Power supplies give designers a head start

Medical electronics products need power, and if you are involved in medical-electronics design, you can give yourself a head start by choosing a power supply designed for medical and home healthcare applications. Such a supply can help you comply with relevant EMC and medical safety standards and achieve the proper levels of Method of Patient Protection (MOPP) and Method of Operator Protection (MOOP): 1 x MOPP and 1 x MOOP or the more stringent 2 x MOPP and 2 x MOOP.¹ Several recent introductions indicate the selection of supply form factors and ratings available to you—including external, internal, and surface-mount.

First, in September SL Power Electronics introduced its ME60 Series medical-grade external power supplies (Figure 1).“These supplies were specifically designed to meet the requirements of home healthcare equipment,” said Paul Kingsepp, product manager for SL Power. Meeting IEC 60601-1-2 fourth edition electromagnetic compatibility requirements, the ME60 models also are approved to AAMI ES/CSA C22.2/EN/IEC 60601-1, third edition, meeting 2 x MOPP. The supplies also adhere to the new U.S. Department of Energy’s Level VI efficiency requirements.

Figure 1. ME60 Series medical-grade external power supplies
Courtesy of SL Power Electronics

Kingsepp said ME60 supplies, just like SL Power’s supplies for test-and-measurement applications, use high-quality electrolytic capacitors, extending expected product life beyond seven years. Mean-time-between-failures is greater than 250,000 hours. The supplies also offer low common-mode noise, tolerate high levels of ESD (in accordance with IEC 61000-4-2, level 4 standard: 8 kV/15 kV), and feature surge protection (in accordance with IEC 61000-4-5, level 4 standard: 2 kV/4 kV). The supplies provide Class B EMI filtering with a 3-dB margin. The supplies are available with many input connection types for worldwide use.

Housed in an impact-resistant polycarbonate enclosure that adheres to the IP22 requirement for dust and water ingress protection, the desktop and wall-plug models offer regulated output power with low ripple, no-load power consumption better than 0.5 W, and short-circuit and thermal protection. With an operating temperature range of 0°C to 50°C, the units comply with worldwide safety and performance standards from UL, cUL, CE, and RoHS. Interchangeable blade options and modified or custom designs are available as well as custom labeling. The supplies feature a three-year warranty. Pricing for the ME Series models starts at $22 for production quantities.

Internal supplies

Figure 2. CUS350M medical and ITE certified 350-W power supplies
Courtesy of TDK-Lambda Americas

If you need an internal supply, you could consider one such as the TDK-Lambda CUS350M medical- and ITE-certified 350-W power supplies (Figure 2). Requiring no external airflow, the series is suitable for hospital, clinical, dental, and home-based medical applications as well as for use in professional-broadcast, test-and-measurement, and audio equipment requiring low audible noise.

Carrying a three-year warranty, the CUS350M series currently is available with 12-V, 18-V, 24-V, or 48-V outputs with a user adjustment of ±5%. The series can provide up to 350-W output power (convection cooled) at 40°C ambient, with derating to 175 W at 70°C. Efficiencies are up to 94% with an average rating of 87%, and standby power consumption is less than 0.5 W; the supplies comply with the European ErP Directive.

The units are enclosed in a 190-mm x 87-mm x 40-mm package and will operate from 85-VAC to 264-VAC inputs. “/F” suffix models include a 5-V, 0.5-A standby output; a 12-V, 0.3-A auxiliary output; remote sense; an isolated “DC Good” signal; and a remote on/off function. Isolation is 4,000 VAC (2 x MOPPs) and 1,500 VAC (1 x MOPPs) input to ground and output to ground.

The CUS350M power supplies are certified to IEC/EN 60601-1, ANSI/AAMI ES 60601-1, and IEC/EN/US 60950-1 and CE marked for the Low Voltage and RoHS2 directives. The units also comply with EN 55011-B, EN 55022-B, and FCC Class B for conducted emissions (Class A radiated), and they meet the IEC 61000-4 immunity and IEC 61000-3-2 harmonic current standards.

In addition, XP Power recently introduced the EPL225 Series open-frame AC/DC power supplies approved for industrial, IT, and medical applications. The series comprises seven single-output models that offer a range of standard output voltages from +12 VDC to +48 VDC. The supplies include a secondary 12-VDC, 0.5-A fan output. Packaged in an industry-standard 1U footprint (50.8 mm x 101.6 mm x 32.3 mm), the series has a convection-cooled output power rating of 150 W. Output power up to 225 W is available with 10 cfm of forced airflow.

The series complies with the universal safety standard EN 60950-1 for IT equipment in addition to the medical-safety standards ANSI/AAME 60601-1 and IEC/EN 60601-1 third edition. The units meet the standards EN 55011 and EN 55022 for Class B conducted and Class A radiated EMI specifications.

The EPL225 series offers a minimum average efficiency of 93% and a maximum efficiency of 95%. Green attributes include a no-load power consumption of less than 0.5 W. The supplies provide an extended temperature range from -20°C to + 70°C with no derating until +50°C. The supplies come with a three-year warranty.

DC/DC converters

And finally, in October Murata introduced the NXJ1 Series single-output, high-reliability, high-isolation, 1-W surface-mount DC/DC converters (Figure 3) designed for medical products; the converters also can serve applications in industrial, transport, and telecom markets. Measuring 13.72 mm x 10.46 mm x 4.36 mm, this compact low-profile series features six models comprising nominal input voltage options of 3.3 VDC, 5 VDC, or 12 VDC and single outputs of 3.3 VDC, 5 VDC, 12 VDC, or 15 VDC.

Figure 3. NXJ1 DC/DC converters for medical applications
Courtesy of Murata

Product manager Ann-Marie Bayliss at Murata commented that with UL60950 recognition for reinforced insulation and ANSI/AAMI ES60601-1 2 x MOOPs pending, “The NXJ1 offers enhanced features previously not available in a miniature low-profile, surface-mount product.”

The NXJ1 series is manufactured using an automated process that also fabricates an integrated transformer into the substrate, contributing to product reliability and repeatability in a halogen-free, inspectable land grid array package. The industry-standard footprint is compatible with previous models, making it suitable for replacement in existing applications as well as for new space-constrained, low-profile designs. The converter features short-circuit protection, and agency recognition is pending to the UL60950 standard for reinforced insulation and 4.2-kV high-pot test.

The device can operate across the full industrial temperature range from -40°C to +85°C. It has an MSL 2 rating and is compatible with a peak reflow solder temperature of 245°C per J-STD-020 and J-STD-075.

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