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Created November 13, 2011
Last modified June 07, 2017
Tags ac-to-dc   diode   time-constant  


A single diode plus a capacitor can be used to rectify AC into DC, but often with a lot of ripple at the output.


Vsrc and Rsrc represent a 12V, 60V voltage output, like you might find at the output of a small power line transformer.

D1 is a 1N4007 diode -- not a particularly fast diode, but it handles reasonable currents up to about an amp.

C1 is the capacitor that we rely on to store and release energy for much of the voltage cycle.

Rload represents our load circuit -- perhaps it's a linear voltage regulator, or maybe just a simple resistive load like a light bulb.

A few things to try in CircuitLab

Load the simulation by clicking "Open in editor" above, and then click "Simulate" at the bottom. Run a time domain simulation.

Output voltage ripple

Take a look at how much the output voltage wiggles even though it's supposed to be DC! You can try making C1 bigger to reduce the ripple, but in the real world that's more expensive.

Try changing the load Rload, and see how this alters the output voltage waveform.

You can also replace Rload with a current source, which might better represent how something like a linear voltage regulator might look to this circuit.

Advanced experiments

You can also try to simulate the "inrush current". You can do this by editing Vsrc and setting phase to -90 degrees, which means the voltage source starts at its highest value, and then inserting a time-controlled switch to close at time zero in series in between Rsrc and D1. Now, run the transient analysis, but also plot the current through the diode D1. Check out the big current spike at the beginning of the first cycle!

See also

Diode full-wave rectifier:

AC Power Supply (Transformer and Bridge Rectifier):


Thanks, helped me alot

by kandongasd
July 10, 2013

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