Intermediate Bus Voltage Optimization for High Voltage Input VRM

Investigations have been carried on into improving the efficiency in the power delivery system. A new architecture is introduced in this paper, which is a high voltage (HV) DC input voltage regulator module (VRM) to replace today´s AC-DC silver box and 12V input VRM, i.e.. Study shows that the system efficiency will improve 8%, under the prediction that the efficiency of this kind of high voltage input VRM is about 85% based on paper research and simulations, if this is the case, a revolution will be taken place in the power delivery in the data center for the next generation server platform. A two-stage approach as the proposed circuit is evaluated, where the 1^st stage is a unregulated DC to DC converter converting 400V input to low voltage intermediate bus, and the 2^nd stage is a 2-phase buck converter converting the intermediate bus voltage to 2V_to 3.3V variable voltages. This paper uses its major part to introduce a practical method on how to find the best intermediate bus voltage to trade off the efficiencies of the two stages in order to get the optimized efficiencies of the overall load range. Simulation /calculation on the commercial voltage levels of 5V, 6V, 7V to 12V show that 8V is the optimized bus voltage considered the efficiencies in the overall load range, the experimental results show the same conclusion as well.