Medical equipment power supplies in times of emergency

When demand for the supply of modular power supplies for medical equipment is high, the necessary certifications should not be overlooked so that patient and operator safety is maintained. This article summarises the product specifications that should be considered.

The outbreak of COVID-19 in January 2020 has disrupted the world economy, with some technology companies, particularly in China, temporarily closing their doors to avoid the infection risks associated with workers travelling and gathering together. Many have restarted their businesses as the risk at the outbreak epicentre diminishes, but supply chains for electronic components have been disrupted, with a knock-on effect around the world. Stock markets have suffered huge losses as companies, from phone manufacturers to airlines, see their profits at risk, but with hope for a rebound after some pause in the continuous demand for consumer goods and industrial output.

Medical equipment demand surges during medical emergencies

While we can all delay our next tech purchase or holiday and wait for stocks to recover, there is a more pressing problem: governments globally have been taking emergency action to contain the disease and make facilities available for screening, isolation and treatment of patients — and this requires medical equipment. We have seen the amazing speed at which China has built new hospitals — from empty lot to finished building within 10 days — with thousands of workers and masses of heavy construction equipment having achieved what seemed impossible.

Each new bed and theatre though needs a suite of diagnostic and therapeutic equipment to treat the patient effectively; screening points around the world at airports and other transport hubs need huge extra numbers of portable personal temperature monitors; even beds themselves today are expected to be ‘smart’ with patient status monitoring and motorised position adjustments. Medical equipment suppliers have been rushing to fulfil new orders to meet the demand, pulling in deliveries of necessary components, but this is the very supply chain that has been disrupted by the virus outbreak. Buyers have therefore, in some cases, had to look for equivalent 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 restating the requirements for one of the most safety-critical items in medical applications — the power supply.

Medical applications require medical-grade power supplies

Medical equipment can be powered from an AC mains or increasingly from an internal battery, and protection against electric shock is vital in both cases. It is often the case that domestic, commercial, industrial, IT and medical-grade AC/DC power supplies are available in a common form factor, for economy in manufacturing. Outwardly they can look identical and headline performance specifications for input and output ratings can be the same, with most categories of end-equipment possibly functioning as expected with a power supply intended for another category. The difference is in safety specifications however; medical-grade power supplies have particular characteristics that match the sensitive healthcare environment where monitoring equipment may be directly applied to the body of a patient, who may already be weak and susceptible to further injury.

A medical-grade AC/DC converter in a 5″ x 3″ industry-standard housing.

Categories of medical environment must be identified

The latest medical standards for safety consider different healthcare environments: Type B (body), where equipment has no direct connection to the patient, such as lighting in operating theatres or analysis equipment in laboratories; Type BF (body float), where the equipment has direct patient connection such as with incubators, beds with electronic controls or ultrasonic diagnostic equipment; and Type CF (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 (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 fourth and latest edition 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.

DC/DC converters may need medical certification as well

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 3 kVDC, 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 250 VAC, 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.

An ECG monitor requiring a medically certified DC/DC converter (RECOM REC3 and RP series).

Certified power supplies are available

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 worldwide 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 its main manufacturing site in Taiwan, with sites in Italy and China fully operational.

Top image credit: ©stock.adobe.com/au/beerkoff

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