CUS250M Series 2” x 4” 250 W Power Supplies

TDK-Lambda’s CUS250M series 2” x 4” 250 W power supplies have a mechanical configuration that enables both convection and conduction cooling through the baseplate to provide silent cooling. The series is certified to industrial IEC 62368-1 and medical IEC 60601-1 standards for both Class I and Class II (no earth ground required) installations. Applications include medical, home healthcare, dental, test, measurement, broadcast, professional audio, and industrial equipment.

The CUS250M series is available in 12 V and 24 V output voltages. The output can be adjusted to accommodate non-standard voltages. The CUS250M operates from an 85 V_AC to 264 V_AC input and has a low earth leakage current of less than 150 µA, including all tolerances. The touch current is <10 µA (Class I) and <70 µA (Class II).

The CUS250M can provide up to 250 W in -20°C to +50°C ambient temperatures when conduction cooled without external air. Operation at up to +80°C is also possible with appropriate derating. Utilizing 1 m/s external airflow or the optional integral fan enables an output power of up to 125 W at +70°C possible because the power supplies have efficiencies up to 94%, generating less internal heat. The average efficiency, measured at 25%, 50%, 75%, and 100% loads, is greater than 91%, and the offload power consumption is less than 0.5 W when the output is inhibited.

Options for the CUS250M include a 5 V 0.1 A standby voltage, remote on/off (inhibit or enable), DC OK and AC fail signals, and choice of open frame, U channel, U channel with cover, or top mounted fan mechanical constructions.

The product is designed to minimize electrolytic capacitor heat degradation. Polymer output capacitors are used, providing low ESR and high ripple current tolerance. The high-voltage bulk storage capacitor is situated on the edge of the PCB for minimum heat rise. Component layout enables more effective cooling for both convection and forced air applications, enhancing reliability and field life. Careful component layout on the underside of the PCB distributes heat evenly across the base, improving thermal transmission. A unique output terminal/choke combination (patent pending) reduces common mode output noise.

The input-to-output isolation is 4,000 V_AC (2xMOPP), input-to-ground isolation 1,500 V_AC (1xMoPP), and the output-to-ground isolation is 1,500 V_AC (1xMOPP) for suitability in B and BF rated medical equipment. Safety certification is to IEC/EN 60601-1, ES 60601-1, and IEC/EN/CSA/UL 62368-1, and is CE/UKCA marked to the Low Voltage, EMC, and RoHS directives. The CUS250M is compliant with IEC/EN 60335-1 and IEC/EN 61010-1. The series meets EN 55011-B, EN 55032-B radiated and conducted emissions with significant margins (both Class I and Class II) and complies with EN 60601-1-2:2015 (Edition 4) and EN 61000-4 immunity standards.