Application Note AN4390
November 2013
The UPS (uninterruptible power supply) is gaining ever increasing importance in office and industrial environments, because it preserves the information and business operations from power supply failure or blackout. Thanks to its technological improvement, it is now suitable both for big customers and for individual users. The right designer's choice about MOSFETs in DC-AC (H-bridge converter) section enhances the overall system performance: THD, power and thermal management and short-circuit ruggedness. In this article, ST's MOSFET technologies are described, highlighting their benefits as well.
Uninterruptible power supplies (UPS) are widely used to avoid a sudden loss of data or information caused by a power supply disconnection (blackout). Power and voltage spikes, supply frequency changes, noise and radio frequency interference affect negatively the load. In figure, the basic schematic of a "standby UPS" is shown; it is the most common type of UPS present in the market. Surge suppressor and input filter protect the output equipment respectively from current spike and noise coming from input line. During an input supply failure, the transfer switch enables the battery-powered path.
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Standby UPS schematic
