Technical Blog

Power components — like other components in an electronic circuit — generate excessive heat that can hurt the system's performance. Power supplies and converters are no exception, and dissipating unwanted heat away from power components and other sensitive circuitry is vital to ensuring performance and reliability. Let's look at some basic thermal management strategies when implementing DC-DC converters, with an emphasis on using heat sinks to dissipate heat to the surrounding environment.

There are three ways to move heat away from a DC-DC converter:

• Radiation. Heat moves between bodies at different temperatures.
• Convection. Heat is transferred through a fluid — typically air.
• Conduction. Heat travels through a solid medium.

Heat sinks are a particularly effective conductive heat-removal technique. The fins that extend from the heat sink increase the DC-DC converter's surface contact with the surrounding air, reducing the converter's thermal resistance and keeping it performing reliably. While heat sinks are a smart choice for dissipating heat, there are important factors to consider when pairing one with your DC-DC converter. For example, large heat sinks are typically more effective than smaller ones, but they can also occupy too much space and height in a design. Other factors include the ambient temperature, power density and efficiency of the converter, as well as weight and cost.

For these reasons, we've expanded our heat sink options for the RWB60 Series of 60-watt railway DC-DC converters. With more options to choose from, this DC-DC converter family can address many design factors and operate in a variety of thermal environments. In addition to the original heat sink height of 0.33 inches (8.5 millimeters), our three new heat sinks come in heights of 0.3, 0.5 and 0.8 inches (7.6, 12.7 and 20.3 millimeters) to meet specific efficiency and space requirements. The new heat sinks feature a redesigned clip assembly, reducing their footprint to fit into tight spaces. The new layouts are shown below.

RWB60 Series DC-DC converters operate over a 4:1 wide input range and provide single and dual outputs for use in railway applications. The units come in a 2.0 by 1.0 by 0.40-inch package to fit tight spaces and offer high efficiency up to 91.5 percent, 3,000V DC isolation voltage, six-sided shielding to minimize noise leakage, low standby power and remote ON/OFF control for energy savings.

Here's how to order heat sinks with the RWB60 Series DC-DC converter:

• -HS: 0.33-inch height
• -HC1: 0.3-inch height
• -HC2: 0.5-inch height
• -HC3: 0.8-inch height

The temperature adaptation performance of the new heat sinks on the RWB60 DC-DC converters is shown below.

Keep Your DC-DC Converter and Nearby Components Cool

To keep your DC-DC converter functioning and nearby components cool, thermal management devices like heat sinks must be an essential part of your design. RWB60 Series 60-watt DC-DC converters are available with a variety of heat sink options to meet the design's space and dissipation requirements so you can obtain optimal performance from your converter and system.

For more information about the RWB60 Series, visit our product page.

For designers of industrial systems and equipment, a tried-and-true power supply brings peace of mind. All too often, however, that peace of mind can end when that go-to supply is out of reach due to long lead times, discontinuation or a steep price. Changes can be frustrating, especially when they put your design in a bind.

Fortunately, it's still possible to get the industrial power supply you need at an attractive price. When you need to replace your regular industrial power supply, we've got you covered with some of the lowest-cost supplies in the market.

We recently introduced a broad range of industrial power supplies that are direct replacements for popular and more expensive models from other manufacturers. With this offering, you can still obtain the same characteristics and features you rely on while keeping costs in check. This new line of replacement switch mode power supplies has an input voltage range of 90 to 264V AC and is available with wattages of 35, 50, 75,100, 200 and 350 W.

Additional features of the IUMEW Series include:

• Efficiencies up to 88 percent.
• Compact shell designs.
• Good heat dissipation for long-term stable work.
• Meet EN standards for electromagnetic compatibility (EMC).
• Built-in safeguards such as short circuit, overload and overvoltage protection.
• Low profile designs, with heights as low as 30 millimeters (1.18 inches).

These new power supplies are well-suited for a variety of applications such as control system machinery, electronic equipment and instruments and industrial automation, as well as household appliances. Sample quantities are in stock and ready to ship.

