For a full wave rectifier, can it rectify an AC wave with a DC offset above the rated voltage of its diodes rated voltage if the peak to peak voltage of the wave is within its rated voltage? Like if you had a rectifier that with diodes that could work up to 10 volts, and you were rectifying electricity with 100 volts DC and a 5 volt amplitude sine wave ripple, would it work because the AC component is only varying by 10 volts?
Electronic – Full wave rectifier with a high DC offset voltage
diodesrectifierripple
Related Solutions
Either can work correctly if designed properly. If you have a dumb rectifier supply feeding a 7805, then all the rectifier part needs to do is guarantee the minimum input voltage to the 7805 is met.
The problem is that such a power supply only charges up the input cap at the line cycle peaks, then the 7805 will drain it between the peaks. This means the cap needs to be big enough to still supply the minimum 7805 input voltage at the worst case current drain for the maximum time between the peaks.
The advantage of a full wave rectifier is that both the positive and negative peaks are used. This means the cap is charged up twice as often. Since the maximum time since the last peak is less, the cap can be less to support the same maximum current draw. The downside of a full wave rectifier is that it takes 4 diodes instead of 1, and one more diode drop of voltage is lost. Diodes are cheap and small, so most of the time a full wave rectifier makes more sense. Another way to make a full wave rectifier is with a center tapped transformer secondary. The center is connected to ground and there is one diode from each end to the raw positive supply. This full wave rectifies with only one diode drop in the path, but requires a heavier and more expensive transformer.
A advantage of a half wave rectifier is that one side of the AC input can be directly connected to the same ground as the DC output. That doesn't matter when the AC input is a transformer secondary, but it can be a issue if the AC is already ground-referenced.
The ripple formula you have is an approximation and just to demonstrate that here's another: -
The formula used here is not too disimilar from yours but it more accurately shows the time and not the frequency as being the important factor. However, the article makes an error in stating the 10msecs should be used at 50Hz. When the diode stops conducting at the top of the cycle and when it restarts is slightly less than 10msecs.
But, in the article's credit, look at the final paragraph - small print indicating where problems with the formula might lie and of course the OP's example falls into this area where all bets are off.
In truth the decay of the voltage is exponential from the top of the peak and not-linear and this will make a difference too.
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Best Answer
No, you can't do that. If you have 5V peak-to-peak riding on top of 100V dc then two of the rectifier diodes will always be forward biased. The other two diodes will see a combined reverse voltage that varies from 95V to 105V. On the other hand, it really doesn't make sense to use a rectifier when the input voltage is always positive.