HomeElectronics5 main tendencies in energy provide design for servers

5 main tendencies in energy provide design for servers

As a result of servers are important for dealing with knowledge communications, the server trade has grown exponentially in parallel with the Web. Though server items have been initially primarily based on a PC structure, a server system should be capable of deal with the rising quantity and complexity of community hosts.

Determine 1 reveals a typical rack server system in an information heart and a block diagram of a server system. Energy provide items (PSUs) are on the coronary heart of a server system and require a fancy system structure. This text will study 5 server PSU design tendencies: energy finances, redundancy, effectivity, working temperature, and communication and management.

Determine 1 A server system block diagram is proven together with how a server is positioned in an information heart. Supply: Texas Devices

  1. Energy finances

Within the early 21st century, the ability finances of a rack or blade server PSU was within the 200- W to 300-W vary. At the moment, energy consumption per central processing unit (CPU) was within the 30- W to 50-W vary. Determine 2 reveals CPU energy consumption tendencies.

Determine 2 The CPU energy consumption tendencies are proven for the early 21st century. Supply: nap.nationalacademies.org/learn/12980/chapter/6#87

At present, a server CPU’s energy consumption is round 200 W—with thermal design energy closed to 300 W—significantly rising the server PSU’s energy finances to a spread of 800 W to 2,000 W. So as to assist increasingly server computation necessities resembling cloud computing and synthetic intelligence (AI) calculations on the Web, servers can embrace graphics processing items (GPUs) to work alongside CPUs. This inclusion might improve a server’s energy demand past 3,000 W inside 5 years. Nonetheless, since most rack or blade server PSUs are nonetheless utilizing an AC inlet with as much as a 16-A present ranking, they’ll have restricted energy budgets: round 3,600 W at a 240 VAC enter, accounting for converter effectivity. So, 3,600 W will nonetheless be a server rack PSU’s energy restrict within the close to time period.

For the info heart energy shelf, server PSU designers broadly apply the Worldwide Electrotechnical Fee (IEC) 60320 C20 AC inlet with 20-A present ranking. PSU energy budgets are restricted by their AC inlet present ranking, which permits about 3,000 W in in the present day’s knowledge heart PSUs; however within the close to future, an information heart PSU’s energy degree might improve to over 5,000 W. To permit the next energy finances per PSU and obtain greater energy density, you may also use a busbar for the AC inlet to extend the enter present ranking.

  1. Redundancy

The significance of reliability and availability in a server system necessitates redundant PSUs. If a number of PSUs fail, different PSUs within the system can take over to ship power.

A easy server system can have 1+1 redundancy, which means that there’s one energetic PSU and one redundant PSU within the system. A posh server system may need an N+1 or N+N (N>2) redundancy, relying on system reliability and value issues. So as to hold the system working usually when a PSU must be changed, the system wants a hot-swap (ORing management) method. And since a number of PSUs ship energy concurrently in an N+1 or N+N system, server PSUs additionally require a current-sharing method.

Even a PSU in standby mode—not delivering energy to the output from its most important energy rail—nonetheless requires prompt supply of full energy after a hot-swap occasion, thus requiring fixed activation of the ability stage. So as to cut back the ability consumption of the redundant energy provide in standby mode, “chilly redundancy” performance is turning into a development. The aim of chilly redundancy is to close down the principle energy operation or function in burst mode, enabling the redundant PSU to reduce standby energy consumption.

  1. Effectivity

Effectivity specs within the early 2000s have been simply above 65%; on the time, server PSU designers didn’t prioritize effectivity. Conventional converter topologies might simply fulfill the 65% effectivity goal. However as a result of a server must function constantly, greater effectivity can significantly cut back complete price of possession.

Since 2004, the 80 Plus normal has supplied certifications for PC and server PSU techniques that may obtain over 80% effectivity. Server PSUs in mass manufacturing in the present day largely obtain the 80 Plus Gold (>92% effectivity) requirement, and a few may even obtain 80 Plus Platinum (>94% effectivity).

Server PSUs underneath improvement in the present day primarily goal the even greater 80 Plus Titanium specs, which require over 96% peak effectivity at half hundreds. Desk 1 reveals the varied 80 Plus specs.

Desk 1 The 80 Plus specification ensures above 80% effectivity. Supply: www.clearesult.com/80plus/

Additionally, in response to the Open Compute Venture (OCP) open-rack specification that knowledge heart PSUs are following, a PSU wants to attain over 97.5% peak effectivity. Subsequently, new topologies resembling bridgeless energy issue correction (PFC) and soft-switching converters, together with large bandgap applied sciences resembling silicon carbide (SiC) and gallium nitride (GaN) may help PSUs obtain 80 Plus Titanium and open-compute effectivity objectives.

  1. Working temperature

Within the context of server PSU thermal administration, designers outline the ambient temperature on the PSU AC inlet—the place the fan is positioned—because the server PSU working temperature. The working temperature began at 45°C most within the early 2000s and in the present day reaches 55°C most, relying on the cooling system within the server room.

