Built-in Medical Power Supplies – Finally a Solution!

Ulrich Schlienz, retired professor and author of the book Schaltnetzteile und ihre Pe-ripherie


Developers need to know how long a medical power supply will work safely without maintenance

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Figure 1: Efficiency vs. load

Every developer looks forward to the moment when he knows that his prototype is finally working, all key functions have been realised and the software is fully implemented except for the diagnostic functions. At the next meeting, he proudly announces that all that is needed at this stage is the EMC approval and a suitable power supply. However, given the limited resources, designing a power supply in-house is not an option, as crucial deadlines would be missed. The team thus agrees to go for a third-party product, and the developer starts looking for a power supply.

Although there is no shortage of such products in the market, identifying the right components proves often more tricky than first thought. In our example, the product must conform to standard X, protection class Y, and even 2MOPP, as it has been decided that the power supply is also to be used in a recently launched ventilator. On top of all that, the developer also needs to consider the MTBF rate. Just image if a patient is connected to a ventilator – and the power supply suddenly fails! This must of course be prevented at all cost! So, the developer needs to know how long a power supply works safely without maintenance.

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Figure 2: Power factor

RECOM has designed the RACM1200-V with “the safest option is the only option” philosophy, and the power supply comes with all the necessary approval certificates.

The RACM1200-V is compact and covers a wide power range for reliable fan-less operation. A special base plate ensures effective heat dissipation for up to 1000W continuous output power. The RACM1200-V comes with two additional outputs so that there is no need for additional power supplies as would otherwise be the case for certain applications. It features an adjustable 12V system fan output and a 5V/1A standby output.

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Figure 3: Remote sense for main output voltage

Thanks to a high insulation strength of 4kVAC between the mains voltage and the output voltages, the RACM1200-V can be used in virtually all areas where a power supply is required, such as chargers, LED lighting systems, laser equipment, analytical instruments, high-frequency devices, robots, medical beds and chairs as well as medical technical devices with direct patient contact.

While the RACM1200-V is certified according to IEC 60601-1, it does of course not guarantee that the device into which it is to be integrated also meets this standard. However, using a certified power supply is one of the preconditions for compliance, and certainly speeds up the certification process for the end product, while reducing development costs.

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Figure 4: The RACMxx series of power supplies for medical technical applications (from left): 230W, 550W and 1200W

The RACM1200-V provides certified 2MOPP (MOPP = Means of Patient Protection) insulation and minimum leakage current, which means that it conforms to the patient safety standards that apply to medical technical equipment. The signal outputs and the 5V output also come with 1.5kVAC insulation to the mains voltage.

The RACM1200-V series features an integrated EMC filter that easily meets the requirements of EN 55032:2015 Class B for radiated and line-bound interference. It conforms to all relevant international safety standards for industrial applications, IT products and medical technical equipment.

The input voltage range is 85VAC to 264VAC. The RACM1200-V allows for up to 1000W continuous output. It features a 40mm high metal housing with contact cooling and a footprint of only 102mm x 229mm. For up to 10 seconds, the output power might even be 1200W. For 1200W continuous output, the power supply must however be equipped with a fan that ensures and air flow of 2.5m/s through the unit. The RACM1200-V is fitted with a controllable auxiliary output to accommodate temperature management.

Key data of RACM1200-V

  • Output power: 1000W at 40°C ambient temperature and 230V input voltage; 1200W with fan or for short peak loads.
  • Dimensions including connectors (L x W x H): 228.0mm x 96.2mm x 40.0mm; in products from other suppliers, the connection part is exposed to mechanical impact.
  • Efficiency: 95%, see Figure 1.
  • Power factor: See Figure 2.
  • Weight: 1kg (typical)
  • Input voltage: 85V to 264V
  • Output voltages:
  • The 24V type can be adjusted by means of a DIP switch in steps of 100mV to maximum 28V.
  • The 48V type can be adjusted by means of a DIP switch in steps of 200mV to maximum 56V.

·        Maximum output current: 50A@24V, 25A@48V.

·        Protection functions for main output and auxiliary voltages:

·        Overload protection, automatic reset

·        Overcurrent and short-current protection, automatic reset

·        Overtemperature protection, automatic restart

·        Temperature range: -40°C to 80°C, derating from 50°C; see data sheet

·        Service life at ambient temperature 40°C: 88,000 hours

·        Max. output voltage ripple: 1% of output voltage

·        Output voltage tolerance: 1% typ.@25°C, +- 2% max. at higher temperature

·       Certified according to: IEC/EN 62368, UL/IEC/EN 60601

·       Conforming to IEC/EN 61558-2-16, IEC61010-1, and OVC III according to IEC62477-1 up to 2000m

  • Cooling by aluminium baseplate or forced airflow.
  • Max. operating altitude: 5000m (IEC/EN62368-1) 4000m (IEC/EN60601)

·        Auxiliary output voltage: 5V/1A, insulated

·        Standby power consumption: < 1W (EcoDesign)

·        LED operating status indicators: user-friendly and offering extra safety

·        Remote on/off: TTL input

·        AC OK: Open Collector Output

·        PSU-good: Open Collector Output

·        PSU good: Open Collector Output Pin, Power Supply Unit working, output voltage OK, temperature within permissible range, no internal faults. For extra safety, reliability and power quality.

·       Maximum patient leakage current: 100μA NC (normal condition) and 500 μA SFC (single fault condition)

·       Medical safety classification: 2MOPP

·        Precision-controlled output voltage: To eliminate voltage dips in lines, the power supply comes with remote main-output voltage sensing whereby two additional (sense) lines measure and control the output voltage at the relevant point. This solution eliminates voltage dips in high-current (25A/50A) lines. Activation through 2 TTL inputs (5V).