Switch Design Power Supply

[rogeryu_ph]

Am I right? is that they called it? Is it regulated? I don't see 7809 IC.... It also has a diode and a very small transformer but seems to be the diode comes first before the transformer 
Furthermore, is it recommended for pedal? I don't see any DIY project or schem around maybe it's not........

Would appreciate someone discuss on how it is implemented,.

Thanks,
Roger

[SISKO]

Youre rigth  They are also called SMPS (switch mode power supply) and mucho more names.

In somes cases they are regulated (PCs, amps), but others they are not (somo cellphones cargers). They are regulated by some sensing Ics or by a phototransistor controlling the rate of the switching.

In a raw way i can put it like this:

AC outlet----> Rectification (diode) ---> Oscillator ( A crude CC to AC converter. Higher frecuency than the tipical 50/60 Hz)--> Transformer---> Rectification-->Filter --->Output.

With a much higher freq you reduce the tunrs of the transformer, thus the size.
Also the are some parts missing as filters, regulation etc. But thats a crude way of showing you how it works

[rogeryu_ph]

Thanks Sisko 

[km-r]

hi mr roger!

smps's are very noisy though... i bought some 9v SMPS's for use with my pedals but theyre just damn too noisy.
not to tell one of them was not isolated from the mains line! i almost died... 
from what ive heard visual sound's smps is very quiet for used with distortion boxes...

[rogeryu_ph]

Hi Km-r,
I asked this co'z my Boss GT10 multifx supplied with this type of 9V power supply SMPS adaptor and sometime i can hear some buzz and my suspect is this adaptor but not quite sure. It's also odd and puzzle me that when I touch the GT10 metal body the buzz sag slightly. I even tried my conventional regulated 9v DIYed power supply which I used for my pedals but just the same. Maybe it's inherent with the GT as quess or the SMPS supplied is not that good in design.
Visual sound product i know RG is connected with, maybe he could help by giving schem of a visual SMPS if he is or would allow to        Callllllllingggggggggggggg R.G.      Hope his cellphone is not busy 

Thanks,
Roger

[earthtonesaudio]

Hook it up with batteries, that is the surefire way to determine if the noise is coming from the power supply.  Fresh batteries are noiseless, pure DC.  If the noise persists, it's coming from somewhere else.

...I doubt RG or Visual Sound would release the schematic for their 1-Spot.  There are lots of specialized parts inside and exposed line voltages.  The exposed line voltage is why they don't want you to open it up, either.   

But, if you've already learned all you can from Wikipedia, check these out:
Boost converter (5V to 24V DC using parts you might already have):
http://www.edn.com/archives/1998/021698/04di.pdf (page 6)

Then there's this superb paper about an LED dimmer which is really an article on the Buck converter (step-down DC converter) in disguise:
http://www.opensourcepartners.nl/~costar/leddimmer/

[Sir H C]

In general the design of SMPS is as much an art as a science.  Little parasitic resistances and capacitances can keep the circuit from being stable.  Now adays there are small switchers that run in the 1 MHz+ range so you don't hear them unless it is down-converted somewhere.  Z Vex uses a switcher with the nano amp to get the high voltage supply. 

[earthtonesaudio]

Some general thoughts about the switching frequency:
Lower frequencies are harder to filter out of the supply, and below 20kHz is audible: bad.
Higher frequencies don't need as much inductance/capacitance to filter them out, BUT higher frequencies leak into your audio circuit easier.  Copper traces in circuit boards can look to MHz frequencies like single coil pickups look to 60Hz hum.
On top of that, higher frequencies require much more thought in the layout.

If you're going to DIY something, I'd make the switching frequency just high enough to be inaudible, then add proper filtering to the output, then (most importantly) isolate it from the rest of the world, especially your audio signal.

[Sir H C]

And remember, because of the sharp edges on the switchings even 50kHz has some harmonics way higher.

[The Tone God]

I asked this co'z my Boss GT10 multifx supplied with this type of 9V power supply SMPS adaptor and sometime i can hear some buzz and my suspect is this adaptor but not quite sure.

I'm alittle lost, are you trying to solve a noise problem or build a switching supply ?

Andrew

[rogeryu_ph]

@ Tone God, both or just buy one superior for my multifx if not doable, you may suggest me a good one Sir.

@ Earthtonesaudio, i will take into buck converter if i got more time, thanks i need some links like this.

@ Sir Hc , good info co'z i'm still puzzle and newbee on SMPS.

Would appreciate more info/your experience and links guys.

Many thanks 
Roger


 

[The Tone God]

After having to spend a huge amount of time designing a switching supply that was audio friendly for the TubeUlent I can tell you this is a difficult task. For the average DIYer linear supplies are still easier to build.

The one spots see to enjoy a good rep.

Andrew

[Sir H C]

I would recommend reading some of the Application Notes from Linear Tech.  They have some of the best technical writers in the industry and are big in the switching regulator world.  These things are tricky, but often these companies have what they call the "reference design" that gives a layout with parts (sometimes you can get the populated PCBs from the company).  Warning many of these designs now use insanely small surface mount devices, without a microscope, it is nearly impossible to solder these things (I have been doing a bunch of 0402 soldering recently, 1mm x .5mm).

[rogeryu_ph]

I was thinking of upgrading if possible an exisiting one and transfer it into new housing co'z i got lot of scrap SMPS adaptor. All of them still working and measured their voltages but many are out of specs.....