DC to DC converter IC that changes "reference point"

Dec 16, 2005 5 Replies
I

Let's say that I have a source of DC signal that is referenced to a particular point (which is tied to an AC line 240 VAC floating potential).



I would like to get a DC signal that is the same as the original (I only need milliamps and it would be under 1 volt), but referenced to ANOTHER point (equipment ground, say).



So, in the AC world I could get by with using a little transformer. Is there a simple IC in the DC world that would do the same?



Perhaps an optocoupler with some extra functions to account for low current trafer ratio, would be helpful.


i
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I

INA117 is basically a perfect solution for me, EXCEPT that the common mode voltage is 200V and I deal with 240VAC. If I could find something similar with common mode voltage of say 500 VDC, I would be delighted!

i

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I

I found AD629, which goes up to 270V, but I suspect that even that is not enough for 240 VAC common voltage.

i

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I

I am wrong. If common mode voltage for my voltage sensing is always tied to either leg 1 or leg 2 (not to the third leg), then I have no need to worry -- the voltage reference to ground is not more than

125VAC. INA117 or AD629 would work just fine. Thanks Al.

This is for my phase converter.

One thing that I wanted to measure was voltage difference between leg

3-1 and leg 2-1 (it is a measure of out of phaseness), which would have a reference voltage of 240VAC or more. Maybe I can get around it by using two such amplifiers that would be tied to legs 1 and 2. i
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T

Well if the new reference point is has no galvanic isolation from the mains then look for a differential amplifier such as an INA117 or so. If the signal must be galvanic islolated try an isolation amplifier such as the HCPL-7800.

Al

"Ignoramus20852" Wrote news:NgBof.54066$ snipped-for-privacy@fe49.usenetserver.com...

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S

Use a high voltage transistor and a floating supply to make a current source,which current goes into a resistor at your other level. I did that once in a full bridge power amp for a 40amp dc motor ,to sense the motor current. We needed that to make a force feedback at a steering wheel.

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