Bridge rectifier question

Thread Starter

DougB

Joined Sep 11, 2010
24
My project requires that I be able to power it with a 12 VDC supply. My 12 VDC can come either from a battery or a rectified AC source depending on the availability of a source. If I connect a battery directly to the output of the bridge rectifier (no AC available on the input of the bridge), do I hurt anything((bridge, battery, transformer) or do I need to isolate the bridge when the battery is used?
 

#12

Joined Nov 30, 2010
18,224
That will work. Just connect the battery. A bridge rectifier will not let DC flow backwards through it.
 

radiohead

Joined May 28, 2009
514
You can also use the bridge rectifier as reverse polarity protection. Connect the output of the bridge to the circuit you want to protect, and the polarity of the DC input to the bridge doesn't matter, the output will always be correct.
 

thatoneguy

Joined Feb 19, 2009
6,359
The polarity protection is a good point. The only thing you need to remember is that you'll get about a 2 volt drop in voltage depending on the rectifier (1.5-2.3-ish volt drop from 2 diodes).
 

tyblu

Joined Nov 29, 2010
199
If the battery voltage is less than the peak AC voltage, it will have to be protected as well just in case they are connected at the same time. Another diode!
 
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