Medical Devices Require 'Do No Harm' Power Supplies

The pace of innovation in powered medical devices is breathtaking and likely to increase with the integration of artificial intelligence. The constant demand for improvements in the diagnosis, monitoring, and treatment of medical issues has created an eye-opening market projected at more than $542 billion in 2024.

But the growing complexity of these devices can make it challenging to source the power supplies and adapters that meet the specific needs of each application. Additionally, those developing applications in this area must adhere to strict medical-grade standards and regulatory requirements.

Whereas less regulated markets often reward vendors with a high-risk tolerance and the ability to shorten time to market, medical devices must minimize risk, undergo rigorous testing and quality control processes, follow regulations that influence all phases of the development process, and demonstrably improve patient outcomes.

Just as the medical adage dictates doctors “first, do no harm,” medical applications must foremost be safe. In that regard, devices must adhere both to “means of patient protection” (MOPP) and “means of operator protection” (MOOP) to safeguard practitioners and technicians, as well as their patients.

The scope of IEC 60601-1

The IEC 60601-1 standard represents the compliance bible for power supplies used in medical devices. The 40-year-old standard is now in its third edition, revision two (60601-1, 3.2), and spans a broad array of device categories, from home health to cardiac care. It has already been adopted in the U.S. and is in various stages of adoption in other regions.

The standard establishes requirements for isolation between AC input and DC output, allowable current leakage, and insulation. A 1x MOOP protection level for operators requires a basic layer of insulation, the ability to withstand an isolation test at 1,500 V_AC, and creepage distance between conductive parts of at least 2.5 mm; 2x MOOP protection mandates double insulation and doubles the isolation and creepage requirements.

For patients, the requirements vary somewhat: 1x MOPP also requires a basic layer of insulation and isolation of 1,500 V_AC, but creepage distance increases to 4 mm; 2x MOPP doubles the creepage and insulation requirements, while also increasing isolation to 4,000 V_AC.

Low leakage is unsurprisingly critical to medical-grade devices, as current can cause potentially deadly harm, whether from earth leakage, enclosure leakage, or that which flows through a patient in direct contact to an applied part or parts.

Applied parts are designated in three classifications:

• Type B, a basic level for equipment such as a medical bed ventilator, where there is no electrical contact with the patient
• Type BF, a stricter classification for applications including ultrasound and electrocardiogram (ECG) imaging, where electrical contact with the patient may occur, but does not provide invasive connection to the cardiovascular system
• Type CG, the strictest classification covering devices that may be in direct contact with the patient's cardiovascular system, such as electro-surgical knives and pacemakers

Vendors must also be aware of the collateral standard, IEC 60601-1-2, regarding electromagnetic compatibility in the presence of external electromagnetic disturbances and to those disturbances emitted by the medical device.

For those creating home healthcare applications, IEC 60601-1-11 sets additional safety requirements reflecting the challenges and risks of using medical-grade applications in non-clinical environments (including out-of-home use). This standard delineates Class I applications that are permanently installed in homes by licensed electricians from Class II applications that do not rely on earth grounding.

Navigating device approvals

In the U.S., the Food and Drug Administration is charged with ensuring that medical devices follow established development paths to guarantee that they are safe and effective. That agency established a three-tier classification system for medical devices based on risk:

• Class 1 devices pose the least amount of risk, ranging from tongue depressors to oxygen masks and surgical tools, that are subject to general controls including good manufacturing processes, standards and reporting of adverse events, product registration, and general recordkeeping.
• Class 2 devices are those with a higher degree of risk, such as blood glucose monitors, subject to additional controls, including product labeling requirements, device-specific mandatory performance standards, and device-specific testing requirements. Developers may submit premarket notifications claiming that a new device is comparable to one or more similar devices that are already legally marketed.
• Class 3 devices are those that support or sustain life, are implanted, or have potential for unreasonable risk of illness or injury, such as pacemakers, defibrillators, transfusion devices, and powered wheelchairs. Because of the higher risk, manufacturers must comply with premarket approval processes aimed at proving safety and efficacy, including submission of clinical and non-clinal studies, inspection of manufacturing facilities and labs.

The FDA also provides “De Novo” approval for devices that have never been marketed in the U.S. but have safety profiles and technologies that are reasonably well understood. Devices intended to benefit patients for diagnosis or treatment of diseases or conditions manifested in fewer than 4,000 patients per year may also be granted Humanitarian Device Exemptions.

Following approvals, the FDA continues to monitor device performance for new safety concerns. This can include inspection of manufacturing facilities and programs that allow manufacturers, health professionals, and consumers to report problems with previously approved devices.

