Can anyone tell me if this schematic that I just pieced together would work or if it's even in the right direction for getting regulated 12vdc and 48vdc from a 15vac supply?
If it is, can you tell me what the values of the caps should be in the regulation stages and if they are supposed to be electrolytic?
For anyone interested, I'm trying to add phantom power to the schematic below. It is an interface for plugging dynamic mics into guitar amps/effects (hopefully condenser mics as well if I can get the power supply working!).
I want to power the circuit and the phantom power from the same power supply. I've been trying to find the cheapest solution and it appears to be using an AC power supply that goes to a bridge rectifier (to convert to full wave dc) and then to a lm7812 regulator to bring it to the acceptable 12vdc for the circuit AND to also send the ac supply to a voltage multiplier (which I assume rectifies to dc) and then regulate with a lm7848 to get the 48vdc for the phantom power. does full or half wave rectification matter for phantom power? Did the multiplier i've shown in the schematic full or half wave rectify? I am just getting into audio electronics and am trying to learn as much as possible. Any help would be greatly appreciated!
If it is, can you tell me what the values of the caps should be in the regulation stages and if they are supposed to be electrolytic?
An externally hosted image should be here but it was not working when we last tested it.
For anyone interested, I'm trying to add phantom power to the schematic below. It is an interface for plugging dynamic mics into guitar amps/effects (hopefully condenser mics as well if I can get the power supply working!).
I want to power the circuit and the phantom power from the same power supply. I've been trying to find the cheapest solution and it appears to be using an AC power supply that goes to a bridge rectifier (to convert to full wave dc) and then to a lm7812 regulator to bring it to the acceptable 12vdc for the circuit AND to also send the ac supply to a voltage multiplier (which I assume rectifies to dc) and then regulate with a lm7848 to get the 48vdc for the phantom power. does full or half wave rectification matter for phantom power? Did the multiplier i've shown in the schematic full or half wave rectify? I am just getting into audio electronics and am trying to learn as much as possible. Any help would be greatly appreciated!
An externally hosted image should be here but it was not working when we last tested it.
No, it won't work as shown. It is difficult to run two quite different supplies from the same secondary, unless you really know what you are doing.
For capacitor values you need to read up about ripple voltage, and see the regulator data sheets.
For capacitor values you need to read up about ripple voltage, and see the regulator data sheets.
What current do you need? Something like <10mA on the 12V I presume, and the 48V?
Does the phantom supply need to be floating, or does it have a common terminal with the 12V?
In this case, which ones?
The circuit works when the two voltages don't have a common reference (ground). However, the phantom supply has to share its 0 V reference with the rest of the circuit, ruining the solution in post #1. You can modify the schematic by replacing the full wave rectifier with a half wave rectifier and grounding one end of the transformer secondary. For clarity I have shown this in the attached schematic.
P.S. I think a more elegant solution for the phantom supply would be to use a booster converter...
P.S. I think a more elegant solution for the phantom supply would be to use a booster converter...
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I think <10mA on the phantom supply as well. I don't know what floating means but I'm assuming it is related to grounding. Sorry! I'm just getting into electronics.
Thank you so much! I really appreciate the effort you took to make the schematic for me! As well as the explanation. I have a slightly better idea of what to google next now. Thanks a lot!!
Hey thank you! I just saw this post. I really appreciate the effort. I'll post the results when I'm ready.
Got it working in case anyone's curious. I'm starting a new thread (9vdc to 48vdc step up converter advice?) to figure out how to go about doing the same thing with a booster converter as suggested. As you can see the power supply is massive with all those huge caps! (everything on the board to the left)
An externally hosted image should be here but it was not working when we last tested it.
They do seem large indeed.
What values did you use?
In the sim for the full wave circuit the two largest caps are a 470µ/25V and a 220µ/63V.
As you can see, with 10 and 20mA load currents, the ripples are perfectly acceptable for a standard 3-terminal regulator.
Did you oversize those caps?
And anyway, the half-wave version is somewhat simpler and should be sufficient.
You can avoid specific ICs and build a discrete one.
Here is a crude example, it only has an efficiency of ~75%, but it is simple and foolproof, uses no exotic components and is well regulated.
The average operating frequency is around 50KHz.
Be sure to enclose it in a shielded box.
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Hi Elvee,
I really appreciate you're full wave schematic but ended up building the half wave schematic above because of the availability of the parts. The caps I used in the voltage multiplier stage were rated for 63v but some where I remember hearing that they'd work if they were rated for the max. input voltage rather than the max. output voltage but just to be safe I though I better go with 63v caps on my first try. Either way I don't think this design is nearly as compact as a booster converter could potentially be so I'm off to figure out how to do that next! Thanks for you help!
If you used Knut's shematic, there are a number of mistakes, resulting in unnecessary parts.
For minimal parts count, see the halfwave schematic I gave.
For minimal parts count, see the halfwave schematic I gave.
Elvee, You are the f&%*in man!! super nice!! I appreciate it very much! I just have a few questions. Is L1 a 1 milli-henry inductor? Is it ok to send the positive and negative leads of the battery (in this case unregulated 9vdc power supply) to the other schematic's power supply in parallel with your schematic?:
An externally hosted image should be here but it was not working when we last tested it.
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Yes, 1mH/500mA (or at the very least 250mA)
I don't exactly figure what you mean, but as long as the converter sees ~9V between its supply terminals (the battery symbol on the schematic), it will provide +48V referenced to the negative side of the input.
Thanks! I just meant having the battery go to your converter circuit as shown and directly to the other schematic's power supply I posted. I was just curious if the power supplies would some how interact with each other in a bad way.
If you use proper decoupling and layout, there should be no problem.
If you are not careful enough, some switching residue might end up in the audio path.
Even though it is ultrasonic, it is best avoided.
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