No Need to Compromise

When it comes to power supplies for industrial equipment, you shouldn't have to contend with high prices and long lead times. With Polytron Devices industrial power supplies, you don't have to make sacrifices to get the performance you need at a competitive price. We're ready to assist you in obtaining the right industrial power supply for your application.

Be sure to speak to a Polytron Devices representative to help with your selection.

For more information about IUMEW Series power supplies, contact us.

Medical device designers must go to great lengths to ensure human safety. Medical equipment can pose hazards to patients in a weakened state as well as to personnel operating the devices. Accordingly, strict standards exist to help guarantee global compliance. For power supplies, one of the most important ones is IEC 60601-1, which covers essential safety-related specifications and values, such as isolation voltage and leakage current requirements that must be met to protect people from electrical shock.

To mitigate the leakage current that can affect patients, IEC 60601-1 classifies applied parts of medical equipment based on their proximity to or contact with the patient. While power supplies are not medical devices themselves, IEC 60601-1 establishes leakage current levels and isolation requirements for power supplies used in medical devices. The applied parts and leakage limits for each are as follows:

• Type B (Body). These parts operate near the patient. They are not intended to pass current to a patient and can be connected to ground. Allowable leakage current is 100 µA under normal conditions; 500 µA single-fault.
• Type BF (Body Floating). These parts are intended to deliver energy to or from the patient and do not connect with ground. Allowable leakage current is 100 µA under normal conditions; 500 µA single-fault.
• Type CF (Cardiac Floating). Type CF parts are intended to deliver energy to or from the patient for direct contact with the heart or bloodstream. Allowable leakage current is 10 µA under normal conditions; 50 µA single-fault.

Power supplies in Types B, BF and CF-rated B-rated parts require 4,000V AC input to output isolation. In addition, power supplies must satisfy these isolation requirements: Type B: 1,500V AC input to ground isolation and 500V AC output to ground isolation. Types BF and CF require 1,500V AC input to ground isolation and 1,500V AC output to ground isolation. To learn more about isolation, check out this blog post.

IEC 60601-1-Compliant Power Supplies Reduce Patient Safety Risks

When selecting a power supply for a medical device, make sure it complies with IEC 60601-1. Medical power supply manufacturers will also indicate whether a power supply meets Type B, Type BF or Type CF criteria. For designs requiring 240W of output power, our PFMUI Series of universal input switching power supplies are designed with patient safety in mind. Providing 4,000V AC input to output 2xMOPP insulation, these devices meet the UL/IEC/EN 60601-1 edition 3.1 safety standard and are suitable for Type BF applications when implemented into an appropriate system.

Additional features include high efficiency, 0.5W no-load input power and a PFC function of >0.9. PFMUI power supplies in the following package types:

• Open type (PFMUIO240)
• U chassis type (PFMUIT240)
• Enclosed type (PFMUIE240)
• DIN rail type (PFMUIE240-DN)

Look for Power Supplies That Meet IEC 60601-1 Standards

Because medical devices can potentially make patients susceptible to shock and safety risks, medical power supplies must meet stringent IEC 60601-1 requirements. Our PFMUI power supplies for BF-type applications satisfy IEC 60601-1 and other standards while providing medical device designers a choice in packaging options to suit their system’s needs.

Find out more information about our PFMUI medical power supplies and other switching power supplies.

For many medical devices, a switch mode power supply (SMPS) will be ideal for the design. After all, an SMPS provides excellent efficiency and power density for its typically small size. However, there are some instances where it may be desirable to use more than one switching power supply in a design. This blog post will explain why connecting power supplies in parallel makes sense, and it will show why including a means of current sharing in your design is important in these situations.

When To Consider Multiple Power Supplies

There are typically three reasons to use more than one SMPS in a medical device design:

• The load requires more current than a single SMPS can provide.
• Power supply reliability is critical, as is often the case with medical devices. Multiple power supplies provide the necessary redundancy for the application.
• Longer power supply lifetimes, thanks to better heat distribution.

