Power Supplies, Rectifiers, Regulation, and Decoupling
From Wall Power to Clean Rails
Power conversion chain
Many systems begin with AC input or an unregulated DC source, then use rectification, filtering, and regulation to produce stable supply rails. Digital and analog circuits need power that is not only at the correct voltage but also low in ripple and noise.
Power-supply stages
Rectification
- Converts AC to pulsating DC
- Usually done with diodes
Filtering
- Reduces ripple
- Often uses capacitors and sometimes inductors
Decoupling capacitors
Small capacitors placed near IC power pins supply sudden current bursts and reduce local noise.
What is the main purpose of a regulator?
A regulator keeps the supply voltage within a desired range despite input or load changes.
Correct answer: Maintain a steady output voltage
Why are decoupling capacitors placed close to integrated circuits?
They supply transient current and shunt high-frequency noise to ground.
Correct answer: to reduce local noise
Which stage typically follows rectification in a basic DC supply?
Filtering smooths the pulsating DC produced by rectifiers.
Correct answer: Filtering
What is ripple?
Ripple is the unwanted AC component remaining on a DC supply.
Correct answer: residual AC variation
Design checklist for a supply rail
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1
Step 1: Define input source and required output voltage/current.
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2
Step 2: Choose rectification and filtering if converting AC.
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3
Step 3: Select a regulator with enough headroom and current rating.
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4
Step 4: Add decoupling and verify thermal limits.