Problem with power meter design
Hello,
I am designing a power meter, using as power supply a LNK306-TN with buck topology and full rectification. From this power supply hang DVDD (digital part) and AVDD (analog part) (+ output), and AGND = DGND (- output).
As IC metering I am using ADE7753 (single-phase sensor).
Well, ADE7753 has two inputs V2N, V2P as fully differential voltage inputs. In all references from manufacturer they assume that reference voltage for these inputs is AGND = Neutral from AC. But this AGND is the same one that I have to use for AVDD (power supply for the chip), and equal to GND from power supply that I said before.
How can I resolve that?, because I think that I can not to shortcut Neutral with ground with this configuration.
Please, help me.
Comments
Your are right ;-)
I attach you three diagrams. Two of them are power supply designs and the third one is the part of power metering (AC 1-phase (Live and Neutral), 230V 50Hz).
The problem is that ADE7753 IC's manufacturer specifies that the maximum differential input voltage for input pairs V1P/V1N and V2P/V2N is +-0.5V. In addition, the maximum signal level on analog inputs for V1P/V1N and V2P/V2N is +-0.5V with respect to AGND.
Therefore I think that I have to design a power supply with output voltage referenced to Neutral.
Is it correct?
May you tell me if Design 2 could be improved on?
Thanks.
It is hard for me to answer your question, since the problem is more ADE7753 related. But I like the powers supply designed with full bridge rectifier, since the ADE7753 should be happier with a true GND, not a GND with huge voltage ripple.
Anyway, you have to consult with guys really understand ADE7753, hopefully they can give you very valuable suggestions.
sorry for not help you much.
Again, really appreciate using PI part.
Could you show me a simple schematic, that can help a lot for me to understand your question.
thanks a lot!