Open Diode Bridge Rectifiers

When 1 of the 4 diodes of a bridge rectifier opens what happens to the following? 1) The output voltage? 2) The ripple voltage? 3) The ripple frequency? Also how can you measure the ripple frequency to determine if a diode were open in a bridge rectifier circuit?

I disagree with in Colin in that when one of the diodes open the full wave bridge circuit now becomes a 1/2 wave rectifier. I would expect to see a 50 percent drop in voltage along with a ripple frequency of 60 hertz instead of 120 hertz. I would also expect the output ripple to increase.

for a full wave bridge Vo = .693 Vpeak
1/2 wave rectifier Vo = .318 Vp


One thing to remember though when the output of the rectifier is fed to a capacitor (filter) the average output voltage and ripple will change will change, output voltage Vave will go up and the ripple voltage will go down, but the ripple frequency will remain un-changed.

As for measuring the ripple frequency - need a oscilloscope or a frequency counter ( some DMM have this function).

when 1 of the bridge diode rectifier is open,
1. the output voltage decreases by 25 % or less
2. the ripple voltage missing the positive half cycle of ac sine wave
3. the ripple frequency reduced by 25%

the ripple frequency can be measure by using an oscilloscope test instrument

Well done, Peter, you got the engineers here to do your homework for you AGAIN.

Engineers ! You do not help students by answering the _whole_ question for them !
The wording of the question tells you it is _straight_ from the classroom !

Let's assume the question refers to the bridge rectifier output with no filter capacitance.

1) The RMS voltage decreases to 70%

2) The peak-to-peak ripple voltage does not change.

3) The ripple frequency is 1/2

An open diode in a full-wave bridge rectifier will produce the same symptoms as in the center-tapped circuit. The open diode prevents current through the load resistor during half of the input voltage cycle. The result is half-wave rectification, which produces double the ripple voltage at 60 Hz.