Author:
Reported by Cliff Keys, Editorial Director, PSD
Date
09/02/2011
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I talked with Mark Adams, CUI's VP of Advanced Power Marketing, about CUI's new power topology which is set to propel quarter-brick bus converter to benchmark power density. CUI is leveraging their Solus Power Topology™ to pioneer a new era in dc-dc power supply performance. Solus is an entirely new topology, rich in features that accelerate the performance trend trajectories for the big-four power conversion needs: higher power density, higher efficiency for "greener" systems, faster transient response, and lower EMI. CUI is introducing their NQB2060 Novum® quarter-brick bus converter as a prime example of the benchmark 720 watts output power performance using their Solus Topology.
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Implementing the "divide and conquer" concept, the Solus Topology accomplishes the reduction of conduction losses by channelling the operating currents into several paths. Figure 1 shows the schematic for the Solus Topology SEPIC-fed buck converter topology. Q1SB functions as high-side switch for both the SEPIC and buck operation. Q2B functions as the lowside switch in buck operation. Q2S functions as part of the SEPIC operation. Note that as soon as the input current enters the converter at I1, the topology immediately branches that current into several paths, with each circuit path carrying lower instantaneous current than the output current, IOUT. This reduces the conduction losses by the square of the current reduction identified in Figure 1. Thus, the conduction losses are significantly less when compared to standard buck converter losses. The reduced imposed current through the MOSFETs allows the design to obtain lower losses for a given set of devices. CUI's Solus Topology integrates a conventional buck converter into a SEPIC converter to form a totally new SEPIC-fed buck converter; a patented 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 GCE (gate charge extraction) process, Solus 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%. With these advantages, CUI is now in a position to develop a wide range of ac-dc and dc-dc power conversion platforms with greatly improved energy efficiency, faster transient response and increased power density versus the leading designs currently on the market.
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The chart demonstrates the total high-side transistor switching loss when comparing the Solus converter to the traditional standard buck converter. Observe that, as the voltage step-down ratio "M" moves from 0.100, to 0.250, to 0.660, the Solus losses are improved by 91%, 88%, and 70%, respectively. Thus, the Solus Topology is ideal for wide-conversion-ratio POL applications. The NQB Series isolated dc-dc quarter brick based on their patented Solus Power TopologyTM. As part of CUI's Novum Advanced PowerTM portfolio, the 720 W intermediate bus converter will initially support an input range of 36-60 V with an output of 12 V and will provide an efficiency greater than 96%. The NQB product will eventually support a wider input range as well as an output of 9.6 V. Additional features include options for DOSA 1st generation or 2nd generation footprint compatibility, remote on/off, and load share capability. The NQB Series aims to address the trend of rising power requirements and efficiency demands in telecom systems and data centers, supplying an industry leading power density of 445 W/in3 across the full 36-60 V input range. Mark explained, "This is the first product of many that will be based on the Solus Topology. The flexibility of the Solus Topology will allow us to not only incorporate it into an isolated dc-dc solution, but will also move to our non-isolated dc-dc and ac-dc product roadmaps, in today's green world where efficiency and density is king, we believe our Solus Topology will be a difference maker in the market for years to come." Since the Solus Topology maintains it effectiveness independent of the control method used, it can operate with analog voltage mode control, analog current mode control, and various digital control profiles. That opens the door for CUI to implement this topology in a wide variety of power supply product platforms. The Solus Topology can also improve the performance of the isolated high-voltage dc-dc section of the ac-dc power supply. Since it can operate very efficiently over a wide voltage range, companies can substantially reduce the amount of the bulk hold-up capacitance, reducing the total cost of the power supply. CUI has been sampling the NQB product to selected customers and will continue to provide engineering samples to customers until full production release in Q1 2012. About CUI Inc CUI Inc is a technology company dedicated to the development, commercialization, and distribution of new, innovative electro-mechanical products. Over the past 20 years, CUI has become a recognized name in electronic components worldwide in the areas of power, interconnect, motion control, and sound. CUI's solid customer commitment and honest corporate message are a hallmark in the industry. CUI is a wholly-owned subsidiary of CUI Global, Inc. For more information, visit www.cui.com
