Power supply build quality pictorial. part 2

[Behemot]

Re: Power supply build quality pictorial. part 2

Well it's 8 years old platform, +- couple years, what would you want from that?

[TELVM]

Re: Power supply build quality pictorial. part 2

Hmmm ... I know nothing, but could it be that the relatively huge passive PFC inductor & associated circuitry also work somehow as inrush current limiter, allowing to discard the NTC thermistor?

[Behemot]

Re: Power supply build quality pictorial. part 2

I don't think so, as basically huge coil, it more of creates own spike when it "loads" after turning on the power. The same as the input capacitor.

Passive PFC is more of used as a harmonics suppresor.

[tom66]

Re: Power supply build quality pictorial. part 2

An inductor would act as inrush limiting, actually, but it would create a resonant tank circuit for several hundred ms after switching on. This could lead to double voltage across the caps briefly, if not significantly damped.

You don't need inrush limiting if customers don't complain about their breakers being tripped, or you don't care about damaging the input caps.

[TELVM]

Re: Power supply build quality pictorial. part 2

How about this?:

"... This report studies two of the most common methods that are used to mitigate this current, the first one being the use of Negative Temperature Coefficient Thermistors. These thermistors behave as a resistor whose resistance varies with changes in temperature. The thermistor initially has a high resistance, but as current begins to flow through it, it heats up and its resistance decreases. The high initial resistance of the thermistor allows for the high inrush current to be limited, and once the current flows through the thermistor, the resistance decreases to a negligible value, causing the voltage drop across it to be negligible as well. However, the main disadvantage is that thermistors have a relatively large thermal time constant, meaning that they take a long time to cool down. If the rectifier system is energized when the thermistor's resistance is low, the capacitor could still draw a high inrush current, damaging the circuit.

The other mitigation technique uses a current limiting resistor (CLR) or inductor (CLI) in series with the bridge-rectifier. This impedance will limit the current, protecting the system from the high inrush current, and then it would be shorted once the capacitor was charged, to avoid power losses.

Although this method provides a solution to mitigate inrush transient currents, these resistors and inductors have high power ratings and are large in size, occupying too much space ..."

Inrush Transient Current Mitigation

[Behemot]

Re: Power supply build quality pictorial. part 2

Do you think PFC coil can be used that way?

[TELVM]

Re: Power supply build quality pictorial. part 2

I haven't the foggiest, that's why I'm asking .

It intrigues me that even the worst gutless wonders I've seen always come with NTC thermistor.

Then the Antec people, after taking the trouble to lay a couple MOVs between the big caps to protect from surges, go cheap on the thermistor and leave this PSU unprotected against inrush current? Strange.

[Behemot]

Re: Power supply build quality pictorial. part 2

The thing is, the PSU can work just fine without that. It's not like high currents affect PSU (they can, but usually not). It's the other way arround. PSU is the very one generating current spikes usually only in the moment when you plug it into electricity and when you are turning it on.

The reason for current limiting is these spikes can switch off the breakers, especially if you have more computers. This can be problem in offices and so where more computers can start in the same moment.

[Th3_uN1Qu3]

Re: Power supply build quality pictorial. part 2

The thermistor isn't for protecting the PSU. Apart for the fuse, the rectifier bridge and the input caps (to a small extent), inrush current does not affect the PSU.

What it is for, is limiting damage to your power cords and outlets. When the PSU is plugged in with the switch already flipped to the "on" position (that is, if it has one, otherwise it's always "on"), the high current inrush that occurs when charging the primary capacitor can create a large spark on the pins of the power cord, damaging the cord and outlet in the long run. That's why the inrush current regulations exist, not for anything concerning the insides of the PSU.

Edit: Behemot above me was also spot on with the breakers.

[Behemot]

Re: Power supply build quality pictorial. part 2

Can it be so bad to affect cables? I would more bet on sparking when you un/plug cable too often.

[ben7]

Re: Power supply build quality pictorial. part 2

Can it be so bad to affect cables? I would more bet on sparking when you un/plug cable too often.

Cables take a lot of overcurrent to burn up.

If this PSU would trip your circuit breaker, then other things like a vacuum cleaner and stereo would too. Most circuit breakers take a little bit (few 1/6 a second) to respond.

Sparking would occur when plugging in, due to the sudden current draw, and not yet completed circuit (The prongs juuuuuust touching the contacts in the outlet, which could be dirty)

[Behemot]

Re: Power supply build quality pictorial. part 2

Well people sometimes go to breakers limits (oven, cooker, washing-machine and boiling kettle on top in the same moment). But as I said, it is more of a problem in offices when after power-drop all PCs can start in the same moment. And unfortunatelly even today you can find very crappy PSUs in this environment.

[ben7]

Re: Power supply build quality pictorial. part 2

Well people sometimes go to breakers limits (oven, cooker, washing-machine and boiling kettle on top in the same moment)

That happened in my school. Well, nothing exciting happened, but someone was using the refrigerator, microwave, and a tea kettle at the same time. The breakers DIDNT trip, but the outlet and power strip got extremely hot!

[TELVM]

Re: Power supply build quality pictorial. part 2

Thanks for the info gentlemen ! So until the switch welds closed, the power cord melts, or the circuit breakers trip, I shouldn't worry too much about 'TH1' being empty.

[tom66]

Re: Power supply build quality pictorial. part 2

An active PFC coil isn't effective against inrush current, it's less than 1mH in most cases. A passive PFC coil of a few hundred mH or more could have an effect.

[PeteS in CA]

Re: Power supply build quality pictorial. part 2

Inrush limiting thermistors are not expensive, but even $0.01 saved when you're making 10s oor 10ss of thousands of units adds up.

[Pentium4]

Re: Power supply build quality pictorial. part 2

Orion (HEC) Clearly can't do its labeled rating but doesn't look too bad once I add some input filtering to it. Has very nice heatsinks. Teapo primary and secondary, most of the little caps are Su'scon. 3.3V = 30A, 5V = 40A, 12V = 20A. Two 2N60L switchers. After adding input filtering and a recap, what do you think this thing would do continuous, stable?

It gets a steady 5.16V on the 5VSB but won't turn on, don't know what's wrong with it yet. It has two 80MM fans branded "Young Lin Tech"

And look at that....there's no -5V rail on the label but there's a white wire.....cut from the inside of the case! It was like that when I opened it and I was the one to break the warranty sticker.

[Behemot]

Re: Power supply build quality pictorial. part 2

Try changing the small cap on +5 V SB, may solve the problem.

[Pentium4]

Re: Power supply build quality pictorial. part 2

Try changing the small cap on +5 V SB, may solve the problem.

I replaced them and still no powering up. It gets the same voltage on the 5VSB, and 0V on all of them except the 5V gets 0.02V. Maybe I should check the input caps?

[Behemot]

Re: Power supply build quality pictorial. part 2

Well than maybe the +5 V SB is good and someting else got wrong actually. Isn't there any short on secondary? Maybe somebody wanted to load it according to the label and blown some rectifier?