Accelerating UPS Wake-Up Can Improve Power Supply Efficiency

by Viktor Vogman, Power Conversion Consulting, Olympia, Wash., How2Power Today, Nov 15 2019

Focus:
For data centers where downtime is unacceptable, standby UPSs are usually insufficient and use of double conversion (online) UPSs is required. But recently the standby UPS has expanded its usefulness in the form of the dc UPS, which integrates battery backup modules into the server power subsystems. This articles explains how speeding up the standby UPS wake-up process creates an opportunity for significant efficiency improvements by taking advantage of both online and offline UPSs. Implementation aspects and benefits of such backup power architectures are discussed. Article begins by explaining the processes that occur during the hold-up time (HUT), when the UPS is switching to battery power, derives an expression for the bulk capacitor voltage as a function of HUT, and discusses how shortening HUT can improve power supply efficiency. It then discusses techniques which can be applied to shorten HUT including disabling soft start of the BBUs and speeding up ac fault detection for the ac-dc power supply. Example calculations demonstrate the potential improvement in dc UPS efficiency obtainable when accelerated wakeup is employed. Finally, some additional ideas are presented for using fast ac and dc fault signals to speed wakeup and improve efficiency in dc UPS architectures.

What you’ll learn:

• How to obtain improvements in data center power delivery efficiency using dc UPSs in combination with techniques that shorten power supply hold-up time requirements

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