The next working temperature reduces the power prices of a server cooling system. In comparison with the capital expenditures of an information heart (resembling {hardware} tools), power prices as an working expense are anticipated to be greater than capital expenditures over time. Based on the ability utilization effectiveness (PUE) normal:

PUE = Whole Datacenter Energy/Precise IT Energy

As proven in Desk 2, a decrease PUE quantity means an environment friendly knowledge heart. Determine 3 is an estimation of the PUE quantity underneath completely different working temperatures. For instance, an information heart with a PUE of 1.25 can solely enable 10% of total energy consumption on its cooling system. This means the necessity for the next working temperature in a server PSU.

Desk 2 A decrease PUE quantity interprets into an environment friendly knowledge heart.

Determine 3 An estimation of the PUE quantity underneath completely different working temperatures reveals decreased cooling prices with the next working temperature.

  1. Communication and management

Communication and management have performed an necessary function in server energy through the years. Within the early 2000s, the PSU’s inner info was transmitted to the system aspect by the System Administration Bus interface. In 2007, the Energy Administration Bus (PMBus) interface added capabilities, together with configuration, management, monitoring and fault administration, enter/output present and energy, board temperatures, fan pace management, real-time replace code, overvoltage (present, temperature), and safety. Then, in response to elevated demand for knowledge heart energy cabinets, the Controller Space Community bus (CANBus) turned part of server energy communication.

Energy-management controllers have additionally advanced together with the communication bus. Within the early 2000s, analog controllers primarily managed server PSUs. As increasingly management calls for elevated the necessity for communication, it turned simpler to comprehend these calls for with digital controllers. Utilizing digital management additionally reduces a {hardware} engineer’s debugging efforts, probably decreasing labor prices throughout the PSU design and verification phases.

Future improvement tendencies for server PSUs

As server energy budgets develop whereas the quantity stays fastened, energy density necessities will change into stricter. Energy density has elevated from single digits at the start of the 2000s to just about 100 W/in3 on newly developed server PSUs. Bettering converter effectivity by topology and element expertise evolutions is the answer to reaching excessive energy density.

As was the case with the present, energy and effectivity tendencies, the perfect diode/ ORing controller must ship excessive present in a small package deal. The perfect diode/ORing controller should additionally combine options resembling monitoring, fault dealing with and transient dealing with to scale back the general element rely and PCB space wanted to attain these functionalities.

For instance, a PFC circuit in a server PSU has advanced from passive PFC to active-bridge PFC to energetic bridgeless PFC. Remoted DC/DC converters have advanced from hard-switching flyback and ahead converters to soft-switching inductor-inductor-capacitor resonant and phase-shifted full-bridge converters. Non-isolated DC/DC converters have advanced from linear regulator and magnetic amplifiers to buck converters with synchronous rectifiers. Subsequent will increase in total effectivity cut back inner energy consumption and the trouble required to resolve thermal points.

Part applied sciences utilized to server PSUs have additionally advanced, from IGBTs and silicon MOSFETs to large bandgap gadgets resembling silicon-carbide MOSFETs and gallium-nitride FETs. The nonideal switching traits of IGBTs and silicon MOSFETs restrict the switching frequencies beneath 200 kHz. Whereas large bandgap gadgets have switching traits nearer to very best switches, utilizing large bandgap gadgets can allow greater switching frequencies to assist shrink the variety of magnetic elements used within the PSU.

Because the working temperature will increase, elements in a server PSU have to deal with greater thermal stress, which additionally drives circuit evolution. For example, a standard implementation applies a mechanical relay in parallel with a resistor to suppress the enter in-rush present throughout startup. However due to their cumbersome dimension, reliability considerations and decrease temperature ranking, solid-state relays at the moment are changing mechanical relays in server PSUs.

The three.6-kW single-phase totem-pole bridgeless PFC designs with >180-W/in3 energy density and 3-kW phase-shifted full bridge with energetic clamp designs with >270-W/in3 energy density intention to satisfy frequent redundant power-supply specs in servers (Determine 4).

Determine 4 The block diagram reveals the three.6-kW and 3-kW reference designs. Supply: Texas Devices

Within the 3.6-kW PFC design, a solid-state relay accommodates a excessive working temperature. Right here, the LMG3522R030 GaN FET permits the usage of a bridgeless totem-pole PFC topology. A “child enhance” reduces the majority capacitor quantity for greater energy density.

Within the 3-kW phase-shifted full-bridge design, the LMG3522R030 GaN FET helps decrease the circulating present and makes it doable to attain delicate switching. An energetic clamping circuit performing as a lossless snubber permits greater converter effectivity with decrease synchronous rectifier voltage stresses. All of the aforementioned management necessities are achieved by C2000 microcontroller performing as digital management processor.

Richard Yin is a techniques engineer in Energy Design Providers at Texas Devices.

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