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Old 15th Dec 2018, 3:57 pm   #1
M3VUV51
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Default PSU using SG3532J.

Hi all. I'm looking for some help.

I've just got an SG3532J regulator IC and I'm after a PSU circuit for this. Any ideas where to look?Google comes up with zippo! Failing that does anyone know what changes have to be made to a 723 circuit to use it with this IC? The current limit part I can sort myself, just not sure what has to be altered for the other parts. Hope that makes sense.

Cheers, Paul M3VUV.
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Old 15th Dec 2018, 5:05 pm   #2
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Default Re: sg3532j psu

Some info here - https://www.digchip.com/datasheets/p...G3532J-pdf.php
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Old 15th Dec 2018, 5:14 pm   #3
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Default Re: PSU using SG3532J.

I was just looking. Would the attached circuit work if I played with the current sense resistor values to suit? Looking at the datasheets for the 723 IC and the SG IC the pinouts are pretty much identical.

Regards M3VUV,.

PS the SG chip was quite expensive so I don't want to fry it!
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Old 15th Dec 2018, 5:37 pm   #4
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Default Re: PSU using SG3532J.

That circuit isn't a bad design. At least it current senses on a separate resistor rather than just on one emitter resistor as many designs do.

Several thoughts:

10A is a bit light for amateur radio use, where 30A is more usual for 100W transceivers.

2N3055 is now a junk transistor, used as a dumping ground for anything which doesn't meet a higher spec by even reputable firms. If you buy from uncontrolled sources, you could get any sort of fake. This means you may get a fall out much faster transistor and have trouble with RF oscillation.

You need a crowbar. Your radio is likely far more expensive than the power supply and a power supply failure can apply enough voltage to ruin much of the radio circuitry.

723 and derived regs tend to be sensitive to RF getting into them. This can make theou output voltage go silly. Goor RF practice and filtering is advisable.

David
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Old 15th Dec 2018, 5:54 pm   #5
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Default Re: PSU using SG3532J.

Well to give you a clearer pic of what I have and what I am trying to do, I have 10 X 2N3773 pass transistors to use in place of the 3055's also an MC342P over voltage IC. The crowbar part etc is no problem, I've used the schematic I posted in the last post before and had R8 switched between 120 ohm and 10 kohm. That gave me two ranges going from about 3V low to about 28V high. In that one I used 6 pass transistors, the current foldback range didn't start until about 5 amps. The 723 needs 0.6V to go into current foldback, the SG 80mV. I'm trying to build a PSU that goes from about 3V to 30V say in two ranges and current limits from say 300mA to 30A, again in say a high and low range. Basically using the circuit attached but with my own mods to it and using the sg IC, I see no reason why it's not doable. My transformer is good for about 60A and my bridge rectifier is good for 180A.

Regards M3VUV.
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Old 16th Dec 2018, 6:43 pm   #6
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Default Re: PSU using SG3532J.

Still no answers to the original question! Doesn't anyone know? I didnt think I was asking the impossible!
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Old 16th Dec 2018, 8:41 pm   #7
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Default Re: PSU using SG3532J.

In the datasheet are some example circuits, and you can use it to compare the parameters to those of a 723.

See http://pdf.datasheetcatalog.com/data.../271221_DS.pdf
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Old 16th Dec 2018, 11:16 pm   #8
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Default Re: PSU using SG3532J.

I've built this Marchwood design, simplified and up rated to 50amps using six 50amp darlingtons on the output.

Bomb proof for over current / over voltage - had a custom transformer wound for it and 200,000uF of reservoir fed by two 50 amp bridge rectifiers

https://g4rvh.files.wordpress.com/20...marchwood5.pdf
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Old 16th Dec 2018, 11:32 pm   #9
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Default Re: PSU using SG3532J.

Quote:
Originally Posted by M3VUV51 View Post
Still no answers to the original question! Doesn't anyone know? I didnt think I was asking the impossible!
Perhaps everyone uses the 723 or else 3-terminal regs with added power assistance.

True the 723 current limit forces a less efficient series resistor, and yes the 3-terminal reg circuits are 'orrible, but I think the SG chip isn't much used.

David
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Old 17th Dec 2018, 12:32 am   #10
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Default Re: PSU using SG3532J.

Hi,

I have attached the power supply circuit schematic I found in a vintage military grade video monitor, that uses the 723 (there is also a mil equiv part number). The regulators are characterized by having a relatively high input voltage of 37.5 volts. Might be of some help to see how they wired them up. There is also the interesting SG1568 in there too. There is a clear to read version of the schematic in the article:

http://worldphaco.com/uploads/The_19...o_monitor..pdf
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Old 17th Dec 2018, 3:09 am   #11
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Default Re: PSU using SG3532J.

PEOPLE SEEM TO BE MISSING THE POINT HERE! I dont give a rat's ass about the 723, IT'S THE SG IC I need info on. Please read my first question, I will repeat it again. WHAT DO I NEED TO CHANGE IN THE SCEMATIC I POSTED TO USE THE SG IC? Forget about the current foldback/sense part of it, I can sort that, it's the voltage regulation part I'm concerned about.

Regards M3VUV.
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Old 17th Dec 2018, 3:51 am   #12
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Default Re: PSU using SG3532J.

