“The power is transmitted from the power source to the various loads distributed in the Electronic system. This work is mainly done by the power distribution network (referred to as PDN). PDN is generally composed of cables, busbars, connectors, copper foil power layers in PCBs, power converters and voltage regulators. According to the voltage of the power distribution network, it is usually divided into low voltage (LV), high voltage (HV) and Ultra-high voltage (UHV) category three. With the increase of power consumption at the point of load, it has become a major trend to increase the voltage of the distribution network. Taking low-voltage PDN as an example, the upgrade from the traditional 12V to 48V system has always been the direction of power engineers in recent years.
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The power is transmitted from the power source to the various loads distributed in the electronic system. This work is mainly done by the power distribution network (referred to as PDN). PDN is generally composed of cables, busbars, connectors, copper foil power layers in PCBs, power converters and voltage regulators. According to the voltage of the power distribution network, it is usually divided into low voltage (LV), high voltage (HV) and Ultra-high voltage (UHV) category three. With the increase of power consumption at the point of load, it has become a major trend to increase the voltage of the distribution network. Taking low-voltage PDN as an example, the upgrade from the traditional 12V to 48V system has always been the direction of power engineers in recent years.
Why boost the voltage of the distribution network? This reason is easy to understand: after the system load power increases, according to the power formula P=I*V, the voltage remains unchanged and if you want to carry more power, you need to increase the current. On the one hand, the increase of the current will increase the power consumption during the power transmission process, and on the other hand, it will also require the use of larger-sized components (such as cables, connectors, and PCB boards), which will bring great impact on the overall performance of the system. big challenge. By increasing the distribution voltage, the current can be effectively reduced while carrying high power, and the power consumption, volume and cost of the entire system can be optimized.
Application of 48V Power Distribution System
New energy vehicles (including hybrid and pure electric vehicles) should be the most anticipated industry for 48V power distribution systems. The traditional car is based on the 12V system to supply power to the on-board electrical appliances, but with the increase of electronic equipment in the car, this low-voltage system becomes more and more stretched, especially after the electric start-stop function is added, the 12V system basically achieves performance. “limit”.
In future cars, the introduction of functions such as ADAS and autonomous driving will add more abundant sensors such as cameras, millimeter-wave radars, and lidars to cars, as well as higher-performance computing processing units—it is expected that future on-board computers will consume It is really difficult for the “small horse” of the 12V power distribution system to pull the “big car” of new energy vehicles. At this time, the 48V power distribution system has become an important technological change.
Another area with high hopes for 48V power distribution systems is data centers. In an intelligent society, data centers concentrate more and more computing resources and carry more and more computing tasks, especially the application of artificial intelligence (AI) technologies such as machine learning, which greatly increases the computing workload. This makes high-density deployment of high-performance processing units such as CPUs, GPUs, FPGAs, and ASICs a rigid need for data centers. This means that the power consumption of both a single processor and the overall computing processing system will continue to rise. Upgrading the server’s power distribution system from 12V to 48V is undoubtedly one of the most effective ways to meet this challenge.
In March 2016, Google released a CPU server based on the 48V architecture; in March 2018, Nvidia also released its 48V GPU server and board – these two landmark events are considered to be the sound of high-end server applications turning to 48V The horn of the system. At present, many new AI accelerator cards will have 48V input to support AI processor power levels of 500W to 750W.
Integration of 12V and 48V systems
However, although the prospect of 48V power distribution system is bright, it is not easy to achieve this goal. Considering the 12V system and equipment with perfect ecology and huge stock, in the process of moving towards 48V, how to make an efficient and reliable bridge between 12V and 48V system, and how to integrate 12V and 48V system together, is a must be seriously considered. the subject.
For example, in the automotive field, although the 48V power distribution system has obvious advantages, the 12V on-board equipment at the load end is still the mainstream, which requires a first-level voltage conversion bridge between the 48V power distribution bus and the 12V load point.
