Hi guys.
I've got one question.
I've got one IEC filter that I want to use in my power supply.
That PS contain two grounds DGND and AGND.
Both are tied together in one place via 0 ohm resistor (on another, separated board).
So which ground should I pick to connect it to IEC filter.
Should I connect it to power supply board or to board when ground are tied together (dac board etc.).
That connection should be direct or via 10-100ohm resistor (+ 100nF capacitor in parallel)?
Cheers.
I've got one question.
I've got one IEC filter that I want to use in my power supply.
That PS contain two grounds DGND and AGND.
Both are tied together in one place via 0 ohm resistor (on another, separated board).
So which ground should I pick to connect it to IEC filter.
Should I connect it to power supply board or to board when ground are tied together (dac board etc.).
That connection should be direct or via 10-100ohm resistor (+ 100nF capacitor in parallel)?
Cheers.
I assume you mean a can type AC inlet with a phase, neutral, and earth GND. Typically the Earth wire would connect to the chassis and usually to the secondary side grounds at a mounting hole if the PSU is EGND referenced and the enclosure is metal. You can determine if the secondary side is EGND referenced by measuring the resistance between the existing AC EGND wire and the secondary side GND. Regardless of whether it is connected or not use the same tie point ac the existing EGND wire. Typically this will be a mechanical ring terminal with a screw to a mounting stud.
Typically the lab type Powe supplies are floating supplies and usually have a separate EGND from the output GND.
Sorry if this is not answering your question. The choice to tie or not tie the secondary GND to EGND is usually EMI related. Get it wrong and you can make the noise worse instead of better. If I were doing it I would start at the AGND/EGND tie connection as my first choice. The I would move it to the digital GND and the as a last resort to analog. The trick is that there can be switching noise from the power supply that can be directed through the GND point what you are doing is allowing an alternate circulating path for current to return that may make thing worse instead of better. Sorry for the rambling post.
I hate Noise!
Typically the lab type Powe supplies are floating supplies and usually have a separate EGND from the output GND.
Sorry if this is not answering your question. The choice to tie or not tie the secondary GND to EGND is usually EMI related. Get it wrong and you can make the noise worse instead of better. If I were doing it I would start at the AGND/EGND tie connection as my first choice. The I would move it to the digital GND and the as a last resort to analog. The trick is that there can be switching noise from the power supply that can be directed through the GND point what you are doing is allowing an alternate circulating path for current to return that may make thing worse instead of better. Sorry for the rambling post.
I hate Noise!
Yep, it's all about AC inlet.
That inlet is connected with chassis directly, but I want to connect PCB to that filter via wire.
But really don't know which ground to pick.
My PSU is typical, linear power supply.
That inlet is connected with chassis directly, but I want to connect PCB to that filter via wire.
But really don't know which ground to pick.
My PSU is typical, linear power supply.
OK... run a 1mm insulated wire (or 18AWG for US) from the same screw point to the secondary side AGND/DGND tie point. I try and preserve the color scheme so that it is easy to identify that this is a EGND wire and not something else. Add shrink wrap to that wire because you are stretching across the primary/secondary side boundary.
The only purpose for a connection from Audio Ground to Chassis is Safety.
If there was a catastrophic failure that allowed Mains Live to touch a part that is normally isolated, then that fault current must pass easily back to Protective earth. The current that flows prior to the fuse rupturing can approach kA (1000A).
The point you choose to connect to chassis must be capable of passing that fault current.
The Centre Tap of the mains transformer has big wiring. The Power Ground has big wiring. The Return Terminal for the speaker has big wiring.
Any one of these could be used for your Safety connection to Chassis.
If you have a dual secondary transformer feeding into separate dual rectifier PSUs, then the CT is not available and the Zero Volts junction between the two PSUs becomes your big wire node.
The PE wire to Chassis will be at the input IEC socket.
The Audio Ground to Chassis will be at the location of the point you choose. It does not go via a long wire back to the PE.
If there was a catastrophic failure that allowed Mains Live to touch a part that is normally isolated, then that fault current must pass easily back to Protective earth. The current that flows prior to the fuse rupturing can approach kA (1000A).
The point you choose to connect to chassis must be capable of passing that fault current.
The Centre Tap of the mains transformer has big wiring. The Power Ground has big wiring. The Return Terminal for the speaker has big wiring.
Any one of these could be used for your Safety connection to Chassis.
If you have a dual secondary transformer feeding into separate dual rectifier PSUs, then the CT is not available and the Zero Volts junction between the two PSUs becomes your big wire node.
The PE wire to Chassis will be at the input IEC socket.
The Audio Ground to Chassis will be at the location of the point you choose. It does not go via a long wire back to the PE.
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The usual advice is that the bolt used to attach safety ground to the chassis must not be used for any other purpose. Add another bolt at a convenient point on the chassis if you want to connect the circuit to the chassis.dtproff said:
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