System Integration Issues of DC to DC converters in the sLHC Trackers
System Integration Issues of DC to DC converters in the sLHC Trackers
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sLHC 跟踪器中 DC-DC 转换器的系统集成问题
DOI：
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发表时间：
2009
期刊：
影响因子：
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通讯作者：
C. Fuentes
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文献类型：
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作者：
B. Allongue;S. Michelisa;G. Blanchot;F. Faccio;S. Orlandia;C. Fuentes
sLHC实验中跟踪器的升级需要实施新的供电方案，以提供更高的功率密度，减少损耗和材料预算。提出了一种基于降压和开关电容DC-DC变换器的方案作为最佳解决方案。降压转换器基于功率ASIC，连接到定制的空芯电感器。功率模块的部件布置和电路板布局旨在最大限度地减少紧凑体积中的EMI辐射，从而实现其在跟踪器模块和板条上的集成。I.如今，LHC的高能物理实验嵌入了大型且非常敏感的前端电子系统，这些系统通常通过长电缆远程供电。实验的最里面的区域，跟踪器，是那些提供最大密度的通道，必须用最小质量的电缆供电，并减少散热，以避免复杂和庞大的冷却系统。随着加速器的升级及其物理实验已经在计划中，探测器将需要更多的电子读出通道，这将需要更多的功率。由于缺乏物理空间来运行更多的电缆，并且由于该体积中的材料对检测器的物理性能有害，因此应该在不增加检测器体积中的材料的情况下实现输送功率的这种增加。在不增加电缆体积和质量的情况下提供更多功率的解决方案依赖于通过检测器上DC-DC转换器分配功率。这些转换器必须能够在探测器的高辐射（总电离剂量为250 Mrad（SiO2），中子注量为2.5× 1015 n/cm 2，1 MeV中子当量，基于中心跟踪探测器在其预计寿命期间的模拟环境）和强直流磁场环境（高达4 T）中可靠运行。为了与这种恶劣的环境兼容，电子设备需要采用特定的技术进行设计，这些技术必须符合所需的剂量和通量。与所需的高度小型化一起，这一事实迫使开发定制ASIC，用于在已知的辐射合格技术中实现功率控制器和开关[1]。大型强子对撞机跟踪器在高达4 T的磁场下工作，使粒子弯曲，从而使它们得以识别。DC-DC转换器将暴露于该DC磁场。这禁止使用传统的铁磁芯，因为它们在磁通密度低于3 T时饱和。必须使用无芯（空心）电感器，将电感值限制在700 nH以下，以保持可承受的尺寸和质量[2]。比较研究表明，降压转换器是最适合预期应用的转换器拓扑结构之一[3]。考虑到可用的无芯电感的范围，开关频率必须设置为超过1 MHz，以限制电流涟漪。一个典型的跟踪器前端系统是由带状探测器，结合到前端混合电路。这些混合动力车配备了几个前端芯片。然后将几个混合和探测器模块安装在一起以形成板条[4]。基于这一点以及混合动力车的估计功率要求，已经定义了基于DC-DC转换器（图1）的最佳供电方案[3]，该方案依赖于沿着冷却壁分布到所有混合动力车的输入电压总线（10 V）。每个混合电路将配备一个降压DC/DC转换器，提供一个中间总线电压（2.5V），为每个前端芯片供电，转换效率为80%。然后，每个前端芯片将通过集成开关电容负载点DC/DC转换器将中间电压转换到所需的水平（1.2V和0.9V），其效率预计约为95%。除了为这种供电方案设置的环境限制之外，跟踪器电子设备和用于为其供电的DC-DC转换器之间的电磁兼容性至关重要。由前端电子设备附近的DC/DC转换器供电的sLHC跟踪器必须能够实现与在本系统中使用远程调节电源时获得的性能水平相当的性能水平。开关转换器与带和前端ASIC（小于5 cm）的接近程度使前端电子器件暴露于传导和辐射耦合，这可能会损害跟踪器性能。兼容性可以通过转换器的适当设计来实现，图1：供电拓扑。
The upgrade of the trackers at the sLHC experiments requires implementing new powering schemes that will provide an increased power density with reduced losses and material budget. A scheme based on buck and switched capacitors DC to DC converters has been proposed as an optimal solution. The buck converter is based on a power ASIC, connected to a custom made air core inductor. The arrangement of the parts and the board layout of the power module are designed to minimize the emissions of EMI in a compact volume, enabling its integration on the tracker modules and staves. I. POWERING TRACKERS AT THE SLHC Today’s high energy physics experiments at LHC embed large and very sensitive front-end electronics systems that are usually remotely powered through long cables. The innermost region of the experiments, the trackers, are those providing the largest density of channels, that must be powered with the minimal mass of cables and with reduced heat dissipation to avoid complex and massive cooling systems. With the upgrade of the accelerator and its physics experiments already being planned, the detectors will require an increased number of electronic readout channels, which will demand more power. This increase of delivered power should be achieved without the addition of material in the detector volume, because of lack of physical space to run more cables and because material in this volume is detrimental to the physics performance of the detector. A solution to deliver more power without increasing the cable volume and mass relies on the distribution of power through on-detector DC–DC converters. These converters must be capable of reliable operation in high radiation (total ionizing dose of 250 Mrad(SiO2) and neutron fluencies of 2.5×10 15 n/cm 2 , 1 MeV neutron equivalent, based on the simulated environment in the central tracker detector over its projected lifetime) and strong DC magnetic field environment (up to 4 T) of the detector. To be compatible with this harsh environment, the electronic devices need to be designed in specific technologies that have been qualified for the required doses and fluencies. Together with the high degree of miniaturization required, this fact imposes the development of a custom ASIC for the implementation of the power controller and switches in a known, radiation qualified technology [1]. The LHC tracker operates with magnetic fields up to 4 T to bend the particles thus allowing their identification. The DC-DC converters will be exposed to this DC magnetic field. This forbids the use of conventional ferromagnetic cores, since they saturate at flux densities below 3 T. Coreless (aircore) inductors have to be used instead, limiting the accessible values of inductance below 700 nH in order to maintain affordable size and mass [2]. A comparative study indicated that the buck converter is one of the most suitable converter topology for the intended application [3]. Given the range of available coreless inductors, the switching frequency has to be set beyond 1 MHz in order to limit the current ripple. A typical tracker front-end system is made of strip detectors that are bonded to front-end hybrid circuits. These hybrids are fitted with several front-end chips. Several hybrid and detector modules are then mounted together to form a stave [4]. Based on this and on the estimated power requirements of the hybrids, an optimal powering scheme based on DC-DC converters (Figure 1) has been defined [3], that relies on an input voltage bus (10V) distributed along the stave to all the hybrids. Each hybrid circuit would be equipped with one Buck DC/DC converter delivering an intermediate bus voltage (2.5V) that brings the power to each front-end chip with a conversion efficiency of 80%. Each front-end chip would then convert the intermediate voltage down to the levels that it requires (1.2V and 0.9V) through integrated switched capacitors point-of-load DC/DC converters, whose efficiency is expected to be around 95%. Beyond the environmental constrains that are set to this powering scheme, the electromagnetic compatibility between the tracker electronics and the DC-DC converter used to power it is essential. The sLHC tracker powered from DC/DC converters in close proximity of the front-end electronics must be able to achieve levels of performance equivalent to those obtained when using remote, regulated power supplies in the present system. The proximity of switching converters with the strips and front-end ASICs (less than 5 cm) expose the front-end electronics to conducted and radiated couplings that could compromise the tracker performance. The compatibility can be achieved by appropriate design of the converter, Figure 1: Powering topology.