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DIGITAL CONTROL POWER SUPPLIES FROM TDK-LAMBDA

Posted : 27 Oct 2008

TDK-Lambda has extended its revolutionary digital power supply technology to include a new range of models designed specifically with medical applications in mind. With 4kVAC, reinforced input to output isolation, and other specifications such as and O/P to ground isolation of 1500VAC, the EFE300M meets the rigorous international safety standards for medical equipment, making it suitable for use in B and BF type medical applications.

With a 152mm x 76mm footprint and a 1U profile, the EFE300M can be incorporated easily in designs where space is limited, so end equipment can be smaller, cooler and more feature rich. Other features such as redundant operation capability and a high current standby output make the EFE300M equally suitable for high integrity applications including broadcast, instrumentation, routers, servers and security networks. Other suitable applications include ATE and automation,

As with the EFE300, the EFE300M includes an integrated magnetics transformer to boost efficiency to typically 90%, and employs an 8-bit microcontroller for full digital control of the output and to handle housekeeping routines. This brings a 25% parts count reduction to achieve a 45% smaller and up to 56% lighter design when compared to similar recently announced competitive products. Power densities of up to 16.6W/in3 are achieved under peak load conditions and 12.5W/in3 under continuous loading.

TDK-Lambda’s control of the EFE300M allows the power supply’s performance, such as current limit and start-up characteristics, to be optimised digitally – this feature eliminates the hardware changes usually required in analogue designs. A low cost primary side control topology is used, supervised by the microcontroller. This results in fewer parts and higher efficiency without sacrificing load regulation performance. Furthermore, the need for an optoisolator is eliminated – a device which is undesirable for long life power supply designs.

Additional features of the EFE300M include remote on/off and power good signals; it also comes with a 5V / 2A isolated standby supply, which is not affected by the remote on/off. The inclusion of an ORing FET allows redundant connection of the EFE300M supplies with no additional diode required. Output regulation is better than 4% and, since the microcontroller is used to digitally predict the output voltage, the line and load regulation can be changed or fine tuned precisely – this is particularly useful when droop paralleling.

The EFE300M delivers 300W continuous power (400W peak for 10 seconds) with nominal outputs of 12V / 25A or 24V / 12.5A. However, non-standard system voltages can be accommodated easily by precise factory programming. An additional 12V / 1A fan supply is also included and all models operate from 90 - 264VAC input with dual fusing as standard. Earth leakage current is better than 300µA fully complying with medical safety requirements. Active power factor correction ensures EN61000-3-2 compliance. Other EMC improving design features, such as the use of SiC diodes, ensure curve B EMC performance with a significant margin.

TDK-Lambda’s EFE300M is approved to IEC/EN/UL/CSA 60950-1 for general purpose applications, IEC/EN 61010-1 for laboratory and process control applications and IEC 60601-1 for medical equipment. In addition, the unit carries the CE mark according to the LV Directive and comes with a three-year warranty.

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