Medical and industrial power supplies can be conduction or convection cooled

TDK Corporation has introduced the compact 250W rated TDK-Lambda brand 2” x 4” footprint CUS250M series of AC-DC power supplies. The series is certified to IEC 60601-1 and IEC 62368-1 standards for Class I and Class II (double insulated) installations.

Conduction and convection cooling provides silent operation, and the CUS250M can supply up to 250W in -20C to +50C ambient temperatures. Operation at +80C is also possible with suitable derating. With 1m/s forced air-cooling using system airflow or the optional integral fan, the U channel models can supply 250W in a +50C ambient, derating to 125W at +70C. Options for the CUS250M include a 5V 0.1A standby voltage, remote on/off, DC OK and AC Fail signals, and a selection of U channel, U channel with cover or top-mounted fan mechanical construction.

12V and 24V models will be offered initially, with 15V, 18V, 28V, 36V and 48V outputs following later. The user can modify the output voltage. The series takes an 85VAC to 264VAC input, and the earth leakage current is lower than 150µA - including all tolerances. Touch current is <10µA (Class I) and <70µA (Class II).

With efficiencies up to 94%, less internal heat is generated, enabling reliable operation. Average efficiency, measured at 25, 50, 75 and 100% loads, is greater than 91%. Offload power consumption is lower than 0.5W when the output is inhibited.

Design elements include polymer output capacitors, delivering low ESR and high ripple current tolerance to maximise field life. The high-voltage bulk capacitor, utilised to store energy throughout short interruptions in AC power, is situated at the edge of the power supply PCB. This and the component layout enable more effective cooling for both convection and forced air applications, enhancing reliability. Careful component layout on the underside of the PCB distributes heat evenly over the base, enhancing thermal transmission. A unique output terminal/choke combination (patent pending) lowers common-mode noise.

The CUS250M has an input to output isolation of 4,000VAC (2 x MoPP), an input to ground isolation of 1,500VAC (1 x MoPP) and an output to ground isolation of 1,500VAC (1 x MoPP) for suitability in B and BF rated medical equipment. Safety certification is 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. The models meet EN 55011-B, EN 55032-B radiated and conducted emissions with significant margins (Class I and Class II) and comply with the EN 60601-1-2:2015 (Edition 4) and EN 61000-4 immunity standards.

Typical applications include test and measurement, medical, home healthcare, dental, broadcast, professional audio and industrial equipment.