Full Bridge and Voltage Comparision

Could you just wire the rectifier outputs in parallel, and not worry about it?

Cheers

Phil Hobbs

For sensing the current through each bridge for comparison, I would delete D1 and D2, then place current - sense resistors in series with the ground connection to each bridge.

--Winston

How would you compare the current from each bridge?

--Winston

Homework?

Looks like it. Not enough detail if it were a _real_ two source situation. ...Jim Thompson

not a homework at all

Melissa

Could you tell us why you need to know this information?

Please. Like what is the application? ...Jim Thompson

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As others have said, you can get rid of D1 and D2. Their function is already being provided by the right two diodes in each rectifiers.

Now, instead of connecting the anodes in the rectifiers directly to ground place a shunt resistor into those connections. Both of them. Calculate the resistor so that at nominal load you get a voltage drop you can easily measure. If you use a comparator such as the LM339 then

Now you can compare the two and find out which source contributes more. You could also use meters or AD converters to find out the ratio. When the sources are within about a volt of each other then both will contribute some.

Remember that the signal on that shunt will pulsate at twice the input frequency.

If the 2 bridge outputs are reasonably similar, the simplest way is load each in turn with a resistor and measure the resistor's temperature rise - DMMs with K-type thermocouples are quite reasonable these days.

Melissa the OP, yes? (Emphasis mine):

"I am trying to *compare the magnitude of the DC outputs* of two full bridge rectifiers."

"Based on the magnitude of the DC output, *I have to decide which bridge will be providing power* to the load as shown in the link."

"I posted the circuit at the following link *to compare the two output voltages*"

I didn't get that from her post. :)

--Winston

AFAIU Melissa wants to know which bridge is currently driving the load. If that is so then she needs a signal that tells her.

It depends how the AC sources are correlated with one another and with the circuit ground, it also makes the assumption that you want to drw power from the source with the greatest amplitude.

also D1 and D2 serve no purpose, as they only duplicate the functionality of the diodes on the right half of the two bridges. the could be omitted (replaced with wire)

Unless someone else does her homework for her ;-) ...Jim Thompson

How much of a voltage difference of detection are you looking for?

Jamie