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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.