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Select DC/DC Converters That Minimize Patient Shock Risks

When selecting DC/DC converters for medical applications, it’s important to remember that power products typically used in medical designs can potentially harm a patient. Power products that meet IEC 60601 medical standards are designed with patient protection in mind. IEC 60601, Part I contains specifications and values that can prevent patients from incurring accidental electrical shock. Two of the three main specifications — isolation voltage, and creepage or clearance distances — are covered here.

In addition to considering power products that offer isolation protection between the electrical circuits and equipment that may contact the device, designers should also be aware of a third specification: Leakage currents, also known as touch currents. They’re the leakage paths from an enclosure that may contact a patient or operator. Because medical patients are often in a weakened state, even a small amount of leakage current can cause them harm. The standard specifies maximum levels of 100 µA for normal operation and 500 µA for a single fault condition.


DC/DC Converter Family Offers Exceptional Leakage Current Characteristics and Satisfies EN60601-1

One particularly good example of a DC/DC converter series that meets IEC 60601, Part 1 is Polytron Devices’ recently introduced MTWA2 and MTWA4 2-watt and 3.5-watt devices. Not only do these DC/DC converters with 2:1 input range exhibit a low leakage current of 2 µA, they offer 5000V AC input to output isolation and the highest level of patient protection — 2 x MOPP. Thanks to process efficiencies that result in a lower cost versus previous DC/DC converters, this series is a desirable option for portable devices with low wattage requirements.

The MTWA2 and MTWA4 Series DC/DC converters with 2:1 input range are both available in 4:1 input versions — MTWB2 (2 watts) and MTWB4 (3.5 watts), respectively. Additional features and specifications include:

  • 2:1 wide input voltage range: 4.5V to 12V DC input; 9V to 18V DC and 18V to 36V DC and 36V to 75V DC.
  • Efficiency as high as 82 percent.
  • Over voltage, short circuit and under voltage protection.
  • Availability in miniature DIP16 and SMD16 packages.
  • RoHS compliance to 2011/65/EU.

Medical Device Designers Can Realize Cost-Effective Performance and Patient Safety

Power products that meet IEC 60601, Part 1 are designed to protect patients from risk of accidental shock. When specifying DC/DC converters, be sure to look for products that meet this specification while exhibiting low leakage current. Polytron Devices’ MTWA2 and MTWA4 Series DC/DC converters offer low wattage, low cost and excellent patient protection characteristics to give designers of portable medical devices exceptional performance, efficiency and peace of mind.

For more information about Polytron Devices MTWA2 and MTWA4 Series DC/DC converters, visit http://polytrondevices.com/applications/medical.

 

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Deliver More Power to Shrinking Medical Devices Without Sacrificing Space

When it comes to choosing a power supply for medical devices, two things come to mind. First, protect the patient from the risk of electrocution. The second is how to sufficiently power your device within a compact design. 

That’s because medical devices are adding more high-performance, power-hungry functions while also becoming more portable, moving out of hospital environments to clinics, ambulatory care facilities and even patient bedsides. One way to maximize power delivery to shrinking medical devices is to look for a high-power density power supply. Another option? Remove the power source from the unit altogether by choosing an external power supply.

High-power Density External Supplies Address Various Design Challenges

Polytron Devices’ MUI310 Series desktop AC/DC power converters provide ample power for various hospital-based instruments yet are small enough for use with at-home patient monitoring equipment. They come in a small 7.78 × 4.01 × 2.01-inch package with output voltages of 12, 19, 24, 32 and 44V DC and can deliver up to 310 watts of power. By incorporating an external, high-density power supply such as the MUI310 for their medical device, designers can:

  • Reduce device size and weight. Compact size and light weight are crucial to medical device portability, particularly if it will be placed near the bedside on a cart or inside a home.
  • Increase functionality. By freeing up design space, engineers can bolster the device’s capabilities and enhance its performance.
  • Minimize cooling requirements. When you remove the internal power supply to free up precious space, you’re also removing a major source of heat from the system.

