A very low noise AC/DC Power Supply System for large arrays of cryogenic detectors

In this work we present the first part of the Power Supply System for the CUORE and LUCIFER arrays of bolometric detectors. It consists of an AC/DC (0 ÷ 60 V output) commercial supply voltage followed by a system composed of DC/DC modules. Every DC/DC module (48 V input, ±15 V output) is laid-out on a 2 layers 220×236 mm² PCB (standard Eurocard). Each module has 3 independent configurable output voltages whose purpose is to provide 3.3 V or 5 V, for the digital circuitry, and a pairs of bipolar supplies selectable from ±5 V to ±12 V. The GND of each output is isolated from the each others to avoid any possible ground loop. The whole system is completely programmable (and monitored) via CAN-bus (optically coupled). A very low (switching) noise, as required for the above mentioned experiments, was met: in the 20 MHz bandwidth the peak-to-peak level is about 0.6 mVpp at a load of 2.6 A per module. This becomes about 0.88 mVpp at 4.3 A load. The efficiency of the system is above 85%.