It is clear that the medical electronics industry has entered an era of dramatic transitions that touch virtually every aspect of the business from design to marketing. As is often the case with such substantial “Big Picture” changes, it can be easy to overlook how these changes affect foundational technologies such as power supplies, which are a vital component in all medical electronics.
Key developments, triggered by general technological advances, an aging population worldwide, and even aspects of government healthcare reforms are driving these trends that include:
- Proliferation of wireless technologies,
- Proliferation of implantable medical devices,
- Push towards home healthcare options versus in-hospital or outpatient clinic visits, and
- Greater demand for cost containment in medical products and services.
For each of these trends, careful planning of the power design from the beginning can enhance end product feature sets while reducing costs, maximizing reliability, and accelerating time-to-market.
Choosing the right power supply design is imperative for an overall successful product. With ongoing goals of increased density, reliability, and efficiencies, power ratings need to be reviewed carefully. Of course, product life, thermal issues, input voltage, load, and cooling needs are also vital considerations. Other factors especially important for medical electronics vendors include demonstrated reliability and proven quality systems. These encompass control processes for design, purchasing, and production as well as product traceability and Corrective and Preventative Actions (CAPAs), which have been the consideration for power supplies. However, because of increased regulation, medical device designers must now consider closely their electromagnetic compatibility (EMC) performance. EMC compliance specifications are spelled out in various EN 61000 standards as listed in Table 1.
EN 61000-3-x sets limits and measures methods for low frequency emissions on the AC mains, while EN 61000-4-xx sets limits on susceptibility or immunity of the equipment powered from AC mains. These standards require precise performance so the power supplies or other electronic devices do not affect the safety and effective functionality of other implantable or critical care medical devices.
The stricter standards are also needed to sustain full operation despite noisy and a somewhat less regulated power conditioning environment at home. For example, an infusion pump malfunctions when a cell phone is used in close proximity to the patient. Or perhaps, a home ventilator shuts down when the line voltage dips below the minimum operating limit caused by a neighboring motor or generator use. Or, a remote patient monitoring device is zapped when touched by someone walking around the house and building electrostatic discharge.
Once designers determine the basic power requirements, the final hurdle in power supply product selection involves meeting standards for safety, EMC, and regulatory environmental impact compliance.
Today’s medical electronics must meet stringent safety requirements and performance testing adhering to various standards starting with IEC 60601-1 3rd Edition for medical devices. Depending on the end use of the product and its implementation, additional standards such as EN and IEC standards for EMI/EMC, RoHS compliance, and CE Mark may also apply.
When selecting an AC or DC power supply—either off the shelf or custom—designers must consider the specific performance criteria suitable for their application when defining these requirements. In addition, keep in mind that transition to the IEC 60601-1-2 4th Edition standard on electromagnetic disturbance started in 2014 (See Figure 1).