Speaker
Description
Summary
A high voltage system includes 60 high voltage power supply channels in a 2U height
EURO crate. The system is composed of 20 high voltage (HV) card and an interface
card, where the interface card is located at the 21-th slot. Three high voltage
power supply channels are implemented on the HV card with control logic. A back-
plane bus is shared among the cards for communication and voltage distribution.
A ceramic transformer is utilized to generate high voltage in the channel. The high
voltage is rectified to be the output voltage. A driver circuit generates a carrier
to drive the ceramic transformer. The HV card is supplied with 3.5 V and ±5V. The
driver circuit is supplied with 3.5 V. An analog circuit to stabilize the output
voltage is powered by ±5V. The control logic on the HV card is mostly digital
logic electrified by 5 V. The system is supplied in total with 40 A of 3.5 V, 20 A
of 5 V and 1 A of -5 V.
The interface card is equipped with USB interface, and the high voltage system is
connected to a computer by a USB cable. The channel can supply the output voltage
ranging from 1 kV to 4 kV with a load of larger than 30 Megohms. Ripples on the
output voltage is less than 100 mV in peak-to-peak amplitude. The output voltage
can be set and monitored with 1 V resolution. The output current is monitored with
9-bit resolution at the sampling rate of 80 Hz. The channel is provided with over-
current shut-down. A hardwired logic turns off the output voltage when the output
current exceeds a prescribed limit current in a predefined time interval, where the
limit current and the time interval can be set by the computer.
The ceramic transformer takes the place of the conventional magnetic transformer.
The ceramic transformer utilizes piezoelectric effect to generate high voltage. The
ceramic transformer is constructed from a ceramic bar and does not include any
magnetic material. So the transformer is free of leakage of magnetic flux and can be
operated efficiently under a magnetic field. The high voltage system can work
without a loss of efficiency under a magnetic field of 1 T.
The HV cards have been irradiated by cobalt 60 up to 300 krad successfully. The HV
cards have been exposed to a protons flux at PSI. The exposure amounts 60 MeV 1E11
protons without causing problems. The exposure is equivalent to 1E11 neutrons and 14
krad. So the radiation test shows the HV card and then the high voltage system
satisfies CERN Radiation Hard Criteria required for TGC power supplies.
The high voltage system is now used in a beam test of TGC in CERN. The high voltage
system is now put to final cost reduction. The price is not yet settled, while the
design goal of the price is targeted between 100 euros and dollars per channel.
