Meeting medical application requirements for displays and power supplies

Author : Peter Lappin, Managing Director at Relec Electronics

06 November 2018

Relec Electronics's medtech equipment

Medical technology is evolving fast and most modern medical devices feature integrated electronics. Electronic devices typically require a power supply, and display technology usually forms the dominant interface. But medtech devices often have more demanding and specific requirements than other applications – and as this piece outlines, working with suppliers who understand these requirements usually makes the design process run more smoothly.

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Suppliers with experience of serving medical industry applications usually have greater awareness of its specific needs, often driven by standards compliance requirements – and are typically better equipped to deliver products that meet them. A specialist power conversion and display technology distributor, Relec Electronics has considerable expertise in providing solutions that are well suited to medical applications – either by ensuring the components meet relevant industry standards, or by customising them to match the requirements.

Powering medtech devices

Medical power supplies differentiate themselves from standard AC-DC converters by virtue of having very low leakage currents. At the heart of any product designed for the medical industry, there will be a power supply that needs to meet the requirements of EN60601 – a standard that has been around for over 40 years! All of the medical power supplies provided by Relec Electronics meet relevant standards, including the globally recognised EN60601-1 and UL60601-1.

Whilst the EN60601 directive does not specifically cover power supplies, this article reviews the relevance of this standard to a range of medical applications, which will help design engineers source the right solution.

Safety and isolation

Medical electronics are inherently either connected directly to the patient or operator, or will be located nearby. Accordingly, EN60601 defines the protection required for both the patient and operator. A patient may be connected to a piece of diagnostic equipment by probes, while operators have access to control panels, and the risks associated with faults in this area.

EN60601 2nd edition defined three categories of usage:

Type B (body). This is typically equipment that may be in a clinical area, but is not directly connected to the patient. These might include beds, lighting, scanners and X-ray machines.

Type BF (body floating). Medical equipment that is directly connected to the patient. These may include ultrasound, blood pressure monitors and thermometers.

Type CF (cardiac floating). Equipment that is directly connected to the heart, such as defibrillators and dialysis machines.

EN60601 3rd edition took this concept further and looked at the management of risk within a product. To manage these risks, products must offer multiple ‘means of protection’ (MOP), and these are further broken down into two categories:

• Means of operator protection (MOOP) – Products controlled by a technician. As a rule, MOOP has the same requirements as EN60950. However, it is essential to assess the risk that there can be no possible contact with the patient.

• Means of patient protection (MOPP) – Products directly connected to a patient.

All new medical equipment should have at least two appropriate MOPs. These can be safety insulation (defined by creepage and clearance distances), or protective earthing – or a combination of the two. Where protective earthing is used, designers must be aware of the constraints on leakage currents, especially on patient-connected equipment.

Relec Electronics offer a wide range of products that meet the requirements of multiple MOPPs and MOOPs, and which also meet the latest requirements for EMC standards (which will become an integral part of EN60601 4th edition).

Its portfolio includes a broad range of power supplies and DC-DC converters:

External power supplies

An extensive range of plug-top and desktop designs, starting at 5W through to 300W. These products are also classified to CEC Level VI, making them suitable for export to the US market. These external power supplies typically meet the requirements of 1xMOPP.

Credit: Shutterstock

Embedded AC-DC converters

This range includes open frame and enclosed power supplies offering 2xMOPP as standard. Power ranges from 40 Watts to 1800 Watts, in single and multioutput configurations. Relec can also now offer products that can be accurately controlled via PMBus.

DC-DC converters

1 Watt to 6 Watt converters offering 6000V DC isolation (2xMOPP) are a simple way to power sensors and actuators which may be connected directly to the patient.

Display technology for medical applications: where standards are not enough!

Standard TFT display products are available from Relec in a wide range of sizes, from small 1.77" up to 12.1". These cover all industry standard resolutions, sizes and interfaces. Standard units are available with brightness levels that exceed 1500 cd/m².

However, if the display is to be used in medical applications, it is important that advice is taken from qualified and experienced suppliers. Relec offers a range of enhancements that improve the optical, mechanical and environmental performance of the display, making it especially suitable for medical applications.

Anti-bacterial treatments

The anti-bacterial (AB) surface treatment is a coating that is applied to the cover glass.

Nano-silver technology is widely used in medical applications, and when combined with an SiO2 layer, it breaks down the bacterial cell wall, reducing bacteria reproduction by 99.999%. The AB coating has no effect on any optical characteristics of the display, nor does it affect sensitivity when used with touch panels. Popular applications of this surface treatment include heart monitors, dialysis machines and reception kiosks.

Anti-glare treatments

The anti-glare (AG) surface treatment is a cost-effective solution to reduce glare and any unwanted reflections. This may be especially important if equipment is used outdoors or even in an operating theatre environment. In normal circumstances, light reflects in a predictable way – be it specular or diffused.

Once light strikes an AG coated display, it is dispersed in different directions, effectively reducing glare. The AG coating has no effect on optical characteristics or sensitivity when used with touch panels.

Anti-fingerprint treatments

Anti-fingerprint (AF) surface treatments reduce fingerprint marking when users directly handle the display. This is most commonly combined with touch panels. The AF treatment is a spray coating that is applied to the front of the module, using fluoride nano-molecules within the coating. This isolates any natural oil on a person’s finger, greatly reducing the transfer of fingerprints to the display, making it clearer and reducing the possibility of reading errors.

Glove touch – touch panels

Relec also offers a range of integrated PCAP touch panels that can be used with a variety of gloves, ranging from simple latex, right through to Nuclear bio-medical. The high signal-to-noise ratio of Relec’s touch panels means systems can be tuned specifically to customer requirements.

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