A recently introduced application note from Texas Instruments (TI) documents how to use high-voltage energy storage techniques to reduce size and cost of transient holdup circuitry on ATCA boards. Though holdup energy in telecom systems is normally stored at -48 V, it is possible to store energy at high voltage (-72 V), reducing requirements for holdup capacitance. The high-voltage energy storage technique described by TI’s Jim Bird is well suited to ATCA systems where up to 2 J of stored energy is required on each board. However, the technique also may be applied in other applications with 48-V supplies.
In this application note, the author discusses holdup requirements in ATCA systems and then calculates the amount of capacitance needed to meet the holdup requirements when storing energy at a -43 V. He then calculates the hold up capacitance required when storing energy at -72 V. The latter approach results in an almost 90% reduction in capacitance while still keeping the voltage within the input range of standard telecom-style dc-dc converters.
The author presents “pump and dump circuitry” needed to implement the high-voltage energy storage. The first circuit boosts the input voltage for storage while the second circuit dumps the energy into the load during transients. The key components used to implement these circuits are the UC2572 negative boost converter and—in the dump circuit—two comparators, a one-shot, and a FET switch.
To see the application note, visit focus.ti.com/docs/apps/catalog/resources/appnoteabstract.jhtml?abstractName=slua331.