Information

13
1 Basics
1.1 DC/DC voltage converters
1 Basics
1.1 DC/DC voltage converters
A DC/DC converter (DC stands for Direct Current) converts an input DC voltage into a
regulated or non-regulated DC output voltage which can be higher or lower, inverted or
non-inverted and isolated or non-isolated.
DC/DC converters are added in the circuit where downstream electronic circuits/
components require voltage levels that differ from the available voltage at the source.
For example, a 24 VDC truck battery cannot drive a radio or UHF transmitter in a car,
as the voltage of 12 VDC is required in this case.
Today, DC/DC converters are part of almost all electronic products, such as phones,
laptops, tablet computers, notebooks, routers, printers, TVs, lighting control devices
etc.
For the developer, the specification and selection of a DC/DC converter is crucial prior
to its use in order to ensure the correct operation of the product and to be sure that
the final product does not constitute a hazard for the user.
Different applications call for different DC/DC converter requirements and therefore
various converter topologies and controllers are necessary to cater the needs.
The basic function of a switching regulator can be described as “taking energy from
the input source and passing it to the load, while maintaining the output voltage level
appropriate for the load”. The input capacitor is charged up to the input voltage. An
inductance is used as an energy storage element energy and to limit the current flow.
The cycles are generated by an electronic switch which is periodically controlled with a
square-wave signal. The ratio of the On and Off phases of the switch also determines
the ratio of the input to the output voltage. The output voltage is present at the output
capacitor and supplies the load. Depending on whether the inductance was imple-
mented in the circuit (topology), the output voltage may be higher or lower than the
input voltage.
Another simplified explanation of the function of a buck regulator is also applicable. An
AC voltage is generated from the DC voltage at the input of a regulator by cycling. A
filter (inductance + capacitance) then converts this back to a DC voltage with another
amplitude.
The switching converters are broadly categorized as isolated and non-isolated convert-
ers. They are sub-categorized as follows:
Square-wave signal