The simplistic Salas low voltage shunt regulator - Page 460 - diyAudio
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Old 6th November 2011, 12:08 AM   #4591
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Yes, i have agnd and dgnd planes coupled at some point. My question was more related to the fact the my salas shunt reg will be placed in an area where there is a gnd plane running. It feels a Wrong to have s0 and f0 traces running through the ground plane and then connecting to it near the chip after running an inch or so as traces. Sort of counteracts the logic of using a ground plane in the first place (shortest current loop).
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Old 6th November 2011, 04:29 AM   #4592
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Quote:
Originally Posted by studiostevus View Post
Yes, i have agnd and dgnd planes coupled at some point. My question was more related to the fact the my salas shunt reg will be placed in an area where there is a gnd plane running. It feels a Wrong to have s0 and f0 traces running through the ground plane and then connecting to it near the chip after running an inch or so as traces. Sort of counteracts the logic of using a ground plane in the first place (shortest current loop).
Why is that ? there is little current in the sense wires, and they are not really part of the Ground, .... your ground plane still makes sense for the "real" ground currents.

This is the very principle of the sense circuit actually...

To simplify the principle: your connecting wires have a non null impedance, which the shunt reg does not know (the active device/circuit regulates the voltage it sees at its pins,...).
Because there is a significant current running in the wires , it can affect the voltage regulation at the load (U=R.I so Voltage drop in the wires can be significant).....
The sense wires bare very little current, so the voltage loss across them is negligible, and you measure very accurately the voltage at the load. (~ like separating the wires that carry the current to the load from the ones that measure the voltage )
This is especially useful if you are running several feet of wire between your reg and your load.
If your load is close to the Reg, I would not lose sleep over it though, and you may even ignore the sensing circuit (pay attention, though, you MUST connect the sense wires somewhere, but it can be on the Reg PCB directly, or at the regulator terminals... ). What I did in my Pcb is put an optional jumper that I can close if I don't want to bother with 4 wires

For your ground plane, don't worry too much anyway.. for this particular circuit, I don't think it's very critical (and I don't think the BiB or DCB1 are using one, and they're working perfectly well with lots of happy users )

Fred

Last edited by Lazybutt; 6th November 2011 at 04:32 AM.
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Old 6th November 2011, 04:23 PM   #4593
AndrewT is online now AndrewT  Scotland
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Why are you using a Ground Plane?
What does the Ground Plane Achieve?
What does the Ground Plane prevent?
Do you know how to design your Ground Plane to meet all those requirements?

So, I'll ask the same question again:
Why are you using a Ground Plane?
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Old 6th November 2011, 04:46 PM   #4594
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The ground plane is used for the DAC section of the PCB... based on what was said earlier, I have now settled to only have a ground plane under the DAC section, and not under the regulator section of the PCB. That way, I can run sense traces to the ground plane.
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Old 7th November 2011, 05:03 PM   #4595
back is offline back  Greece
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i increased current to my buffalo 5.5.volt 500ma and the heatsink is hot but you can barely touch it by hand.

the heatsink is 4k/C do you guys think i am ok or i need bigger heatsink?
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Old 7th November 2011, 05:09 PM   #4596
AndrewT is online now AndrewT  Scotland
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4C/W
how many Watts do you expect in normal operation? and still expect the circuit to perform as expected.
How many Watts do you expect in abnormal conditions? and still expect the circuit to recover undamaged after the abnormal conditions return to normal operation.
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Old 7th November 2011, 05:16 PM   #4597
back is offline back  Greece
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what do you mean abnormal operation.

it`s a dac and it draws 450ma so i gave a headroom of 50ma and setup at 500ma.
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Old 7th November 2011, 05:31 PM   #4598
AndrewT is online now AndrewT  Scotland
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the regulator has a "normal operational window".
It should be designed to allow good quality sound to be reproduced while in this "normal operation.

However the regulator can be expected to occasionally operate in exceptional conditions. Two examples: shorted output ! maximum input mains voltage.
These conditions can occur and I would expect my design to survive these incidents.

I would expect a manufacturer to replace equipment that failed to survive such incidents.

One of the beauties of a CCS Shunt regulator is that, designed properly, it is destruction proof.
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Old 7th November 2011, 05:43 PM   #4599
back is offline back  Greece
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and 500ma is too much?

i use irf9610 and irf9540
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Old 7th November 2011, 05:44 PM   #4600
AndrewT is online now AndrewT  Scotland
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You have not told us the dissipated power yet.
Current alone tells us effectively nothing.
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