Articles
Articles
Medical Power Supplies and Electromagnetic Interference
by Michael Allen, Bear Power Supplies
Medical Design Briefs
One of the challenges of using commercial power supplies in medical instruments is electromagnetic interference (EMI). Commercial power supplies often list “meets Class B” for EMI, but this is often with conditions that are completely unrealistic or impossible for a medical system designer to meet. If designers assume electromagnetic compliance (EMC) in the power supply, they may find themselves chasing EMI problems and making last-minute system design changes, such as adding filtered power entry modules, shielding, and other compensation, before they can launch the product.
This article discusses critical details to look for in commercial medical power supplies with respect to EMI. It also explores why it can be advantageous to consider a custom design to meet EMC as well as cost, performance, and lead time requirements.
Read the article at Medical Design Briefs
Designing a Medical Power Supply
by Danielle Sklepik, Bear Power Supplies
Power Systems Design
Power supplies for medical equipment must comply with IEC/UL 60601-1 3rd edition. Complying with this standard involves more complex isolation techniques, and requires components that are larger and more expensive than those used in industrial or commercial power supplies. Experienced power supply designers can design transformers and other components to maximize performance and reliability, and keep costs within reason, while meeting the justifiably stringent requirements that ensure patient safety.
Within the IEC/UL 60601-1 3rd edition standard there are three categories of equipment. B-rated equipment will have only brief contact with a patient – for example an MRI scanner. BF-rated equipment will have routine contact with the skin; for example ultrasound equipment. CF-rated equipment is likely to make direct internal contact with a patient, for example surgical cauterizers, cameras, and measurement devices. All three categories pose special challenges for the power supply designer, with the CF-Rated category being the most difficult. These challenges fall into four main areas: Creepage distance and air clearance, leakage current (primary to secondary), dielectric strength, and EMI requirements. Learn about design considerations to meet these challenges.
Read the article at Power Systems Design | or view or download the PDF
Medical Power Supplies and Capacitor Choices
by Danielle Sklepik, Bear Power Supplies
Power Systems Design
Operating rooms and clinical settings are crowded with instruments that pack in more functions and features every year, such as surgical tools with lights, lasers and video microscopes. The pressure for them to be smaller, lighter and easy to move around continues to grow. Since the AC-DC converter is often the largest component in an instrument, this pressure lands heavily on the power supply designer. The drive to minimize the size of the power supply conflicts with the imperative for reliability. This leads to some interesting challenges in specification development, component selection and board layout.
Understanding Power Supplies and Inrush Current Limiting
By Michael Allen, Bear Power Supplies
Electronic Products
This technical article describes the importance of inrush current limiting, and compares advantages of the techniques commonly used in commercial power supplies.
Understand Surge Protection Techniques for Low-Power Outdoor Electronics
By Stuart Wood, Bear Power Supplies
ECN
The growing use of low-power electronics in outdoor settings means that designers who are accustomed to creating indoor systems may need to brush up on surge protection techniques appropriate for greater exposure to lightning-induced surges. This article explains protection techniques for "category C, low exposure" equipment installed outside of a building. These systems include video surveillance systems, outdoor LED lighting systems, pole-mounted RF repeaters, and sensors and monitors in clean energy, oil, gas and other industrial applications.
Next-Gen Smart Grid Equipment Challenges Power Supply Designers
By Michael Allen, Bear Power Supplies
Electronic Design
This next wave of smart grid equipment places new demands on the engineers who design it. Specifically, unlike in-home smart meters, much of this new equipment will operate outdoors and under harsh environmental conditions. One of the most unexpectedly complicated aspects of designing an electronic device for outdoor use is the power supply, usually an ac/dc converter, which regulates the input voltage and converts it to levels suitable for the system components. We discuss how to design for the key challenges: extreme high temperatures, extreme low temperatures, and repeated high transients (e.g. lightning strikes).
How to Spec a Reliable Custom Power Supply: Five Essential Tips
By Michael Winslow, Bear Power Supplies
Electronic Products
When reliable power matters – such as in commercial, industrial and medical systems – even the most careful designers fail to include some essential information in their power supply specification. Here are five tips for specifying a reliable custom power supply unit (PSU) with the right balance of performance and cost for your application.
Designing Power Supplies for Portable Devices
By Michael Allen, Bear Power Supplies
Medical Design
Medical professionals expect high performance and reliability from portable medical electronic systems. Meeting these requirements often means that you will have to design the unit's DC/DC converter yourself, or commission a custom design. Here are several key factors to keep in mind, based on BEAR's experience designing power supplies for portable medical devices and other portable systems.
Hot Tips on Temperature Specs
By Brandon Hallen, Bear Power Supplies
Machine Design
What do a vendor's temperature specs tell you about the expected lifetime of a power supply? Can you use the manufacturer's mean time between failures (MTBF) data to get an idea of how long the power supply will last? This article answers these questions and more, explaining how to examine the temperature rise and construction of a power converter to get a much truer picture of a power supply's quality and life expectancy.