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October 2, 2013 11:28 WSPC - Proceedings Trim Size: 9in x 6in Final˙Paper
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POWER SUPPLY SYSTEM FOR THE ATLAS
EXPERIMENT: DESIGN SPECIFICATIONS,
IMPLEMENTATION, TEST AND FIRST RESULTS∗
M. LAZZARONI∗∗
Dipartimento di Fisica, Universita degli Studi di Milano
Via Celoria, 16 - 20133 Milan, Italy
andI.N.F.N. Milano,
Via Celoria, 16 - 20133 Milan, Italy∗∗E-mail: [email protected]
www.unimi.it
M. CITTERIO and S. LATORRE
I.N.F.N. Milano,
Via Celoria, 16 - 20133 Milan, Italy
A. LANZA
I.N.F.N. Pavia,
Via Bassi, 6 - 27100 Pavia, Italy
P. COVA and N. DELMONTE
Dipartimento di Ingegneria Informazione, University of Parma
Viale G.P. Usberti 181/A - 43124 Parma, Italyand
I.N.F.N. Pavia,Via Bassi, 6 - 27100 Pavia, Italy
F. GIULIANI
Dipartimento di Ingegneria Informazione, University of ParmaViale G.P. Usberti 181/A - 43124 Parma, Italy
The planned upgrade of instrumentation sensitivity in the ATLAS experiment
of the Large Hadron Collider (LHC), at CERN, calls for a new type of power
distribution architecture. Moreover, power supplies require DC-DC power con-
∗This work is supported by I.N.F.N. Italy Apollo collaboration.
October 2, 2013 11:28 WSPC - Proceedings Trim Size: 9in x 6in Final˙Paper
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verters able to work in very hostile environment and maintaining high level ofReliability, Availability, Maintainability and Safety (denoted as RAMS require-
ments) during the experimental activity. Two main issues need to be discussed:
first, electronic devices and equipment must operate in very high backgroundof both charged and neutral particles and high static magnetic field and, sec-
ond, the increase of the radiation background and the requirements of new
front-end electronics are indeed incompatible with the current capability ofthe actual distribution system. The APOLLO R&D collaboration, funded by
the Italian Istituto Nazionale di Fisica Nucleare (INFN), aims to study dedi-
cated topologies of both distribution system and DC-DC power converters andto design, build and test demonstrators, developing the needed technology for
the industrialization phase. The collaboration has designed a 3kW, 280V-12V
converter (MC) based on the Switch in Line architecture (SIL), a DC to DCphase-shifted converter characterized by a disposition in line of the MOSFETs
with good soft switching performances, and in the last year many steps have
been taken to enhance the power dissipation and the reliability and to im-prove the general features of the designed converter. In particular a new water
heat sink was designed on the basis of TFD simulation accounting for the lay-out of the specific converter. Experimental activities in order to characterize
both thermal and electrical features of the MC confirm the correctness of the
adopted design criteria.
Keywords: Power Supply; Power Converter; Reliability; LHC.
1. Introduction
The Large Hadron Collider (LHC) is, nowadays, the world’s largest and
highest-energy particle operative accelerator, built by the European Or-
ganization for Nuclear Research (CERN) able to extends the frontiers of
particle physics thanks to its high energy and luminosity. The Phase-2 up-
grade of the LHC is planned to take place during the long shutdown of the
year 2022 when the detectors will be upgraded or substituted. An increase
of the radiation background will cause the accumulation of a higher Total
Ionizing Dose (TID). Furthermore a significant increase of power demand of
the detectors implies a complete re-design of the power distribution system,
water cooling and very stringent thermal constraints1 in order to maximize
both performances and RAMS requirements.2,3
2. The Main Converter
The Main Converter is based on a Switch in Line Converter (SIL) topol-
ogy where the circuit consists in a series connected half bridge converter as
described in previous papers.4,5 The first, of three in 2oo3 redundancy con-
figuration, implemented prototype able to deliver 1.5 kW i.e. 125 A at 12 V
is depicted in Fig. 1 (parallel connection is possible because SILC topology
acts like a controlled current generator).
October 2, 2013 11:28 WSPC - Proceedings Trim Size: 9in x 6in Final˙Paper
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Fig. 1. MainConverter Fig. 2. Cold Plate
In order to improve the performance and the reliability of the con-
verter in the last year the prototype has been deeply modify: the planar
transformer PCBs has been replaced with copper windings separated with
Kapton sheets, a specific cold plate has been designed, simulated, tested
and manufactured (Fig. 2), the thermal coupling between the transformer
and the cold plate has been re-designed and improved, the connections to
the external power cables have been improved and, finally, the auxiliary
power supply and the controller have been replaced. In particular, the cold
plate has been desinged taking into account the necessity of dissipation in
proximity of single devices in such a way to have a power dissipation that
Table 1. Module devices: description and dissi-
pated power (output power: 1.2 kW).
