60A point-of-load regulator blends buck and SEPIC topologies

March 06, 2014 // By Graham Prophet
Using a circuit layout that it calls SEPIC-fed buck, CUI has designed a 60A output, digital-control loop DC/DC point-of-load module that achieves higher power density, higher efficiency, faster transient response, and lower EMI.

NDM3ZS-60 is a non-isolated module outputting 60A from low-profile vertical and horizontal packages. The series is the first non-isolated design to incorporate CUI’s Solus power topology which integrates a conventional buck converter into a SEPIC converter to form a SEPIC-fed buck converter; a single stage topology 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 topology is able to reduce switching turn-on losses by 75% and switching turn-off losses by 99% on the control FET when 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%. As the buck converter is turning off, the SEPIC path is feeding the output, placing less ripple on the input current.