Measuring switching frequency ?

[kaboom]

Re: Measuring switching frequency ?

Supposed to be on the cap

If you know anything about SMPSes, the switching freqb is measured on the LV output diodes' anode(s).

Autocorrect at its best again.

Then stop using it! Why people would rather waste energy "apologizing" for autocorrect versus gee, correcting something, is beyond me.

Oh yeah, the switching frequency will change as the load changes,

Again, you don't understand. The switching frequency doesn't change with load. Only the hunting/squealing of an poorly compensated SMPS changes w/ load. If you don't know what "compensation" is and how it can cause/effect low freq oscillation in an SMPS's output, shut up til you know what the hell you're talking about.

but 312hz is quite low for my liking. Time will tell.

Again, you fail to understand what's going on. The fact that you think something would actually switch at 300-anything Hz is in direct conflict with the "little" transformers SMPSes use.

Once again! 312Hz is NOT the switching frequency!

The unit is oscillating/hunting- increase the load (add damping to the output filter) and it'll change or go away. The switching freq will remain the same- isn't that part of why they're called switch mode power supplies?!

Get it right or go home.

[bianchi77]

Re: Measuring switching frequency ?

Got it measure the frequency as AC at the output of the transformer before it s rectified by diode set DMM to Hz and put negative to negative.. positive to that point..

[CapLeaker]

Re: Measuring switching frequency ?

Oh, grouchy... I apperrently know nothing. However you better re read what I meant. I didn't say that you measure the switching frequency at the capacitor. I suit he measues the ripple on the cap.
#2: you may not like me posting with my tablet, as autocorrect frigs up things in a while, but since you know everything, you should understand better. Not your problem what I use.
#3: I wasn't the one that said, 312hz is o.k. It should be way higher than that. Using a DMM to figure out the switching frequency is a bad idea anyhow. Use an oscilloscope for that.
#4: I don't like to be yelled at chief grouchy. I think you should relly read the thread before you do some WAG pointing fingers. I've got a pretty good track record in fixing PSUs.
Since you know things much better, go head. I am pissed off and out.

[jiroy]

Re: Measuring switching frequency ?

Well , i agree with Capleaker about the Oscilloscope thingy , DMM were never made to do accurate frequencies tests .

[keeney123]

Re: Measuring switching frequency ?

Got it measure the frequency as AC at the output of the transformer before it s rectified by diode set DMM to Hz and put negative to negative.. positive to that point..

And what did you measure for frequency? The data sheet in post 9 gives a good understanding of how the IC is working.

[keeney123]

Re: Measuring switching frequency ?

Kaboom some people are not book learners. They learn by doing. It is just a different form of learning.

[Marianelforum]

Re: Measuring switching frequency ?

There is an easier way to measure the freq of the supply by just measuring it at the outputs of the controller, for the 2003 one the outputs are at 7 and 8 pins, you just put the black lead of the multimeter at pin 12 ( Gnd ), and the red one at either 7 or 8 pin, each one delivers half of the wave for the power transformer's primary winding, so measuring just one of them tells you the frequency, you just need to make sure the DMM is well calibrated. Ofcourse if you got an osciloscope, you can view the outputs with it, and calculate the freq.

[softm]

Re: Measuring switching frequency ?

Switching freq of AT2005B is 50-60kHz, anybody who open datasheet can saw this at page 3.
Oscillation freq param.

If anybody want to verify this he will need use oscillocsope
to measure signal at gates/bases of mosfets/bipolar transistors of the power dcdc converter.

By what is need if datasheet have exact frequency.

[keeney123]

Re: Measuring switching frequency ?

Switching freq of AT2005B is 50-60kHz, anybody who open datasheet can saw this at page 3.
Oscillation freq param.

If anybody want to verify this he will need use oscillocsope
to measure signal at gates/bases of mosfets/bipolar transistors of the power dcdc converter.

By what is need if datasheet have exact frequency.

That is the oscillating frequency the switching frequency is the cross over point at 0 dB. The oscillating frequency is a sawtooth waveform that is referenced to the switching frequency.

[budm]

Re: Measuring switching frequency ?

Page 4 notes: 2) Operating frequency, for push-pull operation, Fpush-pull = 1/2 Tosc.
So look at the value of the Ct cap and then use the scope to look at the outputs to see what you have.

[Marianelforum]

Re: Measuring switching frequency ?

Switching freq of AT2005B is 50-60kHz, anybody who open datasheet can saw this at page 3.
Oscillation freq param.

If anybody want to verify this he will need use oscillocsope
to measure signal at gates/bases of mosfets/bipolar transistors of the power dcdc converter.

By what is need if datasheet have exact frequency.

Not that this topic speaks of AT2005B, but fyi, that is the freq for a given vallue a CT, you can see what it is in the same page. But that is not neccesarily the case with all the psu's, because not all of them have the same CT vallue.
You should pay closer attention

The oscilator freq is divided by the internal flip-flop controlling the outputs, so the output frequency is half of the oscilator. That is well known by anyone with basic knowledge of PWM supplyes.

But again, the topic speaks of the 2003 controller, NOT AT2005B, and as i sayd, the simplest way is to measure one of the outputs, and you get the switching freq of the power transformer.

[TechGeek]

Re: Measuring switching frequency ?

If you know anything about SMPSes, the switching freqb is measured on the LV output diodes' anode(s).


Then stop using it! Why people would rather waste energy "apologizing" for autocorrect versus gee, correcting something, is beyond me.





Again, you don't understand. The switching frequency doesn't change with load. Only the hunting/squealing of an poorly compensated SMPS changes w/ load. If you don't know what "compensation" is and how it can cause/effect low freq oscillation in an SMPS's output, shut up til you know what the hell you're talking about.



Again, you fail to understand what's going on. The fact that you think something would actually switch at 300-anything Hz is in direct conflict with the "little" transformers SMPSes use.

Once again! 312Hz is NOT the switching frequency!

The unit is oscillating/hunting- increase the load (add damping to the output filter) and it'll change or go away. The switching freq will remain the same- isn't that part of why they're called switch mode power supplies?!

Get it right or go home.

that escalated quickly