Figure 1: 48V/12V bridge application in a mild hybrid vehicle (Image credit: Vicor)
Looking at the data center again, one of the main application scenarios it faces is how to enable 12V traditional racks to use 48V high-performance (and high-power) AI accelerator cards. This is where a 12V to 48V bridge is required to add advanced AI capabilities to older rack systems. Of course, for data centers that have been upgraded to 48V systems, there is also a need to support the original 12V load, which requires a 48V to 12V bridge to complete.
Figure 2: 12V/48V bridging application in a data center server (Image credit: Vicor)
Choice of 12V/48V Bridge Scheme
In the choice of 12V/48V bridge technology scheme, fixed ratio converter is a very suitable architecture.
A fixed-ratio converter is a DC-DC converter with a fixed fraction of the output voltage to the input voltage, with the input-to-output voltage range defined by the device’s “turns ratio (also known as the K-factor).” This architecture determines a feature of fixed-ratio converters, which is capable of bidirectional power and voltage conversion. As shown in the figure below, this fixed-ratio converter can be used either as a buck converter with K=1/12 or as a boost converter with K=12/1. This two-way bridging feature brings great flexibility to the design.
Figure 3: Fixed-ratio converter architecture (Image credit: Vicor)
On the other hand, fixed-ratio converters do not have voltage regulators, so they can achieve very high efficiency, resulting in higher power density and lower power dissipation, which can provide great benefits for thermal management of the system. Great convenience. The voltage regulation function of the point of load can be completed by the downstream DC-DC regulator. Such a system architecture is conducive to achieving better performance and system cost.
Furthermore, according to different design requirements, fixed ratio converters can be expanded into different product portfolios. For example, in high-voltage power distribution systems, fixed-ratio converters with isolation can be selected; while in 48V, a safe low-voltage system suitable for SELV environments, non-isolated devices can be used.
In conclusion, the advantages of high density, high efficiency and flexible architecture make fixed ratio converters an ideal solution for 12V/48V bridging.
High-efficiency, miniaturized solutions
Vicor’s NBM2317 is a bus converter that supports efficient 12V and 48V bridging in power distribution systems. It can provide 800W of continuous power and support 1kW of peak power with an efficiency of 97.9%!
Figure 4: NBM2317 bus converter (Image source: Vicor)
NBM2317 supports bidirectional voltage conversion, and both directions provide processing capabilities with the same efficiency: K=1/4 in buck operating mode, rated output current 60A in continuous state, transient up to 100A (maximum 2ms); K=4/1 in voltage mode, rated output current is 15A in continuous state, and transient is 25A (maximum 2ms). The NBM2317 can also be easily paralleled for higher power stages.
Housed in a 23mm x 17mm x 7mm surface mount package, the bus converter is compact and can achieve up to 4.5kW/in3power density. At the same time, it requires very few external components, which also facilitates the “slim down” of the entire power system.
Other advantageous features of NBM2317 include: switching frequency of 1.7MHz, low noise, fast transient response, bidirectional startup and steady-state operation, etc., it can be said to achieve high efficiency, high density, miniaturized 12V / 48V bus bridge conversion ideal choice.
Figure 5: Block diagram of a typical buck application for the NBM2317 (Image source: Vicor)
Figure 6: Block diagram of a typical boost application of the NBM2317 (Credit: Vicor)
last words
The pursuit of higher performance and richer functions is driving the PDN distribution network in electronic systems to upgrade to higher voltages. In this process, how to provide a solution that takes into account high power, high efficiency, miniaturization and low cost is the dream of many power supply engineers.
Using fixed-ratio converters as a solution to achieve higher performance PDNs can lead to significant advantages in overall system performance and greater design flexibility. As an excellent “work” in fixed ratio converters, Vicor’s non-isolated bus converter NBM2317 can achieve bidirectional bridge conversion between traditional 12V and next-generation 48V power systems, resulting in a high power density and very cost-effective Advantages of modular distributed power supply architecture.
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