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1A Regulated DC Power Supply Using 78xx Voltage Regulators

This simple DC power supply provides a regulated output of up to 1A using the 78xx series voltage regulators. The output voltage can be selected by choosing the appropriate 78xx IC (e.g., 7805 for 5V, 7812 for 12V). The design is suitable for powering small electronics and hobby projects.

Power Supply Requirements

  • Input voltage: AC or DC sufficient for the chosen 78xx regulator (typically 2–3V above the desired output).
  • Output current: up to 1A, depending on regulator and heatsinking.
  • Filter capacitors to smooth DC voltage and reduce ripple.

Key Components

  • 78xx Voltage Regulator: Provides regulated DC output (select variant for desired voltage: 7805, 7812, etc.).
  • Transformer (if AC input): Steps down mains AC to appropriate voltage for the regulator.
  • Rectifier Diodes: Convert AC to unregulated DC.
  • Filter Capacitors: Smooth the DC voltage before and after regulation.
  • Heatsink: Required for the 78xx regulator to dissipate heat at higher currents.

Circuit Operation

  • If AC input is used, a transformer steps down mains voltage to a level suitable for the 78xx input.
  • Rectifier diodes convert the AC voltage to pulsating DC.
  • Filter capacitors smooth the DC voltage before it enters the 78xx regulator.
  • The 78xx regulator provides a stable, fixed DC output at the selected voltage, capable of supplying up to 1A.
  • Additional output capacitors can be used to improve transient response and reduce ripple further.

Key Features

  • Regulated DC output from 5V to 24V depending on 78xx chosen
  • Maximum output current: 1A
  • Simple and reliable linear regulation using 78xx series
  • Low ripple and stable output suitable for sensitive electronics
  • Easy to build and adjust for different voltages using different 78xx ICs

Construction Notes

  • Ensure proper heatsinking of the 78xx regulator for currents near 1A to prevent thermal shutdown.
  • Use adequate filter capacitance on the input and output to minimize ripple and noise.
  • If using AC mains input, verify transformer voltage is 2–3V above regulator output for reliable regulation.
  • Observe correct polarity when connecting the regulator, capacitors, and load.
  • Test the supply gradually under load before connecting sensitive devices.

Voltage regulators 7800 IC series