Power Supply Testing

[Jamebonds1]

Well....sadly he does actually have a point. A case fan will not pull any significant power from the system. 0.2 amps is almost nothing. While it is a load technically speaking, I personally wouldnt consider it enough of a load to use for testing.

Pulling 0.2 amps from a line that is made to supply 25A + is hardly a load for any power supply. You would be better off using a few HDDs.

Yeah. I'm not buy that. I'm not sure where you get that information from, but there is no source that external fan is not better way to test voltage. 0.2 amp is more than enough to test a voltage. That would give you reliable read and prevent from being damaging. The voltage is depend on PWM chip (voltage adder). I built switch mode power supply, so I know how they work. Math are pain in neck.

 

[voyagerfan99]

Yeah. I'm not buy that. I'm not sure where you get that information from, but there is no source that external fan is not better way to test voltage. 0.2 amp is more than enough to test a voltage. That would give you reliable read and prevent from being damaging. The voltage is depend on PWM chip (voltage adder). I built switch mode power supply, so I know how they work. Math are pain in neck.

It's pure logic. Just because you can pull 1/5th of an amp doesn't mean you can pull more than that.

 

[Jamebonds1]

It's pure logic. Just because you can pull 1/5th of an amp doesn't mean you can pull more than that.

What do you mean?

 

[Okedokey]

A PSU's ability to provide stable voltage regulation diminishes as you change the percentage load. Loading a 12V rail with 2A or less (a fan) is completely meaningless and pointless. The only way to fully test stability, noise etc is to load it up 50% or more, and even then, it wont have any effect on the other voltage rails.

Secondly most PSU's these days run fine without a load and will reliably give you a 12V or any voltage read.

Your test is pointless for determining vdroop or regulation limits.

 

[Jamebonds1]

A PSU's ability to provide stable voltage regulation diminishes as you change the percentage load. Loading a 12V rail with 2A or less (a fan) is completely meaningless and pointless. The only way to fully test stability, noise etc is to load it up 50% or more, and even then, it wont have any effect on the other voltage rails.

Secondly most PSU's these days run fine without a load and will reliably give you a 12V or any voltage read.

Your test is pointless for determining vdroop or regulation limits.

I'm not buy that. Your argument is pointless without source website. So where is your source?

PS: precent is voltage not amp.

 

[Okedokey]

I'm not buy that. Your argument is pointless without source website. So where is your source?

PS: precent is voltage not amp.

I don't need a source mate, as the equation for %regulation is a function of load. So without a load, your tests are virtually meaningless beyond "the psu switches on".

Load regulation of a constant-voltage source is defined by the equation:

%{Load Regulation} = 100% X {V_{min-load} - V_{max-load}} / {V_{nom-load}}

So yeah, any basic understanding of switching mode powers supplies would provide you with the reason why loading is important.

 

[Jamebonds1]

I don't need a source mate, as the equation for %regulation is a function of load. So without a load, your tests are virtually meaningless beyond "the psu switches on".

Load regulation of a constant-voltage source is defined by the equation:

%{Load Regulation} = 100% X {V_{min-load} - V_{max-load}} / {V_{nom-load}}

So yeah, any basic understanding of switching mode powers supplies would provide you with the reason why loading is important.

Good lucky at try to get me believe without source.

 

[Okedokey]

Good lucky at try to get me believe without source.

Time and time again, you've been proven to not understand psus... im not going to bother as you're struggling to even type a sentence.

 

[Jamebonds1]

Time and time again, you've been proven to not understand psus... im not going to bother as you're struggling to even type a sentence.

Then don't bother to proven me wrong without source next time. I know you use wikipedia to given math which is why I don't believe you.

 

[Okedokey]

Dude, i have an electronic engineering degree, so I really don't need to reference anything.

But here you go:

The DC output voltages shall remain within the regulation ranges shown in Table 2 when measured at the load end of the output connectors under all line, load, and environmental conditions. The voltage regulation limits shall be maintained under continuous operation for any steady state temperature and operating conditions specified in Section 5.

and Section 3.2.1 where voltage regulation measurements and tolerances are measured at peak load.

http://www.formfactors.org/developer\specs\ATX12V_PSDG_2_2_public_br2.pdf

 

[Jamebonds1]

Dude, i have an electronic engineering degree, so I really don't need to reference anything.

But here you go:



and Section 3.2.1 where voltage regulation measurements and tolerances are measured at peak load.

http://www.formfactors.org/developer\specs\ATX12V_PSDG_2_2_public_br2.pdf

I already proved that information and I told that voltage read should be in range of +/- 5%. Go read my post again very careful.

 

[voyagerfan99]

Okay guys, get over it and move on.