MUI310 Series power supplies meet UL/CUL 60601-1, EN60601-1 and IEC60601-1 3rd Edition and 2 X MOPP standards, which can help ease the device manufacturer’s safety and EMC approval process. In fact, 2 X MOPP is the highest level of patient protection from electrocution. The MUI310 Series also offers:

  • An LED power indicator.
  • 4,000V AC input/output isolation.
  • Class I protection, 1,800V AC isolation.
  • 87.5 percent efficiency.
  • Active power correction.

Efficient Use of Space Yields Smarter Medical Device Designs

High-density power supplies can make efficient use of design space, and they can be especially beneficial for medical devices that are packing more functions into smaller units. In many cases, the MUI310 desktop AC/DC converter can eliminate the need for a much larger, heat-generating internal power supply, thereby making it easier to bring your medical device wherever it’s needed.

For more information about Polytron Devices’ MUI310 Series AC/DC power converters, visit http://polytrondevices.com/applications/medical.

 

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Make Sure Your DC/DC Converters Take The Heat And Withstand Emissions in Railway Applications

When selecting a DC/DC converter for railway applications, you might think that once you’ve found the device with the right input voltage range, output power, efficiency and isolation characteristics, your job is done. However, there are other factors to keep in mind when ordering your part, which may add components to your design and affect space. Here are two conditions to consider:

Avoid Thermal Issues and RFI

DC/DC converters may play an important role within the railcar, but the operating environment is anything but hospitable to them. For instance, DC/DC converters may be subject to extreme temperatures and poor airflow aboard railcars, or those with high power densities may require additional heat removal to ensure a consistent surface temperature.

Railway applications also present many opportunities for signal disturbances that can affect the operation of various devices. This is why it’s important that DC/DC converters are tested to meet EMC (electromagnetic compatibility) standards. The International Electrotechnical Commission created the EN61000 family of EMC immunity standards for equipment subject to radio frequency emissions (RFI). They include ESD (EN61000-4-2), radiated immunity (EN61000-3) fast transients (EN61000-4-4), surges (EN61000-4-5) and conducted immunity (EN61000-4-6). In addition, EN55032 establishes EMC standards for information technology equipment in railway applications, as covered here


Go the Extra Mile With Your DC/DC Converter Manufacturer

Be sure to ask your vendor about the optimal cooling method for the DC/DC converter you choose. Polytron Devices can provide optional heat sinks to many of its power products, such as the LWB60 Series single and dual output DC/DC converter modules with an extra-wide input voltage range that’s ideal for railway applications. This DC/DC converter also includes built-in overtemperature protection to prevent damage to components or equipment that could compromise safe operation.

Your vendor’s datasheet also should indicate whether the converter has been tested for compliance to various EN61000 immunity standards. The LWB60 Series features a six-sided continuous metal shield which minimizes conducted and radiated noise, and it meets EN61000-4-2 through -6 — including EN61000-4-4 and EN61000-4-5 when used with an external filter capacitor along with a TVS voltage suppression diode. While many DC/DC converters may have the specifications you seek for your railway application, consider them a starting point. Additional diligence can give you greater peace of mind.

For more information about the LWB60 Series visit the product page.

 

Visit the LWB60 Product Page

 

 

Railway Applications Demand DC/DC Converters That Handle a Diversity of Input Voltages

Modern railways rely on a host of electronic systems in order to operate safely and provide passenger comfort and convenience. A typical railcar distributes either 72V or 110V DC of battery power to these various systems.

Each of these systems has its own DC voltage which is often lower than the central battery voltage. Railway distributed power system designs incorporate DC/DC converters to convert the main battery voltage into the input voltage of the downstream electronic system, and DC/DC converters with a wide input voltage range can accommodate a greater number of power systems. In addition, the main battery power may also fluctuate when feeding higher power systems onboard the train, so a DC/DC converter with a wider input range is better suited to handle those wide variations in voltage.

Wide input range DC/DC converters are especially desirable for railway applications because:

  • They can accommodate a broad range of common battery and bus distribution voltages.
  • Designs can account for wide voltage tolerances and fluctuations.


