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Stephen Oliver, V•I Chip Inc. soliver@vicr , +1 978 749 3256

From the 380V DC Bus to sub-1V Processors: Efficient Power Conversion Solutions SC’07, Reno NV, 11-14-07. Stephen Oliver, V•I Chip Inc. soliver@vicr.com , +1 978 749 3256. Abstract.

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Stephen Oliver, V•I Chip Inc. soliver@vicr , +1 978 749 3256

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  1. From the 380V DC Bus to sub-1V Processors: Efficient Power Conversion SolutionsSC’07, Reno NV, 11-14-07 Stephen Oliver, V•I Chip Inc.soliver@vicr.com, +1 978 749 3256

  2. Abstract • Without a major architectural review, data centers may consume 100 Billion kWhr by 2011. i Additionally, inefficient power and cooling techniques may be the downfall of Moore’s law. ii • One efficiency improvement proposal iii is for the adoption of high voltage DC distribution to enable the AC – 384V stage to be bypassed and the downstream sub-systems (or blades) to be fed directly from the data center distribution busses. This paper represents a follow-on step and proposes high efficiency, high power density power conversion solutions from the HV bus down to processor and low-/medium- and high-power loads. • A baseline sub-system is established with a total load of 1320W: • 6x processors (1V, 120A) • 6x memory (1.5V, 50A) • Miscellaneous loads (12V, 12.5A) • Potential conversion steps considered are 380V-12V-1V and 380-48-1V with bus converter, synchronous buck converters and factorized power regulators with sine amplitude converters. • Efficiency, power density and annual electrical running cost comparisons are presented. • “Report to Congress on Server and Data Center Energy Efficiency” (p56), U.S. EPA ENERGY STAR Program, Andrew Fanara, August 2, 2007 • “The Invisible Crisis in the Data Center: The Economic meltdown of Moore’s Law”. Kenneth Brill, Uptime Institute, 2007 • “DC Power for Improved Datacenter Efficiency”, Ton (Ecos), Fortenbery (EPRI) & Tschudi (Lawrence Berkeley National Labs), January 2007.

  3. Rect., EMI& Inrush PFC Regulated HV DC-DC DC-DC‘Brick’ VRx CPU 380VDC AC 48V 12V 1.xV Backplane AC-DC ‘Silver Box’ VRx Memory 1.xV Motherboard ‘Original’ Traditional High Power System (IBA) • AC-48VDC ‘Silver Box’ + 48-12V DC-DC ‘Brick’ + VRM/VRDs to loads • As designed: • ‘High’ efficiency (~65%), ‘small’ size, ‘cost effective’ • Powered 1.5-2.5V processors, few concerns over energy costs • Over time: • AC-12VDC SMPS & VRM efficiencies / densities improved • IBA bus converters considered expensive and unnecessary • As a result, use of a 12V-only bus increased

  4. ‘Later’ Traditional High Power System (12V) • AC to 12V ‘silver box’ • 12V distribution • Synch Buck POLs to load voltages Rect., EMI& Inrush PFC Regulated HV DC-DC VRx CPU 380VDC AC 12V 1.xV AC-DC ‘Silver Box’ VRx Memory 1.xV Motherboard / Blade VRx CPU 1.xV VRx Memory 1.xV Motherboard / Blade

  5. 12V Bus Concerns • 12V bus is • Established • Proven • Multi-sourced • 12V Bus is also… • Inefficient • Distribution / connector losses • Low efficiency synch buck POLs (especially for sub-1V loads)due to duty-cycle limitations • Expensive • Large connectors, heavy bus bars, lots of copper, high electricity bills • Out of date • Only used in new systems due to incumbency and for legacy loads(e.g. 12V disk drives)

  6. Efficiency Improvements • Higher voltage bus (380VDC* and / or 48VDC) • Direct 48V-sub 1V conversion • Provide 12V for legacy / low power loads * “DC Power for Improved Datacenter Efficiency”, Ton (Ecos), Fortenbery (EPRI) & Tschudi (Lawrence Berkeley National Labs), January 2007.

  7. Revision #1: 380V to the Blade / Motherboard Rect., EMI& Inrush PFC 380VDC HV BCM VRx CPU AC 12V 1.xV • Silver Box  AC-“post-PFC” 380VDC • Reduces silver box size by >50% • 380V distribution direct to blade • Eliminates distribution loss in system(I2R loss at 380V is 0.1% of 12V loss) • Minimize connector size and cost • 380-12V conversion on the blade • Minimize 12V distribution distance AC-HVDC ‘Silver Box’ VRx Memory 1.xV Motherboard / Blade HV BCM VRx CPU 12V 1.xV VRx Memory 1.xV Motherboard / Blade

  8. HV DC-DC Conversion • Bus Converter Module (BCM) • Isolated, Unregulated • Voltage transformer / current multiplier • Sine Amplitude Converter Topology • ZVS, ZCS, >1Mhz switching frequency • 384:12V = 300W @ 95.5% • 384:48V = 330W @ 96.5% • 1.1 in2 package (>1000W / in3) • 1.28 x 0.87 x 0.26in • 0.5 oz / 15 g each U.S. and Foreign Patents and Patents Pending

