Power semiconductors are an important part of efficient power conversion. In fact, power conversion systems exist in all modern electronics, including industrial, automotive, consumer, medical or aerospace applications. They are mainly found in power supplies, lighting controls, and motor drives.
According to Yole Développement, revenues for the power device market in 2017 were approximately $30 billion, with more than half of the revenue coming from power ICs. By 2022, revenue in this market is expected to grow to about $35 billion.
With the rapid improvement of the global standard of living, the demand for electricity is also growing accordingly. In order to reduce the environmental impact of nuclear power, wood, coal, and gas-fired power plants, we must use electricity efficiently. In addition, with the increasing demand for computer processing power, automobile fuel economy, driving distance of electric vehicles and drones, and energy consumption of lamps, people will be cheaper and smaller in the foreseeable future. The demand for more efficient power systems will continue to grow steadily.
Data center power consumption is incredible, requiring efficient power architecture and superior power conversion technology
Data centers and telecommunications systems are key members of the electronic infrastructure and are relevant to our daily lives. As technology is integrated into our lives, we take it for granted, but like icebergs, we don’t see much of the electronic infrastructure. The hardware portion of these infrastructures contains millions of microprocessors, data memories, output data buses, and auxiliary logic.
Each processor may contain billions of tiny integrated transistor circuits. These tiny devices use very little power and typically operate from a few volts to less than 1V. And the data center can use thousands of processors, which means that trillion transistors are used at the same time! Therefore, the power required by the data center will be from several megawatts to tens of megawatts. Currently, the power required by the data center is 4160V three-phase AC voltage or 13.8kV. This is completely inappropriate for information processing hardware that requires very low voltages and fairly accurate voltages. Therefore, we must find an efficient power supply architecture and use superior power conversion technology to efficiently step down to 1V.
In fact, electricity is expensive, and the power consumption of the data center is staggering. If a voltage conversion ratio greater than 1000:1 is to be achieved, multi-stage power conversion must be used, and in each stage of the power conversion process, some energy is lost, thereby increasing the cost of the entire system. The energy lost is heat and must be removed. This requires effective heat management, usually using air conditioning, but this will drive up electricity consumption and further increase costs. Efficient power conversion can significantly reduce electricity bills, and electricity bills are the biggest cost of the data center. By 2020, we expect total energy consumption in the US data center to reach 73 billion kWh, making it impossible to use an inefficient power supply architecture.
During these years, the industry has been paying attention to shift point applications from 48V bus voltage to voltages typically 1V or below. The last level of power conversion is the most difficult, and currently the least efficient, about 15% of the total energy is lost. If you can use this energy for digital chips, you can increase your income.
GaN achieves significant performance gains while still achieving an efficiency of approximately 300 times before reaching its limits
Many engineers asked about the similarities and differences between gallium nitride (GaN) and silicon carbide (SiC). Both GaN and SiC are wide bandgap semiconductors, so more power than silicon can be handled in smaller, faster devices. An additional advantage of GaN is the ability to generate two-dimensional electron gas (2DEG) on the surface of the device. This 2DEG allows the lateral GaN device to conduct electrons faster and has a lower resistance than Si or SiC. All electrical connections of the directional device are on the same plane as the active device. Different applications have different voltage requirements. When the voltage requirement exceeds 600~900V, the lateral device will not work. Vertical GaN devices (electrically connected at the top and bottom) have no 2DEG, so their performance is closer to SiC. As vertical SiC diodes and transistors become more mature, SiC is expected to dominate applications above 900V. However, in general, the market below 900V is larger, which is also the market that EPC is currently responding to.
GaN devices are just beginning to emerge in the field of power conversion. It is worth noting that power transistors have made significant progress in the past few years, and the on-resistance has been greatly improved. Even so, the best silicon-based GaN transistors on the market today are much better than the theoretical limits of Si, and can still increase efficiency by about 300 times before reaching their limits.
Silicon-based GaN technology is also a very good candidate for integration. Now, we have a single-chip half-bridge device based on silicon-based GaN. There will be complete system-on-a-chip (SoC) power devices in the future, and discrete transistors can be essentially discarded in power conversion applications.
to sum up
The emergence of GaN power devices has changed the rules of the game in the industry. Compared to solutions based on traditional silicon MOSFET devices, GaN-based devices are more efficient, have smaller footprints, and are less expensive.
The common goal of our industry is to create a superior data center with every new design that achieves energy savings, lower cost, and greater efficiency. More and more companies are manufacturing DC/DC power conversion products based on GaN technology, so it can be expected that a more efficient and cost-effective future will start now!
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