Energizing Output Filter Inductor Enables Instantaneous PSU Activation
by Viktor Vogman, Olympia, Wash., How2Power Today, Sep 15 2025
Focus:
Using a cold redundancy technique to wake up a battery backup module allows for
accelerated power supply wake-up. It is based on precharging output capacitors to their
steady-state voltage levels. In this case, a soft start is not required, as only the
output filter inductor needs to be charged to the current matching the current consumed by
the load. Although a full power stage activation in this case typically lasts only a few
hundred microseconds, the usage of this technique still requires much larger dc bus
capacitor values than would be needed in the “ideal” instantaneous wakeup case. To
overcome this limitation, this article discusses the opportunity to “precharge” the output
filter inductor along with the output capacitor, to further accelerate the backup module
activation process. After quantifying the reduced capacitance requirement with
instantaneous power supply activation, a circuit is presented for energizing the output
filter inductor’s core. Then, its operation is explained and verified through simulation.
Some design considerations for implementing the proposed circuit are also discussed.
What you’ll learn:
- How to speed activation of a battery backup power supply by pre-energizing its output filter inductor
- How to reduce dc bus capacitor requirements through instantaneous activation of backup power supplies
View this Source (requires a PDF Viewer installed on your device)
© 2025 How2Power. All rights reserved.