Direct-coupled it load

Abstract

Apparatus and associated method and computer program products involve a highly efficient uninterruptible power distribution architecture to support modular processing units. As an illustrative example, a modular processing unit includes an integrated uninterruptible power system in which a PFC-boost AC-to-DC conversion occurs between the utility AC grid and the processing circuit (e.g., microprocessor) loads. In an illustrative data center facility, a power distribution architecture includes a modular array of rack-mountable processing units, each of which has processing circuitry to handle network-related processing tasks. Associated with each modular processing unit is an integrated uninterruptible power supply (UPS) to supply operating power to the network processing circuitry. Each UPS includes a battery selectively connectable across a DC bus, and a AC-to-DC rectifier that converts an AC input voltage to a single output voltage on the DC bus. The regulated DC bus voltage may be close to the battery's fully charged voltage.

What is claimed is: 
     
         1 . A method comprising:
 connecting a rack mountable processing unit to a power source, the power source being configured to receive AC power from an electric utility grid and to provide the received AC power to the rack mountable processing unit without any intermediary AC/DC conversion or conditioning of the AC power, wherein the rack mountable processing unit is mounted in a position in a rack and includes a base supporting:   a DC load comprising at least one digital processor operative to process data received over a network;   a DC bus configured to deliver operating power to the DC load; and   an uninterruptible power supply (UPS), the UPS comprising:
 a battery circuit configured to operatively connect a battery across the DC bus during a fault condition in which the received AC power falls outside of a normal operating range; and 
 an AC-to-DC rectification stage comprising an AC-to-DC conversion circuit configured to filter noise and harmonic components from the received AC power, correct a power factor of the received AC power to a power factor closer to unity, and to convert the filtered and corrected AC power to a single DC output voltage signal across the DC bus when the received AC power is within the normal operating range; 
   detecting that the received AC power falls outside of the normal operating range;   in response to detecting that the received AC power falls outside of the normal operating range, connecting the battery across the DC bus instead of the DC output voltage signal of the AC-to-DC rectification stage;   detecting that the received AC power has returned to the normal operating range; and   in response to detecting that the received AC power has returned to the normal operating range, connecting the DC output voltage signal of the AC-to-DC rectification stage across the DC bus instead of the battery.   
     
     
         2 . The method of  claim 1  comprising regulating the DC output voltage signal to a set point voltage above and substantially near a maximum nominal charge voltage of the battery. 
     
     
         3 . The method of  claim 2  comprising selecting the set point voltage based on operating conditions of the back-up battery 
     
     
         4 . The method of  claim 2 , wherein the set point voltage is approximately 1 Volt above the maximum nominal charge voltage of the battery. 
     
     
         5 . The method of  claim 1  further comprising presenting a combined power factor of the multiple rack mountable processing units, the combined power factor being at least 0.95. 
     
     
         6 . The method of  claim 5  wherein the combined power factor is at least 0.98. 
     
     
         7 . The method of  claim 1  wherein the AC power received from the electric utility grid comprises a phase voltage signal and a neutral signal from a three phase AC system. 
     
     
         8 . The method of  claim 1  wherein the AC power received from the electric utility grid has an r.m.s. value between about 85 Volts and at least about 480 Volts. 
     
     
         9 . The method of  claim 8  wherein the AC power received from the electric utility grid has an r.m.s. value of about 208 Volts to about 277 Volts. 
     
     
         10 . The method of  claim 1  wherein the single DC output voltage signal is less than about 26 Volts. 
     
     
         11 . The method of  claim 1  wherein the single DC output voltage signal is between about 10 Volts and about 15 Volts. 
     
     
         12 . The method of  claim 11  wherein the single DC output voltage signal is about 13.65 Volts. 
     
     
         13 . The method of  claim 1  comprising:
 storing delay time parameters for the multiple rack; 
 delaying for a time period after detecting that the received AC power has returned to the normal operating range and before connecting the DC output voltage signal of the AC-to-DC rectification stage across the DC bus instead of the battery, said time period corresponding to the delay time parameter in the data store. 
 
     
     
         14 . The method of  claim 13  wherein the stored delay time parameter comprises a pseudo-randomly generated value. 
     
     
         15 . The method of  claim 1  wherein the AC-to-DC conversion circuit is of a continuous conduction mode (CCM) type including average current mode control (ACMC). 
     
     
         16 . The method of  claim 1  wherein the AC-to-DC conversion circuit is of a critical conduction mode (CRM) type. 
     
     
         17 . The method of  claim 1  wherein detecting that the received AC power falls outside of the normal operating range comprises receiving a signal that indicates the received AC power falls outside of the normal operating range. 
     
     
         18 . The method of  claim 1  wherein detecting that the received AC power has returned to the normal operating range comprises receiving a signal that indicates the received AC power has returned to the normal operating range.