  9. Revision #2: Direct 48V-to-load conversion Rect., EMI& Inrush PFC 380VDC HV BCM PRM VTM CPU AC 1.xV • Same 380V direct to blade • 380-48V conversion on the blade • 48-1.xV highest efficiency, smallest converter at the load • Minimize 12V on-blade distribution loss AC-HVDC ‘Silver Box’ 48V PRM VTM Memory 1.xV Motherboard / Blade HV BCM PRM VTM CPU 1.xV 48V PRM VTM Memory 1.xV Motherboard / Blade

  10. Direct 48V-to-Load Conversion Voltage Transformation Module (VTM) • Isolated, voltage transformer • Sine Amplitude Converter Topology • ZVS, ZCS, >1Mhz switching frequency • Performance • Up to 100A in 1.1in2 • >96% Efficient at 300W out • Input : Regulated 26-55V from PRM • Outputs : 0.8 - 55V, up to 100A (13 models) Pre-Regulator Module (PRM) • Non–isolated, regulator • ZVS Buck – Boost Topology • ZVS, >1MHz switching • Performance • 320W in 1.1in2 package • Power Density >1,100W/in3 • Efficiency = >97% at 320W out • Input : Unregulated 48V • Output : Regulated (26-55V) VTM • PRM + VTM = Isolated, regulated, voltage transformation direct to load US and Foreign Patents and Patents Pending

  11. Source Load Source Load Source Load 1uFhere 1,000uFhere Space-saving Powertrain – and no ‘Bulk’ • Direct 48V-to-load conversion with 2 V•I Chips • PRM can be located remotely • Increased space on motherboard / near load • Reduced power dissipation at load • Move POL Capacitance to input of VTM • Reduce capacitance by 1/k^2 • Additional space and cost savings

  12. Transient Response

  13. HV BCM PRM VTM 1.5V200A 380V 48V VF (48V) VTM Powertrain & Distribution Efficiency • High conversion efficiency and smallest footprint from 380V-load • Convert 380V to 1.5V, 200A • Total “380V-to-load” Efficiency = 85.2% • 96.5% x 97% x 91% • Total PCB power component footprint = 4.4 in2 ( 4 chip solution ) • With fewer caps, smaller filters, smaller heatsinks • Co-locate HV BCM & PRM, place only the VTM at the load= highest distribution efficiency (I2R) and least space taken at the load

  14. BCM VRx LowPowerLoads xV 12V Legacy, Low Power Loads Rect., EMI& Inrush PFC 380VDC HV BCM PRM VTM CPU AC 1.xV • Step down from 48V to create 12V for legacy / low power loads. • Simple unregulated DC-DC converter AC-HVDC ‘Silver Box’ 48V PRM VTM Memory 1.xV Motherboard / Blade Motherboard / Blade

  15. Systems Comparison • “System” • Blade / Motherboard Content: • 6 processors (1.0V, 120A ea.) • 6 memory (1.5V, 50A ea.) • Miscellaneous rails (12V, 150W total) • Infrastructure: • 30 blades / Motherboards • Board impedance 1.5mΩ • Rack distribution impedance 2.0mΩ • Operation: • Duty cycle = 65% • Air conditioning = 50% efficient • Electricity = $0.1028 per kWhr* • Systems: • [AC 12V] 1.xV (baseline) • [AC-384V] 12V 1.xV • [AC-384V] 48V 1.xV • [AC - 48V] 1.xV […] = silver box * Nevada industrial electricity price July ’07 ( http://www.eia.doe.gov/cneaf/electricity/epm/table5_6_a.html )

  16. Efficiency Comparison: AC-Loads • In all cases, adoption of higher voltage improves efficiency • 380V in rack and 48V on blade / motherboard has highest efficiency • +8.7% pts over baseline • Improved efficiency 380V-Load means smaller PFC / EMI section. +8.7% pts

  17. Power Loss (per Blade / Motherboard) • Reduction of 173W per blade / motherboard vs. baseline 173 W

  18. Utility Savings ( per Year per Blade / Motherboard ) • 380V in rack and 48V on blade / motherboard has highest saving ($202 per year, per blade / motherboard) $202

  19. Conclusion • 12V-only distribution systems have limitations in high power computing applications • Lower load voltages and larger load domain power • Duty cycle limitation of synchronous buck conversion • Increased I2R distribution loss • Higher voltage (380V and / or 48V) distribution greatly reduces distribution loss • Direct 48-to-load conversion offers high efficiency and small size • Enable up to 8.7% pts efficiency improvement over 12V baseline • Significant running cost savings

  20. References • “Report to Congress on Server and Data Center Energy Efficiency” (p56), U.S. EPA ENERGY STAR Program, Andrew Fanara, August 2, 2007 • “The Invisible Crisis in the Data Center: The Economic meltdown of Moore’s Law”. Kenneth Brill, Uptime Institute, 2007 • “DC Power for Improved Datacenter Efficiency”, Ton (Ecos), Fortenbery (EPRI) & Tschudi (Lawrence Berkeley National Labs), January 2007 • “Datacenter Power Delivery Architectures : Efficiency and Annual Operating Costs”, Yeaman (V.I Chip), Digital Power Forum, September 2007

  21. Thank youQuestions & comments?Visit the V•I Chip booth (#832) for a live 380V-0.8V demo

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