TDK Corporation (TSE:6762) announces the introduction of the 250W rated TDK-Lambda brand CUS250M series of power supplies in the industry standard 2” x 4” footprint. The product’s mechanical configurations enables both convection and conduction cooling through the product’s baseplate to provide silent cooling. The CUS250M is certified to the 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.
Initially, 12V and 24V output voltages are available, with 15V, 18V, 28V, 36V and 48V models later. The output can be adjusted to accommodate non-standard voltages. The CUS250M operates from an 85 to 264Vac input and has a low earth leakage current of less than 150µA - including all tolerances. Touch current is <10µA (Class I) and <70µA (Class II).
The CUS250M can provide up to 250W 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 1m/s external airflow, or the optional integral fan, enables an output power of up to 125W at +70°C. This is possible as the power supplies have efficiencies up to 94%, generating less internal heat. Average efficiency, measured at 25, 50, 75 and 100% loads, is greater than 91%. Offload power consumption is less than 0.5W when the output is inhibited.
Options for the CUS250M include a 5V 0.1A standby voltage, remote on/off (inhibit or enable), DC OK and AC Fail signals and a choice of open frame, U channel, U channel with cover or top mounted fan mechanical constructions.
The product has been 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, again 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 4,000Vac (2 x MoPP), input to ground isolation 1,500Vac (1 x MoPP) and the output to ground isolation is 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 CUS250M is compliant to 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 the EN 60601-1-2:2015 (Edition 4) and EN 61000-4 immunity standards.
More information on the CUS250M series, including distributor inventory, can be obtained from the TDK-Lambda Americas website at
