reduce I2R losses in server subsystems and reduces the size and cost of busbars and power transmission lines. The disadvantage of IBC is that it adds another step in power conversion, which may affect efficiency. Therefore, in addition to several new topologies that have been tested by OEMs to achieve the best combination of high efficiency and high power density, it is essential to fully utilize efficient GaN devices such as LMG2100 and LMG3100.
    Battery backup unit. The step-down/step-up stage usually converts the battery voltage (48V) to the bus voltage (48V). When the mains power line loses power and the power flow is bidirectional, you can also use a battery backup unit for battery power conversion. The reason why uninterruptible power supplies use this level is because it only performs a direct DC/DC conversion through the battery, avoiding losses caused by DC/AC/DC conversion.

Figure 3 Server Power Block Diagram

Application Area 3: Telecommunications Power Supply
    In telecommunications radio equipment, the power supply may adopt GaN design. Due to the fact that radio equipment is usually installed outdoors and relies solely on natural cooling, high efficiency is particularly important. In addition, with the gradual development of mobile networks such as 5G and 6G, the demand for accelerating network speed and data processing is also increasing, thus requiring high-density designs with extremely low losses. LMG2100 helps to increase the power density of such designs by more than 40%.
    In typical medium voltage applications, GaN converts a negative battery voltage level (usually -48V) power supply using a reverse buck/boost or forward converter topology to a+48V power supply suitable for power amplifiers, or uses a buck converter topology to power field programmable gate arrays and other DC loads.
Application Area 4: Motor Drive
    That‘s right, you can use GaN in motor drive circuits, which has a wide range of applications, including robot, electric tool drive, and two wheel traction inverter design with different load curves. The zero reverse recovery characteristic of GaN (because there is no body diode) leads to unstable reverse bias current of the diode, thereby reducing dead zone loss and improving efficiency. As mentioned earlier, GaN has a higher switching frequency and lower current ripple, which can reduce the size of passive components and achieve smoother motor drive design.
    Figure 4 shows how to add GaN to the motor drive unit.

Figure 4 Motor Drive Unit Block Diagram

epilogue
    In various medium voltage applications, GaN has the potential to replace traditional silicon FETs. Other application areas for 100V to 200V GaN include general-purpose DC/DC conversion, Class D audio amplifiers, and battery testing and formation equipment. In addition, GaN can also provide higher switching frequency and lower power loss, which are particularly prominent in integrated power supply stages that simplify power supply design.
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