By combining a common 78L05 with an integrated audio amplifier of the
type TDA2030, an adjustable voltage regulator can be constructed in a
very simple manner that works very well. The output voltage is
adjustable up to 20 V, with a maximum current of 3 A. Since the TDA2030
comes complete with a good thermal and short-circuit protection circuit,
this adjustable regulator is also very robust. As illustrated by the
schematic, the design of this circuit is characterized by simplicity
that is hard to beat. In addition to the two ICs, the regulator contains
actually only two potentiometers and a few capacitors.
The adjustment is done by first turning potentiometer P1 to maximum
(wiper to the side of the 78L05) and subsequently turning trimpot P2
until the desired maximum output voltage is reached. P1 is then used to
provide a continuously adjustable voltage between this maximum and
nearly zero volts. At relatively small output currents there are no
specific requirements regarding the cooling. However, when the output
current exceeds 1 A, or if the input to output voltage difference is
quite large, the amplifier IC has to dissipate too much power and a
small heatsink is certainly appropriate.
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