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0-30V bench power supply

Chippiejnr

New Member
I have a couple of the Red pcb based 0-30v power supply board kits from EBay.
Having tried to power them with a linear transformer, I find the regulation of the transformer not good enough despite being a toroid type.

I have a 36v switch mode power supply rated for 4 A which holds up quite well under load.

My plan is to use the 36V to power the series element, use a linear reg to reduce the control sections supply rail to 30V …to generate the negative supply, I was proposing to add a seperate winding onto the switching transformer……then use a simple diode,cap circuit with a zener to cap the voltage…..

Anyone see any issues with this proposal?
 
I have a couple of the Red pcb based 0-30v power supply board kits from EBay.
Having tried to power them with a linear transformer, I find the regulation of the transformer not good enough despite being a toroid type.

I have a 36v switch mode power supply rated for 4 A which holds up quite well under load.

My plan is to use the 36V to power the series element, use a linear reg to reduce the control sections supply rail to 30V …to generate the negative supply, I was proposing to add a seperate winding onto the switching transformer……then use a simple diode,cap circuit with a zener to cap the voltage…..

Anyone see any issues with this proposal?

Yes, the new winding won't be regulated.
 
Nigel, I agree the winding wont be regulated, but I dont see that it needs to if it has sufficient overhead when the main output is loaded. ( with approx 5 turns on the transformer, I'm seeing around 12V DC with a red led loading the winding, drawing some 30 mA...)
The onboard Negative supply rail will only be at 2-3V and wont be heavily loaded.

The op amps I'm using are the recommended TLE2141 so there shouldn't be any issues...
 
I have a couple of the Red pcb based 0-30v power supply board kits from EBay.
Having tried to power them with a linear transformer, I find the regulation of the transformer not good enough despite being a toroid type.

I have a 36v switch mode power supply rated for 4 A which holds up quite well under load.

My plan is to use the 36V to power the series element, use a linear reg to reduce the control sections supply rail to 30V …to generate the negative supply, I was proposing to add a seperate winding onto the switching transformer……then use a simple diode,cap circuit with a zener to cap the voltage…..

Anyone see any issues with this proposal?
How can I have an issue when I have no design specifications. If the red PCB is "not good enough" and you know your smps is good enough, then go with that - assuming that your negative rail will be ok with a simple diode cap circuit.
 
ZZO,

Not sure about your opening comment..

The 'RED' pcb is good enough, in fact for those that dont know, the design dates back to the 70's which was published in one of the electronic monthly mags of that time...
Yes my smps is good enough, I was just inviting comments from the membership about how to deal with the Negative rail generation using my proposal...
 
ZZO,

Not sure about your opening comment..

The 'RED' pcb is good enough, in fact for those that dont know, the design dates back to the 70's which was published in one of the electronic monthly mags of that time...
Yes my smps is good enough, I was just inviting comments from the membership about how to deal with the Negative rail generation using my proposal...

Assuming it's the usual Chinese one?, it's been discussed endlessly here (and on other forums) - it's VERY poorly designed, with poor performance and poor reliability. Corrections to it have been posted, but obviously the Chinese manufacturers aren't interested in that.
 
Nigel,
Yes it is the 'Red' kit from China...
I've read the discussion topic on many occasion, seen many other offerings on webpages where folk have modified and recommended changes to enhance its poor performance...
 
First you say...


I have a couple of the Red pcb based 0-30v power supply board kits from EBay.
Having tried to power them with a linear transformer, I find the regulation of the transformer not good enough despite being a toroid type.
Then you say...


The 'RED' pcb is good enough,

How are we supposed to answer...


Anyone see any issues with this proposal?

When what you have is simultaneously good enough and not good enough?
 
Jeez… I give up!

All I wanted was a critique of the smps additional winding proposal….in light of what I stated about the regulation issue using a transformer.

The power supply itself has been done to death, the modifications suggested in the various threads on the internet I’ve taken note of..

Maybe it’s time for a moderator to close this thread?
 
I will reply to your exact question, which is: …to generate the negative supply, I was proposing to add a seperate winding onto the switching transformer…

The answer would be, it depends on the topology used. To be able to determine the primary’s winding direction and number of turns.
Also, what type of core is used for the transformer itself? EE? PQ? Toroid.
Can you take a close and clear photo of?
 
S-T,

While I thank you for taking the time to reply and for those members of the forum who have also taken time to review, I’m going to shelve this…..
 

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