When choosing a DC-DC converter, it
is crucial to consider the output load power requirements of the system, which
include the output voltage and current supplied by the converter. The output
voltage may have tolerance specifications that depend on environmental
conditions, such as input voltage, output load current, and ambient
temperature. The load current requirement specifications should include the
minimum, maximum, and typical values.
Unlike AC-DC power supplies, input
voltages for DC-DC converter applications are not standardized. Therefore, it
is necessary to specify the range of input voltages that the converter will
receive.
DC-DC converters can be isolated or
non-isolated. Isolated converters have no DC path between the input and output
circuits, and they are often used to separate the input and output circuits for
electrical noise or dangerous voltage isolation. Isolated converters can have
multiple output voltages from a single converter. Non-isolated converters, on
the other hand, have a DC connection between the input and output through the
common ground between the input and output circuits. They can be smaller and
less expensive than isolated converters and can produce a negative output
voltage from a positive input voltage.
Most DC-DC converters produce a
tightly regulated output voltage, similar to AC-DC supplies. However, smaller
or less expensive converters can be used in applications that can tolerate an
unregulated output voltage. The selection of a regulated or unregulated output
voltage is often available only on low-power converters.
EMI and EMC (Electromagnetic
Interference and Electromagnetic Compatibility) regulatory requirements are
important for most electronic products offered for sale. DC-DC converters can
be certified to comply with regulatory requirements, but the completed system
is certified in most applications, and the internal sub-circuits do not require
certification.
Similarly, most electronic products
sold are required to meet regulatory safety requirements. Products are granted
safety certification for the final product, and certification is often not
required for the internal sub-components but can be obtained if necessary. It
is essential to note that DC-DC converters sold in the EU and UK with input
voltage ratings of 75 V or greater require safety certificates, so it is
important to check for other geographic locations. Safety certifications for
converters should also be obtained if the DC-DC converters are used for
isolating users of products from hazardous voltages.
Other features, such as the ability
to adjust the output voltage with external resistors or load voltage sense
terminals, can be beneficial or required in product designs. Including remote
on-off capability allows designers to enable or disable the output voltage from
the converter with an electronic signal.
Knowing the basic issues associated
with DC-DC converters can help to simplify the selection process of these
components. There may be other considerations when selecting converters in
addition to those discussed above. By working with an experienced power supply
company, such as Landworld, the effort required to complete the selection
process can be minimized, and optimal DC-DC converters can be identified.
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