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Welcome

Welcome. A DC-DC converter based powering scheme for the upgrade of the CMS pixel detector TWEPP-11, Wien 28.09.2011 Arndt Schultz von Dratzig , Lutz Feld , Waclaw Karpinski , Katja Klein, Jennifer Merz , Jan Sammet , Oliver Scheibling , Michael Wlochal. Welcome. Outline.

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Welcome

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  1. Welcome A DC-DC converter based powering scheme for the upgrade of the CMS pixel detector TWEPP-11, Wien 28.09.2011 Arndt Schultz von Dratzig, Lutz Feld, WaclawKarpinski, Katja Klein, Jennifer Merz, Jan Sammet, Oliver Scheibling, Michael Wlochal Jan Sammet

  2. Welcome Outline • Introduction • Implementation into CMS • Challenges… • … and how we address them • Conclusions & Outlook Jan Sammet

  3. Welcome Upgrade of the CMS Pixel Detector • CMS pixel detector is going to be replaced during shut down of LHC in ~2016 • Additional layer of pixel modules • Number of readout chips (ROCs) increases by factor of 1.9 (16k  30k) • Present powering scheme cannot supply sufficient power through existing cables • Use DC-DC converters to reduce power losses • Aachen develops, tests and produces converters, to be used by CMS The CMS pixel detector 53 cm 93 cm Jan Sammet

  4. Welcome Strategy • Increase efficiency of power transmission • Ploss=Rcable·I2  supply power at higher voltage r·Ui.e. lower current I/r (Conversion ratio r >1) power losses Ploss=R·(I/r)2 are reduced by factor r2! Conventional powering Power supply Module Module DC-DC powering Power suppy DC-DC Module DC-DC Module Jan Sammet

  5. Welcome DC-DC Buck Converters • How it works • Frequently connect and disconnect source and load • Duty cycle D = ton/T • Conversion ratio r = Vin/Vout = 1/D (ideal converter) • Advantages • Output regulation by pulse width modulation Vout is regulated • Provide high currents with high efficiency • ASIC includestransistorsandvoltageregulationcircuit • ASIC isbeingdevelopedwithinCERN electronicsgroup (F. Faccio et al.) [see talk by S. Michelis http://indico.cern.ch/contributionDisplay.py?contribId=21&confId=120853] • Radiation toleranceofmany semi-conductortechnologiesevaluated AMIS I3T80 0.35µm(ON Semiconductor, US) - functionalupto dose of 300Mrad & fluenceof 51015 p/cm2[F. Faccio, TWEPP-10, Development of custom radiation-tolerant DCDC converter ASICs] Jan Sammet

  6. Welcome Aachen DC-DC Converter “PIX_V7“: PCB:2 copper layers a 35µm 0.3mm thick Large ground area on backside for cooling ASIC prototype: AMIS2 by CERN Iout < 3A Vin < 12V Vout configurable; (here: 2.5V & 3.3V) fs configurable, e.g. 1.3MHz Toroidal inductor: L = 450nH RDC = 40m Pi-filters at in- and output A = 28 x 16 mm2 M  2.5g 3.8% of a radiation length Shield/heat sink Design guidelines from CERN group have been implemented. Jan Sammet

  7. Welcome Challenges • Ensure radiation tolerance of high voltage (~15V) power transistors • Implement DC-DC converters into CMS • Provide magnetic field tolerance air-core inductor  risk of radiated noise • Provide good shielding and cooling • Provide high conversion efficiency • Provide compact device with small impact on material budget • Reduce and control noise emissions  (covered by CERN group) Jan Sammet

  8. Welcome Challenges • Ensure radiation tolerance of high voltage (~15V) power transistors • Implement DC-DC converters into CMS • Provide magnetic field tolerance air-core inductor  risk of radiated noise • Provide good shielding and cooling • Provide high conversion efficiency • Provide compact device with small impact on material budget • Reduce and control noise emissions  Jan Sammet

  9. Welcome Implementation into CMS • Integration for pixel barrel onto supply tube • Large distance of converters to pixel modules ( ~ 4) (goal is to be able to power detector, NOT to reduce material) • CO2 cooling available • 26 DC-DC converters per channel • Power dissipation ~ 40W per channel • Full channel (PCB, cooling pipes & bridges, 26 converters) weighs 200g and corresponds to 7% of a radiation length • 2 000 DC-DC converters required in total Pixel detector Mockup 2.2m Jan Sammet