Just have a look at the data sheet in post#7
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Old 17th Dec 2018, 7:11 am   #13
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Default Re: PSU using SG3532J.

M3VuV,

I'm not entirely sure why you feel the need to start ranting about the lack of response to your original query, regarding the use of a little known regulator IC, but I do think that the comments you have received so far would make even the most ardent supporter of differing circuit topography consider that the experience of others (some of who are professional design engineers) would carry some weight, and maybe would suggest that using a different component is sensible for a number of reasons.

If you have the datasheet for the SG IC, then read the application notes, try the circuits the IC manufacturer recommends, and learn it's capabilities from there.

Personally, I think I would draw from the years of experience and proven designs that have already been suggested.

Good Luck whatever you choose to do - I dont think getting all hot under the collar is going to help you though
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Old 17th Dec 2018, 7:59 am   #14
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Default Re: PSU using SG3532J.

Quote:
Originally Posted by Refugee View Post
Just have a look at the data sheet in post#7
Indeed - or even the one in post #2
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Old 17th Dec 2018, 9:37 am   #15
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Default Re: PSU using SG3532J.

Another point that is being missed is that it looks like no-one here has used the SG3523 before. I know I certainly haven't. If I had I would have immediately come under fire from the bosses, triggered by the higher price, wanting to know just why I hadn't used the good old LM...

So you would like to know what you'd need to change in the LM723-based design posted to be able to use a different control device and a different type of power transistor and up to ten of them?

To answer that question, I'd need to design a new circuit around your regulator chip and your power transistors and then compare what I'd come up with against the posted circuit. To have confidence in the new design, I'd want to build one, soak test it and look at the regulation when confronted with a dynamically varying load such as SSB and CW transmitters.

Here, I run into two problems:
1) I don't have any SG3523 or enough 2N3773 in my junk box, and they're quite expensive.
2) I already have a big 13.8v power supply to my own design and I don't need another.

I note that the asker of the original question hasn't done his own design from the information in the datasheet, which makes me think that any design around the SG3523/2N3773 for him would need to be done in full detail.

I also think the design needs to be thoroughly debugged and proven, otherwise the OP could wind up with a collection of destroyed semiconductors, such is the nature of large power supplies. It could even take out an expensive transceiver. Extrapolating from post 11, I wouldn't want to be on the same continent.

I suppose such a design could be put in PW or Radcom to get more value out of it than just a single PSU. Technical articles are in demand everywhere. But I can see an email coming from the editor, asking me to change it to use an LM723/2N3055!

In all seriousness, if you really have to use the SG3523, then it looks like you're going to have to design it yourself.

How to do that:

1) Find, read, and inwardly digest the "Marchwood power supply" article in Practical Wireless. It's one of the best designs published, but more importantly, the article has a good description of its design choices.

2) have a copy of Horowitz & Hill to hand as a good general guide to practical circuit design and development.

4) Build a big bank of load resistors. You don't want to test unproven PSUs into anything expensive.

3) Add a whacking great crowbar circuit to protect whatever it's powering.

4) Don't lose sight of the fact that this is a hobby and is supposed to be fun. Doing your own PSU can be very satisfying and can be good fun - and you can learn a lot from doing it.

David
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Old 17th Dec 2018, 10:31 am   #16
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Default Re: PSU using SG3532J.

Quote:
Originally Posted by Radio Wrangler View Post

1) Find, read, and inwardly digest the "Marchwood power supply" article in Practical Wireless. It's one of the best designs published, but more importantly, the article has a good description of its design choices.
That's why I posted the link to the Marchwood - good starting point and could be modified to accept the SG chip as most regulators which in a similar manner, ie voltage reference, comparator, driver and current sense.

Personally I think it'd easier and safer to rebuild into the Marchwood design.

But I concur best to test it on a DC dummy load before real equipment.
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Old 17th Dec 2018, 11:38 am   #17
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Default Re: PSU using SG3532J.

I've already built the Marchwood PSU about 3 weeks ago. I've studied the data sheets of both IC's and as far as I can tell the main differences are going to be in the current sense resistor values as foldback starts at about 50/60VmV on the SG as oposed to 0.6V on the 723. Can ayone else see any glaring differences?

Regards M3VUV.
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Old 17th Dec 2018, 11:55 am   #18
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Default Re: PSU using SG3532J.

It has a shutdown pin is one difference. It'll have to be parked in the go state, or maybe used to initiate a smooth turn-on after the reservoirs are up. This avoids transients on turn on (That's another current thread) and is what I do in my PSU by means of sequenced switching.

But, you'll have to go through the datasheet line by line checking for gotchas. Some can be quite subtle. Only then can you be sure enough to risk hardware.

David
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Old 17th Dec 2018, 12:00 pm   #19
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Default Re: PSU using SG3532J.

I think I may just build the cct anyway and suck it and see.

Cheers anyway 73 M3VUV.
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Old 17th Dec 2018, 2:04 pm   #20
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Default Re: PSU using SG3532J.

The data sheet shows the shut down pin with an inverting transistor on the shut down pin in one of the diagrams.
What ever you do you will need to have one current monitoring resistor per output transistor.
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