A diode gives current a preferred direction.
In a simple model, a diode conducts readily in one direction and resists current in the other. Real diodes have a forward voltage drop and limits on current, temperature and reverse voltage.
Rectifier circuits use this directional behaviour to turn alternating input into an output with one polarity.
Rectified does not mean smooth.
A half-wave rectifier uses one half of each input cycle. A full-wave rectifier uses both halves; a bridge arrangement steers current through the load in the same direction on each half-cycle.
The result is pulsating DC. Rectification alone does not make the output voltage constant.
Three different functions.
- RectifyMake the output polarity consistent.
- SmoothReduce variation between pulses.
- RegulateControl the output around a target value.
A smoothing capacitor can supply a load between charging pulses. A regulator responds to changing conditions to keep the output within its specified range.
Linear and switch-mode supplies.
A linear supply may use a mains-frequency transformer followed by rectification, filtering and regulation. A switch-mode supply controls energy transfer using rapid electronic switching.
Many switch-mode designs include a high-frequency transformer; others are non-isolated. The full design determines the isolation and protection provided.
Think of the supply and load together.
If the load takes 0.5 A steadily, it receives 12 W. A supply rated to deliver 2 A does not normally force 2 A through that load.
Lift controllers and sensors can depend on a common DC supply. Loss of several signals could therefore involve the supply or distribution, rather than several unrelated failed sensors. Actual diagnosis needs the installation’s documentation.
A closer look
Ripple is variation remaining on a DC output. In a simple single-phase full-wave rectifier supplied at 50 Hz, rectified pulses occur at 100 Hz. That is different from the switching frequency in a switch-mode supply.
Check your understanding
Is a rectifier alone enough to give perfectly steady DC?
Reveal the explanation
No. Its output can be pulsating. Smoothing and regulation perform additional functions.