  10. Welcome Implementation into CMS CAEN A4603 Vout = 2.5V Vin 12V 1 - 4 pixel modules per converter DC-DC ana Vana PSU  50m Vout = 3.3V 6 - 7 converters 1 - 4 pixel modules per converter DC-DC dig Vdig PSU 6 - 7 converters • Two CAEN power supply units (PSU) per supply tube channel • Power suppliesneedmodification • I < 2.8A per converter (for L = 2 x 1034 cm-2 s-1) Jan Sammet

  11. Welcome Challenges • Ensure radiation tolerance of high voltage (~15V) power transistors • Implement DC-DC converters into CMS • Provide magnetic field tolerance air-core inductor  risk of radiated noise • Provide good shielding and cooling • Provide high conversion efficiency • Provide compact device with small impact on material budget • Reduce and control noise emissions   Jan Sammet

  12. Welcome Challenges • Ensure radiation tolerance of high voltage (~15V) power transistors • Implement DC-DC converters into CMS • Provide magnetic field tolerance air-core inductor  risk of radiated noise • Provide good shielding and cooling • Provide high conversion efficiency • Provide compact device with small impact on material budget • Reduce and control noise emissions   Jan Sammet

  13. Welcome R&D on Shielding • Electrical shielding: • Acts also as cooling contact for coil • Shape optimized to fit into edge channels of supply tube • Several technologies are under investigation: • Hydroformed/deep drawn aluminium • Ruled out; required shape not feasible in mass production • Plastic shields coated with a metal layer • Different materials, thicknesses and depositing techniques have been tested • Milled Aluminium shields • 120µm of Aluminium etched down to 90µm + 15 µm of Nickel + 15 µm of Copper Jan Sammet

  14. Welcome Effectiveness of Shielding • Measure z-component of magnetic field of DC-DC converter • Automated x-y table allows high spatial resolution • Many different materials and thickness have been tested focus on thinnest and lightest functional shieldings here BZ Scanning table Jan Sammet

  15. Welcome Effectiveness of Shielding • 90µm milled Aluminium • Magnetic field reduced to 15% • Price per piece ~ 25 € • Plastic shield coated with 30 µm Cu • Magnetic field reduced to 30% • Price per piece: ~ 13 € • Plastic shield coated with 60 µm Cu • Magnetic field reduced to 5% • Price per piece: ~ 13 € • Roughly 56% higher contribution to MB 60µm Cu 90µm AL No shield 30µm Cu Jan Sammet

  16. Welcome Thermal FE-Simulation • Cooling bridges clamp around CO2 pipes • Chip cooled through PCB backside • Shield (soldered to PCB) acts as cooling contact for inductor -6 °C Shielding simulated, but not displayed -10 -15 • Temperature of cooling bridge T = -20°C • Chips are at -7°C (T = 13K) • Coils are at -6°C ( T = 14K) • For room temperature (20°C) operation, both stay below 40°C -20 Jan Sammet

  17. Welcome Thermal Measurements PIX_V7, 450nH, 1.3MHz Vin = 10V, Vout = 3.3V Coil temperature [°C] Output current [A] • Converter on cooling bridge at 20°C • Good agreement with Finite Element simulations • Shielding fulfils task of cooling contact for coil • Cooling of chips via backside of PCB is very effective Jan Sammet

  18. Welcome Challenges • Ensure radiation tolerance of high voltage (~15V) power transistors • Implement DC-DC converters into CMS • Provide magnetic field tolerance air-core inductor  risk of radiated noise • Provide good shielding and cooling • Provide high conversion efficiency • Provide compact device with small impact on material budget • Reduce and control noise emissions     Jan Sammet

  19. Welcome Challenges • Ensure radiation tolerance of high voltage (~15V) power transistors • Implement DC-DC converters into CMS • Provide magnetic field tolerance air-core inductor  risk of radiated noise • Provide good shielding and cooling • Provide high conversion efficiency • Provide compact device with small impact on material budget • Reduce and control noise emissions     Jan Sammet

