Power Electronics

Lambda NV-Power Series Provides Class-Leading Power

Lambda’s NV-Power is a new series of class-leading high-density and environmentally friendly ac-dc power supplies that gives designers a "no compromise" solution.

NV-Power is based on a configurable planar transformer and employs multiple efficiency gain (MEG) technology to achieve its class-leading efficiency for multiple-output power supplies. Lambda’s approach is to uniquely use synchronous rectifiers in a resonant topology. The patented multi-resonant-topology (MRT) at the heart of the new design gives a 5% improvement over more traditional ac-dc power supplies.

The new MRT uses closed-loop control of the main outputs, a single conversion stage and auxiliary channels employing high-efficiency dc-dc post regulation. NV-Power has no minimum load requirement on any output channel. The inherent low internal voltages on the secondary side produced by Lambda’s MRT allow the use of low-voltage synchronous rectifiers with minimal losses, which improves the efficiency.

The new topology uses smaller, lower-loss output inductors, along with a ferrite boost choke wound with Litz wire. Improvements in multilayer ceramic and functional organic polymer capacitors enable the use of simplified filter circuits without inductors, increasing efficiency and reducing size. Silicon carbide Schottky diodes in the PFC (power factor corrected) circuit provide a further 4% improvement in efficiency.

Because of these efficiency improvements, Lambda did not have to trade power for size. The first two NV-Power units to be released, the NV-175 and the NV-350, are compatible with a 1-U rack and boast class-leading power densities of 9.36 W/cu in. and 6.6 W/cu in., respectively.

NV-Power employs an 8-bit microcontroller to handle housekeeping routines, replacing multiple discrete components. This reduces the part count by 50% and board space by 40%.

The open construction improves cooling, made easier by the combined benefits of the MRT and MEG design. Reduced heat dissipation and careful thermal management eliminate heatsinks, reducing weight and size, and low airflow volumes allow a slower fan to be used, reducing acoustical noise.

The patented soft-switching MRT design has inherently low EMI emissions, and the use of silicon carbide Schottky diodes minimizes EMI. Moreover, the power IMS (insulated metal substrate) does not rely on chassis conduction cooling, eliminating a potential path for noise currents to ground. This superior design enables the NV-Power 350-W unit to meet medical safety approvals (less than 300 m leakage current) and still meet EN55022 Curve B, typically with a 6-dB margin.

The environmentally friendly NV-Power series exceeds Energy Star guidelines for low power dissipation in operational mode, 50% better than some competing products. It is also designed to be a totally lead-free solution and to meet the European RoHS directive.

For more information, visit www.lambdapower.com.

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