Hi,

I'm new here and in the beginning of my career as an electrical engineer.

I'm using a schottky barrier rectifier on a circuit, and according to the datasheet its Average Rectified Output Current is 3A.

Is it OK if the consumer fed through that diode max consumption is 3.4A?

And if someone could expand about the meaning of Average Rectified Output Current, that would be great, because I'm not sure about it.

Thanks!

 

hi KS,
Welcome to AAC.
Check thru this PDF for that definition and other parameters.
E

 

hi KS,
Welcome to AAC.
Check thru this PDF for that definition and other parameters.
E

Hi,

Thank you for the reply!

I've read this but I'm still not sure about whether 3A is the max allowable value, or is it just the average.

 

hi KS,
OK.
I would say that the 3A rated diode is under rated for a continuous 3.4A usage, IMO a 5Amp rated diode would be preferred.
What is the application.?
E

 

hi KS,
OK.
I would say that the 3A rated diode is under rated for a continuous 3.4A usage, IMO a 5Amp rated diode would be preferred.
What is the application.?
E

Powering a PC.

Although 3.4A is the calculation I reached according to the PC's original power supply (19V 65W), so that would be the max current consumption possible.

Is there a common practice for those power supplies, such that I can assume that the real use would be only X% of the capability?

 

hi,
If I had to design a PSU for a client, who had specified that it should be capable of 19Vdc at 3.4Amps, I would never assume a X% down rating in performance.
It would be capable of at least +5% over rating.
You should consider the operating environment of the PSU and the consequence of an in service failure.

If your application is for one PC, why don't you measure the actual operating current.?
E

 

hi,
If I had to design a PSU for a client, who had specified that it should be capable of 19Vdc at 3.4Amps, I would never assume a X% down rating in performance.
It would be capable of at least +5% over rating.
You should consider the operating environment of the PSU and the consequence of an in service failure.

If you application is for one PC, why don't you measure the actual operating current.?
E

Thank you for your replies! It's highly appreciated.

I'll measure the actual consumption and decide accordingly.

 

hi KS,
As you are at the start of a hopefully long and successful career, one piece of advice would be to always fix your client down into providing a detailed written specification.
Usually 'verbal' and 'informal chat' specifications will cause the designer much grief.

Eric

 

When you measure current of PC it should be running some intensive calculation test
along with serious graphics rendering functions and hard disk activity and com activity
and USB loads and.....

In other words its complicated as to what the PC energy requirement is just assuming
sticking an ammeter in PSU lead will indicate.

A worst case would be to take manufacturers max numbers for each system level piece
and add. Hopefully the MB manufacturers numbers did this right for their portion. They
should have a power breakdown of how they did this and what was measured. Same
for graphics card guys.

Regards, Dana.

 

The current rating of a diode is, to a very large extent, a function of allowable temperature rise, which in turn is a function of power dissipation and rate of heat removal. The 3 ampere average rating will be at specified conditions.

It would be quite acceptable to put 10 ampere pulses through the diode provided that the temperature of the die was not excessive at the end of each of the pulses. You could, for example, put 10 A pulses of 100 µs width at 1% duty cycle through the 3 A diode, but you couldn't put 100 s pulses at 1% duty cycle through it. In both cases, the long-term average is only 100 mA. In the former case the pulse is narrow enough that the die is not going to reach the allowable temperature limit because the heat input is quite small. In the latter case, the pulse is so wide that the whole of the die and package will likely reach or at least nearly approach thermal equilibrium at an excessive temperature. This sort of thing is typically well documented in the datasheet.

The average current rating conditions in the datasheet may, in some cases, be unrealistic in terms of being able to accomplish the conditions in any practical system. For example, you may find some rating based on a particular mounting face temperature, but in order to actually accomplish such a temperature you would have to be removing heat using liquid cooling with extremely cold coolant at a high flow rate.

 

Hi,

Thank you for the reply!

I've read this but I'm still not sure about whether 3A is the max allowable value, or is it just the average.

Just out of curiosity - why are you using a SB rectifier?