Optimization of DC-DC Converters for Improved Electromagnetic Compatibility With High Energy Physics Front-End Electronics

Abstract

Abstract-The upgrade of the Large Hadron Collider (LHC) experiments at CERN sets new challenges for the powering of the detectors. One of the powering schemes under study is based on DC-DC buck converters mounted on the front-end modules. The hard environmental conditions impose strict restrictions to the converters in terms of low volume, radiation and magnetic field tolerance. Furthermore, the noise emission of the switching converters must not affect the performance of the powered systems. A study of the sources and paths of noise of a synchronous buck converter has been made for identifying the critical parameters to reduce their emissions. As proof of principle, a converter was designed following the PCB layout considerations proposed and then used for powering a silicon strip module prototype for the ATLAS upgrade, in order to evaluate their compatibility.

The International Linear Collider Technical Design Report - Volume 4: Detectors

“…Test boards were constructed operating at 1 MHz with several di erent commercial DC-DC converter chips. Tests with ATLAS tracker silicon strip detectors [79,80] indicated that the electrical noise is primarily electrostatic and can be shielded by a 20 µm Al foil. To further reduce the mass, higher frequency operation of the inductor and the buck converter is required.…”

Power-pulsing schemes for vertex detectors at CLIC

“…The storage capacitors have to be charged back to their initial voltage before the next bunch train arrives. This was previously meant to be achieved using a DCDC buck converter [5] outside the vertex barrel region, connected through a 30 cm flex cable to the front-end electronics. In the following we present an improved powering scheme where the DCDC buck converters are replaced by programmable current sources.…”

Power pulsing schemes for vertex detectors at CLIC

“…Local regulation is necessary in order to accomplish the required regulation while supplying more than 20 A along the 12 cm of half a ladder. The proposed scheme (figure 5 and consists of a buck DC-DC converter [4] placed outside the vertex barrel region, connected through aluminium flex cables to a local regulation based on Low-DropOut regulators (LDOs) and silicon capacitors [5]. The latter are fundamental for material mass reduction as the radiation length of silicon is high and as future improvements to the technology are expected to increase their capacitance density by a factor of 4 (from 250 nF/mm 2 to 1 µF/mm 2 ) [5], making the X 0 /unit capacitance for silicon significantly smaller than for other commercially available capacitor materials.…”