• • • ELECTRIC VEHICLES • • •
48V boost converter (K = 4/1) onto these accelerator cards, or within a distributed higher power 12V-to-48V module, enables AI capability and capacity to be installed very easily in older rack systems.
How to address demanding high-voltage applications that require isolation
Electric Vehicles
The addition of artificial intelligence in data centre racks has driven rack power above 20kW, which has made the use of a 12V PDN bulky and lower in efficiency. By using a 48V PDN, the same benefits can be achieved as with hybrid vehicles. In both automotive and data centre applications, the preference is to keep 12V legacy loads and PoL commodity buck regulators to minimize the amount of change.
Solving real world problems with non-isolated fixed-ratio
converters Because 48V is SELV compliant, a non-isolated fixed-ratio converter is a perfect choice for the 48V-to-12V DC-DC conversion stage, as today’s PoL 12V regulators can handle the variation in input voltage. A non-isolated, unregulated fixed- ratio converter is the most efficient high-power bus converter, which enables lower power dissipation, higher power density and lower cost. This high density allows new decentralised distributed power architectures in hybrid automobiles where non-isolated fixed-ratio converters can be placed near the loads, allowing maximum runs of a smaller and more efficient 48V PDN around the vehicle. In server blades, this small non-isolated 48V-to-12V fixed-ratio converter can be placed on the motherboard close to the buck regulators.
Many new AI accelerator cards such as the SXM from NVidia and the OAM cards from the Open Compute Project (OCP) members are designed with a 48V input due to the 500 – 750W power level of the AI processors. For these high- performance cards to be used by cloud computing and server companies who still use a 12V PDN backplane in their racks, requires a 12V-to-48V conversion. Adding a bidirectional K = 1/4 non-isolated fixed-ratio converter as a 12V-to-
In both the 400V/48V and 800V/400V applications and due to the high power requirements, a parallel array of isolated K: 1/8 (400/48) and K: 1/2 (800/400) fixed-ratio converters with high power density and efficiency above 98% can be used effectively. Regulation is provided either before or after the fixed-ratio converter stage. The power density and efficiency gains of not having regulation works well here in this very high-power application and simplifies thermal management.
High-performance computing Exascale High Performance Computing (HPC) systems use 380VDC as the main PDN because rack power levels typically exceed 100kW. In these applications, isolated fixed-ratio converters of K: 1/8 and K: 1/16 are integrated onto the server blades or on mezzanine cards distributed through the rack to deliver either 48V or 12V to the motherboards. Regulation is then provided by a 12V multiphase buck converter array or advanced higher-efficiency 48V-to-PoL architectures. The density and efficiency of the fixed-ratio converter again play a critical role in enabling this type of PDN architecture to deliver high performance.
Tethered Drones
Another high-voltage application that requires isolation is a tethered drone. Power cables for tethered drones can be over 400 meters in length,
electricalengineeringmagazine.co.uk
5G Communications The world is now equipped with 4G radio and antenna towers which have to be upgraded with new 5G systems which are 5x the power level of the 4G equipment. The 4G PDN is 48V and is delivered via a cable from a ground-based power system. The significant rise in power level with the addition of the 5G equipment would result in a very large diameter and very heavy power cable if the PDN were to stay at the 48V level. Telecommunications companies are currently looking at the advantage of using a 380VDC PDN, to significantly reduce the size of the cable. By using a bidirectional K 1/8 fixed-ratio converter in boost mode, the ground-based 48V power system can deliver 380V (K: 8/1) to the top of the tower. By using a 380V-to-48V regulated converter at the top of the tower, both 5G and 4G systems receive a regulated 48V supply and achieve lower-cost power delivery via a small 380V power cable.
Fixed-ratio converters provide PDN design flexibility for high-
performance applications High-performance power demands are on the rise. Advanced systems in enterprise and high- performance computing, communications and network infrastructure, autonomous vehicles and numerous transportation applications are just a few of the high-growth industries clamouring for more power.
These markets have a common thread: each has extreme power requirements and benefit from a small, power-dense DC-DC converter solution that can save space and weight. Power system engineers should consider fixed-ratio converters as an important and flexible solution for enabling higher-performing PDNs to gain a competitive advantage in overall system performance.
ELECTRICAL ENGINEERING • FEBRUARY 2022 29
In electric vehicle applications, the battery voltage has to be much higher than 48V that is presently used in hybrid vehicles due to the power demand, and 400V is a common choice. The 400V is then converted to 48V for distribution to the various loads around the powertrain and chassis. To support fast-charging, the 400V battery is charged from a charging station with a regulated 800V DC output via an 800V-to-400V converter.
which the drone has to lift and maintain to achieve its flying altitude. By using a high voltage such as 800V, the size, weight and cost of these bulk power cables are dramatically reduced, enabling higher-performance drones. Using an onboard fixed-ratio converter, typically K = 1/16, to convert to 48V provides a very small and highly efficient power delivery solution for the onboard electronics and video payloads.
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44
