9 volt DC to 48V DC

[Ricren]

Hi folks,
I'm serching for a circuit to convert 9vDC to 48v DC for a mic that needs phantom power.
Sennheiser sells an adapter like this,but it's expensive, so I'd like to build one myself.
Any information on this is apreciated

Tks.

Ric

 

[cgaulin]

You should look for either a charge pump(SwitchingRegulators) or DC-DC converter.

DC-DC converter are costly.


A good start could be a look at National semiconductor web site for SwitchingRegulators (step-up) .
www.national.com.
you can also search Digikey site

 

[Bill Fitzpatrick]

Possible a dumb answer but couldn't you just use 5 batteries?

 

[jackinnj]

here's a lot of info on phantom power:

http://www.hut.fi/Misc/Electronics/circuits/microphone_powering.html

if you have a wall-wart which delivers AC you can use a voltage multiplier (tripler, quadrupler, whatever) -- this will be quieter than a switcher -- you can regulate 48V with a LM317HV or a TL783 (which will go to 125V)

 

[davesaudio]

have a look at mpja.com
surplus site w lots of dc dc converters
otherwise oscillator driving multiple stages of voltage doubler
those keywords should find a cct

 

[Ricren]

5 batteries is an option, but since the microphone only needs 2 ma of current at 48V I thought that if the circut is not very complex, it could end up being more compact that a set of 5 batteries.
Weight is another problem. This microphone feeds a camcorder in a Steady cam mount, so weight is of outmost concern.

cheers

Ric

PD: tks for the links, folks.

 

[moamps]

Hi,

almost all electret mikes (I suppose that's what you've got since it needs only 2mA) work with smaller voltages. Try yours with two 9V block batteries and, say, 2k2 1% resistors. Also, you might want to bypass batteries with small block caps.

Regards,
Milan

 

[Ricren]

MK60

I do not have that luck, Moamps. The mic is a Sennheiser MK60, a beautiful shotgun that needs 48 V +_ 4V according to the manufacturer.

tks anyway.

Ric

 

[li_gangyi]

I suppose u could build an SMPSU using National's line of switchers...

 

[thespeakerguy]

One approach

use a MAX1771. It's not the latest/greatest, but will work, has a free sample, and come in an 8-pin DIP package.

 

[Ricren]

Re: One approach

use a MAX1771. It's not the latest/greatest, but will work, has a free sample, and come in an 8-pin DIP package.

Tks for the data. I never used such that chip. I downloaded the PDF and it suggests this:

"The MAX1771 drives an external N-channel MOSFET switch, allowing it to power loads up to 24W. If less power is required, use the MAX756/MAX757 or MAX761/MAX762 step-up switching regulators with on-board MOSFETs"

Which I thing is better because is more compact and I need a few MA anyway. But I can not find any reference that points at using these chips in a 48V output configuration. Any ideas?

tks, Ric

 

[li_gangyi]

head over to national at
www.national.com
use the webbench power tool and input ur requirements...it will come up with a nice schematic and simulation for whatever you want...takes just a few mins...I'll recommend the LM2587...

 

[Ricren]

Great data

Tks a lot for the data. That tool at National is really great. I'll give a try to the IC you suggested. I sounds like the right part to use.

cheers
Ric