N Device Pd
(W)
1 Planar transformer - core 130
2 Planar transformer - windings 70
3 Diodes (ISOTOP) 104 Primary - MOSFETs (TO247) 18
5 Primary - inductor core 4
6 Primary - inductor windings 37 Auxiliary - MOSFET (TO247) 0.2
8 Auxiliary - MOSFET (D2PAK) 0.2
9 Auxiliary - transformer core 0.510 Auxiliary - transformer windings 0.5
11 Capacitors and other devices 4.512 Copper traces at secondary 5.5
Total power dissipation 246.4
October 2, 2013 11:28 WSPC - Proceedings Trim Size: 9in x 6in Final˙Paper
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Fig. 3. The utilized evaluation board. Fig. 4. The tested demo-board.
fit locally with the installed component (Table 1). The test results have led
to the adoption of a sink to a 2C shaped cold plate where the maximum
experimentally measured temperatures at 1.5 kW of delivered power was
108 C.
3. Magnetic field test of a commercial DC-DC converter
An integrated DC-DC step-down converter by Linear Technologies
(LTM4619) has been tested in order to check its magnetic field tolerance.
Test have been carried out at the LASA, a center for research and devel-
opment in the fields of accelerators and of superconductivity of University
of Milan and INFN. The tested evaluation board is shown in the follow-
ing Fig. 3. The tests have been carried out changing the position of the
evaluation board in order to apply the magnetic field in different directions
(Fig. 3). The experimental setup is depicted in Fig. 4.
The two outputs of the evaluation board are both configured to provide
an output voltage of 1.8 V on a nominal load of 0.6 Ω. The current supplied
is therefore equal to 3 A per output, 5.4 W. The board power input was
supplied at 20 V.
It was also added a heat sink which enabled to maintain the module at
approximately 35 C. This allows the device to work as much as possible at
the conditions of nominal efficiency. The tests have been carried out with
the applied magnetic field in three directions.
The best performance was obtained with the magnetic field orthogonal
to the device plane, up to about 0.4 T. The worst performance was observed
with the magnetic field parallel to the device and with direction right to
left, as depicted in Fig. 5.
October 2, 2013 11:28 WSPC - Proceedings Trim Size: 9in x 6in Final˙Paper
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Fig. 5. Experimental results.
4. Conclusions
The designed prototype has proved capable of providing the performance
required by the design specifications. Further tests will be conducted with
the aim to verify both the radiation and magnetic field effects. Some results
on a commercial POL which showed a good behavior until 0.2− 0.4 T have
been also presented.
References
1. P. Tenti, G. Spiazzi, S. Buso, M. Riva, P. Maranesi, F. Belloni, P. Cova,R. Menozzi, N. Delmonte, M. Bernardoni, F. Iannuzzo, G. Busatto, A. Porzio,F. Velardi, A. Lanza, M. Citterio and C. Meroni, Journ. of Instrumentation6 (2011).
2. M. Lazzaroni, L. Cristaldi, L. Peretto, P. Rinaldi and M. Catelani, Reliabilityengineering: basic concepts and applications in ICT (ISBN 978-3-642-20982-6,e-ISBN 978-3-642-20983-3, DOI: 10.1007/978-3-642-20983-3, Springer, BerlinHeidelberg, 2011).
3. P. Cova, N. Delmonte, F. Giuliani, M. Citterio, S. Latorre, A. Lanza andM. Lazzaroni, Thermal modeling and characterization of power converters forlhc power supplies, in Proc. of 12th IMEKO TC10, Workshop on TechnicalDiagnostics, 202–207 , (Florence, Italy, june, 2013).
4. M. Alderighi, M. Citterio, S. Latorre, M. Riva, P. Cova, N. Delmonte,A. Lanza, M. Bernardoni, R. Menozzi, A. Costabeber, A. Paccagnella, F. Sichi-rollo, G. Spiazzi, M. Stellini, P. Tenti, S. Baccaro, F. Iannuzzo, A. Sanseverino,G. Busatto and V. D. Luca, Power distribution architecture for high energyphysic hostile environment, in Proc. of 13th ICATPP Conference, 890–894 ,(Villa Olmo, Como, Italy, october, 2011).
5. M. Alderighi, M. Citterio, M. Riva, S. Latorre, A. Costabeber, A. Paccagnella,F. Sichirollo, G. Spiazzi, M. Stellini, P. Tenti, P. Cova, N. Delmonte,A. Lanza, M. Bernardoni, R. Menozzi, S. Baccaro, F. Iannuzzo, A. Sansev-erino, G. Busatto, V. D. Luca and F. Velardi, Journ. of Instrumentation 7(2012).