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DC/DC converters

DC/DC converters are voltage converters that transform DC voltage at the input side into a different DC voltage on the output side. There are both electrically isolated and non-isolated forms of DC/DC conversion. Naturally, it is also possible to transform the input voltage to the same output voltage, with the DC/DC converter simply acting as an isolator. DC/DC converters are just as suitable for step-up conversion - transforming a lower input voltage to a higher output voltage - as for step-down conversion from a higher to a lower voltage. The important characteristics to watch for are DC/DC converter efficiency, derating, and line as well as load regulation.

Regulated DC/DC converters are the better option where a stable output voltage independent of load and input voltage is required. In contrast, the output voltage from unregulated DC/DC converters is just as subject to load (load regulation) and fluctuations in input voltage (line regulation). Electrical field-related and load-related interference caused by DC/DC converters are just as important in the choice of converter as the converter's immunity against electromagnetic field interference from outside.

A requirement for uncomplicated "plug-and-play" functionality can play a major role in deciding on a DC/DC converter; ground-up construction of the corresponding circuitry may be very time-consuming and expensive in development and testing, while a DC/DC converter delivers the required functionality to specification out of the box. The 2002/95/EC RoHS directive on the restriction of the use of hazardous substances, which is due to come into force in the middle of 2006, also affects DC/DC converters. Producing wired converters in compliance with the directive is a fairly simple matter, but SMD DC/DC converters pose a greater challenge - their hybrid construction involves certain restrictions in the later reflow process by the customer. RECOM has used the Jedec J-STD-020-C standard for orientation in order to cater to the broadest possible range of requirements.

Workmanship and especially factory testing on finished modules is also enormously important in DC/DC converters. Screening and burn-in tests should ensure that defects causing early failure in electronic products occur during the manufacturing process, and are filtered out before the modules are delivered to the customer. HALT (highly accelerated lifetime) and HASS tests (highly accelerated stress screening) should confirm the mechanical strength of the design at the development stage, while burn-in tests should ensure that DC/DC converters from mass production have the corresponding quality. These aspects are just as vital to the quality of DC/DC converters as the specifications given on the data sheets.