Adjustable 3 Ampere Regulator

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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