Power supplies designed for medical applications

TDK-Lambda has extended its digital power supply technology to include a range of models designed specifically with medical applications in mind.

With 4kV AC, reinforced input to output isolation, and other specifications such as O/P to ground isolation of 1,500V AC, the EFE300M meets the 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 in designs where space is limited.

Other features, such as redundant operation capability and a high current standby output, make the EFE300M suitable for high integrity applications including broadcast, instrumentation, routers, servers and security networks.

As with the EFE300, the EFE300M includes an integrated magnetics transformer to boost efficiency to typically 90 per cent, and uses an 8-bit microcontroller for full digital control of the output and to handle housekeeping routines.

This brings a 25 per cent parts count reduction to achieve a 45 per cent smaller and up to 56 per cent lighter design when compared to similar 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, which eliminates the hardware changes required in analogue designs.

A primary side control topology is used, supervised by the microcontroller.

This results in fewer parts and higher efficiency without sacrificing load regulation performance.

The need for an optoisolator is eliminated - a device that is undesirable for long-life power supply designs.

The EFE300M includes remote on/off and power good signals and comes with a 5V/2A isolated standby supply.

The inclusion of an o-ring FET allows redundant connection of the EFE300M supplies with no additional diode required.

Output regulation is better than 4 per cent and, since the microcontroller is used to digitally predict the output voltage, the line and load regulation can be changed or fine tuned precisely.

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 by precise factory programming.

An additional 12V/1A fan supply is also included and all models operate from 90-264V AC input with dual fusing as standard.

Earth leakage current is better than 300uA 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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