AC-DC Converter with LM317

This is a AC-DC Converter with LM317 voltage regulator IC.
It converts an AC input into a stable adjustable or fixed 5V DC output using a full-wave bridge rectifier, filter capacitors, and LM317 regulator.

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Features

• Input: AC 12–15V (via transformer secondary)
• Output: 1.25V – 12V DC (adjustable) or 5V Fixed (depends on input voltage and load conditions)
• Maximum Output Current: 1A (need to add heatsink)
• Built-in fuse protection on AC input

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How It Works

1. AC to DC Conversion The input AC voltage passes through a fuse (F1) for protection.
   The bridge rectifier (D1–D4) converts AC to DC signal.

2. Input Filter Two decoupling capacitors:

   • Polarized Capacitor 1000µF smooths the rectified DC.
   • Non Polarized 100nF filter high-frequency noise input.

3. Voltage Regulation (LM317)
   The LM317 regulates the voltage according to the equation:
   

4. Output Filter Two decoupling capacitors:

   • Polarized Capacitor 1000µF smooths the regulator output.
   • Non Polarized 100nF filter high-frequency noise.

5. Load Output The regulated DC voltage is available at J2 connector pins.

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Design Notes

• Use a 12–18V AC transformer capable of at least 1A output current.
• The LM317 requires a heatsink for continuous load operation.
• Output voltage ripple depends on C1 and load current — for lower ripple, increase C1.
• Always ensure correct polarity before connecting your load.

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Applications

• Bench/lab adjustable DC power source
• Battery charging experiments
• Testing and calibration of small circuits
• Educational demonstration of linear voltage regulation