Compact medical and industrial power supplies have cooling options

AC/DC power supplies by TDK-Lambda in the 250W CUS250M series have a footprint of 2.0 x 4.0 (50 x 100mm). The series is certified to both IEC 60601-1 and IEC 62368-1 standards for both Class I and Class II (double insulated) installations, making them suitable for medical, home healthcare, dental, test and measurement, broadcast, professional audio and industrial equipment.

Conduction and convection cooling enables silent operation, said TDK-Lamba and the CUS250M can deliver up to 250W in -20 to +50 degrees C ambient temperatures. Operation at +80 degrees C is also possible with appropriate derating. With one metre per second forced air cooling using system airflow or the optional integral fan, the U channel models can deliver 250W in a +50 degree C ambient, derating to 125W at +70 degrees C, reported the company. Options for the CUS250M include a 5V 0.1A standby voltage, remote on/off, DC OK and AC fail signals. The supplies are available in U channel, U channel with cover or top mounted fan mechanical construction.

Initially, 12 and 24V models will be available, with 15, 18, 28, 36 and 48V outputs to follow. The output voltage can be adjusted by the user. The series accepts an 85 to 264V AC input and earth leakage current is less than 150 microA – including all tolerances. Touch current is less than 10 microA (Class I) and less than 70 microA (Class II).

With efficiencies up to 94 per cent, less internal heat is generated allowing reliable operation, explained TDK-Lambda. Average efficiency, measured at 25, 50, 75 and 100 per cent loads, is greater than 91 per cent. Offload power consumption is less than 0.5W when the output is inhibited.

Design features include the use of polymer output capacitors, providing low ESR and high ripple current tolerance to maximise field life. The high-voltage bulk capacitor, used to store energy during short interruptions in AC power, is located at the edge of the power supply PCB to enable more effective cooling for both convection and forced air applications. The layout of the components on the underside of the PCB distributes heat evenly across the base, improving thermal transmission. A patent pending output terminal / choke combination reduces common mode noise.

The CUS250M has an input to output isolation of 4,000V AC (2 x MoPP or means of patient protection), an input to ground isolation of 1,500V AC (1 x MoPP) and an output to ground isolation of 1,500V AC (1 x MoPP) for B (body) and BF (body floating) -rated medical equipment. 

The series is certified to IEC / EN 60601-1, ES 60601-1. IEC / EN / CSA / UL 62368-1 and is CE / UKCA marked to the Low Voltage, EMC and RoHS Directives. All models in the series meet EN 55011-B, EN 55032-B radiated and conducted emissions with significant margins (both Class I and Class II) and comply with the EN 60601-1-2:2015 (Edition 4) and EN 61000-4 immunity standards.

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