# Basic tests for a Power Supply

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#### fantabulous68

##### Member
I got a power supply :
output is 5V, 200mA

The basic tests one can perform on the power supply would include:

1. Check it meets the load requirements
2. Check it outputs 5V

Are there any other BASIC tests that can be performed?

#### ericgibbs

##### Well-Known Member
I got a power supply :
output is 5V, 200mA

The basic tests one can perform on the power supply would include:

1. Check it meets the load requirements
2. Check it outputs 5V

Are there any other BASIC tests that can be performed?

hi Ms F,
You could scope the ripple voltage on the 5V output.

#### fantabulous68

##### Member
Thanks Mr EricGibbs

#### stevez

##### Active Member
You might also test the regulation as the load changes. When I was really bored (recovering from back surgery) I measured the ripple suppression of a regulator and pass transistor arrangement. I don't know if that would be a basic test but it is a test that you could run.

#### Mikebits

##### Well-Known Member
Your requirements dictate what you test for such as, short circuit protection, etc.

#### MikeMl

##### Well-Known Member
...

Are there any other BASIC tests that can be performed?

An often overlooked test is "dynamic stability", where the load is suddenly applied and then removed. You are looking for "overshoot" and "damping". A power supply is after all a feedback control system, so it should be tested as one.

Thanks Guys

#### BrownOut

##### Banned
I once built a load tester for qualifying our power supplies when I worked for a defense contractor. It used a power transistor as the load element, and I could just dial up the load current by adjusting the base bias. It replaced the keluge of switches and power reisistors we were previously using.

I was able to disqualify many power supply designs with it Wish I still had the schematic. It was a very simple concept and design though.

#### Mr RB

##### Well-Known Member
Here's a very simple constant-current dummy load schematic, the sort fo thing you can solder up on the spot when it's needed;

Code:
Variable constant current dummy load;
(requires +5v regulated supply also).

PSU
Output   ------------,
|
|
+5v  --------,       |
|       |
|       |  NPN
500 ohm   R       C  TIP3055
pot    R<----B    10A 80v
R       E
|       |
|       |
|       |     (or 4.7 ohms  5w)
|       |
Gnd ---------*-------*--

#### Boncuk

##### New Member
Wish I still had the schematic. It was a very simple concept and design though.

Hi BrownOut,

I'll check what I have. I faintly remember a design I made a while ago for an adjustable load between some milliWatt and a few hundred Watt. (Requires turbo cooling though)

Boncuk

Cool stuff

#### fantabulous68

##### Member
OK im going to ask a very silly question-

If you have a switch mode power supply-booster type
boosting 2v to 5v
the battery input is from 2v to Vout

-lets say you use a 6V battery................(but Vout is 5V not 6V, so what is going to happen if you use 6V???)

OK i know THATS GOING TO KILL THE PURPOSE of using a booster.

BUT a switch mode power supply(SMPS) IS MORE efficient than using a 9V battery with a LM7805 to give you 5V output for the micro controller........................

The battery on the SMPS will last longer............ + The 9V battery and LM7805 is bulky & the battery power fades fast

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#### indulis

##### New Member
You could try this one...

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#### indulis

##### New Member
Or one of these...

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#### fantabulous68

##### Member
Handy Stuff Thanx

#### indulis

##### New Member
An often overlooked test is "dynamic stability", where the load is suddenly applied and then removed. You are looking for "overshoot" and "damping". A power supply is after all a feedback control system, so it should be tested as one.

Technically, it was never stated that this was a regulated supply, so there wouldn’t be a feedback loop. But if it was regulated, “transient response” testing is only an indicator of “conditional stability”. Generating some bode plots would be the real indicator of loop stability.

#### fantabulous68

##### Member
Technically, it was never stated that this was a regulated supply
,

True but i am referring to a regulated supply because I am going to use it to power a micro controller.

#### ericgibbs

##### Well-Known Member
,

True but i am referring to a regulated supply because I am going to use it to power a micro controller.

hi Ms F.

Many use the same psu to power the PIC and relays/motors etc... [ not really the best way]

So the transient test is a good idea.

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