Keep in mind that using multiple SMPSs involves challenges, and it is not always a straightforward process. For example, simply connecting power supplies in parallel does not necessarily mean that the load current will be distributed equally. Uneven distribution of the load current may stress power supplies or create thermal issues, resulting in premature power supply failure. In order to configure multiple power supplies in parallel, a controlling element is needed to ensure that current is shared equally.

As you consider using multiple SMPSs in your medical device design, be sure to understand the different methods of current sharing and select the right one for your application. Also, when selecting your SMPS, look for a power supply designed with current sharing in mind. Power supplies with built-in current sharing circuitry enable parallel connections with equal distribution of load currents when used with appropriate external components.

We offer a variety of switching power supplies with optional current sharing. For example, most models of the recently introduced PFMUIE500 Series of medical switching power supplies can be specified with a current sharing function, and they come in a 5.5 by 3.25 by 2.42-inch enclosed package to economize space in designs that call for parallel connections. In addition to their 500 watts of output power, the PFMUIE500 Series also features:

• 4,000V AC input to output 2MOPP insulation for patient safety.
• Remote ON/OFF function.
• Standby of 5V at 1A.
• Up to 92 percent efficiency.
• PFC function of >0.94.

Built-in Current Sharing Simplifies Designs and Enhances Reliability

When an application requires parallel power supplies, configuring a system with equal current sharing can be challenging. There are many factors and current sharing methods to consider, so be sure to work with your power supply manufacturer to make sure your system is configured correctly and with the proper components. Switching power supplies with built-in current sharing, such as the Polytron Devices PFMUIE500 Series, can help reduce the uncertainty and complexity involved with implementing multiple power supplies in your medical device design.

Find out more about our PFMUIE500 Series medical power supplies.

If you’re integrating a switch mode power supply (SMPS) into a system, you expect good power efficiency. You also have to be sure you’re getting the most useful energy when drawing power from the AC main. To get the most of your AC power draw, you must also consider the power factor during your SMPS selection. Let’s discuss some of the basics of power factor and what you should look for in a switch mode power supply.

Power Factor Basics

As switch mode power supplies draw power from the grid, not all of that power can be used. The SMPS typically draws the AC input current in short, high-magnitude pulses. As a result, the current is out of phase with the voltage. Because of the variance, some of the main energy is displaced and unavailable for useful work. This condition is known as power factor — a ratio of the supply’s working power compared to its apparent power. Power factor is expressed as a decimal between 0 and 1.

Without maximum working power, the system must draw more power and incur the associated costs. Poor power factor can also create harmonic distortion that can damage equipment in the circuit. To avoid these situations, power supply manufacturers employ power factor correction (PFC) techniques to bring the supply’s power factor as close to 1, or unity, as possible. For low-power supplies, PFC typically involves smoothing out the short pulses using passive components to create a low-pass filter. Higher-power supplies use control circuitry or a regulator to harmonize the input voltage and current. For most applications, SMPS that achieve a power factor of 0.9 or higher are ideal.

Our new UIA700 Series 700-watt switching power supply is one such example. It comes with a power factor figure of greater than 0.9, making it appropriate for a wide range of industrial equipment. It accepts a wide 90 to 264V AC input for use globally, and its small size of 6.7 by 3.66 by 1.61 inches makes it ideal for space-constrained applications. And, you don’t have to choose between a high power factor and high efficiency, thanks to the UIA700’s 92-percent efficiency rating.

Additional features and specifications include:

• A remote ON/OFF function for energy savings.
• Standby: 5V at 1A.
• Chassis mount with terminal strip.
• UL/IEC/EN 62368 approval.

When specifying a SMPS, keep in mind that domestic and international regions have regulations that define local power factor or harmonics requirements.

Optimize Power and Space

Switch mode power supplies with a PFC function make the best use of the main power, and those with a power factor of 0.9 or better are preferred for most applications. Our UIA700 Series switching power supply combines a high power factor, high efficiency and small size to achieve optimal AC power for a broad range of industrial applications.

For more information about Daburn Electronics’ Polytron Devices UIA700 Series switching power supply, visit our product page.