Variable Voltage PSU Technology for ICT Applications

Abstract:
ICT power supply systems are facing considerable challenges in the future. Especially in the datacom applications power demand has been rising on continuous basis. At the same time the pressure generated by rising energy cost and global need to minimize the greenhouse effect is getting heavy. Therefore, energy efficiency of ICT power supply systems must be considered carefully so that the ecological footprint can be kept tolerable also in the future. In order to achieve the goal of minimized negative environmental impact of ICT power systems, the following issues must be considered: power system architecture, load management and efficiency of each power system element. Increasing power system efficiency is the best near term means to solve the challenge of rising cost and green house gas emissions. This paper concentrates on novel power supply unit (PSU) technology developed for this purpose. One viable possibility to cut energy consumption of ICT loads is to control the supply voltage of the load devices according to the actual operating state of the unit. In datacom systems this means scaling the processor system supply voltage according to the actual operating mode (e.g. idle, sleep mode, 50 % processing capacity and full power). The same principle can be utilized also in cellular network applications, especially in RF amplifiers for base tranceiver stations (BTS). Two PSU technology options are available depending on the dynamical needs of load voltage control. Average power tracking power supply is based on rapid switching between predefined output voltage levels according to the actual load demand. In envelope tracking method the output voltage of the PSU dynamically follows the required signal envelope waveform. It has been proved that variable voltage PSU technology can provide considerable increase in efficiency of RF power amplifiers. On the other hand, variable supply voltage can have effect on other operational characteristics of the system and challenges in e.g. amplifier linearization can occur. Therefore, close co-operation between the power supply and load electronics designers is necessary in order to achieve an optimized solution.