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New AC/DC Power Supplies For Medical Applications Abstract:
are standards to apply to the endproduct in areas such as labelling, connectors, fusing and internal AC mains wiring. For example, if the AC supply cabling to the equipment features connectors, double fusing, in live and neutral, must be used.
Power supplies for medical applications are in great demand, especially with health crises sweeping the world. With more equipment needed for ventilators, analysers and life support in general, product designers must choose appropriate power supplies that meet the latest medical standards based on IEC 60601-1:2005 and its collateral documents. There are national variants: ANSI/AAMI ES 60601-1:2005 in the US, EN 60601-1:2006 in Europe and yet more round the world, all with local deviations. On the 20th August 2020, IEC 606011 amendment 2 was issued (IEC 60601-1:2005 +A1:2012 + A2:2020). This amendment updates out-of-date references to other standards, aligns the standard more closely with IEC 62368-1 (safety of audio/video, information and communication technology equipment), corrects errors and makes clarifications. Collateral electromagnetic disturbance standard IEC 606011-2 is at edition 4.
There are also considerations to be aware of with any EMI filter added Michael Schrutka, MSc. between a built-in power supply AC/DC Product Manager, RECOM and external connections. The medical EM disturbance standard, IEC 60601-1-2 4th edition, is more onerous than the previous edition, but care must be taken not to increase mains leakage current beyond the proscribed level for the application by applying additional EMI filtering. Even if an added filter claims medical leakage compliance to a certain level, this adds to any existing leakage current in the built-in power supply and may exceed the allowed limits. Ideally, a built-in AC/DC power supply should connect as directly as possible to the medical equipment power inlet with double fusing at that point and with no further EMI filtering. If the power supply holds the highest levels of medical certification and has good EMC compliance margin, there is then a high level of confidence that overall product safety and EMC performance is compliant. It has been possible to use non-medically certified power supplies in medical applications with some extra precautions; a power supply certified to standard IEC 62368-1 for example, with reinforced mains isolation, can be considered to have two measures of operator protection (2MOOP) suitable for lab testing environments with no patient contact. However, the new 4th edition EM disturbance requirements also apply
When specifying a built-in AC/DC power supply for a medical application, a product pre-certified to IEC/EN 60601-1 is a safe option. There are however still issues to consider, such as requirements for external fusing and possibly EMI filtering. This article discusses the requirements and introduces some available power supplies that make end product certification easier.
Using built-in medical power supplies
Medical equipment taking more than around 100W will normally have a built-in AC mains power supply rather than use an external adapter. This places obligations on the endproduct designer as there are now unsafe voltages and energy sources within his equipment. Although a built-in power supply can be medically certified, the whole end-product must also comply with electrical safety and EMC requirements so there
> MAY 2021
28
•Vol - 03 / 05
