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SSLV1.1 builds & fairy tales
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Old 12th December 2012, 12:42 PM   #2031
samoloko is offline samoloko  Bulgaria
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thank you Salas

I have In my Vref filter based on Leds 220 nF only and hear low level buzz but I doubt It Is from low value cap
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Old 12th December 2012, 01:29 PM   #2032
Salas is offline Salas  Greece
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SSLV1.1 builds & fairy tales
Buzz is usually some gnd loop nested somewhere in the full system. Takes tedious debugging. Also check with scope that the rail isn't acting up on something. Low Vref filtering for a purpose would demonstrate as higher white noise effect.
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Old 12th December 2012, 06:54 PM   #2033
samoloko is offline samoloko  Bulgaria
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thank you

BIB Is high quality universal regulator
I see that some users hype 1.2R regulator - can It be set for 5 to 24 Vdc
which sounds better
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Old 12th December 2012, 07:38 PM   #2034
Salas is offline Salas  Greece
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Not necessarily, I know people who prefer 1.1 and others the Reflektor. They all got their best synergy applications area, and subjective preference is a non quantifiable term.
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Old 14th December 2012, 02:04 AM   #2035
Billc is offline Billc
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Hi Salas,
I have built several positive and negative regulators using the recommended boards. I have noticed that the negative regulators do not have stable output voltage with respect to varying loads at high shunt currents (4-500mA through the shunt). Do I need to adjust some components or should I lower the current source to allow 100mA or so through the shunt? My load is 100mA and I currently am running 600mA from the current source.
Please advise.
Thank You,
Bill
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Old 14th December 2012, 03:17 PM   #2036
Salas is offline Salas  Greece
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Much spare current slips the phase margin more with the semis used in the negative polarity. Solder another 1 Ohm across the R7 to see if something changes. But first check the rail with the scope to see there is no oscillation issue giving the instability. If its a DC line without waveforms riding and lessening R7 does not help, stick a 100 uF across the sense terminals on output connector. Last resort is you try use significantly less spare current.
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Old 15th December 2012, 11:37 AM   #2037
samoloko is offline samoloko  Bulgaria
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Default best film type cap that BIB can handle

I am looking to buy some films for Vref and Vout
I am struggling between Auricap and Sonicap
would you recommend which can be better to power line aplication - UGS V3
of course you can recommend some other brand
I would like to use Obbligato Gold but It Is so long
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Old 15th December 2012, 02:41 PM   #2038
Billc is offline Billc
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Quote:
Originally Posted by Salas View Post
Much spare current slips the phase margin more with the semis used in the negative polarity. Solder another 1 Ohm across the R7 to see if something changes. But first check the rail with the scope to see there is no oscillation issue giving the instability. If its a DC line without waveforms riding and lessening R7 does not help, stick a 100 uF across the sense terminals on output connector. Last resort is you try use significantly less spare current.
Thank you for the recommendations Salas.
Lowering the resistor at R7 to 1/2 Ohm and then shorting it out both improved the change in voltage. Shorting out R7 was better. My current output cap is a 10uf film (C104). 100uf across the output causes the voltage change with varying loads to be insignificant. I will experiment with different output capacitors in place of my current 1 Ohm/ 10uF film Zobel.
Another possibility is to add some electrolytics to the circuit that I will be powering and leave the Zobel in place on the regulator circuit board.
My final choice is to lower the current sours down to 200 mA but I like to run it hot.
Am I on the right track??
Bill
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Old 15th December 2012, 02:43 PM   #2039
Salas is offline Salas  Greece
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You are on the right track. Do you have an oscilloscope?
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Old 15th December 2012, 04:14 PM   #2040
Billc is offline Billc
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I do. I have oscillations! I should have checked that first.
Lowering R7 makes them worse. The output cap changed to 100uF improves things but only loading the supply down so that 100 mA is shunted by the transistor makes it go away... and then the voltage is stable. I varied the output cap from 47uF to 1800uF and found 1800 to be much worse. 100uF is best.
Here are my choices as I see them:
I can now run the CCS at 500 mA, let my circuit draw 100 mA and add a resistor to draw 300 mA. Then the shunt transistor will dump 100 mA. Or, lower the CCS to 200 mA.
The other option is to build another positive regulator and use it for the negative supply by connecting the positive output to ground. I have all isolated supplies so that will not be a problem.
What do you recommend?
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