Going to market

Navigating U.S. and international regulatory requirements is not a casual affair. Taking advantage of power supplies that demonstrably comply with the latest standards and regulations can ease the path to market.

MEAN WELL, founded in 1982, offers a comprehensive portfolio of medical-grade power supplies certified to the latest IEC60601-1 safety standards. They are suited to a range of applications, including diagnostic and treatment analysis, laboratory equipment, home healthcare devices, and rehabilitation and assistive devices.

BF-rated with 2x MOPP or MOOP isolation levels, the entire medical power supplies portfolio complies with the broad range of international safety regulations: UL, CUL, TUV, CB, CE, and FCC. They are equipped with higher levels of insulation and provide superior EMC performance, high reliability, and an extended life cycle.

Of particular interest to vendors targeting global markets, the company's NGE series of wall-mounted interchangeable AC adapters for medical, consumer, and industrial applications are available in outputs of 12 W to 90 W with a choice of fixed U.S. plug, fixed EU plug, or interchangeable AC plugs with global certifications.

The 90 W NGE90U18-P1J for the U.S. comes with a fixed blade input and a barrel plug output connector. It works with an input range of 80 V_AC ~ 264 V_AC and delivers an 18 V output with a working efficiency up to 92%. Its international market counterpart, the NGE90I18-P1J, includes an international multi-blade attachment (Figure 1). Multi-blade attachments for other models in the NGE series are sold separately.

Figure 1: The international version of MEAN WELL’s NGE90 AC adapter with interchangeable plugs for multiple markets. (Image source: MEAN WELL)

MEAN WELL also offers its GSM series of highly energy-efficient external medical power adaptors in a desktop style with both IEC320-C14 (A Type) and IEC320-C8 (B Type) AC input connections, as well as wall-mounted versions with a fixed U.S. plug, a EU plug, or an interchangeable AC plug. Both desktop and wall-mount types are available in 5 V, 7.5 V, 9 V, 12 V, 15 V, 18 V, 19 V, 20 V, 24 V, and 48 V versions.

The company’s 500 W RPS series of built-in, PCB type AC/DC medical-grade power supplies are available in various compact sizes, including common sizes such as 3” x 2”, 4” x 2”, and 5” x 3”. These models feature an 80 ~ 264 V_AC input and have output voltage options from 12 V to 48 V. The 48 V RPS-500-48-C (Figure 2, left) comes in an enclosed casing and measures 5.12” L x 3.39” W x 1.69” H (130.0 mm x 86.0 mm x 43.0 mm). The RPS-500-48-SF (Figure 2, right) with a side-mounted fan is slightly larger at 6.30” L x 3.39” W x 1.69” H (160.0 mm x 86.0 mm x 43.0 mm).

Figure 2: Two models of MEAN WELL’s RPS-500-48 power supplies, with a side-mounted fan version on the right. (Image source: MEAN WELL)

Also offered by MEAN WELL are the MPM series (encapsulated) and MFM series (open-frame) PCB power supplies that can be directly soldered onto the PCB motherboard of different types of medical equipment. They are available in 5 W, 10 W, 15 W, 20 W, or 30 W versions. They feature ultra-low no-load power consumption (< 0.075 W), a wider operating temperature range, and higher efficiency than previous generation power supplies.

The NMP650/1K2 is a series of configurable modular power supplies designed to accommodate multiple DC voltages in a 1U low-profile enclosure. They are available in 5 V, 12 V, 24 V, and 48 V output options. Suited for medium-to-high power medical systems, each module can output up to 240 W and has built-in voltage and current adjustment functions.

MEAN WELL's LOP Series (example in Figure 3) of PCB type power supplies offer low-profile dimensions of 4.00” L x 2.00” W x 1.00” H (101.6 mm x 50.8 mm x 25.4 mm) with the ability to provide 140 W under natural air cooling, and 200 W with an external fan. They are available in a voltage range of 12 V to 54 V and are designed for high reliability, quality, efficiency, and safety.

Figure 3: The LOP-200-48 AC-DC low profile open frame power supply. (Image source: MEAN WELL)

Also offered from MEAN WELL is a DC/DC medical power solution, the MDS01 series, aimed at solving design issues related to insufficient isolation levels or excessive leakage current. With SIP7 packaging, these single output, 1 W isolated and unregulated module type medical grade DC/DC converters are well-suited for medical instruments, and operate in a temperature range from -40°C to +73°C. Model options are available with 5 V, 12 V, and 24 V inputs, with output voltage options of 3.3 V, 5 V, 12 V, and 15 V.

Conclusion

MEAN WELL provides a variety of medical-grade power supply solutions that comply with the latest standards, capable of satisfying different design requirements to help medical device developers achieve optimal performance and safety.