  20. Welcome Efficiency PIX_V7, Vout = 3.3V PIX_V7, Vout = 2.5V Efficiency [%] Efficiency [%] [White regions: regulation not working properly, Vout too low] • Phase 1 conditions: Vout = 3.3V or 2.5V, Iout < 2.8A, conversion ratio of 3-4 75% - 80%efficiency: ok – still expected to increase further with new version of AMIS chip Jan Sammet

  21. Welcome Choice of Inductor • Optimal coil shape has been calculated for different wire types and thicknesses • In the available space, copper offers higher efficiency • For pixel upgrade, favour efficiency over material budget (due to high ) Jan Sammet

  22. Welcome Challenges • Ensure radiation tolerance of high voltage (~15V) power transistors • Implement DC-DC converters into CMS • Provide magnetic field tolerance air-core inductor  risk of radiated noise • Provide good shielding and cooling • Provide high conversion efficiency • Provide compact device with small impact on material budget • Reduce and control noise emissions       Jan Sammet

  23. Welcome Challenges • Ensure radiation tolerance of high voltage (~15V) power transistors • Implement DC-DC converters into CMS • Provide magnetic field tolerance air-core inductor  risk of radiated noise • Provide good shielding and cooling • Provide high conversion efficiency • Provide compact device with small impact on material budget • Reduce and control noise emissions       Jan Sammet

  24. Welcome Conductive Noise Noise through cables (conductive noise) was studied with EMC set-up EMC = electromagnetic compatibility GND Load LISN = Line ImpedanceStabilization Network SpectrumAnalyzer Differential Mode (DM), “ripple“ Common Mode (CM) Jan Sammet

  25. Welcome Conductive Noise Differential Mode, no shield Common Mode, no shield PIX_V7 output noise Vout = 3.3V Vin = 10V fs = 1.3MHz L = 450nH Differential Mode, with shield Common Mode, with shield  Large reduction of CM above 2 MHz due to shield Jan Sammet

  26. Welcome System Tests with CMS Pixel Modules • System tests with original pixel PSU from CAEN and module qualification set-up • One full module (16 ROCs, each containing 4160 pixels) is read out • S-curve noise of each pixel is measured • Many thanks to PSI for hardware and advice Connector board PC interface„Advanced Test Board“ Moduleadapter DAQ PC CAEN Pixel PSU Module SY1527 + Branch Controller EASY 4000 PSM A4603 DC-DCconverters HV (150V) VA VD Pixel module multi-servicecables (40m) Original pixel powersupply unit DC-DC converter on bus board Jan Sammet

  27. Welcome Powering with DC-DC Converters conventional powering powering with DCDC • DC-DC converters cause no significant increase of noise Jan Sammet

  28. Welcome Impact of Orbit Gaps • Orbit gaps of LHC beam  no collisions for 3µs every 89µs • Pixel digital current drops within 25..100ns (1..4 bunches, depending on the occupancy) • Worst case for 2×1034cm-2s-1: • ID_high = ~ 2.7A (86µs) ID_low = ~1A (3µs) • Stability Test of the whole power supply chain: • Also check impact of “inverted orbit gaps” • ID_high = ~ 2.7A (3µs) ID_low = ~1A (86µs)(LHC fill with only a few intense bunches) ID t CAEN Pixel PS Moduleadapter Connector board PC interface„Advanced Test Board“ DAQ PC Module Dynamic Load Box SY1527 + Branch Controller EASY 4000 PSM A4603 DC-DCconverters HV (150V) VA VD multi-servicecables (40m) ID t Jan Sammet

  29. Welcome Impact of Orbit Gaps Conventional powering • Powering with DC-DC converters • Without DC-DC converters •  Load variations cause moderate increase of noise • With DC-DC converters • Sensitivity is reduced due to filtering components and regulation of DC-DC converter Jan Sammet

  30. Welcome Influence of the Switching Frequency • Slight reduction ( < 1e ) at 2 MHz • Not significant yet • Might become relevant in larger system • Not directly comparable to previous measurements  •  (slightly different cabling, no copper plate here) Jan Sammet

  31. Welcome Different Sensing Points • DC-DC converter is seen by PS as negative impedance • Sensing at converter could cause instabilities • Modifications of PS would be more complex and costly • Measure influence of sensing point in system tests Dynamic Load Sensing at DC-DC converter DC-DCconverter CAEN PS Module multi-servicecables (40m) Sensing at PS Powering with DC-DC converters • No increase of noise due to sensing at PS • Sensing at DC-DC converters not necessary Jan Sammet