DC/DC Converters Satisfy a Diversity of Railway Power Requirements

Polytron Devices offers DC/DC converters that address the diverse needs of railway power systems. For example, the OFQC60 Series 60-watt quarter-brick DC/DC converter features a wide 12:1 input voltage range covering potential distribution voltages of 9-75 V DC or 14V to 160V DC, according to the EN50155 standard. The wide input range allows the OFQC60 to accommodate many different power systems within the railway environment. Additional features and characteristics include:

  • Output voltages of 5, 12, 15, 24, 28, 48 and 53V DC.
  • Isolation voltage up to 3000V AC.
  • Efficiencies up to 92 percent.
  • EN55032 compliance.
  • Protection against over current, over voltage, under voltage, short circuits and over temperature.
  • RoHS and REACH compliance with CE Mark pending.


A Wide Input Voltage Range Means More Design Flexibility

As railways add more power systems to enable train operation and provide passenger amenities, DC/DC converters must accommodate a greater number of input voltages. Polytron Devices’ OFQC60 Series of 60-W DC/DC converters boasts an extremely wide 12:1 input range so designers can use them in a variety of power systems for modern railways.

For more information visit the OFQC60 product page

 

Visit the OFQC60 Product Page

EN50155 Certification Ensures DC/DC Converters Handle Multiple Railway Challenges

Railway applications present many potential uses for DC/DC converters. Electronic systems onboard modern trains for both critical systems or passenger comfort and convenience need DC/DC converters to lower the main DC battery voltage to their individual input requirements. But, all these systems in close proximity create unwanted signals that affect the safe operation of the train. They also encounter harsh environmental conditions aboard the train including shock, vibration and temperature and humidity extremes.


What is EN50155?

EN50155 is an international standard pertaining to the conditions that can impact railway operations and safety such as harsh environments or the interacting signals between multiple electrical/electronic systems. It encompasses several existing standards, such as EN50121-3-2 for EMC (electromagnetic compatibility) and EN61373 for shock and vibration. In order to attain EN50155 approval, power supplies undergo stringent testing for a host of challenging conditions. Some of the most important parameters pertaining to power supplies include:

  • Input voltage. Since trains present a diversity of bus voltages, EN50155 outlines nominal input voltages of 24, 48, 72, 96 and 110V. EN50155 sets limits for fluctuations of the rated voltage and establishes short-term deviations. The supplies must also provide an output during power interruptions.
  • EMC. With so many electronic systems populating railway vehicles, EN50121-3-2 sets strict limits to radiated emissions and ESD levels, including events like surges and fast transient bursts.
  • Shock and vibration. Not surprisingly, components inside moving rail stock will encounter frequent vibration and mechanical stresses. EN50155 establishes minimum vibration and shock requirements depending on where the device is mounted in the railway vehicle: body mounted, bogie or "truck" mounted or axle mounted.
  • Temperature and humidity. The standard provides different classes of operating temperatures for power supplies, depending on the environment. They must operate at 85 percent efficiency to reduce dissipated power that can otherwise be lost as heat, and they are required to withstand a 15-degree overtemperature at startup for 10 minutes. EN50155 also establishes humidity requirements.


Look for EN50155 Compliance

Designers that choose a DC/DC converter with EN50155 approval can be sure it will perform reliably aboard rolling stock. One example of a DC/DC converter designed especially for railway applications is Polytron Devices’ HWB Series DC/DC converters. These half-brick power supplies operate from 9-36V, 8.5-36V, 16.5-75V and 43-160V DC with no minimum load requirement, and they boast a high efficiency of up to 91 percent. The series’ EN 50155 approval also means it satisfies EN50121-3-2 (with external filter) and EN61373 for shock and vibration. Additional approvals include the EN61000-4-2, -3, -4, -5 and -6 EMC standards and UL/EN/IEC 60950-1 for safety. HWB Series converter safeguards include overvoltage, overtemperature and short-circuit protections plus heat sink options.


Conclusion

When selecting DC/DC converters for railway applications, look for devices that carry EN50155 certification. HWB Series DC/DC converters have been tested and approved to EN50155 so you can be sure they can both manage EMC and perform in the challenging conditions aboard rolling stock. Polytron Devices can furnish the applicable EN50155 test reports upon request.


For more information about Polytron Devices’ HWB Series DC/DC converters for railway applications, view our Railway Data Sheets.

View Our Railway Data Sheets

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