Would this work? (15VAC to 12VDC & 24VDC)

[diyguitarmods]

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!

[DF96]

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.

[Elvee]

Originally Posted by diyguitarmods

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!

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?

[knutn]

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...

[diyguitarmods]

Originally Posted by Elvee

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?

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.

[diyguitarmods]

Originally Posted by knutn

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...

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!!

[Elvee]

It is also possible to retain the bridge rectifier, in case you need a higher current on the low voltage output: see Vmult1.

For the halfwave version, there are alternative options, see Vmult2 f.e.

[diyguitarmods]

Originally Posted by Elvee

It is also possible to retain the bridge rectifier, in case you need a higher current on the low voltage output: see Vmult1.

For the halfwave version, there are alternative options, see Vmult2 f.e.

Hey thank you! I just saw this post. I really appreciate the effort. I'll post the results when I'm ready.

[diyguitarmods]

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)

[Elvee]

Originally Posted by diyguitarmods

. As you can see the power supply is massive with all those huge caps! (everything on the board to the left)[/IMG]

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.