  32. Welcome Challenges • Ensure radiation tolerance of high voltage (~15V) power transistors • Implement DC-DC converters into CMS • Provide magnetic field tolerance air-core inductor  risk of radiated noise • Provide good shielding and cooling • Provide high conversion efficiency • Provide compact device with small impact on material budget • Reduce and control noise emissions        Jan Sammet

  33. Welcome Conclusions & Outlook • Conclusions • Good progress has been made towards a DC-DC converter based powering scheme • Plans for implementation are far advanced • Efficiency and noise performance of our DC-DC converters are satisfactory • Outlook • Improve system tests with more modules, cold temperatures… • Perform thermal cycling to simulate accelerated aging and to ensure reliable operation in the long term • Implement new versions of the AMIS chip (AMIS4 expected soon) • Implement control scheme for DC-DC converters Jan Sammet

  34. Welcome Back-Up Slides Jan Sammet

  35. Welcome The CMS Pixel Detector • Pixel size: (100 x 150) µm² • Present barrel New barrel Jan Sammet

  36. Welcome Aachen DC-DC Converter Design guidelines from CERN group have been followed. Jan Sammet

  37. Welcome Mechanical & Thermal Integration cooling pipes lower part of cooling bridge upper part of cooling bridge chip area • Cooling bridge clamps around pipe • Area reduced to reduce material • Aluminium (could be Graphite, but gain for material budget is low) Jan Sammet

  38. Welcome Effectiveness of Shielding Jan Sammet

  39. Welcome Conductive Noise with Shielding Jan Sammet

  40. Welcome Set-Up for System Tests DC-DC converters Pixel module Original pixel powersupply system Jan Sammet

  41. Welcome Powering with DC-DC Converters 2 • VD = 3.2V, VA= 2.5V • VD = 3.2V, VA= 2.5V • Variations with different but identical converters ~2e • Reproducibility of measurements ~1e Jan Sammet

  42. Welcome Influence of the Switching Frequency No additional load Additional 2A const. Load • (VD = 3.2V, VA= 2.5V) • (VD = 3.2V, VA= 2.5V) With simulated orbit gaps With inverted orbit gaps • (VD = 3.2V, VA= 2.5V) • (VD = 3.2V, VA= 2.5V) Jan Sammet

  43. Welcome Different sensing points, w/o Add. Load Sensing at DC-DC DC-DCconverters CAEN PS multi-servicecables (40m) Module • µ-twisted pair cables Sensing at PS Powering with DC-DC converters • (VD = 3.2V, VA= 2.5V) • DC-DC converter is seen by PS as negative impedance • Sensing at converter could cause instabilities • Modifications of PS would be complex and costly • Test influence of sensing point in system tests •  No increase of noise due to sensing at PS Jan Sammet

  44. Welcome Different sensing points, w/o Add. Load Sensing at DC-DC/load (with and w/o voltage divider) DC-DCconverters CAEN PS multi-servicecables (40m) Sensing at PS(with voltage divider) Module • µ-twisted pair cables Conventional powering Powering with DC-DC converters • (VD = 3.5V, VA= 2.7V) • (VD = 3.2V, VA= 2.5V) • No increase of noise due to sensing at PS  No increase of noise due to sensing at PS Jan Sammet

  45. Welcome Different sensing points with Orbit Gaps Dynamic Load Box Sensing at DC-DC/load DC-DCconverters CAEN PS multi-servicecables (40m) Module • µ-twisted pair cables Sensing at PS Powering with DC-DC converters • (VD = 3.2V, VA= 2.5V) • Test influence of sensing point in system tests • No increase of noise due to sensing at PS • Simplifies modifications of PS by CAEN Jan Sammet

  46. Welcome Different sensing points with Orbit Gaps Dynamic Load Box Sensing at DC-DC/load (with and w/o voltage divider) DC-DCconverters CAEN PS multi-servicecables (40m) Sensing at PS(with voltage divider) Module Conventional powering Powering with DC-DC converters • (VD = 3.5V, VA= 2.7V) • (VD = 3.2V, VA= 2.5V) • Noise increases if voltages are senses at PS  No increase of noise due to sensing at PS Jan Sammet

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