 

[Okedokey]

I already proved that information and I told that voltage read should be in range of +/- 5%. Go read my post again very careful.

Ok, let this be my last post on the matter then i give up.

The role of a PSU is to provide a constant voltage for a variable load. The 5% tolerance is a minimum and maximum variance over different loads. Measuring or testing this at just above minimum load provides absolutely no evidence that a PSU can sufficiently maintain voltage regulation at any other load. That is why the design standard specifies all tolerances (e.g. ATX standards) to be measured at 100% load, peak temperature. As both these things affect the voltage regulation.

Ideally, the output of most power supplies should be a constant voltage. Unfortunately, this is difficult to achieve. ...factors that can cause the output voltage to change. [is]... is a change in the load resistance. In complex electronic equipment, the load can change as circuits are switched in and out.

These variations in load resistance tend to change the applied dc voltage because the power supply has a fixed internal resistance. If the load resistance decreases, the internal resistance of the power supply drops more voltage. This causes a decrease in the voltage across the load.

Many circuits are designed to operate with a particular supply voltage. When the supply voltage changes, the operation of the circuit may be adversely affected. Consequently, some types of equipment must have power supplies that produce the same output voltage regardless of changes in the load resistance or changes in the ac line voltage. This constant output voltage may be achieved by adding a circuit called the VOLTAGE REGULATOR at the output of the filter.

LOAD REGULATION

A commonly used FIGURE OF MERIT for a power supply is its PERCENT OF REGULATION. The figure of merit gives us an indication of how much the output voltage changes over a range of load resistance values. The percent of regulation aids in the determination of the type of load regulation needed. Percent of regulation is determined by the equation:

This equation compares the change in output voltage at the two loading extremes to the voltage produced at full loading. For example, assume that a power supply produces 12 volts when the load current is zero. If the output voltage drops to 10 volts when full load current flows, then the percent of regulation is:

Ideally, the output voltage should not change over the full range of operation. That is, a 12-volt power supply should produce 12 volts at no load, at full load, and at all points in between. http://www.tpub.com/neets/book7/27j.htm

Therefore your specified test with simply a small load (fan) will provide no information beyond the latching circuit works as it is not testing for any real-case scenario.

 

[Jamebonds1]

Ok, let this be my last post on the matter then i give up.

The role of a PSU is to provide a constant voltage for a variable load. The 5% tolerance is a minimum and maximum variance over different loads. Measuring or testing this at just above minimum load provides absolutely no evidence that a PSU can sufficiently maintain voltage regulation at any other load. That is why the design standard specifies all tolerances (e.g. ATX standards) to be measured at 100% load, peak temperature. As both these things affect the voltage regulation.



Therefore your specified test with simply a small load (fan) will provide no information beyond the latching circuit works as it is not testing for any real-case scenario.

Go read voyagerfan's post again. That mean you need stop too. I can keep post as long as it is not going damage or read incorrect, unless I'm told to stop post about how to test PSU with multimeter. So get it over. Voyagerfan is right, it is time to stop fight.

 

[StrangleHold]

Using a case fan to test a 12V rail, all you will find out is if its stable at a .25amp/3W. I guess if all you want to push with it is a case fan then your great. If you have a issue with a rail. Its voltage and wattage can fluctuate widely depending on how much load your putting on it. I've replaced many power supplies with this same issue. If you truly want to test it, you should at least put a 50% or more load.

 

[voyagerfan99]

Go read voyagerfan's post again. That mean you need stop too. I can keep post as long as it is not going damage or read incorrect, unless I'm told to stop post about how to test PSU with multimeter. So get it over. Voyagerfan is right, it is time to stop fight.

He proved his point. And that's fine. You're the only one still going on about it.

 

[G80FTW]

Using a case fan to test a 12V rail, all you will find out is if its stable at a .25amp/3W. I guess if all you want to push with it is a case fan then your great. If you have a issue with a rail. Its voltage and wattage can fluctuate widely depending on how much load your putting on it. I've replaced many power supplies with this same issue. If you truly want to test it, you should at least put a 50% or more load.

I used to use older power supplies to run car amplifiers inside my house that I used as my home theater (since car audio is relatively cheaper than home audio). And I can tell you, with the volume turned up (the last PSU I used was rated at 30A on the 12V) it would drop to around 10v before shutting off. The first time I attempted this, I actually melted the original wire in the power supply (as Im sure I was pushing alot more than 30A through it) so I upgraded the wire to 8awg and it ran alot better.

But yes, higher loads will certainly have an effect on the voltage. That goes for ANY electrical device. The more amperage you attempt to draw from a power source, as the power source struggles to maintain that amperage it will eventually start losing voltage to do so.