B Analog power supply output question

[Patch Cabbage]

TL;DR

simple engineering question

I'm setting up an analog power supply. I have the transformer bridge and filter capacitors so far. The transformer puts out 30 volts. I am currently using two parallel power transistors and a variable resistor to set the output. It also has a meter to monitor voltage. The question is this. How do I set up a single transistor to remove whats left of the ripple after the filter capacitors. It has to vary along with the control transistors to be constant in its ripple removing. The bases of the two power transistors to the potentiometer is currently the control.

 

[Baluncore]

Welcome to PF.

What is the part numbers of the parallel power transistors?
What range of output voltage do you require?
How much current in amps must it supply?

 

[Patch Cabbage]

Max 30 amps? 15a each? 0-40 on the volts.

 

[Baluncore]

What is the part numbers of the parallel power transistors?

 

[Patch Cabbage]

The specs are npn silicon the base comes on at .2v and they work good.

 

[Baluncore]

I need a part number that identifies the device and the package, that tells me the beta and the power rating.

A silicon power transistor will usually need lots of base current, maybe 1/20th of the output current. The base voltage will be closer to 1 volt.

 

[Patch Cabbage]

The control transistors are up and running. I need a ripple remover circuit after the capacitor filter to remove the ripple. The ripple remove has to invert and insert the ripple to the control which is variable on the power transistor's bases. A transistor with a zener would work if the power supply weren't variable. The supply is for a solid state transmitter. Ideally, I don't want any ripple what so ever. I'm looking only for a single transistor ripple remover circuit. The ones in all the linear power supplies online seem to me to be completely absurd and overly complicated for their applications. I'm looking for simplicity. Something that works good easy to work on and reliable.

 

[Baluncore]

Your ripple remover must carry the full output current. It will need the same output current rating as the output power transistors, so why duplicate them?
Control the base of the power transistors to remove the ripple, and to regulate the output voltage. If you do not provide part numbers, I cannot design the base drive circuit that removes the ripple.

 

[berkeman]

TL;DR: simple engineering question

I'm setting up an analog power supply.

Please post your schematic. Use the "Attach files" link below the Edit window. Thanks.

 

[Patch Cabbage]

Are you sure. Sounds like you would like to insert it on the high side power line. That sounds like putting a secondary control before the control. Is this right?

 

[berkeman]

Are you sure. Sounds like you would like to insert it on the high side power line. That sounds like putting a secondary control before the control. Is this right?

Wakarimasen...

 

[Patch Cabbage]

Transformer 30v 20a, bridge rectifier standard, filter capacitors 20k each, power transistors 15a each on top of each other with heat sink, and potentiometer from the high side to the base.

 

[Baluncore]

I have been working with linear supplies for more than 50 years.
I know what I am doing.
Post your circuit diagram and I will show you how to eliminate the ripple.

 

[Patch Cabbage]

I don't know how to post a diagram even if I had one.

 

[Patch Cabbage]

Also, what do you think of Pyramid's line of power supplies.

 

[berkeman]

I don't know how to post a diagram even if I had one.

Please post your schematic. Use the "Attach files" link below the Edit window. Thanks.

 

[Baluncore]

Here is the circuit you describe, and the ripple it will produce.

 

[Patch Cabbage]

Thank you for all the help. Making and posting a schematic for something this simple seems to much of a hassle to me as I only need to connect two leads of a transistor up. Thanks anyway. I think I'll just go and try to figure it out by myself.

 

[Patch Cabbage]

Hey, that's a good circuit diagram, only it's missing the ripple inverter transistor.

 

[Baluncore]

Then fix the diagram.
Get a copy of LTspice, it is free from ADI.

 

[Patch Cabbage]

Thanks, will do.

 

[DaveE]

I don't know how to post a diagram even if I had one.

I doubt you can build a reliable power supply without documentation like schematics.

I've also done several of this sort of design and I believe it's more difficult than you think. I would have a million questions in a design review, but I'll just assume you've done the analysis (things like worst case temperatures, short circuit protection, turn on transients, capacitor ripple current, second breakdown of BJTs, etc.). I think you may have troubles ahead, but kudos for exploring, I think you'll learn a lot. Good luck.

Check out this old National Semi Audio-Radio handbook the appendix has a nice section on your rectifier/filter.

Anyway, it sounds like you would be interested in the capacitor multiplier circuit, although I've personally never seen it used at this sort of power level. Normally it would be done with feedback to a reference, like the venerable LM723, or just op-amps.

 

[Patch Cabbage]

Hey thanks. I need to explain something here. I'm not that learned. My view is this. Lower alternating current off of the secondary then goes to a full wave bridge rectifier since I want it isolated from the ground so it takes 4 diodes. Diodes only let current pass in one direction, the substrate on the silicon is low on one side. Then it goes though a ballast of capacitive charge plates which act slow to charge up reducing some of the 120 cycle which is still there. Then it goes through the current controller which is a big power transistor. It's base has a lower substrate which needs to be charged up for current to pass. The charge up is controlled currently by a potentiometer, see Baluncore's schematic. I think in terms of junction and current controlling and magnetic transfers and charge ups and stuff. When it comes to book stuff and schools I flunk. But the sort of good part of it is that I need a good understanding of how the parts work and work together to get the voltage and amperage out of the power supply with an accurate reading on the meter. My builds are all measure cut and fit builds. Schools and school books are just way to difficult for me. Hopefully this thing will finally get working right sometime. Edit: I changed the 60 to 120 because it doubles in the same direction after the bridge.

 

[Patch Cabbage]

Oh ya I forgot. I put a circuit breaker right after the transformer.