Speakers
Description
Summary
LVBOX
The power supply, called LVBOX, is mounted in the vicinity of Tile Calorimeter
detector modules (drawers) inside so called FINGERS [1]. Each LVBOX contains
eight independent DC/DC converters - bricks (3.3VDIG, +5VMB, -5VMB, +5VDIG,
+15VMB, +5VHV, +15VHV, and -15VHV), so called ELMB Motherboard, ELMB plug-
in board [2], 200VDC distribution Fuse-Board, internal cable set, and chassis
and water cooled heatsink. The ELMB Motherboard and ELMB module are
connected to DC/DC converters and permit remote PC monitoring of their
behavioral parameters (temperatures, Iin, Iout, Vin, Vout, DIG and MB side
sense line voltages) and set trimming of Vout. Start-up sequence of LVBOX is
carried out in 3 groups of bricks[5]. HV or DIG side brick group shutdowns are
triggered by most critical power lines: -5VMB, +15VMB, and -15VHV. The LVBOX
is exposed to radiation and magnetic field in the ATLAS cavern. The Tile LVPS
system is computer managed by the Detector Control System (DCS) software
through a CAN Bus line that communicates with the local ELMB of each power
supply. The LVBOX of each Tile detector module has to deliver average power of
300W. Production of final 256 units started at CERN in January 2007.
DC/DC SWITCHING POWER SUPPLY MODULE - "BRICK"
The key component of the LVBOX is a small size (80 x 80 x 30mm), radiation and
magnetic field tolerant, single output DC/DC dual transistor synchronous
forward converter based on LT1681 chip[6]. Full custom design using only COTS
(Commercial Off The Shelf) components and the universal printed circuit board
design enabled to select three brick versions of various outputs (+3.3V, +5V, or
15V) by means of only several components change. Brick input voltage is
+200VDC due to the radiation derating. The maximum output power from the
brick is 150W. The DC/DC converter design enables high efficiency of energy
conversion: 72% for 3.3V @10A Iout, 85% for 5V version @10A, and 82 % for
15V version @6A, respectively[3]. Switcher uses the current mode control and
has fixed switching frequency of 300kHz. The brick frequency can be
synchronized with other DC/DC modules inside LVBOX. In order to start, the
brick needs a remote auxiliary Start-Up voltage of +15V coming from the AUX
Board in USA15 control room. Important brick features are active Overcurrent
and Overvoltage protection circuitry[5]. Innovative technology of brick cooling
(especially of the switching FET power transistors, power inductors and high
frequency transformer) was applied by means of custom made Al2O3 ceramic
spacers. 2048 bricks plus spares are needed for the LVBOX production.
Brick has integrated remote control and measurement circuitry for both input
(Iin/Vin) and output (Iout/Vout) parameters. Moreover, three temperature
sensors are also present to control brick cooling. The Vout voltage can be
trimmed in range of 15%. This feature enables a remote correction of Vout
voltage during radiation degradation of output voltage of LVPS. The trimming,
sensing and remote control of the brick are carried out by the ELMB module [2].
Extensive irradiation test campaigns of COTS components and of the brick
prototype were performed at PSI, Villigen, CH (protons 2002, 2003, 2004), at
CERN (neutron P2B 2004, TCC2 SPS tunnel 2002, 2003 campaigns), Saclay
(Co60 gamma test 2003) and at INT Portugal NIEL tests in 2003[3].
Experimental results demonstrated that bricks and ELMB motherboards could
work together without problems up to 20krad TID, and survive up to 2.15E+12
n/cm^2 neutron fluency. Bricks radiation tolerance is even higher reaching 35-
38krads. Bricks are also designed to be operational in external DC magnetic
field without damage. Magnetic field decreases efficiency caused by DC
magnetization of the HF transformer ferrite core. Decrease of the DC/DC
converter efficiency measured at CERN magnet with external B at 200 Gauss
(TILECAL nominal level) was max -1.5%, and at 500 Gauss was -3%.
200VDC BULK POWER SUPPLIES
The input for the Tile power system is 200V DC voltage that is converted from
three phase mains 3x230V~. For this purpose 22 custom made bulk power
supplies HPS1 are needed. One HPS1 unit contains three 1.7kW power
channels delivering 200VDC/8.5A [4], and can power 12 LVBOX power supplies.
HPS1 are not radiation tolerant and therefore are deployed in USA15 control
room of the ATLAS cavern. They were developed at TESLA Company, Prague, CZ.
AUX BOARD
The Auxiliary (AUX) Board is 6U sized pcb board and generates all auxiliary
signals and power voltages for one cluster of 4 LVBOXes. The board consists of
3 x 4 isolated power supplies for the ELMB motherboard (trimmed between 6.8 -
14.5V), for ELMB chip (6.8 - 14.5V) and Start-up signal (15 - 25V) for LVPS
bricks. It also contains current sources for LVBOX HV/DIG side remote on/off
current loop controls and an interlock circuitry. The board is controlled via ELMB
module hosting custom made version of ELMB software. So all AUX boards are
creating another CAN bus network and theirs control is embedded into the
overall remote control system. The distance between 64 AUX Boards or 22 HPS1
supplies in USA15 room and 256 LVBOXes in the ATLAS cavern varies from 60 to
100 meters depending on the position of particular power supply.
LVPS INTERLOCK BOARD
The LVPS interlock board receives ATLAS DSS cooling interlock signals. In case of
interrupted water cooling to the Tile Calorimeter, one LVPS Interlock Board will
disable functioning of 64 LVBOXes. It is hardwired together with 16 channels of
200VDC HPS1 bulk power supplies and 16 AUX Boards.
REFERENCES
[1] "Design of the front-end analog electronics for the ATLAS tile calorimeter", K.
Anderson et al., Nucl. Instr. and Meth. A, Vol. 551 (2005), pp. 469-476.
[2] "The Embedded Local Monitor Board (ELMB) in the LHC Front-end I/O Control
System", B. Hallgren, 7th Workshop on Electronics for LHC Experiments,
LECC2001.
[3] Production Readiness Review of LVPS design, LVPS Meeting,
CERN/ATLAS/TileCal, 10 Dec 2004.
[4] "High power supply HPS1 Operational Manual", TESLA Hloubetin, Prague,
CZ, technical manual, 2005.
[5] "Specifications for the Modification of the ATLAS TileCal Bricks for Low
Voltage Power Supplies", B.Palan, L. Price, G. Drake ,CERN ATLAS Draft report,
Dec 29, 2006.
[6] "Radiation and magnetic field tolerant 150W DC/DC converter brick",
I.Hruska, CERN-ATLAS-TileCal internal technical datasheet, 2006
