This paper describes the design of an Lee resonant tank that is to be used in a 300k W modular power converter for an application in particle accelerators. The aim of the power supply is to provide a so-called RF cavity with 25k V De and a current up to SA. Modular approach is chosen for redundancy and availability. Each module is composed of a resonant tank with a step-up Medium Frequency Tr ansformer with its secondary windings put is series. Full gain is ensured in the full operation frequency range considering component value inaccuracies and ageing of capacitors. The paper focusses on the design of the resonant tank and its implementation in a lOOkW power module prototy pe.

A major upgrade will be conducted in the Large Hardon Collider (LHC) at CERN. This high luminosity (HL) version of the LHC will increase the nominal luminosity by a factor of five. One of the key technologies of the HL-LHC are the new superconducting Inner Triplet (IT) magnets, responsible of producing high magnetic fields to focus particle beams. To power the IT magnets from the grid, a multi-stage power supply with an intermediate 24 V battery pack is being considered. In such topology, a lowvoltage high-current DC/DC converter operating with a very high step down-ratio is required for the final conversion stage. In this work, an interleaved multiphase Series Capacitor Buck converter is proposed to feed the IT magnets from the battery pack. A novel voltage regulation approach that ensures the current balance between the paralleled Series Capacitor cells is also proposed, where one cell is responsible for the output voltage regulation, while the remaining cells are current regulated. A balanced current sharing between the Series Capacitor cells is achieved, when the current controlled cells are referenced by the actual current of the 1st one. The proposal is theoretically analysed and experimentally validated in a six cell 1000 A prototype unit. Index Terms-Control of multiphase DC/DC converters, Series Capacitor Buck converter, Large Hadron Collider I. INTRODUCTION T HE Large Hadron Collider (LHC) at CERN (Geneva, Switzerland) is the largest particle accelerator and one of the biggest research facilities in the world [1]. This 27 km long circular machine accelerates hadron (proton) beams to 99.99 % of the speed of light, generating new particles as a result of proton-proton collisions at high energies. To extend its Manuscript received Month xx, 2xxx; revised Month xx, xxxx; accepted Month x, xxxx.

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This paper focuses on the study and the implementation of a 25kV / 200kW / 20kHz rectifier intended to supply radio frequency power amplifiers with a DC voltage in a precision range of 1000ppm. The topology is based on three LCC resonant modules, and the high voltage part uses three 100kW / 20kHz power transformers connected to 72 diode full-bridge rectifiers connected in series. The design of such transformers as well as the management of the voltage balancing between the rectifiers and between the modules constitute new challenges addressed in this paper. The key design points of the transformers are described. Then, a simulation based analysis presents the issues in balancing powers and voltages between the modules. All the presented results are validated by experimental measurements on a full scale system.

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