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The simplistic Salas low voltage shunt regulator
The simplistic Salas low voltage shunt regulator
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Old 24th May 2018, 12:37 AM   #7751
Salas is offline Salas  Greece
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The simplistic Salas low voltage shunt regulator
Scoping at the output should show a flat line. Maybe thickened by random noise but no ac patterns. Try two wire output mode too by linking F+ with S+ locally at the output connectors. You already have no separate F0s, but a star? That's not in the design. Maybe its half sensing over a wide loop area now and picks much noise (if it is not oscillating).
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Old 24th May 2018, 04:40 AM   #7752
sianturi is offline sianturi  Indonesia
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I'll try the 2 wire mode. Anyway, the plot at the output is 50 nanoseconds/div, so i think it's a random noise....
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Old 24th May 2018, 11:51 AM   #7753
Salas is offline Salas  Greece
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The simplistic Salas low voltage shunt regulator
Do 50us also
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Old 28th May 2018, 07:56 AM   #7754
sianturi is offline sianturi  Indonesia
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Hello Salas,

I measured again the 30V+ ripple. This time I set the oscilloscope in "normal mode" (before, I used: detect-peak mode) with 1X attenuation probe. I set the horizontal scale at 50us/div. I could see it is indeed a random noise. But the peak-to-peak amplitude is about 12mV. This is too high, right?

I tried using 2 wire method (connecting Force and Sense directly together at the regulator output), but still the same. So is it oscillating??

About the PCB ground star, I merely copy the Bipolar design for V1.2 shown in the post#1898. But anyway, I added K-Multiplier before the SSLV....

I'm trying to debug my regulator. Perhaps, first thing I do is to test only the V+ section (while disactivating the V- section) to see if the use of common F0 is the root cause? The load is aleph Ono (current consumption is about 110mA for the V+).
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Old 28th May 2018, 11:56 AM   #7755
Salas is offline Salas  Greece
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The simplistic Salas low voltage shunt regulator
If it does not have a distinct AC pattern riding on the line it isn't oscillating. 12mV thick line is too thick for random noise unless it is not coming out of the build but its picked common mode from the environment. Needs short return on the probe as you know. The "coil" pointy thingy. One good comparative clue is to power it off as it is probed and see if the random noise on the screen remains the same or not.
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Old 28th May 2018, 11:57 AM   #7756
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but generally what is the best noise observed on scope? straight line with random noise of 1mv or 0.5mv peak to peak?
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Old 28th May 2018, 12:22 PM   #7757
Salas is offline Salas  Greece
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The simplistic Salas low voltage shunt regulator
To be rivaling a scope's own baseline depending on the bandwidth when with the probe attached and shorted. The wider the BW the more self noise. 20MHz option selected is good to use in this case.
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Old 30th May 2018, 07:25 AM   #7758
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In #1894 for V1.2, I noticed that you take the regulator output directly from Zobel network. I did not do this for V1.2R in my pcb layout. Dooooh

Anyway, I searched in this thread about my problem, and found out that RCruz had 30mV ripple, and played a bit with the value of R & C for the zobel. Also noted that someone here recommended putting elco right at the output (ie between Force and Gnd).

I tried installing a 22uF elco right at the output F+ and Gnd, and the ripple went down to just about 4mV peak-to-peak. Can I further improve this by taking the voltage output directly from the zobel network (i.e. I have to change the position of the zobel network R13 and C3 in V1.2R, so that it is closer to the regulator output)?
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Old 31st May 2018, 03:54 PM   #7759
Salas is offline Salas  Greece
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The simplistic Salas low voltage shunt regulator
Does it show that ripple/noise when using a dummy load? Or when its on your application load? Does that figure change when powering it off and looking again at the scope?
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Old 7th June 2018, 08:34 AM   #7760
sianturi is offline sianturi  Indonesia
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Hello Salas,

After debugging my circut, I found out that the K-Multiplier does not work. It is actually adding noise, and one time I could see that at the output of the K-Multiplier (in this case is also the input of SSLV v1.2R), there was some noise riding on a 100Hz square waves. Dooooh So, I guess my K-Multiplier was oscillating.

I replace the K-Multiplier by just a small elco, and I'm down to 2mV pk-pk at the output of SSLV. Now, I'm happy! Guess I could put a C-R-C in front the SSLV to improve things a little bit. Thx for support, Salas! You're the best!
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