Need to convert DC-DC from 9V to 48V. Ideas? - Page 1
Forum section: electronics / beginners

author: samsagaz
author_rank: Contributor
timestamp: December 15, 2011, 07:53:48 pm
content: Hi guys, want to convert from 9V (battery) to 48V to use with MIC Phantom. I checked some circuits but see diferents alternatives, and cant decide wich one to choice.I want to have high eff because want to operate the mic from an 9V Alkaline Battery and dont want to just get without charge in 1 hour.these are some of the ics that i seeMC 34063LT1054LTC1144LTC3872MAX668Btw, tha mics use like 10-12maRegards

author: IanB
author_rank: Super Contributor
timestamp: December 15, 2011, 08:57:39 pm
content: Have a look here:http://www.national.com/en/webench/power.html

author: Psi
author_rank: Super Contributor
timestamp: December 15, 2011, 10:51:30 pm
content: i'm not sure if this module is suitable because it outputs negative 48V, but if you want a pre-built solutionhttp://search.digikey.com/nz/en/products/NMT0572SC/811-1583-5-ND/1927144- 4.5-5.5V input (so you can LDO 5V reg your 9V and you'll get pretty good usage out of the 9V down to 5V or so.- Up to 21mA @ -48V when the other channels aren't loaded (-24V and -72V)- small module- relatively cheap, US$14Actually, the datasheet says it's isolated between input and output, so you should be able to use it as +48V just fine.

author: NiHaoMike
author_rank: Super Contributor
timestamp: December 16, 2011, 12:27:39 am
content: For such a low current, what about use a voltage multiplier?

author: samsagaz
author_rank: Contributor
timestamp: December 16, 2011, 01:33:56 am
content: well, really dont know, where can i see wich are the best way to do that? i think that the best way will be the one that can let me use the 9V battery for long time. Will be great if the input can be 9 (battery) or 12v (Transformer).

author: IanB
author_rank: Super Contributor
timestamp: December 16, 2011, 01:54:18 am
content: Doing a quick search for microphone phantom power supplies suggests that there is a bit more to designing them than just stepping up to 48 V. There are stability, regulation, lack of noise and other considerations to take into account. Why don't you just buy one that comes with good reviews rather than trying to make one?

author: Zad
author_rank: Super Contributor
timestamp: December 16, 2011, 02:46:21 am
content: If you work out what sort of power it is drawing, and then calculate the current equivalent at 9V, you are looking at 100mA or so, even with a reasonably efficient converter. A 9V alkaline won't last very long. Maybe 2 hours, accounting for the reduced capacity at higher loads?

author: samsagaz
author_rank: Contributor
timestamp: December 16, 2011, 02:52:22 am
content: Quote from: IanB on December 16, 2011, 01:54:18 amWell i wanto to build my own one! if some companies make stable/reg/lack of noise ones, is not possible to get the same specs at home?

author: Zero999
author_rank: Super Contributor
timestamp: December 16, 2011, 02:13:43 pm
content: You could build a hybrid regulator. Use a DC-DC converter to get 52V and put an LM317 on the output to give 48V. This will give you low ripple, noise and excellent regulation.

author: samsagaz
author_rank: Contributor
timestamp: December 16, 2011, 02:37:06 pm
content: Quote from: Hero999 on December 16, 2011, 02:13:43 pmwich DC-DC converter to recommend me?

author: ejeffrey
author_rank: Super Contributor
timestamp: December 16, 2011, 02:57:26 pm
content: Put 5 9V batteries in seriesSuper low noise and will probably last 10 times longer than a single battery due to the conversion losses and capacity derating for high drain.

