While the automotive industry has been struggling for several months in light of ongoing chip shortages, other industries are taking the hit as well—notably, the crypto mining market.
One of the primary concerns in the cryptocurrency market is the massive electricity consumption involved in mining operations. Because of the exorbitant cost of energy, many professional miners attempt to find a suitable geographical location for their mining farm where the cost of electricity is relatively lower.
Crypto mining farm. Image used courtesy of Transphorm
Why exactly does cryptocurrency mining burn so much power? And accounting for this high consumption, how might power supply units (PSUs) employed in mining applications be different from general-purpose PSUs?
Mining Involves Computation-intensive Operations
Bitcoin is a decentralized cryptocurrency. It uses a distributed ledger technology to ensure the security of the system. When a transaction is made by people who send or receive bitcoins, the responsibility of validating the transaction is spread among many users all over the world.
To securely verify these transactions, powerful CPUs, GPUs, or ASICs are employed to solve increasingly difficult cryptographic equations. Mining servers contribute their computational power to the bitcoin network to solve these equations and validate the transactions. As a reward, the bitcoin network pays miners for their time and equipment.
ASICs have been proven to be more efficient than CPUs, CPUs, or FPGAs in crypto mining applications. Image used courtesy of Bitcoin
The greater the computational power of a miner, the greater the received compensation. Consequently, individuals and corporations build megawatt bitcoin mining servers, also known as mining data centers, to increase their chances of earning more bitcoins.
How Much Energy Is Consumed?
The powerful processors employed in the mining servers are power-hungry and work for long periods of time, leading to a significant amount of power consumption. Hence, mining farms have an extremely high, ongoing energy cost that should be minimized to maximize return on investment.
According to Cambridge research, the global energy consumed during bitcoin mining operations is about 121.36 terawatt-hours (TWh) a year and exceeds the annual energy consumption of Argentina.
Power consumption of countries compared to bitcoin. Image used courtesy of the BBC
The PSU Efficiency Rating Is a Key Factor
Without lowering the cost associated with electricity consumption, mining can actually cause miners to lose money. That’s why miners need to employ power supply units (PSUs) with high conversion efficiency.
The efficiency rating can be used to determine how much of the power drawn from the wall socket is delivered to electronic equipment. For example, a PSU with 80% efficiency that delivers 800 W to the load will actually draw 1000 W of power from the wall socket. In this example, 200 W of power will be wasted as heat in the conversion process.
With a PC system, upgrading to a more efficient PSU might not yield remarkable annual savings. However, this is not the case when dealing with power-hungry mining rigs that operate 24/7. Usually, PSUs with an efficiency rating of 80 Plus Gold or above are recommended for mining applications.
As shown below, an 80 Plus Gold PSU has at least 87% efficiency at 20% load, 90% efficiency at 50% load, and 87% efficiency at 100% load.
Efficiency of different PSU ratings. Image used courtesy of Nicehash
Mining PSUs Usually Operate in Harsh Environments
Many mining farms are built near power plants with harsh environmental conditions. Humidity is higher near a hydroelectric power plant, and the high humidity along with a high operating temperature can reduce a PSU’s lifespan.
Besides, in the regions close to power plants, the PSU’s input voltage experiences a higher variation, and lightning strikes are also more frequent. That’s why mining farms need to employ highly-efficient power supply units that can reliably perform in harsh environments. Preventing downtime is critical because time carries a significant dollar value in crypto mining.
System Reliability Takes a Hit From Inefficient Thermal Design
Power-hungry processors in mining facilities can generate excessive amounts of heat. Although techniques such as heavy-duty cooling fans, HVAC systems, or water chillers can be used to handle the heat, these systems are not usually employed in mining farms due to their high costs and energy consumption.
As an alternative, those at crypto mining farms might instead turn to other thermal management techniques. The TI document “Using DC/DC Controllers to Improve Bitcoin Miner Designs” presents two such options. In it, the company compares the thermal performance of two different power designs: 1) a board based on a highly-efficient buck controller, the LM27402, which uses external FETs and 2) a board that uses a buck converter, the TPS548B22, with integrated MOSFETs.
In general, integrated solutions are better options because they require fewer external components and are usually more reliable. However, TI does note that in mining applications, a discrete power design can achieve higher thermal performance. This is because a discrete solution keeps the power MOSFETs and the heat generated by them further away from the controller.
Thermal performance of a board based on LM27402 (left) and TPS548B22 (right). Image used courtesy of Texas Instruments
The board employing the integrated solution based on the TPS548B22 has a maximum temperature of 55.6°C; however, the board that uses external power MOSFETs has a maximum temperature of 43°C. Since the latter design places power MOSFETs further from the controller, it achieves a lower maximum temperature and consequently, higher reliability.
GaN: a Promising Power Element for Mining Applications
Although GaN devices have some limitations, they may be the power transistor of choice in future mining servers. These devices switch at much faster speeds compared to silicon super-junction MOSFETs. A higher switching frequency can shrink the size of the magnetics and lead to a smaller board compared to conventional silicon solutions. Additionally, GaN devices feature lower on-resistance and zero reverse recovery, resulting in more energy-efficient solutions which, as discussed above, is a key factor in mining applications.
Transphorm Inc., a semiconductor company focused on GaN devices for switched-mode power supplies, recently announced that its GaN devices are optimized for high-performance PSUs used in cryptocurrency mining applications.
Comparison of Transphorm’s GaN cascode to other conventional e-modes. Image used courtesy of Transphorm
The company claims that its devices are highly reliable and have yielded a FIT rate of < 1—meaning less than 1 part per billion hours fails in field applications. These devices are driven just like common silicon super-junction MOSFETs with off-the-shelf gate drivers.
The Future of PSUs in Crypto Mining
Power supply units, and particularly GaN-based PSUs, may play a pivotal role in mining data centers should cryptocurrency remain on its current trajectory.
Just as NVIDIA recently announced a new GPU line dedicated to crypto mining, so too has Transphorm tapped into GaN PSUs expressly designed for this power-intensive application. It’s possible that more manufacturers will hop on board with mining-specific components to conserve offerings for less demanding computing applications.
Have you ever dabbled in hardware design for cryptocurrency mining? What challenges did you face with the massive energy consumption? Share your thoughts in the comments below.