Power supply unit for emergency lamps that may need to be used in areas
with radiation. The power supply consists of a transformer, a diode
bridge, capacitors and an optional voltage stabilisation device. It
converts a 207V to 253V 50Hz AC to a stable DC voltage and current, as
required by the LED load.
Note: It is possible to increase the radiation hardness of the power supply by a factor of up to 10x by replacing the Si diodes with SiC based diodes. This has not yet been implemented in the reference design, but is on our list for future improvements.
Relevant standards to be observed: IEC 61000-3-2, EN 55015, EN
50082-1, EN 50082-2
Whilst the standard conditions of the electrical network dictate 230V AC
with a margin of +/-10, due to cabling constraints within radiation
exposed areas it would be considered advantageous should the supply
continue to operate below the -10 threshold. Please note that compliance
with the standards requires the power supply to be installed within a
suitable enclosure, it is assumed this will be the responsibility of
those manufacturing the power supply and integrating it within their
The power supply consists of a transformer, a diode bridge, capacitor(s)
and optional voltage stabilisation device. It converts 50Hz AC voltages
from 207V RMS to 253V RMS to a stable DC voltage, as required by the LED
load. The power supply is designed to supply the current requirements of
the connected LED load.
The Altium PCB schematics in the zip file provided for download comprise
1) Unregulated design for a single LED (e.g. Cree XR-E)
2) Regluated design for a single LED, requiring the LHC4913 radiation
resistant voltage regulator IC. This is a CERN developed part provided
by ST and may not be available for everyone.
3) Unregulated design for three LED string (higher output voltage due
to modified resistor configuration).
The radiation-hard voltage regulator L4913 was developed by ST
Microelectronics in collaboration with CERN to satisfy the radiation
requirements of the LHC (Large Hadron Collider). Its radiation hardness
has been extensively tested using X-rays, 60Co, and a pion beam. The
regulator appears to tolerate TID (total ionizing dose) levels above 100
Mrad, and 1 MeV equivalent neutron fluence above 1.9×1015 cm-2. The
radiation resistance of the regulated designs should be equivalent to
these levels, with the unregulated design significantly exceeding these
levels. Luminaires based on these designs are now installed in activated
parts of the accelerator complex and their performance is being
monitored on an ongoing basis.
Please note that the radiation resistance of the LED's (or other
connected equipment) themselves, and their light output and lifetime in
a radioactive environment, may not reach the levels of reliability
provided by this power supply. Now that the power supply design has been
released this is a current research topic for this