Looking for 24V to 48V conversion for phantom power

[Potato Cakes]

This is a board made from that schematic. It needs a little tweaking as the output is 45V and not 48V. Not really an issue but for sake of being exact it could stand to use a little adjustment.

Thanks!

Paul

 

[freshtapescent]

45V is technically in-spec for P48 phantom power, which is 48V +/- 4V (44-52V) delivered through 6k8 resistors.

 

[Potato Cakes]

45V is technically in-spec for P48 phantom power, which is 48V +/- 4V (44-52V) delivered through 6k8 resistors.

That is why I said 45V is not really an issue. Some mics will operate with voltages as low as 10V. The desire to be at 48V is to satisfy the OCD in myself and others who suffer from needing things to be exact.

Thanks!

Paul

 

[ccaudle]

This is a board made from that schematic

I can't see that part number on that picture, did you end up going with one of the CS5171 family devices you mentioned previously?

 

[emrr]

https://www.jameco.com/webapp/wcs/s...oreId=10001&catalogId=10001&productId=2106693
I bought 4 from Jameco and have implemented them in Langevin AM16 builds so I can confirm that they do indeed work.

Yes. Have used boatloads of those for phantom with zero problems. Hard to beat $10ish with no labor.

 

[KA-Electonics.com]

Keep in mind I haven't actually used that, I just found it based on some vendors I knew had products that might work.
I feel your pain on the power supply problem, there are a few switching devices that might work, but some would require winding a custom transformer, which is a big learning curve for a one-off project. Others might be able to use off-the-shelf inductors but still are a lot of layout work to get quiet (electrically) for audio use.

One thing I noticed looking over the datasheet for that charge pump is that it seems to change switching frequency based on load, which can sometimes cause a problem with audio. If you have additional filtering on the output, when the switching frequency decreases the ripple frequency might move below your filter cutoff, so a supply that was quiet enough with multiple loads might get noisier with lighter loads.
Look through the datasheet and see if there is a fixed frequency mode you can force, or if that is not possible make sure you look at the lowest and highest switching frequencies it will use and size your output filter appropriately.

Have you explored the Versa-Pac products?
https://www.eaton.com/content/dam/e...rsa-pac-inductors-transformers-data-sheet.pdf

 

[KA-Electonics.com]

Yes. Have used boatloads of those for phantom with zero problems. Hard to beat $10ish with no labor.

I've had good luck with the Meanwell 48V as well in my Heath IG-18 oscillator. It worked out to be quieter than the linear supply it replaced.

 

[Potato Cakes]

I can't see that part number on that picture, did you end up going with one of the CS5171 family devices you mentioned previously?

These boards are built from that schematic. It is not a manufacturer's off the shelf part.

Thanks!

Paul

 

[tinn]

I was using a DC/DC converter from MURATA or Recom which works well for 4 Channels. The 2424S converter was about 7€.
The components on the left side of the schematic are a general noise filter for the 24 supply.

 

[MicUlli]

I was using a DC/DC converter from MURATA or Recom which works well for 4 Channels. The 2424S converter was about 7€.
The components on the left side of the schematic are a general noise filter for the 24 supply.

Yes, that is one of the best solutions. Considering the usage of an NPN voltage follower configured as capacitance multiplier should reduce all noise components to safe levels...

 

[AdamFrisen]

Analog Devices has a line of high voltage charge pumps:
AD high voltage charge pumps

At least one of those is just a controller and needs external transistors.
Just noticed at least one of them is a little misleading in the table, it says max input voltage 32V, but that must be close to the breakdown voltage of the internal transistors, because the max input voltage is 32V if you use it as an inverter, but if you use it as a doubler max input is only 16V.

LTC7821 can handle up to 36V in for a doubler, but that is the one which needs external devices (four MOSFETs).

This one looks nice, up to 55V input supply, up to 50mA output current. At first glance should work pretty well to double 24V supply and run a couple of mics:
LTC3290 datasheet

Regarding LTC3290. I saw it can deliver +60V and it caught my interest to polarize the capsule. I tried LTC3290 to get about +60V for U87 cardioid from phantom power and it seems to work.

SMD and all but it is the smallest solution I have found so far.

https://groupdiy.com/threads/open-s...-stripped-down-u87.86814/page-56#post-1169927

 

[kevvy]

Just use one of these. 24V DC in, 2 x 24V DC out. Connect the output in series for 48V. (larger power ones are available).

https://www.mouser.com/ProductDetail/XP-Power/IA2424S?qs=sGAEpiMZZMsc0tfZmXiUnQ%2BwKZhbvwnuTbhx67uJf8lvHo6B4Y46mw==

Some of those cheap ebay boost converters are electrically noisy and not ideal for a mic preamp.

 

[AdamFrisen]

Just use one of these. 24V DC in, 2 x 24V DC out. Connect the output in series for 48V. (larger power ones are available).

https://www.mouser.com/ProductDetail/XP-Power/IA2424S?qs=sGAEpiMZZMsc0tfZmXiUnQ%2BwKZhbvwnuTbhx67uJf8lvHo6B4Y46mw==

Some of those cheap ebay boost converters are electrically noisy and not ideal for a mic preamp.

Thanks, but I am using the original LTC3290 and I wouldn't categorize it as being cheap. It's more expensive than what you suggest and also regulated.
I haven't measured the noise yet but initial comparisons without using it in identical mic body, LDC and U87 ORS voltage regulator, I don't hear higher noise level. But measuring in REW will show.

Besides, the goal was to get +60V to polarize the LDC, not to get the phantom power of +48V from 24V. I was just mentioning LTC3290 could be used to get +60V.