赵闯UC如何均流外文文献简析.doc

APPLICATION NOTE U-163 Laszlo Balogh Unitrode Corporation THE UC3902 LOAD SHARE CONTROLLER AND ITS PERFORMANCE IN DISTRIBUTED POWER SYSTEMS UNITRODE CORPORATION APPLICATION NOTE U-163 THE UC3902 LOAD SHARE CONTROLLER AND ITS PERFORMANCE IN DISTRIBUTED POWER SYSTEMS by Laszlo Balogh Unitrode Corporation UC3902 APPLICATIONS The current demanded by large electronic systems continuously rises due to higher performance and increased functionality. At the same time, supply voltages, especially in digital circuits, are falling to previously unprecedented low levels. The combination of higher load currents and low supply voltages impose difficult requirements on the power distribution and in most cases, forces a higher voltage distribution bus with local voltage conversion. Users of distributed power systems are seeking reliable and economic solutions to supply their loads. A modular approach, where stand alone power supplies are utilized for local power conver- sion, is widely accepted in these applications. The power rating of the individual converters are usu- ally limited by the available height, board space and by the limitation on volumetric heat dissipation. High current loads are supplied by several parallel connected power supplies. In addition to higher currents, the parallel modules can also offer redundancy, an important factor to achieve reliable, uninterrupted operation and extended life expectancy in these systems. Parallel connected power supplies require a dedicated control mechanism, called load share circuitry to assure full utilization of the system. The purpose of a load share controller, like Unitrode’s UC3902, is to provide for equal distribution of the load current among the parallel connected power supplies. By equalizing the output currents, uniform thermal stress of the individual modules is also ensured which has the utmost importance for long term reliability of electronic components. For the UC3902 to work properly, the m