Procedures for Wiener/CAEN power supplies and crates

17th March 2010

Link to Crate/Power Supply Database

Power supplies: general information

Power supplies for sensitive analog front-end electronics is a delicate point that requires significant attention in large scale systems. Power supplies must be used in a fashion compatible to the defined grounding scheme. Analog front-end electronics is in many cases extremely sensitive to noise in the power supply because of the single ended nature of detector signals. It is in most cases required to have separate power supplies for analog and digital front-end electronics to prevent noise from digital circuitry to disturb the analog part.

The question of location of the power supply units and the related transfer of power on cables often have significant problems. Low frequency voltage drops on cables can to a large degree be compensated for by the use of remote sensing to compensate for cable losses. Remote sense can on the other hand also pose stability problems as the compensation loop must be stable under large load variations and with different cable characteristics. In special cases the remote sense circuit must be specially adapted to the final working conditions. High frequency components can only be handled with the use of  local decoupling capacitors.

In most cases a difficult choice must be made between using normal commercial power supplies in the counting room with long cables (~80m) to the front-end electronics in the detector, or having power supplies in the cavern close to the experiment but then having to deal with radiation and magnetic fields. Power supplies for the use in the cavern must be specially designed to handle the radiation effects and the magnetic fields. For the general LHC experiments only few companies are being considered to be capable of supplying power supplies that can handle the environments of the experimental caverns. The CERN ESS group is involved in the qualification of power supplies for the use in the experimental caverns and their purchase via CERN frame contracts.

The power dissipation in power supply cables in the experimental cavern must also be carefully considered as there is only a limited air condition capability in the cavern (already  marginal).

The configuration of power supplies are strong linked to general grounding.

Power supplies for crates must also be considered critical.

A special set of radiation tolerant linear regulators have been developed for the LHC experiments.

Wiener Maraton power supplies for use in radiation and magnetic fields
Presentation of radiation and magnetic field tests made my CERN ESS 2
Presentation of radiation and magnetic field tests made by CERN ESS 1
Presentation by Wiener November 2003

CAEN power supplies for use in radiation and magnetic fields
Presentation by CAEN November 2003

Electronics meeting dedicated to power supplies in November 2003 LHCb week.

Measurements of the electronic crates for LHC experiments. Report. K. Kahle, A. Funken. 18-11-2003: 

General points to be aware of:

• Prevent ground loops via power supplies when ever possible
• Use floating low voltage power supplies.
• Use twisted power cables to minimize noise pickup/generation.
• Use remote sense to compensate for voltage drops on cables
• Remote sense must be fully differential to minimize noise pick up
• Remote sense must be capable of compensation for voltage drop in power supply return (known problem with radiation tolerant linear regulators from ST)
• Take special care of high voltage and its distribution.
• No single point failure must generate safety hazards ( e.g. high voltage connected to accessible structure).
• Separate if possible power supplies for analog front-end from power supplies for digital logic.
• Sudden power consumption drop may generate serious over-voltage on load. Extensive local decoupling and over voltage protection may be needed.
• Magnetic coils/transformers and cooling fans in power supplies are sensitive to magnetic fields.
• Power supplies are known to be sensitive to single event burn-out caused by hadrons.
• Switching mode power supplies are known to in some cases to generate significant common mode noise
• TO BE EXPANDED

This page was last modified by KW on 20 August, 2021.