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Power Supplies & Regulation

Converting and regulating electrical power for electronic circuits

Power Supply Basics

A power supply converts electrical power from one form to another to meet the requirements of electronic circuits. Most commonly, it converts AC mains power to regulated DC power.

Rectification (AC to DC)

Half-Wave Rectifier

Uses one diode, conducts on half of AC cycle.

V_dc = V_peak / π ≈ 0.318 × V_peak

Inefficient, high ripple

Full-Wave Rectifier (Bridge)

Uses four diodes, conducts on both halves of AC cycle.

V_dc = 2 × V_peak / π ≈ 0.636 × V_peak

More efficient, lower ripple

Filtering

Capacitor filters smooth the pulsating DC from rectifiers.

Ripple voltage = I_load / (f × C)

Larger capacitance = smoother DC output. Typical values: 1000-10000 μF

Voltage Regulators

Linear Regulators

Simple, low noise, but inefficient (excess power dissipated as heat).

Efficiency = V_out / V_in

Examples: 7805 (5V), 7812 (12V), LM317 (adjustable)

Switching Regulators

Efficient (80-95%), can step up or down voltage.

Types: Buck (step-down), Boost (step-up), Buck-Boost

Key Specifications

  • • Output Voltage: Desired DC voltage level
  • • Current Rating: Maximum current the supply can provide
  • • Ripple: AC component remaining in DC output
  • • Regulation: How well voltage stays constant with load changes
  • • Efficiency: Output power / Input power