CUI uses SEPIC-fed buck DC/DC topology in 720W intermediate bus converter

March 18, 2014 // By Graham Prophet
Calling it a second-generation high density isolated intermediate bus converter, CUI has used its recently introduced Solus technology, which combines SEPIC and buck circuit configurations, to build the NQBS seriesfor the rising power requirements and efficiency demands in telecom systems and data centres.

The NQBS modules are housed in a quarter brick package and deliver a power density of 27.2 W/cm 3 (445 W/in 3) as well as efficiencies in excess of 96%. The Solus Power Topology, CUI claims, delivers a greater power density, higher efficiency, faster transient response, and lower EMI in both isolated and non-isolated dc-dc converter designs. The module incorporates full regulation across the entire 42~60 Vdc input range and a droop load share feature with 10% current share accuracy for higher power boards.

CUI first used the topology in a recently-announced point-of-load regulator.

As part of CUI’s Novum Advanced Power portfolio, the 720W NQBS series outputs 12 Vdc at 60A in an industry standard DOSA footprint (58.4 x 36.8 x 12.3 mm) and provides input to output isolation of 2250 Vdc. Additional features include insulation that meets EN60950 standards, remote on/off control, and an optional heat sink for improved thermal performance.

The module’s Solus topology integrates a conventional buck converter into a SEPIC converter to form a SEPIC-fed buck converter; a single stage architecture with one magnetic element, one control switch, and two commutation switches that are optimally controlled by pulse-width modulation (PWM). With lower voltage and current stresses in the topology coupled with an inherent gate charge extraction (GCE) process, the architecture is able to reduce switching turn-on losses by 75% and switching turn-off losses by 99% on the control FET compared to a conventional buck converter. The Solus Topology further increases total efficiency by distributing the energy delivery into multiple paths, reducing circuit conduction losses by nearly 50%.