In the book this form of half-wave rectifier voltmeter is introduced first and then the author says that there is a problem in this circuit: that when the AC source is in the reverse direction there is a chance that the diode may break-down causing damage to meter. I understand this part. Then he gives a modified version of this voltmeter:
Now he says that during reverse operation this D2 will be forward biased and there will be no problem.
But now there is a problem when the AC is positive, I mean this diode D2 can break-down in the positive operation. Nothing has been mentioned about this. I simply wanted to confirm: am I right in thinking so? And If I am not, what may be the reasons?
Best Answer
There is never more than a single diode voltage drop across either diode (disregarding the small voltage across the meter itself for sake of the discussion). In this configuration he diodes will not break down due to reverse overvoltage as for each half period one diode will be conducting.