Medical Equipment Power Supplies in Times of Emergency

The grave situation of the outbreak of COVID-19 in January 2020, the ‘corona virus’, has disrupted the world economy with many technology companies, particularly in China, closing their doors to avoid the infection risks associated with workers travelling and gathering together. Many have now re-started their businesses, as the risk at the epicentre of the outbreak diminishes, but supply chains for electronic components have been disrupted - with a knock-on effect round the world. Stock markets have suffered huge losses as companies, from cell-phone manufacturers to airlines, have seen their profits slide.

While we can all delay our next ‘hi-tech’ purchase, reconsider travel plans or wait for technology stocks to recover, there is a more pressing problem for governments and health authorities who have been taking emergency action to contain the disease and make facilities available for the screening, isolation and treatment of those affected. We have seen the amazing speed at which China has built new hospitals – from an empty lot to finished building within ten days; thousands of workers and masses of heavy construction equipment working together to achieve what seemed to be impossible. But this is only the physical infrastructure; each new ward and theatre needs a suite of diagnostic and therapeutic equipment to treat the patients effectively; even hospital beds themselves today are expected to be ‘smart’ with patient status monitoring and motorised position adjustments to relieve the stress on the overworked care staff. Outside of China, screening points around the world at airports and other transport hubs need extra numbers of portable personal temperature monitors to monitor the travelling public for the disease.

Medical equipment suppliers have been rushing to fulfil a raft of new orders to meet the emergency, ‘pulling-in’ deliveries and accelerating production, but this is happening at the very time that the components supply chain that has been disrupted by the virus outbreak itself. Buyers have therefore, in some cases, had to look for alternate parts from a wider supplier base. Certified medical equipment manufacturers are well aware of the necessity to maintain their product quality and safety and cannot ‘cut corners’, but in times of emergency it is worthwhile re-stating the requirements for one of the most safety-critical items in medical applications - the power supply.

The latest medical standards for safety consider different healthcare environments: where equipment has no direct connection to the patient such as lighting in operating theatres or analysis equipment in laboratories, Type B (body) and areas where the equipment has direct patient connection such as with incubators, beds with electronic controls or ultrasonic diagnostic equipment, Type BF (body float). A further category is CF or ‘cardiac float’ where there is direct connection to the patient’s heart such as in defibrillators. For Type B applications an AC/DC power supply must be certified for 2 x MOOP or ‘Two Measures of Operator Protection’. For Type BF and CF, the certification is 2 x MOPP or Two Measures of Patient Protection with a further very stringent limit to mains leakage current in the CF case.

Power supplies meeting these requirements have very specific insulation systems with minimum creepage and clearance distances between live and output connections and controlled maximum mains leakage current – the current that could flow from the AC supply to the output or casing of the equipment and on to an operator or patient under normal or single fault conditions. The latest ‘edition 4’ of the medical safety standard ES/IEC/EN 60601-1 also has more stringent EMC requirements compared with its predecessor and other application environments. In some cases, the power supply output may need guaranteed isolation from ground and there are further considerations if there are other connections to the power supply or end-equipment such as communications links.

It may not be obvious, but in medical applications, DC/DC converters with low input and output voltages may also need safety certification. Often, a DC/DC is used to ‘add’ a level of safety isolation to a lower grade AC/DC to achieve a higher overall grade. This can enable a lower cost 2 x MOOP AC/DC to be used in a 2 x MOPP application, as long as the DC/DC has the required insulation grade and creepage/clearance. DC/DCs in battery-powered equipment may also form a safety barrier when the equipment is being charged from AC mains or when a communications link is connected, to a grounded laptop for example.

In this case the DC/DC is preventing lethal current flow from other faulty equipment through the patient and through the battery powered equipment and on to ground through the laptop. Modular DC/DCs are often advertised with high test-voltage levels, perhaps 3kVDC, but this is not necessarily sufficient and may only be a measure of immunity to transients, not safety isolation. For medical applications, the DC/DC must have the correct, certified, 1 x or 2 x MOOP or MOPP according to the equipment configuration, connections and environment. Unlike AC/DCs which can be expected to be rated for measures of protection for typical highest AC mains voltages, perhaps 250VAC, DC/DCs can be offered with MOPs for lower system voltages, which may not be sufficient in the application. Close examination of the data sheet is necessary.

When selecting a medical grade AC/DC or DC/DC power supply, the decision should be taken with care, despite the urgency. Austria-based manufacturer RECOM has a wide selection of medically certified AC/DC and DC/DC converter products and can advise on their compatibility with any particular application. RECOM has an extensive world-wide distribution network with high inventory levels to meet potential surges in demand and does not anticipate major effects on delivery times or product availability due to events such as the COVID-19 virus outbreak. As of March 2020, RECOM is in full production with good component stocks in their main manufacturing site in Taiwan and our delivery times remain stable.


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