Digital Signal Processing Solutions September

Application Report SPRA589 Digital Signal Processing Solutions September 1999 Implementing Triple Conversion Single-Phase On-line UPS using TMS320C240 Shamim Choudhury DCS Applications Abstract Uninterruptible power supplies (UPS) play an important role in interfacing critical loads such as computers, communication systems, medical/life support systems, and industrial controls to the utility power grid. Among the various UPS topologies, on-line UPS provides the most protection to such loads against any utility power problem. However, because of the multiple power conversion stages, on-line UPSs have been the most complex and expensive type of system.Today's low- cost, high-performance digital signal processor (DSP) controllers, such as the Texas Instruments (TI?) TMS320C24x, provide an improved and cost-effective solution for on-line UPS design. This application report discusses the different implementation aspects of a DSP based on-line UPS design using a TMS320C240. Contents Introduction ......................................................................................................................................................3 System Overview .............................................................................................................................................4 Sampling Cycle ................................................................................................................................................8 Output Inverter Stage.....................................................................................................................................11 Inverter Controller Implementation .....................................................................................................13 Output Inverter Voltage and Current Sensing.....................................................................................14 Battery Charger..............................................................................................................................................17 Battery Charging Procedure ...............................................................................................................18 Battery Charger Control Algorithm......................................................................................................19 Battery Charger Controller Implementation ........................................................................................20 Battery Charger Voltage and Current Sensing ...................................................................................22 Input Power Factor Control (PFC)..................................................................................................................26 PFC Controller Implementation ..........................................................................................................28 Input PFC Voltage and Current Sensing.............................................................................................31 Battery Voltage Boost Stage ..........................................................................................................................34 Boost Stage Controller Implementation ..............................................................................................36 Boost Stage Voltage and Current Sensing .........................................................................................38 Software Organization....................................................................................................................................38 Experimental Results .....................................................................................................................................43 Appendix A Example Code ...........................................................................................................................45

• conversion single-phase


• loads such


• conditioning performance


• output inverter


• input power