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Interpreting Complex Data Sheet Specifications—Part III

For the third installment of our ongoing series on interpreting power supply data sheets, we turn our attention to thermal specifications. Despite demands for higher power and wider input ranges, customers still want their power supplies delivered in small packages. As a result of this demand, engineers have to come up with creative ways to avoid overheating.

Here’s how the addition of information on thermal management solutions, such as heat sinks, adds to the length and complexity of data sheets:

 

 

Current Limiting Versus Heat Sinking. Current limiting the output and heat sinking are the two most common ways engineers avoid overheating in power supplies. Deciding which one to use often boils down to operating environment:

  • Current limiting is a feature that can be built into the circuitry of a power supply, whereby resistors on the PC board limit the amount of current emitted by the transformer. Because this method requires free air convection, however, it cannot be used in enclosed environments.

  • Heat sinking. This option eliminates heat from inside the power supply by dispersing heat and improving energy use. Adding the heat sink to the outside surface allows for a more direct airflow to reach the direct source of heat. This method radiates heat so it doesn’t get trapped inside and overheat the power supply. While heat sinking also relies on free air convection, there are special cases where the power supply can be made with a base plate that functions as the heat sink. This allows the unit to be used in enclosed environments with limited to no airflow, including oil refineries or other applications that involve toxic material or explosive gas.

Effect On Data Sheets. Data sheets need to reflect all the thermal specifications you need to properly design your power supply. For one, power supply manufacturers often have to test for different thermal environments—the results of which must be listed on the data sheet.

Each new thermal management solution—whether current limiting or heat sinking—must also be listed alongside a mechanical drawing. Bear in mind too that each solution can be delivered a number of ways. For example, manufacturers can provide heat sinks with clamps or without, or sometimes heat sinks can be built into the bottom of the package. Listing all of these variations, along with the drawings and test results, takes up a significant amount of real estate on the data sheet.

Stay tuned for more on this series. In next month’s blog post, we’ll delve into packaging specifications. In the meantime, sign up for our newsletter (left-hand toolbar) to receive updates by email.

 

Interpreting Complex Data Sheet Specifications—Part II

In our ongoing series on interpreting complex data sheets, we turn our attention this month to electrical specifications. The need for products to be electrically interchangeable, in addition to meeting specialized industry standards, are the two trends affecting the length and complexity of power supply data sheets. Here’s how:

Electrical Interchangeability. Rather than invest in separate devices to meet the requirements of different applications, nowadays customers are looking to invest in one power source. This need for interchangeability boils down to simple economics: customers want to do more with less devices, which puts pressure on power supply manufacturers to design products that can fit a variety of potential applications.

To be more versatile, power supplies, for one, have to include more voltage combinations. At Polytron, a product series that used to have only 15 models now has well over 50 to account for the new voltages. Secondly, manufacturers now have to offer power supplies with variable voltages in addition to offering fixed-voltage devices. Having a variable voltage lets users adjust the power output to their preferred level, allowing the device to be used across more applications.

Keep in mind also that not only do data sheets have to list each new electrical specification, but sometimes the information has to be represented as a mechanical drawing or graph. It’s no longer enough to simply list a unit’s output voltage, for example. Now, customers want to see a graph that illustrates the relationship between a device’s output voltage and its temperature range.

 

 

Meeting Specialized Electrical Standards. In addition to being interchangeable, power supplies, at the same time, have to meet many specialized requirements. This includes undergoing rigorous, application-specific electrical testing.

Consider the EN 50155, which outlines the specifications of electronic equipment used in railway applications. This standard requires that power supplies have wider input voltages, including a range of 43 to 160 Vdc, as well as pass various tests related to electrical insulation, power surges, ESD, voltage transients and more. The medical industry also has its fair share of tests, most of which are related to EMI, leakage current, immunity and voltage isolation. Tests like the Hipot (high potential) test, which verifies a device’s electrical insulation, are intended to protect patients coming into direct contact with medical equipment.

While many of these power supplies were already manufactured to industry standards, manufacturers are now required to list the various tests and results on their data sheets.

Despite the demands for higher power and wider ranges, customers still want small packages, causing power supplies to run the risk of overheating. Stay tuned for more on this topic, which we will discuss in next month’s blog post on thermal specifications.

In the meantime, sign up for our newsletter (left-hand toolbar) to receive updates by email.

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.

More on power supply specifications. Stay tuned for more on power supply data sheet specifications or sign up for our newsletter (left-hand toolbar) to receive updates by email.

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. 

P3P5MHIA

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.