Regulator Loss Cutter Circuit Diagram . Large input-to-output voltage differentials, caused by wide input
voltage variations, reduce a linear regulator`s efficiency and increase
its power dissipation. A switching preregulator can reduce this power
dissipation by minimizing the voltage drop across an adjustable linear
regulator to a constant 1.5-V value. The circuit operates the LT1084 at
slightly above its dropout voltage. To minimize power dissipation, a
low-dropout linear regulator was chosen. The LT1084 functions as a
conventional adjustable linear regulator with an output voltage that can
be varied from 1.25 to 30 V.
Without the preregulator (for a 40-V input and a 5-V output at 5
A), it would be virtually impossible to find a heatsink large enough to
dissipate enough energy to keep the linear-regulator junction
temperature below its maximum value. With the preregulator technique,
however, the linear regulator will dissipate only 7.5 W under worst-case
loading conditions for the entire input- voltage range of 15 to 40 V.
Even under a short-circuit fault condition, the 1.5-V drop across the
LT1084 is maintained.
Regulator Loss Cutter Circuit Diagram
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