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Converter 0V connection

throbscottle

Well-Known Member
If I have a buck converter (or boost, or cuk, or flyback, or forward, or whatever) does the converter's 0v connection become the main return path for whatever it's powering? Eg, if I was using a star ground, would I place it at the converter instead of whatever is supplying it?

Thanks, as always

If I have a buck converter (or boost, or cuk, or flyback, or forward, or whatever) does the converter's 0v connection become the main return path for whatever it's powering? Eg, if I was using a star ground, would I place it at the converter instead of whatever is supplying it?

Thanks, as always
In theory:
If your converter is "isolated", then no. You must connect the 0v as the "negative" of your secondary side.

If your converter is "non-isolated" then you can connect to anywhere along the 0v because it is all connected at the same potential.

But, since I haven't seen your circuit or even a schematic of what you want to do, don't blindly take my word for what you can/cannot do with your circuit.

It's hypothetical - the circuit that stimulated the question is non-isolated and everything is connected to a ground plane - but it got me thinking because of course the current passing through the converter's 0v node from the load is going to be different from the current passing through it's 0v node to the supply, potentially by a large amount, depending on how much of a voltage shift it's creating.

My reasoning is that as far as the load is concerned, the converter's output inductor is the power source, rather than the actual supply, so the return path for signals should go to it. The issue of course being that 0v is not all at the same potential, as the copper has resistance and inductance, either of which may or may not be relevant, depending on what the circuit does.

If I have a buck converter (or boost, or cuk, or flyback, or forward, or whatever) does the converter's 0v connection become the main return path for whatever it's powering? Eg, if I was using a star ground, would I place it at the converter instead of whatever is supplying it? Thanks, as always
The 0V connection (often referred to as ground or GND) of a DC-DC converter like a buck, boost, Cuk, flyback, or forward converter becomes the main return path for the circuit or system it is powering. This is because the 0V or ground connection of the converter serves as the common reference point for both the input and the output of the converter. In a typical setup, the converter's 0V connection becomes the main return path for whatever it's powering. For a star ground configuration, you would generally place the star point at the converter's 0V connection to ensure a stable and low-noise common reference.

In PCB designs, it's crucial to keep the ground paths as short and low-impedance as possible. The 0V connection of the converter should have a robust connection to the ground plane. Additionally, the input and output grounds should connect to this point in a manner that avoids high-current paths crossing sensitive signal grounds.
If you have further questions regarding the GND plane placement, you can check this Q and A thread.

> "if I was using a star ground, would I place it at the converter instead of whatever is supplying it?'
Yes, you want to choose your "star ground to be the shortest path to your converter output return sensed node. You also want that node to be low impedance for DC, AC or RF reasons to be a reliable 0V.

A "ground" by engineering definition means zero volts. There may be other "grounds" in a system such as Analog gnd or Digital gnd or RF ground. So notes and attention to layout details are necessary design details.
Different symbols are necessary and/or labels. So "ground" must be chosen by design in a new system or understood in an existing one.

Nice to have confirmation of what I had surmised - thanks!

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