The Preamp Power Supply provides power for the charge-to-voltage hybrids, Calorimeter Preamp electronics. The hybrids are located in 12 separate boxes with each box containing two halves. Each half has two columns of Preamp cards, called a motherboard, with 48 hybrids on each board. Power is supplied to each column of cards, four total columns in each box.
The power supply provides three (3) power rails required by the electronics. These voltages are +12V, +8V and -6V. Since each supply provides power for each box these rails are subdivided into eight (8) outputs supplying approximately the same power level.
Output ratings are as follows
A 12V 20A
B 12V 20A
C 8V 20A
D 8V 20A
E 8V 20A
F 8V 20A
G -6V 25A
H -6V 25A
As seen in the illustration +12(A,B) and -6 (G,H) provide power for two columns while +8 (C,D,E,F) powers each column separately.
This diagram shows the power requirements of one Preamp Box of electronics.
The supply assemblies are built around a commercial Vicor switching power supply. The AC input power is controlled with a 3-phase solid-state relay. The three raw voltage rails are divided and fused to distribute power to the columns of preamps. The DC output of the Vicor is enabled or disabled by the user. Protection circuitry monitors output voltage and current as well as temperature to protect the supply and its load.
The supply can be remotely controlled and monitored via a Rack Monitor chassis.
It should also be noted that the output voltages are set almost 1 Volt above the required hybrid voltages, i.e. the 12, 8 and 6 rails are 13, 9 and 7 respectively out of the supply. There is no remote sensing used and the extra voltage is dropped across the wiring harness.