What is IEC 60601-1 and how does it relate to medical power supply units?

Power supply units (or PSUs) are subject to much more stringent regulation in the medical field than almost any other. Here's a short explanation of the applicable standards and a glance at new medical PSU from COSEL that qualifies under them.

 

EN/IEC 60601-1

Medical equipment is extremely highly regulated, for good reason. One of the most prominent standards is IEC 60601-1, first introduced in 1977 by the International Electrotechnical Commission (IEC). 

The series of standards covers safety and performance for electrical equipment in medical applications and are required before a device can be commercialized, especially in US markets where meeting the standard is a requirement under the FDA.

 

What Does MOPP Mean?

The third edition of the IE 60601-1 standard was published in 2005, which made a new distinction between a device's exposure to an "operator" vs. a patient. MOPP stands for Means of Patient Protection. It is a common initialism in the medical device space and compares to MOOP, Means of Operator Protection. 

Many of the PSUs available for medical applications are 2xMOPP, which is another form of MOPP classification that literally doubles the isolation, creepage, and insulation requirements for the PSU.

 

1x and 2x MOOP and MOPP classifications by requirement. Image from CUI

 

According to the standard, creepage and clearance are defined as follows:

  • Creepage is the shortest path between two conductive parts measured along the surface of the insulation.
  • Clearance is the shortest distance through air between two conductive parts.

As illustrated in the image below, 1x MOPP/MOOP and 2x MOPP/MOOP insulation are different in a circuit.

 

1x vs. 2x MOPP/MOOP insulation. Image from Meanwell via Mouser

 

Understandably, MOPP denotes a higher level of protection as it is exposed to a patient. 

 

COSEL's PCA300F and PCA1000F

The 300W PCA300F and 1000W PCA1000F are the newest members of Cosel’s PCA series. The units can be monitored and controlled via a built-in extended-UART (Universal Asynchronous Receiver –Transmitter) interface. Analog control of output voltage/current is possible without additional circuit design. A PMBus version is planned for Q4-2019.

 

Image courtesy of COSEL.

 

The devices work with inputs of  85 to 264 VAC, as well, 88 to 370 VDC. Separate units are available with 5, 12, 15, 24, 32 or 48 VDC outputs. Inrush current limiting, over-current protection, thermal protection, and output status alarm are all standard features.

Whether in constant voltage or constant current mode, all output voltages are adjustable down to near-zero volts. An isolated auxiliary voltage at 0.1 amps is also provided, independent of the main output.

Members of the PCA series can be connected in series or parallel for extra power, and in parallel redundant mode N+1 for improved system reliability and availability.

 

Analog and Digital Interfaces

The analog interface includes current adjustment (ITRM), voltage adjustment (VTRM), remote control ON/OFF, voltage sensing, LED alarms and current monitoring. The UART digital interface supports 83 commands for monitoring and control.

 

Block diagram for the PCA300F. Image from COSEL

 

The units can store operating data within local internal memory.

 

Around the Industry

There are many suppliers of medical grade power supplies.

TRACO Medical Power Supplies also offer PSUs that are IEC/EN/ES 60601-1 certified. Available power outputs include 5 watts to 9 watts and up to a 300-watt to 499-watt range.

Recom offers a wide range of medical power supplies adhering largely to the same protection standards. Outputs range up to 150 watts. They also offer a selection of medical grade DC to DC converters. On their webpage, they offer a concise tutorial explaining the ins and outs of medical power supplies and the standards the govern them.

 

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