Go back

DC/DC

DC/DC converters and voltage converters are plug-and-play voltage supply modules that can be used in a plethora of application fields. DC/DC converters fall into two major categories as determined by their main application area.

The first category consists of DC/DC voltage supplies that transform one DC voltage into another, with the output voltage as independent of load as possible while remaining immune to fluctuations in input voltage. The second consists of DC/DC isolation barriers that electrically isolate two circuits - for example, in interfaces.

While the first DC/DC application category is usually used for higher power output requirements, applications involving electric isolation of two circuits by DC/DC converter are usually around 1W, seldom higher. Various DC/DC module manufacturers have created a certain market standard regarding output class, construction form and pinouts, and many voltage converters have a very similar external appearance in practice. Finding the differences would necessarily involve testing each DC/DC module, which can be a laborious process. Normal static tests will reveal some differences in individual DC/DC converter models, but the differences only really become apparent when the modules are subjected to permanent load. This is normally the case when DC/DC converters are operated at high temperatures, either in static tests exposing the converter to hot and/or humid conditions, or in dynamic tests where DC/DC converters are subjected to temperature fluctuations that span the whole operating temperature range of the DC/DC converter in the space of a few minutes. Since hot operating conditions dramatically shorten the lifetime of a DC/DC converter (around an eighth of the usual lifetime of a DC/DC converter operated at room temperature), these tests provide a rapid way of finding out a DC/DC converter's lifetime and aging qualities. Usually, the values MBTF (mean time between failures) and MTTF (mean time to fail) are quoted as a guide to the lifetime of a DC/DC converter. However, this calculated figure is highly dependent on calculation regulations applied.There are three methods used for calculating MTBF in DC/DC converters: 1. MIL HDBK 217F, which returns values that are relatively high, implying long lifetimes in DC/DC modules. 2. BELLCORE TR-NWT-000332, which is usually used for DC/DC converters with higher output specifications, and 3. SN-29500, which is especially used in German-speaking countries; this method returns values that are significantly lower than those returned by MIL HDBK or BELLCORE for DC/DC converters.