Designing medical devices is a complicated task, largely because of all of the standards that have to be met. To a design engineer it may seem as if the products need as much certification as the physicians who will use them. But there is logic behind all the paperwork: Someone’s life may depend on a steady power supply to a critical medical device.
The good news is that—design difficulty and serpentine approval process notwithstanding—clever engineers at CUI, RECOM, and Powerbox have recently come up with new supplies that meet the latest IEC 60601-1 standards for medical applications.
To better understand what’s involved, let’s take a moment to review the relevant standards and how they are applied. We’ll start with the umbrella standard IEC 60601-1. It provides general requirements that address the basic safety and effectiveness of medical electrical equipment. And it has undergone substantial revision since being first published in 1977.
For example, the second edition of IEC 60601-1 (1988) established risk guidelines in the “patient vicinity” that applied when a device was within a 6-ft. radius from the patient. Three use categories of increasing severity were defined:
- Type B (body) equipment operates within this vicinity, but without patient
- contact. Examples include x-ray machines, hospital beds, and MRI scanners.
- Type BF (body floating) equipment makes physical contact with the patient. Examples include thermometers, blood pressure monitors, and ultrasound equipment.
- Type CF (cardiac floating) equipment makes physical contact with the heart (e.g., defibrillators).
The 3rd Edition of IEC 60601-1, released in 2005, included a greater emphasis on risk management. It extended the patient focus to require an overall means of protection (MOP) that combines one or more “means of operator protection” (MOOP) and “means of patient protection” (MOPP). IEC 60601-1 (Edition 3.1) serves to ensure that no single electrical, mechanical, or functional failure poses an unacceptable risk to patients and/or operators.
The United States and Canada currently require compliance with Edition 3.1. At the same time, however, the FDA has already accepted the 4th edition (2014) in the U.S. This includes EMC standards, and prefers products to be tested to 4th edition standards.
The power products we will discuss all meet these standards. Here, then, are the specifics:
CUI’s Power Group has introduced five new open-frame series to its line of internal ac-dc medical power supplies. Ranging from 180 W up to 550 W and certified to the medical 60601-1 edition 3.1 safety standards for 2 × MOPP applications and 4th edition EMC requirements, the VMS-180, VMS-225, VMS-275, VMS-350, and VMS-550 series feature efficiency up to 94% and power densities up to 30 W/in3. The new models are housed in 2 × 4 in. (50 × 101 mm) and 3 × 5 in. (76 × 127 mm) packages, with profiles measuring as low as 0.75 in. (19 mm).
CUI’s medical ac-dc power supplies range from 180 W to 550 W, featuring efficiency up to 94% and power density up to 30 W/in3.
A compact, high-density solution for medical diagnostic equipment, monitoring devices, and dental application, the new VMS series provides output voltage options from 12 to 58 V dc, have universal input voltage ranges from 80 to 264 V ac, and boast no-load power consumption as low as 0.5 W. The new models also carry an input-to-output isolation of 4,200 V ac, with leakage current ratings as low as 0.3 mA at 230 V ac. Operating temperatures range at full load from −40°C up to +50°C with forced air cooling, derating to 50% load at +70°C. Additional features include protections for over-voltage, over-current, and short circuit; power factor correction; and a 12 V dc/500 mA fan output.
Developed for medical PCB designs, RECOM’s RACM18 and RACM30 (18W and 30W, respectively) ac-dc converters are certified to the latest 60601 medical standards, as well as the EN60335 household and the IEC/EN60950 ITE standards.
RECOM’s RACM8 and RACM30 take up less than 2 × 2 in. on the PCB, and their round shape allows them to be fitted into flush mount wall installations.
IP68 waterproof encapsulation enables the modules to withstand harsh operating conditions allowing for versatile uses in medical, household and industrial applications. The modules take up less than 2-in.x 2-in. on the PCB and their round shape also allows them to be fitted into flush mount wall installations. With a certified operation up to 5000m altitude (the altitude rating is important as countries in South America as well as China are bringing healthcare to mountainous region-based populations) and temperature ranges from -20°C up to +80°C, these modules are built to power compact applications in medical healthcare, household, smart building and automation appliances.
Powerbox has launched a new series of power supplies for medical applications requiring BF (Body Floating) class insulation and full operation up to 5,000 meters altitude to power medical healthcare facilities and equipment. The OBR04 series of 600-650 W (with a peak power level of up to 720 W) single-output ac-dc Medical SMPSs comply with the latest EMI coexistence standard IEC 60601-1-2:2014 (4th edition), and are available in 12 different voltages from 12 V to 58 V with an efficiency rating up to 91%.
The power supply is designed for global operation with an input frequency range of 47 to 63 Hz. The input current at 115 V ac and 60 Hz is 8.4 A (RMS), and 4.2 A (RMS) at 230 V ac, 50 Hz.
The Powerbox VMS-180 series is a 180 W high-density, open-frame, ac-dc power supply certified to the medical 60601-1 (edition 3.1) safety standard.
Input-to-output isolation is 4,000 V ac (2× MOPP), input to ground is 1,500 V ac (1×MOPP) and output-to-ground is 1,500 V ac; Powerbox points out that conventional products frequently offer only 500 V dc isolation. All products are available in single, dual, triple, or quad outputs.
Housed in an aluminum chassis, dimensions are 165.8 mm × 101.6 mm × 62.5 mm (6.53 × 4.0 × 1.95-in.) and the series is available in a “U” shape chassis or an enclosed box with built-in fan. The power supply can be safely operated within a temperature range of −10°C to +70 °C and can be stored at −40°C up to +85°C.