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Interpreting Complex Data Sheet Specifications For Power Supplies–Part I

The operating and safety specifications for power supplies have become more complex, adding to the length, level of detail and complexity of data sheets. Nowadays, the data sheet for a product series has to include everything from voltage combinations to mechanical drawings—oftentimes for dozens of different models. If you don’t know what you’re looking for, reading one can be a daunting task.

In the next series of blog posts, we’ll dig into some of the specifications you can expect to find on today’s power supply data sheets, including:

Electrical. To keep up with new technologies on the market, power supply manufacturers have had to add more output voltages to their devices, as well as widen the input voltage ranges. At Polytron, for example, a product series that used to have only 15 models now has well over 50 to account for all the new voltage combinations.

Thermal. Despite the demands for higher power and wider ranges, customers still want small packages. As a result, engineers have to come up with creative ways to avoid overheating, including adding heat sinks or fans to transfer heat away from the device. The addition of these components adds to a data sheet’s length and level of detail.

Packaging. In the past, power supply manufacturers typically offered only two mounting options: chassis and PC. Nowadays, however, products must be available in a variety of other mounting options, including screw terminal, vertical mount, DIN rail, surface mount, open-frame and enclosed types—to name a few. All of these require extra drawings that must be included on data sheets.

Safety. Many of the safety certifications listed on data sheets require rigorous testing—especially for medical applications. Many products, for example, require a CE mark, indicating they have met all safety and performance requirements for medical devices in Europe. Passing this certification now requires EMC testing, which typically takes several months, as samples need to be sent back and forth between the manufacturer and testing house. Data sheets are required to indicate all new certifications, testing procedures, special model numbers and designations.

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Resolving Heat Issues With Metal Header Heat Sinking

Linear power supplies can generate a significant amount of heat, particularly in military, scientific and industrial applications. That’s why these devices are often designed for free-air convection cooling–air flows over the unit, transferring heat away from the device and cooling it naturally.

But what happens if your linear power supply must be mounted in an enclosed case? This kind of setup restricts airflow around the supply, keeping temperatures high and decreasing the device’s mean time between failure (MTBF).

Fortunately, there is a solution.

Metal header heat sinking. Our MH suffix linear power supplies are designed with a heat sink base plate that is mounted on the inside wall of the enclosure. With the use of a heat sink compound, the supply radiates all of its heat into the enclosure and then out of the box to the outside atmosphere.

Material flexibility. It doesn’t matter if the enclosure is made out of metallic or non-metallic materials. All heat generating power supply components, mounted directly to the heat sink header, are electrically isolated. All cooling is taken care of, and the supply’s MTBF remains unaffected.

Our MH units, which pass UL safety standards, are currently being utilized in military applications for their thermal management features. They are also available in switching power supplies. You can learn more about our linear and switching power modules, including our P3/MHIA, P3 and P41 series. 


All About Linear Power Supplies

With the popularity of switching power supply technology, linear power supplies don't get the attention they deserve. But linear power supplies outperform switching units in clean-power applications that need minimal ripple current and low noise. Watch our new video to learn more.


Power Supplies For Medical Equipment

Want to make sure that the medical equipment you design will do more good than harm? Then pay attention to the power supplies you use. Many industrial power supplies simply do not comply with the safety standards that govern diagnostic, monitoring and treatment equipment. Watch our new video to learn all about linear and switching power supplies that do meet global standards for patient safety.  


When To Consider Linear Power Supplies Over Switching Models

With the advent of highly efficient switching-mode power supplies, linear power supplies are often thought of as old-fashioned and not very useful except in a few specific applications. Nothing could be further from the truth. In fact, modern versions of linear power supplies are making their way into a wide range of industries and applications that demand clean power with very little ripple and low noise (EMI and RFI).

Let’s take a quick look at the major differences between these two styles as well as a few applications where linear power supplies really shine:

Switching power supply advantages: For higher efficiency, a smaller form factor and lighter weight, switching power supplies are the clear winner. However, this higher efficiency and lower heat dissipation comes at a cost. Not only are they more expensive than linear versions, they’re also more complex and can cause electrical noise issues. Even so, their high performance, small footprint, and proven reliability are hard to beat compared to their linear counterparts.

Linear power supply advantages: When low common mode noise is a must, making the tradeoff between the higher efficiency of switching power supplies and lower noise of linear styles makes sense. Switching power supplies just can’t offer low enough ripple for certain applications. A simpler design and lower part count also makes mean time between failures another key advantage of linear designs over the more complicated switching-mode construction.

Key applications for linear power supplies: Simply stated, linear power supplies are an ideal choice when output noise must be kept to a minimum. Applications such as high-end audio equipment, lighting designs such as LEDs, sophisticated sensors, and redundant power for power generation scenarios are all prime candidates for linear power supplies due to their minimal noise output and low ripple. Medical equipment also requires linear power supplies as well, though there are only a few products on the market certified to meet industry standards for patient and operator protection. The key is choosing the right power supply for the type of load in question, and balancing efficiency needs with noise requirements.


Learn more about linear power supplies for medical and other uses