Accelerator Power Supplies Division

Switch Mode Power Converter Section (SMPCS)

Ongoing Activities
  1. FPGA Based Digital Controller
  2. High Stability (± 10 ppm) Power Converters
  3. Automated Test Bench (ATB)
  4. Reliability studies

FPGA Based Digital Controller

Presently, the feedback control loop in power converters developed by SMPCL is based on OPAMP based analog techniques which suffers from inherent disadvantages such as component tolerances, temperature drift, time drift, difficulty in power converter calibration, and inflexible design. To overcome these problems, a prototype digital controller is being developed using FPGA for use in future accelerator projects at RRCAT. So far, a table top digital controller has been developed and implemented using a Xilinx Spartan3AN FPGA kit programmed in VHDL and interfaced with a 16 bits ADC card. The controller is tested with a prototype magnet power converter of rating 80 A/20 V thereby achieving control loop bandwidth of 1.6 kHz and output current stability of 100 ppm. Efforts are being made to standardize the design on a 4 U card and further improve stability.

High Stability (± 10 ppm) Power Converters

Future accelerators such as Low Emittance Storage Ring (LESR) would demand power converter with output current stability of the order of ±10 ppm. While power converters with output current stability of ±50 ppm have been successfully developed and are being regularly used in Indus-2, the development of a magnet power converter with ±10 ppm stability would need special attention broadly in two areas - (1) power converter along with the control electronics and (2) precision sensing, and measurement of magnet current for performance qualification. Both these aspects need major technological up-gradation and new developments, and are being presently looked into.

Automated Test Bench (ATB)

A large number of power converters are required to energize various electromagnets in particle accelerators. It therefore becomes imperative to carry out thorough testing of these power converters before they are deployed in the system to ensure intended functionality and overcome the infant mortality. Of late, various type tests, test sequences and test parameters have been conceived to evaluate a power converter performance. However, they are presently being executed mostly manually with the help of remote interface module. Automation is expected to facilitate conducting routine test on magnet power converters in an orderly, streamlined and more efficient manner with proper documentation of the test results. Therefore, an Automated Test Bench (ATB) is being developed to facilitate automated testing of power converters. It consists of a control interface module (CIM), DCCT racks, oscilloscope, data logger, master patch panel and a computer.

Reliability Studies

The estimation of reliability becomes particularly important for magnet power converters being used in particle accelerators because of large number of power converters and their continuous 24X7 operation. A failure of single power converter can lead to loss of particle beam, synchrotron radiation and user time. Hence it is proposed to estimate reliability of power converters used in Indus complex so that weak links/components can be identified and rectified in order to achieve high availability of system. It is also proposed to carry out comprehensive comparative reliability studies for various power converter topologies used in accelerators such as SMPS topologies, linear power converters, etc.