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Old 7th October 2012, 10:26 PM   #11
BZed is offline BZed  United States
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You are correct dirk. Thats a series regulator.
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Old 7th October 2012, 11:55 PM   #12
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To me it looks like a series reg,with a fixed ~1-2V drop,depending on the LED chosen (it might even be better to use two LED's in series,larger Vdrop,and higher dissipation,but more 'headroom') with a MOSFET shunt reg following it.
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Old 8th October 2012, 12:40 AM   #13
BZed is offline BZed  United States
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I was refering to the Kubota Regulator.
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Old 14th January 2013, 09:08 AM   #14
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Hi,

I've got a couple of Kubota regs that I would like to modify for better noise without sacrificing output impedance. Here's the diagram for one of them :

Click the image to open in full size.

which is sold here :

HIGH SPEED LOW NOISE MOSFET POWER SUPPLY REGULATOR KIT! | eBay

and the other is the one from Jim's audio. It uses constant current diodes so it looks far simpler, like this below, but its really the same thing.

Click the image to open in full size.

My main query is about inserting an RC filter after the voltage reference (D1 and D2 in top diagram) to filter noise into the error amplifier. Will this affect output impedance ? My brain says yes, but I don't trust it completely.

The other option is to increase Vref by using 2 LM329 in series instead of using gain. Is this design stable with unity gain ? Does it need a small cap to bypass the output feedback resistor for unity gain stability ?

For sure I know that the Vref's zener has a low impedance so the filter cap needs a film cap bypass to filter noise.

Are there any LT Spice sims for this circuit ?

Thanks,

Tom

Last edited by KlipschKid; 14th January 2013 at 09:22 AM.
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Old 14th January 2013, 10:09 PM   #15
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I think a more effective way to filter the noise would be to bypass the 220uF/16V electrolytics with multilayer ceramic capacitors. I would also replace those electrolytics with 22uF tantalums.
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Old 14th January 2013, 11:36 PM   #16
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Hi Dirk,

Thanks for the advice. I don't see any reason to use big electro's either. I thought about a film bypass for them but actually, a tant and a ceramic together would probably be far more effective.

I've been turning this design around in my head and actually I think the RC filter on the zener reference won't affect output impedance - it's not part of any of the output-feedback loop. Plus it'll give the psu a soft start.

I still can't figure out if it will be stable without gain - I think probably not. I've been looking at other series regs with unity gain and at least one uses a compensation cap - AMB's Sigma11 (C16 in his schematic).

Anyway, it's a beautifully simple design. To me, it shows some real lateral thinking and it's only real weakness is noise.

Cheers

Tom
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Old 15th January 2013, 08:54 AM   #17
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Quick update - all the changes work as expected except the unity gain. In fact it needs a little gain or it floats.
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Old 15th January 2013, 09:41 AM   #18
Salas is offline Salas  Greece
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Quote:
Originally Posted by CZ101 View Post
I have a similar question about this shunt regulator PCB on ebay. It ships from Indonesia and is described as "overstock Shunt Regulator PCB design by Mr. Salas". Any comments would be really helpful...
Its not an authorized PCB and it looks like based on an old version. Please don't support the copycats.
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Old 15th January 2013, 09:52 AM   #19
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Quote:
Originally Posted by Salas View Post
Originally Posted by CZ101
I have a similar question about this shunt regulator PCB on ebay. It ships from Indonesia and is described as "overstock Shunt Regulator PCB design by Mr. Salas". Any comments would be really helpful...

Its not an authorized PCB and it looks like based on an old version. Please don't support the copycats.
Support the group buy ! Get quality for your money....

GB Thread for Salas SSLV1.1 BiB shunt reg
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Old 15th January 2013, 09:53 AM   #20
Stixx is offline Stixx  Germany
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It looks like ripped from the older Quanghao boards...
tststs
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