Using Local Energy Storage For Organized System Shutdown Simplifies Power Supply Hold-Up Time Requirements
by Viktor Vogman, Power Conversion Consulting, Olympia, Wash., How2Power Today, Sep 15 2020
Focus:
Traditionally, the energy needed for organized system shutdown is stored in the PSU
bulk capacitor, which supplies power to the entire system during an ac fault event.
When warning time needs to be significantly extended (5 to 10 ms) for organized
shutdown mode, a straightforward solution is to increase the PSU bulk cap size. But
this greatly increases power supply size and cost, especially in server redundant
subsystems using two or more PSU modules. This article studies an opportunity for
easing PSU hold-up time requirements when extended warning time is required. It shows
how a local buffer capacitor can supply power just to the components critical to
system shutdown while increasing system immunity to indiscriminate power faults. The
article analyzes the conditions (i.e., buffered power share and allowed voltage droop)
under which the capacitor required for secondary-side energy storage (at the point of
load) is smaller than the capacitor required for primary-side energy storage (the
bulk cap). Different circuit options for secondary-side energy storage are presented.
What you’ll learn:
- How to simplify power supply hold-up requirements while meeting requirements for organized system shutdown
- How to extend warning time for organized system shutdown to 5 to 10 ms by buffering power to critical loads
- How to extend warning time for organized system shutdown without increasing the size of the power supply’s bulk capacitor
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