Switchers won't compromise on efficiency

A power supply without compromise is every designer's dream, and Lambda reckons its new NV-Power range turns that dream into reality.

A power supply without compromise is every designer's dream, and Lambda reckons its new NV-Power range turns that dream into reality.

Pushing back the barriers, the company describes NV-Power as a new range of class leading high density and environmentally friendly AC/DC power supplies that gives designers their no compromise power solution.

"Limited levels of efficiency have always meant that AC/DC power supplies come with tradeoffs", explains Martin Southam, Lambda Europe Marketing Director.

"Certain aspects have always had to be compromised, be it output power, size, minimum load, noise, or EMC performance.

In NV-Power we have an AC/DC power supply technology that cuts switching losses by 50% to deliver an unparalleled efficiency of up to 90%.

It is this massive leap forward in efficiency that has enabled us to create a range of power supplies that do not compromise any of the fundamentals".

NV-Power is based around a configurable planar transformer, and employs multiple efficiency gain (MEG) technology to achieve its class leading efficiency for multiple-output PSUs.

The Lambda approach is essentially a unique use of synchronous rectifiers in a resonant topology.

The patented multiresonant-topology (MRT) that lies at the heart of the new design gives a 5% improvement in efficiency over more traditional methods.

AC/DC products commonly use magamp postregulators and two-stage conversion.

The new MRT however uses closed loop control of the main outputs, a single conversion stage and auxiliary channels employing high efficiency DC/DC postregulation.

All outputs are fully isolated from each other allowing them to be floated either positive or negative.

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 much lower losses, improving the efficiency.

The new topology allows the use of smaller value inductors and wound components.

A small output choke reduces losses, as does a ferrite boost choke wound with Litz wire.

Improvements in multilayer ceramic capacitors and functional organic polymer capacitors allows the implementation of much simpler inductorless filter circuits, again lowering losses, increasing efficiency and reducing size.

Finally, the use of silicon carbide Schottky diodes in the PFC circuit provides another 4% efficiency improvement.

High efficiency and low losses has meant that Lambda has not had to trade power for size.

The first two NV-Power units to be released are the NV-350 and the NV-175 and both boast class leading power densities: 6.6W/in3 for the sub-400W modular and 9.36W/in3 for the multiple-output sub-200W supplies.

NV-Power employs an 8bit microcontroller to handle housekeeping routines, replacing the array of comparators, op amps and other discrete components used in less integrated designs.

This brings a 50% parts count reduction, which in turn allows 40% more board space for power components.

The open construction of the new supply allows easy cooling, made even easier by the fact that the combined benefits of the MRT and MEG design has a 50% reduction in heat generation and that the heat is distributed evenly around the board.

Avoiding critical hotspots means heatsinks are eliminated, reducing weight and saving space.

NV-Power units require minimal airflow to achieve their nominal output ratings.

This reduced airflow means that a slower fan is used which is significantly quieter.

Lambda's patented soft switching MRT design has inherently low EMI emissions.

The silicon carbide Schottky diodes minimise EMI and the main power board's IMS (insulated metal substrate) does not rely on the chassis for cooling, reducing EMI still further.

The superior EMI performance of NV-Power enables it to achieve 601 medical compliance (with earth leakage current down to under 300uA) and meet EN55022 Curve B requirements with a typical 6dB margin which is unique for this class of product.

NV-Power is also very environmentally friendly.

It exceeds Energy Star guidelines for low power dissipation in operational mode, more than 50% better than some competitive products.

The new AC/DC supply has been designed to be a totally lead-free solution and to meet the RoHS directive.

"The NV-Power range marks a new beginning for AC/DC power supply design", concludes Southam.

"Its realisation has as much to do with listening to what our customers want, through our 'voice of the customer' research programme, as it does to the technical brilliance of our Ilfracombe UK design team".

"Our customers said they wanted 1U height compatibility, a narrow 95mm format in medium power ratings, low EMI, a quiet fan, low system airflow, powerful standby options, ease of connection.

NV-Power gives them all of that, and more.

The reduced size and thermal benefits simplify the host system design and allows customers to add extra functionality into their system whereas previously they were constrained.

We expect NV-Power to do very well in the instrumentation, broadcast and medical markets, and indeed all of those other areas, such as ATE, automation, routers and servers, storage systems and security networks, where there is a demand for power without compromise".

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