author: samsagaz
author_rank: Contributor
timestamp: December 16, 2011, 02:59:09 pm
content: Quote from: ejeffrey on December 16, 2011, 02:57:26 pmyeah, i think abt that, but are not to portable with 5 batteries, and battery price will be very high too

author: IanB
author_rank: Super Contributor
timestamp: December 16, 2011, 06:15:23 pm
content: Quote from: samsagaz on December 16, 2011, 02:59:09 pmThe battery cost will actually be lower using five batteries in series compared to one battery with a voltage converter. With five batteries in series the circuit will operate at 100% efficiency, whereas with one battery and a converter the efficiency will necessarily be lower. So over time you will buy more batteries in the single battery solution than the five battery solution.Also I note that none of the commercial offerings are powered by a 9 V battery. Most of them use a 12 V DC wall adapter, and the few that are battery powered use bigger batteries like AA cells. If you think about it, 10 mA at 48 V is going to equal 50 mA at 9 V, then increase that to 70 or 80 mA due to conversion losses. That's a heavy load for a 9 V battery and it won't last very long.

author: ciccio
author_rank: Frequent Contributor
timestamp: December 16, 2011, 06:27:55 pm
content: Phantom powered microphones have wide differences in power requirement: some work from 9 to 48 V, other don't work if powered with less than 40 V, some use really low power, some drain a lot of current.I don't know the mic you intend to use, so I'm not sure it will operate with a lower than 48 V voltage.Most of the microphones I've installed (and they are a really large number) worked flawlessly with a not standard 36 V dc supply (that happens to be the phantom voltage of the PA mixers I design and build).Enclosed is a schematic I happen to have readily available: it's powered from a 12 V dc wall adapter, but adding other stages to the voltage multiplier it will operate from 9 V, or it will supply about 24-26 V dc if powered from 9 V.regardsedit: disregard the preamp section, obviously...

author: ivan747
author_rank: Super Contributor
timestamp: December 16, 2011, 10:21:24 pm
content: Quote from: samsagaz on December 15, 2011, 07:53:48 pmDo you want to connect a phantom microphone to a non-phantom console?

author: Psi
author_rank: Super Contributor
timestamp: December 17, 2011, 12:12:51 am
content: What about 12V A23 batteries4 of them in series will give 48VThe energizer ones are rated at around 30mAh at 10mA discharge, so 3 hours worth.If you put two packs of 4 in parallel (so 8 batteries) you'd get 6 hours.And that wouldn't be huge, maybe the size of two 9volts.

author: samsagaz
author_rank: Contributor
timestamp: December 17, 2011, 05:40:30 am
content: Quote from: ivan747 on December 16, 2011, 10:21:24 pmWell, im making a console, i already have the PREamp (DIY) using THAT1512 opamp, but now trying to add the phantom power. Mainly i want to use 12V DC from a 1A transformer, but want to add some way to make it portable, so i want to use 1 or 2 9V Batteries. Using 5 batteries y think that the weight will be high, and maybe the price too.

author: DrGeoff
author_rank: Frequent Contributor
timestamp: December 17, 2011, 06:10:29 am
content: 48V is a bit of a misnomer in this application, since it is not really a voltage source you are after. Phantom power specifies 48VDC in series with a 6.8K resistor on each of the hot and cold balanced leads with respect to the GND wire. What this really means is that the end voltage is 48V with no load. However if shorted the maximum current that can flow is 14mA. So with a 10mA load you really only have 14V at the load, not 48V.

author: samsagaz
author_rank: Contributor
timestamp: December 17, 2011, 08:41:59 am
content: Quote from: DrGeoff on December 17, 2011, 06:10:29 amoh, i see, looks like not an easy task then :/

author: ejeffrey
author_rank: Super Contributor
timestamp: December 17, 2011, 09:33:27 am
content: Quote from: samsagaz on December 17, 2011, 08:41:59 amThat doesn't really affect your job -- 48VDC through some resistors is still a 48 VDC supply. Actually it makes things easier because it means phantom powered devices have to deal with varying supply voltages. Iif your supply is 45 volts or 42 volts everything should still work. You may have to tweak the feed resistors down slightly to compensate, especially for high current devices.