Wall Wart, or Switching Regulator....or what?

Thread Starter

iONic

Joined Nov 16, 2007
1,654
Was quite curious about this power supply as it stated that the output was 4.5V - 9.5V so I investigated.
It does not appear to be a switching regulator as there are no IC's/devices that do any "switching." Figured as much as it did not mention "switching regulator" on the supply anywhere. But my real question is....how does it supply between 4.5V & 9.5V? It measured ~5.1V with no load and failed to provide a glimmer of light for a small 12V LED strip. So what do I have here........aside from a china-supply. Doesn't appear I can rely on it supplying just 5V alone.

regulator.jpg
 

Papabravo

Joined Feb 24, 2006
16,498
Looks like a transformer, a discrete bridge rectifier, a filter capacitor, and a load dependent pre-regulator. I say pre-regulator because the output voltage covers a wide range and is probably load dependent.
 

BR-549

Joined Sep 22, 2013
4,938
It appears to me that the AC is dropped....rectified...filtered and fed to a switcher.

One might ad an additional feedback reference and switch, for multiple outputs.

I would chalk it up to a non-specific label with more than one product.
 

MaxHeadRoom

Joined Jul 18, 2013
23,368
Also appears to be an unregulated (not SMPS) PS, and the unpopulated areas are for different options of outputs.
With the transistor device shown, there appears to be some kind of attempt at regulation.
Max.
 

Thread Starter

iONic

Joined Nov 16, 2007
1,654
It appears to me that the AC is dropped....rectified...filtered and fed to a switcher.

One might ad an additional feedback reference and switch, for multiple outputs.

I would chalk it up to a non-specific label with more than one product.
So, if I wanted to operate a circuit, whose input range is 2.7V - 18V and another that is essentially 4 5mm LEDs and limiting resistors...will this function properly?
 

MaxHeadRoom

Joined Jul 18, 2013
23,368
So it appears to be set for 5v output, have you tried a small 5v load and see if it maintains it, at a couple of hundred milliamps?
Max.
 

Thread Starter

iONic

Joined Nov 16, 2007
1,654
So it appears to be set for 5v output, have you tried a small 5v load and see if it maintains it, at a couple of hundred milliamps?
Max.
OK, so I couldn't find a suitable 5V/200mA load so I did the following. I used another single 12V LED that consumes more than 200mA(likely 350mA). The LED lit up but dimly and was somewhat flickering. The voltage across the load was still 5.1V. I guess I'm ok with using it for it's intended purpose.
 
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Thread Starter

iONic

Joined Nov 16, 2007
1,654
A photo of the other side of the PCB would be very helpful.
Really nothing but a bunch of smt resistors....maybe a smt diode or two. When you include these parts into the equation, it makes no sense for it to be a simple wall-wart.
Unless,of course they are standard, yet only used if the supply was configured in an alternate fashion. Who knows.
 

BR-549

Joined Sep 22, 2013
4,938
iONic......I doubt that. First one has to have a schematic. I would assume it's a well known design. Draw it out if necessary.

Then find and study that circuit design from net. And go from there. You might find some updated improvements or more mods. Understand the circuit first.

From the specs of your components, determine a medium resistive load. Apply load and gain manual control of feedback or reference. Isolate normal feedback. By manually adjusting that reference.....verify voltage range with that resistive load.

This gives you an idea of what can be done with what you have. Now.....one can very the test load....for possible "stretching" of a particular parameter.

Was that follow-able?

And some wal-warts are extremely sophisticated. China has made sophistication very cheap.
 

MrChips

Joined Oct 2, 2009
23,946
Here is what I see.

AC mains directly connected to bridge rectifier to smoothing capacitor.
Followed by a two transistor switching circuit driving a transformer. Output of transformer is rectified and smoothed by a diode and capacitor.

Looks like SMPS. Smells like SMPS.
 

Thread Starter

iONic

Joined Nov 16, 2007
1,654
It's a crappy smps type....here's what i see....roughly....

View attachment 170989
Given it's a "crappy" smps, what sort of circuits would you not use it for? My intended was is to use it to power a proximity sensor that turns on 4 through-hole white LED's(probably 12mA-15mA each - 48ma - 60mA total). I chose it because I'd either use it for something non-critical and same the cell-phone smps's for slightly better projects. If I can't use it here I may just toss it....minus a couple of parts.
 
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